Hong Sik Byun

Diffusion-Weighted MR Imaging of Intracerebral Hemorrhage

Objective To document the signal characteristics of intracerebral hemorrhage (ICH) at evolving stages on diffusion-weighted images (DWI) by comparison with conventional MR images. Materials and Methods In our retrospective study, 38 patients with ICH underwent a set of imaging sequences that included DWI, T1-and T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). In 33 and 10 patients, respectively, conventional and echo-planar T2* gradient-echo images were also obtained. According to the time interval between symptom onset and initial MRI, five stages were categorized: hyperacute (n=6); acute (n=7); early subacute (n=7); late subacute (n=10); and chronic (n=8). We investigated the signal intensity and apparent diffusion coefficient (ADC) of ICH and compared the signal intensities of hematomas at DWI and on conventional MR images. Results DWI showed that hematomas were hyperintense at the hyperacute and late subacute stages, and hypointense at the acute, early subacute and chronic stages. Invariably, focal hypointensity was observed within a hyperacute hematoma. At the hyperacute, acute and early subacute stages, hyperintense rims that corresponded with edema surrounding the hematoma were present. The mean ADC ratio was 0.73 at the hyperacute stage, 0.72 at the acute stage, 0.70 at the early subacute stage, 0.72 at the late subacute stage, and 2.56 at the chronic stage. Conclusion DWI showed that the signal intensity of an ICH may be related to both its ADC value and the magnetic susceptibility effect. In patients with acute stroke, an understanding of the characteristic features of ICH seen at DWI can be helpful in both the characterization of intracranial hemorrhagic lesions and the differentiation of hemorrhage from ischemia.

Perfusion MR Imaging: Clinical Utility for the Differential Diagnosis of Various Brain Tumors

Objective To determine the utility of perfusion MR imaging in the differential diagnosis of brain tumors. Materials and Methods Fifty-seven patients with pathologically proven brain tumors (21 high-grade gliomas, 8 low-grade gliomas, 8 lymphomas, 6 hemangioblastomas, 7 metastases, and 7 various other tumors) were included in this study. Relative cerebral blood volume (rCBV) and time-to-peak (TTP) ratios were quantitatively analyzed and the rCBV grade of each tumor was also visually assessed on an rCBV map. Results The highest rCBV ratios were seen in hemangioblastomas, followed by high-grade gliomas, metastases, low-grade gliomas, and lymphomas. There was no significant difference in TTP ratios between each tumor group (p>0.05). At visual assessment, rCBV was high in 17 (81%) of 21 high-grade gliomas and in 4 (50%) of 8 low-grade gliomas. Hemangioblastomas showed the highest rCBV and lymphomas the lowest. Conclusion Perfusion MR imaging may be helpful in the differentiation of thevarious solid tumors found in the brain, and in assessing the grade of the various glial tumors occurring there.

Structural Brain Abnormalities in Juvenile Myoclonic Epilepsy Patients: Volumetry and Voxel-Based Morphometry

Objective We aimed to find structural brain abnormalities in juvenile myoclonic epilepsy (JME) patients. Materials and Methods The volumes of the cerebrum, hippocampus and frontal lobe and the area of the corpus callosums subdivisions were all semiautomatically measured, and then optimized voxel-based morphometry (VBM) was performed in 19 JME patients and 19 age/gender matched normal controls. Results The rostrum and rostral body of the corpus callosum and the left hippocampus were significantly smaller than those of the normal controls, whereas the volume of the JMEs left frontal lobe was significantly larger than that of the controls. The area of the rostral body had a significant positive correlation with the age of seizure onset (r = 0.56, p = 0.012), and the volume of the right frontal lobe had a significant negative correlation with the duration of disease (r = -0.51, p = 0.025). On the VBM, the gray matter concentration of the prefrontal lobe (bilateral gyri rectus, anterior orbital gyri, left anterior middle frontal gyrus and right anterior superior frontal gyrus) was decreased in the JME group (corrected p < 0.05). Conclusion The JME patients showed complex structural abnormalities in the corpus callosum, frontal lobe and hippocampus, and also a decreased gray matter concentration of the prefrontal region, which all suggests there is an abnormal neural network in the JME brain.

Traumatic spinal subdural hematoma : Rapid resolution after repeated lumbar spinal puncture and drainage

A 15-year-old boy developed back pain and sciatica after a minor trauma. Magnetic resonance imaging revealed lumbar spinal subdural hematoma. After repeated lumbar spinal puncture and drainage of hemorrhagic fluid, spinal subdural hematoma was resolved completely. The benefits of conservative treatment by lumbar spinal puncture are discussed.

