Image noise analysis of a large ring PET scanner “macro PET” performed using two different phantoms, namely a Jaszczak SPECT phantom and a uniform cylindrical phantom. In the present work, simple 2D filtered back pr...Image noise analysis of a large ring PET scanner “macro PET” performed using two different phantoms, namely a Jaszczak SPECT phantom and a uniform cylindrical phantom. In the present work, simple 2D filtered back projection was used to reconstruct all the images, and in almost all the cases a Hamming filter of cutoff frequency 0.4 and a 256 by 256 matrix with zoom factors from 1 to 4 were used in order to investigate the imaging capabilities of the new scanner and the influence of filter and cut-off frequency on the filtered back projected images. Results indicate that 11.1 mm cold rod in the Jaszczak phantom images can consistently be seen. The Coefficient of variation (CV) results for Hann and Hamming filters are very similar and increase approximately in linear fashion with higher cutoff frequency. The value of CV for the Parsen filter is lower than the value for Hann and Hamming filters. It concludes that all filters with low cut off-frequency (0.6) would suppress image noise but decrease contrast.展开更多
High resolution (4 mm) tof PET-CT (positron emission tomography-computed tomography) from Philips of model Ingenuity TF is newly installed at Institute of Nuclear Medical Physics (INMP). 128 slice CT component incorpo...High resolution (4 mm) tof PET-CT (positron emission tomography-computed tomography) from Philips of model Ingenuity TF is newly installed at Institute of Nuclear Medical Physics (INMP). 128 slice CT component incorporated with PET provides comparatively lower dose than the 511 keV annihilation photons associated with positron decay from PET scan. So, for designing shielding in our PET-CT facility, only 511 keV annihilation photons energy has been considered. The main objective of this paper is to show what measures have been taken to protect patients, occupational workers as well as environment from PET-CT radiation hazard through a cost effective design that satisfy the national regulatory demand. In this paper, AAPM (American Associations of Physicists in Medicine) Task group 108 analysis for PET and PET-CT shielding requirements is followed for our PET-CT facility shielding design. From theoretical calculation as shielding requirement, 1.1 cm Pb thickness or, 13 cm concrete thicknesses are found. Practically, all walls and ceiling are of 30.48 cm (1 foot) thick made of concrete with density 2.35 gcm-3 for more safety. As x-ray from CT is not taken into account for shielding analysis, Bangladesh Atomic Energy Commission (BAEC) conducted an extensive radiation survey at controlled, supervised and public area for CT. The report that is found meets the national regulatory requirements.展开更多
文摘Image noise analysis of a large ring PET scanner “macro PET” performed using two different phantoms, namely a Jaszczak SPECT phantom and a uniform cylindrical phantom. In the present work, simple 2D filtered back projection was used to reconstruct all the images, and in almost all the cases a Hamming filter of cutoff frequency 0.4 and a 256 by 256 matrix with zoom factors from 1 to 4 were used in order to investigate the imaging capabilities of the new scanner and the influence of filter and cut-off frequency on the filtered back projected images. Results indicate that 11.1 mm cold rod in the Jaszczak phantom images can consistently be seen. The Coefficient of variation (CV) results for Hann and Hamming filters are very similar and increase approximately in linear fashion with higher cutoff frequency. The value of CV for the Parsen filter is lower than the value for Hann and Hamming filters. It concludes that all filters with low cut off-frequency (0.6) would suppress image noise but decrease contrast.
文摘High resolution (4 mm) tof PET-CT (positron emission tomography-computed tomography) from Philips of model Ingenuity TF is newly installed at Institute of Nuclear Medical Physics (INMP). 128 slice CT component incorporated with PET provides comparatively lower dose than the 511 keV annihilation photons associated with positron decay from PET scan. So, for designing shielding in our PET-CT facility, only 511 keV annihilation photons energy has been considered. The main objective of this paper is to show what measures have been taken to protect patients, occupational workers as well as environment from PET-CT radiation hazard through a cost effective design that satisfy the national regulatory demand. In this paper, AAPM (American Associations of Physicists in Medicine) Task group 108 analysis for PET and PET-CT shielding requirements is followed for our PET-CT facility shielding design. From theoretical calculation as shielding requirement, 1.1 cm Pb thickness or, 13 cm concrete thicknesses are found. Practically, all walls and ceiling are of 30.48 cm (1 foot) thick made of concrete with density 2.35 gcm-3 for more safety. As x-ray from CT is not taken into account for shielding analysis, Bangladesh Atomic Energy Commission (BAEC) conducted an extensive radiation survey at controlled, supervised and public area for CT. The report that is found meets the national regulatory requirements.
