Biomedical subjects

Tohru Shiga

Publications and source records attributed to Tohru Shiga.

At least 19 recordsLinked to original sources

PubMed2006

Left temporal perfusion associated with suspiciousness score on the Brief Psychiatric Rating Scale in schizophrenia.

We evaluated the relationship between regional cerebral blood flow (rCBF) and clinical symptoms in patients with schizophrenia. Single photon emission computed tomography with N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) was used to study 29 patients with schizophrenia. Clinical symptoms were assessed using the Brief Psychiatric Rating Scale (BPRS). We examined the correlation between rCBF and each BPRS item score using Statistical Parametric Mapping software. Corrected P-values < 0.05 were considered as statistically significant. The suspiciousness score on the BPRS was positively correlated with rCBF in the left inferior temporal gyrus. There was no significant correlation between rCBF and any other items of the BPRS. There was no significant correlation between rCBF and chlorpromazine-equivalent dosage. This analysis permits the quantitative assessment of the severity of persecutory delusions in relation to left temporal perfusion in patients with schizophrenia.

Adolescent↗

PubMed2006

Loss of neuronal integrity: a cause of hypometabolism in patients with traumatic brain injury without MRI abnormality in the chronic stage.

PURPOSE: Traumatic brain injury (TBI) causes brain dysfunction in many patients. However, some patients have severe brain dysfunction but display no abnormalities on magnetic resonance imaging (MRI). There have been some reports of hypometabolism even in such patients. The purpose of this study was to investigate the relationship between metabolic abnormality and loss of neuronal integrity in TBI patients with some symptoms but without MRI abnormalities. METHODS: The study population comprised ten patients with TBI and ten normal volunteers. All of the patients were examined at least 1 year after the injury. ( 15)O-labelled gas PET and [(11)C]flumazenil (FMZ) positron emission tomography (PET) were carried out. The cerebral metabolic rate of oxygen (CMRO(2)) and binding potential (BP) images of FMZ were calculated. Axial T2WI, T2*WI and FLAIR images were obtained. Coronal images were added in some cases. RESULTS: All of the patients had normal MRI findings, and all showed areas with abnormally low CMRO(2). Low uptake on BP images was observed in six patients (60%). No lesions that showed low uptake on BP images were without low CMRO(2). On the other hand, there were 14 lesions with low CMRO(2) but without BP abnormalities. CONCLUSION: These results indicate that there are metabolic abnormalities in TBI patients with some symptoms after brain injury but without abnormalities on MRI. Some of the hypometabolic lesions showed low BP, indicating a loss of neuronal integrity. Thus, FMZ PET may have potential to distinguish hypometabolism caused by neuronal loss from that caused by other factors.

Adult↗

PubMed2006

Brain activation during detrusor overactivity in patients with Parkinson's disease: a positron emission tomography study.

PURPOSE: Patients with Parkinson's disease often have urine storage symptoms, such as urinary urgency, frequency and incontinence, which are induced by detrusor overactivity. However, little is known of the mechanisms inducing detrusor overactivity in this disease. We have previously examined the human brain response to bladder filling in healthy male volunteers using positron emission tomography. We hypothesized that brain activation patterns in response to bladder filling would be different in patients with Parkinson's disease. MATERIALS AND METHODS: Nine male patients with Parkinson's disease were catheterized via the urethra for bladder filling and intravesical pressure monitoring. We performed positron emission tomography, consisting of tasks 1 and 2. For task 1 the bladder was maintained empty via the urethral catheter. For task 2 room temperature water was dripped for bladder filling until the onset of detrusor overactivity. Data acquisition for task 2 was done during detrusor overactivity. Data on each scan were summed on a computer and further analyzed using a statistical parametric mapping procedure. RESULTS: Significant brain activation during detrusor overactivity was found in the periaqueductal gray, supplementary motor area, cerebellar vermis, insula, putamen and thalamus. The most prominent activation was found in the cerebellum. The pons was not activated during detrusor overactivity. CONCLUSIONS: Alteration in brain activation sites in response to bladder filling may be related to the pathophysiology of detrusor overactivity in patients with Parkinson's disease.

