%0 Journal Article %A Xing Rong %A Yong Du %A Michael Ljungberg %A Eric Frey %T Experimental evaluation of quantitative accuracy of activity estimates from a new Y-90 Bremsstrahlung SPECT method %D 2011 %J Journal of Nuclear Medicine %P 2019-2019 %V 52 %N supplement 1 %X 2019 Objectives The wide and continuous energy spectrum of Yttrium-90 bremsstrahlung photons imposes huge challenges on quality and quantitative accuracy of SPECT reconstruction. We have previously developed an OS-EM reconstruction method that models physical image degrading factors to improve image quality and quantitative accuracy of activity estimates. In this work, we evaluated this method for both HEGP and MEGP collimators. Methods An elliptical phantom with spheres having diameters of 1.5, 3.3, and 5.5 cm with and without background activity was scanned on a Philips Precedence SPECT/CT system. The sphere-to-background activity concentration ratio was ~10:1. A wide energy window 100-500keV was used. A phantom with a 3.4 mm diameter cylindrical compartment containing Y-90 solution on the axis of a 25.4 mm diameter acrylic cylinder was used to measure the camera sensitivity. The geometric photon sensitivity was estimated using a combination of curve fitting and MC simulation. We compared the errors in the activity estimates from the two collimators. Results The errors in activity estimates ranged from an overestimate of 4% to an underestimate of 17%. Without background activity, the errors were smaller for the MEGP than the HEGP collimator for all the spheres, likely because of the better resolution and resulting reduced partial volume effects. By contrast, with the non-zero background, the accuracy was worse for MEGP than HEGP. A likely explanation is that the MEGP collimator had higher septal penetration and the model of the imaging process in the reconstruction method of these effects is imperfect, resulting in incomplete compensation. This increased model mismatch has also been demonstrated by MC simulations. Conclusions For both collimators, the proposed reconstruction method provided relatively accurate Y-90 activity estimates. The MEGP collimator provided higher resolution, but improved models of degrading factors are needed to exploit this advantage in cases where there is significant background activity %U