Takashi Tahara

High [18F]-fluorodeoxyglucose uptake in abdominal abscesses: a PET study.

We report two cases of abdominal abscess displaying high uptake of [18F]fluorodeoxyglycose (FDG) by positron emission tomography (PET). Abdominal abscesses should be considered in the differential diagnosis of abdominal masses showing high FDG uptake in PET studies.

Cerebral hemodynamic change in the child and the adult with moyamoya disease.

To clarify the differences in cerebral hemodynamics and metabolism between children and adults with bilateral moyamoya disease, we measured regional cerebral blood flow, regional oxygen extraction fraction, regional metabolic rate for oxygen, regional cerebral blood volume, and regional transit time using positron emission tomography in nine patients (five children and four adults) and compared the values with those in controls (four children with unilateral moyamoya disease and six normal adults). The major differences between pediatric and adult patients were in regional cerebral blood volume and regional oxygen extraction fraction. Regional cerebral blood volume was more markedly increased relative to the control value in the children than in the adults. Also, regional oxygen extraction fraction was greater than control in areas with low blood flow in the children but was never increased in the adults. However, in the adults, only regional transit time was significantly prolonged relative to the control values. The increased regional oxygen extraction fraction relative to the control value observed in children with moyamoya disease may explain why transient ischemic attacks are a common symptom in this group.

Cerebral blood flow, oxygen and glucose metabolism with PET in progressive supranuclear palsy.

Cerebral blood flow, cerebral oxygen metabolic rate and cerebral glucose metabolic rate were measured with positron emission tomography (PET) in four patients with progressive supranuclear palsy (PSP). Decreased blood flow and hypometabolism of oxygen and glucose were found in both subcortical and cortical regions, particularly in the striatum including the head of the caudate nucleus and the frontal cortex. The coupling between blood flow and metabolism was preserved even in the regions which showed decreased blood flow and hypometabolism. These findings indicated the hypofunction, as revealed by decreased blood flow and hypometabolism on PET, both in the striatum and the frontal cortex, and which may underlie the pathophysiological mechanism of motor and mental disturbance in PSP.

Differential diagnosis of bilateral parietal abnormalities in I-123 IMP SPECT imaging

This report discusses the clinical significance of bilateral parietal abnormalities on I-123 IMP SPECT imaging in 158 patients with cerebral disorders. This pattern was seen in 15 out of 21 patients with Alzheimers disease; it was also seen in 4 out of 5 patients with Parkinsons disease with dementia, in 3 out of 17 patients with vascular dementia, in 1 out of 36 patients with cerebral infarction without dementia, in 1 out of 2 patients with hypoglycemia, and in 1 out of 2 patients with CO intoxication. Detection of bilateral parietal abnormalities is a useful finding in the diagnosis of Alzheimers disease, but one should keep in mind that other cerebral disorders may also show a similar pattern with I-123 IMP SPECT imaging.

Morphological changes of the villous microvascular architecture and intestinal growth in rats with streptozotocin-induced diabetes

Using intact tissues and vascular corrosion casts, morphological changes in the small intestine of streptozotocin-induced diabetic rats present 1 month after onset were investigated using scanning and transmission electron microscopy. Although there were increases in the height of the villi in the jejunum and not in the ileum, characteristic changes in surface morphology in the diabetic rats were observed only in the ileum. Use of a vascular corrosion cast technique clearly demonstrated the prominent thick marginal vessels of the intestinal villi of the control rats. In the diabetic rats, the central arterioles in the villi were dilated both in the jejunum and the ileum. Marginal vessels were small in the ileum but prominent in the jejunum. Using transmission electron microscopy, decreases in diameter and the number of endothelial fenestra were also evident in the marginal vessels of the ileal villi in the diabetic rats. Thus in rats made diabetic, fine structural alterations of the marginal vessels are induced in the villi of the distal ileum, in addition to quantitative changes in the jejunal villi, presumably related to hyperphagia. The marginal vessels seem to be involved in the regulation of microcirculation of the intestinal villi in the rat.

Comparison of I-123 IMP and Tc-99m HMPAO SPECT studies with PET in dementia

We compared I-123 IMP and 99m-Tc HMPAO SPECT studies with 0–15 H2O and F-18 FDG PET studies, and evaluated the clinical significance of SPECT studies in dementia. Seventeen patients including 9 patients with Alzheimer’s disease, 3 patients with Pick’s disease and 5 patients with multi-infarct dementia were studied. IMP and HMPAO SPECT studies could not detect mildly affected areas when compared with FDG PET. However, they revealed decreased perfusion in the bilateral parietal regions in Alzheimer’s disease and in the bilateral frontal regions in Pick’s disease, while MRI and/or CT showed mild to moderate cerebral atrophy. IMP and HMPAO SPECT studies can be easily performed in clinical practice, and these findings were useful in the differential diagnosis of dementia. Our preliminary results suggested that SPECT studies with I-123 IMP and Tc-99m HMPAO, despite their limitations, are useful in the differential diagnosis of dementia.

Evaluation of the significance of “redistribution” in I-123 IMP SPECT in cerebrovascular disorders—a comparative study with PET

We evaluated the significance of redistribution in123I-IMP SPECT study using PET. Twelve lesions in ten patients were selected. These lesions were classified into the following three groups; ischemia, infarction of subacute phase and infarction of chronic phase. All lesions with ischemia or subacute infarction showed good or moderate redistribution. Three of four lesions with chronic infarction showed no redistribution. The mean values of rCBF and rCMRO2 were highest in the lesions with good redistribution, but there was no differences in rOEF with the degree of redistribution. In conclusion, the tissue with good redistribution is not always viable and it was impossible to predict a region with increased rOEF by redistribution alone.