MRI assessment of unsuspected dural sinus thrombosis.

In three patients with clinically unsuspected diagnosis, MRI has afforded a positive and conspicuous demonstration of dural sinus thrombosis, allowing specific treatment and followed by improvement in the patients' condition. Even in retrospect, CT examinations were nondiagnostic. Presenting symptoms were usual and nonspecific. CT and radionuclide scanning have proved valuable when performed on a clinically oriented basis. Angiography cannot be carried out without clear indications. MRI offers advantages in being a non-invasive technique without ionising radiation, allowing direct visualization and accurate delineation of the thrombus. MRI is definitely the method of choice to assess clinically suspected cerebral venous occlusion. As MRI diagnosis relies on a routine examination protocol, we believe that it will detect other unsuspected cases of dural sinus thrombosis.

Prostatic carcinoma: staging by clinical assessment, CT, and MR imaging.

The sensitivity, specificity, accuracy, and positive and negative predictive values of clinical assessment, computed tomography (CT), and magnetic resonance (MR) imaging were compared in the differentiation of stage B from stage C prostatic carcinoma. Forty-six patients who had undergone radical prostatectomy were included in the study. Surgical-pathologic staging was considered the "truth measure." Clinical staging had an accuracy of 61%, and CT, 65%. Accuracy for MR imaging depended on the instrument parameters and plane of section used. When only transverse T1-weighted images were analyzed, MR accuracy was 61%. However, when transverse T1- and T2-weighted images supplemented by additional T2-weighted coronal or sagittal images were studied, accuracy increased to 83%. At present, MR imaging is the most accurate diagnostic modality for the local staging of carcinoma of the prostate, but for optimal results, multiple sequences and two orthogonal planes of imaging are needed.

MR imaging of the prostate gland: normal anatomy.

MR images of the male pelvis in 55 subjects were analyzed retrospectively for depiction of the zonal anatomy of the prostate gland as related to different repetition (TR) and echo (TE) times, slice thickness, plane of imaging, chronologic age of the patient, and different magnetic field strengths. With imagers operating at 0.35 and 1.5 T, T2-based tissue-contrast images were needed for the demonstration of the internal anatomy of the prostate gland. The display of zonal anatomy was improved when continuous 0.5-cm slices were used. Evaluating sequential sections, the peripheral, central, and transition zones could be differentiated. The peripheral zone showed higher signal intensity than either the central or transition zone and was discerned in the coronal, sagittal, and transverse planes. The central zone was of low signal intensity and was well displayed in the coronal and sagittal planes. The central zone was seen in 31 of the 32 young men (aged 25-35 years) but in only eight of the 23 older men (aged 40 years and older). The transition zone had intrinsic MR parameters similar to the central zone, and the two could be distinguished from each other only by the knowledge of their respective anatomic location. The low-intensity transition zone blended with the periurethral glands and the preprostatic sphincter. The transition zone was of homogeneous low signal intensity in young men but varied in size and signal intensity in older men. Such a detailed display of the prostate zonal anatomy offers a unique potential for the evaluation of prostatic physiology and disease.

Evaluation of prostate size: a comparison of ultrasound and magnetic resonance imaging.

To determine the relative accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) in the evaluation of prostate volume, we compared US and MR images with surgical findings in 15 patients. Transabdominal US was excellent for determining prostate size in patients with small to moderate enlargement. When compared with surgical specimens, the difference between the weight of the gland as predicted by US and the actual weight was 14% (SD +/- 12). With the transabdominal approach, the length was often inaccurately imaged, but the addition of transrectal scans in the sagittal projection improved results: with combined transabdominal and transrectal US, the average difference in weight was 8% (SD +/- 7). The MRI more accurately predicted prostatic volume (average difference, 6% (SD +/- 6), but the difference between the latter 2 is not significant. In 5 additional patients who had undergone transurethral resection of the prostate, residual prostatic tissue was evaluated by MRI and US. In addition to demonstrating prostate size, transrectal sagittal US showed the relationship among the bladder neck, prostatic urethra, and remaining prostatic tissue. Real-time US also allowed evaluation of dynamic sphincteric contractions, which is a finding not available today with MRI. Tissue differentiation was attempted with both MRI and US. Neither imaging modality could differentiate benign from malignant disease.

