Impact of a Multiple Mice Holder on Quantitation of High-Throughput MicroPET Imaging With and Without Ct Attenuation Correction
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The aim of this study is to evaluate the impact of scanning multiple mice simultaneously on image quantitation, relative to single mouse scans on both a micro-positron emission tomography/computed tomography (microPET/CT) scanner (which utilizes CT-based attenuation correction to the PET reconstruction) and a dedicated microPET scanner using an inexpensive mouse holder “hotel.”
We developed a simple mouse holder made from common laboratory items that allows scanning multiple mice simultaneously. It is also compatible with different imaging modalities to allow multiple mice and multi-modality imaging. For this study, we used a radiotracer (64Cu-GB170) with a relatively long half-life (12.7 h), selected to allow scanning at times after tracer uptake reaches steady state. This also reduces the effect of decay between sequential imaging studies, although the standard decay corrections were performed. The imaging was also performed using a common tracer, 2-deoxy-2-[18 F]fluoro-d-glucose (FDG), although the faster decay and faster pharmacokinetics of FDG may introduce greater biological variations due to differences in injection-to-scan timing. We first scanned cylindrical mouse phantoms (50 ml tubes) both in a groups of four at a time (multiple mice mode) and then individually (single mouse mode), using microPET/CT and microPET scanners to validate the process. Then, we imaged a first set of four mice with subcutaneous tumors (C2C12Ras) in both single- and multiple-mice imaging modes. Later, a second set of four normal mice were injected with FDG and scanned 1 h post-injection. Immediately after completion of the scans, ex vivo biodistribution studies were performed on all animals to provide a “gold-standard” to compare quantitative values obtained from PET. A semi-automatic threshold-based region of interest tool was used to minimize operator variability during image analysis.
Phantom studies showed less than 4.5 % relative error difference between the single- and multiple-mice imaging modes of PET imaging with CT-based attenuation correction and 18.4 % without CT-based attenuation correction. In vivo animal studies (n = 4) showed <5 % (for 64Cu, p > 0.686) and <15 % (for FDG, p > 0.4 except for brain image data p = 0.029) relative mean difference with respect to percent injected dose per gram (%ID/gram) between the single- and multiple-mice microPET imaging mode when CT-based attenuation correction is performed. Without CT-based attenuation correction, we observed relative mean differences of about 11 % for 64Cu and 15 % for FDG.
Our results confirmed the potential use of a microPET/CT scanner for multiple mice simultaneous imaging without significant sacrifice in quantitative accuracy as well as in image quality. Thus, the use of the mouse “hotel” is an aid to increasing instrument throughput on small animal scanners with minimal loss of quantitative accuracy.
Key wordsImage quantitation MicroPET Attenuation correction High throughput Imaging Biodistribution
- 12.Hamilton CS, Ma Y, Smith SD, Benveniste H (2007) High resolution 3D in vivo mouse brain imaging at 9.4 T bruker MRI systemBioengineering Conference, 2007 NEBC '07 IEEE 33rd Annual Northeast, pp. 45-46.Google Scholar
- 13.Hong H, Yang Y, Cai W (2011) Imaging gene expression in live cells and tissues. Cold Spring Harbor Protoc: 354-365.Google Scholar
- 15.Pauux AL, Ong LC, Teh I, et. al. (2011) Comparison of imaging techniques to monitor tumor growth and cancer progression in living animals. Int J Mol Imaging doi:10.1155/2011/321538 .
- 18.Dazai J, Spring S, Cahill LS, Henkelman RM (2011) Multiple-mouse neuroanatomical magnetic resonance imaging. J Vis Exp: e2497.Google Scholar
- 22.Sheruma N, Peter LK, Wencke L, Steven R M (2006) Maximizing the useful field of view of the microPET: feasibility of imaging large animals, IEEE Nuclear Science Symposium Conference Record 1853-1856Google Scholar