[Sequential analysis of the integrated images of PET, CT and MR in malignant brain tumors before and after radiotherapy]

11C-methyl-L-methionine (C-11 Met)PET, CT and MR imaging were performed in eleven patients with malignant brain tumors before and after RT to evaluate the usefulness of positron emission tomography (PET) in monitoring tumor response to radiotherapy (RT). The subjects included five cases of intracranial malignant lymphoma (ICML) and six cases of glioma. C-11 Met uptake by the tumor (T) and the contralateral gray matter (NT) was calculated on the PET images. The mean T/NT ratio of the ICMLs and gliomas changed from 2.33 and 1.87, respectively, before RT to 1.31 and 1.58, respectively, after RT.No significant difference was found between the T/NT ratios before and after RT in either the ICMLs or the gliomas (t-test). We tentatively defined the minimum T/NT ratio, 1.2, as the threshold between tumor and nontumor regions. Tumors with a ratio of 1.2 or more were imaged as "hot" (MET) and coincided with CT or MR image lesions which were visualized as contrast-enhancing (CE) and low-density (LD) or high-intensity (HI). The relationships between PET, CT and MRI lesions were classified as follows: Type I (MET < or = CE), Type II [CE < MET < LD (HI)], Type III [LD(HI) < or = MET]. MET lesions extending regionally ( > 1 cm) beyond the respective CT or MR image lesions were designated "MET-extension" and LD (HI) lesions protruding ( > 1 cm) beyond the MET lesions were recorded as "LD (HI)-extension" on the integrated images. The type II pattern of the MET areas in all five cases of ICML before RT had changed to Type I in one case, Type III in one case and Type II in three cases, after RT, while the two Type II patterns and four Type III patterns of the gliomas had converted to four Type II and two Type III patterns. These findings indicate that gliomas tend to invade into areas of peritumoral edema more than ICMLs. There were two ICML MET-extension sites in the cortex before RT, as opposed to two in the cortex, one in the basal ganglia, one in the thalamus, and one in the corpus callosum among the gliomas. On follow-up CT or MR images MET-extension (75%) had converted to a CE or LD (HI) region. Four ICML LD (HI)-extension sites before RT were found in periventricular white matter, versus one in the cortex and three in the white matter among the gliomas. LD (HI)-extension appeared to represent vascular edema because it decreased or diminished after completion of therapy. Sequential analysis of integrated C-11 Met PET, CT and MR images is useful in detecting the extent of tumor infiltration by ICMLs and gliomas, particularly at an early stage, and for evaluating the effect of RT in the treatment of both.

[Hemocirculation and metabolism in intraventricular tumors: kinetic analysis of glucose metabolism]

To estimate hemocirculation and proliferating activity of intraventricular tumor, we measured kinetic rate constants (k1, k2, k3) and glucose metabolic rate (kinetic-rCMRGl) using dynamic positron emission tomography (PET), as well as regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), oxygen metabolic rate (rCMRO2) and autoradiographic rCMRGl (arg-rCMRGl), in patients with intraventricular tumor. The subjects included ten patients, five males and five females, aged from 13 to 53 years with a mean age of 32 years old. Eight tumors were located in the lateral ventricle and two extended into the third ventricle through the foramen of Monro. Another two tumors were located in the fourth ventricle. Histological diagnosis was as follows: five cases of central neurocytoma, one subependymal giant cell astrocytoma, one ependymoma, one choroid plexus carcinoma, one subependymoma, and one meningioma. Tumor lesion on the PET images was determined using CT or MRI, which was performed at levels equivalent to those for the PET scans. For quantitative analysis, regions of interest (ROI) on PET images were delineated on the tumor and the contralateral gray matter. Hemocirculation (rCBF, rCBV) of the tumor was similar to or higher than that of the contralateral gray matter, which corresponded to neuroradiological findings of abundant tumor vessels. Oxygen metabolic parameters (rOEF, rCMRO2) were significantly lower than those of the contralateral gray matter. Especially, low rOEF resulted in an excessive blood flow beyond oxygen demand of the tumor. The raised metabolic rate (rCMRO2/rCMRGl), as compared with that of meningiomas or malignant gliomas, suggested aerobic glycolysis. The kinetic rate constants of tracer transport from blood to brain (k1), reverse transport from brain to blood (k2), and phosphorylation (k3) were analyzed according to the three-compartment model of 18F-fluorodeoxyglucose (18FDG). Tumor k1 and k2 values were similar to or higher than those of the contralateral gray matter, suggesting high permeability due to lack of blood-brain barrier and an abundant blood supply. Tumor k3 value, an indicator of hexokinase activity, and kinetic-rCMRGl were lower in six of eight patients. These six patients have been free from tumor recurrence or regrowth, postoperatively. In the other two patients, tumor kinetic-rCMRGl was similar to or higher than that of the contralateral gray matter, suggesting high activity of proliferation. However, one patient received irradiation and has been followed up, and the other received total resection and has shown no recurrence. Functional information concerning intraventricular tumor is obtained by PET analysis, and kinetic analysis of the rate constants is useful for interpreting a detailed metabolic process of glucose, and provides additional information on intraventricular tumor aggressiveness.

