Human tumors detected by nuclear magnetic resonance

In-cell NMR: Why and how?

NMR spectroscopy has been applied to cells and tissues analysis since its beginnings, as early as 1950. We have attempted to gather here in a didactic fashion the broad diversity of data and ideas that emerged from NMR investigations on living cells. Covering a large proportion of the periodic table, NMR spectroscopy permits scrutiny of a great variety of atomic nuclei in all living organisms non-invasively. It has thus provided quantitative information on cellular atoms and their chemical environment, dynamics, or interactions. We will show that NMR studies have generated valuable knowledge on a vast array of cellular molecules and events, from water, salts, metabolites, cell walls, proteins, nucleic acids, drugs and drug targets, to pH, redox equilibria and chemical reactions. The characterization of such a multitude of objects at the atomic scale has thus shaped our mental representation of cellular life at multiple levels, together with major techniques like mass-spectrometry or microscopies. NMR studies on cells has accompanied the developments of MRI and metabolomics, and various subfields have flourished, coined with appealing names: fluxomics, foodomics, MRI and MRS (i.e. imaging and localized spectroscopy of living tissues, respectively), whole-cell NMR, on-cell ligand-based NMR, systems NMR, cellular structural biology, in-cell NMR… All these have not grown separately, but rather by reinforcing each other like a braided trunk. Hence, we try here to provide an analytical account of a large ensemble of intricately linked approaches, whose integration has been and will be key to their success. We present extensive overviews, firstly on the various types of information provided by NMR in a cellular environment (the "why", oriented towards a broad readership), and secondly on the employed NMR techniques and setups (the "how", where we discuss the past, current and future methods). Each subsection is constructed as a historical anthology, showing how the intrinsic properties of NMR spectroscopy and its developments structured the accessible knowledge on cellular phenomena. Using this systematic approach, we sought i) to make this review accessible to the broadest audience and ii) to highlight some early techniques that may find renewed interest. Finally, we present a brief discussion on what may be potential and desirable developments in the context of integrative studies in biology.

In Memoriam: Raymond V. Damadian, M.D

Dr. Raymond Damadian, Father of the MRI, passed away on August 3, 2022. In this Letter to the Editor, we discuss Dr. Damadian’s seminal discovery, his path to making the first MRI machine, as well as the work he did in his later years on the dynamics of CSF flow in neurodegenerative disease. We hope to honor the legacy of such an influential character in radiology history and inspire others to continue to continue to explore, innovate, and cure disease with his technology for years to come.

Heat Modulation of Intrinsic MR Contrasts for Tumor Characterization

(1) Background: The longitudinal relaxation time (T1), transverse relaxation time (T2), water proton chemical shift (CS), and apparent diffusion coefficient (ADC) are MR quantities that change with temperature. In this work, we investigate heat-induced intrinsic MR contrast types to add salient information to conventional MR imaging to improve tumor characterization. (2) Methods: Imaging tests were performed in vivo using different rat tumor models. The rats were cooled/heated to steady-state temperatures from 26–36 °C and quantitative measurements of T1, T2, and ADC were obtained. Temperature maps were measured using the proton resonance frequency shift (PRFS) method during the heating and cooling cycles. (3) Results: All tissue samples show repeatable relaxation parameter measurement over a range of 26–36 °C. Most notably, we observed a more than 3.3% change in T1/°C in breast adenocarcinoma tumors compared to a 1% change in benign breast fibroadenoma lesions. In addition, we note distinct values of T2/°C change for rat prostate carcinoma cells compared to benign tissue. (4) Conclusion: These findings suggest the possibility of improving MR imaging visualization and characterization of tissue with heat-induced contrast types. Specifically, these results suggest that the temporal thermal responses of heat-sensitive MR imaging contrast mechanisms in different tissue types contain information for improved (i) characterization of tumor/tissue boundaries for diagnostic and therapy purposes, and (ii) characterization of salient behavior of tissues, e.g., malignant versus benign tumors.

Fully Integrated Quantitative Multiparametric Analysis of Non-Small Cell Lung Cancer at 3-T PET/MRI: Toward One-Stop-Shop Tumor Biological Characterization at the Supervoxel Level

INTRODUCTION

The aim of this study was to study the feasibility of a fully integrated multiparametric imaging framework to characterize non-small cell lung cancer (NSCLC) at 3-T PET/MRI.