Aged↗

PubMed2006

Smoking cessation normalizes coronary endothelial vasomotor response assessed with 15O-water and PET in healthy young smokers.

UNLABELLED: Cigarette smoking is one of the risk factors of cardiovascular diseases and is related to abnormal peripheral and coronary vascular vasomotion. Coronary vascular endothelial dysfunction is caused by chronic smoking in smokers without epicardial coronary artery stenosis. The coronary endothelial vasomotion abnormality is restored by interventions such as l-arginine or vitamin C infusion. However, to our knowledge, the effect of smoking cessation on coronary vasomotor response has not been elucidated. Therefore, the aim of this study was to assess the effect of smoking cessation on coronary vasomotor response by quantitative myocardial blood flow (MBF) measurement using (15)O-water and PET. METHODS: Fifteen young smokers (Brinkman index > 100; mean age +/- SD, 26 +/- 4 y) with no evidence of heart disease or cardiovascular risk factors, except for smoking, and age-matched nonsmokers (n = 12) were enrolled in this study. MBF was measured at rest, during the cold pressor test (CPT), before and at 1 and 6 mo after smoking cessation. In addition, MBF measurement during adenosine triphosphate (ATP) infusion was performed before and at 6 mo after smoking cessation. In nonsmokers, MBF was measured at rest, during ATP infusion, and during the CPT. RESULTS: MBF at rest and during ATP infusion did not differ between smokers and nonsmokers (0.73 +/- 0.12 vs. 0.80 +/- 0.15 mL/g/min and 3.15 +/- 1.43 vs. 3.69 +/- 0.76 mL/g/min, respectively; P = not significant). In contrast, MBF during the CPT in smokers was lower than that in nonsmokers (0.90 +/- 0.19 vs. 1.12 +/- 0.28 mL/g/min; P < 0.05). There was no significant difference in MBF either at rest or during ATP infusion between before and after smoking cessation, but MBF during the CPT increased at 1 mo in comparison with before cessation of smoking (0.90 +/- 0.19 vs. 1.02 +/- 0.22 mL/g/min; P < 0.01). An improvement of MBF response to the CPT was preserved at 6 mo after smoking cessation. CONCLUSION: Coronary vasomotor abnormality assessed by MBF response to the CPT was improved at 1 mo after smoking cessation. These findings indicate that coronary endothelial dysfunction may be reversible within 1 mo after smoking cessation in healthy young smokers.

Adult↗

PubMed2005

Cerebral oxygen metabolism and neuronal integrity in patients with impaired vasoreactivity attributable to occlusive carotid artery disease.

BACKGROUND AND PURPOSE: It is still unclear that impaired cerebrovascular reactivity (CVR) to acetazolamide is comparable to elevated oxygen extraction fraction (OEF) on positron emission tomography (PET) in patients with occlusive carotid diseases. Therefore, in this study, the authors aimed to clarify whether OEF is elevated in all patients with reduced cerebral blood flow (CBF) and CVR (type 3) on single photon emission computed tomography (SPECT), and, if not, to specify the underlying pathophysiology of type 3 but normal OEF. METHODS: This study included 46 patients who had decreased CBF and CVR on N-isopropyl-p-(123)I-iodoamphetamine SPECT in the ipsilateral middle cerebral artery area attributable to occlusive carotid diseases. Hemodynamic and metabolism parameters were determined in all patients by (15)O-gas PET, and neuronal integrity was evaluated in 19 patients using 11C-flumazenil (FMZ) PET. RESULTS: OEF was significantly elevated in 20 (43.5%) of 46 type 3 patients. Another 26 type 3 patients had normal OEF. Regression analysis showed that OEF significantly correlated with cerebral metabolic rate for oxygen and 11C-FMZ binding potential but not with other parameters. Subcortical infarction had no significant effect on OEF values. CONCLUSIONS: The results strongly suggest that type 3 patients with reduced CBF and CVR may be divided into 2 pathophysiologically different subgroups: misery perfusion attributable to hemodynamic compromise and matched hypometabolism attributable to incomplete infarction. Type 3 but normal OEF may represent a transition stage from misery perfusion to matched hypometabolism.

