H Toyama

Publications (37)78.26 Total impact

• Article: Comparison of parametric FBP and OS-EM reconstruction algorithm images for PET dynamic study.

  K Oda, H Toyama, K Uemura, Y Ikoma, Y Kimura, M Senda
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  ABSTRACT: An ordered subsets expectation maximization (OS-EM) algorithm is used for image reconstruction to suppress image noise and to make non-negative value images. We have applied OS-EM to a digital brain phantom and to human brain 18F-FDG PET kinetic studies to generate parametric images. A 45 min dynamic scan was performed starting injection of FDG with a 2D PET scanner. The images were reconstructed with OS-EM (6 iterations, 16 subsets) and with filtered backprojection (FBP), and K1, k2 and k3 images were created by the Marquardt non-linear least squares method based on the 3-parameter kinetic model. Although the OS-EM activity images correlated fairly well with those obtained by FBP, the pixel correlations were poor for the k2 and k3 parametric images, but the plots were scattered along the line of identity and the mean values for K1, k2 and k3 obtained by OS-EM were almost equal to those by FBP. The kinetic fitting error for OS-EM was no smaller than that for FBP. The results suggest that OS-EM is not necessarily superior to FBP for creating parametric images.
  Annals of Nuclear Medicine 11/2001; 15(5):417-23. · 1.50 Impact Factor
• Source

  Available from: Anne G De Volder

  Article: Auditory triggered mental imagery of shape involves visual association areas in early blind humans.

  A G De Volder, H Toyama, Y Kimura, M Kiyosawa, H Nakano, A Vanlierde, M C Wanet-Defalque, M Mishina, K Oda, K Ishiwata, M Senda
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  ABSTRACT: Previous neuroimaging studies identified a large network of cortical areas involved in visual imagery in the human brain, which includes occipitotemporal and visual associative areas. Here we test whether the same processes can be elicited by tactile and auditory experiences in subjects who became blind early in life. Using positron emission tomography, regional cerebral blood flow was assessed in six right-handed early blind and six age-matched control volunteers during three conditions: resting state, passive listening to noise sounds, and mental imagery task (imagery of object shape) triggered by the sound of familiar objects. Activation foci were found in occipitotemporal and visual association areas, particularly in the left fusiform gyrus (Brodmann areas 19-37), during mental imagery of shape by both groups. Since shape imagery by early blind subjects does involve similar visual structures as controls at an adult age, it indicates their developmental crossmodal reorganization to allow perceptual representation in the absence of vision.
  NeuroImage 08/2001; 14(1 Pt 1):129-39. · 5.89 Impact Factor
• Article: [Quantitative estimation of brain atrophy and function with PET and MRI two-dimensional projection images].

  R Saito, H Toyama, K Uemura, K Ishii, M Senda, A Uchiyama
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  ABSTRACT: The purpose of this paper is to estimate the extent of atrophy and the decline in brain function objectively and quantitatively. Two-dimensional (2D) projection images of three-dimensional (3D) transaxial images of positron emission tomography (PET) and magnetic resonance imaging (MRI) were made by means of the Mollweide method which keeps the area of the brain surface. A correlation image was generated between 2D projection images of MRI and cerebral blood flow (CBF) or 18F-fluorodeoxyglucose (FDG) PET images and the sulcus was extracted from the correlation image clustered by K-means method. Furthermore, the extent of atrophy was evaluated from the extracted sulcus on 2D-projection MRI and the cerebral cortical function such as blood flow or glucose metabolic rate was assessed in the cortex excluding sulcus on 2D-projection PET image, and then the relationship between the cerebral atrophy and function was evaluated. This method was applied to the two groups, the young and the aged normal subjects, and the relationship between the age and the rate of atrophy or the cerebral blood flow was investigated. This method was also applied to FDG-PET and MRI studies in the normal controls and in patients with corticobasal degeneration. The mean rate of atrophy in the aged group was found to be higher than that in the young. The mean value and the variance of the cerebral blood flow for the young are greater than those of the aged. The sulci were similarly extracted using either CBF or FDG PET images. The purposed method using 2-D projection images of MRI and PET is clinically useful for quantitative assessment of atrophic change and functional disorder of cerebral cortex.
  Kaku igaku. The Japanese journal of nuclear medicine 06/2001; 38(3):201-9.
• Conference Proceeding: Evaluation of the reliability in kinetic analysis for dual tracer injection of FDG and flumazenil PET study

