WO1995009563A1

WO1995009563A1 - Method for increasing nuclear magnetic resonance signals in living biological tissue

Info

Publication number: WO1995009563A1
Application number: PCT/US1993/009401
Authority: WO
Inventors: Arnon Krongrad
Original assignee: Arnon Krongrad
Priority date: 1993-10-04
Filing date: 1993-10-04
Publication date: 1995-04-13
Also published as: AU5169593A

Abstract

A method of enhancing a magnetic resonance signal comprising the steps of administering a quantity of a selected magnetic isotope to a living biological tissue at a concentration greater than the naturally occurring concentration of such isotope and detecting magnetic resonance signal from the administered magnetic isotope in the living biological tissue.

Description

METHOD FOR INCREASING NUCLEAR MAGNETIC

RESONANCE SIGNALS IN LIVING

BIOLOGICAL TISSUE

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to nuclear magnetic resonance (NMR) signal detection in living biological tissue. It relates specifically a method of increasing detectable signals from the nucleus of magnetic atoms for the purpose of analysis of detected spectra and images generated by such signals and a method of applying the above in the study of living biological tissue. For purposes of this application, "living biological tissue" as used herein shall mean normal and abnormal human and non-human biology, in both whole organisms (for example, human patients), living biological specimens or tissue from whole organisms (for example body fluids or biopsy specimens), or living biological specimens or tissue separate from the organism of origin (for example cell or organ culture).

BACKGROUND OF THE INVENTION Living biological metabolism has traditionally been studied by chemical analysis of tissue samples removed from living tissue or organism. In the process, the tissue examined loses viability in its original form and function.

Developments in radiography during this century have led to analysis of metabolic activity based on the external application of ionizing radiation. In this approach, living tissue exhibits characteristic attenuation of the energy applied. Attenuation differences between adjacent tissues can be reflected by different exposure intensities of film. Alternative approaches include internal application of ionizing radiation, typically by injection of radioisotopes into the circulation, with image production resulting from anatomic distribution and concentration of radioactivity. Both approaches have been prevalent in medicine since early this century.

In the mid-1940' s, the physical phenomenon of nuclear magnetism was discovered. Initially, the phenomenon was used to study chemical constructs in relatively pure forms, with the most actively studied isotope being ^αH (Proton). Toward the 1960's, the lessons of nuclear magnetic spectroscopy were increasingly applied to complex chemical compositions, such as living biological macromolecules, and ultimately living biological tissues, such as cell water. The field expanded to include medically relevant applications when, in 1971, R. Damadian reported in Science (171:1151-53, 1971) his ability to detect tumors by measurement of different proton resonance in cell water derived from tumors.

During the years since 1971, study of living biological magnetic resonance has been used to create both numerical representation of isotopes (Magnetic Resonance Spectroscopy; MRS) as well as graphic images of their location and metabolic characteristics within living tissue. The latter technology has been adapted by the world of medicine and applied in a manner known as Magnetic Resonance Imaging (MRI). MRI has been found to offer advantages over other diagnostic modalities in selected cases, such as the diagnosis of pheochromocytoma and diseases of the central nervous system. MRI is generally considered harmless at current configurations because of the low intensity magnetic radiation utilized to cause the nuclei to emit a resonance signal. Despite this attribute, it has yet to supplant Computerized Axial Tomography (CAT) scanning, which detects radioactive emissions rather than magnetic resonance signals to give generally similar anatomical images, but whose application is limited by the risks of ionizing radiation and the frequent need for adjunctive toxic contrast media. The reasons MRI has not predominated in medicine undoubtedly include cost, but also the absence of multiple clearly demonstrable advantages over other existing techniques, such as CAT scanning. Improvements in the diagnostic capabilities of MRI would be welcome in the study of biology in general, but especially in the world of studying living biological tissue and more especially, in medicine, where concern for human health limits the use of other diagnostic methods such as cat scanning which may have an unacceptably high risk/benefit ratio for the particular diagnostic procedure.

The types of atoms having naturally occurring magnetic isotopes is large but is not unlimited.

Further, the relative proportion of any specific magnetic isotope of a given atom is frequently very low (Ex., C. S. Springer, Jr. "Measurement of Metal Cation Compartmentalization In Tissue By High-Resolution Metal Cation NMR" , Ann Rev Biophys Chem 16:375-99, 1987). Thus, the application of medical MRI has focused on the most abundant magnetic nucleus in living biological tissues, *H, because of its prevalence in nature and because of the relative scarcity of other magnetic isotopes Ex., R. L. Nunnally and PR Antich, "New Directions in Medical Imaging of Cancer" (Cancer 67:1271- 1277, 1991). Attempts have also been made to utilize other isotopes naturally occurring in living biology with magnetic nuclei, such as ¹³C, ¹⁹F, ²³Na, and ³¹P. As for example disclosed in U.S. Patent No. 4,779,619 where ²³Na is used for brain function analysis. Also, for example, H. Kantor et al, "In Vivo ³¹P Nuclear Magnetic Resonance Measurements in Canine Heart.Using a Catheter-Coil" (Circ Res 55:261-266, 1984), disclose the use of ³¹P for heart function analysis in canines; and I. R. Francis et al, "Malignant Hepatic Tumors: P-31 MR Spectroscopy with One- dimensional Chemical Shift Imaging" (Radiology 180:341- 344 1991), disclose use of naturally occurring ³¹P for liver tumor detection.