The potential of magnetic resonance imaging for the evaluation of thoracic arterial diseases.

Fifty-three patients with a variety of thoracic aortic or pulmonary arterial diseases were evaluated by magnetic resonance imaging to determine the potential of this new technique for the diagnosis of thoracic vascular disease. Direct visualization of the atherosclerotic plaques and demonstration of their precise location and extent was achieved by magnetic resonance imaging. The size and extent of the aneurysms and the presence of mural thrombus were demonstrated by magnetic resonance imaging. Magnetic resonance imaging identified the intimal flap and indicated the proximal extent of thoracic aortic dissection. Magnetic resonance imaging permitted direct visualization of thrombi and aneurysm of the pulmonary arteries. In conclusion, magnetic resonance imaging appears to be a totally noninvasive and reliable technique for demonstration of various pathologic processes involving the thoracic aorta and pulmonary arteries. Vascular imaging is achieved without the need for contrast media.

The diagnostic value of renal cortex-to-medulla contrast on magnetic resonance images.

The diagnostic value of magnetic resonance contrast between the renal cortex and renal medulla as an indicator of renal disease was retrospectively studied in 38 patients (ten patients with a variety of diseases affecting the renal parenchyma, nine with renal obstruction, four with diffusely infiltrating renal-cell carcinoma, one with renal hematoma, nine with normally functioning renal allograft, and five with renal allograft failure). Twelve normal volunteers served as controls. On spin-echo (SE) images (TR 0.5 sec, TE 28 msec), the cortex-to-medulla contrast was present in the kidneys of all the normal volunteers (19% contrast +/- 2% S.D.) and in all the normally functioning allografts (17% contrast +/- 2% S.D.). Decrease or absence of cortex-to-medulla contrast (SE image with TR 0.5 sec and TE 28 msec) was found to be a sensitive but nonspecific sign of renal disease. It occurred in renal diseases of various causes and was produced by different pathophysiologic mechanisms such as edema, scarring, and tissue replacement by neoplasm or hematoma. Of the calculated T1 and T2 relaxation times and spin density of the cortex and the medulla, the T1 changes most consistently reflected renal disease.

MR imaging of cardiac thrombi.

This retrospective study of 10 magnetic resonance (MR) examinations in patients with cardiac thrombi (eight in left ventricle and two in right atrium) was performed to assess the ability of MR for demonstrating cardiac thrombi and describe the appearance of cardiac thrombi using the spin echo technique. Cardiac thrombi usually had higher signal intensity than the normal myocardium on MR imaging, especially on the second echo (TE of 56 or 60 ms) image. Differentiation between cardiac thrombus and intracardiac signal resulting from slowly flowing blood was possible based on different signal intensity changes using various techniques. In conclusion, MI imaging constitutes another noninvasive modality for the detection of cardiac thrombus. Further work is needed to determine its accuracy compared with that of two-dimensional echocardiography.

Cholangiocarcinoma: imaging by MR.

Magnetic resonance (MR) images and computed tomographic (CT) scans of nine patients with histologically proved cholangiocarcinoma were compared retrospectively to assess the potential of MR imaging in the detection and staging of the disease. Cholangiocarcinomas were demonstrated as soft-tissue masses by both techniques in seven of the nine patients. In three patients, the masses were more apparent with MR because of a greater degree of contrast between the tumor and the surrounding tissues. In all four patients with the scirrhous subtype of cholangiocarcinoma, the soft-tissue masses showed decreased signal intensity on the second spin-echo image (echo time = 56 msec). Displacement or encasement of the adjacent vessels was well demonstrated by MR. Distal extension of the tumor (hepatic metastases, regional lymphadenopathy) appeared on both MR images and CT scans but was more apparent with MR. Both MR and CT demonstrated intrahepatic bile duct dilatation, but CT demonstrated it more readily. MR appears to be an effective modality for the detection and staging of cholangiocarcinoma.

