Ichiro Sayama

Oxygen Extraction Fraction at Maximally Vasodilated Tissue in the Ischemic Brain Estimated from the Regional CO2 Responsiveness Measured by Positron Emission Tomography

The oxygen extraction fraction (OEF) at maximally vasodilated tissue in patients with chronic cerebrovascular disease was evaluated using positron emission tomography. The vascular responsiveness to changes in PaCO2 was measured by the H215O autoradiographic method. It was correlated with the resting-state OEF, as estimated using the 15O steady-state method. The subjects comprised 15 patients with unilateral or bilateral occlusion and stenosis of the internal carotid artery or middle cerebral artery or moyamoya disease. In hypercapnia, the scattergram between the OEF and the vascular responsiveness to changes in PaCO2 revealed a significant negative correlation in 11 of 19 studies on these patients, and the OEF at the zero cross point of the regression line with a vascular responsiveness of 0 was 0.53 ± 0.08 (n = 11). This OEF in the resting state corresponds to exhaustion of the capacity for vasodilation. The vasodilatory capacity is discussed in relation to the lower limit of autoregulation.

Comparison of the clinical results of STA-MCA anastomosis and the medical treatment in the cerebral low perfusion patients with viable brain tissue

The long-term clinical results of STA-MCA anastomosis as well as the medical treatments were compared in cases that were confined as having a focal cerebral perfusion deficit with viable brain tissue, based on either the drug induced EEG and evoked potential test (DEE test) and/or by positron emission tomography (PET). The criteria for viable cerebral tissue was determined by the following four conditions: (1) functional reversibility could be confirmed by the DEE test; (2) a haemodynamic process could be found in the DEE test; (3) a haemodynamic compromise could be confirmed in the PET study; (4) misery perfusion could be confirmed in the PET study. From 1975 to 1989, 55 cases were confirmed as having viable brain tissue according to the DEE test and the PET study. Of the 55 cases, bypass surgery was performed on 35. Conservative treatment was given to the other 20 cases. There were 3 cases of perioperative neurological deterioration. One was permanent and the other 2 were transient. Results of the long-term follow up are as follows, Ipsilateral attack: 1 case (2.0%) received surgery, and 7 cases (35%) received conservative treatment. Re-attack in the contralateral or posterior circulation: 6 cases (17.2%) received surgery, and 1 case (5%) received conservative treatment. Seventy-seven per cent of the surgical cases improved or had no change in the final functional status, while only 55% of the conservative group either improved or showed no change. The incidence of ipsilateral cerebral ischaemia was significantly low in the surgical group. Contralateral and/or posterior circulation ischaemia tended to be high in this group, however.(ABSTRACT TRUNCATED AT 250 WORDS)

Problems of Surgical Treatment for Multiple Intracranial Aneurysms

A series of 105 patients presenting with multiple aneurysms and subarachnoid hemorrhage (SAH) were operated on for ruptured and unruptured aneurysms between 1976 and 1984. Clinical factors other than the severity of SAH affecting the outcomes included: 1) Misdiagnosis of the location of a ruptured aneurysm among multiple aneurysms resulted in poor outcomes because of multiple surgical approaches or rebleeding during the acute period. 2) Combinations of aneurysmal locations requiring multiple surgical approaches, such as interhemispheric and transsylvian, during the acute stage caused worse outcomes than with multi-stage surgeries. If an unruptured aneurysm could not be reached during the initial exposure, multi-stage surgery was safe if the ruptured aneurysm had been clipped during the acute period. 3) Complications occurring during unruptured aneurysm surgery. The patients age, the location and size of the unruptured aneurysms were significant factors in the clinical prognosis. Surgery for unruptured aneurysm caused 1.8% morbidity in patients between 28 and 55 years, but 18.0% morbidity in patients over 56 years of age. Surgery for internal carotid artery aneurysms resulted in 14.8% overall morbidity. Surgery for middle cerebral and anterior cerebral artery aneurysms caused below 5% morbidity. Postoperative morbidity in patients with aneurysms less than 5 mm in diameter was 1.3%, and with aneurysms measuring 10 mm or more, 20%. The optimum treatment for multiple aneurysms with SAH should be based on all factors of the patients condition, including the unruptured aneurysms.

Impact of attenuation and scatter correction in SPECT for quantification of cerebral blood flow using /sup 99 m/Tc-ethyl cysteinate dimer

We investigated the effects of attenuation correction and scatter correction on rCBF values with /sup 99m/Tc-ECD SPECT imaging. Scans were performed on seven subjects, in the presence of /sup 99m/Tc-ECD. Quantitative K/sub 1/ images were computed using the reconstructed images and the input function obtained with the frequent arterial blood sampling method. The images were reconstructed by the ordered subset expectation maximization (OSEM) reconstruction in which uniform and segmented /spl mu/ maps were used for attenuation correction with and without scatter correction. The transmission-dependent convolution subtraction technique was utilized for scatter correction. Segmented and uniform /spl mu/ maps were generated from magnetic resonance (MR) images. We also produced uniform /spl mu/ maps using ECD images obtained at various threshold levels and /spl mu/ values (0.11, 0.15, and 0.172 cm/sup -1/). Scatter correction improved the image contrast dramatically. There were no significant differences between K/sub 1/ images with attenuation and scatter corrections assuming a uniform /spl mu/ map (not 0.15 but 0.172 cm/sup -1/) and those corrected with segmented /spl mu/ maps for most regions. However, in the former images, values were overestimated for deep structures (e.g., overestimation of 9.5% in the striatum and 7.3% in the central semi oval). This small but significant error was also observed in phantom studies and Monte Carlo simulations. We show that the overestimation using uniform /spl mu/ maps is due to the weight of the path length in the bone. Absolute K/sub 1/ values were sensitive to the threshold level when the edge of the brain was determined from the ECD images, but the variation of the estimated K/sub 1/ was /spl plusmn/9.0% when the optimal threshold level was selected. This study suggests that the use of uniform attenuation /spl mu/ maps provides reasonable accuracy, despite a small but significant error in deep structure regions, and that uniform /spl mu/ maps may be provided from the emission data alone in this patient population.