WO1998046976A2 - Method and apparatus for thermal radiation imaging - Google Patents

Abstract

A method and apparatus for thermal imaging is disclosed which enables a clinician to obtain visual images reflecting metabolic activity within a patient's body. A scanning system is configured to scan an area on the patient's body to obtain infrared intensity data. The data is digitized and processed prior to being displayed. The data processing includes a "slicing" function in which infrared intensity values are assigned color values in accordance with an output window. By redefining the mapping of the output window to the color spectrum, the data can be manipulated such that the visual display reflects metabolic activity within the patient's body under the scanning area.

Description

subside in the 1980's. In the last 10 years, it is believed that very little advancement has been

made in the field of thermography.

If only the temperature of the skin surface can be measured while the relationship

between the surface temperature and the emissions from the inside of the body cannot be

established, then application of thermal imaging technology is limited. It is believed,

therefore, that it would be desirable to provide a method and apparatus for revealing the

relationship between the skin's surface radiation temperature and internal thermal radiation

sources. Through image processing and measurement technology, surface or internal

radiation sources can be non-invasively distinguished through extrapolation. It is believed

that such technology would prove to be clinically effective in the detection and diagnosis of

cancers (especially in their early stages) and other diseases.

The temperature of a live human body is between 20°C and 40°C at room temperature

(20°C). Differences in skin color do not significantly affect the body temperature or the

emission of the thermal radiation. The wavelength of this thermal radiation is between 8 and

13 mm, which is often referred to as "infrared" region in the electromagnetic wave spectrum,

the infrared region having a longer wavelength than the red or near-red spectrum. The physics

of infrared radiation has been investigated extensively, and its application in thermal

metabolism imaging is relatively well-known to those of ordinary skill in the art.

There are various biochemical and biophysical mechanisms that can produce heat in a

live biological body. A biological body will absorb thermal energy if its temperature is below

that of the environment, or will emit thermal energy if its temperature is above that of the environment. The latter condition is the preferred mode of detecting and imaging thermal

metabolic activity.

Superficial (i.e., surface) thermal radiation from the skin of a biological body has

previously been studied. The present invention, on the other hand, involves the thermal

radiation associated with thermal conduction within the body.

There are multiple heat sources within a biological body. Although it is possible to

calculate the thermal radiation from a thermal body by thermodynamics, the complexity of

the boundary conditions associated with the biological body makes this approach impractical.

Therefore, a practically viable method that can be used to solve the problem of imaging

internal heat sources within a thermal body has not heretofore been shown. The present

invention involves formulation of a new method and apparatus for analysis of a thermal

system based on an analogy to electrical circuit theory; this method may be referred to herein

as a "thermal-electric analogue" method.

Infrared radiation passes through a transparent medium, air, for example, at the speed

of light. Thus, heat is transferred in air by thermal radiation. In a material body, on the other

hand, heat transfer is based on thermal conduction resulting in establishment of thermal

equilibrium. From the point of view of thermal radiation, infrared radiation deep within the

body cannot be readily detected from outside. Therefore, there has not heretofore been shown

a method and apparatus for resolving heat sources within the body; prior infrared imaging has

been restricted to viewing objects on the surface of the body. However, in accordance with

one aspect of the present invention, it is proposed that, based on the conduction of heat to

establish thermal equilibrium, thermal sources lying within the body can be imaged. That is, based upon the thermal conditions at the surface of a patient's body, information about

internal regions can be derived through extrapolation.

Thermal metabolism imaging systems used in clinical diagnosis are preferably not

influenced by particular patient conditions or environmental conditions. Prior art thermograph

machines have not been widely used because they generally do not satisfy this requirement.

Accordingly, it is another aspect of the present invention that an imaging system is provided

which is less sensitive disturbance from the patient and from the environment.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a thermal imaging system

particularly well-suited for medical diagnostic applications is provided. In one embodiment,

the system includes an infrared scanning system including an infrared sensor and associated

optics for scanning an anatomical area of interest, and generating electrical signals which

vary in intensity according to the intensity of thermal radiation at each point in the scanned

area. After digitization, the thermal energy signals are mapped to a color spectrum according

to the intensity of the thermal energy at each point in the scanned image.

In accordance with another aspect of the invention, the system includes a computer for

processing the thermal image data. One processing step is referred to as a thermal radiation

"slice" operation, which involves gradual adjustment of the mapping of thermal intensity data

to color values in a color spectrum. Displaying the thermal data during adjustment of the

color mapping reveals meaningful information about internal sources of thermal energy, facilitating the detection, identification, and/or assessment of certain metabolically significant

internal regions, including, for example, tumors and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects and features of the present invention may perhaps be

best appreciated with reference to a detailed description of a specific embodiment of the

invention, when read in conjunction with the accompanying drawings, wherein:

Figures la, lb, and lc are diagrams of a thermal system showing the distribution of

thermal radiation emanating from a point heat source and impinging upon a planar surface;

Figure 2 is a schematic diagram of an electrical circuit analogue to the thermal system

of Figure 1;

Figures 3a, 3b, and 3c are diagrams of a thermal system showing the distribution of

thermal radiation emanating from a uniform circular heat source and impinging upon a planar

surface;

Figures 4a, 4b, and 4c are diagrams of a thermal system showing the distribution of

thermal radiation emanating from a three-dimensional Gaussian distributed spherical heat

source and impinging upon a planar surface;

Figures 5a, 5b, and 5c are diagrams of a thermal system showing the distribution of

thermal radiation emanating from a three-dimensional Gaussian distributed spherical heat

source, radiating through an inhomogenious medium and impinging upon a planar surface;

Figure 6 is a block diagram illustrating a thermal imaging system in accordance with a

specific embodiment of the present invention; Figure 7 is a schematic/block diagram of a portion of the system from Figure 6

including scanner, filter, and analog-to-digital converter subsystems;

Figure 8 is a schematic/block diagram of the scanner subsystem from the system of

Figure 6;

₅ Figures 9a and 9b are graphs of the output response of the scanner subsystem from

Figure 8;

Figure 10 is a flow diagram illustrating operation of the thermal imaging system of

Figure 6;

Figure 11 is a schematic/block diagram of the scanner subsystem in the imaging

l o system of Figure 6;

Figure 12 is an alternative schematic/block diagram of the scanner subsystem in the

imaging system of Figure 6;

Figure 13 is a plot of an image pulse wave and a line pulse signal present in the

scanning subsystem of Figures 11 and 12;

is Figure 14 is a functional flow diagram illustrating operation of control software for

the imaging system of Figure 6;

Figure 15 is a diagram illustrating color mapping of thermal intensity data generated

by the imaging system of Figure 6;

Figure 16 is a color image of a display screen from the imaging system of Figure 6

20 during a scanning proceedure;

Figure 17 is a diagram illustrating color mapping of thermal data before and after

computer processing in the imaging system of Figure 6; Figure 18 is a diagram illustrating a thermal radiation slice operation performed by the

imaging system of Figure 6 on thermal intensity data; and

Figure 19 is a diagram illustrating the visual display resulting from performing the

thermal radiation slice operation of Figure 18 on thermal intensity data associated with a

suspected anatomical region.

DETAILED DESCRIPTION OF A SPECIFIC EMBODIMENT OF THE INVENTION

As noted above, metabolic activity causes multiple heat sources to exist in a live

biological body. Figure la illustrates a simple case, in which a point heat source designated

S₀ is embedded within a homogeneous medium Ml, the medium Ml being further

surrounded by atmosphere M2. A planar interface between medium Ml and medium M2 is

identified with reference numeral 10 in Figure la. Interface 10 extends along an axis

designated "x" in Figure la.

The temperature of S₀, Ml and M2 are Tl, T2, and T3, respectively. When Tl is

greater than T2, which in turn is greater than T3, the heat transfer from S₀ is shown by

conduction lines 12 in Figure la. As shown in Figure la, point heat source S₀ is disposed at a

perpendicular distance D from interface 10. The angle of each conduction line 12 from this

perpendicular is designated as α in Figure la. For α not equal to zero, a conduction line

intersects interface 10 at some distance x=H or x=-H from the origin (x=0), with H in the

range of -n to n.

Figure lb shows the distribution function H(x,y) of the thermal energy radiated from

point heat source S₀ on planar interface 10, in steady state under thermal equilibrium. H(x,y) is symmetric if the medium Ml is homogenous and the point source S₀ is isotropic. The

pattern of H(x,y) will thus depend upon the thermal properties of medium Ml including its

specific heat and heat conductivity, as well as the distance between S₀ and M2, i.e., the

thickness of Ml . Figure lc shows the distribution of H(x) on the x-axis.

