EFFECTS OF TIME-DELAY IN CARDIAC BLOOD-FLOW MEASUREMENTS BY BOLUS (H2O)-O-15

Myocardial blood flow (rMBF) can be measured using dynamic positron em ission tomography (PET) and bolus injection of H-2 O-15. Recent studie s indicate that large errors in the estimates of flea ((f) over cap) c an be produced by time shifts between the true arterial input function and the measured input function [A(t)]. We have investigated this phe nomenon further using A(t) derived from patient data, and using simula ted myocardial time activity curves [M(t)]. We found that the judiciou s choice of scan parameters and region of interest (ROI) placement, th ese errors can be greatly reduced, In particular, when A(t) is measure d from the left ventricular (LV) cavity, the bias in (f) over cap is n egligible over a wide range of circumstances, However, when A(t) is no t measured from the LV cavity, the bias in dow can be large for short scans (<2 min) or low flow values (f < 0.4 ml/g/min). We show that the bias is primarily due to the spillover term in the model that is most commonly used to compute rMBF and suggest some correction methods. We conclude that it is possible to avoid errors in estimates of flow due to time delay.