Aged↗

PubMed2005

Clinical analysis of cognitive function in diabetic patients by MMSE and SPECT.

We examined the frequency of cognitive impairment using the mini-mental-status examination (MMSE), as well as cerebral perfusion using single photon emission computed tomography (SPECT) in elderly diabetic patients. Written consent was obtained from all patients prior to their inclusion in this study. An MMSE score of 26 or less was adopted as an indication of cognitive impairment. Following an initial study, a 3-month study incorporating the use of MMSE and SPECT was performed in subjects, some of whom were taking donepezil hydrochloride. Of the 92 subjects enrolled in this study, 38% exhibited cognitive functional impairment and 18% earned MMSE scores of 23 or lower that were indicative of dementia. With regard to their cerebral blood flow pattern as determined by SPECT 217, 31.4 and 34.2% of subjects showed parieto-temporal hypoperfusion, asymmetrical hypoperfusion and fronto-temporal hypoperfusion patterns of abnormalities, respectively; 11.4% displayed unclassifiable findings and 8.5% showed no detectable abnormalities. No significant differences were seen in patients that were taking donepezil hydrochloride compared to those who were not. The incidence of cognitive functional impairment in elderly, diabetic patients was significantly elevated and was accompanied by a reduction in cerebral blood flow in the fronto-temporal region, as determined by SPECT.

Aged↗

PubMed2005

Quantitative analysis of myocardial glucose utilization in patients with left ventricular dysfunction by means of 18F-FDG dynamic positron tomography and three-compartment analysis.

PURPOSE: Myocardial glucose utilization (MGU) is altered in various heart diseases. The aim of this study was to quantitatively assess regional myocardial glucose utilization in patients with left ventricular (LV) dysfunction by dynamic( 18)F-fluorodeoxyglucose positron emission tomography (FDG PET). METHODS: A total of 18 subjects were studied, including ten with LV dysfunction (seven with idiopathic dilated cardiomyopathy and three with aortic regurgitation; NYHA II in 8 and III in 2) and eight healthy normal volunteers. Patients with diabetes mellitus were excluded. A dynamic PET study was performed for 40 min following the injection of 370 MBq of FDG after 50-g glucose loading. On the basis of a three-compartment model, MGU, K1, k2, and k3 were computed on a pixel by pixel basis to generate LV myocardial parametric maps. FDG standardized uptake value (SUV) was also calculated using static images obtained 40 min after FDG injection. These metabolic values were compared with myocardial flow distribution (%Flow), LVEF, LV volumes, and LV wall thickening (WT) determined by gated myocardial single-photon emission computed tomography using QGS software in eight myocardial segments. RESULTS: MGU correlated positively with LV volumes and negatively with LVEF. K(1) was significantly higher in the segments of the patients than in those of the normal volunteers (0.082+/-0.055 vs 0.041+/-0.017 ml min(-1) g(-1), p<0.05), although there was no difference in MGU between the groups. On the other hand, SUV, k2, and k3 did not differ significantly between the groups. Among the patients, the K1 values were significantly higher in the areas with impaired WT (%WT<17%) (0.109+/-0.063 vs 0.069+/-0.062 ml min(-1) g(-1), p<0.05) and in the areas with flow reduction (%Flow<71%) (0.112+/-0.076 vs 0.071+/-0.046 ml min(-1) g(-1), p<0.05). CONCLUSION: These results indicate that glucose utilization was preserved in the patients with LV dysfunction, mainly due to an increase in glucose transport, particularly in the regions with severely impaired LV function. Thus, the quantitative assessment of myocardial glucose utilization by FDG dynamic PET may provide useful information for assessing the regional myocardial metabolic status in patients with LV dysfunction.

Aged↗

PubMed2005

Evaluating performance of a pixel array semiconductor SPECT system for small animal imaging.

