Amino acid study of cerebral gliomas using positron emission tomography--analysis of (11C-methyl)-L-methionine uptake index

Sixteen patients with gliomas (7 low grade, 9 high grade) were examined using positron emission tomography (PET) with intravenous administration of 22.2 MBq/kg (0.6 mCi/kg) of (11C-methyl)-L-methionine (C-11 Met). The tracer uptake in regions of interest was calculated on PET images taken 45 minutes after injection; the uptake index was represented as a percentage of the total count in the arterial blood summed over 45 minutes. C-11 Met uptake indices in the tumors ranged from 0.020 to 0.041% with a mean of 0.032% for the low-grade gliomas and from 0.013 to 0.044% with a mean of 0.036% for the high-grade gliomas. These indices significantly increased as compared with those in the contralateral gray matter (0.008-0.032% with a mean of 0.023%; p less than 0.01 vs. low-grade gliomas, p less than 0.001 vs. high-grade gliomas). In the low-grade gliomas, C-11 Met PET images clearly depicted the existence and even the extent of the tumors, although x-ray computed tomography (CT) did not always distinguish tumoral lesions. In the high-grade gliomas, the areas of tracer accumulation regionally extended to peritumoral low density on CT scans, where malignant tumor cell infiltration was proved by operative and follow-up CT findings. C-11 Met may be a useful radiopharmaceutical for differential diagnosis of gliomas, and the accuracy of tumor localization will give us a better rationale in therapeutic strategies for surgery and radiation therapy of gliomas.

[The changes of cerebral blood flow and metabolism of normal brain tissue after surgery, radiation, and chemotherapy in brain tumor patients: evaluated by position emission tomography]

The changes of cerebral blood flow (CBF) and metabolism of normal brain tissue after surgery, radiation, and chemotherapy in brain tumor patients were measured by positron emission tomography (PET). The subjects consisted of 6 men and 3 women, and were from 11 to 62 years old. Those were four patients with glioblastomas, one patient with malignant oligodendroglioma, one patient with astrocytoma grade II, one patient with astrocytoma grade III, one patient with pontine glioma, one patient with pineal germinoma. Seven patients were operated and pathohistologically diagnosed. Two patients with pineal germinoma and pontine glioma were not operated and radiologically diagnosed. Of 7 operated patients, first PET was performed before operation in 3 patients, and from 10 to 16 days after operation in 4 patients. Following first PET, the patients were treated with irradiation (1 case), or with both irradiation and chemotherapy (8 cases). The total radiation dose for tumor was from 59 to 61 Gy distributed in a period of 6-8 weeks. Whole brain irradiation was performed up to 30 or 40 Gy, with a remaining dosimetry (20-30 Gy focused on the tumor field. Chemotherapy consisted of intravenous administration of ACNU and oral administration of FT-207. Second PET was performed 1 month after therapy (9 cases), and third PET was performed from 4 to 24 months after therapy (6 cases). Fourth PET was performed in 2 patients (22 and 35 months after therapy), and fifth PET was performed in one patient (35 months after therapy).(ABSTRACT TRUNCATED AT 250 WORDS)

Decrease in cerebral metabolic rate of glucose after high-dose methotrexate in childhood acute lymphocytic leukemia

We measured changes in the regional cerebral metabolic rate of glucose (rCMRGlu) using 18F-fluorodeoxyglucose and positron emission tomography for the assessment of neurotoxicity in childhood acute lymphocytic leukemia treated with high-dose methotrexate (HD-MTX) therapy. We studied 8 children with acute lymphocytic leukemia (mean age: 9.6 years) treated with HD-MTX (200 mg/kg or 2,000 mg/M2) therapy. CMRGlu after HD-MTX therapy was most reduced (40%) in the patient who had central nervous system leukemia and was treated with the largest total doses of both intrathecal MTX (IT-MTX) and HD-MTX. CMRGlu in the whole brain after HD-MTX therapy was reduced by an average of 21% (P less than 0.05). The reductions of CMRGlu in 8 patients were correlated with total doses of both IT-MTX (r = 0.717; P less than 0.05) and systemic HD-MTX (r = 0.784; P less than 0.05). CMRGlu of the cerebral cortex, especially the frontal and occipital cortex, was reduced more noticeably than that of the basal ganglia and white matter. We suggest that the measurement of changes in rCMRGlu after HD-MTX therapy is useful for detecting accumulated MTX neurotoxicity.

[Regional effects of craniotomy on cerebral circulation and metabolism: PET study on the un-ruptured aneurysmal surgery]

Regional effects of craniotomy on cerebral circulation and metabolism, such as regional cerebral blood flow (rCBF), regional cerebral oxygen consumption (rCMRO2), regional oxygen extraction fraction (rOEF), and regional cerebral blood volume (rCBV) were examined by a PET (positron emission tomography) study concerning surgery that was performed on unruptured aneurysm patients. Eight patients with intracranial un-ruptured aneurysms were studied pre- and post-operatively by the 15O labelled-gas steady-state method, using HEADTOME-III. All patients underwent aneurysmal surgery performed by the transsylvian approach. There was a significant increase in the mean OEF values taken from the whole-brains of 8 patients, but there was not a significant change in CBF, CMRO2 or CBV. The increase in OEF was caused by decrease of O2 content, which was caused by post-operative decrease in the Hb value. So, this OEF increase was not the direct effect of craniotomy. In 2 patients, the rCBF and rCMRO2, in the fronto-temporal region (where craniotomy was performed) increased post-operatively. This regional effect suggests transient reactive hyperemia following compressive ischemia during the operative procedure, and metabolic demands for recovery of brain function. In 2 other patients, who had relatively low rCBFs during the pre-operative study, rCBF and rCMRO2 in the bi-frontal region had decreased more at the post-operative study. This change appears to have been caused by removal of cerebrospinal fluid and depression of the frontal lobe. From this study, it becomes evident that the regional effect of craniotomy on cerebral circulation and metabolism is not so great, when adequate microsurgical techniques are used.

