Nuclear magnetic resonance imaging of a fibrosarcoma tumor implanted in the rat

Gadolinium-DTPA Enhancement of Experimental Soft Tissue Carcinoma and Hemorrhage in Magnetic Resonance Imaging

An experimental series in the rabbit was performed to test gadolinium-DTPA (Gd-DTPA) enhancement of VX-2 carcinoma and hemorrhages induced in the soft tissues. The recognition of both malignant and benign lesions was greatly facilitated on T1 weighted images after intravenous administration of 0.3 mmol Gd-DTPA/kg body weight because of reduced T1 relaxation times. Gd-DTPA enhancement reached its maximum after 10–15 minutes and was most apparent in tumor tissue, connective tissue surrounding the tumor and in the area of fresh hemorrhage.

Magnetic resonance imaging: comparison of four pulse sequences in assessing primary bone tumours

A prospective magnetic resonance imaging (MRI) study was carried out in 13 patients (19 examinations) with primary bone tumours to assess the relative value of each of four pulse sequences in showing the extent and nature of the lesion. The four pulse sequences used were a T1-weighted spin-echo (SE544/44), a T2-weighted spin echo (SE1500/80), a short TI inversion recovery (STIR) (IR500/100/44), and a partial saturation (PS) (PS500/22) with field echo data collection. For soft tissue disease the combination of PS and STIR gave better definition of the boundary of the tumour than the more conventional T1 and T2-weighted spin echo sequences. For the demonstration of bone cortex, periosteal change and calcification, T1 and T2-weighted spin echo sequences were better. However, for calcified tissues, plain radiographs were better than either MRI combination. On the assumption that plain films will be available in all cases, PS and STIR sequences could therefore be substituted for T1 and T2-weighted spin echo sequences allowing an increase in soft tissue detectability for lesions in both red and yellow marrow.

Magnetic resonance imaging (MRI): a new tool in experimental toxicologic pathology

Magnetic Resonance Imaging (MRI) is a noninvasive imaging technique that provides multidimensional images of the soft tissues of the body. This imaging technique has proven to be an excellent diagnostic and experimental tool for the detection of pathologic alterations in soft tissues, as well as an adjunct screening method for following the genesis, progression, or regression of chemically induced lesions in the same live animal. Future applications of MRI technology in small animals include MRI microscopy, mapping of vascular or circulatory alterations, measurement of perfusion and diffusion rates of body fluids, and acquisition of cell metabolic states in combination with Nuclear Magnetic Resonance (NMR) spectroscopy, all of which will contribute immensely to the advancement of toxicologic and biomolecular research.

Magnetic resonance imaging in pediatric hematology/oncology. Part I. Basic technology

Magnetic resonance imaging (MRI) is a promising new diagnostic modality that is well suited for the evaluation of children with hematological or oncological diagnosis. The side effects of ionizing radiation are avoided, the tomographic pathological anatomy in three orthogonal planes can be obtained, and differences between normal and abnormal tissues are often present. In order to present our preliminary clinical experience with MRI in pediatric hematology and oncology, the historical background of MRI, the technique, and possibilities for tissue characterization are reviewed.

Magnetic resonance imaging of the musculoskeletal system

During the last few years, the interest and experience in magnetic resonance imaging (MRI) of the musculoskeletal system has increased rapidly. Modern equipment with good spatial resolution and multislice, multiecho technique provides detailed information on the joints, soft tissue and spine within a reasonable examination time, both with superconductive and resistive systems. Today, MRI is an established technique for examination of musculoskeletal tumors and aseptic bone necrosis and it has proven to be of great value for evaluation of diseases of the spine and spinal canal. The definite place of MRI within musculoskeletal diagnostic imaging is not yet settled, but its potential is great, and it will have an important role in the future.

Nuclear magnetic resonance in oncology

The application of nuclear magnetic resonance (NMR) techniques to the diagnosis of cancer was first explored by Damadian, who proposed that benign and malignant tissues could be differentiated on the basis of characteristic differences in spin-lattice and spin-spin relaxation times (T1 and T2) as determined in vitro with NMR spectrometers. Damadian's thesis was very controversial and never gained widespread acceptance. Not all investigators were able to confirm his findings. Moreover, it was improbable that NMR would ever play an important role in the diagnosis of malignancy as long as biopsy was necessary to obtain material for analysis. However, the potential usefulness of NMR in oncology was enhanced considerably by the work of Lauterbur, who showed that NMR signals could be spatially encoded to produce images of the examined object. NMR imaging has made feasible the measurement of the T1 and T2 of lesions without biopsy. Unfortunately, initial efforts at characterizing tissues by in vivo determination of proton relaxation times have yielded disappointing results. Nonetheless, NMR imaging will be a powerful tool for evaluating patients with malignant disease because of the unique anatomic information it can provide without exposure of the patient to ionizing radiation. In vivo NMR spectroscopy of 31P and other sensitive nuclei may add a new dimension to clinical and experimental oncology.