Adnexal structures: MR imaging.

Magnetic resonance (MR) images of the pelvis in 63 women (40 healthy and 23 with various adnexal diseases) were assessed retrospectively. When imaged with contiguous sections without gaps, adnexa were demonstrated bilaterally in 13 of the 15 healthy women of reproductive age, but in only seven of the 15 healthy postmenopausal women. Normal adnexa demonstrated low to medium signal intensity on images obtained with short repetition time (TR) (0.5 sec) and echo delay time (TE) (28 or 30 msec). Their signal intensity approached that of fat on images with a long TR (2.0 sec) and TE (56 or 60 msec). The adnexal origin of the pelvic masses was correctly identified in every case. Lesions containing fluid with little or no protein, fat, or blood content (simple fluid) had characteristically long T1 and T2 relaxation times and low signal intensity on images obtained with a short TR (0.5 sec) and TE (28 or 30 msec); they could be readily differentiated from all the other types of lesions.

MR imaging of the dilated biliary tract.

The magnetic resonance (MR) examinations of 18 patients with dilated bile ducts were reviewed retrospectively to determine the capability of MR to demonstrate biliary dilatation, assess MR appearance of the dilated biliary tract using spin-echo techniques, and define the optimal MR imaging parameters (repetition time [TR] and echo time [TE]) for its demonstration. On images with short TR (0.5 sec) and TE (28 msec), the dilated intrahepatic and intrapancreatic bile ducts usually had lower signal intensity compared with the surrounding liver or pancreas; on images with long TR (2.0 sec) and TE (56 msec), they had higher signal intensity. Because of the observed variation in percentage of contrast between dilated bile ducts and surrounding liver and pancreas, two imaging sequences are recommended to obtain reliable demonstration of dilated intrahepatic and intrapancreatic bile ducts. The dilated common bile duct at the level of the hepatic hilus is best seen with a short TR and TE.

Uterine leiomyomas: correlation of MR, histopathologic findings, and symptoms.

Magnetic resonance (MR) imaging, symptoms, and pathologic findings were correlated in 59 uterine leiomyomas from 23 patients. The tumors varied from less than 1 cm to 18 cm in diameter. Fifty-seven leiomyomas were identified in the corpus uterus, one was located within the broad ligament, and another was detected in the cervix. Among the corpus lesions, 9 were correctly identified on MR images as subserosal and 37 as intramural. Of 11 tumors assigned at surgery to the submucosal group, 10 had been accurately defined with MR. On MR, myomas associated with hypermenorrhea produced an anatomic disruption of the "junctional zone" (the low-intensity band seen at the myometrium-endometrium junction on T2 contrast images). Long TR (2 sec) and TE (56 msec) parameters (T2 contrast images) yielded the best contrast resolution between leiomyoma and surrounding myometrium. Correlation of MR with histologic features demonstrated 2 groups of lesions. Leiomyomas free of degenerative changes emitted homogeneous signals of low intensity. Contrast between tumor and myometrium was -16% on the T1 contrast image and increased to -44 +/- 16% on the T2 contrast image. Leiomyomas with hyaline, myxomatous, or fatty degeneration demonstrated various degrees of inhomogeneity, best seen on images obtained with long TR and TE. It is concluded that MR is an accurate modality for imaging uterine leiomyomas, since it clearly demonstrates tumor number, size, location, and the presence and extent of degeneration.

MR imaging of extracranial hematomas: comparison with CT.

Thirty MR examinations of twenty-five patients with extracranial hemorrhagic lesions were reviewed. Comparative CT studies were available in 11 patients. The acute hematomas (less than 3 days old) showed intermediate intensity on the short TR (0.5 sec.) and increased in signal intensity on the long TR (2.0 sec.). The MR appearance of acute hematoma was not specific. Clot (more than 3 days old) demonstrated an intermediate intensity on the short TR and increased markedly in signal intensity on the long TR equaling the signal intensity of fat. Serum (more than 3 days old) was imaged as a high intensity lesion on both short and long TR. It is concluded that MR can be very useful for the differential diagnosis of subacute and chronic hemorrhagic lesions from other lesions.

