High throughput static and dynamic small animal imaging using clinical PET/CT: potential preclinical applications.

PURPOSE

The objective of the study was to evaluate state-of-the-art clinical PET/CT technology in performing static and dynamic imaging of several mice simultaneously.

METHODS

A mouse-sized phantom was imaged mimicking simultaneous imaging of three mice with computation of recovery coefficients (RCs) and spillover ratios (SORs). Fifteen mice harbouring abdominal or subcutaneous tumours were imaged on clinical PET/CT with point spread function (PSF) reconstruction after injection of [18F]fluorodeoxyglucose or [18F]fluorothymidine. Three of these mice were imaged alone and simultaneously at radial positions -5, 0 and 5 cm. The remaining 12 tumour-bearing mice were imaged in groups of 3 to establish the quantitative accuracy of PET data using ex vivo gamma counting as the reference. Finally, a dynamic scan was performed in three mice simultaneously after the injection of (68)Ga-ethylenediaminetetraacetic acid (EDTA).

RESULTS

For typical lesion sizes of 7-8 mm phantom experiments indicated RCs of 0.42 and 0.76 for ordered subsets expectation maximization (OSEM) and PSF reconstruction, respectively. For PSF reconstruction, SOR(air) and SOR(water) were 5.3 and 7.5%, respectively. A strong correlation (r (2) = 0.97, p < 0.0001) between quantitative data obtained in mice imaged alone and simultaneously in a group of three was found following PSF reconstruction. The correlation between ex vivo counting and PET/CT data was better with PSF reconstruction (r (2) = 0.98; slope = 0.89, p < 0.0001) than without (r (2) = 0.96; slope = 0.62, p < 0.001). Valid time-activity curves of the blood pool, kidneys and bladder could be derived from (68)Ga-EDTA dynamic acquisition.

CONCLUSION

New generation clinical PET/CT can be used for simultaneous imaging of multiple small animals in experiments requiring high throughput and where a dedicated small animal PET system is not available.