NMR in cancer, XIII: application of the NMR malignancy index to human mammary tumours.

One hundred and nineteen specimens of human mammary tissue taken from 112 individuals, were inspected by pulsed proton magnetic-resonance techniques (at 22.5 MH2). The purpose of the study was to evaluate the diagnostic capabilities of the nuclear magnetic resonance (NMR) technique with regard to the recognition of malignancy. The combination of two NMR parameters (spin lattice (T1) and spin-spin(T2) relaxation times) into a malignancy index produced better than 95% discrimination between the 2 populations of tissue on a case-by-case basis. The mean and standard deviations obtained were 2.002 +/- 0.351 for normal tissue, and 3.137 +/- 0.667 for malignant specimens. The probability that this difference is not significant is considerably less than 0.01. In addition, specimens of fibrocystic disease and fibrous mastopathy had indices of 2.263 +/- 0.503 and 2.151 +/- 0.505 respectively. Both groups yielded P values less than 0.01 when compared to the malignant specimens.     

Nuclear magnetic resonance in cancer, XII: Application of NMR malignancy index to human lung tumours.

Sixty specimens of human lung tissue from 52 individuals were inspected at 22.5 MHz by proton magnetic resonance techniques. The purpose of the study was to evaluate the diagnostic capabilities of the nuclear magnetic resonance (NMR) technique for the diagnosis of malignancy. The combination of two NMR parameters (spin-lattice (T1) and spin-spin (T2) relaxation times) into a malignancy index yielded 3 cases of overlap between the two populations of tissue. The mean and standard deviations obtained were 1.966 +/- 0.262 for normal tissue, and 2.925 +/- 0.864 for malignant specimens. In addition, analysis of the electrolyte and water content of the tissues confirm that factors other than specimen water content influence the relaxation time.     

Diminished aqueous microviscosity of tumors in murine models measured with in vivo radiofrequency electron paramagnetic resonance

Using very low frequency in vivo electron paramagnetic resonance (EPR), we have compared, for the first time, the average microviscosity of the total aqueous compartment of murine fibrosarcomas and that of normal leg tissue in a living animal. EPR spectra from dissolved nitroxide spin probes report the solvent microviscosity. The tumor aqueous microviscosity, 1.8 +/- 0.1 centipoise, was significantly lower than that of the corresponding normal tissue, 2.9 +/- 0.3 centipoise, a difference of 38 +/- 7%. These results confirm the commonly observed increase in the water proton transverse relaxation times (T2) in magnetic resonance imaging of hyperproliferative states, for example, malignancy. The specificity of the localization of the EPR signal indicates a substantial portion of the T2 increase seen in magnetic resonance imaging derives from decreased bulk-water viscosity. The effect of this microviscosity differences may be the basis of several physiological differences between tumors and normal tissues which could confer a growth rate advantage to tumor tissue.     

C-13 NMR spectroscopy of plasma reduces interference of hypertriglyceridemia in the H-1 NMR detection of malignancy. Application in patients with breast lesions

Summary We have previously described the application of water-suppressed proton nuclear magnetic resonance (H-1 NMR) spectroscopy of plasma for detection of malignancy. Subsequently, hypertriglyceridemia has been identified as a source of false positive results. We now describe a confirmatory, adjunctive technique — analysis of the carbon-13 (C-13) NMR spectrum of plasma — which also identifies the presence of malignancy but is not sensitive to the plasma triglyceride level. Blinded plasma samples from 480 normal donors and 208 patients scheduled for breast biopsy were analyzed by water-suppressed H-1 and C-13 NMR spectroscopy. Triglyceride levels were also measured. Among the normal donors, there were 38 individuals with hypertriglyceridemia of whom 18 had results consistent with malignancy by H-1 NMR spectroscopy. However, the C-13 technique reduced the apparent H-1 false positive rate from 7.0% to 0.6%. Similarly, in the breast biopsy cohort, C-13 reduced the false positive rate from 2.8% to 0.9%. Furthermore, the accuracy of the combined H-1/C-13 test in this blinded study was greater than 96% in 208 patients studied.     

