Calculation of Variability in Myocardial Uptake of ^<99m>Tc-tetrofosmin at Exercise and Rest SPECT Images : Application to Hypertrophic Cardiomyopathy

Abstract

We examined whether or not it is better to use delayed myocardial SPECT images in determining the varability in myocardial uptake(ΔTF) of^<99m>Tc-tetrofosmin under the one-day protocol. We injected 370 MBq of ^<99m>Tc-tetrofosmin at peak exercise, and initial(TF1) and delayed(TF2) exercise SPECT images were acquired 30 min and 3 hr, respectively, after the injection. Then, 740 MBq of ^<99m>Tc-tetrofosmin was reinjected soon after TF2 acquisition, and rest SPECT images(TF3) were obtained 30 min later. Myocardial counts of TF1, TF2, and TF3 were defined as C1, C2, and C3, respectively, and ΔTF was determined by the following formula:ΔTF(A)=[{C1×R-(C3-C2')}/(C3-C2')]×100(%). ΔTF(B)=[{C1×R-(C3-C1')}/(C3-C1')]×100(%), where R is dose ratio, A is the procedure of imaging with delayed exercise SPECT, and B is the procedure of imaging without delayed exercise SPECT. The combination in which the delayed image was used better clari-fied the decreased uptake of ^<99m>Tc-tetrofosmin at the hypertrophied myocardium, and thus proved to by useful.