US2849621A - Methods and apparatus for X-ray therapy - Google Patents

Description

Aug. 26, 1958 J. w. CLARK METHODS AND APPARATUS FOR X-RAY THERAPY Filed March 25, 1955 2 Sheets-Sheet 1 mi mm .mw

INVENTOR. file N W Came/c Aug. 26, 1958 J. W/CLARK METHODS AND APPARATUS FOR X-RAY THERAPY 2 Sheets-Sheet 2 INVENTOR. fa/m W C2 48% BY %mu-A) flrrae/vzz Filed March 25, 1955 METHODS AND APPARATUS FOR X-RAY THERAPY John W. Clark, Santa Monica, Calif., assignor to Litton industries of California, Beverly Hills, Calif.

Application March 25, 1955, Serial No. 496,732

14 Claims. (Cl. 250-64) This invention relates to methods and apparatus for X-ray therapy and more particularly to therapeutic X-ray apparatus wherein a radioactive source of relatively soft or low voltage X-rays is utilized to provide a boresight for aligning a source of relatively hard or high voltage X-rays or gamma rays with an object to be irradiated. For purposes of simplicity, the term X-rays will be utilized hereinafter as generic to both X-rays and gamma rays, since gamma rays are in reality only exceptionally hard X-rays.

The therapeutic value of X-rays in the treatment of tumors and other physical disorders has longbeen recognized by the medical profession. In general, X-ray therapy, as contrasted with the diagnostic application of X-rays, requires extremely intense irradiation of a relatively small area which defines the region to be treated.

ing extremely hard X-rays or gamma rays, these X-ray sources including both exceptionally high voltage electronic X-ray apparatus and nucleonic X-ray apparatus employing materials such as radioactive cobalt, for example.

Although each of the above forms of apparatus has successfully proven its therapeutic value, there is at least one serious disadvantage attendant their use, namely, the fact that it is difficult to align the X-ray source with the particular area to be irradiated. More specifically, in setting up the apparatus for a treatment it is usually necessary to align the X-ray source with a relatively small area within the patients body; however, owing to the fact that the relative position of organs or tissue within the body tends to change as the body assumes various positions, it is extremely diflicult to foretell from an external examination the precise location of the tissue to be treated.

in the past it has been proposed that the high voltage X-ray source be utilized first in combination with a fluoroscope or X-ray plate for determining the position of the tissue to be treated, and thereafter as a therapeuticinstrument. As a rule, however, this proposal is rejected for several reasons. Firstly, the maximum amount of radiation to which the body may be subjected is relatively limitedglaccordingly, the utilization of the therapy apparatus for positioning the patient appreciably decreases the amount of exposure time available for therapy. Secondly, irradiation of healthy tissue may also produce harmful afterefiects. Thirdly, therapeutic X-ray apparatus is not in general amenable to use with fluoroscopic apparatus or X-ray plates owing to the fact that the-high voltage rays used for therapy do not give sufiicient contrast to enable the radiologist to locate the site of irradiation fiuoroscopically. in other words, the various portions of the body are substantially equally transparent to X-rays or gamma rays of relatively short Wavelength.

Owing to the foregoing limitations on the use of therated States Patent F 2,849,621 Patented Aug. 26, 1958 ice peutic X-ray apparatus for properly positioning the patient, it has become common practice to employ anatomical surveying and its concommitant precise measurements to determine the location of the tissue to be treated. However, this technique is relatively expensive and time consuming, and requires a skilled anatomist to determine the area to be irradiated. Of even more importance is the fact that in any individual case, the area selected for irradiation may be incorrect owing to the fact that the basic measurements utilized in anatomical surveys are based to some extent on statistics.