In an effort to improve resonance detection, technical innovations have been applied to MRI machinery. Many imaging modalities have been introduced since Lauterbur introduced the concept of "zeugmatography" . Hardware configuration has evolved to include a variety of magnets to alternatively establish and remove magnetic fields so nuclear magnetic resonance is generated. Advances in antenna design for detecting the resonance frequencies of various nuclei include surface applied or internally applied coils, with easily interchangeable frequency sensitivities. For example, U.S. Patent No. 4,672,972 discloses a solid state NMR probe which both receives a resonance on or from proximate tissue and modulates a magnetic field in the proximity of the tissue from which resonance signal is detected.

Attempts have also been made to alter the physical environment within the tissue. One method causes induction of normal metabolic cascades known to alter the spin states of the magnetic nucleus. Thus, for example, fructose causes reduction of MRI-detectable inorganic liver phosphate, and allows a dynamic assessment of liver function through ³¹P spectroscopy (F. Terrier et al, Radiology 171:557-563 1989).

Other approaches, as disclosed in U. S. Patent Nos. 4,532,217; 4,731,239; 4,735,796; 4,849,210; and 4,985,233 include the use or administration of paramagnetic, diamagnetic, and ferromagnetic contrast enhancement particles or agents, which agents may or may not be metabolized by the tissue; but, which agents normally have little if anything to do with the metabolic activity of the tissue in question. Essentially a contrast between areas in which signals are generated by the isotope and those where they are not generated is enhanced to create a greater "shadow" for imaging purposes. Such contrast agents, for example, may cause reduction of relaxation times of an endogenous (i.e. unadministered) nucleus under study and improve signal/noise ratios. Alternatively, as for example with metabolizable ferromagnetic particles such as iron dextran particles, the contrast agents may focus and concentrate the magnetic field. Contrast agents, such a those described in the patents listed above, specifically do not contain MRI-sensitive nuclei. By definition, such contrast enhancers are not detected directly on images and spectra; they are not generating the resonance frequency signal, but rather they act to alter the magnetic environment of an endogenous isotope under analysis.

To a limited extent, chemists have previously applied increased concentrations of various magnetic isotopes to proteins and enzymes and other non-living macromolecules for NMR studies. Pharmacologist have even used naturally abundant, i.e. unenriched, magnetic isotopes to label drugs for the study of drug metabolism and distribution, in living organisms. There are recommendations in the literature, however, to avoid the use of most magnetic isotopes as their concentrations are low enough as to render them useless under current configurations and applications (Ex., Crooks et al., "Tomography of hydrogen with. nuclear magnetic resonance (NMR) and the potential for imaging other body constituents" SPIE 206:120-128, 1979). In part because of the emphasis on NMR studies of naturally abundant magnetic isotopes and in part because of such recommendations.most magnetic isotopes have been ignored; exogenous administration of an element with concentrated magnetic isotopes for the study of the administered element in living biological tissue has not been discovered.

It has also been recognized, as with radioactive ions, that magnetic isotopes could be used as labels chemically bonded to larger non-living molecules for pharmacalogical studies of such molecules. For example, the use of solid state ¹³C NRM, to study characterization of covalent hapten-protein conjugates was disclosed in J. R. Garbow, et al., "Characterization of Covalent Protein Conjugates Using Solid State ¹³C NMR Spectroscopy," Biochemistry 30, 7057-7062 (1991). Selective hapten ¹³C isotope enrichment was postulated for direct observation of nucleophilic protein heteroatom displacement at the - position of α-halocarbonyl substrates. A chemical labeling modality using ¹³C was also explored in Unkefer, C.J., J. Clin. Pharmcol. 26:452-8 (1986). The article discusses the use of stable isotopic ¹³C labeling to study metabolic regulation of labeled metabolites and considerations for optimal ¹³C-labeling pattern for direct observation of the metabolites in vivo. Simultaneous ¹³C and ³¹P NMR was suggested as promising. However, ³¹P NMR (which ³¹P has 100% natural abundance) was beyond the scope of the article. There was no suggestion or teaching of use for any magnetic isotope, with less than 100% natural concentration, other than as a label on macromolecules of interest. The study of an isotope, which is of interest as it is absorbed in living biological tissue was not suggested. The ¹³C is of interest as it is absorbed in living biological tissue. The ¹³C was chemically bonded and does not readily form a salt solution from which it might be absorbed.

The absorption of various elemental atoms by various living biological tissues has been observed.

