Development of longitudinal PET studies for experimental animal models

Liefaard, Lia C.; Ploeger, Bart; Molthoff, Carla F. M.; Boellaard, Ronald; Jong, Hugo W. A. M. de; Lammertsma, Adriaan A.; Danhof, Meindert; Voskuyl, Rob A.

doi:10.1038/sj.jcbfm.9591524.0602

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“…The HRRT-S has high spatial resolution, but its count rate performance is limited due to dead time losses and data overrun problems for activities in the FOV exceeding 75 MBq. Although in general high activities are not used in dynamic small animal scans due to low specific activities of the radiopharmaceuticals, they may be required for full saturation studies (Liefaard et al 2003), or when multiple animals are scanned simultaneously. Although dose may be lowered in these latter studies, this would result in higher noise levels or longer scan times.…”

Section: Introductionmentioning

confidence: 99%

Use of an in-field-of-view shield to improve count rate performance of the single crystal layer high-resolution research tomograph PET scanner for small animal brain scans

et al. 2003

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The count rate performance of the single LSO crystal layer high-resolution research tomograph (HRRT-S) PET scanner is limited by the processing speed of its electronics. Therefore, the feasibility of using an in-field-of-view (in-FOV) shield to improve the noise equivalent count rates (NECR) for small animal brain studies was investigated. The in-FOV shield consists of a lead tube of 12 cm length, 6 cm inner diameter and 9 mm wall thickness. It is large enough to shield the activity in the body of a rat or mouse. First, the effect of this shield on NECR was studied. Secondly, a number of experiments were performed to assess the effects of the shield on the accuracy of transmission scan data and, next, on reconstructed activity distribution in the brain. For activities below 150 MBq NECR improved only by 5-10%. For higher activities NECR maxima of 1.2E4 cps at 200 MBq and 2.2E4 cps at 370 MBq were found without and with shield, respectively. Listmode data taken without shield, however, were corrupted for activities above 75 MBq due to data overrun problems (time tag losses) of the electronics. When the shield was used data overrun was avoided up to activities of 150 MBq. For the unshielded part of the phantom, transmission scan data were the same with and without shield. The estimated scatter contribution was approximately 8.5% without and 5.5% with shield. Reconstructed emission data showed a difference up to 5% in the unshielded part of the phantom at 5 mm or more from the edge of the shielding. Of this 5% about 3% results from the difference in the uncorrected scatter contribution. In conclusion, an in-FOV shield can be used successfully in an HRRT PET scanner to improve NECR and accuracy of small animal brain studies. The latter is especially important when high activities are required for tracers with low brain uptake or when multiple animals are scanned simultaneously.

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Section: Introductionmentioning

confidence: 99%