Dual-Gated Motion-Frozen Cardiac PET with Flurpiridaz F18

A novel PET radiotracer, flurpiridaz F-18, has undergone Phase II clinical trial evaluation as a high-resolution PET cardiac perfusion imaging agent. In a subgroup of patients imaged with this agent, we assessed the feasibility and benefit of simultaneous correction of respiratory and cardiac motion.

METHODS: In 16 patients, PET imaging was performed on a 4-ring Siemens Biograph-64 in dual cardiac and respiratory gating mode. Four sets of data were reconstructed with high-definition reconstruction (HD•PET): (i) ungated and (ii) 8-bin ECG-gated images using 5-min acquisition, (iii) optimal respiratory gating (ORG)-as developed for oncological imaging- using a narrow range of breathing amplitude around end-expiration level with 35% of the counts in a 7-min acquisition, and (iv) 4-bin respiratory-gated and 8-bin ECG-gated images (32 bins in total) using the 7-min acquisition (dual-gating, using all data). Motion-frozen (MF) registration algorithms were applied to ECG-gated and dual-gated data, creating cardiac MF and dual MF images. We computed wall thickness, wall/cavity contrast and contrast-to-noise ratio (CNR) for standard, ORG, cardiac MF and dual-MF images to assess image quality.

RESULTS: The wall/cavity contrast was similar for ungated (9.3±2.9), ORG (9.5±3.2) and improved for cardiac MF (10.8±3.6) and for dual MF images (14.8±8.0) (p < 0.05). CNR was 22.2±9.1 with ungated, 24.7±12.2 with ORG, 35.5±12.8 with cardiac MF, and 42.0±13.2 with dual MF images (all p < 0.05). The wall thickness was significantly decreased (p < 0.05) with dual MF (11.6±1.9 mm) compared to ungated (13.9±2.8 mm), ORG (13.1±2.9 mm) and cardiac MF images (12.1±2.7 mm).

CONCLUSION: Dual (respiratory/cardiac) gated perfusion imaging with flurpiridaz F 18 is feasible and improves image resolution, contrast, and contrast-to-noise ratio when motion-frozen registration methods are applied.