A phantom and simulation study on body-shields to cope with radioactivity outside the field of view in 3D PET
Basic physics characteristics of body-shields to screen out radioactivity outside the field of view were analyzed by phantom experiments and Monte-Carlo simulation. The shielding effect depended primarily on the geometrical condition as in the case of end-shields. However, body-shields became more effective by increasing the shield thickness more than 10 mm as not in the case of end-shields. This characteristic difference was related with the fractions of un-scattered and shield-scattered components. A body-shield could be as effective as an end-shield if a good geometrical condition was kept with sufficient shield thickness.
We consider the cross area of the PP_ and PSV_wave window as the best window for joint PP_ and PSV_wave acquisition in VTI media. Within the effective window, the PP_ and PSV_wave's raypathes and phase angles at all reflection points are calculated, and the reflection (or transmission) coefficients' ratios of PSV- to PP_wave solved from Zoeppritz equations are defined as the controlling factor G. Then we use G values as the main controlling parameters of joint PP_ and PSV_wave acquisition design in VTI media, determine the best receiving window of detectors by analyzing G values, and derive the method of optimizing the receiving window for acquisition of multi_component converted seismic data in VTI media.