A noise equivalent counts approach to transmission imaging and source design

Noise equivalent counts are a convenient and effective means to assess PET emission image quality. We have extended the method to include the effects of transmission imaging on the statistics of attenuation corrected PET data. The result of the calculations is a noise figure which describes the SNR performance of the elements of the attenuation corrected emission sinogram. The noise figure demonstrates the tradeoff between emission and transmission imaging performance, and can be used to determine optimal partitioning of imaging time between emission and transmission scans. Also, the technique can be used to compare the efficacy of simultaneous transmission/emission imaging techniques and multiple orbiting rod source geometries. Experimental and simulated results from the GE 2048 PET scanner are used to demonstrate the model. In a sample imaging situation in that system geometry |0.2 |micro~Ci/cc activity in a 20-cm flood phantom, 3-mCi orbiting rod source(s)~, the dual rod source achieves 80 percent of the noise figure improvement which is available in simultaneous transmission/emission imaging without transmission data filtering, and demonstrates superior performance when a 3-point averaging transmission filter is applied.