The present invention, on the other hand, obviates the above and other disadvantages of the prior art therapeutic X-ray apparatus by providing methods and apparatus which are utilizable in conjunction with a source of high energy X-rays for initially determining the location of tissue to be subsequently treated by high energy radiation. According to the basic concept of the invent-ion there is provided a therapeutic X-ray apparatus wherein a radioactive source of relatively low voltage X-rays is utilized as a boresight for aligning a source of relatively high voltage X-rays with an object to be irradiated. More specifically, there is provided a high voltage therapeutic X-ray apparatus which includes as one of its elements a radioactive source of low voltage X-rays, this latter source being movable to a point coincident with the center line of the high voltage X-ray beam.

In operation, according to the methods of the invention, the radioactive source is first utilized in cooperation with a fiuoroscope, for example, to align the center line of the high voltage X-ray beam with the center of the region to be irradiated, after which the associated masks and cones of the high voltage X-ray source are adjusted so that only the desired predetermined area will be visible to the high voltage X-ray beam. The low voltage radioactive source is then withdrawn from the radiation cone of the high voltage source after which the high energy source is actuated to irradiate the area to be treated.

According to the invention the methods and apparatus herein disclosed are equally applicable to both electronic therapeutic X-ray apparatus and nucleonic or radioactive therapeutic X-ray apparatus. It will also be recognized; of course, that the low voltage radioactive source employed as the boresightlfor the therapeutic machine may be housed within the therapeutic apparatus itself or may be housed, in an associatedequiprnent adapted to cooperate With existing therapeutic X-ray apparatus.

It is therefore an object of the invention to provide.

Another object of the invention is to provide a high voltage therapeutic X-ray apparatus which employs a radioactive source of relatively low voltage X-rays as a boresight for aligning the therapeutic apparatus with an object to be irradiated.

It is also an object of the invention to provide a therapeutic X-ray apparatus which utilizes a relatively low voltage radioactive source, movable into a position coincident with the center line of the therapeutic X-ray beam, for orienting the therapeutic X-ray beam with respect to a predetermined area to be irradiated.

A further object of the invention is to provide a therapeutic X-ray apparatus which includes as one of its elements a radioactive auxiliary source of low voltage X-rays, the auxiliary source being adapted to project a beam of relatively soft X-rays along the axis of the therapeutic X-ray beam which is produced when the therapeutic X-ray source is actuated.

Still another object of the invention is to provide methods for aligning a therapeutic X-ray apparatus with 3 an object to be irradiated with high voltage X-rays by first radiographically aligning the object with a low voltage X-ray beam emitted from a radioactive source positioned along the center line of the high voltage X-ray beam.

A still further object of the invention is to provide methods for aligning a therapeutic X-ray apparatus with an object to be irradiated by first irradiating the object with low voltage X-rays from an auxiliary radioactive source, radiographically observing the position of the object to be irradiated with respect to the position of the therapeutic X-ray source, and moving the object relative to the therapeutic source until the object lies within the cone which defines the therapeutic X-ray beam.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which several embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.

Fig. 1 is a schematic view, partly in section, of a therapeutic X-ray apparatus, which includes a nucleonic high voltage therapeutic X-ray source and one embodiment of the novel alignment device of the invention;

Figs. 2 and 3 are isometric views of alignment sights which may be employed with the therapeutic X-ray apparatus of the invention;

Fig. 4 is a sectional view of a modified form of nucleonic therapeutic X-ray apparatus, according to the invention; and

Figs. 5 and 6 are schematic views, partly in section, of a therapeutic X-ray apparatus according to the invention which utilizes an electronic X-ray source to provide the therapeutic X-ray beam.

With reference now to the drawings, wherein like or corresponding parts are designated by the same reference characters throughout the several views, there is shown in Fig. 1 a therapeutic X-ray apparatus which utilizes the novel X-ray boresight of the invention for aligning a particular area within a patient 10 with the axis of the therapeutic X-ray beam. Basically, the therapeutic X-ray apparatus includes four principal components, namely; a radioactive source 14, which may be radioactive cobalt, for example, for generating a therapeutic X-ray beam, a housing assembly, generally designated 16, for encapsulating and shielding source 14, a radioactive source 18 of relatively soft or low voltage X-rays which is utilized for aligning the therapeutic beam with an object to be irradiated, and an actuating mechanism, generally designated 20, for moving source 18 to a position coincident with the axis of the therapeutic X-ray beam.