To describe the heat conduction from the heat source S₀ and the thermal radiation

function H(x,y), and in accordance with one aspect of the present invention, a

thermal/electrical analogy can be made to relate the thermal system to its analog electric

system. The correspondence between quantities in thermal and electrical systems are listed in

the following Table 1 :

Table 1

With reference to Figure la, in medium Ml heat conduction can be thought of as

many conduction lines 12 very close to each other. If it is assumed that the temperature

difference and distance between S₀ and M2 is not large, then any given small section of

conduction lines 12 itself does not represent a heat source. Under these assumptions, one of

the conduction lines 12 in the thermal system in Figure la can be analogized to the electrical

circuit shown in Figure 2. In Figure 2, a battery designated U_H1 is analogous to the heat source S₀. A battery

designated UH3 represents the heat source of air (medium M2 from Figure la). Resistance

RHl in Figure 2 is the internal resistance of UHl, which accounts for the internal heat loss

inside the heat source. Similarly, resistance RH3 corresponds to the heat resistance of the air.

Resistances RH₂₁ through RH_2K correspond to the heat resistance of the medium Ml,

specifying the heat loss per unit length of a conduction line 12 within Ml. CH₂₁ through to

CH_2K represent the heat capacity of the medium Ml, specifying the heat reserve per unit

length of a conduction line within Ml . Using the circuit of Figure 2, conventional circuit

analysis can be applied, assuming the circuit is under steady state, to obtain an expression for

the transfer function H(x) as follows:

Σ*. H2ι

H(x) = ∑ U (=1

HI χ {u_H] -u_H3)

^RHl ^{+ R}H3 + Σ H2ι ι=l *.

where

α being the angle of incidence of a given conduction line 12 with plane 10, as noted

above with reference to Figure la, and d being given by the equation

where D is the distance along the x axis between point heat source S₀ to interface 10

and R_Q is the heat resistance rate of homogenous medium Ml . Thus, along the x axis, the relative radiation distribution is as shown in Figure 1 c, and

on the plane A we get a circular radiation distribution with diameter 2H, as shown in Figure

lb, which is highest in the center and gradually decreases as |x| increases.

For an interface 10 having transverse thermal conduction is 3 to 5 times lower than

internal conduction within medium Ml, when α=45° then H=D and hence D/r = 0.707. This

is referred to as the "half power point."

In an unsteady state, the thermal radiation as a function of time can be used to study

the heat transfer and equilibrium establishment in the medium, such as when additional cold

or heat sources are introduced near the medium, or when the metabolism is changing, for

example, during exercise.

When multiple heat sources exist within a medium, the distribution of H(x,y) can be

calculated as the superposition of the H(x,y) from multiple single point sources. If the

medium Ml is not homogeneous, the inhomogeneity can be simplified to calculate H(x,y) on

the plane A. The following examples show a few typical cases of thermal distributions

H(x,y). In each of these examples, the designation conventions adopted in Figures la-lc are

used; that is, conduction lines are designated with reference numeral 12, the angles of

conduction lines 12 with respect to the perpendicular distance between point heat source S₀

and plane 10 are designated as α, and so on.

Figure 3 a shows a heat source S₀' having a circular, planar configuration. The thermal

energy distribution H(x,y) on plane 10 is again symmetric and circular, as shown in Figure

3b. As shown in Figure 3c, H(x) along the x axis on plane 10 has a trapezoidal distribution.

The relative width of the sides of the trapezoid decreases when source S₀' is farther away from plane 10. As the distance between the source S₀' and plane A increases, the source

distribution approaches that of a point source, as previously discussed with reference to

Figures la-lc.

Figure 4a shows a non-uniform, three-dimensional Gaussian distributed spherical heat

source S₀". Again, the thermal distribution function H(x,y) shown in figure 4b is substantially

circular. However, as shown in Figure 4c, the energy on the x-axis is has a Gaussian

distribution. Again, the distribution approaches that of a point source (Figures la-lc) as the

distance D between the source and plane 10 increases.

In the foregoing examples, it has been assumed that Ml was a homogenous medium.

Figures 5a-5c illustrate an example of a non-uniform, three-dimensional Gaussian distributed

spherical heat source S₀'" within an inhomogeneous medium. The inhomogeneity is

represented by a inhomogenous region designated M3 in Figure 5a. As shown in Figures 5b

and 5 c, the inhomogeneity of the medium introduces perterbations in the thermal transfer

distribution functions H(x,y) and H(x) as compared with those functions corresponding to the

same spherical heat source in a homogenous medium, previously discussed with reference to

Figures 4b and 4c.

The examples of Figures la-lc, 3a-3c, 4a-4c and 5a-5c serve to illustrate the theory

underlying the present invention. In accordance with one aspect of the present invention, a

thermal radiation image of one part of human body is obtained, and information about

internal metabolic activity is detected, derived and/or extrapolated based upon the

fundamental principles of thermal conduction illustrated in the foregoing examples. That is,

the skin surface plays the role of planar interface 10 in the foregoing examples, such that thermal radiation patterns at the skin surface can be used to extrapolate information about

underlying internal metabolic activity, which constitutes the heat source S₀ in the examples.

Internal heat sources at different depths and having different shapes are reflected in

different surface patterns in the image. From the above analyses, it is believed that the the

thermal radiation pattern at the skin surface can be detected, observed and measured, and used

to calculate the center point temperature U₀. Image processing technology can then be

applied to determine the half power point (i.e., 0.707U_o), the distance between the half power

point and the skin surface being the depth D of the source.

For different parts of a human body, the heat resistance rate (thermal conductivity) is

different. For example, for fatty tissue (adipose), the heat resistance rate R is on the order of

0.1 to 0.15 °C/cm. For muscle R is on the order of 0.2 °C/cm, and for bone, R is generally in

the range 0.3 to 0.6 °C/cm.

Thus, in accordance with one aspect of the present invention, the temperature of intra-

body (i.e., internal) heat sources can be non-invasively ascertained. The difference between

this temperature and normal metabolic thermal radiation temperature is the very useful data,

and it can be used to detect and/or diagnose the nature and characteristics of lesions or

pathology within the body.

The following Table 2 lists the heat production of various cells relative to normal

cells. From the heat generated from a group of cells, the physiological properties of the cells

can be analyzed and the pathological features of the tissues can be diagnosed.

Table 2

To reduce the influence of the measurement distance from the patient to the scanner,

in addition to multiple levels of filtering, a detector sensitive only to radiation wave length

rather than to radiation intensity is preferable.

Among all the factors affecting the thermal radiation from the patient, the most

important factor is the patient. The thermal radiation could be affected by the patient's mental

status, psychological or physiological conditions, or other environmental disturbance. The

normal basal body temperature among different patients can also differ significantly, i.e., by

more than 6 degrees or so. In the prior art, the normal basal temperature of the human body or

a particular anatomic region was averaged from the human population to be used as a

diagnostic standard. This can result in large errors in diagnostic specificity because of the

thermal differences existing among different people.

It has been proposed to use the temperature differences of the corresponding anatomic

regions as a diagnostic standard. This can lead to somewhat improved diagnostic specificity,

but it still may not satisfy the clinical requirement. In accordance with one aspect of the

present invention, therefore, it is proposed to use the normal metabolic thermal radiation

temperature of the a patient himself/herself within the same body region as the reference

temperature value. Clinical trials have shown great improvement of the diagnostic specificity.

The method and apparatus of the present invention avoids the errors due to: (1) the difference

in basal normal temperature among the population; (2) the disturbance from the patient

himself/herself; and (3) disturbances from the environment. In principle, the metabolic regions from which the normal basal temperature of the

patient is obtained include head, extremity, chest, abdominal, dorsal regions, and other large

and uniform areas on the body. The selection of the normal regions should avoid inclusion of

the diseased, adipose, or bony areas.

Figure 6 is a block diagram of a thermal imaging system 50 in accordance with one

embodiment of the present invention. Central to the system 50 is a computer 52, which in the

presently preferred embodiment of the invention is an industry-standard personal computer

system including a microprocessor, such as the commercially-available Intel Pentium™

processor or the like, operating under control of, for example, the Windows 95™ operating

system. Those of ordinary skill in the art, however, will appreciate that various other types of

computers now available or to become available may be equally or even more suitable for the

purposes of practicing the present invention. For the purposes of the present disclosure, it will

be assumed that computer 52 is a system which includes such conventional and well-known

components as a hard disk drive, keyboard, mouse or other cursor control device, and so on.