OBJECTIVES: Small animal imaging has recently been focused on basic nuclear medicine. We have designed and built a small animal SPECT imaging system using a semiconductor camera and a newly designed collimator. We assess the performance of this system for small object imaging. METHODS: We employed an MGC 1500 (Acrorad Co.) camera including a CdTe semiconductor. The pixel size was 1.4 mm/pixel. We designed and produced a parallel-hole collimator with 20-mm hole length. Our SPECT system consisted of a semiconductor camera with the subject holder set on an electric rotating stage controlled by a computer. We compared this system with a conventional small animal SPECT system comprising a SPECT-2000H scanner with four Anger type cameras and pinhole collimators. The count rate linearity for estimation of the scatter was evaluated for a pie-chart phantom containing different concentrations of 99mTc. We measured the FWHM of the 99mTc SPECT line source along with scatter. The system volume sensitivity was examined using a flood source phantom which was 35 mm long with a 32-mm inside diameter. Additionally, an in vivo myocardial perfusion SPECT study was performed with a rat. RESULTS: With regards to energy resolution, the semiconductor camera (5.6%) was superior to the conventional Anger type camera (9.8%). In the count rate linearity evaluation, the regression lines of the SPECT values were y = 0.019x + 0.031 (r2 = 0.999) for our system and y = 0.018x + 0.060 (r2 = 0.997) for the conventional system. Thus, the scatter count using the semiconductor camera was less than that using the conventional camera. FWHMs of our system and the conventional system were 2.9 +/- 0.1 and 2.0 +/- 0.1 mm, respectively. Moreover, the system volume sensitivity of our system [0.51 kcps/(MBq/ ml)/cm] was superior to that of the conventional system [0.44 kcps/(MBq/ml)/cm]. Our system provided clear images of the rat myocardium, sufficient for practical use in small animal imaging. CONCLUSIONS: Our SPECT system, utilizing a semiconductor camera, permits high quantitative analysis by virtue of its low scatter radiation and high sensitivity. Therefore, this system may contribute to molecular imaging of small animals and basic medical research.

Animals↗

PubMed2004

Use of a standardized uptake value for parametric in vivo imaging of benzodiazepine receptor distribution on [11C]flumazenil brain PET.

To simplify the acquisition protocol of carbon-11 labeled flumazenil (FMZ) positron emission tomography (PET) for distribution volume (DV) images, we attempted to obtain standardized uptake value (SUV) images compatible with DV images, and assessed the applicability of this method in patients with unilateral cerebrovascular diseases (CVD). [(11)C]FMZ PET was performed in ten normal subjects. A DV image and ten sequential 5-min SUV images were generated for each subject. We investigated the correlation coefficient (r) and standard estimation of error (SEE) between the latter ten static images and the DV image using the pixel-by-pixel method, thereby determining the optimum acquisition phase. The same FMZ PET procedure was performed in 15 patients with unilateral CVD. Twenty regions of interest (ROIs) were positioned both in lesioned areas and in symmetrical regions. DV and SUV in the optimum phase for each ROI were calculated to compare the lesion-to-normal (L/N) ratio of DV and that of SUV. The highest r and a low SEE (r=0.957, SEE=633) were observed from 30 to 35 min after tracer administration in the study of normal subjects. A high r (0.945) and a low SEE (0.0438) between the DV L/N ratio and the SUV L/N ratio were obtained in the study of patients. Our study suggests that SUV images acquired from 30 to 35 min after FMZ administration are a suitable alternative to DV images not only in normal subjects but also in patients with unilateral CVD. This simple method seems to be valuable for the identification of altered neuronal activity in patients with CVD.

Adult↗

PubMed2004

Pretreatment and posttreatment evaluation of hemodynamic and metabolic parameters in intracranial dural arteriovenous fistulae with cortical venous reflux.

