Thallium-201 for assessment of myocardial viability: Quantitative comparison of 24-hour redistribution imaging with imaging after reinjection at rest

Abstract

Redistribution thallium-201 imaging 2 to 4 h after exercise may be incomplete and therefore may be inadequate to fully assess myocardial variability. Late redistribution imaging 24 h after exercise has been proposed to overcome this limitation of thallium stress imaging. However, because of poor count density the image quality on these studies is often suboptimal. In the present study the diagnostic information on 24-h planar thallium redistribution images was compared with that on images obtained after a reinjection of thallium at rest. Eighty-four patients with a stress thallium-201 defect had delayed redistribution imaging after 2 to 4 h and 24 h later, and again after an injection of thallium at rest. Defect reversibility on 24-h redistribution images was compared quantitatively with that on images after injection of thallium at rest. The quality of thallium images at rest was consistently better than that of 24-h redistribution images. Poor quality studies occurred in 13% of 24-h redistribution images compared with 0.4% of the studies at rest. Significantly more defect reversibility was detected on images after the reinjection at rest. Of 41 patients who appeared to have a fixed defect at 2- to 4-h redistribution imaging, 11 (27%) had a reversible defect by 24-h redistribution imaging compared with 29 (71%) after thallium-201 reinjection. No clinical variables at the time of stress testing were predictive of late defect reversibility. It is concluded that in patients with fixed a thallium defect at 2 to 4 h after exercise, reimaging after a reinjection at rest provides better diagnostic information than does 24-h late redistribution imaging.

Persistent Thallium-201 Defect: Can Clinical, Electrocardiographic and Exercise Hemodynamic Variables Predict Defect Normalization with Reinjection?

“…This finding is consistent with previously published reports demonstrat ing a similar prevalence of Q waves among patients with normalized defects and those with fixed defects after rest 20IT1 reinjection [9], and the similar prevalence of Q waves in patients with reversible defects and those with fixed defects on late (24-hour) redistribution images stud ied by Yang et al [4], This finding is not unexpected since it is established that viability, reflected as regional FDG uptake, may be found in large myocardial regions associ ated with large Q waves [ 16. 17], Furthermore, Tillisch ct al.…”

Twenty-four-hour quantitative thallium imaging for predicting beneficial revascularization

“…Rest thallium injection after 24-h planar imaging showed 50 new reversible segments among 126 segments without redistribution on 24-h imaging [18]. These two studies suggested the superiority of reinjection methods to 24-h imaging.…”

“…However, significant proportion of fixed defects can be considered viable. Several reports have revealed that additional late imaging or reinjection shows thallium redistribution or fill-in in the areas of fixed defects with conventional stress and delayed images [4,6,8,10,[17][18][19]. Positron emission tomography has been found to show metabolic activity in the zone of fixed thallium defects [10,20,21].…”

Thallium-201 for Detection of Myocardial Viability: Comparison of Early Postexercise Reinjection and Imaging with 4 and 18–24 Hours Redistribution Imaging

“…Accordingly, in patients showing apparently irreversible defects at 3-4 h, the identification of viable myocardium may be enhanced by the acquisition of a third set of images obtained 8-24 h later which allows for a longer period of Tl redistribution [2][3][4]. Furthermore, previous studies [5,6] showed that a quantitative analysis using planar imaging techniques after Tl rest-RI improved the detection of viability and predicted the recovery of left ventricular function of coronary bypass surgery. At times, it is important to complete a study as quickly as possible because this maximizes patient turnover, increases patient comfort, and expedites the decision-making process.…”