In use, a patient upon whom thermographic imaging in accordance with the method

and apparatus of the present invention is to be performed is positioned on a scanning bed 54,

within the scanning field of a scanner 56 carried by a scanning gantry 58. The scanner 56 of

the presently disclosed embodiment will be hereinafter described in further detail. As would

be appreciated by those of ordinary skill in the art, scanner 56 functions in a conventional

manner to generate electrical signals corresponding to the intensity and wavelengths of

electromagnetic radiation present in its scanning field. Various scanning systems have been

shown in the art, and although the present disclosure will describe one or more scanners in detail, it is believed that the particular details of the implementation of the scanning system

employed to obtain infrared data is not critical to an understanding of the principles

underlying the present invention, and it is further believed that those of ordinary skill in the

art having the benefit of the present disclosure would be readily able to adapt the teachings of

the present disclosure to the purposes of practicing the present invention.

The electrical signals from scanner 56 are provided as input to an analog-to-digital

(A/D) converter and filtering circuit 60, which performs a filtering and digitization function

on the scanner's output. The digitized scanning signals are then available for processing by

computer system 52. The resulting processed images may then be displayed on display 62,

which may be a high-resolution video monitor or the like. The processed images may also be

output to a printer 64.

The remaining components of thermographic imaging system 50 are more or less

conventional in design and operation. For example, an AC power supply 66 is used to provide

power to various components of system 50. A DC power supply 68 converts AC power from

AC power supply 66 to DC, providing the necessary operational power for an operator

console 70. Console 70 is the means by which an operator of system 50 controls the

activation, movement and positioning of scanning bed 54, scanning gantry 58 and scanner 56.

For example, a "Turn" signal from operator console 70 is provided on line 72 to cause

scanning bed 54 to turn. Similarly a "Move" signal on line 74 controls lateral movement of

scanning bed 54. A "Scan" signal on line 76 is provided to scanner 56 for controlling

activation and deactivation of scanner 56. An "Up/Down" signal provided to scanning gantry

58 controls up and down positioning of gantry 58 and scanner 56. Figure 7 is a slightly more detailed block diagram of a portion of infrared

scanning/imaging system 50 in accordance with the presently disclosed embodiment of the

invention, including filter and A/D converter circuit 60, computer system 52, and scanner 56.

As will be hereinafter described in further detail (in particular, with reference to Figures 11

and 12), scanner 56 includes an infrared detector 98 and various optics and focusing systems

to scan an image field and generate electrical signals representing a matrix of thermal energy

intensity values (256x256 values, in the presently disclosed embodiment, although those of

ordinary skill in the art will appreciate that greater or lesser resolution may be implemented).

The output from scanner 56 is first applied to a low-pass filter circuit comprising a

resistor 80 (a 100Ω resistor in the presently preferred embodiment) and a capacitor 82 (a

0.01 μF capacitor in the presently preferred embodiment). This low-pass filtering reduces the

electronic disturbance or noise from other equipment which might be present in the clinical

environment in which system 50 is used. In the presently disclosed embodiment, the filter

comprising resistor 80 and capacitor 82 attenuates signals over 100 kHz by 40dB or so.

With continued reference to Figure 7, the filtered output from infrared detector 98 is

applied to a preamplifier, as would be familiar to those of ordinary skill in the art, and then

applied to the input of A/D converter 86. In the presently disclosed embodiment, A/D

converter 86 operates at 100 kHZ with 12-bit resolution. The digitized sensor signal is then

provided as input to computer 52 for digital processing in accordance with one aspect of the

present invention.

Turning now to Figure 8, there is shown a schematic/block diagram of a portion of the

thermal imaging system 50 in accordance with the presently disclosed embodiment of the invention, illustrating, in particular, certain details of scanner 56. In Figure 8, the target being

thermally scanned and imaged, i.e., an area of the patient's anatomy, is represented with

reference numeral 88. Thermal (i.e., infrared) radiation from target 88 is represented with

dashed lines 90 in Figure 8. In accordance with one aspect of the present invention, in order

to reduce the influence of the measurement distance between target 88 and scanner 56,

multiple levels of radiation filtering are employed. Additionally, scanner 56 is preferably

sensitive only to radiation wavelength, and not to radiation intensity.

As shown in Figure 8, the thermal radiation 90 first passes through a Germanium

monocrystal filter, designated with reference numeral 92. Germanium monocrystal filter 92,

as will be appreciated by those of ordinary skill in the art, has a transmission fraction of

approximately 90% to radiation having a wavelength of between 8 and 13 μm (typically

referred to as "infrared" radiation), and a transmission fraction of less than 0.1% to visible

light.

Scanner 56 further includes a Germanium coated lens 94 having transmission

characteristics substantially the same as discussed above with reference to Germanium

monocrystal as well as a further Germanium monocrystal filter 96.

The three levels of Germanium filtration just described preferably result in a

transmission fraction of less than 0.1%o for radiation beyond 8 to 13 μm, and less than 0.001%

to visible light for the radiation actually impinging upon the wavelength sensitive detector

designated with reference numeral 98 in Figure 8. This reduces the system's overall

sensitivity to environmental light. Wavelength sensitive detector 98 in the presently disclosed embodiment of the

invention is made of Cd-Hg-Te material. Various infrared detectors suitable for the purposes

of practicing the present invention are known in the art and are commercially available. U.S.

Patent No. 5,034,794 to Murotani, entitled "Infrared Imaging Device" is but one example.

Figures 9a and 9b illustrate the output response for sensor 98 in accordance with the presently

disclosed embodiment of the invention. In particular, Figure 9a shows the output voltage of

sensor 98 as a function of wavelength, and it can be seen from Figure 9a that the output

response is greatest in the wavelength range of 8 to 13 μm. Figure 9b shows the output

voltage of sensor 98 as a function of the distance between sensor 98 and target 88. It is

apparent from Figure 9b that the output response as a function of distance is relatively flat,

rendering system 50 relatively insensitive to variations in distance between scanner 56 and

target 88.

In the presently disclosed embodiment of the invention, wavelength sensitive detector

98 preferably enables the scanner to detect temperatures in the range from 0 to 50°C, with an

accuracy of 0.05°C. In the presently implemented embodiment, a scan takes approximately

five seconds, resulting in a 256x256x8 bit (64kByte) image.

Although the present invention is described herein as incorporating a "single-point"

infrared sensor, i.e., a sensor which is capable of detecting infrared radiation at a single point

within the overall scanning area, it is contemplated that other infrared scanning devices,

currently known or to be developed, may be advantageously employed in the practice of the

present invention. For example, linear or two dimensional (e.g., grid) arrays of multiple

individual sensors are known, and it is believed that those of ordinary skill in the art having the benefit of the present disclosure would be able to readily adapt the presently disclosed

embodiment of the invention to incorporate such different types of sensors for the purposes of

practicing the present invention. A potential advantage of using a linear or two-dimensional

arrays of sensors would be a reduction in the time necessary to scan a given image area. It is

to be understood, therefore, that the present invention is in no way limited to systems

incorporating a single-point sensor.

Figure 10 is a flow chart illustrating operation of system 50 in accordance with the

presently disclosed embodiment of the invention. The first step of system operation,

positioning the patient with respect to the scanner, is represented by block 100 in Figure 10.

To facilitate this, system 50 provides for movement of both scanning bed 54 and scanning

gantry 58 carrying scanner 56, as previously described. In the presently disclosed

embodiment of the invention, scanning gantry 58 is preferably capable of moving from

between 0.4 to 1.6 meters from scanning bed 54. Moreover, gantry 58 is preferably capable of

rotating ± 45° left and right, and ± 30° up and down. All such positioning of gantry 58 is

faciliated by the operator console 70, previously discussed reference to Figure 6.

Similarly, scanning bed 54 is preferably capable of positional adjustment with respect

to gantry 58. In the presently disclosed embodiment, scanning bed 54 is preferably capable of

from between 0.3 and 5.0 meters from scanning gantry 58, and of turning 360° with respect to

gantry 58.

With continued reference to Figure 10, the next step in the operation of system 50 is

to ensure that thermal equilibrium has been established; this is represented by block 102 in

Figure 10. Because of the specific heat of the human body, thermal conduction and establishment of thermal equilibrium in the human body can be a slow process. Thus, it may

require up to 10 to 15 minutes prior to an examination to achieve a thermal equilibrium

condition. On the other hand, the dynamic thermal process can be used to study and measure

the specific heat of the human bodies, as well as to assess pathological or other body

reactions.

The next step in the operation of system 50 is to initiate the scanning operation, as

represented by block 104 in Figure 10. During this operation, thermal radation from the

scanned area of the patient is received by scanner 56 and transformed into analog electrical

signals, as previously discussed.