  Y. Ikoma, H. Toyama, K. Uemura, A. Uchiyama
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  ABSTRACT: The kinetic analysis for dual tracer injection with 2-input compartment model is challenging in order to assess the two different functions In the same time and same situation. In this study, we investigated the possibility of kinetic analysis with two tracers, ¹⁸F-FDG and ¹¹C-flumazenil (FMZ), by means of the computer simulation. The reliability of estimated parameters was Investigated for various injection protocols and noise levels. Simulated decaying tissue time activity curves were generated for various injection protocols with input function of FDG and FMZ and true k-values by using the 2-input 3-tissue compartment 5-parameter model, i.e. 2-tissue compartment 3-parameter for FDG and 1-tissue compartment 2-parameter for FMZ. The injection Interval of two tracers was changed from 0 to 20 minutes. The noise was generated depending on the total collected count and added each decaying tissue time activity curve. The rate constants for FDG and FMZ were estimated by nonlinear least square method. The reliability of parameter estimates was evaluated by mean absolute difference between true and estimated value of one thousand runs for each injection protocol and noise level. As a result, it was found that parameters were estimated most reliably when FDG was injected 15 minutes later than FMZ injection. In 5% last frame noise, the mean absolute difference between true and estimated value of Ki, reflecting the uptake of FDG, was about 8%, that of DV, distribution volume of FMZ, was 7%. The reliability was independent on the ratio of administration dose of FDG to that of FMZ. In the simulation study, the possibility of kinetic analysis for dual tracer injection was shown
  Nuclear Science Symposium Conference Record, 2001 IEEE; 02/2001
• Article: Application of PET-MRI registration techniques to cat brain imaging.

  Y Shimada, K Uemura, B A Ardekani, T Nagaoka, K Ishiwata, H Toyama, K Ono, M Senda
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  ABSTRACT: In positron emission tomography (PET) studies of diseased animals, it is very useful to have accurate anatomical information as a reference. In human studies, anatomical information is usually obtained from magnetic resonance imaging (MRI) of the subject with retrospective registration of the subject's PET image to the MRI. A number of PET-MRI registration techniques are used for this purpose. However, the utility of these methods has not been tested for animals image registration. This paper studies the feasibility of applying two currently used human brain PET-MRI registration techniques to cat brain images. Three cats were anesthetized with isoflurane gas, and PET images were acquired with H(2)(15)O, benzodiazepine receptor ligand 11C-flumazemil (FMZ), dopamine receptor ligand 11C-nemonapride (NEM) and fluorodeoxy glucose (18F-FDG). The four PET scans were acquired consecutively within the same day while the cat remained fixed in the scanner. We also obtained T1-weighted and T2-weighted MRI of the cats in a 4.7 T unit. The PET images were registered to MRI using two human brain registration techniques: a semi-automatic method (SAM), which is a two-step method based on the extraction of the midsagittal plane, and an automatic method (AMIR) method that minimizes PET pixel variance within spatially connected segments determined by MRI. T2-weighted MRI provided better structural information than T1 MRI. FMZ did, while FDG or H(2)O PET images did not, provide a structural outline of the brain. The FMZ PET image was registered to MRI satisfactorily using SAM. The striatum visualized in nemonapride PET image re-sliced with the same parameters matched the striatum identified in T2-weighted MRI. Registration by AMIR was successful by inspection for FMZ, FDG or H(2)O PET images in only one of the three cats. The registration error of SAM was estimated to be less than 2 mm or 2 degrees. A satisfactory registration of FMZ-PET to T2-weighted MRI of the cat brain was obtained by a two-step manual registration technique. This will enhance the usefulness of PET in the field of cerebral pathophysiology.
  Journal of Neuroscience Methods 09/2000; 101(1):1-7. · 1.98 Impact Factor
• Article: Intrasubject correlation between static scan and distribution volume images for [11C]flumazenil PET.