Distinction of normal, preneoplastic, and neoplastic mouse mammary primary cell cultures by water nuclear magnetic resonance relaxation times

Normal, preneoplastic, and neoplastic primary cultures of mouse mammary epithelial cells were distinguishable on the basis of water proton nuclear magnetic resonance (NMR) relaxation times--i.e., spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). T1 values were 916 +/- 24 msec for normal cells, 1,029 +/- 24 msec for preneoplastic cells, and 1,155 +/- 42 msec for neoplastic cells. This method of distinction between normal and neoplastic cells (P less than 0.001) and normal and preneoplastic cells (P less than 0.005) supported previous findings in whole tissues. NMR relaxation times resulted in better distinction between these cell populations than any other technique except direct histology. The T1 and T2 values of water protons in cells grown in primary culture were higher than those of established mouse mammary cancer cell lines. The differences in T1 and T2 did not correlate with cellular hydration. The data suggested a basic difference in water-macromolecular surface interactions among normal, preneoplastic, and neoplastic cells.     

Quantitative analysis of immunocompetent cells in oral submucous fibrosis in Taiwan.

Previous studies have shown that the local and systemic upregulation of inflammatory and fibrogenic cytokines and downregulation of antifibrotic cytokines are central to the pathogenesis of oral submucous fibrosis (OSF). The immunocompetent cells, especially the macrophages and lymphocytes, are likely the main source of cytokine synthesis. Therefore, this study used an immunohistochemical method to quantify the T lymphocyte, B lymphocyte and macrophage densities in the epithelium and subepithelial connective tissue of 50 specimens of moderately advanced and advanced OSF and 10 specimens of normal oral mucosa (NOM). The mean T lymphocyte, B lymphocyte and macrophage densities in OSF specimens were 555.2+/-417.4, 63.4+/-44.3 and 66.9+/-76.4 cells/mm(2) in the subepithelial connective tissue and 308.1+/-261.1, 1.4+/-3.5 and 6.6+/-11.9 cells/mm(2) in the epithelium, respectively. These findings suggest that T lymphocytes were the major immunocompetent cells in both the subepithelial connective tissue and epithelium of OSF specimens. Macrophages and B lymphocytes are the minor immunocompetent cells in the subepithelial connective tissue and are only occasionally found in the epithelium of OSF specimens. Similar distribution of immunocompetent cells was also found in NOM specimens. However, the mean T lymphocyte, B lymphocyte and macrophage densities in the subepithelial connective tissue (271.2+/-107.0, 13.3+/-18.4 and 17.3+/-19.1 cells/mm(2), respectively) and the mean T lymphocyte density in the epithelium (97.7+/-51.4) of NOM specimens were significantly lower than the corresponding mean cell densities in OSF specimens. Using frozen tissue sections, we further quantified the CD4+ and CD8+ lymphocyte numbers in eight moderately advanced or advanced OSF specimens. It was found that the CD4+ and CD8+ lymphocyte densities were 213.3+/-140.7 and 101.5+/-72.8 cells/mm(2) in the subepithelial connective tissue of OSF specimens, respectively. The CD4+ to CD8+ lymphocyte ratio was 2.1:1. Our results showed a significant increase in the number of T lymphocytes and macrophages and a predominance of CD4+ lymphocytes over CD8+ lymphocytes in the subepithelial connective tissue of OSF specimens. We conclude that the cellular immune response may play an important role in the pathogenesis of OSF.     

Relationship of the queuine content of transfer ribonucleic acids to histopathological grading and survival in human lung cancer.