These analog signals are filtered, preamplified, and applied to the input of A/D

converter 86, as also previously discussed, and as represented by block 106 in Figure 10. The

digitized signals are then provided to computer 52 for processing, as represented by block

108 in Figure 10. The digitized signals received by computer 52 represent a two-dimensional

color image reflecting skin surface temperature of the scanned area. Processing by computer

52, applying the concepts of extrapolation discussed with reference to the examples of

Figures la, lb, lc, 3a, 3b, 3c, 4a, 4b, 4c, 5a, 5b, and 5c is necessary to derive a two-

dimensional image representing the metabolic activity within the patient's body at the

scanned area.

Finally, as represented by block 110 in Figure 10, the resulting processed image,

representing an extrapolation of the surface thermal image to represent internal metabolic

activity, can be displayed, printed, and/or stored by thermal imaging system 50. It is contemplated that system 50 may be capable of various image processing and

diagnostic functions, as would be appreciated by those of ordinary skill in the art, including,

but not limited to: providing a heat source enhance function, whereby 256 colors can be used

to represent temperature differentials of anywhere from 0.01 to 0.1 °C; measurement of heat

radiation at multiple points on the patient; computing the maximum, minimum, and/or mean

temperature within a scanning area; displaying distribution curves of heat radiation in any

horizontal or vertical direction; multiple image comparison; and generation of three-

dimensional images.

Turning now to Figures 1 1 and 12, there are provided alternative schematic/block

representations of the scanning system 56 in accordance with the presently disclosed

embodiment of invention. It is to be understood that Figures 1 1 and 12 are intended to

represent the same scanning system 56; system 56 is merely represented in Figures 1 1 and 12

from different perspectives and with different levels and styles of schematic detail.

Accordingly, identical reference numerals are used in Figures 1 1 and 12 to represent the same

components.

Scanning system 56 as represented in Figures 1 1 and 12 operates as follows: Thermal

radiation from patient 120, represented by ray traces 90 in Figures 1 1 and 12 (as it was in

Figure 8), passes through front optics 124, which includes germanium monocrystal 92,

germanium filter 94 and germanium lens 96, previously described with reference to Figure 8.

Next, thermal radiation 90 impinges upon a vertical optics system 126, an oscillating

reflective system responsible for effectuating scanning in the vertical direction. Vertical

optics system 126 is controlled by a vertical motion control circuit 128. Thermal radiation 90 is then reflected to impinge upon a horizontal or line optics

system 130, also an oscillating reflective system responsible for effectuating scanning in the

horizontal direction. Line optics system 130 is controlled by a line motion control circuit 132.

From line optics system 130, the thermal radiation is reflected to a focusing optics

system 134 which is controlled by a focus adjustment circuit 136. Focusing optics system 134

operates to focus the thermal radiation 90 upon a modulator 136. Under control of a

modulation circuit 138, the vibrations of modulator 136 are used to control the optimal linear

sampling of scanner mirror 130 during the scanning to ensure that the distortion of images are

minimized. Moreover, the thermal radiation will be shielded during the back scanning period

of the scanner mirror 130.

The output of modulator 136 is applied to a sensitive infrared sensor 138, which in the

presently disclosed embodiment of the invention is a point type sensor although it is to be

understood that other commercially-available infrared sensors may be suitable for the

purposes of practicing the present invention. In particular, as noted above, it is contemplated

that linear or two-dimensional arrays of multiple sensors can be employed.

As previously noted with reference to Figures 6 and 7, the output of sensor 138 is fed

to an amplifier and analog-to-digital converter (ADC) circuit 60, which as shown in Figure 7

comprises resistor 80, capacitor 82, amplifier 84 and ADC 86.

Referring to Figure 11, vertical motion control circuit 128 and line (horizontal)

motion control circuit 132 generate signals for synchronizing the horizontal and vertical

scanning of scanner 56, in a conventional way. Vertical motion control circuit 128 generates a

signal "frame synch pulse wave" on a line designated with reference numeral 140 and line motion control circuit 132 generates a signal "line synch pulse wave" on a line designated

with reference numeral 142 in Figure 11.

The frame synch pulse wave and line synch pulse wave signals are depicted in Figure

13. In the presently disclosed embodiment of the invention, the image synch pulse wave

signal, designated generally with reference numeral 144 in Figure 13, is a periodic wave of

pulses of 0.4 mSec duration occurring every 4.8 sec, while the line synch pulse wave signal is

a series of 256 pulses of 0.4 mSec duration pulses occurring every 15.4 mSec, followed by a

0.85 sec "backsweep" interval prior to a subsequent series of 256 pulses.

Image scanning occurs as follows: when a scan is initiated, a frame synch pulse and

the first of 256 line synch pulses is generated. One frame consists of 256 horizontal scan

lines. One line is scanned for every line synch pulse in line synch pulse wave 146. After 256

lines have been scanned, the 0.85 sec back sweep time occurs, enabling the vertical motion

control circut to redirect the scanner to the top of the image, whereupon another frame synch

pulse occurs signalling the start of another image scan.

It is to be understood that the particulars of the scanning arrangement described

above, and of the nature of the frame synch pulse wave 144 and line synch pulse wave 146

may be varied from implementation to implementation. For example, if a different type of

sensor (e.g., a linear or two-dimensional array) were used in a given implementation, the

timing of horizontal and/or vertical scanning may be correspondingly different. It is believed

that those of ordinary skill in the art having the benefit of the present disclosure would be

readily able to adapt the present disclosure in accordance with such design and

implementation variations. The image pulse wave and line pulse waves signals are also provided to ADC 86 in

order to enable ADC 86 to synchronously convert the analog output from scanner 56 to

digital values.

The digitized output from ADC 86 is then provided to computer 52 for processing in

accordance with the present invention. Figure 14 is a functional flow diagram illustrating the

processing operations.

Block 150 in Figure 14 represents the analog-to-digital conversion operation

performed by ADC 86. The digital output of ADC 86 is then processed for intensity

adjustment and geometric compensation, as represented by block 152 in Figure 154. Intensity

adjustment refers essentially to the normalization of the digital data, to compensate for the

variance in base levels of intensity thermal radiation from patient to patient. That is, each

patient will radiate thermal energy over a range or spectrum of intensities whose upper and

lower limits will likely be different than other patients. Intensity adjustment normalizes each

patient's thermal energy spectrum to a common range. (It is to be understood that, at least for

the purposes of the present disclosure, "thermal energy" and "temperature" are not precisely

the same thing, although sometimes "temperature" is used herein as a shorthand reference to

"thermal energy." In particular, after the intensity adjustment step of block 152, a given

"thermal energy" level, when quantified, may not correspond to the same "temperature"

(measured, for example, in degrees centigrade), for two different patients. In any event,

"thermal energy" will be reflected by the intensity of thermal or infrared radiation, which is

fundamentally what the present invention concerns.) With continued reference to Figure 14, the geometric compensation processing

performed in block 152 refers to spatial processing of the digitized thermal data to

compensate for the essentially sinusoidal modulation of the scanned data arising from the

oscillatory nature of the horizontal and vertical optics systems 126 and 130. It is believed that

those of ordinary skill in the art will appreciate that, as optics systems 126 and 130 oscillate

back and forth to accomplish the scanning of a scanning area, the effective geometric

relationship between scanned points may be modulated in, for example, a sinusoidal or

pseudo-sinusoidal manner, and that a compensatory manipulation of the data may be

necessary to establish the true geometric relationship between adjacent scanned points in the

scanning area.

After processing in block 152, the processed data is then subjected to color mapping,

in block 154. In the presently disclosed embodiment of the invention, color mapping refers to

the assignment or mapping of color values to each thermal intensity increment within the

overall thermal intensity spectrum of the scanned area. This color mapping or coding

operation in accordance with the presently disclosed embodiment of the invention can

perhaps be best understood with reference to Figure 15. For the purposes of Figure 15, it is

assumed that the range or spectrum of thermal intensity values in the scanned area, after

intensity adjustment in block 152 (referred to herein as the "input window"), referred to with

reference number 155 in Figure 15, ranges between 13.90 and 39.50 (again, units for these

values are more or less arbitrary, and do not necessarily correspond with "temperature" in

degrees centrigrade). (As a matter of nomenclature, the maximum radiation intensity value in

the input window will be referred to as IW_MA and the minimum radiation intensity level in the input window will be referred to as IW_MIN. In Figure 15, IW_MAX is 39.50 and IW_MIN

isl3.909.)

