Abstract:Regional Cerebral Blood Flow by ™Xenon Inhalation

Regional cerebral blood flow measurements were made in normal right-handed subjects by the 133 xenon inhalation method at rest and during movement of either hand. Left hand movement evoked a prominent focal flow increase in the right hemisphere in the Rolandic region. During right hand movement, there was a smaller and not statistically significant increase in left hemisphere Rolandic region. This suggests that more effort is required of right-handed subjects to move the left hand than the right, or that motor organization differs for left and right hand movements. Of several flow indices tested, there was little difference among gray matter flow rate, the product of gray matter flow and relative weight, the mean regional flow, and the initial slope index, all reflecting the flow changes with nearly equal sensitivity. The gray matter weight and fractional flow did not change consistently during hand movement.

Values of total cerebral blood flow in man measured by the indicator dilution method are compared with values of total internal jugular venous flow measured by the thermal dilution method. Except in the case of an extremely labile cerebral hemodynamic state, the results agree within the accuracy of the two methods, suggesting that for the supine patient total internal jugular venous flow provides a good index of total cerebral flow. The relatively short measurement time associated with nondiffusible indicators (dye or thermal dilution) facilitates detection of transient changes in total CBF or differential jugular flow that would tend to be averaged out with diffusible indicator methods. A mathematical analysis of the potential errors in the computation of total flow using the average of bilateral jugular venous dilution curves from a unilateral internal carotid injection is presented. This error can be partially corrected if the ratio of flow in one internal jugular to total flow is known. An analysis of potential computational errors under nonsteady state flow conditions (change in flow during the period between alternate carotid injections) is presented. Such flow changes can effect substantial errors in the computation of individual hemispheric or internal jugular flow and smaller errors in the computation of total flow.

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