ISSN:
1619-7089
Keywords:
Key words: Transport kinetics
;
Radionuclide imaging
;
Radioisotope dilution technique
;
Perfusion imagingIntroduction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract. Technetium-99m Q12 and 99mTc-sestamibi are cationic lipophilic myocardial perfusion imaging tracers. Because myocardium in areas of ischemia becomes acidotic, experiments were designed to differentiate the effects of myocardial perfusate pH on radiotracer extraction and retention independent of substrate availability. We hypothesized that 99mTc-Q12 and 99mTc-sestamibi single-pass uptake and retention would be unaffected by a modest reduction in coronary perfusate pH. Isolated rat hearts were perfused at constant flow with Krebs-Henseleit buffer enriched with bovine red blood cells (20%). The indicator dilution method was used to measure the maximum extraction (E max) and net extraction (E net) of thallium-201 and 99mTc-Q12 (n = 8) or 201Tl and 99mTc sestamibi (n = 7) during baseline perfusion (pH = 7.4), during acidemic (pH = 6.7) perfusion, and during a restitution period with normal perfusate (pH = 7.4). 201Tl E max (0.71±0.03) was greater than either 99mTc-Q12 or 99mTc-sestamibi E max (0.27±0.02 and 0.26±0.01 respectively, P〈0.0001). Acidemia significantly reduced 201Tl E max (0.65±0.03, P〈0.02) but not 99mTc-Q12 or 99mTc-sestamibi E max (0.25±0.02 and 0.24±0.02 respectively). During control perfusion E net of 201Tl was greater than that of 99mTc-Q12 at 3 and 5 min and greater than that of 99mTc-sestamibi at 3 min. 99mTc-Q12 E net was less than 99mTc-sestamibi E net at 3, 5, and 10 min. Acidemia decreased 201Tl and 99mTc-sestamibi E net at 3, 5, and 10 min but had no effect on 99mTc-Q12 E net. It is concluded that E max of 99mTc-Q12 is less than that of 201Tl but is not different from that of 99mTc-sestamibi. E net of 99mTc-Q12 is less than that of 99mTc-sestamibi.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002590050177
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