New display methods of combined topographic EEG and cerebral blood flow images in the evaluation of cerebral ischemia

To evaluate complicated changes in the EEG and cerebral blood flow (CBF) in cerebral infarction, EEG was recorded under various blood pressure levels, during CBF measurement with positron emission tomography, in patients with chronic cerebral infarction. Newly developed display methods which combine topographic EEG and its significance probability mapping with CBF, clearly provided objective measures of changes in EEG parameters and CBF, during induced hypo- and hypertension.

[Positron emission tomographic evaluation for frontal hypertrophic cranial pachymeningitis using 11C-methyl-L-methionine]

A case of frontal hypertrophic cranial pachymeningitis was presented with positron emission tomography (PET) using (11C-methyl)-L-methionine (11C-Met). A 55-year-old male developed right hemiparesis after generalized tonic convulsion one month prior to admission. MR images revealed patchy enhancement extending from the dura mater to the cerebral parenchyma surrounding high T2-weighted signal in the left frontal region. Left carotid angiogram showed atresia of the rostral superior sagittal sinus and obliteration of the cortical veins associated with compensatory venous channels coursing in the frontal deep white matter. PET demonstrated high 11C-Met uptake in the area corresponding to the enhancing lesion on the MR images. The ratio of lesion/normal cortex was 1.58 as an indicator of selective uptake in the lesion. The contralateral temporal gray matter was representative of a normal cortex. In contrast, 11C-Met did not accumulate in the frontal white matter where T2-weighted MR images showed abnormal high intensity lesion. This suggested that the frontal white matter lesion was derived from vasogenic edema due to venous infarction. The patient underwent an uneventful exploratory biopsy. The dura mater had proliferated to a thickness of 3.5mm and was tightly adherent to the left middle frontal gyrus. Microscopically, the thickened dura mater where the tracers had accumulated was composed of abundant collagenous fibers together with diffuse infiltration of inflammatory cells, including predominantly lymphocytes, plasma cells, and neutrocytes. The lymphocytes, which proved positive in both UCHL-1 and L26 staining, had no atypism. Histological findings corresponded to hypertrophic pachymeningitis. Met-PET clearly represented viable and infiltrative zones of inflammatory cells. The patient's neurological symptoms and signs gradually improved. Follow-up MR images three months after the surgery showed the enhancing lesion to be diminished and a marked regression of the vasogenic edema. Spatial determination of viable lesions permitting differentiation from biological inactive or vasogenic edema is an important guideline in selecting an appropriate surgical procedure in the diagnosis and treatment of hypertrophic cranial pachymeningitis. Met-PET would appear useful in delineating inflammatory lesions such as hypertrophic cranial pachymeningitis.

Regional cerebral blood flow response in gray matter heterotopia during finger tapping: an activation study with positron emission tomography

We examined regional cerebral blood flow response in a patient with gray matter heterotopia located beneath the sensorimotor cortex during a finger tapping task. We found regional cerebral blood flow was specifically increased during contralateral finger tapping. This indicated the possibility of functional differentiation of the ectopic neurons despite incomplete migration.