  M Mishina, M Senda, Y Kimura, H Toyama, K Ishiwata, M Ohyama, T Nariai, K Ishii, K Oda, T Sasaki, S Kitamura, Y Katayama
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  ABSTRACT: Accumulation of [11C]flumazenil (FMZ) reflects central nervous system benzodiazepine receptor (BZR). We searched for the optimal time for a static PET scan with FMZ as semi-quantitative imaging of BZR distribution. In 10 normal subjects, a dynamic series of decay-corrected PET scans was performed for 60 minutes, and the arterial blood was sampled during the scan to measure radioactivity and labeled metabolites. We generated 13 kinds of "static scan" images from the dynamic scan in each subject, and analyzed the pixel correlation for these images versus distribution volume (DV) images. We also analyzed the time for the [11C]FMZ in plasma and tissue to reach the equilibrium. The intra-subject pixel correlation demonstrated that the "static scan" images for the period centering around 30 minutes post-injection had the strongest linear correlation with the DV image. The ratio of radioactivity in the cortex to that in the plasma reached a peak at 40 minutes after injection. Considering the physical decay and patient burden, we conclude that the decay corrected static scan for [11C]FMZ PET as semi-quantitative imaging of BZR distribution is to be optimally acquired from 20 to 40 minutes after injection.
  Annals of Nuclear Medicine 07/2000; 14(3):193-8. · 1.50 Impact Factor
• Article: A PET study of adenosine A1 receptor in anesthetized monkey brain.

  S Wakabayashi, T Nariai, K Ishiwata, T Nagaoka, K Hirakawa, K Oda, Y Sakiyama, S Shumiya, H Toyama, F Suzuki, M Senda
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  ABSTRACT: We demonstrated the distribution of adenosine A1 receptors in the anesthetized monkey brain with positron emission tomography (PET) using [(11)C]KF15372 ([1-propyl-(11)C]8-dicyclopropylmethyl-1, 3-dipropylxanthine). [(11)C]KF15372 was injected intravenously. The regional standardized uptake values and the distribution volume were calculated. We also investigated the effect of carrier on the uptake and regional brain distribution of [(11)C]KF15372. The use of [(11)C]KF15372 with dynamic PET scanning could be an appropriate method to analyze the regional binding potential of adenosine A1 receptors in living brain.
  Nuclear Medicine and Biology 06/2000; 27(4):401-6. · 3.02 Impact Factor
• Article: A PET-MRI registration technique for PET studies of the rat brain.

  N Hayakawa, K Uemura, K Ishiwata, Y Shimada, N Ogi, T Nagaoka, H Toyama, K Oda, A Tanaka, K Endo, M Senda
  Nuclear Medicine and Biology 03/2000; 27(2):121-5. · 3.02 Impact Factor
• Article: Benzodiazepine receptor distribution and cerebral blood flow in early blindness--a PET study.

  M Mishina, M Senda, M Kiyosawa, A De Volder, H Toyama, K Ishiwata, K Oda, Y Kimura, H Nakano, M Ohyama, S Kitamura, Y Katayama
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  ABSTRACT: We studied benzodiazepine receptor (BZR) distribution, which is thought to be affected by neuronal density in the cerebral cortex, and CBF using [11C]flumazenil and [15O]water PET in early blind (EB) and in blindfold sighted control (SC) subjects. PET images were co-registered to the subject's MRI. Using SPM96, MRI images were normalized in the Talairach and Tournoux coordinate system, and accordingly MRI-registered PET images were spatially normalized. Statistical parametric maps were computed on a voxel-by-voxel basis, using the general linear model. CBF for EB was significantly larger in the Brodmann area 17 and 18, especially anterior area, than that for SC, while there was no significant difference in BZR distribution. Our BZR data suggest that the amount of neurons do not change due to early visual deprivation in the visual cortex, in spite of high CBF in visual cortex of EB subjects.
  The Keio Journal of Medicine 03/2000; 49 Suppl 1:A114-6.
• Source

  Available from: Masahiro Mishina

  Article: Preserved benzodiazepine receptors in Alzheimer's disease measured with C-11 flumazenil PET and I-123 iomazenil SPECT in comparison with CBF.