Occipital lobe infarction and positron emission tomography

Even though the PET study revealed a total infarct in the territory of the left PCA in our 3 cases of pure alexia, it is still obscure which part of the left occipital lobe is most closely associated with the occurrence of the pure alexia. In order to elucidate the intralobar localization of the pure alexia, it is needed to have an ideal case who shows an pure alexia due to the localized lesion within the left occipital lobe. Furthermore, high-resolution PET scanner will circumvent the problem in detecting the metabolism and blood flow in the corpus callosum which plays an important role in the pathogenesis. We have shown that the occlusion of the right PCA also produced a left unilateral agnosia which is one of the common neurological signs in the right MCA infarction. To tell whether the responsible lesion for the unilateral spatial agnosia differs between the PCA occlusion and the MCA occlusion, the correlation study should be carried out in a greater number of the subjects. Two distinctive neuropsychological manifestations, cerebral color blindness and prosopagnosia, have been considered to be produced by the bilateral occipital lesion. The PET studies disclosed reduction of blood flow and oxygen metabolism in both occipital lobes in our particular patient who exhibited cerebral color blindness and prosopagnosia.

[Brain glucose metabolism in a patient with Creutzfeldt-Jakob disease measured by positron emission tomography]

Sequential measurements of local cerebral glucose metabolism were performed in a case with Creutzfeldt-Jakob disease. The diagnosis was based on the characteristic clinical symptoms and EEG. Cerebral glucose metabolism (CMRGlc) was measured by positron emission tomography (PET) and 18F-fluorodeoxyglucose. CMRGlc was decreased to about 45% of the normal value. At that time, X-ray CT revealed little brain atrophy. The decrease of CMRGlc was prominent in cerebral cortices, but the metabolic decrease was slight in striatal body, cerebellum, and brainstem. The motor cortex and occipital lobe showed relatively preserved metabolism among the cerebral cortices. Six months after the first PET measurement, X-ray CT showed marked brain atrophy. Decrease of cerebral glucose metabolism advanced furthermore. However, the progress of the decrease was relatively small in the basal ganglia, brainstem, and cerebellar nucleus. These findings differ from the findings that was known by pathological study. These results suggest that measurement of CMRGlc by PET is useful for the early detection and for understanding of the pathophysiology of this disease.

[Value of 11C-methionine and PET in the diagnosis of low grade gliomas]

Ten patients with low grade glioma were examined with positron emission tomography (PET) using 11C-methyl-L-methionine (11C-Met). In 4 cases, follow-up study was performed after radiation therapy. 11C-Met uptake index was calculated by sequential arterial blood sampling and PET image on 45 minutes after injection. The tumor was clearly seen in the images, and uptake index in the tumor lesion was higher than that in the normal cortex. The uptake of 11C-Met was observed in a recurrent lesion that was confirmed by operation. 11C-Met uptake indices were decreased in the tumor lesions after radiation therapy. From these results PET with 11C-Met is a useful clinical tool for diagnosis of low grade gliomas.

[Positron emission tomography in acute disseminated encephalomyelitis: a case report]

Sequential positron emission tomography (PET) and single photon emission tomography (SPECT) were performed in an 11-year-old girl who was clinically diagnosed as acute disseminated encephalomyelitis (ADEM). She had fever, stupor, loss of sight and left hemiparesis on admission to our hospital. X-ray CT (XCT) demonstrated a hypodense lesion in the right fronto-parietal white matter. In the 1st PET study, CBF and CMRO2 were reduced in both hemispheric white and gray matter, particularly in the right fronto-parietal lesion. The XCT abnormality was improved in the subsequent scan when the patient had improved except visual disturbance. When visual disturbance was worsened again, and a new hypodense lesion was appeared in the left frontal white matter on XCT, the 2nd PET study was performed. CBF and CMRO2 were recovered except the left frontal white and gray matter. SPECT study was also performed and the image was almost similar to CBF image of PET scan. The changes and distributions of CBF and CMRO2 were related to her symptoms and clinical course. Reduced CBF and CMRO2 of whole brain is thought to be characteristic of ADEM. From the experiences of this case, PET measurements is useful for the understanding of neuronal functional abnormalities of ADEM, and is more useful for the detection of recovery or relapsing process than XCT.

PET evaluation of spinal cord tumor using 11C-methionine

A cervical cord tumor was examined with positron emission tomography using L-methyl-[11C]methionine. The radioactive tracer accumulated in the solid parts (but not in the associated cysts) of the neoplasm, which at histology was found to be an ependymoma.