Clinical positron emission tomography for brain tumors: comparison of fludeoxyglucose F 18 and L-methyl-11C-methionine

PURPOSE

To evaluate the differences between fludeoxyglucose F 18 (FDG) and L-methyl-11C-methionine (11C-methionine) as tracers for positron emission tomography (PET) in the evaluation of brain tumors.

METHODS

We analyzed 10 patients with histologically verified cerebral glioma or meningioma and 1 patient with a neuroradiologic diagnosis of low-grade glioma by using FDG, 11C-methionine, and PET. We qualitatively and quantitatively evaluated the extent and degree of accumulation of FDG and 11C-methionine in the tumor tissue.

RESULTS

Although PET with FDG depicted malignant tumors as a hot spot in all cases, it was not able to delineate the extent of the tumor. Conversely, PET with 11C-methionine outlined the tumors as areas of increased accumulation of 11C-methionine, regardless of the degree of malignancy.

CONCLUSION

PET with FDG and with 11C-methionine can play complementary roles in the evaluation of brain tumors.

Analysis of plasma metabolites during human PET-studies with three receptor ligands, [11C]YM-09151-2, [11C]doxepin and [11C]pyrilamine

Carbon-11 labeled metabolites in human plasma were analyzed by high-performance liquid chromatography during positron emission tomography (PET) studies using the dopamine D2 ligand [11C]YM-09151-2 as well as the histamine H1 ligands [11C]doxepin and [11C]pyrilamine. For all the three tracers, blood clearance of the radioactivity was extremely rapid after an i.v. injection. The plasma protein-binding of [11C]YM-09151-2 and [11C]doxepin had protective effects upon the metabolic alteration of the ligands, whereas [11C]pyrilamine was free from the protein-binding and immediately degraded. The degradation of [11C]doxepin was more rapid in epileptic patients on medication than in normal subjects. These results indicate that analysis of metabolites in the plasma is necessary to determine the accurate arterial input function for quantitative PET measurement.

Spinal cord ependymoma: a positron emission tomographic study with (11C-methyl)-L-methionine

An intramedullary spinal cord ependymoma was studied by positron emission tomography (PET) using (11C-methyl)-L-methionine (11C-Met). MRI showed a homogeneously enhancing tumour at C6-T2 with cysts at its rostral and caudal ends. Sagittal PET images demonstrated high 11C-Met uptake in the solid portion of the tumour, particularly ventrally at C7-T2, where viable tumour cells proliferated in association with abundant perforating vessels. Met-PET would appear useful for delineating the viable portion of intramedullary ependymomas.

Central benzodiazepine receptor distribution after subcortical hemorrhage evaluated by means of [123I]iomazenil and SPECT

BACKGROUND AND PURPOSE

[123I]Iomazenil is a single-photon emission computed tomography (SPECT) tracer that selectively binds to central benzodiazepine receptor in the neuron membrane. With this ligand, we studied the central benzodiazepine receptor distribution in the cortex remote from subcortical hematoma in intracerebral hemorrhage patients.

METHODS

Four patients with unilateral putaminal hemorrhage and one patient with right thalamic hemorrhage were studied (mean +/- 1 SD age, 50.0 +/- 8.8 years). The initial volume of hematoma ranged from 4.3 to 31.0 mL (mean +/- 1 SD, 17.5 +/- 12.3 mL). SPECT images obtained 3 hours after intravenous administration of [123I]iomazenil (167 MBq/750 ng) were analyzed. In three patients, perfusion was evaluated with [123I]IMP. On SPECT images, the radioactivity ratio of the ipsilateral to the contralateral cerebral cortex (I/C ratio) or of the contralateral to the ipsilateral cerebellar hemisphere (C/I ratio) was measured.

RESULTS

The I/C ratio for iomazenil was significantly decreased compared with unity in the temporal lobe (0.84 +/- 0.08, P < .01) and the parietal lobe (0.87 +/- 0.10, P < .05), but the C/I ratio in the cerebellum (1.00 +/- 0.03) was not. The C/I ratio for perfusion in the cerebellar cortex (0.83 +/- 0.04, P < .01) was significantly decreased compared with that in normal subjects.

