TY - JOUR T1 - All-count reconstruction: Effects of energy band width JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1503 LP - 1503 VL - 50 IS - supplement 2 AU - Arkadiusz Sitek AU - Marie Foley Kijewski Y1 - 2009/05/01 UR - http://jnm.snmjournals.org/content/50/supplement_2/1503.abstract N2 - 1503 Objectives To quantify the effects of energy band width on estimation task performance using all-count reconstruction (ACR) in SPECT. Methods ACR uses all events detected in a defined energy band, by modeling all orders of Compton scatter interactions in the projector and backprojector. The energy band is divided into several energy windows, and projection and backprojection are performed separately for each energy window using an iterative approach. Attenuation, detector response, and detector energy resolution are modeled. The computing requirements depend critically on the width of the energy band, as inclusion of lower-energy data requires modeling of higher orders of scatter. Wider energy bands can, potentially, yield lower image noise, as even multiply scattered photons carry some information. We evaluated the effects of energy band width on estimation task performance by simulating, using SIMSET, very high-count projections of a 10-cm-diameter sphere containing a 1-cm-diameter higher-activity sphere, and calculating the Cramer-Rao bound (CRB) on estimation of activity within the smaller sphere. Results Inclusion of photons detected with energies down to 120 keV significantly improves the precision. Further improvement, but at a moderate level, can be gained by including photons in the energy band 120-70 keV. Photons below 70keV improve precision only marginally and probably should not be used in ACR. Conclusions Our data suggest that inclusion of higher-order scattered photons in ACR improves the precision with which activity can be estimated. However, the wider the band, the more complex and time-consuming the reconstruction. This trade-off, as well as the feasibility of achieving the CRB using ACR, will be studied in future work. Research Support This work was supported in part by the National Institutes of Health under Grant R01 EB000802 and R21 CA123057 and American Heart Association, Scientist Development Grant, Grant 0735328N. ER -