Figure 15 shows a color spectrum 156 which ranges from white (at the top, in Figure

15) to black (at the bottom), with red, orange, yellow, green, blue, indigo, and violet regions

in between. For the purposes of Figure 15, it is to be understood that each of the color regions

(red, orange, yellow, etc..) is not a single color, but rather a range of colors, such that there is

no distinct division between any two regions (as the black-and-white representation in Figure

15 might otherwise suggest). That is, spectrum 156 is a conventional color spectrum which

gradually transitions along the colors of the spectrum of visible colors. Numerically,

however, the entire spectrum 156 can be represented by a range of discrete color values, for

example, 256 color values ranging from 0 to 255.

As shown in Figure 15, one distinctive region or color value of spectrum 156 (white

in the disclosed embodiment), is preferably reserved for assignment to the highest intensity in

the input window 155, IW_MAX=39.50 in the present example. Successively lower increments

of the input window are assigned to correspondingly successively lower locations in the red

region, then the orange region, the yellow region, etc., with the lowest increment of the input

window, IW_MIN= 13.90 in the present example, being assigned or mapped to the bottom of

color spectrum 156. In other words, the process of "mapping" input window 155 to spectrum

156 involves mapping IW_MAX to the highest color value in spectrum 156, mapping IW_MIN to

the lowest color value in spectrum 156, and mapping input window values between IW_MAX

and IW_MIN evenly to the color spectrum values between the highest and lowest. In the presently disclosed embodiment of the invention, spectrum 156 is divided into

256 distinct color values 0-255, such that, for example, the highest intensity value IW_MAX is

assigned color value 255 and the lowest intensity value IW_M1N is assigned color value 0.

Those of ordinary skill in the art will appreciate, therefore, that depending upon the

magnitude of the thermal intensity input window 155, some intensity values may be assigned

to the same color value (if the number of increments of intensity in the input window 155

exceeds 256) or, conversely, some color values may not have intensity values assigned to

them (if the number of increments of intensity in the input window 155 is less than 256). In

the illustrative example of Figure 15, however, the number of increments in the input window

155 is advantageously selected to be 256, such that there is a one-to-one correspondence

between the number of intensity increments and the number of color values in spectrum 156.

This is, however, not believed to be essential for the purposes of practicing the present

invention.

(Some more or less arbitrary assumptions are made for the purposes of the illustrative

embodiment of Figure 15 which are not critical for the purposes of the present invention. For

example, it is assumed in Figure 15 that the input window of thermal intensity values is

divided into increments of tenths of a unit; also, the order of succession of colors in spectrum

156 is also more or less arbitrary. It is to be understood that such assumptions can be varied

for the purposes of practicing the present invention. For example, it may be desired to

increase or decrease the size of successive increments in the thermal intensity input window

155 (e.g., to halves of units, or hundreths of units), and/or to re-order the color regions of

spectrum 156. It is contemplated that the sizing or increments in the thermal intensity input window may be controllable on a dynamic basis by the user of the system. That is, it is

contemplated that the control software for the system may include options for adjusting the

sizing or increment (resolution) of the input window.

After color mapping of the thermal intensity input window 155 to spectrum 156, the

thermal data may at this stage be displayed in accordance with such mapping; that is, the

mapping of window 155 to spectrum 156 determines what color value will be assigned to

each data value in the thermal data. This displaying is represented by block 157 in Figure 14,

and such display enables the clinician to view a thermographic image of the scanned area. An

example of such a thermographic image as it might appear on display 62 (see Figure 6) is

designated with reference numeral 158 in the color image of Figure 16. Such a thermographic

158 image is believed to differ from conventional thermographic images in several respects,

as a result, for example, of the filtering and modulating of the thermal radiation as it is

scanned and of the intensity adjustment processing discussed above.

However, in accordance with an important aspect of the present invention, additional

processing of thermal intensity input data is performed to achieve an even further enhanced

diagnostic functionality.

As represented by block 160 in Figure 14, the color-coded thermal intensity input data

from processing block 154 is next subjected, in accordance with one aspect of the present

invention, to what is referred to herein as a thermal radiation "slice process."

The first stage of the slice process involves defining an output intensity window

comprising a range of intensity values preferably smaller than the range of intensity values in

the input intensity window 155. Then, each increment in the output intensity window is mapped to a color value in color spectrum 156. Figure 17 illustrates this process. In the

illustrative embodiment of the invention, a scaling factor of Vi is used to define the output

intensity window, which is designated with reference numeral 162 in Figure 17. That is,

whereas the input intensity window 155 has a range of 25.60 intensity increments (that is,

IW_MAX - IW_MIN = 25.60), the output intensity window is selected to have one-half of that

range, or 12.80 intensity increments (35.00 - 22.20 = 12.80). (Again, as a matter of

nomenclature, the range of the output window will be deemed to range between a maximum

value OW_MAX and a minimum value OW_MIN.)

Stated more mathematically, the process of defining output intensity window 162

involves selecting OW_MAX and OW_MIN such that OW_MIN > IW_MIN, OW_MAX < IW_MAX and

(OW_MAX - OW_MIN) < (IW_MAX - IW_MIN). For a scaling factor of Vi, (OW_MAX - OW_MIN) =

^(I MAX - I MIN)-

It is to be understood that the scaling factor for defining the output intensity window

may be selected to be greater or less than ! ₂, which is used in Figure 17 merely as an

illustrative example. In the preferred embodiment, in fact, the scaling factor for defining the

output intensity window is among the operational processing parameters which can be

adjusted up or down on a dynamic basis, as will be hereinafter described in further detail.

Having selected the output intensity scaling factor, the output intensity window 162

can then be mapped to spectrum 156, as depicted in Figure 17. In Figure 17, the 12.80

increment range of output intensity window 162 ranges between intensity values OW_MAX =

35.00 and OW_MIN = 22.20. However, in accordance with one aspect of the present invention,

since output intensity window 162 is smaller than input intensity window 155, it is possible for output intensity window 162 to fall in any 12.80 increment range of the 25.60 increment

range of the input intensity window 155. That is, it is possible to "slide" or adjust the output

intensity window 162 up and down within the input intensity window 155.

The sliding adjustment of output intensity window 162 illustrated in Figure 18, which

shows output intensity window 162 as it is adjusted from a first position (162') in which it is

mapped to an intensity range between OW_MIN' = 26.70 and OW_MA ' = 39.50 to a second

position (162") in which it mapped an intermediate intensity range between OW_MIN" = 22.20

and OW_MAX" = 35.00, to a third position (162"') in which it is mapped to an intensity range

between OW_M1N'" = 13.90 and OW_MAX'" = 26.60. In each case, while the intensity range to

which the output window 162 is mapped is adjusted, the output window 162 continues to be

mapped to the entire color spectrum 156. Thus, for output window 162', intensity value

OW_MAX' = 39.50 is mapped to the highest color value in spectrum 156 (the contrasting white

color, in the presently disclosed embodiment), while intensity value OW_MIN' = 26.70 is

mapped to the lowest value in spectrum 156. When the output window 162 is adjusted down

(reference numeral 162"), intensity value OW_MAX" = 35.00 is mapped to the highest color

value and OW_MIN" = 22.20 is mapped to the lowest. Finally, at the lowest adjustment

(reference numeral 162'"), intensity value OW_MAX'" = 26.60 is mapped to the highest color

code and intensity value OW_MIN'" = 13.90 is mapped to the lowest.

Those of ordinary skill in the art will appreciate that the adjustment of the output

intensity window 162 as described with reference to Figure 18 is readily accomplished by

processor 52 under control of user commands. For example, as in the presently disclosed

embodiment, the output intensity window can be continuously adjusted up or down as illustrated in Figure 18 in response to depression of "up arrow" and "down arrow" keys

associated with computer 52.

The adjustment of the output intensity window mapping as illustrated in Figure 18 is

referred to as a "slicing" function due to a visual effect that is produced as a result of the

adjustment, as will be hereinafter described in further detail.

Once the output window 162 has been mapped to spectrum 156 as just described, the

"slicing" image can then be displayed. That is, by defining the output intensity window

mapping, a new assignment of color values to data in the input thermal data can be performed

in accordance with that mapping. By "in accordance with the mapping," it is meant that each

input data value is assigned the color to which that value in output window 162 is mapped.

(In one embodiment, data values in the thermal data which are below the output window 162

(i.e., data values below OW_MIN) are assigned the lowest color value, while data values in the

thermal data which are above the output window 162 (i.e., data values above OW_MAX).)

Figure 16 is a color illustration of the image presented to the operator of the system 50

in accordance with the presently disclosed embodiment of the invention, as the image would

appear on display unit 62, which may be a conventional VGA or SVGA computer monitor or

the like, or as it would appear in hardcopy form from printer 64.