PATIENTS AND METHODS

An 18F-FDG PET/MRI multiparametric imaging framework was developed and prospectively applied to 11 biopsy-proven NSCLC patients. For each tumor, 12 parametric maps were generated, including PET full kinetic modeling, apparent diffusion coefficient, T1/T2 relaxation times, and DCE full kinetic modeling. Gaussian mixture model-based clustering was applied at the whole data set level to define supervoxels of similar multidimensional PET/MRI behaviors. Taking the multidimensional voxel behaviors as input and the supervoxel class as output, machine learning procedure was finally trained and validated voxelwise to reveal the dominant PET/MRI characteristics of these supervoxels at the whole data set and individual tumor levels.

RESULTS

The Gaussian mixture model-based clustering clustering applied at the whole data set level (17,316 voxels) found 3 main multidimensional behaviors underpinned by the 12 PET/MRI quantitative parameters. Four dominant PET/MRI parameters of clinical relevance (PET: k2, k3 and DCE: ve, vp) predicted the overall supervoxel behavior with 97% of accuracy (SD, 0.7; 10-fold cross-validation). At the individual tumor level, these dimensionality-reduced supervoxel maps showed mean discrepancy of 16.7% compared with the original ones.

CONCLUSIONS

One-stop-shop PET/MRI multiparametric quantitative analysis of NSCLC is clinically feasible. Both PET and MRI parameters are useful to characterize the behavior of tumors at the supervoxel level. In the era of precision medicine, the full capabilities of PET/MRI would give further insight of the characterization of NSCLC behavior, opening new avenues toward image-based personalized medicine in this field.

Going Low in a World Going High: The Physiologic Use of Lower Frequency Electron Paramagnetic Resonance

Yakov Sergeevich Lebedev was a pioneer in high frequency EPR, taking advantage of the separation of g-factor anisotropy effects from nuclear hyperfine splitting and the higher frequency molecular motion sensitivity from higher frequency measurements⁸. This article celebrates a second EPR subfield in which Prof. Lebedev pioneered, EPR imaging. ⁹ We celebrate the clinical enhancements that are suggested in this low frequency work and imaging application to animal physiology at lower-than-standard EPR frequencies.

Simultaneous T1 and T2 mapping of hyperpolarized 13C compounds using the bSSFP sequence

As in conventional ¹H MRI, T₁ and T₂ relaxation times of hyperpolarized (HP) ¹³C nuclei can provide important biomedical information. Two new approaches were developed for simultaneous T₁ and T₂ mapping of HP ¹³C probes based on balanced steady state free precession (bSSFP) acquisitions: a method based on sequential T₁ and T₂ mapping modules, and a model-based joint T₁/T₂ approach analogous to MR fingerprinting. These new methods were tested in simulations, HP ¹³C phantoms, and in vivo in normal Sprague-Dawley rats. Non-localized T₁ values, low flip angle EPI T₁ maps, bSSFP T₂ maps, and Bloch-Siegert B₁ maps were also acquired for comparison. T₁ and T₂ maps acquired using both approaches were in good agreement with both literature values and data from comparative acquisitions. Multiple HP ¹³C compounds were successfully mapped, with their relaxation time parameters measured within heart, liver, kidneys, and vasculature in one acquisition for the first time.

Short-time Fourier Transform of Free Induction Decays for the Analysis of Serum Using Proton Nuclear Magnetic Resonance

Proton nuclear magnetic resonance (NMR) is useful for the analysis of biological samples such as serum. Free induction decays (FIDs) are NMR signals that follow a radio-frequency pulse applied at the resonance frequency. Short-time Fourier transform (STFT) is a basic method for time-frequency analyses. The purpose of this study was to ascertain whether the STFT of FIDs enables the sensitive detection of changes and differences in serum properties. FIDs were obtained from serum collected from young, healthy, male volunteers ≤ 40 years of age and seniors ≥ 65 years of age. Temporal changes in the instantaneous amplitudes for the time-domain analysis, fast Fourier transform for frequency-domain analysis, and STFT were applied to the FIDs. The STFT-based spectrogram represented the complex frequency components that changed dynamically over time, indicating that the spectrogram enabled the visualization of the features of an FID. Furthermore, the results of a partial least-squares discriminant analysis demonstrated that the STFT was superior to the other two methods for discriminating between serum from younger and older subjects. In conclusion, the STFT of FIDs obtained from proton NMR measurements was useful for evaluating similarities and dissimilarities in the FIDs obtained from serum samples.

