Monitoring of Transient Central Nervous System Postirradiation Effects by 133Xe Inhalation Regional Cerebral Blood Flow Measurements

The early transient postirradiation effects in the central nervous system are well known; however, no specific means of objective follow-up have been devised. The xenon (133Xe) inhalation technique for measurement of regional cerebral blood flow (rCBF) is easily reproducible. Serial rCBF measurements corresponding to the clinical presentation and course of the early postirradiation syndrome have not been previously reported. It is our belief that the global decline in rCBF identified in these patients represents a generalized metabolic derangement induced by whole brain irradiation rather than primary vascular changes. A distinction between tumor recurrence and the early transient postirradiation effects can be made utilizing this technique. It also provides a reproducible monitor of the clinical and metabolic impact of radiotherapy for brain tumors. A series of seven such patients is presented with appropriate case histories and graphic representations of the serial rCBF measurements.