Measurement and imaging of cerebral blood flow with stable xenon and computed tomography using modified least-squares analysis

Studies of stable xenon CT CBF technique with a newly developed closed system inhalator are reported. The patient inhales 30% of xenon for six minutes using a closed system(XETRON 3) while a series of CT scans is obtained using a Somaton DR 3 CT scanner. Endtidal xenon concentration is measured using a xenon monitor (AZ-723-XS), and CBF is calculated with Siemens medical CT CBF imaging software. The software uses Koeppe's mocified nonlinear least-squares analysis for calculation of f and k in Kety-Schmidt's equation. The scan slice level was selected about 5 cm above and parallel to orbitomeatal line, showing the pineal body and both glomus of the choroid plexus. CBF was evaluated in the region of interest corresponding to anatomical structure. Ten cases were studied including five normal adults, three cases of headache, one of small acoustic neurinoma and one of hemifacial spasm. There were seven males and three females, with ages ranging from 25 to 59 years old and averaging 43. In this system, normal averaging CBF (ml/100g/min) of left and right hemisphere was 52.0±9.0 and 51.1±7.4, respectively. The results are reasonable and this technique has the potential for broad utilization as a cheap, less-invasive three dimensional method of clinical examination for the evaluation of brain disorders.