To elucidate the significance of tRNA hypomodified with queuine to the grade of malignancies in human solid tumors, the amount of tRNA having guanosine in place of queuosine was determined in human lung cancer and normal lung tissue, by exchanging the unmodified guanosine residue for [3H]guanine. The reaction is catalyzed by guanine:queuine tRNA transglycosylase. Total tRNA was extracted from 23 different lung cancer specimens and the precursor of isoacceptor tRNA that contains guanine instead of queuine in the first or wobble position of the anticodon [(Q-)tRNA] content was determined. In 12 cases the (Q-)-tRNA was determined in normal lung tissues as well. In each individual, the (Q-)tRNA content in lung cancer tissue was higher than that of the normal lung tissue. The (Q-)tRNA content was not correlated to the surgicopathological staging of the patients but was highly correlated to the histopathological classification of the tumors. The amounts of (Q-)-tRNA were 1.75 +/- 0.67 (SD), 2.36 +/- 0.89, 3.77 +/- 1.39, 5.18 +/- 2.32, and 7.65 +/- 1.34 pmol/A260 in normal, well, moderately, moderately to poorly, and poorly differentiated tumors. The difference from normal to moderately differentiated or less differentiated groups was significant (P less than 0.05). In 10 patients with (Q-)tRNA higher than 3.5 pmol/A260, their cancers relapsed and only 2 were alive after 4 years. In 11 patients with (Q-)tRNA less than 3.5 pmol/A260 in their lung cancer tissues, 7 patients were still alive without any evidence of disease, 3 were dead, and 1 had recurrence of disease. These results, taken together with other previous studies, suggest that a decreased queuosine content of tRNA may be a general feature of neoplasms and may be useful for grading malignancy and perhaps also for the prediction of survival in human lung cancer.     

NMR spectroscopy and pediatric brain tumors

Proton nuclear magnetic resonance spectroscopy ((1)H-NMRS) is a noninvasive in vivo technique that utilizes conventional MR imaging hardware to obtain biochemical information from a discrete volume of tissue after suppression of the water signal. MR spectroscopy coupled with conventional MR imaging allows correlation of structural changes with biochemical processes in tissues by measuring specific metabolites present in brain tissue. NMRS is commonly used in the evaluation of patients with brain tumors. This article reviews the basic principles of spectroscopy and its use in evaluating pediatric patients with brain tumors.     

Status of sex steroid hormone receptors in large bowel cancer

To determine the potential role of sex steroid hormones in the development of colorectal tumors in humans, specific androgen (AR), estrogen (ER), and progesterone (PGR) receptors were investigated in normal mucosa (NM) and in tumor (T) paired biopsy specimens from 94 patients. Androgen receptors were detected in 98% and 96% of NM and T samples, ER in 91% and 83% of NM and T biopsy samples, whereas PGR were detected only in 14% and 10% of NM and T specimens, respectively. These incidences are independent of the sex and age of the patients. They are not related to tumor localization, histologic grade, or stages of Dukes' classification. Scatchard analysis of labeled ligand binding indicated the existence of one single class of high affinity binding sites; the calculated dissociation constant (Kd) was 1.7 +/- 0.6 10(-9) molar concentration (M) for 5 alpha-dihydrotestosterone (DHT) and 0.6 +/- 0.3 10(-9) M for estradiol (E2). These values were identical in NM and T tissue for both AR and ER. The binding capacity for DHT was 148 +/- 67 and 93 +/- 43 fmol/mg of cytosol protein in NM and T tissues, respectively (P less than 0.05). The ER content was lower and similar in NM and T biopsy specimens: 19 +/- 9 and 18 +/- 10 fmol/mg protein, respectively. The PGR content was 10 +/- 4 in NM versus 17.5 +/- 6 fmol/mg protein in T specimens. It is observed that the elevated AR in normal mucosa is not related to any known function for androgens in the digestive tract. The receptor pattern observed in tumors does not support the hypothesis previously raised in the case of chemically induced colonic tumors in rodents.     

