Biomedical subjects

N Sadato

Publications and source records attributed to N Sadato.

At least 109 records · Page 6Linked to original sources

PubMed1995

The role of reading activity on the modulation of motor cortical outputs to the reading hand in Braille readers.

We studied the cortical motor output maps of the first dorsal interosseous (FDI) of both hands and the abductor digiti minimi of the reading hand in 6 blind proficient Braille readers. The maps were generated using transcranial magnetic stimulation. We compared the maps obtained on a day in which they worked as Braille proofreaders (reading Braille for approximately 6 hours) with the maps obtained on a day they took off from work. On the work day, the maps for the FDI of the reading hand were significantly larger after the working shift than in the morning after having been off work for 2 days. These changes were not seen for the same muscle on the day off work or on any of the 2 days in the other two muscles studied. These results illustrate the rapid modulation in motor cortical outputs in relation to preceding activity and emphasize the importance of precise timing in studies of the neurophysiological correlates of skill acquisition.

Adult↗

PubMed1995

Changes in cerebral blood flow induced by balloon test occlusion of the internal carotid artery under hypotension.

Balloon test occlusion (BTO) of the internal carotid artery (ICA) combined with cerebral blood flow (CBF) study has proved to be a sensitive test for prediction of the outcome of permanent vessel occlusion. In this study, we evaluated the acute changes in regional CBF during BTO under hypotension in order to examine the possible risk of cerebral ischaemia after surgical treatment. Eleven patients in whom surgical carotid sacrifice was planned underwent BTO combined with CBF studies using technetium-99m hexamethyl-propylene amine oxime single-photon emission tomography under hypotension by decreasing the systemic blood pressure by about 50 mm Hg using a ganglion blocking agent. All patients showed a mild to severe decrease in CBF in the ipsilateral ICA territory relative to the contralateral side. A decrease in CBF of greater than 20% was observed in nine patients (82%), and two of them showed a decrease exceeding 40%. However, no ischaemic symptoms were demonstrated during scanning with hypotensive BTO. Our results suggest that in many patients with negative normotensive BTO, a considerable reduction in CBF would occur during hypotension. This procedure may predict a possible risk of hypotensive accident during and/or after surgery.

Adult↗

PubMed1995

Clinical application of 62Zn/62Cu positron generator: perfusion and plasma pool images in normal subjects.

We have developed a new 62Zn/62Cu positron generator, and applied it for PET imaging of perfusion and plasma volume in 5 normal subjects. The generator makes it possible by a simple procedure to obtain 62Cu eluate and labeling compounds sufficiently every 40-60 minutes. 62Cu labeled pyruvaldehyde bis(N4-methylthiosemicarbazone) copper II (62Cu-PTSM) was employed for cerebral and myocardial perfusion imaging and 62Cu labeled human serum albumin-dithiosemicarbazone (62Cu-HSA-DTS) was used for plasma pool imaging. The images of cerebral blood flow, cerebral plasma volume and myocardial perfusion were excellent. In addition, the analysis of tissue activity and blood activity demonstrated the microspheric character of 62Cu-PTSM. Correction of arterial activity with the standard disappearance curve of 62Cu-PTSM suggested the possibility of quantifying blood flow. The results of this study indicate the capability of the 62Zn/62Cu generator for wide clinical use without an in-house cyclotron.

Adult↗

PubMed1995

Effects of stimulus rate on regional cerebral blood flow after median nerve stimulation.

The primary motor cortex and supplementary motor area (SMA) are purportedly involved in the generation of the P22 and N30 components of somatosensory evoked potentials (SEPs) evoked by electrical stimulation of the median nerve at the wrist. We used regional cerebral blood flow (rCBF) measurements and PET in 10 normal subjects to study the cerebral areas activated by median nerve electrical stimulation. PET scans were performed with the subjects at rest and during stimulation of the right median nerve at frequencies of up to 20 Hz. Stimulation evoked a single focus of activation in the primary somatosensory area (SI). An increase of rCBF in this area was linearly correlated with stimulus frequencies of up to 4 Hz and then reached a plateau. The SMA was not significantly activated by stimulation at any of the frequencies tested. In contrast to the SI, the SMA showed no trend toward a correlation between the rCBF changes and the stimulus repetition rate. In order to achieve maximal resolution in the sensorimotor cortex, regions of interest were placed in individual co-registered MRI-PET images on both sides of the central sulcus. There was no significant increase of rCBF in the crown of the precentral gyrus. These results suggest that a contribution of the primary motor cortex and the SMA to the generation of the P22 and N30 components of SEPs is unlikely. Consequently, functional clinical interpretations derived from P22 or N30 abnormalities must be reconsidered.