As shown in Fig. 1, housing assembly 16 includes a massive shielding member 22 for containing therapeutic X-ray source 14, shielding member 22 preferably being constructed of a relatively heavy material such as lead and having a conically shaped aperture 23 communicating between source 14 and the exterior of member 22. In operation, as will be more evident from the description set forth hereinbelow, passage 23 is operative as a beam forming channel so that the therapeutic X-ray beam is projected concentric with the axis 24 of passage 23. In addition, housing assembly 16 also includes a shutter mechanism, generally designated 26, for selectively withdrawing a lead shutter 28, which normally blocks passage 23, into an adjacent cavity 30 in member 22. In the particular embodiment shown in Fig. I shutter 28 is actuated through a rack and pinion mechanism 32 affixed to the outer periphery of member 22. It is clear, of course, that the pinion may be rotated either 4 manually or through an associated motor driven mechanism, not shown.

According to the invention, low voltage radioactive source 18 is preferably composed of thulium or a similar radioactive isotope suitable for low energy radiography, and is normally postioned within a shielding cavity 34 in member 22, substantially as shown, so that radiation from the low energy source is normally precluded from radiating into the surrounding area. In the embodiment of the invention shown in Fig. 1, source 18 is connected to actuator mechanism 20 through a push rod 36 which is axially movable in a bearing 38, push rod 36 constituting the plunger of a solenoid 40 which is energizable upon closure of a switch 42 to project source 18 to a position coincident with axis 24 of the therapeutic X-ray beam. In order to insure that source 18 is properly positioned relative to axis 24, push rod 36 includes a relatively thick lower region, as viewed in the drawings, which bottoms againstthe lower end of bearing 38 when solenoid 40 is actuated. It will be recognized by those skilled in the art, of course, that the actuator mechanism may include other mechanical devices, such as a return spring for example, to make the actuator mechanism completely fail safe.

Consider now the operation of the therapeutic X-ray apparatus of the invention in locating and treating a particular region within a patient. The entire therapeutic X-ray apparatus and the patient are first positioned relative to each other so that axis 24 is directed toward the general location of the tissue or organ to be treated. An X-ray film cassette or fluoroscope 44 is then positioned on the side of the patient opposite the therapeutic X-ray apparatus after which switch 42 is closed, thereby projecting low voltage X-ray source 18 into its position coincident with axis 24. As a consequence thereof the pertinent region of the patients body is illuminated with relatively soft X-rays or gamma rays which are of sutficiently low energy to produce a good X-ray picture of the area illuminated.

If it is assumed that a fluoroscope is employed in conjunction with the therapeutic X-ray boresight of the invention, source 18 provides a fluoroscopic image having good contrast, or in other words, an image in which the various elements of the body are readily discernible. Accordingly, the operator may readily determine the internal location of the tissue to be treated and move the patient and therapeutic apparatus relative to each other until axis 24 is aligned with this tissue. Thereafter, associated masks and cones, not shown in Fig. 1 for purposes of simplicity, are adjusted so that only the desired area is irradiated.

When the foregoing steps have been carried out switch 42 is again returned to its normal or open position, thereby returning low voltage source 18 to its shielded position within cavity 34. Shutter mechanism 26 is then actuated to withdraw shutter 28 into cavity 30, whereby the desired region within the patient is exposed to the high energy therapeutic X-ray beam from source 14. At the conclusion of the treatment shutter mechanism 26 is again actuated to return shutter 28 to its normal position within aperture 23, thereby shielding the patient from further irradiation.