[Quantitative evaluation of myocardial blood flow and myocardial fluoro-deoxyglucose uptake determined by PET before and after aorto-coronary bypass operation in patients with ischemic heart disease]

Absolute myocardial blood flow (MBF) and myocardial FDG uptake (MFU) in the fasting state were determined in 5 patients who underwent aorto-coronary bypass operation, using O-15 water, F-18 fluoro-deoxyglucose and dynamic PET before and after the operation. In the patent graft region, MBF was increased from 0.59 +/- 0.17 ml/min/g to 0.77 +/- 0.14 ml/min/g (p less than 0.05). Mean MBF was increased from 0.69 +/- 0.22 ml/min/g to 0.83 +/- 0.18 ml/min/g (p less than 0.05). MFU in the fasting state was significantly decreased in high MFU region compared with low MFU region (p less than 0.005). Quantitative evaluation of MBF and MFU before aorto-coronary bypass operation was quite useful to determine adequate indication of the operation.

[Positron emission tomography (PET) of an invasive ACTH-producing pituitary adenoma]

We report a case of large, invasive ACTH-producing pituitary adenoma with PET study. In CT scans, an intra- and supra-sellar mass diminished after replacement therapy for primary hypoadrenalism. Two years and seven months later, the tumor grew and extended into the neighboring structures. 11C-methionine accumulated markedly in the tumor, and depicted the lateral and dorsal extension.

[Positron emission tomography (PET) study in patients with meningiomas]

Regional hemocirculation and metabolism were evaluated in five patients with meningiomas using positron emission tomography (PET). Histological diagnoses were: two cases of meningotheliomatous type, one hemangiopericytic type, one fibroblastic type, and one transitional type. Regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), and metabolic rates of oxygen (rCMRO2) and glucose (rCMRG1) were measured with 15O2, C15O. 15O2, and 18F-fluorodeoxyglucose tracers. For the quantitative analysis, regions of interest were delineated on tumors, the peritumoral region, and the contralateral gray matter in comparison with age-corresponding 5 malignant gliomas and 5 normal volunteers. Tumor hemocirculatory parameters (rCBF: 57.2 +/- 22.6 ml/100 ml/min, rCBV: 7.95 +/- 3.27 ml/100 ml, mean + SD, n = 5) were markedly higher than those of the contralateral gray matter (p less than 0.05 by a Student-t test). The high values were consistent with angiographic findings of tumor staining and with abundant tumor vessels demonstrated by pathological examination. rCMRO2 was 2.15 +/- 0.80 ml/100 ml/min, which were comparable to those of the contralateral gray matter. Tumor rCMRG1 showed 4.76 +/- 2.37 mg/100 ml/min; the values of two cases were similar to the respective gray matter. The raised metabolic rate (rCMRO2/rCMRG1) therefore suggests rather aerobic glycolysis as compared with gliomas. Low rOEF (0.26 +/- 0.16) reveals an excessive blood flow beyond oxygen demand of the tumor. In the peritumoral regions, rCBF and metabolism fell slightly but rOEF reached a level similar to the contralateral gray matter, possibly due to hemocirculatory stasis caused by intracranial hypertension; in contrast, an unmatched reduction of rCBF and rCMRO2 implies tumor cells infiltration in gliomas.(ABSTRACT TRUNCATED AT 250 WORDS)

[Compartment analysis of 123I-IMP brain SPECT]

To clarify the kinetics of N-isopropyl [123I]p-iodoamphetamine (IMP) in the brain, 2-compartment analysis was applied for brain SPECT with 57-minute dynamic scan in 9 subjects. The model consisted of blood component and brain tissue component. Two transfer rate constants were defined; k1 showed the rate from the blood to the brain tissue, and k2 was that of back diffusion. The late scan was performed 210 minutes after the tracer injection. Suitable k values best fitting to the dynamic data were determined for all regions of interest. Predicted regional cerebral activity at 210 minutes using 57-minute dynamic data was well agreed with measured activity. These showed the kinetics of IMP in the brain was well described by the 2-compartment model. The partition coefficient (k1/k2 ratio) was as large as about 35, and almost constant in the various brain structures including hypoperfused areas. These findings indicated that the initial IMP images reflected the reasonable CBF distribution, which gave relatively reliable CBF values even if using microsphere model.

Differentiation between cerebral embolism and thrombosis on sequential CT scans

A differentiation between embolic versus thrombotic infarction has been attempted on the basis of sequential CT of 32 patients fulfilling our clinical and angiographic criteria for embolic or thrombotic cerebral infarction of the middle cerebral arterial distribution. In the 20 patients of the embolic group, a large homogeneous low attenuation area was seen in every case. In 18 of these 20 patients, the low attenuation area extended from the deep brain to the cortex. In the 12 patients of the thrombotic group, 10 had an inhomogeneous low attenuation area that did not involve the cortices in 8 cases. The frequency of hemorrhagic transformation in the embolic group was higher than in the thrombotic group. Computed tomography showed discrete areas of increased attenuation corresponding to an angiographically occluded artery in 7 of the 20 patients in the embolic group. Sequential CT can assist in differentiating between embolic and thrombotic infarction.