Measurement by nuclear magnetic resonance diffusion of the dimensions of the mobile lipid compartment in C6 cells

The (1)H spectrum of certain tumor cells, in vivo tumors, and their biopsies in vitro shows a narrow and intense resonance at 1.26 ppm, which has been assigned to the fatty acyl chain of triglycerides [nuclear magnetic resonance (NMR) visible mobile lipids, MLs]. We have used diffusion-weighted NMR spectroscopy to directly address the subcellular origin of MLs in the case of C6 cells in which lactate accumulation had been inhibited by prior iodoacetamide incubation. Borage oil and artificial lipid droplets were used as model systems of free and restricted diffusion, respectively. The characteristic diameter for the ML resonance compartment measured by NMR for the C6 cells was not significantly different from the one obtained with phase contrast microscopy (1.88 +/- 0.04 micro m from NMR versus 1.37 +/- 0.33 micro m from microscopy). We herewith provide direct and noninvasive evidence that the lipid signal at 1.26 ppm in C6 cells, which remains visible in long echo time (T(E) = 136 ms) experiments, mostly originates from subcellular structures with diameters of 1-2 micro m, which correspond to the cytosolic lipid droplets that can be detected in optical microscopy preparations of the same cells.     

High glycolytic activity in rat glioma demonstrated in vivo by correlation peak 1H magnetic resonance imaging.

High-grade brain tumors are known to have a high rate of glucose (Glc) consumption. Postmortem measurements have suggested that Glc content in experimental brain tumors is relatively low. We used magnetic resonance spectroscopy to investigate this, in vivo, in the brains of seven rats bearing intracerebral C6 gliomas. We combined the high spectral resolution allowed by two-dimensional proton nuclear magnetic resonance with spatial encoding by magnetic field gradient pulses to obtain in vivo maps of Glc, alanine, hypotaurine, aspartate, phosphoethanolamine, Glu/Gln, N-acetylaspartate (NAA), phosphocreatine/creatine (PCr/Cr), choline-containing compounds, and lactate (Lac) (some of which are involved in energy metabolism). Compared with normal brain tissue, the main differences found in the gliomas were that Glc, NAA, PCr/Cr, and aspartate concentrations were much lower, whereas concentrations of alanine, hypotaurine, phosphoethanolamine, and Lac were higher, whatever the extent of necrosis. A striking observation is the similarity of the NAA and Glc images: the concentrations of both metabolites are lower in the tumor than they are in the contralateral brain. If Glc was completely absent from the tumor tissue, and if the residual Glc level was due only to a partial volume effect like that for NAA, a neuronal marker, the ratio [Glc]tumor/[Glc]contralateral tissue, should be similar to that found for NAA. The ratio for Glc was 0.48 +/- 0.22 (+/- SD; n = 6), a ratio similar to that found for PCr/Cr (0.50 +/- 0.19) but significantly higher than that obtained for NAA (0.29 +/- 0.07). This observation indicates that a measurable Glc concentration is still present in the tumor tissue. Intense glycolysis in tumor cells may explain the increased production of Lac and alanine and decreased amount of Glc. These nuclear magnetic resonance measurements of metabolite concentrations are complementary to positron emission tomography, which measures Glc consumption.     

MRI-guided 3D optimization significantly improves DVH parameters of pulsed-dose-rate brachytherapy in locally advanced cervical cancer