OBJECTIVE: Retrograde drainage into the cortical veins results in poor outcome in patients with an intracranial dural arteriovenous fistula. However, the pathophysiological features of dural arteriovenous fistulae remain obscure. This study aimed to clarify hemodynamic and metabolic conditions in these patients using positron emission tomography. METHODS: This study included eight patients with an intracranial dural arteriovenous fistula. All patients had cortical venous reflux, as demonstrated by angiography. Regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), regional cerebral metabolic rate for oxygen, and regional oxygen extraction fraction (rOEF) were measured before and after surgical or endovascular treatment using positron emission tomography. RESULTS: Pretreatment positron emission tomographic studies revealed that all patients had abnormal hemodynamic and metabolic parameters in the area that was drained by the involved cortical veins. A severe increase in rCBV was noted in seven of the eight patients. A significant decrease in rCBF also was observed in all eight patients. A negative correlation was observed between rCBF and rCBV. Three patients had an elevated rOEF. Oxygen metabolism was impaired in seven patients. All patients underwent successful treatment. Follow-up studies demonstrated significant improvements in rCBF, rCBV, and regional cerebral metabolic rate for oxygen. The improvement in regional cerebral metabolic rate for oxygen varied among the patients. Normalization of rOEF also was confirmed in three patients who had increased rOEF before the treatment. CONCLUSION: The present results suggest that hemodynamic and metabolic characteristics vary widely among patients with cortical venous reflux. It is essential to precisely evaluate hemodynamic and metabolic conditions to predict their outcomes and therapeutic effects.

Adult↗

PubMed2004

Reduced blood flow and preserved vasoreactivity characterize oxygen hypometabolism due to incomplete infarction in occlusive carotid artery diseases.

UNLABELLED: Recent studies have clarified that hemodynamically compromised patients are at high risk for subsequent stroke. The acetazolamide test is widely used to detect the patients with hemodynamic compromise due to occlusive carotid artery disease. Previous studies have suggested that patients with impaired reactivity to acetazolamide had an increased oxygen extraction fraction (OEF) on PET. However, the underlying pathophysiology has not been defined in patients with reduced blood flow and preserved reactivity to acetazolamide due to carotid occlusive diseases regardless of a normal appearance on MRI. This study aimed to clarify hemodynamic and metabolic parameters in such patients, using (15)O gas and (11)C-flumazenil (FMZ) PET. METHODS: Our study included 15 patients who had reduced cerebral blood flow (CBF) and preserved cerebrovascular reactivity (CVR) to acetazolamide in the ipsilateral middle cerebral artery territory due to occlusive carotid diseases on N-isopropyl-p-(123)I-iodoamphetamine ((123)I-IMP) SPECT. We determined the CBF, cerebral metabolic rate for oxygen (CMRO(2)), cerebral blood volume (CBV), and OEF using (15)O gas PET. The binding potential for (11)C-FMZ was also measured in 5 patients. All patients were medically treated and followed-up during a mean period of 2.7 y. RESULTS: (15)O gas PET scans revealed that the ipsilateral CBF and CMRO(2) were reduced to 80% +/- 11% (P < 0.0001) and 78% +/- 8% (P < 0.0001) of the contralateral side, respectively. However, there was no significant side-to-side difference in the CBV and OEF. The ipsilateral binding potential for (11)C-FMZ was also significantly reduced to 82% +/- 2% of the contralateral side (P < 0.05), being very similar to the asymmetry of the CBF and CMRO(2). No patients suffered further ischemic stroke in the ipsilateral hemisphere during the follow-up period. CONCLUSION: Our results strongly suggest that a reduced CBF and a normal CVR characterize oxygen hypometabolism probably due to ischemia-related neuronal loss-namely, incomplete infarction. Such an ischemic lesion is not hemodynamically compromised and is at very low risk for a subsequent ischemic stroke even if the patient is medically treated.

Acetazolamide↗

PubMed2004

Improvement of algorithm for quantification of regional myocardial blood flow using 15O-water with PET.