Adult↗

PubMed1995

Delayed data acquisition for optimal PET activation studies with oxygen-15-water in cerebral arteriovenous malformation.

UNLABELLED: In the clinical application of activation PET studies with 15O-water, optimal PET images are required when the high activity of a nearby lesion might affect the activated area. METHODS: To determine the optimal time for data acquisition of PET images, we performed serial dynamic PET measurements in five patients with cerebral arteriovenous malformation (AVM). All AVMs were closest to the motor cortices, and the activation task was opponent finger movement contralateral to the AVM. Activation PET and MR images were coregisterated for localization of activated foci. RESULTS: Time-activity curves of the nidus and normal cortex from the dynamic PET data demonstrated a discrepancy in peak time and significant radioactivity increase in the nidus during the early phase. Elimination of the initial PET data provided better contrast in activated foci without affecting the calculated cerebral blood flow of other areas. CONCLUSION: Delayed data acquisition can avoid interference of the AVM nidus with the activated area.

Adult↗

PubMed1994

Spinal epidural abscess with gadolinium-enhanced MRI: serial follow-up studies and clinical correlations.

We reviewed serial MRI with and without gadolinium-DTPA in eight patients with spinal epidural abscess and correlated the findings and the clinical manifestations. In four patients, diffuse abscesses spanned four vertebral bodies or more; the others had focal abscesses associated with osteomyelitis and/or diskitis. In three of the four patients with diffuse abscesses, MRI (NCMRI) showed diffuse encasement of the subarachnoid space. Contrast-enhanced MRI (CEMRI) demonstrated linear enhancement surrounding unenhanced pus. In the four patients with focal abscesses, CEMR delineated the inflammatory process more clearly than NCMR. On follow-up studies, decrease in abscess size and better visualization of the subarachnoid space correlated with clinical improvement in both diffuse and focal abscesses. Despite clinical improvement, contrast enhancement persisted in the disk or epidural space of three patients, and was thought to represent chronic granulomatous change or postsurgical scar. CEMR is very valuable for the initial diagnosis of an epidural abscess, particularly if it involves lengthy segments. During follow-up, CEMR can document responses to therapy, and provide information for determining appropriate treatment.

Abscess↗

PubMed1994

Comparison of anatomical standardization methods regarding the sensorimotor foci localization and between-subject variation in H2(15)O PET activation, a three-center collaboration study.

Identical sets of H2(15)O-PET brain activation data regarding vibrotactile stimulation and voluntary motion of the fingers in seven young normal subjects, together with the MRI, were analyzed in three PET centers by means of each center's own method of anatomical standardization to Talairach's frame. Every center used a linear or segmentally linear transformation with various number of scaling factors. A variation of 6-8 mm in each axis was observed in the foci localization due to the difference in the transformation principle and the measured brain size. Between-subject variation was similar in all the centers. Since different standardization methods define different coordinate systems, a cautious attitude should be taken to comparing results analyzed at different centers.

Adult↗

PubMed1994

Optimal dose of injection in activation study with O-15 water and PET.

