Biomedical subjects
Publications and source records attributed to N Sadato.
We report two patients with HIV infection whose MR imaging showed abnormal high signal intensity confined to both putamina on T2-weighted spin echo (SE) images. We assume that they may represent the early manifestations of HIV encephalitis.
Aneurysms of the posterior inferior cerebellar artery-vertebral artery complex are relatively uncommon lesions. They include aneurysms at the origin of the posterior inferior cerebellar artery (PICA-VA), aneurysms on the distal artery (PICA) and aneurysms at the junction of the vertebral and basilar arteries (VA-BA). We have had the opportunity to treat 17 patients and study the radiological records of 9 additional patients in the past 8 years. The aneurysms ranged in size from 3 to 30 mm, with mean values of 10.6, 7.3, and 9 mm for PICA-VA lesions, distal PICA lesions, and VA-BA lesions, respectively. Three of the 4 VA-BA aneurysms were located at the midline, and the mean distance of the PICA-VA aneurysms from the midline was 7.6 to 9.4 mm; 2 aneurysms crossed the midline from their parent VA. The aneurysms were located slightly more often on the left side (left:right ratio, 1:2), were found more frequently in women (2.25:1), and occurred at a mean age of 50 years. Ten aneurysms at the origin of the PICA and 4 VA-BA aneurysms were treated via a lateral suboccipital craniectomy; 3 distal PICA aneurysms were exposed by a midline craniectomy. Surgery was carried out acutely in 5 patients. Tortuousness of the VA required contralateral approaches in 2 patients, an exploratory craniectomy in 1 patient, and an approach toward the dome of 1 patient with a VA-BA aneurysm. Morbidity was primarily due to cranial nerve dysfunction. There were no perioperative deaths. These aneurysms can easily be missed on initial radiographic examination; one appeared only on the second study, one was seen to grow over 16 days, and one was discovered at the level of C1 extracranially. Our radiographic and surgical approach to the treatment of these lesions is presented.
Preoperative embolization of vascular metastatic tumors of the spine, particularly carcinomas of renal and thyroid origin, is an adjuvant technique that significantly decreases the intraoperative blood loss and resultant surgical morbidity. Surgical decompression was achieved in 24 spinal vascular metastatic lesions, 20 of which were treated with preoperative embolization and four of which were not. The embolic materials used were gelatin sponge, polyvinyl alcohol foams, and metallic coils. In patients who underwent adequate embolization, an average of 1,850 mL of estimated blood loss was reported; in those who underwent inadequate or no embolization, greater than 3,500 mL of estimated blood loss occurred. When gelatin sponge is used, surgery should be performed within 24 hours to prevent preoperative recanalization.
We have developed a simple method to quantitate brain perfusion SPECT with N-isopropyl-p-[123I]iodoamphetamine (IMP). After an intravenous bolus injection of IMP, serial dynamic images of the brain and the lung were obtained every 5 sec for 2 min, followed by a SPECT scan at 20 min. Based on the assumption of IMP as chemical microspheres, fractional uptake (FU) of IMP in the brain was calculated from the time-activity curves of the total brain and the total lungs. FU showed a strong positive correlation with inverse of the body surface area which was calculated from the height and weight of the individual subject, suggesting that FU is influenced by cardiac output. Quantification of IMP brain perfusion SPECT was attempted with FU and estimated cardiac output in each subject, providing an index of regional cerebral blood flow. Compared with PET measurement of regional cerebral blood flow, the present method tended to overestimate the flow values. This method has a great advantage that it can be applied in many institutions having large field gamma cameras. However, the accuracy of the measurement may be limited in the tall subjects and in the cases with cardiopulmonary diseases, and further investigation is required to clarify the usefulness and limitation of this approach.
The authors report a case of two aneurysms in the posterior fossa, one of which was first visualized on follow-up arteriography. The mechanism of non-vasualization and re-appearance of the aneurysm is discussed.
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The purpose of this study was to evaluate cerebral perfusion with T2*-weighted dynamic MRI in the area around the infarcted core. We examined seven patients with subacute cerebral infarction. After bolus injection a gadopentetate dimeglumine, a series of gradient-echo images were recorded in a selected slice. From these images, concentration-time curves were created on a region-of-interest (ROI) basis around infarction for calculating relative regional cerebral blood volume (rrCBV). Brain perfusion single photon emission computed tomography (SPECT) study also was performed with intravenous injection of 123I-labeled N-isopropyl-p-iodoamphetamine (123I-IMP). All patients showed prolonged signal decrease in the area around the infarcted core. ROI analysis showed significantly increased rrCBV compared to the normal side (P < .01, paired t test). The 123I-IMP SPECT study showed that these areas had decreased cerebral blood flow. Theses findings suggest compensatory vascular dilatation due to decreased perfusion pressure. T2*-weighted dynamic MRI is a useful method for detecting compensatory vasodilatation of ischemic insult in the peri-infarcted area.
Recently, perfusion imaging has been of increasing interest in MRI. We applied this method for semiquantitative evaluation of hepatic parenchymal portal blood flow in patients with diffuse liver damage. Twenty patients with diffuse hepatic damage were divided according to the Child's Classification and studied. Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) was administered into the superior mesenteric artery (SMA), and a dynamic series of T2*-weighted fast low angle shot (FLASH) images was obtained. We evaluated relative regional portal blood volume (rrPBV), mean transit time (MTT), and relative regional portal blood flow (rrPBF). The relationship between the rrPBV, rrPBF, and plasma indocyanine green retention rate test at 15 minutes (ICGR15 was also evaluated in 12 patients. Both rrPBF and rrPBV are significantly decreased in Child B & C patients compared with Child A patients. On the other hand, the MTT is significantly prolonged in Child B & C patients compared with Child A patients. Significant correlations were also noted between rrPBV and ICGR15 and between rrPBF and ICGR15. By means of selective catheterization into the SMA, we were able to estimate rrPBV, rrPBF, and MTT. This method may play a clinical role for assessment of regional portal perfusion in various diseases with diffuse liver damage.