  M Ohyama, M Senda, K Ishiwata, S Kitamura, M Mishina, K Ishii, H Toyama, K Oda, Y Katayama
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  ABSTRACT: This study evaluates the regional cerebral blood flow (CBF) with H2(15)O-PET and the distribution of central benzodiazepine receptor (BZR) with C-11 flumazenil (FMZ) by PET and I-123 iomazenil (IMZ) by SPECT in Alzheimer's disease (AD). In AD, whereas the CBF was diminished in the frontal, temporal, parietal, and occipital cortex, the distribution volume of FMZ and delayed activity of IMZ were relatively preserved in these cortices, suggesting that the BZR reduction, reflecting neuronal loss, is less prominent than the CBF suppression. The mini-mental state examination score (MMS) was weakly correlated with the CBF in the parietal cortex but not with BZR. It is speculated that the neuronal density reflected by BZR is less impaired than the neuronal function assessed with blood flow in the association cortex of AD. High correlation was found between the uptake of FMZ and the delayed activity of IMZ. The delayed image of IMZ-SPECT is clinically useful to evaluate the preservation of neuronal density in the affected temoporoparietal association cortex in AD.
  Annals of Nuclear Medicine 11/1999; 13(5):309-15. · 1.50 Impact Factor
• Source

  Available from: jsnm.org

  Article: Comparison of three PET dopamine D2-like receptor ligands, [11C]raclopride, [11C]nemonapride and [11C]N-methylspiperone, in rats.

  K Ishiwata, N Hayakawa, N Ogi, K Oda, H Toyama, K Endo, A Tanaka, M Senda
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  ABSTRACT: We studied the tracer kinetics of three dopamine D2-like receptor ligands, [11C]raclopride ([11C]RAC), [11C]nemonapride ([11C]NEM) and [11C]N-methylspiperone ([11C]MSP), in anesthetized rats by tissue dissection, ex vivo ARG and PET in order to clarify their characteristics for PET imaging. The in vivo affinity of the three ligands for the striatum ([11C]MSP > [11C]NEM > [11C]RAC) obeyed the in vitro affinity for dopamine D2 receptors. The affinity of [11C]RAC and [11C]MSP for the cerebellum was very low, but the affinity of [11C]NEM for the cerebellum was compatible to that for the cortex and was not to be ignored. Also the affinity of [11C]MSP for the cortex was relatively high. [11C]RAC showed the highest selectivity. The striatal PET image with [11C]RAC was clearer than that with [11C]NEM or [11C]MSP, but the activity decreased much faster than that measured by tissue dissection because of the partial volume effect. The striatal activity with [11C]NEM remained high and that with [11C]MSP gradually increased. [11C]RAC and [11C]MSP, but not [11C]NEM, showed a high accumulation in the periorbital region.
  Annals of Nuclear Medicine 07/1999; 13(3):161-7. · 1.50 Impact Factor
• Conference Proceeding: Effect of reconstruction algorithm on parametric images in PET dynamic study: comparison between FBP and OS-EM

  K. Oda, H. Toyama, K. Uemura, Y. Ikoma, Y. Kimura, M. Senda
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  ABSTRACT: Ordered subset expectation maximization (Os-FM) algorithm is used for image reconstruction to suppress image noise and to make non-negative value images. The authors have applied OS-EM to a digital phantom and to an ¹⁸F-FDG PET kinetic study to generate parametric images. A 45 min dynamic scan was performed starting injection of 86-223 MBq of FDG using a 2D PET scanner. The images were reconstructed with OS-EM (6 iterations, 16 subsets) and with filtered backprojection (FBP), and K1, k2 and k3 images were created with Marquardt method. The activity images by Os-FM correlated fairly well with those by FBP. Although the mean values of K1, k2 and k3 for OS-EM were almost equal to those for FBP, the pixel correlation between OS-EM and FBP showed an offset from the line of identity in parametric images, possibly due to different noise characteristics. The kinetic fitting error for OS-EM was no smaller than that for FBP The results suggest that OS-EM is not necessarily superior to FBP for creating parametric images
  Nuclear Science Symposium, 1999. Conference Record. 1999 IEEE; 02/1999
• Conference Proceeding: Correction of partial volume effect on rate constant estimation in compartment model analysis of dynamic PET study