It will be recognized from the foregoing description that radioactive source 18 is employed as a boresight for aligning the therapeutic X-ray beam with a particular region to be irradiated. It will also be recognized, however, that source 18 produces a relatively wide beam which is delimited only by its position with respect to the right hand end of passage 23, as viewed in Fig. 1, or if associated masks or cones are utilized, by its position with respect to the openings in these elements. It is clear, therefore, that to utilize source 18 for aligning axis 24 with the object to be irradiated some mechanism should be provided to indicate the point on fluoroscope 44 intercepted by axis 24. In other words, even though the particular tissue to be treated is made visible on the fluoroscope by virtue of the low energy radiation from source 18, a sight should be provided to indicate the positional error between the tissue to be treated and axis 24.

With reference now to Figs. 2 and 3, these are shown two forms of sights which may be removably mounted at the end of aperture 23 in the therapeutic apparatus of Fig. l, or in one of the associated cones, for indicating to the operator the location of the axis of the therapeutic X-ray beam. Referring now with particularity to Fig. 2 there is illustrated a cross hair sight which includes a mounting ring 50 which is adapted to be mounted concentrically with one of the cones utilized to form the therapeutic X-ray beam, and a pair of crossed lead bars 52 and 54 which are mounted within ring 50. It will be noted that bars 52 and 54 are substantially rectangular in cross section, their transverse dimension being relatively small so as to define a relatively fine cross when viewed along the axis of ring while their depth parallel to axis 24 is sufiiciently large to absorb incident X-rays striking the bars.

In operation the sight of Fig. 2 is mounted within either aperture 23 or one of the associated cones so that the juncture of bars 52 and 54 is coincident with axis 24. Accordingly, when solenoid 40 is energized to project low voltagesource 18 to its position coincident with axis 24, a cross will appear on fiuoroscope 44 owing to the fact that X-rays which strike bars 52 and 54 are absorbed, the juncture of the cross defining the point at which axis 24 intercepts the fluoroscopic screen.

It will be recognized, of course, that numerous other forms of sights may be employed with the therapeutic X-ray apparatus of the invention. As shown in Fig. 3, for example, a ring sight comprising a lead ring 56 mounted on a plastic base 58 may be employed in lieu of the sight shown in Fig. 2. As still another alternative fiuoroscope screen 44- may be integrally connected mechanically to the therapeutic X-ray apparatus housing so that movement of the therapeutic X-ray source relative to the patient will be accompanied by a corresponding movement in the fluoroscope screen. If this arrangement is employed the utilization of a separate sight of the types shown in Figs. 2 and 3 may be avoided since the point at which axis 24 intersects the fiuoroscope screen is fixed and may be indicated by a simple marking on the screen.

In the foregoing description it has been assumed that fluoroscopic techniques were being employed during the initial positioning of the patient. It is obvious, however, that an X-ray film cassette could also be employed in conjunction with the therapeutic X-ray source for determining the position of the region to be treated with respect to the axis of the therapeutic X-ray source. It should also be clear from the description of the invention set forth hereinabove that its basic concept resides in the utilization of a radioactive source of low voltage X-rays as a boresight for a therapeutic X-ray apparatus, and is not to be restricted by the specific embodiment of the invention shown in Fig. 1.

With reference now toFig. 4, there is shown a modified form of therapeutic X-ray apparatus, according to the invention, wherein low voltage source 18 is confined within its own apertured housing member 60 which is hingedly mounted to main housing member 22, only a portion of which is here shown. As indicated by the dotted line 61 in Fig. 4, housing member 60 has a normal or shielding position engaging a latch 62 and is movable upon rotation of a keyed shaft 64 to an operating position in the mouth of the aperture in main housing member 22 whereby source 18 is moved to a point intercepted by axis 24 of the therapeutic X-ray beam. It will be readily apparent to those skilled in the art that shaft 64 may be rotated either manually or may be driven automatically by an air piston or similar fail safe mechanism. It should be noted too that the apparatus may be made even further fail safe by designing housing member 60 so that its center of gravity is always forward of shaft 64.