Embolization of intracranial aneurysms with hydrogel-coated coils : Result of a korean multicenter trial. Commentary

OBJECTIVE HydroCoil (MicroVention, Aliso Viejo, CA), a hydrogel-platinum coil hybrid device, is one of various efforts to overcome delayed recanalization of coiled intracranial aneurysms. The purpose of this study was to investigate the outcome of intracranial aneurysms treated with HydroCoils. METHODS This multicenter prospective study included 80 aneurysms in 76 patients treated with HydroCoils. There were 32 (40%) ruptured and 48 (60%) unruptured aneurysms; 22 (28%) were large aneurysms (maximal diameter, ≥10 mm) and 58 (72%) were small. Aneurysm volumes were 100 mm3 or more in 48 (60%) and less than 100 mm3 in 32 (40%); in 13 aneurysms (16%), volumes were 600 mm3 or more. Efficacy and safety were evaluated on the basis of degree of initial occlusion, procedure-related complications, and the follow-up result. RESULTS Initial aneurysmal occlusion was complete in 60 (75%) aneurysms and near-complete in 14 (17.5%). Procedure-related complications included aseptic meningitis-related problems, including delayed hydrocephalus in 13 patients (28% among cases of unruptured aneurysms) and thromboembolism in two patients. Radiological follow-up data obtained 6 months or more after coil embolization were available in 54 aneurysms (68%) and revealed stable occlusion in 48 (89%) aneurysms, minor recanalization in one (2%), and major recanalization in five (9%). All of the recanalized aneurysms were 600 mm3 or more in volume, and aneurysm volume was a single important variable related to delayed recanalization on multiple logistic regression analysis (P = 0.016). CONCLUSION HydroCoil embolization seems to be a feasible treatment option in intracranial aneurysms in terms of initial aneurysmal occlusion rate and durability at the time of the follow-up evaluation; however, caution is required regarding aseptic meningitis and delayed hydrocephalus. Calculated aneurysmal volume of 600 mm3 seems to be critical in determining the anatomic outcome in aneurysms embolized with HydroCoils.

Morphological and functional MRI, MRS, perfusion and diffusion changes after radiosurgery of brain metastasis

Radiosurgery is a noninvasive procedure where spatially accurate and highly conformal doses of radiation are targeted at brain lesions with an ablative intent. Recently, radiosurgery has been established as an effective technique for local treatment of brain metastasis. After radiosurgery, magnetic resonance (MR) imaging plays an important role in the assessment of the therapeutic response and of any complications. The therapeutic approach depends on the imaging findings obtained after radiosurgery, which have a role in the decision making to perform additional invasive modalities (repeat resection, biopsy) to obtain a definite diagnosis and to improve the survival of patients. Conventional MR imaging findings are mainly based on morphological alterations of tumors. However, there are variable imaging findings of radiation-induced changes including radiation necrosis in the brain. Radiologists are sometimes confused by radiation-induced injuries, including radiation necrosis, that are seen on conventional MR imaging. The pattern of abnormal enhancement on follow-up conventional MR imaging closely mimics that of a recurrent brain metastasis. So, classifying newly developed abnormal enhancing lesions in follow-up of treated brain metastasis with correct diagnosis is one of the key goals in neuro-oncologic imaging. To overcome limitations of the use of morphology-based conventional MR imaging, several physiological-based functional MR imaging methods have been used, namely diffusion-weighted imaging, perfusion MR imaging, and proton MR spectroscopy, for the detection of hemodynamic, metabolic, and cellular alterations. These imaging modalities provide additional information to allow clinicians to make proper decisions regarding patient treatment.

Analysis of perfusion weighted image of CNS lymphoma

PURPOSE It is difficult to differentiate CNS lymphoma from other tumors such as malignant gliomas, metastases, or meningiomas with conventional MR imaging, because the imaging findings are overlapped between these tumors. The purpose of this study is to investigate the perfusion weighted MR imaging findings of CNS lymphomas and to compare the relative cerebral blood volume ratios between CNS lymphomas and other tumors such as high grade gliomas, metastases, or meningiomas. MATERIALS AND METHODS We retrospectively reviewed MRI findings and clinical records in 13 patients with pathologically proven CNS lymphoma between January 2006 and November 2008. We evaluated the relative cerebral blood volume ratios of tumor, which were obtained by dividing the values obtained from the normal white matter on MRI. RESULTS Total 13 patients (M:F=8:5; age range 46-67 years, mean age 52.3 years) were included. The CNS lymphomas showed relatively low values of maximum relative CBV ratio in most patients regardless of primary or secondary CNS lymphoma. CONCLUSION Perfusion weighted image may be helpful in the diagnosis of CNS lymphoma in spite of primary or secondary or B cell or T cell.

