Attenuation correction for rotating slant-hole (RSH) SPECT using exact rebinning

We have recently derived an analytic method of image reconstruction for the rotating slant-hole (RSH) SPECT scanner for cardiac imaging. The method assumes that the emission activity lies in a region of constant attenuation. It operates by rebinning the three-dimensional (3-D) measured projections into the geometry of a stack of two-dimensional (2-D) slices and performing 2-D reconstruction in a second step. An important consequence of this method is a mathematical proof that opposing projections are not necessary for full tomographic reconstruction in the presence of attenuation. We have now tested our algorithm in the presence of noisy projection data and with projections which violates the constant attenuation assumption. We present results from simulated and real phantom data demonstrating effective attenuation correction in the presence of a uniform low-level of background in the torso, with truncated liver activity, and without opposing views. Our conclusions are that attenuation correction can be performed for RSH SPECT without measuring opposing views, and that the effect of background activity (which violates the assumptions required for exponential data) and truncated activity of a nearby liver are small and easily dominated by typical noise levels in SPECT imaging.