Estimation of Organ Activity using Four Different Methods of Background Correction in Conjugate View Method

Abstract

To make an accurate estimation of the uptake of radioactivity in an organ using the conjugate view method, corrections of physical factors, such as background activity, scatter, and attenuation are needed. The aim of this study was to evaluate the accuracy of four different methods for background correction in activity quantification of the heart in myocardial perfusion scans. The organ activity was calculated using the conjugate view method. A number of 22 healthy volunteers were injected with 17-19 mCi of (99m)Tc-methoxy-isobutyl-isonitrile (MIBI) at rest or during exercise. Images were obtained by a dual-headed gamma camera. Four methods for background correction were applied: (1) Conventional correction (referred to as the Gates' method), (2) Buijs method, (3) BgdA subtraction, (4) BgdB subtraction. To evaluate the accuracy of these methods, the results of the calculations using the above-mentioned methods were compared with the reference results. The calculated uptake in the heart using conventional method, Buijs method, BgdA subtraction, and BgdB subtraction methods was 1.4 +/- 0.7 (P < 0.05), 2.6 +/- 0.6 (P < 0.05), 1.3 +/- 0.5 (P < 0.05), and 0.8 +/- 0.3 (P < 0.05) of injected dose (I.D) at rest and 1.8 +/- 0.6 (P > 0.05), 3.1 +/- 0.8 (P > 0.05), 1.9 +/- 0.8 (P < 0.05), and 1.2 +/- 0.5 (P < 0.05) of I.D, during exercise. The mean estimated myocardial uptake of (99m)Tc-MIBI was dependent on the correction method used. Comparison among the four different methods of background activity correction applied in this study showed that the Buijs method was the most suitable method for background correction in myocardial perfusion scan.