UNLABELLED: (15)O-Water and dynamic PET allow noninvasive quantification of myocardial blood flow (MBF). However, complicated image analyzing procedures are required, which may limit the practicality of this approach. We have designed a new practical algorithm, which allows stable, rapid, and automated quantification of regional MBF (rMBF) using (15)O-water PET. We designed an algorithm for setting the 3-dimensional (3D) region of interest (ROI) of the whole myocardium semiautomatically. Subsequently, a uniform input function was calculated for each subject using a time-activity curve in the 3D whole myocardial ROI. The uniform input function allows the mathematically simple and robust algorithm to estimate rMBF. METHODS: Thirty-six volunteers were used in the static (15)O-CO and dynamic (15)O-water PET studies. To evaluate the reproducibility of the estimates, a repeated (15)O-water scan was obtained under resting condition. In addition, to evaluate the stability of the new algorithm in the hyperemic state, a (15)O-water scan was obtained with adenosine triphosphate. This algorithm includes a procedure for positioning a 3D ROI of the whole myocardium from 3D images and dividing it into 16 segments. Subsequently, the uniform input function was calculated using time-activity curves in the whole myocardial ROI and in the LV ROI. The uniform input function allowed this simple and robust algorithm to estimate the rMBF, perfusable tissue fraction (PTF), and spillover fraction (Va) according to a single tissue compartment model. These estimates were compared with those calculated using the original method. A simulation study was performed to compare the effects of errors in PTF or Va on the MBF using the 2 methods. RESULTS: The average operating time for positioning a whole myocardial ROI and 16 regional myocardial ROIs was <5 min. The new method yielded less deviation in rMBF (0.876 +/- 0.177 mL/min/g, coefficient of variation [CV] = 20.2%, n = 576) than those with the traditional method (0.898 +/- 0.271 mL/min/g, CV = 30.1%, n = 576) (P < 0.01). In the hyperemic state, the new method yielded less deviation in rMBF (3.890 +/- 1.250 mL/min/g, CV = 32.1%) than those with the traditional method (3.962 +/- 1.762 mL/min/g, CV = 44.4%) (P < 0.05). This method yielded significantly higher reproducibility of rMBF (r = 0.806, n = 576) than the original method (r = 0.756, n = 576) (P < 0.05). Our new method yielded a better correlation in the repeated measurement values of rMBF and less variability among the regions in the myocardium than with the original theory of the (15)O-water technique. The simulation study demonstrated fewer effects of error in the PTF or Va on the MBF value with the new method. CONCLUSION: We have developed a technique for an automated, simplified, and stable algorithm to quantify rMBF. This software is considered to be practical for clinical use in myocardial PET studies using (15)O-water with a high reproducibility and a short processing time.

Algorithms↗

PubMed2003

Characterisation of [123I]iomazenil distribution in a rat model of focal cerebral ischaemia in relation to histopathological findings.

Iodine-123 labelled iomazenil ([(123)I]IMZ) has been reported to be a useful marker of neuronal viability. The brain distribution of [(123)I]IMZ, however, has not been correlated with the pathophysiological response in detail after an ischaemic insult. To characterise [(123)I]IMZ as a marker of neuronal viability, we compared its brain distribution with cyclooxygenase-2 (COX-2) expression, DNA fragmentation and cellular integrity. [(123)I]IMZ and [(125)I]IMP were injected into rats with focal cerebral ischaemia for the purpose of dual-tracer autoradiography. COX-2 and microtubule-associated protein-2 (MAP-2, a marker of cellular integrity) were immunostained. In situ DNA polymerase-I-dependent dUTP incorporation into damaged DNA was used as an indicator of DNA fragmentation. Lesion to normal ratios (LNRs) for [(123)I]IMP and [(125)I]IMZ were calculated. [(123)I]IMZ accumulation was preserved in several regions with impaired [(123)I]IMP accumulation. COX-2 expression was occasionally observed, whereas neither DNA fragmentation nor MAP-2 denaturation was detected in these regions. DNA fragmentation and impaired MAP-2 immunostaining were observed only in the regions with reduced LNRs for both tracers. The LNR for [(123)I]IMZ was significantly lower in regions with impaired MAP-2 immunostaining (0.120+/-0.152, P<0.0001), in regions positive for dUTP incorporation (0.488+/-0.166, P<0.0001) and in regions positive for COX-2 expression (0.626+/-0.186, P<0.001) than in histologically normal regions (0.784+/-0.213). Thus, neuronal DNA is still intact and cellular integrity is maintained in the ischaemic regions with preserved [(123)I]IMZ accumulation. The impairment of [(123)I]IMZ accumulation precedes DNA fragmentation and denaturation of cellular integrity. These results provide the molecular basis of [(123)I]IMZ distribution.