In activation studies with the bolus method for O-15 water and PET, the radiotracer concentration may reach the limits of the system in terms of dead time correction and accidental coincidence. To obtain the optimal injection dose of O-15 water, we performed a normal volunteer study to evaluate the relationship between the injected dose and the radioactivity concentration in the brain and a phantom study to evaluate the performance of the PET scanner (PCT3600W) under high count rate conditions and the effect of averaging on the signal to noise ratio for the PET images. A linear relationship was noted between the injected dose (normalized for each body weight: x) and the mean radiotracer concentration in the brain measured by PET (y) (y = 2.52 + 30.1 x, n = 64, r = 0.87, p < 0.001). The percent error in the measurement of radioactivity with PET was within +/- 5% in the 100 to 2000 nCi/ml (3.7-74 KBq/ml) range. Below 100 nCi/ml (3.7 KBq/ml), the percent error increased due to the rapid increase in noise in the reconstructed images. Over 1000 nCi/ml (37 KBq/ml), on the other hand, the noise was almost unchanged. With our PET scanner, the optimal range of the radiotracer concentration in the brain is below 1000 nCi/ml (37 KBq/ml), corresponding to an injection dose of 33 mCi (1.22 GBq)/60 kg body weight. With the same total dose, the increment of number of repeated measurements for averaging provided the better signal to noise ratio. In designing a paradigm for an activation PET study, the injection dose and the number of repeated measurements for averaging should be considered.

Adult↗

PubMed1994

Effects of hyperglycemia on FDG uptake in human brain and glioma.

UNLABELLED: This study evaluates the effects of hyperglycemia on fluorodeoxyglucose (FDG) uptake in the human brain and in brain tumors. METHODS: We performed glucose loading during FDG PET studies in nine patients with brain tumors (eight gliomas and one brain metastasis) and one with resected glioma. Two FDG PET scans were obtained in all cases within 1 wk in a control state and with glucose loading by intravenous infusion of 10% glucose solution. Serial arterial blood sampling was performed in all cases to obtain fractional uptake of FDG normalized by the plasma integral uptake of radioactivity (FU). RESULTS: In all nine patients with brain tumors, the tumor was depicted more clearly with glucose loading than in the control state. Glucose loading decreased FU in the cerebral cortex (54.2% +/- 13.8%) nearly in inverse proportion to the plasma glucose level, while the tumors showed a decrease (42.5% +/- 15.6%), resulting in an increased tumor-to-cortex ratio by 26.0% +/- 5.7%. Fractional uptake in the cerebellum, white matter and the edematous area also decreased by glucose loading (53.9% +/- 13.2%, 49.6% +/- 10.3% and 34.9% +/- 9.6%, respectively). CONCLUSION: These results demonstrate the different effects of hyperglycemia on normal brain tissue and on tumor, suggesting that glucose loading may be a valuable adjunct to FDG PET to enhance detection of recurrent or residual brain tumors.

Adult↗

PubMed1994

Brain perfusion SPECT with 99mTc-bicisate: comparison with PET measurement and linearization based on permeability-surface area product model.

To characterize a recently introduced cerebral perfusion tracer, 99mTc-bicisate, single photon emission computed tomography (SPECT) images of 99mTc-bicisate were compared with CBF images obtained by positron emission tomography (PET) using the 15O steady-state method in 10 cases of cerebrovascular disease and dementia. 99mTc-Bicisate SPECT and PET CBF images showed a similar distribution pattern except for two cases with subacute stroke, in which 99mTc-bicisate showed less uptake than CBF in the infarcted area where oxygen metabolism was severely diminished. Comparison of 99mTc-bicisate uptake and CBF in the other eight cases showed less contrast between high- and low-flow regions in 99mTc-bicisate SPECT. Although the SPECT count ratio of cerebral structures to cerebellum showed a good correlation with CBF ratio, it gradually deviated from the linear relationship in the high-flow range. Assuming this nonlinear relationship is due to the limited extraction of the tracer, we estimated the permeability-surface area product (PS) value by a nonlinear least-squares curve-fitting procedure. The correction of the nonlinear relationship using the estimated PS value and a table lookup method resulted in an excellent linear relationship between corrected SPECT counts and CBF.

Adult↗

PubMed1994

SPECT images of technetium-99m-ethyl cysteinate dimer in cerebrovascular diseases: comparison with other cerebral perfusion tracers and PET.

