WHOLE-BODY IMAGING OF TL-201 AFTER 6 DIFFERENT STRESS REGIMENS

There are a number of stress techniques in common use for Tl-201 myoca rdial imaging but few studies have been performed comparing the biodis tribution of Tl-201 in each case. Methods: We studied 36 normal patien ts after six different stress regimens by whole-body imaging, 40 min a fter Tl-201 injection. The stress regimens were exercise, dipyridamole , adenosine or dobutamine alone in standard doses and exercise combine d with a vasodilator (dipyridamole or adenosine). Results: Cardiac upt ake expressed as a percentage of whole body uptake was greater for the vasodilators compared with exercise (p < 0.005), and this difference was unaffected by combining either vasodilater with exercise. Intermed iate results were found with dobutamine. Heart-to-liver (p < 0.01) and abdomen (p < 0.05) ratios were greater for exercise compared with the vasodilators, and this difference was also unaffected by combining th e exercise with either vasodilator. Heart-to-lung ratios were highest with any stress involving exercise (p < 0.05). The heart-to-background ratios with dobutamine were similar to the vasodilators. Conclusion: Vasodilator infusion yields higher cardiac Tl-201 uptake than exercise , but when given alone this results in poor heart-to-background ratios . Combining either vasodilator with exercise maintains the high cardia c uptake, but substantially improves the heart-to-background ratios to levels similar to exercise alone. Dobutamine stress produces an inter mediate cardiac uptake, and heart-to-background ratios similar to the vasodilators. Therefore, optimal imaging conditions are obtained by st ress which combines a vasodilator with exercise.