As previously noted, the image of Figure 16 includes a display 158 of the input

thermal intensity data, i.e., the scanned thermal image prior to being subjected to the slice

operation described above with reference to Figures 17 and 18. Index labels designated

generally with reference numeral 170 along the right-hand side of input image 158 indicate that the input thermal data from the scan image ranges between 13.90 and 39.50. Spectrum

156 also appears in the display image of Figure 16.

An output image 172 is disposed generally on the right-hand side of the image of

Figure 16. Output image 172 is generated by subjecting the input thermal data used to

generate the input image 158 to the thermal radiation slice processing (block 160 in Figure

14). Index labels designated generally with reference numeral 174, disposed to the left of

output image 172, indicate that the output image 172 spans a thermal intensity range between

OW_MIN = 22.20 and OW_MAX = 35.00 as depicted in Figure 16.

In accordance with an important aspect of the invention, and as previously described,

the system 50 allows the operator to adjust the output image window up and down. A menu

176 along the bottom of the image of Figure 16 indicates that in the presently disclosed

embodiment, the output image adjustment is accomplished by depressing the "+" or "-" keys

associated with computer 52. In the image of Figure 16, the input intensity window is

represented by bar 155, and can be seen to extend over a range between IW_MIN = 13.90 and

IW_MAX = 39.50 (25.60 units), while the output intensity window, represented by bar 162,

extends over a range between OW_MIN = 22.20 and OW_MAX = 35.00 (12.80 units, or an output

window scaling factor of ^lA, as previously discussed). Menu 176 further indicates that the

"PgDn" and "PgUp" keys associated with computer 52 can be used to narrow or widen the

output image intensity window, i.e, to decrease or increase the output window scaling factor.

Use of the thermal imaging system in accordance with the presently disclosed

embodiment of the invention will now be described. First, the patient is placed in scanning

bed 54 (see Figure 6), and the operator positions the patient appropriately using the control on operator console 70, so that the anatomical area of interest is positioned within the scanning

field.

Next, the thermal scan is performed, to derive a 256x 256 matrix of thermal data to

processed as described above. At this stage, the input image 158 and an output image 172

may be displayed on display 62.

As previously discussed, the present invention is believed to be advantageously

applicable to detection, identification and/or diagnosis of certain disorders, such as cancer,

that are responsible for certain characteristic internal metabolic (i.e., thermal) activity, where

such internal metabolic activity has not heretofore been readily or reliably detectable using

conventional thermographic imaging systems such as have been shown in the prior art. The

thermal radiation "slicing" processing in accordance with the present invention, however,

enables such internal metabolic activity to be more readily detected, identified and perceived.

This is accomplished by identifying certain characteristic variations in the images resulting

from performing the slicing operation on scanning data one or more times. That is, it has been

found that there are certain types of variations in the image which, when detected, can

provide useful information about underlying internal metabolic activity.

After a thermal scan has been taken of an anatomic area of interest, the operator of the

thermal system in accordance with the presently disclosed embodiment of the invention

adjusts the output image 172 such that, in the area of interest, i.e., in an area in which an

internal thermal body, such as a tumor or the like, is suspected of existing, the color value

representing the highest thermal intensity value is mapped to the most thermally intense

location in the area of interest. Visually, this is accomplished by adjusting or shifting the output window up or down until a small white area — initially merely a dot — appears in the

area of interest. (Recall that the highest color value in the spectrum 156 is white, purposefully

in contrast to the color values immediately below, red in the presently disclosed embodiment

of the invention. This purposeful contrast enables the most thermally intense location(s) in an

image to be readily observed).

In Figure 16, the output window has been shifted by the operator so that such a white

dot, designated with reference numeral 178 in Figure 16, has appeared in the patient's left

clavicle region. To better illustrate the diagnostic process in accordance with the presently

disclosed embodiment of the invention, dot 178 is reproduced in Figure 19.

Next, the physician shifts the input temperature window up incrementally. In the

embodiment of Figure 16, a legend 180 indicates the increment for units in the input and

output intensity windows is 0.10, so that shifting output window 162 up one increment will

cause it to span an intensity range from OW_MIN = 22.30 to OW_MA = 35.10, shifting it up two

increments will cause window 162 to span a range OW_MIN = 22.40 to 0¹W_MAX = 35.20, and so

on.

Because of the internal thermal radiation behavior discussed above with reference to

Figures 1-5, an therefore in accordance with an important aspect of the present invention, it

has been clinically found by the inventors that when a metabolically active body (e.g., a

cancer) is present within a patient's body, as the output window 162 is shifted up as described

herein, the region 178 mapped to the color value at the the highest end of spectrum 156 will

tend to increase in size in a more or less consistent and uniform manner. The point at which such sudden, non-incremental or non-uniform transition occurs can, it is believed, be

correlated with the depth of the internal metabolically active region underlying region 178.

Referring to Figure 19, for example, recall that region 178 represented the small white

dot in the scanning area of interest. Assuming that dot 178 is present due to an internal

metabolically active body (e.g., a tumor) when output window 162 is shifted up one

increment, region 178 will enlarge slightly, appearing as a generally well-defined area as

represented by reference numeral 178' in Figure 20. Shifting the output window 162 up one

further increment will cause region 178 to enlarge still further, but still in a more or less

bounded fashion, so as to appear as designated with reference numeral 178", and shifting

window 162 still another increment will cause region 178 to enlarge to appear as designated

with reference numeral 178'". This gradual and more or less uniform enlarging of region 178

can be observed by the operator on display 62.

It has been found that upon further incremental shifting of output window 162, a

suspected region which initially appeared as a dot 178 in Figure 19 and which, upon shifting

the output window incrementally, tended to incrementally enlarge, will at some point

abruptly enlarge in an amoφhous and discontinuous manner as output window 162 is

incrementally shifted. That is, as output window 162 is incremented, causing gradual and

smooth enlargement of region 178, the region will eventually suddenly enlarge, for example,

from the region designated with reference numeral 178'" in Figure 20 to that designated 178""

with only one (or perhaps two) incremental shifts in output intensity window 162. Such

abrupt, non-incremental enlarging is readily distinguished from the gradual, incremental

enlarging that region 178 undergoes at first, and can be readily observed by the operator. While in the presently disclosed embodiment of the invention it is considered that an

operator will be present to observe the sudden, discontinuous expansion of region 178, thus

giving insight into the depth of the underlying metabolic activity reflected by region 178, it is

also contemplated that known or to-be-developed computational algorithms can be applied to

enable certain characteristic changes or variations in the images, such as the first incremental

continuous and later discontinuous expansions (i.e., discontinuities) discussed above to be

detected by means of computer analysis, i.e., without the intervention of human observation,

or at least without the full reliance upon human observation.

In accordance with another important aspect of the present invention, the point at

which the non-incremental and discontinuous transition of region 178 (i.e., the transition from

region 178'" to region 178"") occurs can be correlated to the depth of the internal metabolic

body that the thermal region 178 reflects. That is, the magnitude of the overall shift in output

intensity window 162 which causes region 178 to gradually enlarge from its appearance

designated with numeral 178 to its appearance designated with reference numeral 178"" can

be correlated to the depth of the internal metabolic body. This correlation can take into

account the known relative thermal conductivities of various types of body tissue (fatty tissue,

muscle, bone, etc.), as previously discussed.

As noted above, one advantageous aspect of the imaging system in accordance with

the present invention is its ability to generate accurate and meaningful results in spite of

variations in thermal radiation intensity ("temperature") from patient to patient. This

capability arises in part from a reference value calculation function of the processing software

represented by the flow diagram of Figure 14. The reference value calculation, represented by block 180 in Figure 14, operates in one embodiment as follows: after a thermally radiating

object in an anatomical area of interest has been identified, for example as discussed above

with reference to Figure 19, the system operator uses the mouse or other cursor control device

associated with computer system 52, to identify a reference region at some other anatomical

area appearing in the image likely to have the same thermal characteristics under normal

circumstances. For example, since the region 178 identified in the output image (Figures 16

and 19) in the illustrative example was located on the patient's left shoulder/clavicle area, the

operator may designate an area in the patient's right shoulder/clavicle area as the reference.

Block 180 represents a function of the software executed by processor 52 wherein an

average thermal radiation intensity value is calculated for the reference area identified by the

operator. This value may then be used as a reference against which the thermal intensity of

the suspected region (spot 178) can be compared in order to ascertain the relative intensity

thereof. Block 182 in Figure 14 represents the operation of calculating the thermal intensity

associated with the suspected area. As with the derivation of the reference value, the

operation represented by block 182 in one embodiment involves the operator identifying the

boundaries of the suspected area (for example, by using the mouse or cursor control device

associated with computer 52).

