Biomedical subjects

R Kawashima

Publications and source records attributed to R Kawashima.

At least 91 records · Page 5Linked to original sources

PubMed1996

Hypoperfusion in the limbic system and prefrontal cortex in depression: SPECT with anatomic standardization technique.

UNLABELLED: Depression is a common psychiatric illness, and several reports have described cerebral blood flow (CBF) abnormalities on SPECT studies in affected patients. However, because region of interest analyses were used to determine significant CBF changes in these studies, there were methodological limitations. Therefore, we investigated CBF distribution abnormalities in depression on a pixel-by-pixel basis using SPECT and an anatomic standardization technique that has been commonly used for PET activation studies. METHODS: Eleven patients with unipolar depression, six patients with bipolar depression and nine age-matched normal control subjects underwent HMPAO brain SPECT studies. The radioactivities of SPECT images for each subject were globally normalized to 100 counts/pixel. Then, each SPECT image was transformed for standard brain anatomy using a computerized Human Brain Atlas system. For each group, the mean and variance images were calculated from the standardized anatomic SPECT images, and group comparisons were performed on a pixel-by-pixel basis. RESULTS: Significant decreases in CBF in the prefrontal cortices, limbic systems and paralimbic areas were observed in both depression groups compared with the normal control group. CONCLUSION: Decreases in CBF in these regions may be related to impaired attention as well as cognitive and emotional responses, which have been recognized as usual symptoms in depression. The anatomic standardization technique promises to be useful for group comparison analysis of brain SPECT on a pixel-by-pixel basis for individual neurological and psychiatric diseases.

Aged↗

PubMed1996

[Regional distribution of the muscarinic cholinergic receptor in the human brain studied with 11C-benztropine and PET using an anatomical standardization technique].

We measured regional distribution of the muscarinic cholinergic receptor in the normal human brain with 11C-benztropine (BZT) and positron emission tomography (PET) using an anatomical standardization technique. Seven normal volunteers who gave informed consents were involved in this study. Immediately after intravenous injection of 11C-BZT into the subjects, we started dynamic PET scanning and serial frequent arterial blood sampling. Analyses of plasma metabolites were also performed at selected time points and plasma time activity curves (TAC) of unmetabolized ligand were generated. From these PET and TAC data, we obtained Patlak plot slope calculation images. Using the HBA (human brain atlas) system, the Patlak plot slope calculation image of each subject was transformed into the shape of the standard brain. Mean and standard deviation (SD) calculation images were generated from those anatomically standardized images. On these mean and SD images, we placed regions of interest which were previously outlined on a MR image of the standard brain. From those data, we found the highest receptor distribution in the striatum and occipital cortex, as well as high distribution in the frontal, parietal, and temporal cortices, which were consistent with previous reports. These results suggested that anatomical standardization of PET receptor images with 11C-BZT will be useful for delineating the physiological or pathological alterations of the muscarinic cholinergic receptor in the human brain.

Adolescent↗

PubMed1996

[Normal cerebral perfusion of 99mTc-ECD brain SPECT--evaluation by an anatomical standardization technique].

A single photon emitter labeled tracer, 99mTc-ethyl cysteinate dimer (99mTc-ECD), has now been used for rCBF studies with SPECT. However, normal distribution pattern of this agent in the brain still remains unclear. Therefore, the specific purpose of this study was to investigate the normal distribution pattern of 99mTc-ECD SPECT image. Regional cerebral distribution was measured with SPECT and 984 +/- 17 MBq of 99mTc-ECD in ten normal subjects. During the SPECT measurement, subjects were placed comfortably in a supine position with their eyes closed. Each SPECT image was anatomically standardized using a computerized brain atlas system of Roland et al. (HBA: Human Brain Atlas) and X-CT image. Anatomically standardized SPECT images were globally normalized to 100 count/voxel. Then, the mean and SD images of brain SPECT were calculated voxel-by-voxel basis. The highest radioactivity was found in the medial aspect of the occipital lobe. The results indicate that the normal distribution pattern of 99mTc-ECD in the human brain may be not simply reflect the regional cerebral blood flow.

Adult↗

PubMed1996

[Development of a new statistical evaluation method for brain SPECT images].

