Low-dose dual-isotope procedure planed for myocardial perfusion CZT-SPECT and assessed through a head-to-head comparison with a conventional single-isotope protocol

Purpose of the report: This study aimed at assessing an original low-dose dual-isotope procedure in which the abnormal stress Tc-99m Sestamibi SPECT is followed by rest Tl-201 SPECT, along with a head-to-head comparison with a single-isotope procedure.

Methods and results: One hundred two patients, referred for a low-dose stress-SPECT with Sestamibi (123 ± 20 MBq) on a CZT camera and for whom a rest Sestamibi SPECT was warranted, had an additional Tl-201 rest-SPECT (52 ± 5 MBq) between stress and rest Sestamibi SPECT recordings. Tl-201 images were processed for spill-over and scatter corrections, and uptake differences with stress Sestamibi SPECT were analyzed: (1) for rest acquisitions from Tl-201 (dual-isotope procedure) and from Sestamibi (single-isotope procedure) and (2) in segments for which a diagnosis of ischemia, infarct, or normal perfusion was achieved. Mean effective dose was 8.3 mSv for dual-isotope but would decrease to 5.7 mSv for an expected rate of 37% of patients for whom rest-SPECT is not warranted. After a further background correction of Tl-201 images, the rest-stress difference in myocardial uptake was equivalent between dual- and single-procedures for identifying ischemic segments (respective areas-under-curves: 0.83 ± 0.03 and 0.81 ± 0.03).

Conclusion: This original dual-isotope procedure provides acceptable radiation doses and consistent results, as compared with conventional single-isotope.