After closed head injury nineteen patients had single photon emission tomography (SPECT) using the lipophilic tracer 99m-Technetium hexamethyl-propyleneamineoxime (HMPAO) to compare the defects shown by CT and MRI. SPECT showed more focal cerebral lesions than either CT or MRI alone or in combination. Most lesions shown by SPECT were not shown by CT or MRI in the corresponding anatomical regions. The most severely disabled patients showed the highest number of SPECT lesions (average four per patient) and the lowest (mean, SE) cerebral blood flow (718, 69 ml/min) compared with the less disabled patients (two per patient and 1058, 51 ml/min, p < 005).There was a correlation between the Glasgow Outcome Scale grade and the global cerebral blood flow (r 0 74, p < 0-05 months. All scans were carried out within 12 weeks of each other, with one exception, and in random order. Clinical assessment at the time of the first scan was made using the Glasgow Outome Scale, Extended version'0 (GOSE); 1 = death, 2 = persistant vegetative state, 3a = severe disability-needs continuous supervision or help with many activities of daily living, 3b = severe disability-can manage on own with considerable support, 4a = moderate disability-significant problems with either occupational or social functioning, 5a = good recovery with residual symptoms, 5b = good recovery with no symptoms. Unenhanced CT scanning was performed on a GE 9000 scanner, with 10 mm contiguous slices from the radiological baseline. MRI was performed on a 0-8 Tesla Imatec International machine using TR 1500 ms and TE 64 and 128 ms sequences at 12 mm slices from the radiological baseline. One sagittal section was also made. For rCBF the patient was studied in a quiet room after a full explanation of the test and with a nurse and doctor in attendance. The eyes were not covered. There was a five minute delay between the insertion of the venous line and the start of the study. SPECT was performed 20 minutes after 600 MBq. TC-99m HMPAO was injected intravenously using a GE 400/AT gamma camera with a high resolution collimator linked to a PDP 1/73 computer. Raw data was collected over 360 degrees rotation at each of 64 angles (counting 30 seconds per angle) with resolution of 64 by 64 pixels and a zoom factor of 1-2. A series of 10 mm transverse slices were taken parallel to a plane lying approximately 10 degrees to the OM line. Coronal and sagittal sections were also obtained and a computer program was available to select and display corresponding regions in each of the three planes.CT and MRI scans were read by an experienced neuroradiologist. (MC) without 92
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