These observations have not previously led to the concept of the study of elemental atom absorption in living biological tissue with MRI where the magnetic isotope of the atom naturally occurs at significantly less than 100%. The low natural concentration of many magnetic isotopes would result in poor resolution for specific magnetic isotopes of atoms, the isotopes of which atoms is of interest for the study. Prior to the present invention, despite the need for better testing modalities, increasing the concentration of non- radioactive magnetic isotopes for purposes of studying the absorption of such isotopes in living biological tissue was not disclosed, suggested or implemented. SUMMARY OF THE INVENTION The invention comprises a method for detection, spectra analysis and imaging the concentration and characteristics of magnetic nuclei in living biological tissue as defined above. Magnetic isotopes are administered to living biological tissue in a chemical form in which it is bioavailable and at concentration levels greater than naturally occurring concentration levels, i.e. at which the magnetic isotope has been enriched. Typically, this means that a magnetic isotope of an element of interest is administered in a form from which it is available for absorption, as for example, from a salt solution. Such a salt solution is formed of magnetic isotopes of an element with greater concentrations of magnetic isotopes than naturally occur for such elements. The magnetic isotope administered is selected from isotopes of elements which are of interest as the element is absorbed and metabolized by the living biological tissue. The tissue is allowed to absorb and metabolize the isotope. The tissue is then, for example, subjected to a magnetic field, such as with a magnetic pulse, which will orient all nuclei with nonzero spin and generate a net magnetic moment M, aligned parallel to the field, within the tissue. When the excitation magnetic pulse is interrupted, the nuclei return to their original equilibrium with characteristic resonance. In the process the nuclei emit resonant radiation in the radio frequency region of the electromagnetic spectrum, which resonant frequency is characteristic of the isotope under study. This radiation is detected and converted into spectra or images which reflect the concentration and chemical characteristics of the nuclei. These spectra or images are then used to study the normal and abnormal physiology of the isotope in the living biological tissue and following this to detect abnormal biology. In the case of human medical studies, early detection of abnormalities and disease will hopefully lead to prevention and early cure. The invention provides a new method for studying normal biology and detecting aberrations in that biology. It relies on some of the existing MRS and MRI technology, but differs significantly in its method of signal enhancement. In previously described signal enhancement, "contrast" agents are not directly measurable and are not the source of signal. In contradistinction, this invention describes the augmentation of signal by increasing the concentration of physiologically relevant magnetic nuclei by exogenous. administration. The administered nuclei are thus very directly and advantageously the source of signal. It is the elemental isotope under study which emits the magnetic resonant signal which is detected.

This inventive concept and method where the magnetic resonant signal itself is increased has many advantages over prior methodology both with and without the use of signal enhancement though the application of contrast agent particles. The previous focus on ferromagnetic, paramagnetic and diamagnetic enhancers is further evidence of the novelty of the methodology of directly increasing the quantity of resonance signal through the application of increased concentrations of magnetic isotopes to study absorption or metabolization of the signal emitting isotope in living biological tissue. Such a technique has long been needed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For the purpose of this disclosure the term "living biological tissue" refers to subcellular, monocellular and multicellular reproducing organisms including but not limited to vertebrates, invertebrates, plants, bacteria, viruses and yeast. This further includes fluids, cells, or organs as specimens, biopsies, or independent cultures of such organisms.

Advantageously, according to the present invention, relevant magnetic isotopes can now be identified for a multitude of specific applications of the method according to the present invention. Many magnetic and nonmagnetic nuclei are described by the scientific community, and in .particular in chemistry and physics literature. Compilations of spin characteristics, magnetic and quadrupole moments, as well as magnetic resonance frequencies are published.

Distribution of various atoms in certain living biological tissues are described in the chemistry, biology, and medicine literature. Some such descriptions include the distribution of common atoms, for example the ubiquitous H, and of more rare atoms, for example Se. From descriptions of distributions of various atoms and the magnetic characteristics of such atoms, those which are relevant or useful, according to the present invention for a given study of a particular living biological tissue can now be selected. Once an atom of interest has been selected as one with magnetic isotopes with a natural abundance significantly less than 100%, as might be identified by a literature search, it can be administered to living biological tissue in a form in which it is absorbable by the living tissue. Scientific experimentation may further lead to identification of magnetic isotopes useful according to the present invention, which are not identifiable through a literature search.

