[Magnetic resonance tomography (MRT) of the breast in problem patients]. / Magnetresonanztomographie (MRT) der Mamma bei Problempatientinnen.

Over the past few years MRI has become important in the evaluation of inconclusive mammograms. These studies were performed on high-field strength machines, which have the disadvantage of limited accessibility. We evaluated 185 investigations on 169 patients on a 0.5 Tesla MR machine using a dynamic sequence and gadolinium (Gd) DTPA. The results in 107 patients were correlated with the histological findings and MRI assessment proved correct in 44 of 47 benign lesions (93.6%) and 57 of 60 malignant lesions (95%). The 3 false positive results occurred in patients with mastitis, fibroadenoma and an ectatic vessel, respectively. Of the 3 false negative results 2 occurred in patients with microcarcinomas and were due to partial-volume artefacts, whilst the third was due to a technical error. These results compare with those reported in the literature using mainly high-field strength machines. Furthermore, unsuspected second tumours were diagnosed in the ipsilateral breast of 6 women and infiltration of the adjacent thoracic wall in 4 women, findings which had not been evident on mammography. Hence, our results indicate that a mild-field strength MR machine is a valuable tool not only for the non-invasive differentiation between benign and malignant lesions of the breast, but also for planning therapeutic strategy.

Quantitation of structural distortion of the cervical neural foramina in gradient-echo MR imaging.

Quantitative errors (due to magnetic susceptibility artifacts) in the measurement of the cervical spinal neural foramina with fast gradient-echo (GRE) magnetic resonance imaging were assessed. Cylindric phantoms of different materials were used to demonstrate the nature of magnetic susceptibility artifacts, emphasizing the dependence of the artifact on tissue geometry. Neural foramina diameters measured on thin, sagittal GRE and spin-echo (SE) images through the neural foramina of a fresh human cervical spine specimen were then compared with direct measurements with calipers. The GRE images showed more apparent narrowing than did the SE images. The absolute distortion of seven neural foramina was rather constant (less than two pixels) on the GRE images; therefore, the relative distortion was inversely proportional to the size of the neural foramen, ranging up to 10% in the upper cervical region at a short TE. The absolute and relative distortion increased as TE increased. At a constant TE, the structural distortion did not change with different TRs or flip angles. The shortest possible TE is recommended in evaluation of the cervical spine.

MR imaging of vertebrobasilar vascular disease.

Sixteen patients with vascular lesions of the vertebral and basilar arteries were studied with magnetic resonance imaging. The vascular abnormalities included seven cases of atherosclerotic disease with partial or complete thrombosis, six aneurysms, two cases of vertebrobasilar dolichoectasia, and one basilar artery dissection. Magnetic resonance effectively demonstrated vascular thrombosis with occlusion as high signal intensity on spin echo (SE) sequences with absence of flow void and no flow enhancement on gradient echo (GRE) images. Nonthrombosed aneurysms exhibited mixed signal intensity on SE images and hyperintensity on GRE images. Intraluminal thrombus also appeared heterogeneous, with variable signal intensity depending on the specific components of hemorrhage present. Correlation of the SE and GRE scans was helpful for distinguishing stasis and turbulent flow from thrombus. Compression of cranial nerves by vascular structures was clearly depicted in both cases of dolichoectasia. Basilar artery dissection was displayed as a focal area of flow void surrounded by a thrombosed false lumen. Magnetic resonance is an effective noninvasive method for evaluating vascular pathology of the vertebrobasilar system.

[Color-coded Doppler sonography of the carotid artery]. / Farbkodierte Doppler-Sonographie der Arteria carotis.

A total of 844 patients were evaluated to compare the value of ultrasonography and color-flow Doppler and to demonstrate the advantage presented by the latter method. In 89%, color-flow assessment was in complete agreement with the duplex assessment. In the remaining 11%, important additional results were discovered in the color-flow examination. Non-stenotic plaques were seen more often (43%) in the wide carotid bulb; stenotic plaques and occlusion were found more often (66% and 82%) in the internal carotid artery. Color-flow Doppler allows the sonomorphological (plaques, stenoses, occlusion) and functional parameters (turbulences, flow enhancement) to be studied at the same time.

[Color-coded Doppler sonography in the diagnosis of carotid artery diseases]. / Farbkodierte Dopplersonographie in der Karotisdiagnostik.

