The construction and use of nomograms for cerebral blood flow calculation using a 133Xe inhalation technique

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Abstract
Measurement of human cerebral blood flow (CBF) using a 133Xe inhalation technique requires monitoring the clearance rate of the radioisotope from the head using extremely situated detectors and also from arterial blood using a detector to monitor the expired air activity. The end-tidal concentration function is assumed to be proportional to the arterial concentration function and must be deconvoluted from the clearance functions obtained from the head to enable CBF to be calculated. A digital computer is generally considered to be essential for this. A procedure using 3-dimensional nomograms is derived and tested. Results obtained using the nomograms do not differ significantly from results obtained using a full deconvolution procedure, and so it is not essential to use a computer to calculate CBF by the inhalation technique.