As applied to diagnosis of cancerous conditions, for example, a threshold in the

difference between the thermal radiation intensity of the suspected area (spot 178) and the

reference value can be established, such that suspected areas which exceed this threshold are

considered indicative of a cancerous condition. It is to be noted that, in accordance with one aspect of the present invention, by

assessing the thermal intensity of a suspected area by comparison to a reference value derived

from the patient (as opposed to a reference value taken from a population average, for

example), the effects of patient-to-patient variations in base levels of thermal radiation are

minimized.

Referring now to Figure 20, there is shown still another functional capability of the

system 50 in accordance with the presently disclosed embodiment of the invention. In

particular, illustrated in Figure 20 is a temperature-measurement function whereby the

operator can identify selected locations in a thermal image and cause the temperature at those

locations to be displayed. Using a mouse or other cursor control device associated with

computer 52, the operator causes a set of cross-hairs 190 to move about the image. At desired

locations, the operator then depresses the mouse button or another key associated with

computer 52. This causes the location to be labeled (labels A-K appear in Figure 20), and in a

table 192 to the left of the image, the respective temperatures corresponding to the selected

points are listed. This function may be advantageously employed to identify areas of high

thermal radiation, suggesting that a suspicious internal thermal body is present in those areas

and indicating, therefore, that the thermal "slicing" operation should be performed with data

in the area to further assess the condition.

From the foregoing detailed description of a specific embodiment of the invention, it

should be apparent that a method and apparatus for thermal radiation imaging has been

disclosed. In accordance with a significant aspect of the invention, the method and

corresponding apparatus enables thermal radation data to be processed in such a manner so as to facilitate generation of images reflecting internal thermal conditions, i.e., thermal

conditions inside a human body.

Although a specific embodiment of the present invention has been disclosed herein in

some detail, this has been done soley for the puφoses of illustrating various aspects of the

present invention, and is not intended to be limiting with respect to the scope of the invention.

It is to be understood that various substitutions, alterations and modifications may be made to

the invention as disclosed, including but not limited to those specifically discussed herein,

without departing from the spirit and scope of the invention as defined in the appended

claims, which follow.

PCT WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERAΗON TREATY (PCT)

(51) International Patent Classification 6 ; (11) International Publication Number: WO 98/46976 G01N A2

(43) International Publication Date: 22 October 1998 (22.10.98)

(21) International Application Number: PCT/IB 98/01320 (81) Designated States: AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE,

(22) International Filing Date: 26 March 1998 (26.03.98) GH, GM, GW, HU, ID, IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ,

(30) Priority Data: TM, TR, TT, UA, UG, UZ, VN, YU, ZW, ARIPO patent

60/042,214 31 March 1997 (31.03.97) US (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), Eurasian patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European patent (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU,

(71)(72) Applicants and Inventors: LIU, Zhong, Qi [CN/CN]; MC, NL, PT, SE), OAPI patent (BF, BJ, CF, CG, CI, CM, #3-4-101 Furunli, Beijing 100080 (CN). WANG, Chen GA, GN, ML, MR, NE, SN, TD, TG). [CN/CN]; KeJie Fu Hua Building A-101, Shangdi, Beijing 100080 (CN).

Published

Without international search report and to be republished upon receipt of that report.

(54) Title: METHOD AND APPARATUS FOR THERMAL RADIATION IMAGING

(57) Abstract

A method and apparatus for thermal imaging is disclosed which enables a clinician to obtain visual images reflecting metabolic activity within a patient's body. A scanning system is configured to scan an area on the patient's body to obtain infrared intensity data. The data is digitized and processed prior to being displayed. The data processing includes a "slicing" function in which infrared intensity values are assigned color values in accordance with an output window. By redefining the mapping of the output window to the color spectrum, the data can be manipulated such that the visual display reflects metabolic activity within the patient's body under the scanning area.

FOR THE PURPOSES OF INFORMATION ONLY

Codes used to identify States party to the PCT on the front pages ol pamphlets publishing international applications under the PCT.

AL Albania ES Spain LS Lesotho SI Slovenia

AM Armenia FI Finland LT Lithuania SK Slovakia

AT Austria FR France LU Luxembourg SN Senegal

AU Australia GA Gabon LV Latvia SZ Swaziland

Azerbaijan GB United Kingdom MC Monaco TD Chad

BA Bosnia and Herzegovina GE Georgia MD Republic of Moldova TG Togo

BB Barbados GH Ghana MG Madagascar TJ Tajikistan

BE Belgium GN Guinea MK The former Yugoslav TM Turkmenistan

BF Burkina Faso GR Greece Republic of Macedonia TR Turkey

BG Bulgaria HU Hungary ML Mali TT Trinidad and Tobago

BJ Benin IE Ireland MN Mongolia UA Ukraine

BR Brazil IL Israel MR Mauritania UG Uganda

BY Belarus IS Iceland MW Malawi US United States of America

CA Canada IT Italy MX Mexico uz Uzbekistan

CF Central African Republic P Japan NE Niger VN Viet Nam

CG Congo KE Kenya NL Netherlands U Yugoslavia

CH Switzerland KG Kyrgyzstan NO Norway ZW Zimbabwe

CI Cote d'lvoire KP Democratic People's NZ New Zealand

CM Cameroon Republic of Korea PL Poland

CN China KR Republic of Korea PT Portugal cu Cuba KZ Kazakstan RO Romania

CZ Czech Republic LC Saint Lucia RU Russian Federation

DE Germany LI Liechtenstein SD Sudan

DK Denmark LK Sri Lanka SE Sweden

EE Estonia LR Liberia SG Singapore CLAIMS:

1. An imaging system, comprising:

a scanning subsystem for generating digital data corresponding to infrared radiation

from a scanned area of a patient's body;

a processor, coupled to said scanning subsystem to receive said digital data, for

processing said data to generate image data reflecting metabolic activity

internal to the patient's body beneath the scanned surface area.

2. An imaging system in accordance with claim 1, further comprising a display system

for generating a display corresponding to said image data.

3. An imaging system in accordance with claim 1, wherein said digital data comprises

data values corresponding to levels of infrared radiation intensity at a plurality of image

locations within said scanned area.

4. An imaging system in accordance with claim 3, wherein said processor assigns color

values from a predetermined range within a spectrum of color values to each data value, such

that different infrared radiation intensity levels are assigned different color values;

and wherein said color values comprise said image data, such that when said imaging

system generates a display corresponding to said image data, different colors

on said display correspond to different radiation levels in said scanned area. 5. An imaging system in accordance with claim 4, further comprising a control system,

coupled to said processor, said display system, and said scanning subsystem, for facilitating

user control of said imaging system.

6. An imaging system in accordance with claim 5, wherein said processor is responsive

to said control system to adjust said assignment of color values to data values, such that said

display is correspondingly adjusted.

7. An imaging system in accordance with claim 6, wherein said processor assigns said

data values to color values by

(a) defining an output intensity window of data values between a maximum output

data value OW_MAX and a minimum output data value OW_MIN;

(b) mapping said output intensity window of color values to said spectrum of color

values such that OW_MAX is mapped to a highest color value in said spectrum

of color values and OW_MIN and is mapped to a lowest color value in said

spectrum of color values, with all data values between OW_MAX and OW_MIN

being evenly mapped to color values between said highest and lowest color

values in said color spectrum;

(c) assigning color values to said data values in accordance with said mapping in step

(b). 8. An imaging system in accordance with claim 9, wherein said processor adjusts said

assignment of color values to data values to color values by adjusting said mapping of said

output window of color values to said spectrum of color values.

9. An imaging system in accordance with claim 8 wherein said processor adjusts said

mapping of said output window of color values by adding a predetermined incremental value

to both OW_MAX and OW_MI .

10. A method of radiation imaging, comprising:

(a) scanning a scanning area to obtain digital data values corresponding to levels of

radiation intensity at a plurality of points within said scanned area;

(b) assigning a color value within a spectrum of color values to each digital data

value, to generate image data; and

(c) displaying said image data.

11. A method in accordance with claim 10, further comprising:

(d) adjusting said assignment of color values to obtain adjusted image data; and

(e) displaying said adjusted image data.