  K. Uemura, H. Toyama, Y. Ikoma, K. Oda, M. Senda, A. Uchiyama
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  ABSTRACT: The estimates for the rate constants in compartment model analysis of ¹⁸F-FDG PET are affected by the fraction of tissue mixture in the ROI, which depends both on the spatial resolution and on the size of the ROI. At first we have evaluated the relationship between the Recovery Coefficient (RC) and estimates of ¹⁸F-FDG rate constants in a ROI without tissue mixture by using a segmented striatum phantom with various resolution. The RC was calculated as the percentage of ROI value to the true activity in the ROI. Next, we have investigated the relationship among the estimates of ¹⁸F-FDG rate constants, spatial resolution and ROI size for the striatum and cerebral cortex, using dynamic digital brain phantom. The activity time course in each tissue was determined with a three-parameter model for ¹⁸F-FDG. Noise was generated by Poisson process according to the collected count for each frame. Sinograms with various spatial resolutions were produced by forward projection, and the images were reconstructed by filtered backprojection method with spatial resolution of 2-12 [mm FWHM]. The parameters (K1, k2, k3, CMRGlc) were estimated by Modified Marquardt method. The fractional tissue component (FTC) was determined as the percentage of the target tissue volume in the total volume of the ROI in the smoothed images. The values of estimates linearly correlated with the FTC for the ROIs with various sizes. The true value was estimated as an extrapolation to 100 [%] FTC on the linear regression line. When this method was applied to the human data for three normal subjects, the estimates also linearly correlated with the FTC and the value at 100 [%] FTC was obtained as a partial volume corrected parameter estimate
  Nuclear Science Symposium, 1999. Conference Record. 1999 IEEE; 02/1999
• Article: Posthyperventilatory steal response in chronic cerebral hemodynamic stress: a positron emission tomography study.

  T Nariai, M Senda, K Ishii, S Wakabayashi, T Yokota, H Toyama, Y Matsushima, K Hirakawa
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  ABSTRACT: The alteration of regional cerebral blood flow (CBF) during and after hyperventilation was measured using positron emission tomography (PET) to determine the circulatory response induced by daily respiratory changes in the cerebral area under chronic hemodynamic stress. Three normal volunteers and 12 patients with an obstruction of major cerebral arteries underwent PET measurements of the CBF after an injection of H2(15)O: (1) in the resting condition, (2) during hyperventilation (HV scan), (3) 1 to 3 minutes after hyperventilation (post-HV scan), (4) during the inhalation of 5% CO2, and (5) after an injection of acetazolamide. Eleven patients also underwent a 15O gas study to measure CBF, oxygen extraction fraction (OEF), and cerebral blood volume (CBV). (1) In 9 patients, the CBF value in the post-HV scan was lower than that in the HV scan in 1 or more regions in the area of the obstructed arteries, although the PaCO2 level during the post-HV scan was higher than that during the HV scan in all patients. All control regions in the patients and in the normal volunteers showed an elevated CBF in the post-HV scan compared with the HV scan. (2) The negative post-HV response (posthyperventilatory steal) was prominent in 4 patients with moyamoya vessels and in another 5 patients with atherosclerotic disease who had PET evidence of hemodynamic stress (elevated CBV or OEF). (3) The regional pre- to post-HV change in CBF was significantly correlated with the CBF responses to acetazolamide and CO2. Vasodilatation after the termination of hyperventilation in the normal areas induces a steal response in the cerebral area suffering from hemodynamic stress and may cause profound hypoperfusion in everyday situations. This phenomenon may be important to our understanding of the clinical symptoms and the natural course of chronic cerebral occlusive disease bearing hemodynamic stress.
  Stroke 08/1998; 29(7):1281-92. · 5.73 Impact Factor
• Article: [Creation of a dynamic digital phantom and its application to a kinetic analysis].

  Y Ikoma, H Toyama, T Yamada, K Uemura, Y Kimura, M Senda, A Uchiyama
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  ABSTRACT: A dynamic digital brain phantom was created from the MRI to evaluate visually the relationship between the noise and the error in the parameter estimates in the PET kinetic analysis. This phantom incorporates the noise level depending on administration dose, camera efficiency and the data acquisition schedule. We simulated a serial dynamic scan with 18F-FDG or 11C-flumazenil, assuming 2-tissue 3-parameter model and 1-tissue 2-parameter model, respectively, and the sampling schedule was determined according to the clinical examination. The noise in the tissue time activity curve in FDG had a peak in the first minute and decreased thereafter, whereas the noise increased gradually in the flumazenil study after the initial peak due to radioactivity decay. We examined the relationship between the noise level and the error in the parameter estimates. Both mean absolute differences between true and estimated values and standard deviation became large, and the quality of the parametric images became poor with increasing noise level. This simulation was compared with human tissue time activity curves and parametric images, which were obtained with 100 MBq administration dose in FDG study and 430 MBq in flumazenil study. We inferred that the noise level in the human study was 10-20% in FDG, and 20-40% in flumazenil, and the error in the estimated parameter of K-complex in FDG study was about 20%, that of DV in flumazenil study was 2%.
  Kaku igaku. The Japanese journal of nuclear medicine 07/1998; 35(5):293-303.
• Source

  Available from: Kenji Ishii

  Article: Data base and management system for clinical positron emission tomography (PET) studies.