CONCLUSIONS

Central benzodiazepine receptor-[123I]iomazenil binding was decreased in the ipsilateral cerebral cortex remote from the subcortical hematoma. This preliminary result may facilitate further study of the potential damage of the cortical neurons remote from subcortical hematoma.

Evaluation of cerebral infarction with iodine 123-iomazenil SPECT

This study evaluates ischemic damage to central benzodiazepine (BZD) receptor binding in the brain with [123]iomazenil SPECT in relation to CT hypodense lesions and blood flow abnormalities.

METHODS

Nine patients with middle cerebral artery territory infarction were studied. Iomazenil images obtained 180 min postinjection were analyzed for BZD receptor binding. The cortical infraction, visualized as CT hypodense area on CT, the peri-infarct area, visualized as normodensity surrounding the infarction on CT, the intrahemispheric remote area and the cerebellum were analyzed by taking the ratio of the lesion to contralateral mirror region (L/C ratio). CT during the chronic stage and perfusion images obtained during the smallest time difference between the two studies were used for comparative analysis.

RESULTS

The mean L/C ratio of iomazenil uptake was 0.53 +/_ 0.08, 0.79 +/- 0.07, 0.98 +/- 0.03 and 1.00 +/- 0.04 in the infarct, peri-infarct and remote areas and the cerebellum, respectively. The infarct and peri-infarct areas showed significant decrease compared with unity. The corresponding mean L/C ratio for blood flow was 0.52 +/- 0.08, 0.73 +/- 0.07, 0.83 +/- 0.09, and 0.80 +/- 0.07, respectively. In all areas, the ratios were significantly decreased compared with unity. There was significant difference between the L/C ratio for blood flow and iomazenil in the remote area and the cerebellum.

CONCLUSION

Iodine-123-iomazenil SPECT imaging may provide new information on ischemic damage to the brain, particularly neurons.

Carbon-11-methionine PET evaluation of intracerebral hematoma: distinguishing neoplastic from non-neoplastic hematoma

We evaluated whether PET with L-methyl-11C-methionine (11C-methionine) was clinically useful in distinguishing neoplastic from non-neoplastic intracerebral hematoma.

METHODS

We examined eight patients with neoplastic (n = 4) or non-neoplastic (n = 4) intracerebral hematomas between 5 and 68 days after the bleeding episode using PET with 11C-methionine (Met-PET).

RESULTS

Carbon-11-methionine accumulated in the area surrounding the hematoma in both groups, except in one patient with an acute hypertensive hematoma. Between 22 and 45 days after the ictus, non-neoplastic hematomas showed increased 11C-methionine accumulation largely in accordance with the contrast-enhanced areas on CT or MR images; whereas between 14 and 68 days after bleeding, neoplastic hematomas showed increased 11C-methionine accumulation that extended beyond the contrast-enhanced areas on CT or MR images. The intensity of 11C-methionine accumulation in tumor tissue was greater than that in non-neoplastic hematomas.

CONCLUSION

Preliminary results suggest that Met-PET can distinguish neoplastic from non-neoplastic hematomas on the basis of differences in lesion extent compared with CT or MR findings.

MR diagnosis of subacute and chronic subarachnoid hemorrhage: comparison with CT

OBJECTIVE

The purpose of our study was to compare the value of MR imaging with CT in the diagnosis of subarachnoid hemorrhage in the subacute and chronic stages (> 3 days after the hemorrhagic episode).

MATERIALS AND METHODS

We performed 42 MR examinations using a 0.5-T unit in 37 patients with subarachnoid hemorrhage caused by a ruptured aneurysm. Examinations were done 4-75 days after the ictus. We obtained 40 T1-weighted, 11 proton density-weighted, 15 T2-weighted, and 28 moderately T2-weighted images. CT was also performed in all patients within 24 hr of the MR examination. Confirmation of the presence of subarachnoid hemorrhage at the time of the MR examination was made by CSF examination using lumbar puncture or surgical findings.

