Title :
An optimization of reconstruction parameters and investigation into the impact of photon scatter in 67Ga SPECT
Author :
Farncombe, Troy H. ; Gifford, Howard C. ; Narayanan, Manoj V. ; Pretorius, P. Hendrik ; Bruyant, Philippe ; Gennert, Michael ; King, Michael A.
Author_Institution :
Dept. of Nucl. Med., Massachusetts Univ. Med. Center, Worcester, MA, USA
fDate :
10/1/2002 12:00:00 AM
Abstract :
During 67Ga citrate SPECT imaging, photon downscatter will occur from higher energy photons into lower energy acquisition windows thus possibly adversely affecting reconstructed image quality. With these additional scattered photons present in projection data, the effect of using more complex reconstruction strategies such as three-dimensional detector response compensation (3-D DRC) and attenuation correction (AC) is unclear. Using a combination of numerical channelized hotelling observers (CHO) and human localization receiver operating characteristics (LROC) studies it has been found that maximum lesion detectability occurs when projection data is reconstructed using two iterations of the rescaled block iterative (RBI) algorithm with both 3-D DRC and patient specific AC, followed by a postreconstruction low-pass 3-D Gaussian filtering with a FWHM of ≈1 cm. These parameters deviate from optimal reconstruction parameters for primary photon-only projection data which finds that maximum lesion detection occurs after 4 RBI iterations with the same 3-D DRC, AC, and postfiltering. As expected, it is also observed that decreased tumor detectability results when scattered photons are present in 67Ga projection data compared to primary photon only reconstructions (reducing maximum AL from 0.79 to 0.58). This decrease has been found to be statistically significant in both human LROC and numerical observer studies, suggesting the need for scatter compensation during 67Ga citrate imaging.
Keywords :
single photon emission computed tomography; 67Ga SPECT; 67Ga citrate imaging; Ga; Gaussian filtering; attenuation correction; channelized hotelling observers; lesion detectability; localization receiver operating characteristics; photon downscatter; three-dimensional detector response compensation; Attenuation; Detectors; Electromagnetic scattering; Humans; Image quality; Image reconstruction; Lesions; Particle scattering; Scattering parameters; Single photon emission computed tomography;
Journal_Title :
Nuclear Science, IEEE Transactions on
DOI :
10.1109/TNS.2002.803786