12. A method in accordance with claim 11, wherein said step (b) of assigning a color

value to each digital data value comprises:

(f) defining an output intensity window of data values between a maximum output

data value OW_MAX and a minimum output data value OW_MIN; (g) mapping said output intensity window of color values to said spectrum of color

values such that OW_MAX is mapped to a highest color value in said spectrum

and OW_MIN and is mapped to a lowest color value in said spectrum of color

values, with all data values between OW_MAX and OW_MIN being evenly mapped

₅ to color values between said highest and lowest color values in said color

spectrum;

(h) assigning color values to said data values in accordance with said mapping in step

(g)-

13. A method in accordance with claim 12, wherein said step (d) of adjusting said

l o assignment of color values comprises :

(i) adding or subtracting a predetermined incremental amount from both OW_MAX and

OW_MIN to redefine said output intensity window of data values;

(j) mapping said redefined output intensity window of color values to said spectrum of

color values such that OW_MAX is mapped to a highest color value in said

is spectrum and OW_MIN and is mapped to a lowest color value in said spectrum

of color values, with all data values between OW_MAX and OW_MIN being evenly

mapped to color values between said highest and lowest color values in said

color spectrum;

14. A method in accordance with claim 13, wherein said steps (b) through (j) are

20 performed by a computer. 15. A method of detecting internal metabolic activity in a patient, comprising:

(a) scanning a scanning area on said patient's body to obtain digital data values

corresponding to levels of radiation intensity at a plurality of points within

said scanned area;

(b) assigning a color value within a spectrum of color values to each digital data

value, to generate image data; and

(c) displaying said image data.

16. A method in accordance with claim 15, further comprising:

(d) adjusting said assignment of color values to obtain adjusted image data; and

(e) displaying said adjusted image data.

17. A method in accordance with claim 16, wherein said step (b) of assigning a color

value to each digital data value comprises:

(f) defining an output intensity window of data values between a maximum output

data value OW_MAX and a minimum output data value OW_MIN;

(g) mapping said output intensity window of color values to said spectrum of color

values such that OW^χ is mapped to a highest color value in said spectrum

and OW_M1N and is mapped to a lowest color value in said spectrum of color

values, with all data values between OW_MAX and OW_MIN being evenly mapped

to color values between said highest and lowest color values in said color

spectrum; (h) assigning color values to said data values in accordance with said mapping in step

(g)-

18. A method in accordance with claim 17, wherein said step (d) of adjusting said

assignment of color values comprises:

(i) adding or subtracting a predetermined incremental amount from both OW_MAX and

OW_{M N} to redefine said output intensity window of data values;

(j) mapping said redefined output intensity window of color values to said spectrum of

color values such that OW_MAX is mapped to a highest color value in said

spectrum and OW_MIN and is mapped to a lowest color value in said spectrum

of color values, with all data values between OW_MAX and OW_MIN being evenly

mapped to color values between said highest and lowest color values in said

color spectrum;

19. A method in accordance with claim 18, wherein said steps (b) through (j) are

performed by a computer.

20. A method in accordance with claim 16, further comprising:

(f) detecting at least one predetermined type of variation in said adjusted image as

compared with said image displayed in step (c).

21. A method in accordance with claim 20, wherein said step of detecting is performed by

a computer.

Claims

CLAIMS: 1. An imaging system, comprising: a scanning subsystem for generating digital data corresponding to infrared radiation from a scanned area of a patient's body; a processor, coupled to said scanning subsystem to receive said digital data, for processing said data to generate image data reflecting metabolic activity internal to the patient's body beneath the scanned surface area.

2. An imaging system in accordance with claim I, further comprising a display system for generating a display corresponding to said image data.

3. An imaging system in accordance with claim 1, wherein said digital data comprises data values corresponding to levels of infrared radiation intensity at a plurality of image locations within said scanned area.

4. An imaging system in accordance with claim 3, wherein said processor assigns color values from a predetermined range within a spectrum of color values to each data value, such that different infrared radiation intensity levels are assigned different color values; and wherein said color values comprise said image data, such that when said imaging system generates a display corresponding to said image data, different colors on said display correspond to different radiation levels in said scanned area. <Desc/Clms Page number 42> 5. An imaging system in accordance with claim 4, further comprising a control system, coupled to said processor, said display system, and said scanning subsystem, for facilitating user control of said imaging system.

6. An imaging system in accordance with claim 5, wherein said processor is responsive to said control system to adjust said assignment of color values to data values, such that said display is correspondingly adjusted.

7. An imaging system in accordance with claim 6, wherein said processor assigns said data values to color values by (a) defining an output intensity window of data values between a maximum output data value OWMAX and a minimum output data value OWMIN; (b) mapping said output intensity window of color values to said spectrum of color values such that OWMAX is mapped to a highest color value in said spectrum of color values and OWMIN and is mapped to a lowest color value in said spectrum of color values, with all data values between OWMAX and OWMIN being evenly mapped to color values between said highest and lowest color values in said color spectrum; (c) assigning color values to said data values in accordance with said mapping in step (b). <Desc/Clms Page number 43>

8. An imaging system in accordance with claim 9, wherein said processor adjusts said assignment of color values to data values to color values by adjusting said mapping of said output window of color values to said spectrum of color values.

9. An imaging system in accordance with claim 8 wherein said processor adjusts said mapping of said output window of color values by adding a predetermined incremental value to both OWMAX and OWMIN.

10. A method of radiation imaging, comprising: (a) scanning a scanning area to obtain digital data values corresponding to levels of radiation intensity at a plurality of points within said scanned area; (b) assigning a color value within a spectrum of color values to each digital data value, to generate image data; and (c) displaying said image data.

11. A method in accordance with claim 10, further comprising: (d) adjusting said assignment of color values to obtain adjusted image data; and (e) displaying said adjusted image data.

12. A method in accordance with claim 11, wherein said step (b) of assigning a color value to each digital data value comprises: (f) defining an output intensity window of data values between a maximum output data value OWMAX and a minimum output data value OWMIN; <Desc/Clms Page number 44> (g) mapping said output intensity window of color values to said spectrum of color values such that OWMAX is mapped to a highest color value in said spectrum and OWMIN and is mapped to a lowest color value in said spectrum of color values, with all data values between OWMAX and OWMIN being evenly mapped to color values between said highest and lowest color values in said color spectrum; (h) assigning color values to said data values in accordance with said mapping in step (g).

13. A method in accordance with claim 12, wherein said step (d) of adjusting said assignment of color values comprises: (i) adding or subtracting a predetermined incremental amount from both OWMAX and OWMIN to redefine said output intensity window of data values; (j) mapping said redefined output intensity window of color values to said spectrum of color values such that OWMAX is mapped to a highest color value in said spectrum and OWMIN and is mapped to a lowest color value in said spectrum of color values, with all data values between OWMAX and OWMIN being evenly mapped to color values between said highest and lowest color values in said color spectrum; 14. A method in accordance with claim 13, wherein said steps (b) through (j) are performed by a computer. <Desc/Clms Page number 45>

15. A method of detecting internal metabolic activity in a patient, comprising: (a) scanning a scanning area on said patient's body to obtain digital data values corresponding to levels of radiation intensity at a plurality of points within said scanned area; (b) assigning a color value within a spectrum of color values to each digital data value, to generate image data; and (c) displaying said image data.

16. A method in accordance with claim 15, further comprising: (d) adjusting said assignment of color values to obtain adjusted image data; and (e) displaying said adjusted image data.

17. A method in accordance with claim 16, wherein said step (b) of assigning a color value to each digital data value comprises: (f) defining an output intensity window of data values between a maximum output data value OWMAX and a minimum output data value OWMIN; (g) mapping said output intensity window of color values to said spectrum of color values such that OWMAX is mapped to a highest color value in said spectrum and OWMIN and is mapped to a lowest color value in said spectrum of color values, with all data values between OWMAX and OWMIN being evenly mapped to color values between said highest and lowest color values in said color spectrum; <Desc/Clms Page number 46> (h) assigning color values to said data values in accordance with said mapping in step (g)- 18.

A method in accordance with claim 17, wherein said step (d) of adjusting said assignment of color values comprises: (i) adding or subtracting a predetermined incremental amount from both OWMAX and OWMIN to redefine said output intensity window of data values; (j) mapping said redefined output intensity window of color values to said spectrum of color values such that OWMAX is mapped to a highest color value in said spectrum and OWMIN and is mapped to a lowest color value in said spectrum of color values, with all data values between OWMAX and OWMIN being evenly mapped to color values between said highest and lowest color values in said color spectrum; 19. A method in accordance with claim 18, wherein said steps (b) through (j) are performed by a computer.

20. A method in accordance with claim 16, further comprising: (f) detecting at least one predetermined type of variation in said adjusted image as compared with said image displayed in step (c).

21. A method in accordance with claim 20, wherein said step of detecting is performed by a computer.