Analysis of bone scintigram data using speech recognition reporting system--data analysis with speech recognition system

Five hundred eighty bone scintigram reports were stored using a voice pattern recognition system in a general-purpose, middle-sized computer (ACOS-650). Bone scintigraphy carried out in our institute was examined by analyzing these data. The results of the examination showed that the introduction of this system made it possible to analyze all the data quickly. Before the introduction of this system, the data able to be analyzed had been restricted because of their complexity. The results also showed that this system would be useful for understanding the examinations carried out in the whole hospital as well as for analyzing metastatic tumors and the number of patients receiving examinations. Furthermore, this system would be helpful in the logical analysis of reports prepared by doctors.

[Analysis of regional blood flow, blood volume, oxygen and glucose metabolism in heterogeneous parts of untreated high grade gliomas using positron emission tomography (PET)]

A high resolution positron emission tomography (PET), HEADTOME III, has enabled us to visualize heterogeneous parts, i.e. viable, necrotic, and edematous portions in malignant gliomas, and to quantify regional hemocirculation and metabolism of the tumors using 15O and 18F-fluorodeoxyglucose tracers. Hemocirculatory and metabolic indices of regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), oxygen consumption (rCMRO2) and glucose consumption (rCMRGl) were studied in eight patients with untreated malignant gliomas. Regions of interest (ROIs) in PET images were focused on lesions corresponding to contrast enhancing areas, central low density areas of the tumors, and peritumoral low density areas in CT scans. In the viable portion of the gliomas, rCBV (5.20 +/- 1.18ml/100ml, mean +/- SD, n = 8) was significantly higher than that of the contralateral gray matter (p less than 0.05), which is suggestive of high vascularity; rOEF (0.36 +/- 0.16) and rCMRO2 (1.66 +/- 0.45ml/100ml/min) values markedly decreased (p less than 0.05, p less than 0.01). On the other hand, rCBF (36.3 +/- 13.0ml/100ml/min) and rCMRGl (5.94 +/- 1.15mg/100ml/min) were similar to that of the contralateral gray matter. A relative dissociation between oxygen and glucose metabolism indicates anaerobic glycolysis in the energy metabolism of malignant gliomas. In the central low density area, rCBF, rCBV, rOEF, rCMRO2, rCMRGl values decreased significantly from the viable portion and the contralateral gray matter. rOEF was markedly reduced in the central low density area as compared with that of the peritumoral low density area. The rOEF reduction indicates that oxygen metabolism of gliomas is the first to fail, accompanied by autoregulatory impairment of vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

[Radiochemotherapy-related changes in the brain parenchyma of glioma patients evaluated repeatedly by C15O2, C15O, 15O2, and 18F-fluorodeoxyglucose (FDG) PET]

The aim of this study was to evaluate effects of radiochemotherapy on blood flow and metabolism using C15O2, C15O, 15O2, and 18F-fluorodeoxyglucose positron emission tomography (PET). Conventional, external radiotherapy (180-200 cGy/5 fractions/week) using 60Co or a 10 MV linear accelerator was given in conjunction with chemotherapy of nimustine hydrochloride (ACNU) and tegafur (FT-207) in eight patients with gliomas. Regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), oxygen consumption (rCMRO2), and glucose consumption (rCMRG1) were longitudinally examined before the treatment, and at an early stage (within one month) and a late stage (three to thirty-one months with a mean of 12 months) after radiochemotherapy. Contralateral gray and white matter to the tumor was selected as regions of interest (ROIs), because these portions were irradiated with larger doses compared to other brain parenchymal regions through parallel opposing fields. Maximum doses to the ROIs varied between 20 and 61 Gy. Calculated as a function of time-dose-fractionation, nominal standard doses (NSD) ranged from 566 to 1729 ret, and 344 to 1062 neuret; equivalent doses (ED) equaled 432 to 1327 rads. At the early stage, rCBF and rCBV increased in the contralateral gray and white matter; gray matter rOEF decreased significantly (p less than 0.05 by a paired-t test) from that of the pretreatment study, probably due to decompression of the tumor bulk and radiochemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

[Vascular responses in cerebrovascular "Moyamoya" disease--evaluated by positron emission tomography]

We investigated cerebral blood flow and metabolism, and cerebral vascular response in 9 patients with cerebrovascular Moyamoya disease or unilateral Moyamoya phenomenon using positron emission tomography (PET). The subjects consisted of 5 men and 4 women, and were from 9 to 60 years old. Five patients had bilateral occlusion in the carotid fork with Moyamoya vessels (fulfilled the criteria of cerebrovascular Moyamoya disease), and four patients had unilateral Moyamoya phenomenon. The PET scanner used was the HEADTOME III, of which spatial resolution in clinical use was 10 mm full width at half-maximum (FWHM) in the image plane. Cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), cerebral oxygen extraction fraction (OEF), and cerebral blood volume (CBV) were measured in resting state by the 15O-labelled gases steady state method in every patient and 22 normal controls (17 men and 5 women, and from 26 to 64 years old). Consecutively cerebral vascular responses were measured by H215O autoradiographic method in resting state, hypercapnia, hypocapnia, and hypertension. Forced hypercapnia, hypocapnia, and hypertension were achieved by 7% CO2 inhalation, hyperventilation, and venous infusion of angiotensin II, respectively. CMRO2 of the whole brain was significantly lower in patients than in normal controls (p less than 0.05), and CBV of the lentiform nucleus significantly increased in patients (p less than 0.01). This reflected Moyamoya vessels in the basal ganglionic regions. In 3 of 5 patients with bilateral Moyamoya vessels, CBF and CMRO2 in the symptomatic cerebral hemisphere were lower than that in the nonsymptomatic hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)