Many relevant or useful magnetic isotopes predominate in nature, and some, for example H, are readily available with high naturally occurring concentrations for study as natural components in living biological tissue. The signal of magnetic isotopes naturally occurring in 100% concentrations will not be benefitted directly by the present method. However, such atoms are not always the ones which will be relevant or useful for a particular living biological tissue or for a specific metabolization, abnormality, analysis, or study with such living biological tissue. The signal from any isotope naturally occurring which is not significantly less than 100% concentration (Ex., ¹⁴N [99.6%], ³¹P [100%] and ³⁹K [93.1%] will not be significantly enhanced by increasing the concentration according to the present method. Magnetic isotopes which may be particularly relevant for a given living biological tissue investigation represent minor components of naturally occurring atoms (Ex., ^€Li [7.4%], ²⁵Mg[10%], ³⁵Cje[75.5%], ⁴¹K [7%], ⁵⁰V[0.24%], ⁵³Cr [9.6%], ⁵⁷Fe [2%], ⁶³Cu [69%], ⁶⁵Cu [31%], ⁶⁵Ga [40%], ⁶⁷Zn [4%], ⁶⁹Ga [40%], ⁷⁹Br [51%], ⁸¹Br [49%], ⁸⁷Sr [11%], ^luCd [13%], and ¹¹³Cd [12%]) and could each be significantly enriched by exogenous administration. Significant enrichment is considered to be available when the natural abundance of a magnetic isotope is about 80% or below of naturally occurring atoms. Some isotopes need not be administered at 100% concentrations in order to obtain a significant increase in the emitted magnetic signal. For example, a potential signal increase of 20% or more is considered significant. It is also noted that some of the elements have separate magnetic isotopes which total 100%. Nevertheless, the resonant signal from separate isotopes may be sufficiently distinct so that increasing the concentration of a particular one of the magnetic isotopes can still result in greater specific signal generation according to the invention. Many such potentially relevant isotopes can be readily purchased from government and commercial sources.

One of the aspects of the present inventive method is the administration of relevant magnetic isotopes to living biological tissue. For the purpose of this invention, "administration" means exposing the living biological tissue under study to the relevant isotope such that the living biological tissue will absorb and process the relevant isotope.to meet its own living biological directives. Relevant isotopes may have to be chemically processed so as to render them more accessible to the living biological tissue under study, and so as to minimize untoward effects of the co-constituents in the chemical formulation. For example ⁶⁷Zn is available from the US Department of Energy as zinc oxide, which cannot be easily absorbed, but may be easily converted into a more soluble zinc chloride salt which is absorbable in biological tissue for purposes of this invention.

Administration may be done by a variety of means, depending on the living biological tissue and its milieu. In the case of cell or organ culture, administration could consist of bathing the cells or organ in medium containing solutions of relevant isotope,¹¹³CdCl₂ for example. In the case of whole organisms, it could consist of exposing the organism to the relevant isotope by a variety of methods including but not limited to: 1) transdermal (skin and mucous membranes [example, nasal mucosa]) or enteric contact (oral, ano-rectal, or nasogastric) ; 2) intradermal, subcutaneous, intramuscular, intravenous, intra-arterial, intrathecal, intravisceral, or intraperitoneal injection; or 3) transurethral and/or intravesical contact.

Tissue will be prepared for NMR analysis according to the specifications of the analytical tools. In the case of cells, organs, biopsy specimens, or body fluids they may be purified from living biological tissue and assayed directly or in solution. In the case of whole organisms, including man, the relevant isotope would be studied within the host organism, in a manner similar to that currently use in medicine. For example, external or internal antenna or probes can be passed in proximity to the area of interest. A magnetic field can be applied and released. The frequency, phase angle, duration times and interrupt times can be adjusted for the study based on considerations such as the isotope which generates the signal, tissue structure, enhancing agents, if any also used and other normally or newly considered factors of the study to be. conducted. The magnetic resonance can be spectrographically detected, mapped, graphed imaged or otherwise studied by techniques now known or later developed.

Examples of the general application of this method include the study of cancer or other diseases in animals including humans.

Examples of the specific application of the present method include, but are not limited to the following:

Example 1:

⁶⁷Zn IN THE CLINICAL ANALYSIS OF HUMAN PROSTATE CANCER

A study of prostate using ⁶⁷Zn which has a low natural abundance of 4%. However, Zn plays an important role for the functions of the prostate gland. Cancerous conditions as well as other abnormalities may be detected, or more accurately staged at early stages of the cancer or other disease.

Zinc is an integral component of the human diet. It is widely distributed in the body following intestinal absorption, and is known to be essential for the function of a vast array of physiological functions. Despite its wide distribution, zinc concentrations vary dramatically from organ to organ, with particularly high concentrations in the prostate.

Prostatic zinc has been extensively studied in both humans and animals. It appears to be both an integral element in intracellular metabolism and an integral element in prostatic secretions contributing to ejaculate. Regardless of its normal role in physiology and reproduction, prostatic zinc concentration appears to vary as a function of disease: prostatitis, benign prostatic hyperplasia, and prostate cancer. Previous studies are consistent with this determination, and it appears that there may even be a role of altered zinc levels as an indicator of imminent malignant transformation. It is believed by Applicant that not only is zinc concentration altered in disease, but that cellular disposition of zinc, including its molecular associates, may be altered. These factors will alter the magnetic resonance of the prostatic zinc nucleus.

