Clinical impact of combination of scatter, attenuation correction, and depth-dependent resolution recovery for Tl-201 studies

A lack of specificity for myocardial perfusion imaging has been widely repo rted, mostly related to false-positive defects on the inferior wall. The ap plication of depth-dependent resolution recovery (RR), attenuation correcti on (AC) using external source devices, and scatter correction has been prop osed to resolve this pitfall. Methods: We studied the clinical benefit of d epth-dependent RR, nonuniform AC using a scanning line source, and scatter correction (photon energy recovery [PER]) compared with filtered backprojec tion alone. Eighty-two patients were included: 40 healthy volunteers with a low likelihood of coronary artery disease (control group) and 42 patients with proven right or circumflex coronary artery disease but without involve ment of the left anterior descending artery. Among these 82 patients, the i mages of 33 were also processed with PER. Results: RR did not alter the per formance of filtered backprojection alone. AC + RR greatly improved specifi city and the rate of normal (TI)-T-201 SPECT findings in the control popula tion (from 56% to 95% and from 53% to 100%, respectively) but significantly decreased sensitivity (from 92% to 54%). AC + RR generated a false anteroa pical defect in 21% of patients and reverse redistribution of the apex in 2 3%. AC + RR significantly decreased the extent of the stress defect (from 4 .09 to 3.21 segments, P < 0.003) and increased the perfusion score of the s tress defect (from 0.78 +/- 0.72 to 1.47 +/- 1.11, P < 0.00061). Moreover, AC + RR generated overcorrection on the inferior wall, leading to false est imation of viability for 11 of 15 patients with an old inferior myocardial scar without evidence of residual viability. PER decreased overcorrection o n the inferior wall, but without improving sensitivity. PER did not signifi cantly reduce the number of anteroapical false-positives or the number of a pical reverse distribution cases. Conclusion: AC + RR improved the specific ity and normalcy rate of (TI)-T-201 SPECT myocardial perfusion imaging but generated overcorrection on the inferior wall, leading to low sensitivity a nd to false evaluation of myocardial viability in 73% of the patients with inferior infarction. AC + RR also generated anteroapical artifacts. The add ition of scatter correction did not significantly reduce these drawbacks.