[Changes in the (11C-methyl)-L-methionine uptake index in gliomas following radiotherapy]

We have studied changes in the (11C-methyl)-L-methionine (C-11 Met) uptake index in six glioma cases subsequent to radiotherapy, using positron emission tomography (PET) to evaluate the effects of radiotherapy on the amino acid metabolism of the tumor. The uptake index of the tumor represented as a percentage of the total count in the atrial blood recorded during a period of 45 min, showed an average of 0.037% and 0.039% prior to and within two months after the therapy, respectively. Out of three cases where a fall in the index was seen, two cases showed tumor regression in the size of the contrast enhanced lesion measured by CT; all three cases had a relatively long period of clinical and neurological amelioration. However, following a short period of clinical improvement, the other three patients with a rise in the index showed no change or tumor progression on CT. These findings indicate that changes in the C-11 Met uptake index can be a sensitive and precise indicator for evaluating the effect of radiotherapy on gliomas.

Sequential PET studies in neuro-Behçet's syndrome

A case of neuro-Behcet's syndrome is presented with sequential positron emission tomography (PET) studies. Regional cerebral blood flow (rCBF) and oxygen consumption (rCMRO2) were decreased in the brain lesion; however, on follow-up studies 3 months after steroid therapy rCBF and rCMRO2 had increased in the lesion, which demonstrated the reversibility of this disease. Such monitored improvement may accurately reflect the early stage of the disease and its response to steroid therapy.

[Cerebral blood flow and oxygen metabolism in ischemic cerebrovascular disease; embolic occlusion and thrombotic occlusion]

Using positron emission tomography and 15O-steady state method, cerebral blood flow (CBF), oxygen consumption and oxygen extraction fraction were measured in patients with embolic occlusion and in those with thrombotic occlusion in the carotid system. By the study of patients with embolic occlusion, we evaluated ischemic threshold of CBF for infarction to be 16 ml/100 ml/min. The area of "penumbra" could be estimated in regions with CBF value just above this threshold. In the patients with thrombotic occlusive lesion, we clarified that the efficiency of the collateral circulation was mainly related to the grade of peripheral atherosclerosis. These findings must be helpful to develop better strategy for treatments of cerebral ischemic disease.

Brain tumor imaging with synthesized 18F-fluorophenylalanine and positron emission tomography

Two patients with cerebral gliomas were studied with 18F-fluorophenylalanine, newly synthesized by the electrophilic substitution reaction, using positron emission tomography. The tracer accumulated markedly in the tumor lesion and delineated the extent of the lesion. This new tracer will be promising in the diagnosis of gliomas.

[Design concepts and preliminary performances of stationary-sampling whole-body high-resolution positron emission tomography: HEADTOME IV]

Design concepts and preliminary performances of a stationary sampling high-resolution whole-body positron emission tomograph, HEADTOME IV, were reported. The system comprises four layers of detector ring which consists of 768 BGO crystals with 3 mm width, 96 photomultiplier tubes arrayed on 825 mm circle. A sufficiently fine sampling-interval allows data sampling without scan motion along the transaxial plane. But an axial motion (Z-motion) is installed to interlace between adjacent planes. Preliminary performance characteristics were an in-plane resolution of 4.5 mm in full width at half maximum (FWHM), an axial resolution of 9.5 mm in FWHM, sensitivities of 14 and 24 kcps/(microCi/ml) for direct and cross planes, respectively, with 20 cm diam. cylindrical flood phantom. A large scale cache memory prepared for each plane allows a realtime correction for the deadtime and the radionuclide decay, and a realtime calculation of the rate constants using the weighted integral method.

Ewing's sarcoma with intracranial metastasis presenting depressed cerebral blood flow and metabolism in the contralateral gray matter

A case of Ewing's sarcoma with intracranial metastasis is reported with special reference to positron emission tomography (PET) evaluation of cerebral hemocirculation and metabolism after brain irradiation.

Electroencephalographic correlates of blood flow and oxygen metabolism provided by positron emission tomography in patients with cerebral infarction

Quantitative EEG data were analyzed statistically with respect to cortical cerebral blood flow (CBF) and oxygen metabolism (CMRO2) measured by positron emission tomography in 47 patients with unilateral cerebral infarction. Relative value of the square root of average power was used as a percentage power fraction (PPF) for each frequency category. Power ratio index (PRI) was calculated by dividing the combined delta-PPF and theta-PPF by the combined alpha-PPF and beta-PPF. Delta-PPF, theta-PPF and PRI correlated negatively with regional CBF (rCBF) and CMRO2 (rCMRO2) whereas alpha-PPF and beta-PPF correlated positively. In the acute stage, delta-PPF, alpha-PPF and PRI correlated with rCBF at all but the frontopolar region whereas the correlation with rCMRO2 was poor. Alpha-PPF and PRI correlated also with rCMRO2 in the frontal, central, parietal and occipital regions while delta-PPF correlated with rCBF only in the parietal and occipital regions in the subacute stage. In the chronic stage, all EEG quotients correlated significantly with both rCBF and CMRO2 in the central and parietal regions. In the frontopolar region, only the theta-PPF correlated with rCBF throughout. In the comparison of hemispheric mean values, the correlations were always closer for the affected hemisphere than for the contralateral hemisphere. Although hemispheric mean CBF and CMRO2 were significantly lower in patients with cortical infarcts on CT than in those with small subcortical infarcts, there was no significant difference in the EEG data between the 2 groups.