The purpose of this study was to develop a new statistical evaluation method for Brain SPECT images. First, we made normal brain image databases using 99mTc-ECD and SPECT in 10 normal subjects as described previously. Each SPECT images were globally normalized and anatomically standardized to the standard brain shape using Human Brain Atlas (HBA) of Roland et al. and each subject's X-CT. Then, mean and SD images were calculated voxel by voxel. For the next step, 99mTc-ECD SPECT images of a patient were obtained, and global normalizing and anatomical standardization were performed as the same way. Then, a statistical map was calculated as following voxel by voxel; (P-Mean)/SD x 10 + 50, where P, Mean and SD indicate voxel value of patient, mean and SD images of normal databases, respectively. We found this statistical map was helpful for clinical diagnosis of brain SPECT studies.

Brain↗

PubMed1995

Positron-emission tomography studies of cross-modality inhibition in selective attentional tasks: closing the "mind's eye".

It is a familiar experience that we tend to close our eyes or divert our gaze when concentrating attention on cognitively demanding tasks. We report on the brain activity correlates of directing attention away from potentially competing visual processing and toward processing in another sensory modality. Results are reported from a series of positron-emission tomography studies of the human brain engaged in somatosensory tasks, in both "eyes open" and "eyes closed" conditions. During these tasks, there was a significant decrease in the regional cerebral blood flow in the visual cortex, which occurred irrespective of whether subjects had to close their eyes or were instructed to keep their eyes open. These task-related deactivations of the association areas belonging to the nonrelevant sensory modality were interpreted as being due to decreased metabolic activity. Previous research has clearly demonstrated selective activation of cortical regions involved in attention-demanding modality-specific tasks; however, the other side of this story appears to be one of selective deactivation of unattended areas.

Brain↗

PubMed1995

Activity in the human primary motor cortex related to arm and finger movements.

With the purpose of mapping representations of the finger and proximal arm in the human primary motor cortex (MI), we measured regional cerebral blood flow (rCBF) in eight right-handed normal volunteers during self-paced finger and proximal arm movements. Each movement activated two different fields in MI, one located deep in the anterior lip of the central sulcus and the other relatively close to the surface of the precentral gyrus. Arm fields were located higher than finger fields. A superficial arm field and a deep finger field partially, overlapped. The results indicate that there are two spatially separate motor representations of the finger and proximal arm in the human MI.

Adult↗

PubMed1995

Error analysis of table look-up method for cerebral blood flow measurement by 123I-IMP brain SPECT: comparison with conventional microsphere model method.

While N-isopropyl-p-[123I]iodoamphetamine (IMP) is commonly used as a flow tracer, significant clearance from the brain causes underestimation of CBF as compared with true CBF when conventional microsphere model analysis is applied. We previously reported a simple "table look-up" method for CBF measurement using IMP taking into account this clearance effect. The method is based on a two-compartment model, the K1 (corresponding to CBF) and k2 constants being obtained from a table from the ratio of the 1st SPECT (40 min) to the 2nd SPECT (180 min) counts. Arterial input data used were obtained by one point blood sampling 10 min after IMP infusion against the standard input function. In the present study, this approach was compared with conventional microsphere model analysis. For 30 subjects, the latter method entailed 8 min continuous arterial blood sampling after IMP infusion and the use of SPECT data at the end of this period, calibrated by a count ratio of 8 min/40 min planar images of whole brains. A good correlation was observed between the two methods (r = 0.88), but an overestimation of table look-up method CBF as compared with microsphere model CBF was observed contrary to theoretical predictions. Limitations in the estimation of SPECT data at 8 min, obtained with SPECT data at 40 min for calibration of the count ratio of 8 min/40 min whole brain planar images, might be responsible for this.

Amphetamines↗

PubMed1995

Error analysis of autoradiography method for measurement of cerebral blood flow by 123I-IMP brain SPECT: a comparison study with table look-up method and microsphere model method.

