Correction method for end-tidal xenon concentration in CBF measurements with xenon-enhanced CT.
OBJECTIVE
The goal of this work is to show how variations in respiratory rate and tidal volume affect calculated cerebral blood flow (CBF) values on xenon-enhanced CT. In xenon-enhanced CT examination, the patient often takes shallow and rapid breaths. Thus, it is less likely that end-tidal xenon concentration reflects arterial xenon concentration, and appropriate correction measures should be taken for the end-distal respiratory data to obtain reliable CBF values.


METHODS
Preliminary breathing tests were performed using a lung phantom to determine the influence of respiratory volume and rate on end-tidal xenon concentration. Two xenon-enhanced CT studies were conducted of a healthy person with completely different respiratory manners between two studies. One was deep and slow respiration. The other was shallow and rapid respiration.


RESULTS
The lung phantom results prove that deep and slow respiration is essential for the end-tidal method. The results of xenon-enhanced CT studies of the same person show that the direct use of end-tidal data for shallow and rapid respiration leads to CBF values much lower than the actual values.


CONCLUSIONS
Differences in respiratory rate and tidal volume during xenon inhalation can significantly affect calculated CBF values on xenon-enhanced CT. With use of the correction methods described herein, these effects can be minimized. We have derived the end-tidal correction method on the assumption that a person's CBF values should be kept unchanged regardless of different respiratory manners.
Sase
S
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Anzai Medical Corporation, Tokyo, Japan.
D002560:Cerebrovascular Circulation / Q000502:physiology; D003287:Contrast Media; D006801:Humans; D008168:Lung / Q000502:physiology; D019047:Phantoms, Imaging; D012119:Respiration / Q000502:physiology; D013990:Tidal Volume; D014057:Tomography, X-Ray Computed; D014978:Xenon
D003287:Contrast Media; D014978:Xenon