Cerebral Ischemia Detected with Diffusion-Weighted MR Imaging after Protected Carotid Artery Stenting: Comparison of Distal Balloon and Filter Device

Objective The aim of this study was to examine the incidence of ischemia during protected carotid artery stenting (CAS) as well as to compare the protective efficacy of the balloon and filter devices on diffusion-weighted MR imaging (DWI). Materials and Methods Seventy-one consecutive protected CAS procedures in 70 patients with a severe (> 70%) or symptomatic moderate (> 50%) carotid artery stenosis were examined. A balloon device (PercuSurge GuardWire) and a filter device (FilterWire EX/EZ, Emboshield) was used in 33 cases (CAS-B group) and 38 cases (CAS-F group) to prevent distal embolization, respectively. All the patients underwent DWI within seven days before and after the procedures. The number of new cerebral ischemic lesions on the post-procedural DWI were counted and divided into ipsilateral and contralateral lesions according to the relationship with the stenting side. Results New cerebral ischemic lesions were detected in 13 (39.4%) out of the 33 CAS-Bs and in 15 (39.5%) out of the 38 CAS-Fs. The mean number of total, ipsilateral and contralateral new cerebral ischemic lesion was 2.39, 1.67 and 0.73 in the CAS-B group and 2.11, 1.32 and 0.79 in the CAS-F group, respectively. No statistical differences were found between the two groups (p = 0.96, 0.74 and 0.65, respectively). The embolic complications encountered included two retinal infarctions and one hemiparesis in the CAS-B group (9.09%), and one retinal infarction, one hemiparesis and one ataxia in the CAS-F group (7.89%). There was a similar incidence of embolic complications in the two groups (p = 1.00). Conclusion The type of distal protection device used such as a balloon and filter does not affect the incidence of cerebral embolization after protected CAS.

Intracranial solitary fibrous tumors: imaging findings in 6 consecutive patients.

BACKGROUND AND PURPOSE: Intracranial solitary fibrous tumors (ISFTs) are rare mesenchymal neoplasms originating in the meninges. The aim of this study was to describe the CT, MR imaging, and angiographic features of the solitary fibrous tumor and to identify imaging characteristics. MATERIALS AND METHODS: We retrospectively reviewed CT, MR, and angiographic findings in 6 cases of ISFT. We evaluated the size, shape, and location of the tumor; the internal content and margin of the lesion; the pattern of enhancement; and the change of the adjacent structures. Density on noncontrast CT scans, signal intensity on MR images, and angiographic features were also documented. RESULTS: Each lesion appeared as a discrete extra-axial mass (size, 3–7 cm; mean, 5 cm). Five lesions were entirely solid, and 1 had peritumoral cyst. All 5 of the noncontrast CT scans showed hyperattenuated masses, and the tumors exhibited marked heterogeneous enhancement. No lesion contained calcification, and 2 cases showed bone invasions. On the MR images, 4 lesions showed mixed signal intensity on T2-weighted imaging. All of the lesions revealed marked heterogeneous enhancement. All of the tumors had thickening of the meninges adjacent to the tumor. Angiography showed delayed tumor blushing in all, and 3 of them had dysplastic dilation of the tumor vessels. CONCLUSION: Although there are no pathognomonic imaging findings, some imaging features, such as the “black-and-white mixed” pattern on T2-weighted images and marked heterogeneous enhancement, might be helpful in the diagnosis of intracranial solitary fibrous tumor.

Rhabdoid meningioma: clinical features and MR imaging findings in 15 patients.

BACKGROUND AND PURPOSE: Rhabdoid meningioma (RM) is a recently described variant of malignant meningioma, with radiologic features currently not well characterized in the medical literature. The purpose of this study was to describe and characterize clinical features and imaging findings associated with RM. MATERIALS AND METHODS: CT (n = 8) and MR (n = 15) images of 15 patients (4 men and 11 women; mean age, 52 years; range, 22–75 years) with 16 pathologically proved RMs along with associated clinical records were retrospectively reviewed. All of the patients underwent surgical resection and had additional radiation therapy except for 1 patient. After surgery, the patients had follow-up brain MR imaging to evaluate for tumor recurrence. RESULTS: Nine lesions (56%) were located in the cerebral convexity, and 4 lesions (25%) were located in the parasagittal areas. The tumors were isointense (n = 15) to gray matter on T1-weighted images, whereas they were hyperintense (n = 14) on T2-weighted images. On gadolinium-enhanced T1-weighted images, homogeneous enhancement was seen in 10 lesions, and heterogeneous enhancement was seen in 6 lesions that had cysts. Cystic components were noted in 6 lesions (38%). Severe peritumoral edema was seen in 12 lesions (75%). Nine lesions (56%) had hyperostosis, and 5 of them also had bone destruction. Among the 8 cases with initial CT scans, only 1 had amorphous calcifications (13%). There was only 1 recurrence of RM found during the follow-up period after surgical resection. CONCLUSION: RMs tend to have prominent peritumoral edema, cystic components, and bone involvement.