Animals↗

PubMed2003

Quantitative cerebral blood flow measurement with dynamic perfusion CT using the vascular-pixel elimination method: comparison with H2(15)O positron emission tomography.

BACKGROUND AND PURPOSE: Blood vessels are usually conspicuous on dynamic CT perfusion images. The presence of large vessels may lead to overestimation of the quantitative value of cerebral blood flow (CBF). We evaluated the efficacy of the vascular-pixel elimination (VPE) method in quantitative CT perfusion imaging, in comparison with positron emission tomography (PET). METHODS: Five healthy volunteers underwent CT perfusion and PET studies. A four-channel multi-detector row CT scanner was used. Dynamic cine scanning was performed after bolus injection of an intravenous contrast agent. CT-CBF was calculated by the central volume principle and deconvolution method. PET was performed after infusion of (15)O-labeled water. PET-CBF was calculated by using a nonlinear least squares method. Average CBF values of the whole section, gray matter, and white matter with both CT and PET were compared after image registration. The comparison was performed with and without VPE. In the VPE method, the vascular pixels were defined by the cerebral blood volume value of the pixel. The threshold of VPE was changed from 5 to 20 mL/100 g. Pixel-by-pixel correlation between CT-CBF and PET-CBF and linear regression analysis were also performed. RESULTS: Without VPE, CT-CBF was overestimated in all subjects. As the VPE threshold decreased, CT-CBF decreased and the correlation coefficient increased. The best correlation was observed at a VPE threshold of 8 mL/100 g in four of the five subjects. Average CT-CBF values, without VPE, of the whole section, gray matter, and white matter were 59.01, 66.73, and 42.53 mL/100 g/min, respectively. With VPE (threshold, 8 mL/100 g), average CT-CBF values of the whole section, gray matter, and white matter were 45.56, 52.75, and 30.38, respectively. The corresponding PET-CBF values were 46.86, 50.89, and 38.20 mL/100 g/min, respectively. CONCLUSION: Vascular pixels should be excluded from the calculation of CT-CBF to avoid overestimation of the CBF values. If vascular pixels are excluded, CBF calculation with CT perfusion imaging is considerably accurate.

Adult↗

PubMed2003

[Combined imaging of epileptic foci and brain metabolism using MEG and FDG-PET].

A 17-year-old woman developed left hemiparesis at the age 6 months. She had suffered from focal motor seizures associated with tonic extension of her left extremities since the age of 10 years. The interictal scalp EEG demonstrated frequent spike-and-slow-wave complexes dominantly in the right frontal area. MRI showed an old cerebral infarction in the right frontal lobe. Simultaneous recordings of magnetoencephalography (MEG) and EEG were obtained by using a 204-channel whole-head MEG system. Equivalent current dipoles (ECDs) calculated from epileptic spikes on MEG were scattered in the cortex adjacent to the lesion in the right frontal lobe. Positron emission tomography with 18-fluoro-2-deoxyglucose (FDG-PET) in the interictal state showed hypometabolism in the lesion and its adjacent area. The super-imposed images of the dipole and PET showed that epileptic foci surrounded the lesion. The multimodality imaging is useful for evaluation of patients with epilepsy for possible indication of surgery.

Adolescent↗

PubMed2003

High uptake on 11C-methionine positron emission tomographic scan of basal ganglia germinoma with cerebral hemiatrophy.

We herein describe a 12-year-old male patient with a germinoma of the basal ganglia who presented with progressive hemiparesis. MR imaging showed ipsilateral cerebral hemiatrophy predominantly in the left basal ganglia, whereas no mass or enhancement was depicted. Single photon emission CT revealed no significant uptake of thallium, whereas (11)C-methionine positron emission tomography showed clearly discernible uptake in the left putamen. Stereotactic biopsy, referencing the results of (11)C-methionine positron emission tomography, was performed, allowing histologic verification of germinoma to be established. (11)C-methionine positron emission tomography was the only technique that indicated the precise localization of the tumor in our patient and enabled biopsy-based final diagnosis of the basal ganglia germinoma without any overt mass formation.

