Measurement of cerebral blood flow by X-ray computed tomography with a short inhalation of low-dose stable xenon

A less invasive technique has developed for measurement and mapping of cerebral blood flow (CBF) and brain/blood partition coefficient (λ) by xenon computed tomography (Xe-CT). Six minutes inhalation of 30% xenon had no influence on electroencephalography in normal adults, and head motion was seen in only 2.6% of clinical 310 cases. The cerebral xenon enhancement data were utilized in order to calculate CBF and CBF/λ ratio (k), using multivaluable analysis. This analysis method is a modified least-squares search by Koeppe, that does not use so called 'curve-fitting'. CBF and k values were calculated under unsaturation of brain with xenon. And λ was estimated as a ratio of CBF/k. In this analysis method, 'curve-fitting' was not needed, so this analysis method made it able to treat respiratory endtidal xenon data, which are inadequate to an exponential curve-fitting because of irregular respiration, with a linear interpolation method. A signal to noise ratio of increment in Hounsfield number of brain, should be as low as 30% xenon. But with smoothing of sampled date of intracerebral xenon, reasonable and reliable values of CBF and λ were obtained. And also high resolution between white matter and grey matter was obtained. Two dimensional Gauss function was used for smoothing. Also in clinical application, our new technique brought out many useful findings, these could not be obtained by X-ray CT or angiography alone, especially on ischemic cerebral vascular disease. (author)