N-isopropyl-p-[123I]iodoamphetamine (IMP) has been commonly used as a cerebral blood flow tracer, but, significant clearance of IMP from the brain to the blood causes underestimation of cerebral blood flow (CBF) as compared with true CBF when the conventional microsphere model method is applied. Previously, we reported an "Autoradiography method" (ARG method) for measuring CBF by using IMP in which this clearance effect was corrected. This method was based on a two-compartment model (influx: K1, efflux: k2, K1/k2 = distribution volume of IMP (Vd)), the K1 (corresponding to CBF) being obtained form the table which showed a correlation between CBF and the brain counts of SPECT scan with a constant Vd value. Arterial input data used were obtained by one point blood sampling 10 min after IMP infusion against the standard input function. In the present study, the ARG method was compared with the table look-up method (TLU method) and the conventional microsphere model method (MS method) for 30 subjects. When the Vd value in the ARG method was assumed to be 50 ml/ml, CBF values obtained by the ARG method were correlated well with those obtained by the TLU method (Y = 1.04X-2.5; X: TLU, Y: ARG r = 0.97) and those obtained by the MS method (Y = 0.82X + 12.1; X: ARG, Y: MS, r = 0.84). But, when the Vd value was assumed to be more or less than 50 ml/ml, ARG method CBF were under- or overestimated compared with the TLU method. This indicated that the ARG method could be a reliable method for CBF measurement if the Vd was determined properly. CBF values obtained by the MS method were actually 13.2% higher than those obtained by the ARG method against previous studies. As reasons for this, errors in the effects of gray-white matter mixture in the ARG method and in estimation of the SPECT brain counts at 8 min in the MS method were considered.

Amphetamines↗

PubMed1995

[A new 3-dimensional head fixation device for brain imaging].

We have developed a new head fixation device for studies of brain function. This device was designed to immobilize subject's heads during image scanning and to precisely reproduce the head position for two different imaging modalities such as MRI and PET. The device consists of a plastic frame, a pillow filled with beads of styrene foam, and a face mask of thermoplastic resin which was originally intended for application in radiotherapy. A bridge for biting was incorporated into the mask for stable fixation. The device enables immobilization of subject's heads with good reproducibility of position at the practical level. Our results indicate that this head fixation system is useful for fixation of head during activation studies using PET.

Brain↗

PubMed1995

Cerebral blood flow measurement with iodine-123-IMP SPECT, calibrated standard input function and venous blood sampling.

UNLABELLED: We previously reported simple methods for measuring cerebral blood flow (CBF) with 123l-labeled N-isopropyl-p-iodoamphetamine (IMP) and SPECT: table look-up method and autoradiography. With these methods, the arterial input function is obtained by calibrating the standard input function using one-point arterial blood sampling 10 min after IMP infusion. In this study, we sought to determine if these approaches can be as successful when used with venous blood sampling. METHODS: After IMP infusion, simultaneous arterial and venous blood samples were drawn from 30 subjects without heart or lung disease. RESULTS: The activity ratios of venous whole blood from the cubital vein to arterial blood were 0.75 +/- 0.09, 0.77 +/- 0.10, 0.78 +/- 0.03 and 0.83 +/- 0.11, respectively, at 10, 20, 30 and 50 min after IMP infusion. Venous blood activities were always 20% lower than the artery values over 50 min. When blood was sampled from the dorsal hand vein, however, the respective ratios were 0.92 +/- 0.03, 0.93 +/- 0.05, 0.97 +/- 0.04 and 0.98 +/- 0.08 after 10, 20, 30 and 50 min. Furthermore, when the palm was exposed to heat during the sampling period, blood activity levels increased to 0.92 +/- 0.04, 0.96 +/- 0.04, 0.99 +/- 0.05 and 0.98 +/- 0.03. Thus, venous blood activities were consistent with arterial activity, presumably because of the numerous arteriovenous anastomoses in the palm. Optimal times for venous blood sampling, with and without palm heating, were determined by error analysis to be 15 and 20 min, respectively, after IMP infusion. CONCLUSION: Venous blood sampling from the dorsal hand can be substituted for arterial blood sampling in IMP-CBF studies.

Amphetamines↗

PubMed1995

[Normal cerebral perfusion of 99mTc-HMPAO brain SPECT--evaluation by ananatomical standardization technique].

Single photon labeled tracer 99mTc-hexamethylpropylene amine oxime (HMPAO) has been used for rCBF studies by SPECT. However, normal perfusion pattern of this agent still remains unclear. The purpose of this study was to investigate normal 99mTc-HMPAO SPECT image voxel by voxel. Eighteen male subjects without any prior or present history of medical illness participated in this study. All SPECT images were globally normalized to 100 count/voxel. Each subject had an X-ray CT scan at the same day of SPECT measurement. All subjects had normal X-ray CT scans. The standard anatomical structures of the computerized brain atlas of Roland et al. were fitted to X-ray CT images of a subject by linear and non-linear parameters. These parameters were subsequently used to transform SPECT images of the subject. After the anatomical standardization, mean and SD images of eight standardized images were calculated voxel-by-voxel basis. In the mean image, following structures showed relatively higher radioactivity; the putamen, the cerebellum, and the frontal lobe. In addition, the occipital lobe, parietal lobe, frontal lobe, and the putamen showed large degree of SD. Anatomical standardization of SPECT images may be useful as a reference to diagnose and evaluate various brain disorders.