Prostate cancer remains one of the leading causes of cancer death in the United States. Many issues in its diagnosis and management remain unresolved. One of these issues is the problem of staging. For example, a patient may have cancer diagnosed incidently following surgery for benign hyperplasia. Further treatment options for this so-called stage A tumor are then dictated by an analysis of residual tumor, and may range from observation to radical surgery. Unfortunately, current staging procedures are highly inaccurate in this setting, given the fact that no tumor was diagnosed prior to the first operation. An accurate staging method would potentially obviate the need for further surgery in some patients, confirm the need in others, or suggest metastatic disease and the need for systemic therapy in others. Such a method would potentially be useful in screening and directing biopsies. Traditional ^αH MRI has been used in imaging the prostate, but while offering perhaps greater resolution than CAT scanning, is of no real use in the problem described. This is altered by the present invention.

Zinc metabolism has been extensively studied in the human, in particular in regards to its bioavailability.

Stable isotopes, ⁶⁷Zn and ⁷⁰Zn, as well as radioactive ⁶⁵Zn have been used. Zinc has been given orally as well as intravenously, and some of the kinetics of its distribution and elimination are well worked out. Zinc has been found to be rapidly absorbed by the prostate. In accordance with the present invention, nonradioactive magnetic isotope ⁶⁷Zn in increased concentrations (i.e. greater than the 4% abundance level of ⁶ Zn which naturally occurs) is administered to a patient with recently diagnosed prostate cancer. Before, during and/or following administration, the patient undergoes MRI utilizing probes configured to measure ⁶⁷Zn resonance. These probes are preferably mounted within endorectal catheters for maximization of resolution, as has been described in the case of ^*H prostatic MRI.

Following conversion to anatomical images, determinations of focal altered zinc concentrations are made, with confirmation of pathology by aspiration cytology or biopsy as indicated. Example 2:

⁶⁷Zn IN THE CLINICAL ANALYSIS OF HUMAN PANCREAS TUMORS

In a study of the pancreas using ⁶⁷Zn which has a low natural abundance of 4%, however, Zn lays an important role for functions of the pancreas gland. Cancerous conditions as well as other abnormalities may be detected, or more accurately staged at early stages of the cancer or other disease. Zinc is an integral component of the human diet.

It is widely distributed in the body following intestinal absorption, and is known to be essential for the function of a vast array of physiological functions. Despite its wide distribution, zinc concentrations vary dramatically from organ to organ, with particularly high concentrations in the pancreas.

Pancreatic zinc has been studied in both humans and animals. It appears to be both an integral element in intracellular metabolism and an integral element in secretions. Pancreatic cancer remains a difficult therapeutic challenge. Many issues in its diagnosis and management remain unresolved.

Zinc metabolism has been extensively studied in the human, particular in regards to its bioavailability. Several zinc isotopes have been used for this research, primarily the radioactive isotope ⁶⁵Zn. Zinc has been given orally as well as intravenously, and some of the kinetics of its distribution and elimination are well worked out. It has been concluded from radioactivity scanning that zinc may be rapidly absorbed by the pancreas, for example.

In accordance with the present invention, nonradioactive magnetic isotope ⁶⁷Zn in increased concentrations (i.e. greater than the 4% abundance level of ⁶⁷Zn which naturally occurs) is administered to a patient with a suspected tumor. Before, during and/or following administration, the patient undergoes MRI utilizing probes configured to measure ⁶⁷Zn resonance.

These probes are mounted for maximization of resolution.

Following conversion to anatomical images, determinations of focal altered zinc concentrations are made, with confirmation of pathology by aspiration cytology or biopsy as indicated.

Example 3:

⁴³Ca , ⁵⁰V, "Ga , ⁸⁷Sr , ⁹¹Sr , ¹⁸⁵Re , ^{1 7}Sm, ¹⁴⁹Sm IN THE CLINICAL ANALYSIS OF HUMAN BONE

To study bone, the investigator would choose an isotope from the following list of isotopes, in which the natural abundance is represented in brackets: ⁴³Ca [0.1%], ⁵⁰V [.24%], ⁶⁹Ga [60%], ⁸⁷Sr [70%], ⁹¹Sr [11%], ¹⁸⁵Re [37%], ¹⁴⁷Sm [15%] and ¹⁹Sm [14%], which could be absorbed by living biological bone tissue. The isotopes are administered at greater than natural concentration levels and are absorbed by bone. The increased concentration of magnetic isotopes may be more easily detected in the bone by MRI methodology. Following or otherwise detecting the magnetic resonance signals emitted, the administered isotope can be used to study the biological state of the target organ (bone) . One might choose the ⁴³Ca isotope as the most physiological, or one might, depending on specific utility, choose another isotope.