Radiologic imaging modalities, including magnetic resonance, for evaluating lymph nodes.

Although lymphography may be more accurate in assessing the extent of abdominal and pelvic Hodgkin's lymphoma, computed tomography (CT) has similar or greater overall accuracy than other imaging modalities in detecting malignant lymph nodes in the neck, chest, abdomen and pelvis. In this early stage of magnetic resonance (MR) imaging, its depiction of nodes is apparently mostly similar to that of CT. In addition, MR imaging shows the capacity to distinguish between enlarged lymph nodes caused by acute inflammation and those caused by malignant processes.

Magnetic resonance imaging of the pelvis: prostate and urinary bladder.

Magnetic resonance imaging has opened up a new horizon in the evaluation of the male pelvis. Its direct multiplanar imaging and display of the unique tissue contrast allows for the demonstration of prostate anatomy. Prostatic disease, even when confined to the gland, is easily depicted. However, one cannot distinguish benign from malignant processes. In a patient with a known prostatic neoplasm, magnetic resonance is useful as a staging modality. Accuracy in the staging of prostatic malignancies by MRI surpasses that of ultrasound or CT. In the evaluation of the urinary bladder, the greatest advantage of magnetic resonance is its ability to differentiate between a normal bladder, and other pathologic conditions affecting the bladder, including inflammatory, congestive and neoplastic processes. In the evaluation of bladder carcinoma, magnetic resonance is useful as a staging modality. Clinical application of magnetic resonance is just beginning and therefore, the full potential of the modality has yet to be explored.

Spin-echo MR imaging of intracranial hemorrhage.

This retrospective study was performed to describe the appearance of intracranial hemorrhagic lesions on magnetic resonance (MR) imaging at 0.35 tesla using the spin-echo technique, and define the present clinical role of MRI in this particular pathology. Forty-eight examinations of forty-three patients with forty-seven intracranial hemorrhagic lesions (39 true hematomas and 8 hemorrhagic lesions mixed with other tissues) were reviewed for this study. Comparative CT studies were available for all the patients. In our limited experience with acute hematomas (less than 3 days old), low or isointense signal was seen with a short TR (0.5 s), but a relative increase in signal intensity was observed with a long TR (2.0 s). This appearance of acute hematoma was not specific. Chronic hematomas (more than 3 days old) were imaged as foci of bright signal intensity on both short and long TR. This pattern was characteristic of chronic hematoma. With a short TR (0.5 s), two hemorrhagic lesions (5 and 7 days old) were displayed as an isointense signal surrounded by a rim of high intensity signal. This peripheral zone most likely represented liquefaction at the clot's periphery and the initial formation of methemoglobin. T1 and T2 relaxation times were found to be very long for acute hematomas (first two days). T1 values of chronic hematomas (more than 3 days old) were comparatively short and in the same range as T1 of white matter. T2 values of chronic hematomas decreased also but remained very long.

Brain radiation lesions: MR imaging.

This retrospective study was performed to assess the capability of magnetic resonance (MR) to depict and characterize diffuse and focal radiation lesions in the brain using the spin-echo technique. The MR images of 55 patients who had undergone radiation therapy were reviewed. Comparative computed tomography (CT) studies were available for all the patients. Normal white matter was chosen as reference tissue for the quantitative comparison of signal intensities. Radiation lesions (identified in eight patients) were seen as regions of high signal intensity on the sequence with a long repetition time (TR) (2.0 sec) and showed no difference in signal compared with white matter when the TR was short (0.5 sec). Nonspecific prolongation of T1 and T2 relaxation times was measured in such lesions. In one patient, subependymal tumor spread, demonstrated by contrast-enhanced CT, was missed on MR images, masked by the adjacent abnormal signal owing to radiation effects. Recurrent or residual brain tumor could not be distinguished from radiation brain necrosis either by CT or by MR imaging. It is concluded that MR can depict radiation lesions with great sensitivity but is not very helpful for discrimination between recurrent or residual brain tumor, radiation necrosis, and other brain lesions.