Color-flow Doppler is a new development of duplex sonography of the peripheral vessels. In this study 844 consecutive patients were evaluated (a) to assess the comparative value of these two methods, (b) to see if there is a correlation between the degree of stenosis and the incidence of neurological symptoms and (c) to find a possible relationship between the plaque structure and the incidence of neurological deficits. (a) In 89%, the color-flow assessment was in complete agreement with the duplex assessment. In the remaining 11%, important additional results were discovered in the color flow examination. (b) Non-stenotic plaques were seen more often (43%) in the wide carotic bulb, stenotic plaques and occlusion were found more often (66 and 82%) in the internal carotic artery. Vessel occlusion was found most often in patients with cerebral ischemia. Color-flow Doppler demonstrated a higher incidence of hemodynamic stenosis in patients with peripheral vascular disease, hypertension and bruits. (c) Patients with heterogeneous plaques demonstrated a significantly higher risk of neurological deficits than those with homogeneous plaques. The great advantage of color-flow Doppler is that it enables sonomorphological (plaques, stenoses, occlusion) and functional parameters (turbulences, flow enhancement) to be studied during the same procedure.

MR imaging of the temporomandibular joint: a cadaver study of the value of coronal images.

Recent studies comparing cryosectional anatomy of the temporomandibular joint (TMJ) to its MR appearance have shown that the assessment of disk displacement is inaccurate when based on the sagittal plane alone. This article describes the MR appearance of the normal and abnormal (positional and osseous changes) TMJ in the coronal plane and compares these findings with their cryosectional anatomy. Twenty-two TMJs from unselected frozen cadavers were embedded in paraffin. Coronal and sagittal MR imaging was performed; specimens were then cut in the same plane as the coronal images. Disk position by cryosection was normal in 14 cases and abnormal in eight cases. Coronal MR images alone correctly depicted the TMJ disk position in 17 cases (77%) (13 normal, four abnormal). Complementary sagittal images were necessary for diagnosing anterior displacement in two cases (9%). MR was inaccurate in three cases (14%) of severe degenerative joint disease. Bone condition was correctly diagnosed on the basis of coronal images alone in all cases. Our study shows that coronal MR imaging alone of the TMJ in cadavers accurately shows disk position in 77% of cases. Complementary sagittal images were of benefit in the diagnosis of an additional 9% with anterior displacement. Disk position was assessed inaccurately in either plane in patients with severe degenerative joint disease. For a full MR assessment of the TMJ for disk position and bone condition, we recommend imaging in both coronal and sagittal planes.

Clinical experience with routine Gd-DTPA administration for MR imaging of the brain.

A retrospective analysis of intracranial magnetic resonance (MR scans of 514 patients who underwent nonselective Gd-DTPA enhanced MR imaging was performed to determine the efficacy of this protocol for Gd-DTPA administration. This report reviews the frequency and clinical significance of abnormally enhancing areas that were entirely undetectable on precontrast images or would have been missed without the retrospective knowledge of enhancement. Fifty-seven patients (11% of the 514 patients studied) showed enhancing lesions, with 16 (3.1% of the total) of these patients demonstrating one or more lesions identifiable only on postcontrast images. Of those 16 patients, 8 had other focal abnormalities on precontrast studies, whereas the remaining 8 (1.6% of the total) had negative precontrast studies. The new diagnoses affected clinical management directly in five patients and in another nine contributed potentially significant information. Considerations regarding a selective versus nonselective protocol for Gd-DTPA administration for intracranial MR imaging and the use of clinical information to augment these protocols are discussed.

Primary myxoma of the posterior fossa.

A rare case of primary intracranial myxoma of the posterior fossa is described in a 32-year old woman. The patient presented with a history of headaches, disequilibrium, nausea and abnormal vision for several months. Computed tomography (CT) showed a well-demarcated hypodense mass. After contrast administration the mass appeared as an inhomogeneously enhancing lesion surrounded by a small rim of edema. The mass was surgically excised with histological examination revealing a true myxoma. Echocardiography revealed no evidence of a cardiac myxoma. The CT appearance of other case reports of non-cardiac myxomas in the literature is reviewed.

Heterotopic brain in the middle ear: CT findings.