Current and Future Approaches for Effective Cancer Imaging and Treatment

Cancer poses a major health problem, not only due to cancer-related deaths but also because of treatment toxicities. This review discusses early diagnosis and strategies to overcome treatment difficulties, to facilitate recovery, and prevent deaths. Generally, noninvasive techniques such as computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and positron emission computed tomography (PET), and their hybrid systems, including SPECT/CT, PET/CT, and PET/MRI, are used in diagnosis of cancer. Cancer treatment in clinics still comprises conventional methods such as chemotherapy, radiotherapy, and surgery. However, these techniques and methods are often inadequate. Therefore, new approaches, including the formulation of actively and/or passively targeted nanosized drug delivery systems and combined treatment protocols, are being investigated. In this article, conventional cancer imaging and treatment are reviewed. In addition, the formulation of nanosized systems and their use in cancer treatment are discussed and combined diagnostic and therapeutic (theranostic) approach are proposed as additional cancer therapies.

Histopathological Evidence in Support of the Association of Elevated Proton Spin-lattice Relaxation Times with the Malignant State

The pulsed nuclear magnetic resonance technique was explored for its potential diagnostic value in human cancer. Measurements of proton spin-lattice relaxation times (T1) of cellular water protons of normal and malignant esophageal tissues showed elevated T, values in the latter. In some cases, tissues which appeared normal on gross examination assumed as uninvolved tissues had T, values higher than the other grossly uninvolved tissues and often closer to the T, of the corresponding tumor tissue. A histopathological study of the assumed uninvolved areas also studied for the T, values was therefore undertaken. A preliminary study demonstrated the presence of malignant cell groups or clusters in some of the uninvolved samples with higher T1 compared to the true uninvolved tissues, which had a normal histological picture and low T, values. This observation has brought out the importance of histopathological studies in addition to relaxation studies to comprehend contributory factors to relaxation. Secondly, it lends support to the thesis of elevated T, values being characteristics of the malignant state.

Detection of Bone Marrow Involvement in Patients with Cancer

Current methods for the study of bone marrow to evaluate possible primary or metastatic cancers are reviewed. Bone marrow biopsy, radionuclide scan, computed tomography and magnetic resonance imaging (MRI) are analyzed with regard to their clinical usefulness at the time of diagnosis and during the course of the disease. Bone marrow biopsy is still the examination of choice not only in hematologic malignancies but also for tumors that metastasize into the marrow. Radionuclide scans are indicated for screening for skeletal metastases, except for those from thyroid carcinoma and multiple myeloma. Computed tomography is useful for cortical bone evaluation. MRI shows a high sensitivity in finding occult sites of disease in the marrow but its use has been restricted by high cost and limited availability. However, the future of MRI in bone marrow evaluation seems assured. MRI is already the method of choice for diagnosis of multiple myeloma, when radiography is negative, and for quantitative evaluation of lymphoma when a crucial therapeutic decision (i.e. bone marrow transplantation) must be made. Finally, methods are being developed that will enhance the sensitivity and specificity of MRI studies of bone marrow.

Cancer Metabolism and Tumor Heterogeneity: Imaging Perspectives Using MR Imaging and Spectroscopy

Cancer cells reprogram their metabolism to maintain viability via genetic mutations and epigenetic alterations, expressing overall dynamic heterogeneity. The complex relaxation mechanisms of nuclear spins provide unique and convertible tissue contrasts, making magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) pertinent imaging tools in both clinics and research. In this review, we summarized MR methods that visualize tumor characteristics and its metabolic phenotypes on an anatomical, microvascular, microstructural, microenvironmental, and metabolomics scale. The review will progress from the utilities of basic spin-relaxation contrasts in cancer imaging to more advanced imaging methods that measure tumor-distinctive parameters such as perfusion, water diffusion, magnetic susceptibility, oxygenation, acidosis, redox state, and cell death. Analytical methods to assess tumor heterogeneity are also reviewed in brief. Although the clinical utility of tumor heterogeneity from imaging is debatable, the quantification of tumor heterogeneity using functional and metabolic MR images with development of robust analytical methods and improved MR methods may offer more critical roles of tumor heterogeneity data in clinics. MRI/MRS can also provide insightful information on pharmacometabolomics, biomarker discovery, disease diagnosis and prognosis, and treatment response. With these future directions in mind, we anticipate the widespread utilization of these MR-based techniques in studying in vivo cancer biology to better address significant clinical needs.