Atrophy↗

PubMed2003

[Normalization of cerebral hemodynamics and metabolism after carotid stenting in patients unfit for major surgery].

There is increasing evidence that stenting is a useful strategy for internal carotid artery (ICA) stenosis in patients unfit for drastic surgery. However, it should be remembered that perioperative complications including seizure or intracerebral hemorrhage due to hyperperfusion are not so rare. The authors describe a case with severe ICA stenosis, who successfully underwent stenting as a result of intensive medical care for postoperative hyperperfusion. A 77-year-old man with a recent history of angina pectoris and transient ischemic attack was referred to our hospital. Cerebral angiography showed subtotal occlusion of the left ICA. SPECT/PET studies revealed a disturbed reactivity to acetazolamide and an increase in regional oxygen extraction fraction in the left hemisphere, suggesting a marked reduction in cerebral perfusion pressure. He successfully underwent carotid stenting. Intraoperative near-infrared monitoring showed an increase in the concentration of total and oxidized hemoglobin in the left frontal area after stenting. A SPECT study just after stenting also demonstrated hyperperfusion in the left middle cerebral artery territory. His blood pressure was carefully controlled to avoid "hyperperfusion syndrome" including headache, seizure and intracerebral hemorrhage. Follow-up SPECT/PET studies showed a normalization of hemodynamic and metabolic parameters. SPECT/PET studies are quite valuable to predict and prevent hyperperfusion syndrome after carotid stenting, and result in good clinical outcome.

Aged↗

PubMed2002

Accumulation of [11C]acetate in normal prostate and benign prostatic hyperplasia: comparison with prostate cancer.

Carbon-11 acetate positron emission tomography (PET) has been reported to be of clinical value for the diagnosis of prostate cancer. However, no detailed analysis has yet been carried out on the physiological accumulation of [(11)C]acetate in the prostate. The purpose of this study was to elucidate the physiological accumulation of [(11)C]acetate in the prostate using dynamic PET. The study included 30 subjects without prostate cancer [21 with normal prostate and nine with benign prostatic hyperplasia (BPH)] and six patients with prostate cancer. A dynamic PET study was performed for 20 min after intravenous administration of 555 MBq of [(11)C]acetate. The standardised uptake value (SUV) at 16-20 min post tracer administration and the early-to-late-activity ratio of the SUV (E/L ratio), which was determined by dividing the SUV(6-10 min) by the SUV(16-20min), were calculated to evaluate the accumulation of [(11)C]acetate. The prostate was clearly visualised and distinguished from adjacent organs in PET images in most of the cases. The SUV of the prostate (2.6+/-0.8) was significantly higher than that of the rectum (1.7+/-0.4) or bone marrow (1.3+/-0.3) ( P<0.0001 in each case). The SUV of the normal prostate of subjects aged <50 years (3.4+/-0.7) was significantly higher than both the SUV for the normal prostate of subjects aged > or =50 years (2.3+/-0.7) and that of subjects with BPH (2.1+/-0.6) ( P<0.01 in each case). The primary prostate cancer in six cases was visualised by [(11)C]acetate PET. However, the difference in the SUV between subjects aged > or =50 with normal prostate or with BPH and the patients with prostate cancer (1.9+/-0.6) was not statistically significant. There was also no significant difference in the E/L ratio between subjects aged > or =50 with normal prostate (0.98+/-0.04) or BPH (0.96+/-0.08) and patients with prostate cancer (1.02+/-0.12). In conclusion, a normal prostate exhibits age-related physiological accumulation of [(11)C]acetate. Careful interpretation of [(11)C]acetate PET images of prostate cancer is necessary because the SUV and the E/L ratio for the normal prostate and for BPH overlap significantly with those for prostate cancer.

Acetates↗