Hemisphere cross talk and signal overlapping in bilateral regional cerebral blood flow measurements using xenon 133

In bilateral regional cerebral blood flow measurements with xenon 133, Compton scatter and hemispheric cross talk obscure the regional resolution and increase the uncertainty of the results. In order to evaluate the effects of these extraregional signal sources on the calculation of regional gray matter blood flow, a computerized simulation procedure was developed. Using the depth-response of a rCBF detector in combination with a computer model of the human brain, it was possible to calculate the signal contributions from different regions in the brain. The results obtained show that large errors may be introduced in the calculation of regional gray matter blood flow when flow asymmetries exist.