Image contrast recovery coefficient (CRC) of a large ring PET scanner “macroPET” was studied with septa and without septa configuration by ac-quiring data from a laboratory made 35.7 cm square phantom filled with 18...Image contrast recovery coefficient (CRC) of a large ring PET scanner “macroPET” was studied with septa and without septa configuration by ac-quiring data from a laboratory made 35.7 cm square phantom filled with 18-F. Images were reconstructed with simple 2D filtered back projection using Hann, Hamming and Parsen filters with different cut-off frequencies aiming to investigate the influence of filter and cut-off frequency on image contrast with septa and without septa mode. Results indicate that the CRC, for both hot and cold lesions, is excellent for diameters ≥ 3 cm using cut-off frequencies > 0.4. For a 2 cm hot lesion CRC is around 0.8 to 0.9. CRC for 1 cm hot and cold lesions is ~0.3, as expected. There is surprisingly little difference between results with and without septa. For hot lesions, septa appear to improve CRC slightly, but for cold lesions CRC is slightly poorer using septa.展开更多
A nuclear miniPET camera was constructed with 2 bucket rings, each having 8 BGO detector modules for brain scanning. After calibration of the camera, an experimental investigation of sensitivity was carried out to eva...A nuclear miniPET camera was constructed with 2 bucket rings, each having 8 BGO detector modules for brain scanning. After calibration of the camera, an experimental investigation of sensitivity was carried out to evaluate the performance of this PET scanner. The characteristics of NECR were examined for comparisons of count rate considering the statistical noise due to scattered and random events. NECR performance was observed using 10 cm diameter phantom filled with 1 L water and 240 MBq of 18F. All data were acquired in 2D acquisition mode but without septa. Randoms were estimated by introducing delay into the coincidence circuit which was an extra 100 ns time delay. Multiples were recorded simultaneously with the prompt and delayed events. The true plus scattered coincidence events were calculated as the difference between prompt and random plus multiple events. After recording all the data, the noise equivalent count rate (NECR) was calculated and graphically presented. It is observed that NEC value is significantly lower than other similar scanners. Comparing the individual components of the count rate, a much higher randoms rate is observed for the camera because of the absence of any side shielding, so that out of field activity contributes significantly to the randoms rate and hence reduces the NECR value.展开更多
文摘Image contrast recovery coefficient (CRC) of a large ring PET scanner “macroPET” was studied with septa and without septa configuration by ac-quiring data from a laboratory made 35.7 cm square phantom filled with 18-F. Images were reconstructed with simple 2D filtered back projection using Hann, Hamming and Parsen filters with different cut-off frequencies aiming to investigate the influence of filter and cut-off frequency on image contrast with septa and without septa mode. Results indicate that the CRC, for both hot and cold lesions, is excellent for diameters ≥ 3 cm using cut-off frequencies > 0.4. For a 2 cm hot lesion CRC is around 0.8 to 0.9. CRC for 1 cm hot and cold lesions is ~0.3, as expected. There is surprisingly little difference between results with and without septa. For hot lesions, septa appear to improve CRC slightly, but for cold lesions CRC is slightly poorer using septa.
文摘A nuclear miniPET camera was constructed with 2 bucket rings, each having 8 BGO detector modules for brain scanning. After calibration of the camera, an experimental investigation of sensitivity was carried out to evaluate the performance of this PET scanner. The characteristics of NECR were examined for comparisons of count rate considering the statistical noise due to scattered and random events. NECR performance was observed using 10 cm diameter phantom filled with 1 L water and 240 MBq of 18F. All data were acquired in 2D acquisition mode but without septa. Randoms were estimated by introducing delay into the coincidence circuit which was an extra 100 ns time delay. Multiples were recorded simultaneously with the prompt and delayed events. The true plus scattered coincidence events were calculated as the difference between prompt and random plus multiple events. After recording all the data, the noise equivalent count rate (NECR) was calculated and graphically presented. It is observed that NEC value is significantly lower than other similar scanners. Comparing the individual components of the count rate, a much higher randoms rate is observed for the camera because of the absence of any side shielding, so that out of field activity contributes significantly to the randoms rate and hence reduces the NECR value.