Linearization correction of 99mTc-labeled hexamethyl-propylene amine oxime (HM-PAO) image in terms of regional CBF distribution: comparison to C15O2 inhalation steady-state method measured by positron emission tomography

The radioisotope distribution following intravenous injection of 99mTc-labeled hexamethylpropyleneamine oxime (HM-PAO) in the brain was measured by single photon emission computed tomography (SPECT) and corrected for the nonlinearity caused by differences in net extraction. The "linearization" correction was based on a three compartment model, and it required a region of reference to normalize the SPECT image in terms of regional cerebral blood flow distribution. Two different regions of reference, the cerebellum and the whole brain, were tested. The uncorrected and corrected HM-PAO images were compared with cerebral blood flow (CBF) image measured by the C15O2 inhalation steady state method and positron emission tomography (PET). The relationship between uncorrected HM-PAO and PET-CBF showed a correlation coefficient of 0.85 but tended to saturate at high CBF values, whereas it was improved to 0.93 after the "linearization" correction. The whole-brain normalization worked just as well as normalization using the cerebellum. This study constitutes a validation of the "linearization" correction and it suggests that after linearization the HM-PAO image may be scaled to absolute CBF by employing a global hemispheric CBF value as measured by the nontomographic 133Xe clearance method.

[Cases similar to cerebrovascular moyamoya disease--investigation by angiography and computed tomography]

The criteria of the cerebrovascular Moyamoya disease is defined by the characteristic findings of its cerebral angiograms, as follows; 1) The internal carotid siphon is narrowed or obstructed bilaterally. 2) The "Moyamoya vessels" are observed at the base of the brain or the basal ganglionic regions. 3) Main trunks of the cerebral arteries such as the anterior, the middle, and/or the posterior cerebral arteries are often not or poorly visualized. 4) Its etiology is unknown. It has been known that the occlusion of the internal carotid fork with Moyamoya vessels is not infrequently seen in patients with tuberculous meningitis, sickle cell anemia, head trauma, and so on. In the definition of the disease, patients with known etiology and/or unilateral occlusion in the carotid fork must be excluded. However, the cases who cannot fulfil its criteria of the cerebrovascular Moyamoya disease, but have its characteristic Moyamoya vessels and collateral pathways have been reported. We investigated the findings of cerebral computed tomograms in 13 patients who did not fulfil the criteria of the cerebrovascular Moyamoya disease, but revealed the Moyamoya vessels. The subjects are 5 males and 8 females, ranging 15 to 70 years old. The past histories of 9 patients among them revealed hypertension, radiation therapy for pituitary adenoma, head trauma, aplastic anemia, and the Raynaud phenomenon. By angiographic evaluations, occlusions in the unilateral carotid forks were seen in 7 patients, and stenoses in those were in 5 patients. One patient showed only a severe stenosis in the horizontal portion of the middle cerebral artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Early and late stage positron emission tomography (PET) studies on the haemocirculation and metabolism of seemingly normal brain tissue in patients with gliomas following radiochemotherapy

Haemocirculatory and metabolic changes in seemingly normal brain tissue following radiochemotherapy including nimustine hydrochloride (ACNU) and tegafur (FT) were analyzed using oxygen-15 and fluorine-18 positron emission tomography (PET) in seven patients with gliomas. At an early stage (within one month) after radiochemotherapy, marginal increases in regional cerebral blood flow (rCBF) and cerebral blood volume (rCBV) were found contralateral to the tumour in gray matter which was apparently normal brain structure, as seen on computerized tomography (CT). The oxygen extraction fraction (rOEF) decreased significantly (p less than 0.05 by a paired-t test) from that of the pretreatment study, due to surgical decompression and radiochemotherapy. At the late stage (three to thirty-one months with a mean of thirteen months), rCBF decreased significantly from the early stage study (p less than 0.05); oxygen consumption (rCMRO2) fell in all cases significantly from the pretreatment study (p less than 0.01) and from the early stage study (p less than 0.05); consequently, rOEF remained unchanged at a level similar to the early stage study. Glucose consumption (rCMRG1) increased slightly as compared with the early stage study but failed to be restored to the level of the pretreatment study. Noteworthy was a coupling reduction of rCBF and rCMRO2--presumably, a late delayed effect of radiochemotherapy. These preliminary results indicate that with PET studies it may be possible to predict damage to normal brain tissue after radiochemotherapy.

Early CT finding in cerebral infarction: obscuration of the lentiform nucleus

Early computed tomographic (CT) findings (scans obtained within 6 hours of the onset of stroke) were retrospectively analyzed in 25 patients with embolic cerebral infarction of the middle cerebral artery or internal carotid artery distribution, including the lentiform nucleus, diagnosed on the basis of findings at sequential CT. CT scans were analyzed for the following: (a) an obscured outline or partial disappearance of the lentiform nucleus, (b) a slight decrease in tissue density, or (c) effacement of the cortical sulci. One or more of these findings was recognized in 23 of 25 patients (92%). The first finding was noted most frequently, and it appeared earliest. Obscuration of the lentiform nucleus was thought to be an important early sign of cerebral infarction, including the lentiform nucleus.