RESULTS

In the subacute and chronic stages, subarachnoid hemorrhage was seen as an area of high signal intensity on T1-weighted, proton density-weighted, T2-weighted, and moderately T2-weighted MR images in 63%, 90%, 25%, and 92% of cases, respectively. On CT scans, subarachnoid hemorrhage was seen as an area of high attenuation in only 46% of cases. Especially in the chronic stage, subarachnoid hemorrhage was seen as an area of high signal intensity more frequently by MR imaging than by CT (90% on T1-weighted images; 100% on proton density-weighted images; 25% on T2-weighted images; 100% on moderately T2-weighted images; and 10% on CT scans). High-signal-intensity subarachnoid hemorrhage was demonstrated by MR imaging until a maximum of 39 days after the ictus, whereas high-attenuation subarachnoid hemorrhage was demonstrated by CT until a maximum of 17 days after the ictus.

CONCLUSIONS

Our findings show that MR imaging is superior to CT for the diagnosis of subacute and chronic subarachnoid hemorrhage. MR imaging is especially useful for the diagnosis of chronic subarachnoid hemorrhage.

[Kinetics of glucose metabolism in central neurocytomas]

To estimate proliferating activity of central neurocytoma, we measured kinetic rate constants and glucose metabolic rate (kinetic-rCMRGI) using dynamic positron emission tomography (PET), as well as autoradiographic rCMRG1 (arg-rCMRG1), in patients with histologically verified central neurocytoma. The subject included five patients, four males and one female, aged from 23 to 53 years with a mean age of 41 years old. All tumors were located in the lateral ventricle and two extended into the third ventricle through the forearm of Monro. Tumor lesion on the PET images was determined using CT or MRI, which was performed at levels equivalent to those for the PET scans. The kinetic rate constants of tracer transport from blood to brain (k1), reverse transport from brain to blood (k2), and phosphorylation (k3) were analyzed according to the three compartment 18F-fluorodeoxyglucose (FDG) model. For quantitative analysis, regions of interest (ROI) on PET images were delineated on the tumor and the contralateral gray matter. Tumor k1 and k2 values were similar to or higher than those of the contralateral gray matter, suggesting high permeability due to lack of blood-brain barrier. Tumor k3 value, an indicator of hexokinase activity, and kinetic-rCMRG1 were exceedingly lower in three of five patients. These three patients have been free from tumor recurrence or regrowth, postoperatively. The other two patients, tumor kinetic-rCMRG1 was similar to or higher than that of the contralateral gray matter. One patient suffered from tumor regrowth shortly after resection, and the other has been followed up postoperatively. Thus, k3 and kinetic-rCMRG1 are indicative parameters of proliferative activity in central neurocytoma.

Blood flow and metabolism of central neurocytoma: a positron emission tomography study

BACKGROUND

New World Health Organization classifications have categorized central neurocytomas as neuronal tumors. The differential diagnosis between central neurocytomas and other tumors is important for selection of the optimal therapy modality for the management of intraventricular tumors. To characterize the pathophysiology and proliferating activity of central neurocytoma accurately, cerebral blood flow and metabolism in five patients with central neurocytoma were studied using positron emission tomography (PET).

METHODS

Tracers used for the present study included C15O2, C15O, 15O2, and 18F-fluorodeoxyglucose (FDG). Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), cerebral metabolic rate of oxygen (rCMRO2), and cerebral metabolic rate of glucose (rCMRGl) were quantitatively analyzed in tumor lesions and the contralateral gray matter. Four patients with central neurocytoma underwent a complete PET study, including all circulatory and metabolic parameters; one patient was studied with 11C-methyl-L-methionine and FDG tracers.

