title: A Monte Carlo evaluation of three Compton camera absorbers

authors: Uche, Chibueze Zimuzo

subjects: Compton camera

abstract: We present a quantitative study on the performance of cadmium zinc telluride (CZT), thallium-doped sodium iodide (NaI(Tl)) and germanium (Ge) detectors as potential Compton camera absorbers. The GEANT4 toolkit was used to model the performance of these materials over the nuclear medicine energy range. CZT and Ge demonstrate the highest and lowest efficiencies respectively. Although the best spatial resolution was attained for Ge, its lowest ratio of single photoelectric to multiple interactions suggests that it is most prone to inter-pixel cross-talk. In contrast, CZT, which demonstrates the least positioning error due to multiple interactions, has a comparable spatial resolution with Ge. Therefore, we modelled a Compton camera system based on silicon (Si) and CZT as the scatterer and absorber respectively. The effects of the detector parameters of our proposed system on image resolution were evaluated and our results show good agreement with previous studies. Interestingly, spatial resolution which accounted for the least image degradation at 140.5 keV became the dominant degrading factor at 511 keV, indicating that the absorber parameters play some key roles at higher energies. The results of this study have validated the predictions by An et al. which state that the use of a higher energy gamma source together with reduction of the absorber segmentation to sub-millimetre could achieve the image resolution of 5 mm required in medical imaging.

text: A Monte Carlo evaluation of three Compton camera absorbers We present a quantitative study on the performance of cadmium zinc telluride (CZT), thallium-doped sodium iodide (NaI(Tl)) and germanium (Ge) detectors as potential Compton camera absorbers. The GEANT4 toolkit was used to model the performance of these materials over the nuclear medicine energy range. CZT and Ge demonstrate the highest and lowest efficiencies respectively. Although the best spatial resolution was attained for Ge, its lowest ratio of single photoelectric to multiple interactions suggests that it is most prone to inter-pixel cross-talk. In contrast, CZT, which demonstrates the least positioning error due to multiple interactions, has a comparable spatial resolution with Ge. Therefore, we modelled a Compton camera system based on silicon (Si) and CZT as the scatterer and absorber respectively. The effects of the detector parameters of our proposed system on image resolution were evaluated and our results show good agreement with previous studies. Interestingly, spatial resolution which accounted for the least image degradation at 140.5 keV became the dominant degrading factor at 511 keV, indicating that the absorber parameters play some key roles at higher energies. The results of this study have validated the predictions by An et al. which state that the use of a higher energy gamma source together with reduction of the absorber segmentation to sub-millimetre could achieve the image resolution of 5 mm required in medical imaging.

year: 2011

title: Excerpt from Pet

authors: Chidgey, Catherine

abstract: Catherine Chidgey has once again won the prestigious Jann Medlicott Acorn Prize, this time for her brilliant "classic in the making" novel The Axeman's Carnival. Now her thrilling new psychodrama looks set to grab more awards and is launching in the UK as Book of the Month. This excerpt from Pet gives you a taste of an author who is smoking hot right now.

text: Excerpt from Pet Catherine Chidgey has once again won the prestigious Jann Medlicott Acorn Prize, this time for her brilliant "classic in the making" novel The Axeman's Carnival. Now her thrilling new psychodrama looks set to grab more awards and is launching in the UK as Book of the Month. This excerpt from Pet gives you a taste of an author who is smoking hot right now.

year: 2023-06-01

title: E Ara Apanui

authors: Maxwell, Te Kahautu

abstract: E Ara Apanui recites the genealogical links between the Te Whakatōhea iwi and the host people of the Te Whānau a Apanui iwi. This new composition was performed by Ōpōtiki Mai Tawhiti at the Mātaatua Regional Kapa Haka Competition to qualify for Te Matatini 2013.

text: E Ara Apanui E Ara Apanui recites the genealogical links between the Te Whakatōhea iwi and the host people of the Te Whānau a Apanui iwi. This new composition was performed by Ōpōtiki Mai Tawhiti at the Mātaatua Regional Kapa Haka Competition to qualify for Te Matatini 2013.

year: 2012