Cardiac tumors and thrombus: evaluation with MR imaging

Thirty patients with a suspected cardiac or pericardial mass underwent MR imaging. Twenty-six also had two-dimensional (2D) echocardiography, and three also had CT; one patient had MR only. Overall, 18 (60%) of the 30 patients were found to have a mass lesion. The lesion was confirmed by biopsy, surgery, or unequivocal demonstration on CT, 2D echocardiography, and/or MR imaging. Fourteen of the lesions were soft-tissue or tumor masses, and four were thrombi. The findings on 2D echocardiography and MR were in agreement in 17 (65%) of 26 patients who had both studies. MR was equivocal or in error in two patients (7%), and 2D echocardiography was nondiagnostic in seven (27%). In all seven patients with equivocal 2D echocardiography, the diagnosis was made by MR. In the four patients who did not have 2D echocardiography, MR showed the mass clearly. MR imaging is useful in the diagnosis of cardiac mass lesions. It can be used effectively in addition to 2D echocardiography to increase the certainty of diagnosis, and it is useful when 2D echocardiography is equivocal or inadequate.     

Nerve sheath tumors: evaluation with CT and MR imaging.

Tumors of nerves are classified into benign (schwannoma and neurofibroma) and malignant nerve sheath tumors. Schwannomas almost always occur as solitary lesions, whereas neurofibromas may occur alone or in a greater number, especially in patients with the peripheral form of von Recklinghausen's disease. Benign nerve sheath tumors often present as asymptomatic, slowly growing soft tissue masses. Although malignant nerve sheath tumors are relatively rare, a sudden increase in the size of a lesion, in particular in a patient with neurofibromatosis, should raise the suspicion of malignant change. On computed tomography (CT) and magnetic resonance imaging (MR) a benign nerve sheath tumor usually appears as a well-defined, oval, spherical or fusiform mass with smooth borders and distinct outlines, located in the subcutaneous tissue or centered at the expected anatomic location of a nerve, with displacement of adjacent soft tissues. Generally nerve sheath tumors have a low density on unenhanced CT scans. On MR they are isointense to muscle on T1-weighted images, whereas on T2-weighted images the signal intensity is high. Both on CT and MR the degree of contrast enhancement is moderate to marked and may be homogeneous or inhomogeneous. MR has become the method of choice for evaluating the anatomic location, contour, and relation of a nerve sheath tumor to adjacent neural, vascular, and muscular structures. The imaging criteria for malignant nerve sheath tumors are not specific enough to distinguish them from other malignant soft tissue tumors, so that neither CT nor MR can establish a definite diagnosis.     

Prospective evaluation of pancreatic tumors: accuracy of MR imaging with MR cholangiopancreatography and MR angiography

PURPOSE: To prospectively assess accuracy of magnetic resonance (MR) imaging, MR cholangiopancreatography (MRCP), and MR angiography in patients suspected of having pancreatic tumors. MATERIALS AND METHODS: Sixty-six patients suspected of having pancreatic tumors underwent MR imaging (unenhanced and contrast material-enhanced MR, MRCP, and contrast-enhanced MR angiography). Two blinded readers prospectively analyzed the images by consensus, and results were correlated with surgery, biopsy, or follow-up findings. Results were tabulated in two-by-two tables. RESULTS: MR assessment of pancreatic lesion status (differentiation of benign vs malignant) resulted in 60 correct diagnoses (accuracy, 91%), and six (10%) false diagnoses. Among histologically proved malignant tumors, MR imaging yielded correct diagnoses in 42 of 44 patients (sensitivity, 95%; 95% CI: 85%, 99%), whereas 18 of 22 patients with benign findings were classified correctly. At MR imaging, findings in four patients with chronic pancreatitis were wrongly categorized as malignant tumors (specificity, 82%; 95% CI: 60%, 95%), and in one patient, a distal common bile duct carcinoma was not detected. In no patient with pancreatic adenocarcinoma was this tumor misdiagnosed as benign. In patients with malignant tumors who underwent resection, local-regional tumor growth and vascular infiltration were accurately classified in 89% and 94%, respectively. MR imaging depicted histologically proved synchronous hepatic metastases in 82%. The positive and negative predictive values for cancer nonresectability were 90% and 83%, respectively, and the accuracy, sensitivity, and specificity were 85%, 69%, and 95%, respectively. CONCLUSION: Unenhanced and contrast-enhanced MR imaging with MRCP and MR angiography offers potential as a noninvasive tool for assessment of patients suspected of having pancreatic tumors.     

