Susceptibility-Weighted Imaging as a Distinctive Imaging Technique for Providing Complementary Information for Precise Diagnosis of Neurologic Disorder

Various sequences have been developed for MRI to aid in the radiologic diagnosis. Among the various MR sequences, susceptibility-weighted imaging (SWI) is a high-spatial-resolution, threedimensional gradient-echo MR sequence, which is very sensitive in detecting deoxyhemoglobin, ferritin, hemosiderin, and bone minerals through local magnetic field distortion. In this regard, SWI has been used for the diagnosis and treatment of various neurologic disorders, and the improved image quality has enabled to acquire more useful information for radiologists.Here, we explain the principle of various signals on SWI arising in neurological disorders and provide a retrospective review of many cases of clinically or pathologically proven disease or components with distinctive imaging features of various neurological diseases. Additionally, we outline a short and condensed overview of principles of SWI in relation to neurological disorders and describe various cases with characteristic imaging features on SWI. There are many different types diseases involving the brain parenchyma, and they have distinct SWI features.SWI is an effective imaging tool that provides complementary information for the diagnosis of various diseases.

CT and MR Imaging Features in Patients with Intracranial Dolichoectasia

PURPOSE: To describe the CT and MR imaging features in patients with intracranial dolichoectasia. MATERIALS AND METHODS: The CT(n=21), MR(n=20) and MRA(n=11) imaging features seen in 28 patients (M:F=12:16 aged beetween 65 and 82 (mean, 65) years with intracranial dolichoectasia were retrospectively reviewed with regard to involved sites, arterial changes(maximum diameter, wall calcification, high signal intensity in the involved artery, as seen on T1-weighted MR images), infarction, hemorrhagic lesion, compression of brain parenchyma or cranial nerves, hydrocephalus and brain atrophy. Involved sites were classified as either type 1 (involvement of only the posterior circulation), type 2 (only the anterior circulation), or type 3 (both). RESULTS: In order of frequency, involved sites were type 1(43%), type 3(36%) and type 2(22%). Dolichoectasia was more frequently seen in the posterior circulation(79%) than in the anterior (57%). Arterial changes as seen on T1-weighted MR images, included dolichoectasia(mean maximum diameter 7.4mm in the distal internal carotid artery, and 6.7mm in the basilar artery), wall calcification(100% in involved arteries) and high signal intensity in involved. Cerebral infarction in the territory of the involved artery was found in all patients, and a moderate degree of infarct was 87%. Hemorrhagic lesions were found in 19 patients(68%); these were either l o b a r ( 53%), petechial(37%), or subarachnoid (16%), and three patients showed intracranial aneurysms, including one case of dissecting aneurysm. In 19 patients(68 %), lesions were compressed lesions by the dolichoectatic arteries, and were found -in order of descending frequency- in the medulla, pons, thalamus, and cerebellopontine angle cistern. Obstructive hydrocephalus was found in two patients (7 %), and 23 (82 % ) showed a moderate degree of brain atrophy. CONCLUSION: In patients with intracranial dolichoectasia, moderate degrees of cerebral infarction and brain atrophy in the territory of involved arteries, as well as hemorrhagic lesions and compression of the brain stem or cranial nerves, were not infrequently seen on CT and MR images. These changes were in addition to the basic arterial change(dolichoectasia, arterial wall calcification and intraluminal high signal intensity) seen on T1-weighted MR images.

MR Findings of Neuro-Behcet's Disease: Initial and Follow-up Changes

PURPOSE: To evaluate the MR findings of neuro-Behcet's disease, and changes occurring during follow up. MATERIALS AND METHODS: Brain MR imaging was performed in 19 patients in whom neuro-Behcet's disease had been clinically diagnosed. After treatment with corticosteroids and immunosuppressive agents, 23 follow-up MR images were obtained in 12 patients, and a total of 42 MR images were retrospectively reviewed by two radiologists. RESULTS: Of the 19 patients, 17 (89%) had parenchymal lesions, and the other two had dural venous sinus thrombosis. Among the 17 patients with parenchymal lesions, three showed leptomeningeal enhancement. A total of 72 parenchymal lesions were detected on initial MR images; 55 (76%) were patchy or nodular in shape and the lesion of the internal capsule appeared linear. Seventeen lesions (24%) in 12 patients were confluent. In order of frequency, the involved sites were the pons, midbrain, thalamus, basal ganglia, internal capsule, and frontal lobe. Thirteen lesions of 39 lesions detected on postcontrast images were enhanced, and a mass effect was seen in the area of 16 parenchymal lesions. Associated findings were microhemorrhage of the brain in two patients and spinal cord involvement in one. On short-term follow-up images obtained 1 week to 2 months after intensive treatment during the acute stage of the illness, the leptomeningeal enhancement seen in three patients had decreased and most parenchymal lesions showed improvement. Long-term follow-up images obtained 3 months to 3 years later showed that parenchymal lesions had relapsed in five patients, and brainstem atrophy had developed or progressed in five others. CONCLUSION: The most characteristic MR finding of neuro-Behcet 's disease is multiple non-hemorrhagic lesions involving the brainstem. Leptomeningeal enhancement and dural venous sinus thrombosis may also be noted. On follow-up MR, the lesions may show either improvement or aggravation, and brainstem atrophy is not uncommon.

Experimental Study on High-Resolution CT of Pulmonary Oil Embolism Induced by LipiodoI-Adriamycin Emulsion

PURPOSE: To elucidate high-resolution CT(HRCT) findings and their pathologic basis in pulmonary oil embolism induced by LipiodoI-Adriamycin emulsion. MATERIALS AND METHODS: Pulmonary oil embolism was induced by infusing LipiodoI-Adriamycin emulsion through a peripheral vein in twelve Yorkshire pigs. Serial HRCT scans were performed on 2rid, 4th, 7th, 14th, and 28th day after the procedure. The pigs were sacrificed immediately after HRCT and histologic specimens were prepared in the same plane and level with HRCT. RESULTS: The basic pathology was reversible hemorrhagic edema of the lung. On HRCT, intraalveolar hemorrhage and edema in the acute stage manifested as ground-glass opacity or air-space consolidation of the whole secondary Iobule. The lesions were predominantly distributed over the dependent posterior lung fields because the specific gravity of Lipiodol is 1.28. Interlobular septal thickening due to edematous fluid collection was also associated. With the elapse of time, the extent and severity of the acute lesions resolved and, sometimes, changed into small nodular opacities. Pulmonary opacity was most severe on the post-embolization 2nd day and completely resolved within 2 weeks. CONCLUSION: Pulmonary embolization of LipiodoI-Adriamycin emulsion causes reversible hemorrhagic edema of the lung and Lipiodol toxicity seems to play a major role. HRCT findings of pulmonary oil embolism are quite different from those of pneumonia and pulmonary metastasis, which suggests the possibility of clincal application.