Topological impact of noncanonical DNA structures on Klenow fragment of DNA polymerase

Noncanonical DNA structures that stall DNA replication can cause errors in genomic DNA. Here, we investigated how the noncanonical structures formed by sequences in genes associated with a number of diseases impacted DNA polymerization by the Klenow fragment of DNA polymerase. Replication of a DNA sequence forming an i-motif from a telomere, hypoxia-induced transcription factor, and an insulin-linked polymorphic region was effectively inhibited. On the other hand, replication of a mixed-type G-quadruplex (G4) from a telomere was less inhibited than that of the antiparallel type or parallel type. Interestingly, the i-motif was a better inhibitor of replication than were mixed-type G4s or hairpin structures, even though all had similar thermodynamic stabilities. These results indicate that both the stability and topology of structures formed in DNA templates impact the processivity of a DNA polymerase. This suggests that i-motif formation may trigger genomic instability by stalling the replication of DNA, causing intractable diseases.

Determination of an optimally sensitive and specific chemical exchange saturation transfer MRI quantification metric in relevant biological phantoms

The purpose of this study was to develop realistic phantom models of the intracellular environment of metastatic breast tumour and naïve brain, and using these models determine an analysis metric for quantification of CEST MRI data that is sensitive to only labile proton exchange rate and concentration. The ability of the optimal metric to quantify pH differences in the phantoms was also evaluated. Novel phantom models were produced, by adding perchloric acid extracts of either metastatic mouse breast carcinoma cells or healthy mouse brain to bovine serum albumin. The phantom model was validated using 1 H NMR spectroscopy, then utilized to determine the sensitivity of CEST MRI to changes in pH, labile proton concentration, T1 time and T2 time; six different CEST MRI analysis metrics (MTRasym , APT*, MTRRex , AREX and CESTR* with and without T1 /T2 compensation) were compared. The new phantom models were highly representative of the in vivo intracellular environment of both tumour and brain tissue. Of the analysis methods compared, CESTR* with T1 and T2 time compensation was optimally specific to changes in the CEST effect (i.e. minimal contamination from T1 or T2 variation). In phantoms with identical protein concentrations, pH differences between phantoms could be quantified with a mean accuracy of 0.6 pH units. We propose that CESTR* with T1 and T2 time compensation is the optimal analysis method for these phantoms. Analysis of CEST MRI data with T1 /T2 time compensated CESTR* is reproducible between phantoms, and its application in vivo may resolve the intracellular alkalosis associated with breast cancer brain metastases without the need for exogenous contrast agents.

Australian radiation therapy - Part two: Reflections of the past, the present, the future

Introduction: Documentation on the history of Australian radiotherapy is limited. This study provides radiation therapists' (RTs) perspectives of the people, workplace, and work practices in Australian radiotherapy centres from 1960 onwards. It provides a follow-up to our previous study: Australian radiation therapy: An overview – Part one, which outlines the history and development of radiotherapy from conception until present day.

Methods: Four focus groups were conducted on separate occasions in 2010, one in South Australia and three in Victoria, Australia. Participants who worked in radiotherapy were purposively selected to ensure a range of experience, age, and years of work.

Results: From a RT perspective, radiotherapy has evolved from a physically demanding ‘hands-on’ work environment, often with unpleasant sights and smells of disease, to a more technology-driven workplace.

Conclusion: Understanding these changes and their subsequent effects on the role of Australian RTs will assist future directions in advanced role development.

A novel approach to assess mean lethal radiation dose with water proton spin lattice relaxation times

The assessment of mean lethal radiation dose (D0) in human organs, using multi-target and linear quadratic models, with water proton nuclear magnetic resonance spin lattice relaxation time yields a correlation coefficient of 0.90 and 0.82, respectively. Results of this study reveal that as the spin lattice relaxation time increases, the D0 decreases.