Tumor of the heart diagnosed by magnetic resonance imaging

A case of liposarcoma metastatic to the heart is presented. This is a very rare entity and only three prior case reports could be found. Magnetic resonance imaging was successfully used to visualize the tumor. These images compared favorably with a two-dimensional echocardiographic study and postmortem examination.

Magnetic resonance imaging of bone and soft tissue tumors: early experience in 31 patients compared with computed tomography

In 31 patients with 21 soft tissue and 10 bone tumors, magnetic resonance imaging (MRI) and computed tomography (CT) were equally effective in delineating the margins of most soft tissue tumors, and the margins of bone tumors from fat and adjacent normal bone. However, MRI was superior to CT in delineating bone tumors from adjacent muscle, and in showing the relationships to bone of the deep margins of some soft tissue tumors. This was true because the quality of CT images around thick cortical bone often was severely degraded by streak artifact, which does not occur in MRI. Excellent anatomic detail was achieved on MRI by spin echo pulse sequences with short repetition times. Bone tumors were delineated best by spin echo 1000/30 images, and soft tissue tumors by spin echo 1000/30 or inversion recovery images.

Limitations of computed tomography following excisional biopsy of soft tissue sarcomas

Twenty-one patients were evaluated by computed tomography (CT) following complete or incomplete excisional biopsy of soft tissue sarcomas. Since the surgical margins were inadequate, additional treatment was required, and CT was intended to identify and delineate any residual tumor. Thirteen patients had no palpable mass in the operative area. In these, eleven CTs showed no tumor, but microscopic tumor was found in seven. The other two CTs showed masses, but both proved to be hematomas. Eight patients had palpable masses and seven proved to be residual tumor. Of these, two CTs failed to show the residual tumor. Five CTs correctly identified residual tumor, but two of them failed to show the entire tumor extent. Computed tomography did not correctly predict the presence or absence of microscopic residual tumor when there was no palpable mass, and was at least partly inaccurate in delineating residual tumor in four of eight patients with palpable masses.

Magnetic resonance. Principles and applications

Magnetic resonance is a unique, noninvasive imaging modality which allows direct, multiplanar imaging and the possibility of obtaining biochemical information in vivo. Presently, MR appears most applicable to the evaluation of central nervous system abnormalities. The high sensitivity of MR in the evaluation of intracranial pathology suggests that it may eventually replace CT for many suspected diseases, if future investigations are able to improve its specificity. As previously noted, MR may be more diagnostic than other radiologic studies in the evaluation of suspected Chiari malformation, syringomyelia, congenital abnormalities, tumors of the spinal axis, and disc space infection. In the chest, MR appears to be more accurate than CT in the determination of the extent of mediastinal tumor, but at present cannot replace CT because of the lack of experience in imaging parenchymal nodules and benign diseases. MR of the breast is promising, but the size of the lesion may prove to be a limiting factor with magnetic field strengths commonly being utilized. There are inherent difficulties in the evaluation of cardiac disease with MR, but it offers a noninvasive method of investigating congenital heart disease and may provide valuable information in suspected myocardial ischemia and altered cardiac function. MR provides a new method of evaluating the vascular system, both in terms of providing anatomic information on large and medium-sized vessels and flow analysis. In the abdomen, MR appears to be most sensitive in the evaluation of suspected hepatic masses, but as with the brain, greater specificity will be needed to replace CT. At the present time, MR offers no distinct advantage over conventional imaging modalities in the evaluation of pancreatic disease, it maybe more accurate than CT in the staging of renal cell carcinoma. Larger studies are needed to determine the role of MR in the investigation of retroperitoneal adenopathy and adrenal abnormalities. In the pelvis, MR offers the hope of earlier diagnosis of prostatic carcinoma and may replace CT for staging of prostatic carcinoma and transitional cell carcinoma of the bladder. Limited MR experience with benign disease of the female pelvis suggests that it is currently more accurately evaluated with ultrasound. MR appears to be highly sensitive and specific for the diagnosis of avascular necrosis and may provide an early clue in suspected osteomyelitis. Finally, in vivo MR spectroscopy may provide unique metabolic information that was unobtainable prior to the advent of magnetic resonance, if this proves to be technically feasible.

Measurement of spin-lattice relaxation times in double spin-echo imaging

Calculation of tissue T1 in double spin-echo imaging (90 degrees-T-180 degrees-2T-180 degrees) using two repetition times (b1 and b2) has entailed an approximation that ignores the two 180 degrees pulses. The theoretical consequence of the simplification is to overestimate T1 with a fractional error that increases with increasing T1 faster than linearly in a manner dependent on the sequence parameters. With b1, b2, and T as parameters, the theory gives a family of curves relating T1 to the predicted ratio of signals acquired at b2 versus b1 intervals. Tissue T1 can be determined from the observed signal ratio with no approximation. Consideration of noise effect on the precision of T1 so determined favors the use, within limits, of higher b2/b1 ratio for the same b1 + b2 time. At constant b2/b1, using longer b1 + b2 permits wider range of T1 to be measurable with a specified minimum precision.