Recurrent glomus tumors of fingertips: MR imaging evaluation

PURPOSE: To determine the magnetic resonance (MR) imaging findings in recurrent glomus tumors of the fingertips. MATERIALS AND METHODS: Twenty-four consecutive patients with recurrent pain after previous excision of a glomus tumor of the fingertip underwent MR imaging studies and surgery. T1-weighted spin-echo MR images were obtained in each patient before and after intravenous injection of contrast material; T2-weighted spin-echo and three-dimensional gradient-recalled echo images were also obtained. MR angiography was performed in four patients. Postsurgical histopathologic analysis revealed recurrent glomus tumors in 22 patients. Signal intensity, enhancement, and margins of the scar tissue and the recurrent tumors at MR were assessed. RESULTS: The postsurgical scars were depicted in 21 (88%) of 24 patients with all sequences but were best demonstrated on gradient-recalled echo MR images. Seven patients had undergone multiple surgical procedures and had extensive scar tissue and, in one case, a neuroma. In all patients, MR imaging revealed a nodule compatible with the diagnosis of a recurrent glomus tumor. In 13 (54%) of 24 patients, the nodule had typical features of a glomus tumor. In eight (33%) of 24 patients, the tumors had low signal intensity or isointensity compared with the nail bed on T2-weighted images. In six (25%) of 24 patients, the tumors had faint enhancement after intravenous gadolinium chelate administration. The margins of the tumors were blurred by scar tissue in nine of 24 cases. CONCLUSION: MR imaging can aid in the evaluation of recurrent glomus tumors.     

Brain tumors: MR imaging with gadolinium-DTPA

Magnetic resonance (MR) imaging was performed on 40 patients with intracranial tumors, before and after intravenous administration of gadolinium-DTPA (Gd-DTPA). Precontrast studies included a comprehensive protocol of spin-echo sequences. Tumors were visualized on precontrast images either directly or indirectly by anatomic distortion caused by the mass. However, differentiation of the tumor from adjacent tissues was possible in only 17 of 40 cases. Delineation of the tumor was best on precontrast, T2-weighted images. After administration of Gd-DTPA (0.1 mmol/kg), increased signal intensity from the tumor was observed in all patients. The localized increase in signal intensity in the tumor considerably improved the tumor delineation in 36 of 40 patients. Whereas most of the meningiomas, neuromas, and adenomas could be delineated prior to administration of contrast material if appropriate pulse sequences were applied, glioblastomas and intracranial metastases required Gd-DTPA administration for diagnostically sufficient tumor display.     

Soft-tissue tumors: MR imaging

We evaluated the suspected soft-tissue masses of 33 patients using magnetic resonance (MR) imaging. Thirty-two masses were defined, of which ten were malignant and 22 were benign. Specific characteristics that would allow us to distinguish the benign lesions from the malignant ones could not be identified on MR imaging. Lesions located within muscles or in the intramuscular septa were best seen with T2-weighted imaging sequences; those located within the subcutaneous fat were best outlined with T1-weighted imaging sequences. Both imaging sequences were necessary to provide the complete representation of the extent of the mass. We performed comparison studies using computed tomography (CT) in 24 of the cases. Of 92 possible comparisons and in four categories MR imaging yielded results that were superior to those obtained by CT scanning in 30 instances, equaled the results obtained by CT scanning in 62 instances, but never yielded results inferior to those obtained by CT scanning. However, MR imaging failed to demonstrate soft-tissue calcification and soft-tissue gas in one case each.     

Parotid tumors: MR imaging with pathological correlation

Most parotid tumors grow slowly, whether benign or malignant; thus, it is difficult to predict the malignant or benign nature of a tumor clinically. Magnetic resonance imaging may have a place in the diagnostic work-up of parotid tumors. The purpose of this article is to illustrate the MR imaging findings of parotid tumors and to correlate them to pathologic findings. The MR imaging may be helpful in differentiation of benign and malignant tumors of the parotid gland, and can provide important clues in the diagnosis of their histologies.     

Venous clots: evaluation with MR imaging

In vitro and in vivo studies were performed to determine the proton relaxation and imaging characteristics of static blood and acute and organized clot in canine jugular veins. In vivo, it was found that two inversion recovery sequences using a short inversion time (100 msec) demonstrated better differentiation of signal intensity of intravascular clot from surrounding soft tissues than did standard T1- and T2-weighted sequences. In vitro, quantitative measurements showed marked reduction of both T1 and T2 relaxation time of acute clot compared with stagnant blood. In addition, the T1 relaxation time, and to a lesser extent the T2 relaxation time, shortened as the clot aged, indicating a potential role for magnetic resonance imaging in determining the age of venous thrombi.     