The operation of the therapeutic apparatus shown in Fig. 4 is substantially identical with the operation of the apparatus previously described with theexception that source 18 is moved into its operating position by a rotational rather than an axial movement. It is readily apparent, of course, that sights of the general type shown in Figs. 2 and 3 may also be employed in the apparatus of Fig, 4, in which instance the sight may be permanently mounted within the beam forming aperture in housing member 60.

In the two embodiments of the invention thus far disclosed it has been assumed that the novel alignment device of the invention was being employed with a nucleonic or radioactive source of high voltage therapeutic X-rays. It will be recalled, however, that the motivating concept of the invention is equally applicable to electronic therapeutic X-ray apparatus.

With reference now to Fig. 5, there is shown a sectional side elevation of a portion of an electronic therapeutic X-ray apparatus wherein the novel alignment device of the invention is employed. As illustrated in Fig. 5, the apparatus includes a conventional high voltage X-ray tube 70, only a portion of which is shown, a beam forming member 72 whose axis 74 coincides with the axis of the therapeutic X-ray beam generated at the target electrode of tube 70, a low energy radioactive source 76 movable to a position coincident with axis 74, and an actuator mechanism, generally designated 78, for selectively moving source 76 from a shielded position within the wall of member 72 to its position coincident with axis 74.

In the illustrative embodiment of the invention shown in Fig. 5 actuator mechanism 78 includes an arm 80 on one end of which radioactive source 76 is mounted, the other end of arm 80 being aflixed to a shaft 82 which is journaled in member 72 and which is rotatable through a gear train 84 upon rotation of an input shaft 86. With reference now to Fig. 6, which is a sectional View taken along section line 66 in Fig. 5, 'it will be noted that arm80 has a normal position within a cavity 88 in the wall of member 72, as indicated by the dotted line 90, and is movable in a counterclockwise direction until it engages a stop shoulder 92 in which position source 76 is coincident with the longitudinal axis of member 72. It will again be readily apparent to those skilled in the art that input shaft 86 may be driven either manually or automatically, and that the actuator mechanism may include any of numerous mechanical contrivances to insure that the apparatus is completely fail safe.

It will of course be recognized that numerous other structural embodiments of the basic concept of the invention will occur to those skilled in the art. In addition it is clear that the illustrative embodiments shown and described may be modified in many particulars without departing from the spirit of the invention. For example, the low'energy source shown in Fig. 4, together with its encapsulating housing, could be employed readily with an electronic therapeutic apparatus rather than with a radioactive high energy source. Again, for certain applications it would be permissible to permanently mount the boresight or low energy X-ray source in a position intercepted by the axis of the therapeutic beam. Accordingly, it is to be expressly understood that the invention is to be limited only by the spirit and scope of the appended claims.

What is claimed as new is:

1. In a therapeutic 'X-ray apparatus wherein a source of relatively high energy X-rays is selectively operable to project a therapeutic X-ray beam along a predetermined axis, an alignment device for radiographically determining the position of the axis relative to an object to be irradiated; said device comprising: a radioactive source of low energy X-rays; means for normally shielding said radioactive source; selectively actuable means for moving said radioactive source from its shielded position to a position coincident with the predetermined axis; and means for actuating said selectively actuable means.

2. A therapeutic X-ray apparatus comprising a first X- ray source for generating therapeutic X-rays; beam forming means for channeling X-rays from said first source along a predetermined axis to form a therapeutic X-ray beam; a second low voltage X-ray source for generating relatively low energy X-rays, said low voltage source being movable to an operating position coincident with said predetermined axis; means coupled to said beam forming means for normally shielding said low voltage X-ray source; and a selectively operable actuating mechanism coupled to said low voltage source, said actuating mechanism being responsive to an input signal for moving said low voltage source to said operating position whereby a low energy X-ray beam is projected along said predetermined axis.

3. The therapeutic X-ray apparatus defined in claim 2 wherein said low voltage X-ray source is a specimen of thulium 170.

