Correlation of regional cerebral blood flow between Xe-CT and 133Xe-SPECT: validity of Xe-CT in evaluating rCBF

Stable xenon-enhanced computed tomography (Xe-CT), a relatively inexpensive addition of an inhalation system to the CT, has been a common method for the measurement of rCBF in recent years. Although the 133Xe clearance method has been accepted as a standard method since the 1970s, a comparative study of rCBF between Xe-CT and 133Xe-SPECT has not been reported. We studied the validity of Xe-CT for evaluating rCBF in comparison with 133Xe-SPECT. From May 1993 to December 1994, rCBF studies in 31 cases were performed using both methods within one month of each other. We evaluated rCBF of the unilateral cerebral hemisphere at a slice of OM + 80 mm level. Finally, Eleven cases were excluded from the analysis because of the existence of ventricle in the image and/or discrepancy in the clinical state between the two examinations. In the remaining 20 cases, there was a significant correlation of rCBF between Xe-CT (Y) and 133Xe-SPECT(X)(Y = 0.95X-1.7, r = 0.86, p < 0.001, n = 40). The results supported the usefulness of Xe-CT for the quantitative assessment of rCBF. As compared with SPECT, Xe-CT offers the advantages of much higher spatial resolution, allowing more precise reference of flow and anatomy, and providing quantitative information on rCBF in deeper regions of the brain.