Adult↗

PubMed1994

The human entorhinal cortex participates in associative memory.

Animal studies have shown that lesions of the parahippocampal cortex impair learning of visual stimulus-stimulus associations. We tested the hypothesis that recall of paired associates, in contrast to recall of non-associated items, activates the parahippocampal cortex in humans. Ten volunteers had their regional cerebral blood flow measured with positron emission tomography during non-associative recall, and during two conditions with associative recall of visual stimuli. Compared with non-associative recall, associative recall specifically increased the blood flow in a field located in the entorhinal cortex, extending into the presubiculum. Our results demonstrate functional differences between the human hippocampal and parahippocampal cortex, and show that the entorhinal cortex is engaged in associative memory.

Association Learning↗

PubMed1994

Activity in the human primary motor cortex related to ipsilateral hand movements.

In two studies with positron emission tomography (PET), we found that somatosensory discrimination of length activated the ipsilateral MI, but somatosensory discrimination of shape did not. This occurred even though both tasks required the exclusive use of distal finger and hand movements which were also very similar in both tasks. The activation of the ipsilateral MI was correlated with activations of the premotor cortex in the other hemisphere, the prefrontal cortex and the posterior cingulate cortex, indicating that these areas together with the ipsilateral MI constitute a task-related active network.

Discrimination Learning↗

PubMed1994

Functional anatomy of taste perception in the human brain studied with positron emission tomography.

Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) in 10 normal volunteers with the purpose of measuring rCBF changes related to taste physiology. Discrimination of 0.18% saline from pure water was associated with significantly increased rCBF values in the thalamus, the insular cortex, the anterior cingulate gyrus, the parahippocampal gyrus, the lingual gyrus, the caudate nucleus, and the temporal gyri. The results indicate that rCBF changes in these structures may reflect oral exposure to salt.

Adolescent↗

PubMed1994

A PET study of somatosensory discrimination in man. microgeometry versus macrogeometry.

The regional cerebral blood flow (rCBF) was measured with 15O-butanol and positron emission tomography (PET) in 10 healthy subjects in order to compare cerebral activation involved in the somatosensory discrimination of microgeometric features with cerebral activation associated with the discrimination of macrogeometric features. Subjects performed two-alternative forced choice (2-AFC) discriminations of pairs of stimuli from a series of quantified standardized stimuli that differed in roughness (microgeometry), and a separate 2-AFC task of smooth tactile stimuli that differed in length (macrogeometry). Results are presented from three conditions: (1) a roughness discrimination task; (2) a length discrimination task; and (3) a control trial in which subjects were required to reproduce similar exploratory finger movements only, but without a specific stimulus to feel. Mean subtraction images were computed using the computerized adjustable brain atlas of Greitz et al. (1991, J. Comput. Assisted Tomogr., 15, 26-38) and areas of significant blood flow change were identified. Both the roughness and the length discrimination tasks activated overlapping cortical fields contralaterally in the anterior and posterior lip of the postcentral sulcus. However, in the length discrimination, activation of the posterior lip of the postcentral sulcus extended deeper into the sulcus and there was also a separate additional area of activation in the anterior part of the precentral gyrus. Furthermore, the length discrimination task activated fields in the overt part of the supramarginal gyrus bilaterally as well as fields in the angular gyrus bilaterally. Thus roughness discrimination uses only a subset of the cortical regions that are needed for the recovery of length information, which requires more extensive somatosensory processing. This finding may be partly explained in that length perception needs both edge detection of the stimuli used, as well as integrated information of surface length and velocity, which is not necessary for roughness perception. Specific differences in the acquisition of necessary tactile information between the two discrimination tasks was reflected in different sampling strategies.

Adult↗

PubMed1994

[Ventricular premature contraction observed after anti-cancer chemotherapy with ifosfamide].

