Biomedical subjects

Keiichi Machida

Publications and source records attributed to Keiichi Machida.

3 recordsLinked to original sources

PubMed2003

[Comparison of cerebral blood flow with Xe-inhalation CT and perfusion CT].

Cerebral blood flow (ml/min/100g) (CBF) was detected by two methods, static xenon inhalation dynamic CT (Xe-CT) and perfusion CT, and a comparison of these two methods (Xe-CBF and perfusion CBF) was carried out in the same cases. Xe CT used 30% static xenon, 4 min wash-in, and 5 min wash-out, while perfusion CT was done by injecting 30 ml of non-ionic contrast medium at a rate of 9 ml/sec. Forty-eight patients underwent these examinations (30 serious cases and 18 mild). The correlation coefficients in the hemispheric area were r=0.713 (p<0.01) with Xe-CBF and perfusion CBF in mild cases and r=0.567 (p<0.01) in serious cases. The two CBF values were especially disparate in serious cases. The value for perfusion CBF was almost double that of Xe-CBF in these cases. Perfusion CT was a useful examination for the detection of CBF, but in serious cases, CBF needs to be determined by Xe-CT as well.

Administration, Inhalation↗

PubMed2002

[Method of injection of contrast medium for brain perfusion CT].

Perfusion computed tomography (CT) has great value for detecting stroke and evaluating blood flow in the brain. With perfusion CT, it is possible to obtain two absolute values, cerebral blood flow (CBF) (ml/min/100g) and cerebral blood volume (CBV) (%). In using this examination, the main problem is the method of iodine injection. The maximum slope of time-attenuation curve in organs must be reached before the peak enhancement time of the sagittal sinus. To solve this problem, we used a new method in which total injection volume is 30ml, and the rate of injection is 9ml/sec. The data acquisition time is one second for each scan, and the time interval is one second, for 20 scans in total. With this method, we can obtain reliable information on blood flow in the damaged brain. The most common examination used for the detection of brain blood flow is single-phased dynamic CT with Xe inhalation. However, the Xe inhalant examination is difficult to use in the routine clinical setting. Perfusion CT will be more useful for the detection of brain blood flow.

Blood Volume↗

PubMedDate not supplied

Quantitative cerebral blood flow calculation method using white matter lambda in xenon CT.

The objective of this work is to propose a quantitative cerebral blood flow (CBF) calculation method for xenon CT (Xe-CT) by logically estimating the time course change rate (rate constant) of the arterial xenon concentration from that of end-tidal xenon concentration. A single factor, gamma (gamma), which is considered to reflect the diffusing capacity of the lung for xenon, was introduced to correlate the end-tidal rate constant (Kend-tidal) with the arterial rate constant (Karterial). When an appropriate value is given to gamma, it is possible to calculate the arterial rate constant (calculated Karterial) from Kend-tidal. A procedure was developed to determine the gamma value utilizing the characteristics of white matter lambda (lambda). This procedure was applied to three healthy volunteers. The gamma gammaalues for the three subjects were consistent with those directly calculated from end-tidal and arterial (abdominal aorta) xenon data. Hemispheric CBF values with use of calculated Karterial (47.3 +/- 10.3 ml/100 g/min) were close to the reported normative values. We conclude this method could make current Xe-CT examinations substantially reliable and quantitative in measuring CBF.

Adult↗