Measurement of absolute myocardial blood flow with H215O and dynamic positron-emission tomography. Strategy for quantification in relation to the partial-volume effect

An in vivo technique was developed for measuring the absolute myocardial blood flow with H215O and dynamic positron-emission tomography. This technique was based on a new model involving the concept of the tissue fraction, which was defined as the fraction of the tissue mass in the volume of the region of interest. The myocardium was imaged dynamically by positron-emission tomography, starting at the time of intravenous bolus injection of H215O. The arterial input function was measured continuously with a beta-ray detector. A separate image after C15O inhalation was also obtained for correction of the H215O radioactivity in the blood. The absolute myocardial blood flow and the tissue fraction were calculated for 15 subjects with a kinetic technique under region-of-interest analysis. These results seem consistent with their coronary angiographic findings. The mean value of the measured absolute myocardial blood flows in normal subjects was 0.95 +/- 0.09 ml/min/g. This technique detected a diffuse decrease of myocardial blood flow in patients with triple-vessel disease.

Delayed radiation necrosis of brain evaluated positron emission tomography

In four patients highly suspected of having delayed radiation necrosis of the brain, regional cerebral blood flow and metabolism were studied by using positron emission tomography (PET) with the 15O-labelled gases, 18F-fluorodeoxyglucose (18FDG). All four patients showed marked decreases in glucose and oxygen consumption in the lesion with that suspected pathology in comparison with those in normal brain parenchyma. Two of them were histologically proved to have radiation injuries (one was radiation necrosis and another was early delayed reactions). But one patient was histologically proved to have a recurrent tumor. Although metabolic study with PET using 18FDG is generally an excellent procedure for differentiation between radiation injuries and recurrent brain tumor, these results imply that in some cases the differential diagnosis is difficult even with 18FDG. The present study demonstrated considerably more pronounced reduction in the metabolism than the decrease of the blood flow in the lesion with radiation necrosis. This result would indicate that the primary effect causing the radiation necrosis is a direct effect of irradiation on neural tissue rather than the capillary damage.

Evaluation of regional differences of tracer appearance time in cerebral tissues using [15O] water and dynamic positron emission tomography

The tracer appearance time relative to the radial artery-sampling site has been evaluated in six brain locations in five human subjects using dynamic positron emission tomography (PET) following the bolus injection of H2(15)O. There was a maximum difference of +/- 2 s from the average in each location. To globally adjust the timing difference between the measured arterial curve and the PET scan, a correction method was developed based on a nonlinear least-squares fitting procedure. This new technique determined the global time delay with an accuracy of +/- 0.5 s. On the other hand, the linear backward extrapolation method resulted in a systematic error of 4 s.

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 H2(15)O 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.

Anatomical adjustments in brain positron emission tomography using CT images

We have developed a method that allows us to place regions of interest on X-ray CT (XCT) images that are automatically adjusted to positron emission tomography (PET) images from the same patient. A face mask with landmarks was used during PET and XCT studies for matching slice positions between PET and XCT. Anatomical locations in different images of the same slice can be accurately adjusted using the landmarks and a video system. In our clinical experience misadjustments of the slice position are on the average less than 2 mm in axial distance and 1.0 degrees in slice angle. The method is easily applicable to any PET or XCT device.

Changes of cerebral blood flow, and oxygen and glucose metabolism following radiochemotherapy of gliomas: a PET study

The effects of radiochemotherapy on blood flow, blood volume, and consumption of oxygen and glucose in tumor tissue and normal brain were studied by positron emission tomography. Thirteen patients with cerebral gliomas were included, and they were examined before, during, and within approximately 1 month after the therapy. The 15O-labeled gas steady state inhalation and the 18F-fluorodeoxyglucose methods were used. After the therapy, glucose consumption and blood volume decreased (p less than 0.03) in the tumoral tissue. In the structurally (CT) normal gray matter, blood flow, blood volume, and oxygen consumption did not show any significant changes; oxygen extraction fraction, glucose consumption, and glucose extraction fraction, however, decreased significantly (p less than 0.05, less than 0.02, and less than 0.03, respectively).

[Regional myocardial blood flow quantitatively measured using O-15 water and dynamic positron emission tomography]

This study was performed to measure regional myocardial blood flow (MBF) quantitatively using dynamic positron emission tomography (PET) and O-15 water. The subjects consisted of two normal volunteers, four patients with normal coronary angiograms (CAG), two patients with angina pectoris (3-vessel disease) and three patients with myocardial infarction. O-15 water (15-20 mCi) was injected via the cubital vein in a bolus, and dynamic PET was performed. MBF was calculated according to the method of Iida. The region of interest (ROI) was selected on the left ventricular wall (septum, anterior and lateral walls) and MBF was calculated in each ROI. In normal volunteers, MBF was 1.07 to 1.17 ml/g/min. It was 0.96 to 1.02 ml/g/min in patients with normal CAG, and 0.53 to 0.64 ml/g/min in patients with angina pectoris in the ischemic area. In patients with myocardial infarction, MBF was so diminished in the infarcted area as detected by 2-DE or ECG that the absolute value was almost 0 ml/g/min. In patients with angina pectoris, there was no definite defect on the MBF image, but we could estimate the severity of coronary stenosis by quantifying the MBF. The clinical advantages of this method include estimation of the severity of coronary arterial stenosis in the resting state.