Metabolic imaging by hyperpolarized 13C magnetic resonance imaging for in vivo tumor diagnosis

The "Warburg effect," an elevation in aerobic glycolysis, may be a fundamental property of cancer cells. For cancer diagnosis and treatment, it would be valuable if elevated glycolytic metabolism could be quantified in an image in animals and humans. The pyruvate molecule is at the metabolic crossroad for energy delivery inside the cell, and with a noninvasive measurement of the relative transformation of pyruvate into lactate and alanine within a biologically relevant time frame (seconds), it may be possible to quantify the glycolytic status of the cells. We have examined the metabolism after i.v. injection of hyperpolarized (13)C-pyruvate in rats with implanted P22 tumors. The strongly enhanced nuclear magnetic resonance signal generated by the hyperpolarization techniques allows mapping of pyruvate, lactate, and alanine in a 5 x 5 x 10 mm(3) imaging voxel using a 1.5 T magnetic resonance scanner. The magnetic resonance scanning (chemical shift imaging) was initiated 24 seconds after the pyruvate injection and had a duration of 14 seconds. All implanted tumors showed significantly higher lactate content than the normal tissue. The results indicate that noninvasive quantification of localized Warburg effect may be possible.

An association between spin-lattice relaxation time and organ weight in humans

It is observed that, in humans, the lighter the weight of the organ, the higher the spin-lattice relaxation time. Similarly, smaller animals tend to have a higher oxygen consumption rate per unit of body weight than larger animals. The allometric function relationship between oxygen consumption rate against body weight of different species is similar in shape to those of the spin-lattice relaxation times in 21 normal human organs against organ weight.

Correlation between spin lattice relaxation time and radiation sensitivity in human tissues

The water proton spin lattice relaxation time of normal and tumorous tissues of human and radiosensitivity yield a linear relationship.

Primary leptomeningeal melanoma simulating a meningioma

A surgically confirmed primary leptomeningeal malignant melanoma (PLMM) discovered at the parietal region is reported in a 72-year-old male. He developed progressive right hemiparesis and speech disorders caused by a parietal large mass that simulated a growing meningioma. A well-defined, dark-black tumor was removed completely and was histopathologically diagnosed as a malignant melanoma. No melanomas were detected by systemic clinical and radiological examination, including dermatological and ophthalmologic examinations. Follow-up examination 18 months postoperatively showed no evidence of recurrence of the tumor. The patient gradually became bedridden probably because of decreased general activity possibly due to brain atrophy and died of cardiac failure without any evidence of recurrence. Because of the absence of other systemic localizations, we consider this melanoma as primary. A favorable outcome was obtained by surgical treatment alone.

New magnetic resonance imaging techniques for the detection of breast cancer

The importance of contrast agents in enhancing diagnoses from magnetic resonance images has been established in numerous cases. However, the development of a potent tissue-specific contrast agent, as a sensitive probe for early detection and investigation of the physiological characteristics of a tumor, has not yet been realized in MR imaging (MRI). In nuclear scintigraphy the technique has been demonstrated; however, the poor spacial resolution inherent to the modality and the substantial dose of radioactivity administered to the patient has hindered its widespread use. This article will review the different classes of contrast agents in MRI, with special focus on the strategies involved in the development of targeted tissue-specific MRI contrast agents for the early detection of breast cancer. The features of a new class of contrast agents for targeted MR imaging will be described. Gadolinium-containing melanin polymers (GMP's) have been synthesized as MR contrast agents in our laboratory. These GMP's demonstrate significantly higher relaxivities than any other paramagnetic contrast agents reported; consequently, they are extremely effective contrast enhancing, imaging agents by themselves. The successful coupling of these potent GMP's to a monoclonal antibody specific for breast carcinoma, the 323/A3 monoclonal antibody, suggests that in vivo tissue-specific MR imaging, at the receptor level, will become feasible in the near future.

Primary pineal melanoma: case report

Primary melanomas of the central nervous system are unusual, and those in the pineal region are exceedingly rare. We present a case of primary pineal melanoma in a 60-year-old man. The lesion was subtotally resected through an infratentorial, supracerebellar approach. The clinical features and the histological findings are discussed. Eight previous case reports are reviewed.

Double inversion recovery improves water suppression in vivo

It is shown that double inversion recovery used for water suppression can be made much less sensitive to pulse imperfections and to the variations in the relaxation times than a single inversion recovery. This insensitivity results in up to 10-fold improvement in the water suppression in vivo. The excellent water suppression by double inversion recovery is demonstrated experimentally by the in vivo proton spectra obtained from a rat brain.