According to the present invention, the isotope chosen would be administered at a concentration level greater than the abundance of the isotope in nature. Preferably, the concentration would be increased by about 20% or more over the natural abundance in nature. More preferably, an increase of 50% or more, such as with administration with isotope concentration levels approaching 100%, would further enhance the magnetic resonance signal. Example 4:

⁶Li, ²⁵Mg, ³⁵ce, ⁵⁰V, ^lιαCd, ¹¹³Cd IN THE CLINICAL ANALYSIS OF HUMAN KIDNEY TISSUE

To study the kidney, the investigator would choose isotopes which could be absorbed by the living kidney tissue from among the following magnetic isotopes which have the naturally occurring abundance, as indicated in brackets: ⁶Li [7.4%], ²⁵Mg [10%], ³⁵C£ [75.5%], ⁵⁰V [0.24%], ^nιCd [13%], and ¹¹³Cd [12%]. Each of these isotopes can be concentrated. in the kidney. Following signals emitted from the enriched administered isotope can be used to study the biological state of the target organ (kidney) . One would preferably administer concentrations which are about 20% or more greater than the concentrations. Advantageously where the naturally occurring concentration is sufficiently low, administering concentrations of about 50% or greater than the naturally occurring concentration, as for example, administration of concentrations approaching 100%, will further beneficially generate an enhanced emitted signal. Example 5:

⁵⁷Fe, ⁶³Cu, ⁶⁵Cu IN THE CLINICAL ANALYSIS OF THE HUMAN LIVER

To study the human liver, the investigator would choose isotopes which could be absorbed by living biological liver tissue from the following magnetic isotopes having the naturally occurring abundance indicated in brackets: Fe [2%], Cd [13%], ^U3Cd [12%]. Each of these is concentrated in the pancreas and each is a magnetic isotope from which a signal may be detected by MRI methodology. Following or otherwise detecting the signals generated or emitted from the enriched administered isotope can be useful to study the biological state of the pancreas. Preferably, concentrations of about 20% or more greater than the naturally occurring concentration will produce a significant signal enhancement. More preferably, concentrations of 50% or more greater than the naturally occurring concentration, as with administering normally low concentration isotopes at concentration levels approaching 100%, will further enhance the emitted signal for improved MRI results. Example 6: ^ιnCd and ^U3Cd IN THE CLINICAL ANALYSIS OF TESTICULAR TISSUE

To study testicular tissue, an investigator would choose magnetic isotopes of cadmium, i.e., ^ι Cd [13%] or ¹¹³Cd [12%] as these are selectively concentrated in this organ. Following or otherwise detecting the emitted signals using MRI methodology of an isotope administered at enriched concentrations, and preferably concentrations of 20% or more greater than the naturally occurring concentration can be used to study the biological state of the target organ. Example 7:

³C£ IN THE CLINICAL ANALYSIS OF THE INTESTINES

To study the intestines, an investigator would choose ³⁵CJ2 to be administered orally or intravenously through trace distribution in the intestines and to interpret blood flow in these organs. Administration of ³⁵C£ at approximately 100% concentration will significantly increase a magnetic resonance signal emitted by 20% or more over naturally occurring ³⁵C£ which has a natural abundance of 75.5%. Example 8:

²⁵Mg IN THE CLINICAL ANALYSIS OF BLOOD VESSELS ⁵Mg could be administered orally or intravenously to trace the distribution in the blood vessels and potentially to interpret blood flow in the blood vessels. Administering concentrations of ²⁵Mg of about 20% or greater than the naturally occurring abundance of 10% can significantly increase the magnetic resonance signal emitted from the Mg administered. Example 9:

⁵⁷Fe IN THE CLINICAL ANALYSIS OF BONE MARROW To study bone marrow, the investigator would choose

⁵⁷Fe which is a magnetic isotope having a 2% naturally occurring concentration among elemental Fe. Administering enriched concentrations, preferably concentrations of about 20% or greater than the naturally occurring concentration will facilitate the study of bone marrow using MRI methodology by increasing the detectable signal emitted from the increased concentration of magnetic isotope ⁵⁷Fe.

Other alterations and modifications of the invention will likewise become apparent to those of ordinary skill in the art upon reading the present disclosure, and it is intended that the scope of the invention disclosed herein be limited only by the broadest interpretation of the appended claims to which the inventor is legally entitled.

Claims

CLAIMS:WHAT IS CLAIMED IS:

1. A method of increasing a magnetic resonance signal comprising the steps of:

(a) administering to a living biological tissue a quantity of a selected magnetic isotope to be studied in the living biological tissue at a concentration greater than the naturally occurring concentration of such isotope; and

(b) detecting magnetic resonance signal from the administered magnetic isotope in the living biological tissue.

2. A method of increasing a magnetic resonance signal as in claim 1 further comprising the step of allowing at least a portion of the quantity of administered magnetic isotope to be absorbed by the living biological tissue before detecting the magnetic resonance signal.

3. The method of claim 2 further comprising the step of selecting a magnetic isotope to be administered which has an acceptably short absorption time to allow effective clinical testing using NMR technology.

4. The method of claim 1 wherein the step of detecting the magnetic resonance signal comprises the steps of

(a) subjecting said administered magnetic isotope in the living biological tissue to a magnetic field;

(b) removing the magnetic field;

(c) detecting a characteristic resonance radiation emitted from the administered magnetic isotope as the magnetic field is removed; and (d) analyzing the detected resonant radiation emitted from the administered magnetic isotope with spectra, images, or other forms of data representation.

