SUV-SPECT for quantitation of myocardial 99m Tc-HMDP uptake with new SPECT/CT Cadmium zinc telluride (CZT) camera in patients treated by tafamidis for transthyretin-related cardiac amyloidosis: a new therapy managing tool?

1632 Objectives: Cardiac uptake of 99mTc-HMDP is widely used to evaluate cardiac transthyretin-related amyloidosis (ATTR). The aim of this preliminary report was to retrospectively evaluate the amyloid burden as the % of injected dose (%ID) or SUVmax using a new whole body CZT SPECT/CT camera (DNM 670CZT) before and after 6 months of treatment by tafamidis in two patients with ATTR. Methods: Two patients (2 men, of 85 et 90 years) with cardiac ATTR underwent a conventional 99mTc-HMDP planar imaging and a thoracic SPECT/CT using a DNM 670CZT (GE Healthcare) before and after 6 months of tafamidis. Perugini score was estimated by two experimented physicians. Acquisition parameters were: 60 projections over 360°, 10 sec/projection. All images were reconstructed using OSEM. HMDP-SUVmax (mg/L) and % of injected dose (%ID) were calculated in a cardiac VOI encompassing the whole left ventricle using commercially available program (Q-volumetrix, GE Healthcare). Results: Injected dose of 99mTc-HMDP were similar before and after treatment (656MBq vs 685MBq for patient 1 and 591MBq vs 609MBq for patient 2,). Patients had a Perugini score of 2 before and after tafamidis. Cardiac HMDP-SUVmax and %ID were lower after treatment: 13.1mg/L and 1.06% vs 17.1mg/L and 1.58% for patient 1 (ΔSUVMax and Δ%ID of -23% and -33% respectively), 8.65mg/L and 0.79% vs 14.3mg/L and 1.29% for patient 2 (ΔSUVMax and Δ%ID of -40% and -39% respectively). Conclusions: This preliminary study shown a decrease of quantitative parameters (99mTc-HMDP SUVmax, %ID) in two patients with cardiac ATTR treated by tafamidis during 6 months, while qualitative assessment (Perugini) remain unchanged. These new quantitative parameters may be useful tools in therapy management. Further patients are expected soon.