Evaluation of bone marrow cellularity by magnetic resonance imaging in patients with myelodysplastic syndrome

Magnetic resonance imaging (MRI) is a safe modality for examining the bone marrow and it is quite effective in revealing marrow involvement in hematological malignancies. MRI has been compared with needle marrow biopsy in 22 patients with myelodysplastic disorders. A fairly good concordance has been demonstrated in 79% of cases. However, in 5 patients MRI revealed that bone marrow hyperplasia was not generalized. Therefore in elderly patients with MDS, MRI of the spine allows the quantification of bone marrow hyperplasia with a greater accuracy than bone marrow biopsy and this may be useful for monitoring the effect of cytostatic treatment.

Evidence for a contribution of paramagnetic ions to water proton spin-lattice relaxation in normal and malignant mouse tissues

Paramagnetic ions complexed to proteins may lose, retain, or enhance solvent paramagnetic relaxation (SPR) relative to free solution. We measured T1 and T2 of three mouse cancers, their normal counterparts, and six additional tissues. Long T1 of cancers was not caused by necrosis or by different contents of water, fat, or blood. Dissociable (TCA-extractable) and nondissociable (ashed) Mn, Cu, and Fe were measured by AA. Cancers had less Mn, Cu, and Fe than did normal counterparts. All 12 tissues had inverse correlations between T1 and dissociable Mn and Cu. For Mn alone to account for reduced T1, the extent to which SPR of the Mn-protein complexes would be enhanced is by factors of 0.6 to 13, below the maximum observed in Mn-enzymes. Different amounts of paramagnetic ion-protein complexes may account for part of the differences in T1 of water protons in different tissues, and the longer T1 of cancer cell water may be caused in part by reduced amounts of such complexes.

Volume-selective determination of the spin-lattice relaxation time in the rotating frame T1 rho, and T1 rho imaging

A method for the volume- and resonance line-selective determination of the longitudinal relaxation time in the rotating frame, T1 rho, is described. The spin-lock pulse intrinsic to the T1 rho sequence simultaneously replaces the first slice-selective pulse of the VOSY method for localized spectroscopy. This is a further parameter suitable for the local characterization of tissue. On the same basis, T1 rho can be used as a new contrast parameter for biomedical imaging purposes. An appropriate pulse sequence for T1 rho imaging is presented. Test experiments which promise some striking advantages compared with conventional magnetic resonance imaging are reported.

Deuteron field-cycling relaxation spectroscopy and translational water diffusion in protein hydration shells

The deuterated hydration shells of bovine serum (BSA) albumin, and purple membrane sheets have been studied by the aid of deuteron field-cycling relaxation spectroscopy. The deuteron Larmor frequency range was 10(3) to 10(8) Hz. The temperature and the water content has been varied. The data distinguish translational diffusion on the protein surface from macromolecular tumbling or exchange with free water. A theory well describing all dependences has been developed on this basis. All parameters have successfully been tested concerning consistency with other sources of information. The concept is considered as a major relaxation scheme determining, apart from cross-relaxation effects, the water proton relaxation in tissue.

Anatomy of the thoracic aorta: magnetic resonance imaging and interpretation of flow phenomena

The authors present the results of magnetic resonance imaging (MRI) in the investigation of the anatomy of the thoracic aorta in a group of eight volunteers and in one patient with presumptive Takayasu's disease but with normal aorta. Transaxial, coronal, sagittal and oblique slices were made and the morphologic results are presented. Major flow phenomena are also discussed and some examples given.

Application of magnetic resonance imaging and computerized tomography as an adjunct to the surgical management of soft tissue sarcomas

Magnetic resonance imaging (MRI) and computed tomography (CT) scans of 53 evaluable patients with biopsy-proven soft tissue sarcomas were reviewed and compared with operative results to ascertain the accuracy for each imaging modality to predict resectability. Location of soft part sarcomas included: abdomino-pelvic (3), retroperitoneal (7), extremity (35), and other anatomic sites (8). MRI was observed to have greater accuracy than CT to preoperatively predict resectability (96.2% vs. 75.5%, respectively, p = 0.0034) following three-dimensional, multiplanar evaluation. Further, MRI was judged to have superior sensitivity to CT (95.6% vs. 73.3%, respectively, p = 0.006) and equivalent specificity (100% vs. 87.5%, respectively, p = 0.125). MRI represents a sophisticated diagnostic imaging technique to differentiate normal tissue from soft tissue sarcomas with superior contrast resolution in multiplanar imaging. MRI is considered to be the imaging modality of choice for these tumors with the advantage of not exposing the patient to ionizing irradiation or intravenous contrast agents to delineate contiguous structures.