RESULTS

Tumor rCBF and rCBV were higher than comparable values in the contralateral gray matter in three of four patients. This high level of perfusion corresponds to angiographic findings that show intense tumor staining in tumors fed by perforated arteries. Tumor rOEF and rCMRO2 were significantly lower than corresponding values in the gray matter (rOEF, P < 0.01; rCMRO2, P < 0.05 by Student's t test). Tumor rCMRGl ranged from 2.68 to 6.26 mg/100 ml/minutes and did not exceed contralateral gray matter values in any of the five patients. Tumor rCMRGl was significantly lower (P < 0.02) than the gray matter rCMRGl. One tumor exhibited a relatively high value of rCMRGl (comparable to gray matter rCMRGl), and increased in size 4 months after partial resection. No other tumors appeared during postoperative follow-up periods that ranged from 4 to 135 months.

CONCLUSIONS

Circulation and metabolism parameters measured by PET offer insight into the biologic characteristics of central neurocytoma. Tumor rCMRGl may be an indicator of the proliferating activity in central neurocytoma.

Acute subarachnoid hemorrhage: MR imaging with fluid-attenuated inversion recovery pulse sequences

PURPOSE

To evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging sequences in the detection of acute subarachnoid hemorrhage (SAH).

MATERIALS AND METHODS

MR imaging with FLAIR sequences was performed with a 0.5-T superconducting unit in 20 patients (aged 30-72 years) with acute SAH due to a ruptured aneurysm and in 27 control subjects (aged 32-72 years). FLAIR images were obtained 2 hours to 2 days after ictus. Findings were evaluated and compared with computed tomographic (CT) findings.

RESULTS

In all patients, acute SAH was clearly demonstrated as an area with signal intensity that was high relative to that of the normal cerebrospinal fluid and surrounding brain parenchyma at FLAIR imaging. This sequence was especially useful in demonstration of acute SAH in the posterior fossa, which was difficult to show at CT because of beam-hardening artifacts. In a double-blind comparison, no FLAIR images acquired in control subjects were confused with those acquired in control subjects were confused with those acquired in patients.

CONCLUSION

FLAIR sequences reliably provide diagnostic images in patients with acute SAH.

Aging effect on neutral amino acid transport at the blood-brain barrier measured with L-[2-18F]-fluorophenylalanine and PET

Neutral amino acids (NAAs) are transported from the blood to the brain using the same carrier system in a competitive fashion. The purpose of this study is to establish a method for evaluating neutral amino acid transport at the blood-brain barrier (BBB) in humans and to examine the aging effect of amino acid transport.

METHODS

A dynamic PET study with L-(2-18F)-fluorophenylalanine (18F-Phe) was performed in 14 normal volunteers (age 21-71 yr; mean +/- s.d., age range 48.0 +/- 17.1 yr). By using a two-compartment model analysis and a weighted integration technique, the influx rate constant K1, the efflux rate constant k2 and distribution volume Vd of 18F-Phe were estimated in various brain structures.

RESULTS

The value of K1 was inversely correlated with plasma NAA concentration (r = -0.69, p < 0.01). The cerebellum showed the highest value of K1, while the white matter showed the lowest. There was no significant change in K1 during aging. The value of k2 was significantly increased with age.

CONCLUSION

No decline of K1 during aging indicated that NAA transport from the blood to the brain is a limiting process of age in amino acid incorporation. Fluorine-18-Phe PET imaging is a feasible method to study NAA transport at the BBB in vivo in humans and can be applied to pathological conditions of the brain.

[Kinetic analysis of glucose metabolism in meningiomas--comparison with malignant gliomas]