PURPOSE: To compare dose-volume histogram parameters of standard Point A and magnetic resonance imaging-based three-dimensional optimized dose plans in 21 consecutive patients who underwent pulsed-dose-rate brachytherapy (PDR-BT) for locally advanced cervical cancer. METHODS AND MATERIALS: All patients received external beam radiotherapy (elective target dose, 45 Gy in 25-30 fractions; tumor target dose, 50-60 Gy in 25-30 fractions). PDR-BT was applied with a tandem-ring applicator. Additional ring-guided titanium needles were used in 4 patients and a multichannel vaginal cylinder in 2 patients. Dose planning was done using 1.5 Tesla T(1)-weighted and T(2)-weighted paratransversal magnetic resonance imaging scans. T(1)-weighted visible oil-containing tubes were used for applicator reconstruction. The prescribed standard dose for PDR-BT was 10 Gy (1 Gy/pulse, 1 pulse/h) for two to three fractions to reach a physical dose of 80 Gy to Point A. The total dose (external beam radiotherapy plus brachytherapy) was normalized to an equivalent dose in 2-Gy fractions using alpha/beta = 10 Gy for tumor, alpha/beta = 3 Gy for normal tissue, and a repair half-time of 1.5 h. The goal of optimization was dose received by 90% of the target volume (D(90)) of > or =85 Gy(alpha/beta10) in the high-risk clinical target volume (cervix and remaining tumor at brachytherapy), but keeping the minimal dose to 2 cm(3) of the bladder and rectum/sigmoid at <90 and <75 Gy(alpha/beta3), respectively. RESULTS: Using three-dimensional optimization, all dose-volume histogram constraints were met in 16 of 21 patients compared with 3 of 21 patients with two-dimensional library plans (p < 0.001). Optimization increased the minimal target dose (D(100)) of the high-risk clinical target volume (p < 0.007) and decreased the minimal dose to 2 cm(3) for the sigmoid significantly (p = 0.03). For the high-risk clinical target volume, D(90) was 91 +/- 8 Gy(alpha/beta10) and D(100) was 76 +/- 5 Gy(alpha/beta10). The minimal dose to 2 cm(3) for the bladder, rectum, and sigmoid was 73 +/- 6, 67 +/- 6, and 69 +/- 6 Gy(alpha/beta3), respectively. CONCLUSION: The results of our study have shown that magnetic resonance imaging-guided optimization of PDR-BT for locally advanced cervical cancer significantly improved the dose-volume histogram parameters.     

Variation of the magnetic relaxation rate 1/T1 of water protons with magnetic field strength (NMRD Profile) of untreated,non-calcified,human astrocytomas: correlation with histology and solids content

Summary The magnetic relaxation rate 1/T1 of tissue water protons was measured over a wide range of magnetic field strengths (NMRD profile) for 92 fresh surgical specimens of astrocytomas to search for correlations of 1/T1 with tumor histology, as determined by light microscopy, and to assess the diagnostic potential of NMRD profiles for grading astrocytomas. A third goal was to elucidate the molecular determinants of 1/T1. Each specimen was histologically graded and inspected for evidence of mineral deposits (Ca, Fe); its dry weight was determined and expressed in % of original wet weight. To minimize variability not directly related to tumor grade, this initial report is limited to NMRD profiles of 47 non-calcified, non-mehorrhagic, untreated astrocytomas. For these, the mean value of 1/T1 at very low magnetic field strenghts was found to increase with increasing grade of malignancy; no clear correlation could be demonstrated at high fields where most imaging is done. The spread of 1/T1 for different grades of malignancy is large, however, and the overlap significant, even at the lowest field, so that astrocytomas can not be graded by NMRD profiles alone. Average 1/T1 and average dry weight increase with grade of malignancy; but the variability of 1/T1 among specimens of the same dry weight is large, indicating that at least one other cellular parameter, not variable in normal tissue, influences 1/T1 strongly. We hypothesize that this parameter reflects changes at the molecular level in size distribution, mobility, or intermolecular interaction of cytoplasmic proteins. Which specific changes are induced by malignant transformation in astrocytomas remains to be investigated.     