Magnetic resonance imaging versus computed tomography in the evaluation of soft tissue tumors of the extremities

Twenty patients with extremity soft tissue tumors were prospectively evaluated with magnetic resonance imaging (MRI) and computed tomography (CT) scans with subsequent anatomic correlation of surgical findings. MRI and CT had a similar percentage of accuracy in assessing tumor relationship with major neurovascular (80% and 70%, respectively) and skeletal (80% and 75%, respectively) structures. MRI was significantly better than CT in displaying contrast between tumor and muscle when using the T2 weighted spin echo (SE) (p2 less than 0.002) and inversion recovery (IR) (p2 less than 0.005) pulse sequences. MRI and CT were comparable in demonstrating contrast between tumor and fat. The contrast between tumor and vessel was better displayed by MRI compared with CT when using the T1 weighted SE (p2 less than 0.001) and T2 weighted SE (p2 less than 0.001) pulse sequences. T1 and T2 values were measured on fresh tumor and normal tissue samples and were used to predict relative contrast on different MRI pulse sequences using isosignal contour plots. MRI appears to offer several advantages over CT in the evaluation of extremity soft tissue tumors.

Nuclear magnetic resonance imaging and spectroscopy in experimental brain edema in a rat model

Many aspects of the use of high-resolution nuclear magnetic resonance (NMR) imaging in the examination of brain edema have not been fully explored. These include the quantitation of edema fluid, the ability to distinguish between various types of edema, and the extent to which tissue changes other than a change in water content can affect NMR relaxation times. The authors have compared NMR relaxation times obtained by both in vivo magnetic resonance imaging (MRI) and in vitro NMR spectroscopy of brain-tissue samples from young adult rats with cold lesions, fluid-percussion injury, hypoxic-ischemic injury, bacterial cerebritis, and cerebral tumor. Changes in relaxation times were compared with changes in brain water content, cerebral blood volume, and the results of histological examination. In general, both in vivo and in vitro longitudinal relaxation times (T1) and transverse relaxation times (T2) were prolonged in the injured hemispheres of all experimental groups. Water content of tissue from the injured hemispheres was increased in all groups. A linear correlation between T2 (but not T1) and water content was found. Changes in the values of T1 and T2 could be used to distinguish tumor from cold-injured tissue. Cerebral blood volume was reduced in the injured hemispheres and correlated inversely with prolongation of T1 and T2. The results of this study suggest that, in a clinical setting, prolongation of T2 is a better indicator of increased water content than prolongation of T1, yet quantitation of cerebral edema based solely upon prolongation of in vivo or in vitro T1 and T2 should be undertaken with caution.

Biphasic change of proton magnetic relaxation times during azo-dye hepatocarcinogenesis

For the first time, change in the proton longitudinal relaxation times (T1) of rat tissues has been examined throughout the whole process of azo-dye hepatocarcinogenesis. Two maxima of the T1 values were observed for liver, on Day 60 and after Day 120, and these changes correlated well with the changes in water content. The first peak was ascribed to the immature hepatocytes of hyperplastic nodules, and the second peak to the developed hepatoma cells. The significance of the change in T1 values as a preneoplastic change is discussed.

Proton NMR relaxation times in the peripheral blood of cancer patients

The proton spin lattice relaxation time (T1) of serum and leucocytes of cancer patients and normal volunteers was measured using pulsed NMR techniques. There was no statistically significant difference in the serum T1 values of cancer patients relative to normal. An increase in T1 relative to normal values was detected in the white blood cells of patients with active leukaemia. In these patients T1 fell to normal levels after the initiation of treatment. The variation of leucocyte T1 with the course of the disease for five patients having leukaemia is presented.

Cancer Detection by NMR in the Living Animal

The purpose of this paper is to review in vivo NMR experiments [1, 2] on a transplantable tumor in mice and to discuss the feasibility of using noninvasive NMR for cancer detection in humans.