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

Abstract

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.

Monitoring of Tumor Growth and Post‐Irradiation Recurrence in a Diffuse Intrinsic Pontine Glioma Mouse Model

“…FLT (3′‐deoxy‐3′‐[ 18 F]fluorothymidine) was synthesized according to an earlier described method (22, 27). PET scans were acquired under inhalation anesthesia (mixture of 5% isoflurane: 95% oxygen) and performed, as previously described, using a double lutetium oxyorthosilicate (LSO)‐layer High Resolution Research Tomograph (HRRT; CTI, Knoxville, TN, USA) (3, 7).…”

Performance evaluation of the ECAT HRRT: an LSO-LYSO double layer high resolution, high sensitivity scanner

“…The many technical innovations used in the scanner and the leading role it is expected to play in future PET brain research justifies publication of the performance of the commercial HRRT. Although specific elements of the performance of mainly the prototype HRRTs have been reported previously (Boellaard et al 2003a, 2003b, Eriksson et al 2002, no study has yet described the complete performance of the commercial HRRT. In order to make sure that all aspects in the scanner performance are included and to make a comparison with other scanners possible, the standardized NEMA protocols were taken as a basis.…”

Development of a flexible end-shield using tungsten curtains for 3D PET

“…However, the shield decreases the diameter of the patient port of the PET scanner and can be only used for brain study. The other solution is the use of the body shield [3][4][5]. Although the body shield could be used for the whole body scanning, it needs some modifications on the bed.…”