Rapid detection of metastatic melanoma in lymph nodes using proton magnetic resonance spectroscopy of fine needle aspiration biopsy specimens

Accurate staging of patients with primary cutaneous melanoma includes assessment of regional lymph nodes for the presence of micrometastatic disease. Sentinel lymph node biopsy is highly accurate but is an invasive surgical procedure with a 5-10% complication rate, and requires labour-intensive and expensive histological examination to identify disease. A rapid, accurate and cost-effective non-surgical technique able to detect micrometastatic deposits of melanoma in regional lymph nodes would be of great benefit. Fine needle aspiration biopsies and tissue specimens were obtained from lymph nodes from 18 patients undergoing node resection for metastatic melanoma and five patients undergoing radical retropubic prostatectomy. One-dimensional proton magnetic resonance spectroscopy was undertaken at 360 MHz (8.5 T). Lymph nodes were cut into 3 mm thick slices and embedded. Four sequential 5 microm tissue sections were cut from each block and stained, with haematoxylin and eosin, for S100 protein, for HMB45, and again with haematoxylin and eosin, respectively. Proton magnetic resonance spectroscopy distinguished between benign and malignant lymph node tissue (P < 0.001, separate t-test) and benign and malignant lymph node fine needle aspiration biopsy (P < 0.012) based on the ratio of the integrals of resonances from lipid/other metabolites (1.8-2.5 p.p.m. region) and 'choline' (3.1-3.3 p.p.m. region). In conclusion, one-dimensional proton magnetic resonance spectroscopy on a simple fine needle aspiration biopsy can distinguish lymph nodes containing metastatic melanoma from uninvolved nodes, providing a rapid, accurate and cost-effective non-surgical technique to assess regional lymph nodes in patients with melanoma.     

Discrimination of metabolic profiles of pancreatic cancer from chronic pancreatitis by high-resolution magic angle spinning 1H nuclear magnetic resonance and principal components analysis

The metabolic profiles of Sprague-Dawley rat pancreases were investigated by high-resolution magic angle spinning proton magnetic resonance spectroscopy ((1)H NMR) combined with principal components analysis (PCA) to discriminate pancreatic cancer from chronic pancreatitis. Intact pancreatic tissue samples were obtained from Sprague-Dawley rats with histologically proven pancreatic cancer (n = 5), chronic pancreatitis (n = 5), and two matched controls (n = 5 per group). Two (1)H NMR experiments, single-pulse and Carr-Purcell-Meiboom-Gill, were carried out separately. Increases in phosphocholine and glycerophosphocholine levels and decreases in leucine, isoleucine, valine, lactate and alanine levels were observed in chronic pancreatitis, whereas the opposite trends were observed in pancreatic cancer. Increasing taurine and decreasing betaine were found both in chronic pancreatitis and in pancreatic cancer. Additionally, the lipid content in pancreatic cancer was higher than that in chronic pancreatitis. PCA was carried out for the single-pulse and Carr-Purcell-Meiboom-Gill (1)H NMR spectra, respectively, to visualize separation among the samples and to extract characteristic metabolites of pancreatic cancer and chronic pancreatitis. Decreased phosphocholine and glycerophosphocholine were suggested as unique metabolite indicators of pancreatic cancer. Furthermore, even with the disturbance of various quantities of lipid contents pancreatic cancer and chronic pancreatitis could be differentiated well by the combination of high-resolution magic angle spinning (1)H NMR and PCA. Thus this combination was demonstrated to have the potential to improve magnetic resonance spectroscopy for positive early diagnosis of pancreatic cancer in clinical settings.     

Failure of 1H nuclear magnetic resonance spectroscopy of blood plasma to detect malignancy

Water-suppressed proton nuclear magnetic resonance (NMR) of plasma was proposed as a technique for detecting malignant tumors. In that analysis, bloods drawn from cancer patients at the Beth Israel Hospital (BIH; Boston, MA), were easily distinguished from normal subjects by measuring and averaging the proton NMR methyl and methylene line widths of plasma lipoproteins. We collected blood at the Massachusetts General Hospital (MGH), including from normal controls, patients with untreated and treated malignant tumors, and patients with nontumor diseases. The plasma NMR analyses were carried out blind. The code was not broken until all patient charts and pathology records were reviewed, plasma analyses were completed, and patients had been divided into appropriate clinical groups. Analysis of these data showed no differences between the means of the study groups (false-positive and false-negative frequencies 46% and 57%, respectively). An inverse correlation of methyl/methylene line widths with age (P less than .01), and a correlation with nitrate-requiring cardiovascular disease (P less than .05) was, however, evident. This test cannot be validly used to detect malignancy.     