5. A method of enhancing a magnetic resonance signal as in claim 1 further comprising the step of selecting a magnetic isotope from among magnetic isotopes which are absorbable by the living biological tissue to which it is applied.

6. A method of increasing a magnetic resonance signal as in claim 1 further comprising the step of administering a magnetic isotope at a concentration about 20% or more greater than the. naturally occurring concentration of such magnetic isotope.

7. The method of claim 1 further comprising the step of selecting a magnetic isotope from among isotopes which have a naturally occurring abundance of less than about 80%.

8. The method of claim 7 wherein the magnetic isotope is selected from among the following isotopes ^βLi , ²⁵Mg ; ³⁵C-β ; ³Ca ; ⁴¹K ; ⁵⁰V; ⁵⁷Fe ; ⁶³Cu ; ⁶⁵Cu ; ⁶⁷Zn ; ⁶⁹Ga ;

⁷¹Ga ; ⁷⁹Br ; ⁸¹Br ; ⁸⁷Sr ; ⁸⁹Sr ; ^ιCd and ¹¹³Cd .

9. The method of claim 7 wherein the living biological tissue to be analyzed is human kidney tissue and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting a specific magnetic isotope from a group comprising ⁶Li, ²⁵Mg, ³⁵C£, ⁵⁰V, ^ι Cd and ¹¹³Cd.

10. The method of claim 7 wherein the living biological tissue to be analyzed is bone tissue and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting a specific magnetic isotope from a group comprising ⁴³Ca, ^S0V, ⁶⁹Ga, ⁷¹Ga, ⁸⁷Sr and ⁹¹Sr.

11. The method of claim 7 wherein the living biological tissue to be analyzed is human liver tissue and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting a specific magnetic isotope from a group comprising ⁵⁷Fe, ⁶³Cu and ⁶⁵Cu.

12. The method of claim 7 wherein the living biological tissue to be analyzed is human testicular tissue and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting a specific magnetic isotope from a group comprising ^ι Cd and ¹¹³Cd.

13. The method of claim 7 wherein the living biological tissue to be analyzed is human brain tissue and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting the specific magnetic isotope, ⁶Li.

14. The method of claim 7 wherein the living biological tissue to be analyzed is human blood vessels and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting the specific magnetic isotope, ²⁵Mg.

15. The method of claim 7 wherein the living biological tissue to be analyzed is human intestines and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting the specific magnetic isotope,

³⁵ce.

16. The method of claim 7 wherein the living biological tissue to be analyzed is human bone marrow and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting the specific magnetic isotope, ⁵⁷Fe.

17. The method of claim 7 wherein the living biological tissue to be analyzed is human pancreas and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting a specific magnetic isotope from a group comprising ^δ7Zn, ^mCd and ¹¹³Cd.

18. The method of claim 7 wherein the living biological tissue to be analyzed is human prostate and the step of selecting a magnetic isotope to be administered to the living biological tissue comprises the step of selecting the specific magnetic isotope, ⁶⁷Zn.

19. A method as in claim 1 further comprising the step of administering the magnetic isotope to living humans.

20. The method of claim 1 wherein said step of administering said selected magnetic isotope in an absorbable form comprises the steps of:

(a) producing a salt solution with a concentration of said selected magnetic isotope which is greater than the naturally occurring concentration of said selected magnetic isotope; and

(b) exposing the living biological tissue under study to salt solution of said magnetic isotope so that said biological tissue will absorb and process said magnetic isotope of interest to meet its own living biological directives.

21. A method of enhancing a magnetic resonance signal in a living biological tissue comprising the steps of:

(a) selecting a magnetic isotope of an element which is of interest in diagnosis of disease in a living biological tissue;

(b) administering to said living biological tissue a quantity of said selected magnetic isotope of an element in a form in which said selected magnetic isotope is absorbable by said living biological tissue, which administered quantity of selected magnetic isotope has a concentration which is about 20% or more greater than the concentration of said selected magnetic isotope naturally occurring outside of said living biological tissue; and

(c) detecting magnetic resonance signal which is emitted from said administered magnetic isotope in said living biological tissue.

22. A method of enhancing a magnetic resonance signal as in claim 21 further comprising the step of allowing at least a portion of the quantity of administered isotope of an element to be absorbed by the living biological tissue before detecting the magnetic resonance signal.

23. The method of claim 21 wherein the magnetic isotope is selected from among the following isotopes

⁶Li , ²⁵Mg; ³⁵CJ2 ; ³Ca; ⁴¹K , ⁵⁰V, ⁵⁷Fe , ⁶³Cu , ⁶⁵Cu , ⁶⁷Zn , ⁶⁹Ga, ⁷¹Ga , ⁷⁹Br , ⁸¹Br , ⁸⁷Sr , ⁸⁹Sr , ^ι Cd and ¹¹³Cd . ^•

24. The method of claim 21 wherein said step of administering said selected magnetic isotope in an absorbable form comprises the steps of:

(a) producing a salt solution with a concentration of said selected magnetic isotope which is greater than the naturally occurring concentration of said selected magnetic isotope; and (b) exposing the living biological tissue under study to salt solution of said magnetic isotope so that said biological tissue will absorb and process said magnetic isotope of interest to meet its own living biological directives.