  H Toyama, Y Amou, K Ishii, K Oda, M Senda
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  ABSTRACT: A data base and management system connected to an image analysis system has been developed and utilized for clinical positron emission tomography (PET). This data base system, 1) is based on "GBASE", a general purpose data base, which runs on a UNIX work station, 2) works on a network file system and is connected to PET cameras and other data acquisition devices as well as to an image analysis system "Dr.View", 3) centrally manages the data stored in a data storage unit, 4) is easily modifiable and expandable, and 5) has a human friendly interface which requires minimum operation for registration, retrieval and management. We have been using this system to handle clinical PET data for seven years and have optimized the data base schema. As a result, this system has become a truly practical tool for the daily operation and is well-received by technologists, nuclear physicians and attending physicians.
  Annals of Nuclear Medicine 05/1998; 12(2):119-26. · 1.50 Impact Factor
• Source

  Available from: Masahiro Mishina

  Article: Metabolite analysis of [11C]flumazenil in human plasma: assessment as the standardized value for quantitative PET studies.

  K Ishiwata, T Itou, M Ohyama, T Yamada, M Mishina, K Ishii, T Nariai, T Sasaki, K Oda, H Toyama, M Senda
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  ABSTRACT: Analysis of carbon-11 labeled metabolites in plasma was carried out during positron emission tomography (PET) studies with a central benzodiazepine receptor ligand [11C]flumazenil ([11C]FMZ) in 24 human subjects (14-76 y.o.) including five normal volunteers and 19 patients with neurological disorders. Arterial plasma samples were obtained at 3, 5, 10, 15, 20, 30 and 60 min after i.v. injection of the tracer, and were analyzed by high-performance liquid chromatography. The rate of plasma [11C]FMZ degradation was associated with a large individual variation, but no significant difference was found in the degradation of [11C]FMZ either between male and female, young and old, or between normal subjects and patient groups. When the mean fraction of unchanged [11C]FMZ at each time point was used instead of individually measured metabolite data for the arterial input function, as much as a 30% error occurred in the distribution volume of the [11C]FMZ binding in the brain. These results indicate that the mean percentage of unchanged [11C]FMZ fraction in subjects cannot be used as the standardized value, and that the analysis of metabolites in plasma is necessary to determine the exact arterial input function for quantitative PET measurement.
  Annals of Nuclear Medicine 03/1998; 12(1):55-9. · 1.50 Impact Factor
• Source

  Available from: Tadashi Nariai

  Article: Evaluation of carbon-11-labeled KF17837: a potential CNS adenosine A2a receptor ligand.

  J Noguchi, K Ishiwata, S Wakabayashi, T Nariai, S Shumiya, S Ishii, H Toyama, K Endo, F Suzuki, M Senda
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  ABSTRACT: The 11C-labeled KF17837 ([7-methyl-11C](E)-8-(3,4-dimethoxystyryl)-1,3-dipropyl-7-methylxa nthine) was evaluated as a PET ligand for mapping adenosine A2a receptors in the central nervous system (CNS). The regional brain distribution of [11C]KF17837 and the effect of adenosine antagonists on the distribution were measured in mice by the tissue sampling method. In rats, the regional brain uptake of [11C]KF17837 and the effect of carrier KF17837 was visualized by autoradiography. Imaging of the monkey brain with [11C]KF17837 was performed by PET. In mice, a high uptake of [11C]KF17837 was found in the striatum in which A2a receptors were highly enriched. The uptake was decreased by co-injection of carrier KF17837 or a xanthine-type A2a antagonist CSC but not by nonxanthine-type A2a antagonists ZM 241385 or SCH 58261, or an A1 antagonist KF15372. In the rat brain, [11C]KF17837 was accumulated higher in the striatum than in other brain regions, and the uptake was blocked by co-injection of carrier KF17837. In a monkey PET study, a high striatal uptake of radioactivity was observed. Carbon-11-KF17837 binds to adenosine A2a receptors in the striatum. However, the presence of an unknown but specific binding site for xanthine-type compounds also was suggested in the other brain regions. The results also suggested that the in vivo receptor-binding sites of xanthine-type ligands are slightly different from those of nonxanthine-type A2a antagonists.
  Journal of Nuclear Medicine 03/1998; 39(3):498-503. · 6.38 Impact Factor
• Article: Positron emission tomography reveals changes in global and regional cerebral blood flow during noxious stimulation of normal and inflamed elbow joints in anesthetized cats.

