Magnetic resonance appearance of fibromatosis. A report of 14 cases and review of the literature.

We reviewed retrospectively the magnetic resonance (MR) images of 14 soft-tissue lesions of fibromatosis (desmoid tumors) encountered in 11 patients. The lesions were typically inhomogeneous in texture and round to oval in configuration. Margins were well-defined in 78% of the lesions at presentation and were infiltrating in all recurrences. On T1-weighted spin echo MR images, the predominant signal intensity was either isointense or minimally hyperintense when compared with skeletal muscle. On T2-weighted MR images the predominant signal intensity was typically intermediate between skeletal muscle and subcutaneous fat or isointense to fat. Linear and curvilinear areas of decreased signal intensity were distributed throughout the lesions on both pulse sequences in 86% of cases. This pattern strongly suggested fibromatosis. Speculation concerning possible etiologies of this appearance are discussed, and the relevant literature on previously reported cases is reviewed.

MR appearance of fibrous dysplasia.

Magnetic resonance (MR) imaging is utilized in diverse clinical circumstances for evaluation of the musculoskeletal system. Consequently, common benign skeletal lesions may be detected incidentally following MR scan obtained for unrelated reasons. The spectrum of MR appearances of fibrous dysplasia has not been previously reported. We retrospectively reviewed all radiologic images (including the MR scans) of 11 sites of fibrous dysplasia encountered in seven patients. On MR, the fibrous dysplastic lesion causes an "expanded" bony contour and is characterized by decreased signal on T1-weighted image. The signal on T2-weighted MR scan is variable, however. Since fibrous dysplasia is a (relatively) common skeletal lesion that can be encountered incidentally, all radiologists should be familiar with its MR appearance. Furthermore, in the unlikely possibility of surgical intervention, MR is useful in determining the extent of disease within the affected bone and planning the preoperative strategy.

Soft-tissue masses: diagnosis using MR imaging.

The MR images of 112 soft-tissue masses of various causes were retrospectively reviewed. Pathologic diagnosis by biopsy was available in 96 cases. Diagnosis in the remaining 16 cases was established by characteristic radiographs, CT scans, and/or arteriograms, in conjunction with appropriate history and clinical follow-up. All masses were evaluated with both T1-weighted, 300-600/20-30 (TR/TE), and T2-weighted, 2000/80-100, images. They were reviewed to determine (1) if these images were sufficiently unique to allow a preoperative diagnosis based exclusively on the MR appearance and (2) if benignity vs malignancy could be predicted on the basis of the analysis of the MR image characteristics of the lesion. Concerning the latter, attention was directed to the margins of the lesions, to the impact of the lesion on the surrounding tissues (edema, infiltration, etc.), and to the intensity and homogeneity of the MR signal of the lesion. MR images were sufficiently characteristic to allow a specific diagnosis in 27 (24%) of the 112 cases (10 lipomas, eight hemangiomas, six pigmented villonodular synovitis, two hematomas, and one arteriovenous malformation). MR was incapable of reliably distinguishing between benign and malignant soft-tissue tumors.

Valvular regurgitation: dynamic MR imaging.

Cine magnetic resonance (MR) imaging is a new technique that combines short repetition times, limited flip angles, gradient refocused echoes, and cardiac gating. This technique has a temporal resolution of up to 32 time frames per cardiac cycle and accentuates signal from flowing blood. Cine MR images of 56 valves in 27 patients were evaluated and compared with either Doppler echocardiograms or cardiac catheterization images. An area of decreased signal that correlated spatially and temporally with regurgitant blood flow was seen in all instances in which valvular incompetence was demonstrated on either Doppler echocardiograms or cardiac catheterization images (20 valves). This abnormality was seen in nine of 36 cases without valvular incompetence. Cine MR imaging may be sensitive to turbulence and thus sensitive to valvular regurgitation.

MR appearance of fibroxanthoma.

Magnetic resonance images of nine patients with 10 fibroxanthomas of bone were retrospectively reviewed. Eight of 10 lesions were characterized by a markedly decreased signal of both T1- and T2-weighted pulse sequences. This pattern of decreased signal intensities, when present, proved distinctive and has not been observed in other nonossified primary bone lesions. Possible etiologies for this observation are discussed.

Cine MR determination of left ventricular ejection fraction.

Cine MR imaging provides tomographic images of the heart with both high spatial and high temporal resolution. As many as 32 images per cardiac cycle can be acquired with up to four separate anatomic slices and a total imaging time of 128 cardiac cycles. End-diastolic and end-systolic volumes were determined in 11 patients, and ejection fractions were calculated. The results correlated linearly with those from cardiac catheterization (correlation coefficient of .88). We conclude that cine MR imaging can be used to obtain quantitative information about the heart and has the potential to become a valuable noninvasive means of cardiac evaluation.

Two-second MR images: comparison with spin-echo images in 29 patients.