We encountered 3 cases of ventricule premature contraction (VPC) after anti-cancer chemotherapy with ifosfamide (IFM). These cases were administered IFM of more than 2 g/body/day for 3 days, and they were more than 70 years old. They had no cardiovascular disorder before the chemotherapy. Among them, 1 case who received a total dose of 15.0 g of IFM showed severe VPC. She had also received a total dose of 155 mg of doxorubicin (ADM) in earlier treatment. There was also 1 case, whose VPC was aggravated after anti-cancer chemotherapy with IFM. He had dilated cardiomyopathy and had already showed frequent VPC before the chemotherapy. His VPC became more frequent after the chemotherapy. IFM was a common agent among the anti-cancer agents used in these cases. We must be careful for the occurrence of VPC when more than 2 g/body/day of IFM is administered to patients more than 70 years old. An increase in the total dose of IFM or former ADM may cause severe VPC. When IFM is given a patient with VPC, the existing VPC may be aggravated.

Aged↗

PubMed1994

[A simple method for measurement of cerebral blood flow using 123I-IMP SPECT with calibrated standard input function by one point blood sampling; validation of calibration by one point venous blood sampling as a substitute for arterial blood sampling].

In a simplified method for measurement of cerebral blood flow using one 123I-IMP SPECT scan and one point arterial blood sampling (Autoradiography method), input function is obtained by calibrating a standard input function by one point arterial blood sampling. A purpose of this study is validation of calibration by one point venous blood sampling as a substitute for one point arterial blood sampling. After intravenous infusion of 123I-IMP, frequent arterial and venous blood sampling were simultaneously performed on 12 patients of CNS disease without any heart and lung disease and 5 normal volunteers. The radioactivity ratio of venous whole blood which obtained from cutaneous cubital vein to arterial whole blood were 0.76 +/- 0.08, 0.80 +/- 0.05, 0.81 +/- 0.06, 0.83 +/- 0.11 at 10, 20, 30, 50 min after 123I-IMP infusion, respectively. The venous blood radioactivities were always 20% lower than those of arterial blood radioactivity during 50 min. However, the ratio which obtained from cutaneous dorsal hand vein to artery were 0.93 +/- 0.02, 0.94 +/- 0.05, 0.98 +/- 0.04, 0.98 +/- 0.03, at 10, 20, 30, 50 min after 123I-IMP infusion, respectively. The venous blood radioactivity was consistent with artery. These indicate that arterio-venous difference of radioactivity in a peripheral cutaneous vein like a dorsal hand vein is minimal due to arteriovenous shunt in palm. Therefore, a substitution by blood sampling from cutaneous dorsal hand vein for artery will be possible. Optimized time for venous blood sampling evaluated by error analysis was 20 min after 123I-IMP infusion, which is 10 min later than that of arterial blood sampling.

Amphetamines↗

PubMed1994

Fields in human motor areas involved in preparation for reaching, actual reaching, and visuomotor learning: a positron emission tomography study.

The purpose of this study was to examine the functional organization of motor cortices in the human brain involved in reaching and visuomotor learning. All subjects were asked to learn the positions of seven circular targets projected on a screen. Each time the targets were turned off, they were required to close their eyes and keep them closed, and, after a delay, to point to the center of the targets in a prescribed order using their right hand. The regional cerebral blood flow (rCBF) was measured with 15O-butanol and positron emission tomography in 20 subjects during a rest state, an initial learning stage, and a later learning stage. Ten subjects constituted the reaching group in which rCBF was measured during actual reaching; the 10 other subjects constituted the preparation group in which rCBF was measured in the delay period between target exposure and actual reaching. Individual subtraction images (each stage minus rest) were calculated and transformed into a standard size and shape brain image by the adjustable computerized brain atlas and averaged, after which significant changes of rCBF were identified. In all reaching and preparation for reaching phases, cortical fields were activated in the left primary motor area (M1) and the left premotor area (PMA). Within M1, fields active in the delay phases were adjacent to the fields active only during actual reaching movements. During the course of learning, additional fields of activity appeared in both M1 and PMA. The results indicate that three types of fields occur in M1 and PMA: (1) fields directly engaged in the efferent control of peripheral muscle contraction, (2) fields engaged in preparatory activity for reaching, and (3) fields appearing after learning of the task has taken place.

Adult↗