Positron emission tomographic evaluation of radiochemotherapeutic effect on regional cerebral hemocirculation and metabolism in patients with gliomas

Hemocirculatory and metabolic changes in tumor regions and the remote brain structure were analyzed using oxygen-15 and fluorine-18 positron emission tomography (PET) in eight patients with gliomas after radiation and chemotherapy of 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) and N-(2-tetrahydrofuryl)-5-fluorouracil (FT-207). In the tumor regions after the radiochemotherapy, regional cerebral blood flow (rCBF) and cerebral blood volume (rCBV) varied widely and there was a tendency for oxygen consumption (rCMRO2) to fall. The change in glucose consumption (rCMRG1) was especially noteworthy with regard to clinical correlations. Six patients with decreased rCMRG1 values had 16% to 29% regressions in tumor size measured by X-ray computerized tomography (CT), and showed some period of clinical relief. In contrast, one patient with an increased rCMRG1 value had some progression of tumor growth, and there were no clinical amelioration. The hemocirculation and metabolism of the contralateral gray matter seem to fluctuate by various factors as intracranial pressure and the effectiveness of the therapy. In gliomas therapy, tumor rCMRG1 values can be a good indicator of therapeutic effectiveness.

[Oxygen extraction fraction and cerebrovascular reactivity to PaCO2 changes in ischemic brain measured by positron emission tomography]

Interrelations between oxygen extraction (OEF) and cerebrovascular reactivity to PaCO2 change (VRCO2) in ischemic brain were measured by the 15O gases steady state method and the H215O autoradiographic method using a positron emission tomography. OEF at rest and VRCO2 for hypercapnia and hypocapnia were assessed successively in five cross sections of 10 mm image resolution. With each study correlation coefficients between OEF and VRCO2 were calculated using 30 to 40 regions of interest. In hypercapnic measurements those which had a larger ischemic region resulted in a higher incident of a negative correlation. Fifteen of 19 studies (79%) showed the negative correlation. From the regression lines which showed significant correlation a mean OEF at VRCO2 =0 was 0.54 +/- 0.09, which might indicate the point at the maximal dilatation of the resistance vessels. On the other hand, in hypocapnic studies only five of 18 (28%) showed apositive correlation, and the other measurements showed diffusely negative VRCO2 over the whole regions in the brain.

[Cerebral blood flow measurement using H2(15)O intravenous injection and positron emission tomography: description of implementation and applications to cerebrovascular reactivity measurement]

The method for cerebral blood flow (CBF) measurement using an H215O intravenous injection and positron emission tomography (PET) was implemented, examined and applied to measure cerebrovascular reactivity to PaCO2(VRCO2) and to MABP (VRBP) in normal brain and in ischemic brain. Immediately after bolus intravenous injection of 30-40 mCi H2(15)O, a time-activity curve of H2(15)O concentration in the arterial blood and in the brain were measured for 60 sec by a beta detector and a PET, respectively. The PET was HEADTOME III and measured five planes. CBF was determined by the table-look up method based on the autoradiographic principle. Six volunteers were studied to examine region of VRCO2, and a moyamoya patient and a stroke patient with a bilateral-intracarotid circulation defect were studied to examine VRCO2 and VRBP in ischemic brain. The studies were carried out so as to be followed two or three H2(15)O CBF measurements with changing PaCO2 or MABP after control study at rest condition. In addition, prior to the H2(15)O study O15 gas steady state study was performed on all subjects. Validity of the method examined by simulation studies showed 3% error per 1 sec time shift of the artery curve for 60 sec PET scan duration and the error was rapidly increased to the shorter scan duration. Inhomogeneity of a brain tissue gave mild under-estimation by 5% for 60 sec PET scan duration. VRCO2 in normal brain was revealed to be almost uniform except that the infratentorium area showed a slight higher VRCO2 than the supratentorium area. The ischemic brain showed a negative correlation between VRCO2 and oxygen extraction fraction (OEF), and a positive correlation between VRBP and OEF.

A system for cerebral blood flow measurement using an H215O autoradiographic method and positron emission tomography

A system for CBF measurement using an H215O autoradiographic method and positron emission tomography (PET) has been designed and installed as a clinical tool. Following an intravenous injection of H215O, a radioactivity accumulation in the brain tissue for 60 s and a continuous record of radioactivity in arterial blood were measured by a high counting speed PET device and a beta-ray detector, respectively, and CBF was calculated by a table-lookup procedure. First, this method was compared with the C15O2 inhalation steady-state method on 17 cerebrovascular disease patients and four normal subjects. The two values for CBF agreed with each other when H215O autoradiographic method was applied by correction for the dispersion in the measured arterial radioactivity-time curve. However, without the correction, the CBF by the H215O autoradiographic method revealed substantial overestimation by 30.6 +/- 17.5%. A reduced gray/white ratio of CBF was also observed in the H215O autoradiographic method. Second, simulation was performed in order to determine optimal accumulation time by PET scan; the result was that errors due to dispersion and time mismatch became critical as the accumulation time was shortened to less than 60 s.