Differences in early-phase tracer distribution in lung between 11C-acetate and 13N-ammonia.
OBJECTIVE
N-ammonia and C-acetate are well-known tracers useful for the measurement of myocardial blood flow. Some studies reported that the measurement of C-acetate showed better statistical quality than that with N-ammonia. To evaluate this difference, we focused on the early-phase tracer kinetics in blood and lung. The tracer kinetics in the myocardium, arterial blood, venous blood, and lung were compared between these two tracers.


METHODS
Twelve patients were studied. Dynamic positron emission tomography was performed with C-acetate and N-ammonia within a 1-week period. The time activity curves (TACs) of the myocardium, arterial blood, and lung were calculated. The TACs normalized to the peak activity of right ventricle blood (normalized TAC) were also generated.


RESULTS
The area under the curve of each TAC was calculated. Lung activity tended to be higher when assessed with N-ammonia. The area under the curve of the lung was larger with N-ammonia than with C-acetate both with the original TAC (478+/-232 vs. 248+/-87 MBq s/ml, P<0.001) and the normalized TAC (47.1+/-17.9 vs. 22.8+/-6.9 ratio x s, P<0.001).


CONCLUSIONS
N-ammonia and C-acetate showed strikingly different early-phase tracer distribution in the lung. This difference may affect myocardial blood flow measurement, which largely depends on the early-phase image quality.
Kudo
Takashi
T
Biomedical Imaging Research Center, University of Fukui, Fukui, Japan. tkudo@u-fukui.ac.jp
Hata
Tatsuhiko
T
Kagawa
Shinya
S
Kishibe
Yoshihiko
Y
Iwasaki
Jinei
J
Okazawa
Hidehiko
H
D000085:Acetates; D000368:Aged; D000369:Aged, 80 and over; D000641:Ammonia; D002250:Carbon Radioisotopes; D003331:Coronary Vessels / Q000000981:diagnostic imaging; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008168:Lung / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009590:Nitrogen Radioisotopes; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D014018:Tissue Distribution
D000085:Acetates; D002250:Carbon Radioisotopes; D009590:Nitrogen Radioisotopes; D019275:Radiopharmaceuticals; D000641:Ammonia