MR images can be obtained with a 2-sec scan time when an extremely short repetition rate (22 msec), limited flip angle (30 degrees), and gradient refocused echoes are used. Comparison of 415 such images obtained in 29 patients with routine T1-weighted (TR 500, TE 25) and T2-weighted (TR 2000, TE 80) images showed that images free of respiratory artifacts could be obtained in all patients. Although abdominal organs were well seen with 2-sec scan time, overall evaluation of these organs was better on routine T1-weighted images. Vascular structures, however, were seen as well or better on the 2-sec images in 60% of cases. The images were extremely sensitive to field nonhomogeneity, and metallic artifact was exaggerated in five patients with surgical clips. Two-sec MR images provide a rapid method of localizing abdominal organs for further evaluation. The sensitivity to blood flow may assist in the assessment of vascular patency.

Evaluation of steady and pulsatile flow with dynamic MRI using limited flip angles and gradient refocused echoes.

Magnetic resonance imaging sequences utilizing limited flip angles and gradient echoes yield rapid (less than 2 min) dynamic images of the cardiovascular system. These images contain both accurate anatomical and functional information. Using a gradient refocused acquisition in the steady state (GRASS) in the CINE mode, we studied the relationship between gradient echo signal intensity and velocity of steady and pulsatile flow in a phantom simulating medium to large vessels. Images were acquired on a 1.5 Tesla system (repetition time = 21 ms, echo time = 12 ms, flip angle = 30 degrees). Data from each pulse interval were sorted in 16 images. Signal intensities from flow tube lumina and surrounding stationary water jacket were used to calculate contrast ratios which were compared to velocity measurements made with electromagnetic (EM) flow probes outside the magnet room. During steady flow, signal intensity contrast ratios increased with increasing flow and in a 10 mm thick slice, reached a peak at 48 cm/s, and declined for velocities up to 90 cm/s. Changes in instantaneous velocity during pulsatile flow correlated well (r greater than .88) with signal intensity changes up to a maximum mean velocity of 17 cm/s. Total signal intensity from the lumen for an "R to R" interval correlated extremely well (r greater than .97) with mean pulsatile flow velocities up to 30 cm/s. The excellent correlation between gradient echo signal intensity and actual flow velocities suggests that this imaging sequence might be useful for evaluating normal and pathologic flow phenomena.

Asymptomatic total hip prosthesis: natural history determined using Tc-99m MDP bone scans.

A prospective study was performed with 97 patients who had undergone total hip replacement surgery and who were not experiencing pain or other symptoms or problems. The study was intended to determine the normal postoperative appearance of radionuclide scans of the hip following administration of technetium-99m methylene diphosphonate. Five areas of the prostheses were evaluated. Results showed that 6 months after implantation activity around the lesser trochanter and prosthesis shaft became insignificant. Activity around the acetabulum, greater trochanter, and prosthesis tip stabilized approximately 2 years after surgery; approximately 10% of patients in the study had persistent activity in these areas. Familiarity with this normal progression is fundamental to interpretation of postoperative bone scans in patients with total hip prosthesis.

MRI with surface coils for parathyroid tumors: preliminary investigation.

The ability of MRI to detect parathyroid gland enlargement was assessed using 1.5-T systems and surface coil reception. Nine patients with primary hyperparathyroidism were studied before surgical neck exploration. Five-millimeter-thick axial images were obtained from the thyroid cartilage to the sternal notch. Both T1 and T2 contrast-weighted spin-echo sequences were performed in most cases. MRI correctly identified six out of seven parathyroid adenomas. In the false-negative case, T2 contrast-weighted sequences were not performed for technical reasons. In the one case of surgically proven parathyroid hyperplasia, a lesion identified by MRI as a parathyroid adenoma coincided at surgery with the largest of three hyperplastic parathyroid glands. A single case demonstrated a potential pitfall in the search for ectopic parathyroid glands: A large colloid cyst in the posterior portion of the thyroid gland showed signal characteristics indistinguishable from a parathyroid adenoma. The enlarged parathyroid glands were best visualized on T2 contrast-weighted sequences, with the lesions demonstrating greater signal than surrounding tissues.

Hepatoma visualization with Tc-99m pyridoxylidene glutamate.

Tc-99m sulfur colloid is concentrated in Kupffer cells of the liver, whereas the new biliary agents are processed by hepatic parenchymal cells. A case of primary hepatocellular carcinoma, appearing as a defect on sulfur-colloid liver scan and visualized on a biliary scan, is presented. The possible role of biliary scanning in the evaluation of a defect on sulfur-colloid liver scan is discussed.

Radionuclide imaging in the assessment of lung injury.

Nuclear medicine imaging techniques are being more widely applied to study a variety of lung injuries. Ventilation and perfusion imaging is often superior to other roentgenographic techniques for establishing the diagnosis and demonstrating the extent of such injuries. At several large burn centers, the Xe-133 washout technique has become the cornerstone for diagnosing early inhalation injury. The overall accuracy of this procedure is 92%. Regional decreases in ventilation and perfusion can reliably localize aspirated radiolucent foreign bodies. Disproportionate perfusion changes are often the earliest indicator of radiation pneumonitis and other forms of vascular injury. Other types of injury, such as gastropulmonary aspiration, blunt trauma, and near-drowning, require further evaluation before the ultimate role of nuclear imaging is defined. An imaging technique to assess capillary permeability in the adult respiratory distress syndrome would be of great clinical benefits.