We measured kinetic rate constants and glucose metabolic rate (kinetic-rCMRGl) using dynamic positron emission tomography (PET), as well as regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), oxygen metabolic rate (rCMRO2) and autoradiographic rCMRGl (arg-rCMRGl), in patients with meningioma. Ten patients including one recurrent case, two males and eight females aged from 44 to 71 years with a mean age of 54 years old, were studied prior to surgical interventions. Histological diagnosis was as follows: seven cases of meningothelial type, two cases of angiomatous type and one fibrous type. For quantitative analysis, regions of interest (ROI) on PET images were delineated on the tumor and the contralateral gray matter in comparison with eight cases with malignant gliomas (five cases of malignant astrocytoma and three cases of glioblastoma, aged from 14 to 70 years with a mean age of 41 years old). Hemocirculation of the tumor was exceedingly higher than that of the contralateral gray matter, which corresponded to neuroradiological findings of abundant tumor vessels. Low rOEF implicated an excessive blood flow beyond oxygen demand of the tumor. The raised metabolic rate (rCMRO2/rCMRGl) suggested rather aerobic glycolysis as compared with malignant gliomas. The kinetic rate constants of tracer transport from blood to brain (k1), reverse transport from brain to blood (k2), and phosphorylation (k3) were analyzed according to the three compartment model of 18F-fluorodeoxyglucose (FDG). Tumor k1 and k2 values markedly increased in all examined cases, suggesting high permeability due to lack of blood-brain barrier and an abundant blood supply.(ABSTRACT TRUNCATED AT 250 WORDS)

Serial positron emission tomography with fludeoxyglucose F 18 in Creutzfeldt-Jakob disease

We serially examined a patient with Creutzfeldt-Jakob disease using fludeoxyglucose F 18 and positron emission tomography. Marked cerebral hypometabolism reflected clinical deterioration in the early stages of Creutzfeldt-Jakob disease when no parenchymal abnormalities were present on MR imaging.

[Positron emission tomographic findings of subependymal giant cell astrocytoma developed in tuberous sclerosis--a case report]

Tuberous sclerosis (TS) is well known to be occasionally associated with subependymal giant cell astrocytoma (SGCA). SGCA is considered to be a benign tumor in its clinical course and morphology. However, this tumor is grown sometimes so rapid and caused hydrocephalus. To our knowledge, little is known about hemocirculation and metabolism, particularly in relation with proliferating activity of TS and SGCA. We measured hemocirculation and metabolism of SGCA developed in a case of TS using positron emission tomography (PET). A 13-year-old-boy who had frequently developed convulsions four months after birth. He was diagnosed as TS and had been medically treated with anticonvulsants, since multiple intraventricular calcifications were detected by CT, at the age of five months. The convulsions had been well controlled. In March 1993, he presented with syncopal attack and admitted to our hospital. CT showed multiple subependymal nodules. Among the nodules, one of the left anterior horn exceeded 2cm in size obliterated Monro's foramen. The tumor was homogeneously enhanced with contrast medium. The lesion detected by postcontrast T1-weighted MR imaging had almost the same status as that by CT. T2-weighted image revealed cortical tubers as high intensity area at the left frontal and parietooccipital regions. PET was performed with the Headtome IV. Hemocirculation of the tumor was lower than that of contralateral gray matter, which suggested poor blood supply. The oxygen and glucose metabolism of the tumor were decreased compared with contralateral gray matter, indicative of a low activity of proliferation and a clinically benign tumor in the present case.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of partial volume effect in quantitative measurement of regional cerebral blood flow using positron emission tomography]

Effects of limited spatial resolution of the positron emission tomography (PET) scanner on the quantitative measurement of regional cerebral blood flow (rCBF) was investigated for various tracer kinetic models with use of 15O labeled water and PET. Using a numerical brain phantom consisting of a gray matter, white matter and cerebrospinal fluid components, dynamical tracer distribution images were calculated for the H215O bolus injection and for the C15O2 gas inhalation protocols. The tracer distribution images were convoluted with a 2 dimensional gaussian function with full-width at half maximum (FWHM) of 4, 7, 12 mm to simulate a limited spatial resolution of the PET scanner, and rCBF images were calculated according to some kinetic models. Smoothing the tracer distribution images caused a heterogeneous structure (tissue mixture) in a given volume element. rCBF values calculated by models with use of 15O-water and PET were found to provide rCBF values that were systematically underestimated compared with those obtained by the microsphere model for a mixed tissue region. Moreover, the magnitude of the underestimation was shown to be highly dependent on the tracer kinetic models employed, those errors for mixed tissue of gray and white matter were 20% on steady state, 9% on autoradiography and on weighted integration method, and 2% on non-linear least squares fitting, compared with microsphere model. More errors observed by steady state method and autoradiography method happened for tissue mixture consisting gray matter, white matter and cerebrospinal fluid components. It is important to take into account for difference of the partial volume effect for each models in calculated rCBF.