UNLABELLED: To assess the clinical role of 99mTc-ethyl cysteinate dimer (ECD) as a cerebral perfusion tracer, 10 patients with unilateral cerebral infarction were studied. METHODS: ECD SPECT images were compared with IMP and/or HMPAO SPECT in nine patients, seven in chronic phases and two in subacute phases. Five of these patients and one additional patient with chronic infarction received PET imaging in order to compare ECD distribution with quantitative regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2) images. RESULTS: In patients with chronic cerebral infarction, regression analysis showed excellent correlation between ECD and IMP in the uptake ratio of lesions-to-nonaffected cortices (r = 0.91). In two cases of subacute infarction, decreased uptake of ECD was observed in the area of "luxury perfusion," which showed elevated or preserved rCBF with diminished rCMRO2. On visual analysis, ECD image contrast was less prominent compared to that of IMP, but contrast was better than that of HMPAO. CONCLUSIONS: ECD uptake showed a curvilinear relationship against rCBF, suggesting flow-limited uptake in a high flow range. ECD is a clinically useful cerebral perfusion tracer with distinct characteristics when compared with other available agents.

Adult↗

PubMed1993

Lack of prolonged cerebral blood flow change after transcranial magnetic stimulation.

To study the physiological changes in the human brain induced by transcranial magnetic stimulation (TMS), we measured cerebral blood flow (CBF) before and after TMS in 3 healthy volunteers with positron emission tomography (PET). The intersecting point of the figure-of-eight coil was positioned at C3. TMS was delivered 20-32 times at maximum intensity. CBF measured at 50 sec after the termination of TMS showed no significant change in the cerebral cortex corresponding to C3 or any other area. This finding indicates that the hemodynamic change in the brain induced by TMS, if any, lasts only for a short period.

Adult↗

PubMed1993

Both primary motor cortex and supplementary motor area play an important role in complex finger movement.

In order to clarify the roles played by the primary motor cortex and the supplementary motor area in the execution of complex sequential and simple repetitive finger movements, regional cerebral blood flow (rCBF) was measured with PET using 15O-labelled water in five normal subjects. The PET data of each individual subject co-registered to his own MRI, was analysed. Compared with the resting condition, the mean rCBF was markedly increased in the contralateral sensorimotor cortex (M1-S1) and moderately increased in the contralateral cingulate gyrus and putamen in both the simple and complex motor tasks. During the complex motor task, in addition to the above, the mean rCBF was markedly increased in the supplementary motor area and the contralateral premotor area, and moderately increased in the ipsilateral M1-S1 and cerebellum. In the supplementary motor area, there was a moderate rCBF increase also during the simple task. However, comparison of the mean rCBF increase against the resting condition between the two tasks revealed a greater increase during the complex task than in the other only in the supplementary motor area and the ipsilateral M1-S1. Thus, in agreement with our previous electrophysiological findings, not only the supplementary motor area but also the M1-S1 seems to play an important role in the execution of complex sequential finger movements.

Adult↗

PubMed1993

Spinal epidural abscess: evaluation with gadolinium-enhanced MR imaging.

Magnetic resonance (MR) imaging with gadopentetate dimeglumine was performed in 25 patients with spinal epidural abscess (SEA). Seventeen of 25 patients underwent follow-up MR imaging. The studies were retrospectively reviewed. In 20 patients, diskitis was the primary infectious foci; however, five patients developed diffuse SEA without diskitis. The two most common MR appearances were (a) homogeneous or heterogeneous enhancement of the solid portion of the SEA and (b) thin or thick enhancement around the liquefied collections of pus. Dural enhancement was frequently seen in patients with lengthy vertebral involvement of SEA. Engorgement of the epidural venous plexus or basivertebral veins was occasionally observed. The changes in abscess size noted on follow-up studies correlated well with clinical improvement or deterioration in most patients. Persistent contrast enhancement, however, was frequently noted at the site of diskitis, osteomyelitis, or surgical drainage sites despite clinical improvement. Careful correlation of MR imaging findings with clinical findings and laboratory data is important in predicting prognosis for these patients.

Abscess↗

PubMed1993

[99mTc-HMPAO SPECT in the brain death--a case report].

