Quantitation of myocardial ^99mTc-HMDP uptake with new SPECT/CT Cadmium zinc telluride (CZT) camera in patients with transthyretin-related cardiac amyloidosis: ready for clinical use?

Objectives: Cardiac uptake of 99mTc-HMDP is widely used to evaluate cardiac transthyretin-related amyloidosis (ATTR). SUV may be calculated using a new whole body CZT SPECT/CT camera (DNM 670CZT). Our aim was to investigate the feasibility of assessing cardiac 99mTc-HMDP uptake using SUVs with new SPECT/CT CZT gamma-camera.

Methods: SUV measurements were calibrated using a conventional cylindrical SUV phantom. Seven patients (7 men, mean age: 78 ± 10 years) with cardiac ATTR underwent a conventional 99mTc-HMDP planar imaging and a thoracic SPECT/CT using a DNM 670CZT. Perugini score was estimated by two experimented physicians. A control group consisted of 7 patients who underwent a thoracic 99mTc-HMDP SPECT/CT as a routine examination. Acquisition parameters were: 60 projections over 360°, 10 sec/projection. All images were reconstructed using OSEM. HMDP-SUVmax (mg/L) were calculated in a cardiac VOI encompassing the whole left ventricle and in a cubic VOI placed in the right lung using commercially available program (Q-volumetrix, GE Healthcare). A heart-to-lung SUVmax ratio (HLR) was also calculated.

Results: Injected dose of 99mTc-HMDP were similar in ATTR (576±157 MBq) and control (579±75 MBq, p=ns). All ATTR patients had a Perugini score ≥ 2 an and demonstrated an increased cardiac HMDP-SUVmax (12.3 ± 3.2 mg/L) vs. controls (2,3 ± 0.7, p<0.0001). HLR were significantly higher in the ATTR group (11.12 ± 2.5 vs. 3,2 ± 1.2, p<0.001). Conclusion: This study demonstrated the feasibility of 99mTc-HMDP SUVmax measurement using a new whole body SPECT/CT CZT camera in patients with cardiac ATTR.