25. A method for magnetic resonance imaging (MRI) of a living biological tissue comprising prior to the MRI of a living biological tissue administering a magnetic isotope in a salt solution from which said administered magnetic isotope can be absorbed by the biological tissue and which administered magnetic isotope is present in said salt solution at a higher than normal concentration so that an enhanced signal for the MRI image is generated by said administered magnetic isotopes.

26. A method of disease detection in humans comprising the steps of: (a) administering to living human tissue a quantity of Li having a concentration of ⁶Li greater than the abundance of ⁶Li in naturally occurring Li outside of said living human tissue; (b) allowing said ⁶Li to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

(d) detecting the NMR detection of said living human tissue to standards by which disease can be detected.

27. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Mg having a concentration of ²⁵Mg greater than the abundance of ²⁵Mg naturally occurring Mg outside of said living human tissue;

(b) allowing said ²⁵Mg to be absorbed, assimilated or metabolized by said living human tissue; (c) subjecting said living human tissue to

NMR detection; and

28. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Cϋ having a concentration of ³⁵CJ2 greater than the abundance of ³⁵Ci in naturally occurring C2 outside of said living human tissue;

(b) allowing said ³⁵C£ to be absorbed, assimilated or metabolized by said living human tissue; (c) subjecting said living human tissue to NMR detection; and

29. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Ca having a concentration of ⁴³Ca greater than the abundance of ⁴³Ca in naturally occurring Ca outside of said living human tissue;

(b) allowing said ⁴³Ca to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

30. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of V having a concentration of ⁵⁰V greater than the abundance of ⁵⁰V in naturally occurring V outside of said living human tissue; (b) allowing said ⁵⁰V to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

31. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Fe having a concentration of ⁵⁷Fe greater than the abundance of ⁵⁷Fe in naturally occurring Fe outside of said living human tissue;

(b) allowing said ⁵⁷Fe to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

32. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Cu having a concentration of ⁶³Cu greater than the abundance of ⁶³Cu in naturally occurring Cu outside of said living human tissue; (b) allowing said ⁶³Cu to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

33. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Cu having a concentration of ⁶ Cu greater than the abundance of ⁶⁵Cu in naturally occurring Cu outside of said living human tissue; (b) allowing said ⁶⁵Cu to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and (d) detecting the NMR detection of said living human tissue to standards by which disease can be detected.

34. A method of disease detection in humans comprising the steps of: (a) administering to living human tissue a quantity of Ga having a concentration of ⁶⁹Ga greater than the abundance of ⁶⁹Ga in naturally occurring Ga outside of said living human .tissue;

(b) allowing said ⁶⁹Ga to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

(d) .detecting the NMR detection of said living human tissue to standards by which disease can be detected.

35. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Ga having a concentration of ⁷¹Ga greater than the abundance of ¹Ga in naturally occurring Ga outside of said living human tissue;

(b) allowing said ⁷¹Ga to be absorbed, assimilated or metabolized by said living human tissue;

36. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Sr having a concentration of ⁸⁷Sr greater than the abundance of ⁸⁷Sr in naturally occurring Sr outside of said living human tissue; (b) allowing said ⁸⁷Sr to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

37. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Sr having a concentration of ⁹¹Sr greater than the abundance of ⁹¹Sr in naturally occurring Sr outside of said living human tissue;

(b) allowing said ⁹¹Sr to be absorbed, assimilated or metabolized by said living human tissue; (c) subjecting said living human tissue to

NMR detection; and

38. A method of disease detection in humans comprising the steps of: (a) administering to living human tissue a quantity of Cd having a concentration of ^ιnCd greater than the abundance of ^ulCd in naturally occurring Cd outside of said living human tissue; (b) allowing said ^ι Cd to be absorbed, assimilated or metabolized by said living human tissue;

(c) subjecting said living human tissue to NMR detection; and

39. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Cd having a concentration of ¹¹³Cd greater than the abundance of ¹¹³Cd in naturally occurring Cd outside of said living human tissue;

(b) allowing said ¹¹³Cd to be absorbed, assimilated or metabolized by said living human tissue; (c) subjecting said living human tissue to

NMR detection; and

40. A method of disease detection in humans comprising the steps of:

(a) administering to living human tissue a quantity of Zn having a concentration of ⁶⁷Zn greater than the abundance of ^β7Zn in naturally occurring Zn outside of said living human tissue;

(b) allowing said ⁷Zn to be absorbed, assimilated or metabolized by said living human tissue; (c) subjecting said living human tissue to NMR detection; and