Brain single photon emission computed tomography (SPECT) with 99mTc-d,l-hexamethyl-propyleneamine oxime (HMPAO) was performed twice in a 78-year-old man clinically diagnosed as brain death according to the standard criteria of the Japanese Ministry of Welfare. The first brain SPECT demonstrated the tracer accumulation in the brain, indicating preserved cerebral blood flow. The second brain SPECT performed 3 days later revealed cessation of the blood flow. In patients with preserved cerebral blood flow, the diagnosis of brain death cannot be made, even if they meet the existing criteria, because previous report noted the recovery in some of those patients. Brain perfusion SPECT plays an important role as a confirmatory test for the diagnosis of the brain death.

Aged↗

PubMed1993

PET and the autoradiographic method with continuous inhalation of oxygen-15-gas: theoretical analysis and comparison with conventional steady-state methods.

The steady-state method using 15O gas inhalation and positron emission tomography (PET) is a simple and practical way of imaging cerebral blood flow (CBF) and oxygen metabolism. Several disadvantages do exist, however, including prolonged examination time, requirement of steady-state and a large tissue heterogeneity effect. To avoid the drawbacks of the steady-state method but to preserve its simplicity, we applied the PET/autoradiographic method to the build-up phase during the continuous inhalation of 15O-gas with intermittent arterial sampling. A simulation study was performed to determine the optimal scanning period, evaluate the delay and dispersion effect of the input function and estimate the tissue heterogeneity effect. To assess the clinical feasibility of the proposed technique for the study of oxygen metabolism, sequential measurements with this method and the conventional steady-state method were performed in eight patients. The simulation study showed that a 5-min scan started 3 min after the commencement of 15O-gas inhalation was optimal. With this method, the delay and dispersion effect on CBF was the same as that of the conventional steady-state method, but the tissue heterogeneity effect was reduced. In eight patients, CBF values calculated by this method showed time dependency and were slightly higher than those obtained by the steady-state method. The oxygen extraction fraction showed no significant time dependency and was well correlated with that obtained by the steady-state method. We conclude that the proposed method is a simple and acceptable alternative to the conventional steady-state method.

Administration, Inhalation↗

PubMed1992

Myocardial oxidative metabolism in normal subjects in fasting, glucose loading and dobutamine infusion states.

Experimental studies indicated the clearance rate constant of 11C-acetate as an index of regional myocardial oxygen consumption. To assess the response of the clearance rate from the left ventricular (LV) myocardium to the change in plasma substrate levels and to the increase in the cardiac work load in normal subjects, a total of 18 dynamic positron emission tomographic studies were performed at rest in the fasting state (control) (n = 7), after oral glucose administration (n = 4), and during dobutamine infusion (n = 7) in 7 normal volunteers. The clearance rate constant (Kmono) was similar in the control (0.065 +/- 0.017 min-1) and glucose loading states (0.059 +/- 0.008 min-1), whereas a significant increase in Kmono was observed during dobutamine infusion (0.106 +/- 0.018 min-1) (p < 0.01) in relation to the increase in the pressure-rate product with a correlation coefficient of 0.873 (p < 0.01). When the LV myocardium was divided into 6 segments, there were no significant differences among the segments in Kmono values in any condition. These normal responses should be valuable for assessing oxidative metabolic reserve and regional changes in oxidative metabolism in patients with coronary artery disease.

Adult↗

PubMed1992

[Transcatheter arterial infusion of adriamycin-lipiodol suspension to patients with metastatic liver tumor].

Adriamycin-Lipiodol suspension was administered to 44 patients with metastatic liver tumor using the transcatheter arterial infusion method. The result revealed 23% in the over all effect (partial response or more) of the therapy which was evaluated by comparing the CT images of the tumor, 47% in the 25% or more of the decrease of the tumor, and 65%, very effective in the decrease of the smaller tumor (less than 50 cm2). Except for a case of hepatic subcapsular hematoma after the infusion of Adriamycin-Lipiodol suspension, minor complications were experienced such as abdominal pain, slight fever, and so on. No serious exacerbation in liver function test and white blood cell count was noted.

Adult↗