磁共振弥散加权成像在胶质瘤分级中的价值

目的 探讨磁共振弥散加权成像(DWI)及表观弥散系数(ADC)在鉴别胶质瘤瘤体区、瘤周区和正常组织中的应用及鉴别胶质瘤良、恶性的价值.方法 采用Philips 1.5T Achieva超导型磁共振成像仪,对46例胶质瘤患者行常规MRI及DWI,弥散系数b值分别取0和1 000 s/mm2,测量瘤体区、瘤周区及对侧正常组...     

Nuclear magnetic resonance investigations of human neoplastic and abnormal nonneoplastic tissues.

A large number of samples of human neoplastic and abnormal nonneoplastic tissues were studied by nuclear magnetic resonance spectrometry in order to evaluate the possible role of this technique in the diagnosis of cancer. The spin-lattice magnetic relaxation times (T1) of abnormal nonneoplastic tissue were longer, in many instances, than those of malignant tumors from similar sites, preventing recognition of the tumors in this manner. The evidence for the nonspecific nature of the prolongation of T1 in abnormal tissue is reviewed, and additional limitations of this technique in the diagnosis of cancer are indicated.     

Nuclear magnetic resonance computed tomography (NMR-CT) of malignancies

The physical principles of nuclear magnetic resonance (NMR) imaging were initially outlined. In the present proton images, T1 and T2 relaxation times were more important than proton density in determining the varying intensity of the tissue. Early clinical experiences of NMR for malignancies of the head and neck region, chest, abdomen, pelvis and extremities were also presented. There was superb ability for soft tissue characterizations, accentuating intensity difference between tissues with different T1 and T2 relaxation time. Although the spatial resolution of NMR-CT appeared to be inferior to X-CT, the absence of streak artifacts or X-ray beam hardening were advantageous. Because of the absence of significant NMR signal from rapidly flowing blood, the differentiation of vessels and soft tissue masses was easily accomplished by NMR-CT without employing contrast material. Multisection scans were performed in most cases with not only transverse but sagittal or coronal imaging by simply varying the sequence of pulse gradient magnetic field. While more experience is required, NMR-CT has a promising future in the imaging modality for malignancies.     

Comparison of noninvasive MRT procedures for temperature measuremnt for the application of medical heat therapies

Novel methods for hyperthermia tumor therapy, such as high-intensity focused ultrasound (HIFU) or laser-induced thermotherapy (LITT), require accurate non-invasive temperature monitoring. Non-invasive temperature measurement using magnetic resonance imaging (MRI) is based on the analysis of changes in longitudinal relaxation time (T1), diffusion coefficient (D), or water proton resonance frequency (PRF). The purpose of this study was the development and comparative analysis of the three different approaches of MRI temperature monitoring (T1, D, and PRF). Measurements in phantoms (e.g., ultrasound gel) resulted in the following percent changes: T1-relaxation time: 1.98%/degree C; diffusion coefficient: 2.22%/degree C; and PRF: -0.0101 ppm/degree C. All measurements were in good agreement with the literature. Temperature resolutions could also be measured from the inverse correlation of the data over the whole calibration range: T1: 2.1 +/- 0.6 degrees C; D: 0.93 +/- 0.2 degree C; and PRF: 1.4 +/- 0.3 degrees C. The diffusion and PRF methods were not applicable in fatty tissue. The use of the diffusion method was restricted due to prolonged echo time and anisotropic diffusion in tissue. Initial tests with rabbit muscle tissue in vivo indicated that MR thermometry via T1 and PRF procedures is feasible to monitor the local heating process induced by HIFU. The ultrasound applicators in the MR scanner did not substantially interfere with image quality.