  Y Sakiyama, A Sato, M Senda, K Ishiwata, H Toyama, R F Schmidt
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  ABSTRACT: In cats the global (gCBF) as well as the regional cerebral blood flow (rCBF) and blood pressure were measured before, during, and after noxious inward and outward rotations of normal and inflamed elbow joints. The animals were anesthetized with halothane and immobilized by gallamine triethiodide. The gCBF as well as the rCBF were measured using positron emission tomography (PET) with a camera specifically designed for use in small animals. Slow intravenous bolus injections of 15O-labeled water were followed by 3-min acquisition of regional radioactivity starting at the time of injection. In all experiments the gCBF as well as the blood pressure were increased by noxious inward-outward rotations of the normal and of the inflamed joint, whereas the blood pressure and the rCBF remained unchanged during bolus injections under control conditions (without any joint movement). Movements of the inflamed joint evoked significantly greater increases in blood pressure and gCBF than corresponding ones of the normal joint. These increases in gCBF were paralleled by increases in rCBF along the complete anterior to posterior axis of the brain. Again, the increases in rCBF were larger, more extensive and more uniform following the stimulation of the inflamed joint relative to the results obtained with stimulation of the normal joint. No significant laterality was seen, but when an atlas-based region of interest (ROI) analysis was carried out and when the individual variations in rCBF were removed with two-way ANOVA, significant differences were disclosed in rCBF between the stimulated condition and the resting condition in a large number of brain regions. In particular, noxious rotation of the normal (right) elbow joint induced a significant increase in rCBF over the cerebral cortex and in the right thalamus and hippocampus. The same stimulation of the (left) inflamed joint induced a significant increase in rCBF throughout the brain; the biggest increase being over the right posterior cortex. It is concluded that under the conditions of the present experiments the generally accepted autoregulation of the cerebral blood flow is not fully functioning, and various factors that may be responsible for this failure (which obscures rCBF differences) are discussed. The more pronounced increases in rCBF when moving inflamed joints instead of normal ones is thought to be a direct consequence of the peripheral sensitization of the articular nociceptors and the consequent central hyperexcitability induced in the articular nociceptive pathways.
  Experimental Brain Research 02/1998; 118(4):439-46. · 2.39 Impact Factor
• Article: A stereotaxic method of anatomical localization by means of H(2)15O positron emission tomography applicable to the brain activation study in cats: registration of images of cerebral blood flow to brain atlas.

  Y Sakiyama, H Toyama, K Oda, S Ishii, K Ishiwata, K Ishii, A Suzuki, H Nakayama, M Senda
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  ABSTRACT: In the neuronal activation study of normal animals, precise anatomical correlation, preferentially to a detailed brain atlas, is required for the activation foci co-registration. To obtain precise regional correlation between H(2)15O-PET images and the brain atlas, a method of stereotaxic image reorientation was applied to an activation study with vibrotactile stimulation. Cats anesthetized with halothane underwent repeated measurements of regional cerebral blood flow (rCBF) in the resting condition and during vibration of the right forepaw. The image set was adjusted three-dimensionally to the atlas. The postmortem brain was sectioned according to the atlas planes. The activated areas were determined by the stimulus-minus-resting subtraction images, and the areas were projected to the atlas. The PET images of the cat brain were compatible both to the postmortem brain slices and to the brain atlas. The activation foci obtained from the subtraction images corresponded to the area around the coronal sulcus, which is electrophysiologically known as the primary sensory area as described in the atlas. There were precise regional correlations between the PET image and anatomy in a PET activation study of the cat by means of stereotaxic image reorientation.
  Annals of Nuclear Medicine 12/1997; 11(4):315-9. · 1.50 Impact Factor