Faculty Bibliography

BACKGROUND AND PURPOSE: In evaluating intracranial tumors, a safe low-cost alternative that provides information similar to that of digital subtraction angiography (DSA) may be of interest. Our purpose was to determine the utility and limitations of a combined MR protocol in assessing (neo-) vascularity in intracranial tumors and their relation to adjacent vessels and to compare the results with those of DSA. METHODS: Twenty-two consecutive patients with an intracranial tumor who underwent preoperative stereoscopic DSA were examined with contrast-enhanced dynamic T2*-weighted perfusion MR imaging followed by a T1-weighted three-dimensional (3D) MR study (volumetric interpolated brain examination [VIBE]). The maximum relative cerebral blood volume (rCBV) of the tumor was compared with tumor vascularity at DSA. Critical vessel structures were defined in each patient, and VIBE images of these structures were compared with DSA findings. For full exploitation of the 3D data sets, maximum-intensity projection algorithms reconstructed in real time with any desired volume and orientation were used. RESULTS: Tumor blush scores at DSA were significantly correlated with the rCBV measurements (r = 0.75; P <.01, Spearman rank correlation coefficient). In 17 (77%) patients, VIBE provided all relevant information about the venous system, whereas information about critical arteries were partial in 50% of the cases and not relevant in the other 50%. CONCLUSION: A fast imaging protocol consisting of perfusion MR imaging and a volumetric MR acquisition provides some of the information about tumor (neo-) vascularity and adjacent vascular anatomy that can be obtained with conventional angiography. However, the MR protocol provides insufficient visualization of distal cerebral arteries

BACKGROUND: For radiobiological experiments using the Gamma Knife model B, we constructed a stereotactic device to irradiate rat and mouse brains and verify the absorbed dose at the target using thermoluminescence dosimetry and a head phantom. METHODS: Our stereotactic device is primarily designed for rats using the fixation principles of a stereotactic atlas. A head-fixation adapter for a mouse was constructed to enable targeted irradiation of mouse brains. We built simple phantoms to simulate rat and mouse heads. We placed thermoluminescent dosimeters at various positions on the phantom for dose measurements. Dose planning employed the Leksell Gamma Plan version 4.11 software, assuming a spherical skull geometry for all calculations. FINDINGS: The measurements demonstrated that the actual absorbed dose agreed with our calculations within the errors of thermoluminescence dosimetry and the accuracy of our irradiation technique and dose calculations. INTERPRETATION: This device provides an accurate method for irradiating rat and mouse brains using the Gamma Knife model B

PURPOSE: To evaluate the role of T2*-weighted echo-planar perfusion imaging by using a first-pass gadopentetate dimeglumine technique to determine the association of magnetic resonance (MR) imaging-derived cerebral blood volume (CBV) maps with histopathologic grading of astrocytomas and to improve the accuracy of targeting of stereotactic biopsy. MATERIALS AND METHODS: MR imaging was performed in 29 patients by using a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence followed by conventional imaging. The perfusion data were processed to obtain a color map of relative regional CBV. This information formed the basis for targeting the stereotactic biopsy. Relative CBV values were computed with a nondiffusible tracer model. The relative CBV of lesions was expressed as a percentage of the relative CBV of normal white matter. The maximum relative CBV of each lesion was correlated with the histopathologic grading of astrocytomas obtained from samples from stereotactic biopsy or volumetric resection. RESULTS: The maximum relative CBV in high-grade astrocytomas (n = 26) varied from 1.73 to 13.7, with a mean of 5.07 +/- 2.79 (+/- SD), and in the low-grade cohort (n = 3) varied from 0.92 to 2.19, with a mean of 1.44 +/- 0.68. This difference in relative CBV was statistically significant (P < .001; Student t test). CONCLUSION: Echo-planar perfusion imaging is useful in the preoperative assessment of tumor grade and in providing diagnostic information not available with conventional MR imaging. The areas of perfusion abnormality are invaluable in the precise targeting of the stereotactic biopsy

OBJECTIVE AND IMPORTANCE: Mycosis fungoides is a rare T-cell lymphoma of the skin that can, in one-half to three-quarters of patients suffering from this disease, involve the viscera in late stages of the disease. Although autopsy series performed more than 2 decades ago showed that the incidence of metastatic mycosis fungoides to the central nervous system is approximately one of seven, a total of only several dozen cases have been reported to date. As compared to meningeal involvement, intraparenchymal metastases are even rarer. We describe a biopsy-proven case of intraparenchymal central nervous system mycosis fungoides in a patient with nonprogressive skin involvement and no detectable visceral involvement, and we present a review of the relevant literature. CLINICAL PRESENTATION: A 68-year-old man, 3 years after the diagnosis of his skin disease, developed fatigue, confusion, and frontal lobe signs without the presence of cerebriform cells in the peripheral blood or any other clinical evidence of visceral involvement. Magnetic resonance imaging revealed a diffuse area of increased T2-weighted signal involving the white matter of both cerebral hemispheres as well as a focal area of T2 abnormality along the body of the corpus callosum. The radiological differential diagnosis was either leukodystrophy caused by chemotherapy, progressive multifocal leukoencephalopathy, or glioma with associated white matter changes. INTERVENTION: A stereotactic serial brain biopsy revealed diffuse perivascular infiltrates of atypical lymphocytes, as well as several large cells with cerebriform nuclei consistent with mycosis fungoides. The cells were immunoreactive for LCA, MT1, UCHL1, and CD3. CONCLUSION: We stress the importance of including mycosis fungoides as part of the differential diagnosis for a brain lesion in patients with cutaneous T-cell lymphoma, because treatments do exist, and we conclude that a serial stereotactic biopsy may be necessary to provide a definitive diagnosis