A soft tissue mass was found by CT in the mesotympanum of the left middle ear of a 4-year-old boy. This lesion was without radiologic or surgical evidence of associated bony defect or communication with the intracranial cavity. Pathological examination revealed heterotopic brain tissue. Although heterotopic brain tissue in the middle ear is rare, it should be considered in the differential diagnosis of soft tissue middle ear masses.

Diagnostic significance of interslice gap and imaging volume in body MR imaging.

Thin interslice gaps and large imaging volumes are detrimental to MR signal and contrast, especially when the body coil is used. To show the influence of these two factors on fat and water signal and contrast, we performed a series of in vitro experiments. A cylinder filled with water and another filled with oil were imaged transaxially (TR = 2000 msec; TE = 20 and 70 msec) with different interslice gaps (0-150% slice thickness). A series of images was obtained to cover a 40-cm imaging volume. Increasing interslice gap thickness increased water signal without affecting fat signal, resulting in a decrease in fat/water contrast on TE = 20 msec (less T1-weighting) and increasing contrast on TE = 70 msec (more T2-weighting). Contrast nearly doubled when the interslice gap was increased from 10% to 75%. As slices moved away from the central slice, fat and water signals decreased slowly to 12.5 cm off center. Signal loss was significant with offsets greater than 12.5 cm. These results emphasize that to obtain proper contrast on T2-weighted images, the optimal interslice gap should be used and the region of interest should be near the central slice. Otherwise, images should be interpreted with caution.

Primary intracranial CNS lymphoma: MR manifestations.

We reviewed MR scans of 10 patients with biopsy-proved primary CNS lymphoma. Twenty-five lesions were identified in 10 patients (four with AIDS and six without AIDS). In general, the typical lesion of CNS lymphoma was found to have the following MR characteristics: they were slightly hypointense on T1-weighted images and slightly hyperintense on proton density and T2-weighted images relative to gray matter; they induced mild edema and mild to moderate mass effect. In AIDS patients, 82% of the lesions were smaller than 2 cm in diameter, and were frequently located in the temporal lobes and basal ganglia; they were often multiple. In non-AIDS patients, 75% of the lesions were larger than 2 cm in diameter and were primarily found in the deep parietal lobe; most were solitary.

Mucocele of the anterior clinoid process: CT and MR findings.

A patient with biopsy-proven primary mucocele of the anterior clinoid process is presented. Gadolinium-DTPA enhanced magnetic resonance imaging revealed a nonenhancing lesion isointense to gray matter. Computed tomography revealed well corticated bony margins without direct involvement of the sphenoid sinus.

MRI evaluation of pigmented skin tumors. Preliminary study.

Magnetic resonance imaging (MRI) was performed in 16 patients with pigmented skin lesions, seven with nodular melanomas, two with superficial spreading melanomas, two with subcutaneous melanoma metastases, and five with different benign pigmented nodular skin lesions. The results of MRI were compared with the histologic diagnoses. Signal intensities of the lesions were compared with subcutaneous fat, revealing a lower signal intensity of all lesions on T1-weighted images. Intensity measurements showed a significant (P less than .01) difference between benign and malignant lesions on T2-weighted images.

MR demonstration of reversible brain abnormalities in eclampsia.

A 24-year-old woman with eclamptic convulsions during her 25th week of gestation is presented. Magnetic resonance imaging revealed multiple hyperintense foci within the cerebral cortex, most likely related to cerebral ischemia and edema. The MR abnormalities resolved completely within 1 week.

Internal jugular and subclavian vein thrombosis caused by central venous catheters. Evaluation using Doppler blood flow imaging.

Thrombosis of the internal jugular vein and the subclavian vein is often caused by central venous catheters. Doppler blood flow imaging (duplex sonography and color flow imaging) is very useful to establish the diagnosis, as soon as signs of venous obstruction occur after placing a catheter. Twenty-six patients with clinically suspected thrombosis were examined; in 25 patients thrombosis of the internal jugular or subclavian vein was diagnosed. By means of duplex sonography and color flow imaging, the degree of venous obstruction can easily be determined. The efficiency of therapy can be controlled. With color flow imaging, blood flow direction and velocity can be visualized in color which provides global information about hemodynamics in a short time. Furthermore, color flow imaging is a suitable method to detect even small subcutaneous collaterals.