Gallbladder carcinoma: evaluation with MR imaging

Magnetic resonance (MR) images of 19 patients with histologically proved gallbladder carcinoma were retrospectively reviewed to determine the appearance of the primary tumor, and to assess the ability of MR imaging to demonstrate the various modes of tumor spread beyond the gallbladder. The primary tumor, as well as tumor spread beyond the gallbladder, was hyperintense on T2-weighted images and hypointense on T1-weighted images when compared with the liver parenchyma. Liver invasion and metastasis could be depicted by MR imaging with both sequences, unless the tumors were small or the extent of invasion was minimal. Duodenal invasion was difficult to evaluate because of motion artifacts, paucity of fat, and partial volume effects. T1-weighted images readily demonstrated extension of the tumor to the hepatoduodenal ligament and para-aortic region with good contrast between tumor and surrounding tissue. The extent of tumor extension to the blood vessels was also easily evaluated because of flow void in the vasculature. MR imaging can help determine the extent of gallbladder carcinoma and can contribute to the staging of this disease.     

Wallerian degeneration: evaluation with MR imaging

Twenty-three patients who underwent routine magnetic resonance (MR) imaging of the brain were found to have signal or structural abnormalities corresponding to white matter tracts. Images were evaluated for anatomic and MR signal characteristics of the involved tract, associated primary lesions, and, when possible, changes in MR signal and anatomic structures with time. Images from 20 patients demonstrated a thin band of abnormal signal contiguous with the primary lesion and conforming to the known anatomic pathway of a white matter tract. Cerebral infarction was the most common associated primary disorder (n = 17). Neoplasms (n = 2), demyelinating (n = 1) and posthemorrhagic (n = 2) conditions, and an idiopathic movement disorder (n = 1) were associated with white matter tract signal abnormalities that were indistinguishable from those seen with infarction. Signal abnormality corresponding to the corticospinal tract was the type most commonly seen. No change in signal characteristics was seen with time (six cases) or following contrast material administration (two cases). The authors conclude that MR imaging provides a sensitive method of evaluating wallerian degeneration in the living human brain.     

Galactosemia: evaluation with MR imaging.

The cerebral findings at magnetic resonance imaging in 67 transferase-deficient galactosemic patients (36 female, 31 male; median age, 10 years) are reported. Twenty-two patients had mild cerebral atrophy, eight had cerebellar atrophy, and 11 had multiple small hyperintense lesions in the cerebral white matter on T2-weighted images. The classic galactosemic patients (those without measurable transferase activity) older than 1 year of age did not show the normal dropoff in peripheral white matter signal intensity on intermediate- and T2-weighted images. The authors postulate that this abnormal signal intensity is due to altered myelin formation secondary to the inability to make sufficient and/or normal galactocerebroside.     

Periventricular leukomalacia: evaluation with MR imaging

We reviewed 24 magnetic resonance (MR) images of 12 infants diagnosed as having periventricular leukomalacia based on ultrasound results. Abnormalities were identified on the MR images of every patient and were divided into three categories: distribution of low-signal-intensity areas within the cerebral white matter, degree of ventriculomegaly and brain atrophy, and extent of myelination. Follow-up examinations on six patients were also compared for significant changes. Abnormalities noted on MR images that most consistently related to poor outcome for the patient were low-signal-intensity lesions involving all four cerebral lobes, moderate to severe delays in myelination, lack of progression of myelination, and moderate to severe cortical atrophy. MR imaging was able to depict the extent and progression of myelination, and it may be used to continue follow-up of these patients beyond the time of fontanel closure.     

Shoulder instability: evaluation with MR imaging

Instability of the glenohumeral joint is a common cause of chronic shoulder pain and disability. One or more episodes of subluxation or dislocation may result in a tear, detachment, or attenuation of the glenoid labrum, stripping of the joint capsule from the scapula, or trauma to the tendons or muscles of the rotator cuff. A series of 27 shoulders examined with magnetic resonance (MR) imaging showed changes of glenohumeral instability, which were confirmed with open or arthroscopic surgery. MR imaging was capable of displaying common types of pathologic conditions resulting from instability, including labral trauma, capsular detachment, and retraction of the subscapularis muscle. MR imaging is a valuable diagnostic tool for the evaluation of glenohumeral instability.