PURPOSE: Misregistration artifact is the major cause of image degradation in digital subtraction angiography (DSA). The purpose of this study was to evaluate the efficacy of a newly developed nonlinear geometric warping method to reduce misregistration artifact in DSA. METHODS: The processing of the images was carried out on a workstation with a fully automatic computerized program. After making differential images with a lapracian filter, 49 regions of interest (ROIs) were set in the image to be processed. Each ROI of the live image scanned the corresponding ROI of the mask image searching for the best position to match itself. Each pixel of the mask image was shifted individually following the data calculated from the shifts of the ROIs. Five radiologists compared the images produced by the conventional parallel shift technique and those processed with this new method in 16 series of cerebral DSA. RESULTS: In 14 of 16 series (88%), more radiologists judged the images processed with the new method to be better in quality. Small arteries near the skull base and veins of low density were clearly visualized in the images processed by the new method. CONCLUSION: This newly proposed method could be a simple and practical way to automatically reduce misregistration artifacts in DSA.
A case of intradural spinal lipoma, rarely seen in the high cervical region, is described. Extension into the posterior fossa is not infrequent with these rare tumors. Magnetic resonance imaging clearly showed the longitudinal dimension of the tumor as well as the infiltrative extension into the spinal cord without any invasive procedure.
A case of an epidermoid cyst obstructing the transverse sinus is presented. The preoperative radiologic evaluation comprised CT, MR Imaging, and cerebral angiogram. The discussion includes the relative value of each test as part of the preoperative evaluation and the differential diagnosis of lateral sinus occlusion.
Computed tomography of the brains in 20 patients with acute rupture of posterior fossa aneurysms was reviewed and analyzed retrospectively. Findings were compared with those from 44 cases described in the literature and with the findings in ruptured supratentorial aneurysms. Extravasated blood was observed in 19 of 20 patients (95%); intraventricular hemorrhage (IVH) in 17 of 20 (85%); and subarachnoid hemorrhage (SAH) in 13 of 20 (65%). These values were significantly higher than those previously reported and suggest that, during the acute phase of rupture, extravasated blood may be detected with the same frequency in either infratentorial or supratentorial ruptured aneurysms. Subarachnoid hemorrhage was accompanied by IVH, prominent in the fourth ventricle and without intraparenchymal hematoma, in 11 patients (55%). This pattern is highly suggestive of ruptured posterior fossa aneurysms. Intraventricular hemorrhage without SAH was noted in five patients (25%) and specifically represented ruptured posterior inferior cerebellar artery aneurysms. Subarachnoid hemorrhage without IVH was noted in only two patients (10%).
OBJECTIVE: We applied glucose loading during PET studies with [18F]2-fluoro-2-deoxy-D-glucose (FDG) to enhance detection of brain tumors by diminution of FDG uptake in normal gray matter. MATERIALS AND METHODS: This study involved three patients with glioblastomas. Two PET scans were performed in all cases within 1 week in control and with glucose loading state. RESULTS: In all patients, tumor was depicted more clearly with glucose loading than in the control study. The FDG uptake ratio of tumor to normal cortical gray matter showed a mean increase of 27% with glucose loading. CONCLUSION: This technique might be useful for detection of recurrent or residual tumors.
PURPOSE: Our aim was to evaluate the visibility of the cervical spinal cord with [18F]2-fluoro-2-deoxyglucose (FDG) and a high-resolution PET scanner and to quantify the glucose utilization by the cervical cord. METHOD: Twenty-one normal subjects and three cervical myelopathy patients were studied. The visibility of the cervical spinal cord in sagittal and coronal sections was evaluated. The metabolic rate of glucose (MRGlu) and standardized uptake value (SUV) of FDG in the cord were calculated. RESULTS: The entire cervical spinal cord was clearly visualized in 57% of the subjects: the upper cord in 81%, the middle cord in 73%, and the lower cord in 57%. The MRGlu of the normal cord was 1.93 +/- 0.37 mg/100 g/min. SUV was constant across all the vertebral levels and negatively correlated with subject age. In the myelopathy patients, the SUV of the entire cervical cord was lower than in the age-matched normal subjects. CONCLUSION: These preliminary results indicate that the cervical spinal cord can be visualized as a normal structure in routine head and neck PET imaging and that FDG-PET may provide quantitative information about spinal cord disorders.
PURPOSE: The aim of our study was to compare the activation patterns of higher cognitive function detected by functional MRI (fMRI) with those by H2(15)O positron emission tomography (PET). METHOD: Activation studies with both modalities were performed in six normal volunteers with identical covert word generation tasks and statistical analysis. For PET, each subject had five rest scans and five task scans at 10 min intervals. fMRI was performed with a 1.5 T magnet using T2*-weighted echo planar sequences. Each scanning session consisted of two rest and two task periods of 30 s each, alternating rest and task. RESULTS: In group analysis, the activation patterns on both PET and fMRI were similar, whereas the deactivation patterns differed, presumably due to the noise of fMRI. In single-subject analysis, PET showed fewer activated areas and fMRI showed more areas of activation than in group analysis. CONCLUSION: fMRI has an advantage over 3D PET in its better signal-to-noise ratio for detecting change in neuronal activity for higher brain function.