4. The therapeutic X-ray apparatus defined in claim 2 which further includes a sight removably mounted in said beam forming means, said sight including at least one element of relatively dense material substantially intercepted by said axis, said sight being positioned between the object to be irradiated and said low voltage X-ray source when said low voltage source is in its operating position whereby the position of said axis relative to the object may be determined radiographically.

5. The therapeutic X-ray apparatus defined in claim 2 wherein said low voltage X-ray source consists essentially of a radioactive isotope and wherein said low voltage source is mounted within a housing member which in turn is hingedly mounted at one end of said beam forming means, said housing member being apertured in one side to provide a beam forming channel for said low voltage source and being rotatable into said beam forming means in response to operation of said actuating mechanism to project a low voltage X-ray beam along said predetermined axis.

6. The therapeutic X-ray apparatus defined in claim 2 wherein said first X-ray source consists essentially of a radioactive isotope.

7. The therapeutic X-ray apparatus defined in claim 2 wherein said first X-ray source comprises an electronic X-ray machine including an X-ray tube.

8. A therapeutic X-ray apparatus for treating a predetermined area within an object with high voltage therapeutic X-rays, said apparatus comprising: a first radioactive source of relatively high energy X-rays; a shielding member surrounding said first source, said shielding member having a substantially conically shaped bore in one side thereof communicating between said first source and the exterior of said member, said bore being operable as a beam forming channel for channeling high voltage X-rays in a beam whose axis is coincident with the axis of said bore; shutter means normally positioned within said bore for blocking irradiation therethrough; means coupled to said shutter means and responsive to an input signal for withdrawing said shutter means from said bore; a second radioactive source of relatively low energy X-rays, said second source being movable from a normal position to an operating position intercepted by the axis of said bore; shielding means for shielding said second source in its normal position; and means operable to move said second source to its operating position whereby said second source projects a low energy X-ray beam in line with the axis of said bore to enable the radiographic determination of the position of the axis relative to an object to be treated.

9. The therapeutic X-ray apparatus defined in claim 8 wherein said shielding means for shielding said second source is connected to said shielding member which surrounds said first source.

10. The therapeutic X-ray apparatus defined in claim 8 wherein said shielding means for shielding said second source comprises a cavity formed in the surface of said conically shaped bore in said shielding member, and wherein said means operable to move said second source to its operating position comprises an axially movable pushrod coupled to said second source.

11. The method of aligning the axis of a therapeutic X-ray beam with an object to be irradiated, said method comprising the steps of irradiating the object with a low voltage X-ray beam whose axis coincides with that of the therapeutic beam, radiographically observing the position of the object relative to said axis, moving the object relative to the axis until the object is intercepted by the axis, and irradiating the object with the therapeutic X-ray beam.

12. The method of determining radiographically the internal position of an object to be irradiated relative to the axis of a therapeutic X-ray beam, said method comprising the use of a low energy radioactive source for first irradiating the object with a low energy X-ray beam whose axis coincides with the axis of the therapeutic beam.

13. The method of aligning the beam axis of a therapeutic X-ray machine with a particular area within a patient to be treated, said method comprising the steps of irradiating the patient including the particular area with a low energy X-ray beam from a point on the beam axis of the therapeutic machine, radiographically observing the positional error between the particular area and the beam axis, and moving the patient relative to the therapeutic Y-ray machine until the particular area is intercepted by the beam axis.

14. The method defined in claim 13 which includes the additional steps of masking 01f the area adjacent the particular area within the patient to be treated, and irradiating the particular area with the therapeutic X-ray beam.

References Cited in the file of this patent UNITED STATES PATENTS 1,976,179 Mannl Oct. 9, 1934 2,486,503 Stephens Nov. 1, 1949 2,614,224 Wright Oct. 14, 1952 2,675,479 Stewart et al. Apr. 13, 1954 2,730,566 Bartow et al Ian. 10, 1956

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