Time-reduction for simultaneous dual isotope lung scintigraphy using 3D-ring CZT SPECT/CT.

Introduction: Lung scintigraphy has still multiple indications such as pulmonary embolism diagnosis, follow-up of thromboembolic disease, or even right-left shunt. SPECT perfusion and ventilation acquisitions are now mandatory, but due to their pulmonary pathologies, some patients may have trouble to tolerate the relatively long examination duration. The StarGuide 3D-ring CZT-camera (GE Healthcare, Haifa, Israel) is equipped with 12 swiveling high-resolution CZT detectors and a CT in a hybrid system and allows simultaneous dual isotope acquisitions. In this preliminary work, we visually and quantitatively compared full-time and time-reduced lung SPECT perfusion and ventilation acquisitions.

Methods: We conducted a retrospective, single-center, comparative (with intra-patient comparisons) study. Patients underwent a 10-minutes acquisition on the new StarGuide CZT system (default protocol), after mean injection of 185.7 MBq 18.7 99mTc-labeled human albumin macroaggregates, and inhalation of 81mKrypton. Using list-mode, we retrospectively reframed patients’ data to acquisitions lasting for 5 and 7 minutes. Visual and quantitative comparison (QLung software, Xeleris, GE Healthcare, Haifa Israel) were performed. The primary outcome was the comparison of quotient analysis mismatch between 10-, 7-, and 5-minutes acquisitions. Secondary outcomes included the visual comparison and quotient analysis mismatch comparisons between 10 and 5 minutes acquisitions for perfusion and ventilation.

Results: Between October and December 2021, 20 patients were included, 13 women, 7 men,mean age 71 Y (33-94), mean BMI 27.7 kg/m2 (18-42). Mean Quotient Analysis Mismatch between perfusion and ventilation was 12% 18.4. There was no-significant difference between each acquisition duration with an intra-class correlation coefficient r of 0.996 between 10- and 7-minutes mismatch (p<0.0001), and r = 0.993 between 10- and 5- minutes mismatch (p<0.0001). Visual comparison showed no difference and overall image quality remained similar. Using the mismatch quotient analysis algorithm, mean difference between 10 and 5 minutes acquisitions was 0.000% 0.001 for perfusion, and 0.005% 0.045 for ventilation.

Conclusions: Our preliminary results indicate that the use of StarGuide system should allow time reduction for simultaneous dual-isotope lung scintigraphy up to 50% (scan time of 5 minutes) without visual difference or quantitative impact on perfusion-ventilation mismatch. These results should be confirmed on a larger scale.