Regional cerebral blood flow, blood volume, oxygen extraction fraction, and oxygen utilization rate in normal volunteers measured by the autoradiographic technique and the single breath inhalation method

By means of a high resolution PET scanner, the regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rCMRO2) for major cerebral gyri and deep brain structures were studied in eleven normal volunteers during an eye-covered and ear-unplugged resting condition. Regional CBF was measured by the autoradiographic method after intravenous administration of H2(15)O. Regional OEF and rCMRO2 were measured by the single inhalation of 15O2. With MR T1-weighted images as an anatomical reference, thirteen major cerebral gyri, caudate nucleus, lentiform nucleus, thalamus, midbrain, pons, cerebellum and vermis were defined on the CMRO2 images. Values were read by using circular regions of interest 16 mm in diameter. The posterior part of the cingulate gyri had the highest rCBF and rCMRO2 values among brain structures, followed by the lentiform nucleus, the cerebellum, the caudate nucleus, and the thalamus. Parahippocampal gyri had the lowest rCBF and rCMRO2 values among the cortical gyri. Regional OEF for the pontine nuclei (0.34 +/- 0.04), the midbrain (0.35 +/- 0.05), the parahippocampal gyri (0.35 +/- 0.04 for the right and 0.37 +/- 0.05 for the left), and the thalami (0.37 +/- 0.05 for the right and 0.36 +/- 0.04 for the left) were significantly lower than the mean OEF for the cerebral cortices (0.42 +/- 0.04) (p < 0.05 or less). The global CBF and CMRO2 were consistent with those obtained by the Kety-Schmidt method.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of partial volume effect in quantitative measurement of regional cerebral blood flow in single photon emission computed tomography--effects of limited spatial resolution and first-pass extraction fraction]

Two numerical brain phantoms were generated in order to investigate errors which might be included in the quantitative measurement of regional CBF with use of single photon emission computed tomography (SPECT). The first phantom simulated the normal brain, and effects of the limited spatial resolution of the SPECT scanner were evaluated for 4 tracer kinetic models of the conventional microsphere model, the intra-carotid bolus injection technique of 133Xe, 133Xe Kanno-Lassen method, and the IMP-autoradiography (IMP-ARG) method. The second phantom simulated the diseased brain with middle-carotid artery (MCA) occlusion, and effects of the limited first-pass extraction fraction were investigated for the microsphere model with various permeability-surface area products. The limited spatial resolution caused systematic underestimation of the radioactivity concentration in the gray matter regions, and systematic overestimation in the low CBF regions. These errors in the original radioactivity distribution were found to cause further systematic errors in the calculated regional CBF images. It was also found that these errors were highly dependent on the tracer kinetic model employed, e.g., regional CBF values were overestimated in the clearance and the Kanno-Lassen methods compared with the conventional microsphere method, whereas values were underestimated in the IMP-ARG method. It was also shown in this study that the limited first-pass extraction fraction caused significant underestimation in the calculated rCBF values. In addition, regional contrast can be reduced when using a tracer with small PS product.(ABSTRACT TRUNCATED AT 250 WORDS)

Linearized method: A new approach for kinetic analysis of central dopamine D(2) receptor specific binding

We proposed a new method (;linearized method') to analyze neuroleptic ligand-receptor specific binding in a human brain using positron emission tomography (PET). We derived the linear equation to solve four rate constants, k(3), k(4), k(5), k(6) from PET data. This method does not demand a radioactivity curve in plasma as an input function to the brain, and can perform fast calculations in order to determine rate constants. We also tested the nonlinearized method including nonlinear equations which is a conventional analysis using plasma radioactivity corrected for ligand metabolites as an input function. We applied these methods to evaluate dopamine D(2) receptor specific binding of [(11)C] YM-09151-2. The value of B(max)/K(d)=k(3)/k (4) obtained by the linearized method was 5.72+/-3.1 which was consistent with the value of 5.78+/-3.4 obtained by the nonlinearized method.