SIMULTANEOUS ASSESSMENT OF BLOOD FLOW AND FUNCTION USING GATED N-13 AMMONIA PET We determined whether simultaneous assessment of regional blood flow and function was feasible using low dose, short duration N-13 ammonia PET scans. Twelve patients with known coronary artery disease underwent a 5mCi - 5min ammonia dynamic scan immediately followed by a 10min ECG gated ammonia scan, and a 5mCi - 30min gated fluorodeoxyglucose (FDG) scan. Regional ammonia uptake, FDG uptake and blood flow values were measured. Regional cavity shortening was estimated both from the short gated ammonia scan and from the long gated FDG scan. Although the ammonia gated images had about 4 times less counts than the FDG gated images, there was a high correlation between cavity shortening measured from the 10min gated ammonia scans and from the 30min gated FDG scan (r=0.82). FDG uptake, ammonia uptake and blood flow values were all significantly decreased in regions with cavity shortening <4.5mm compared to regions with shortening >4.5mm regardless of whether shortening was measured from the short ammonia scan or from the long FDG scan. Cavity shortening measured by both gated FDG and ammonia was significantly different between viable and non-viable regions defined by FDG uptake. Both cavity shortening measurements were significantly higher in normal regions (defined by ammonia uptake) compared to abnormal and matched regions, and were also higher in normal regions compared to abnormal and mismatched regions. The ammonia shortening values had higher variability than the FDG shortening values. These data suggest that simultaneous assessment of regional blood flow and wall motion can be made using 15min - 5mCi ammonia imaging protocols, enabling the use of rapid, sequential and low dose ammonia scans to study blood flow and mechanical funciton under different physiologic conditions.
