Speaker
Description
Double Photon Emission Computed Tomography (DPECT) is an imaging method using radionuclides that emit two cascade photons. It can be applied to ring Compton camera system. Two Compton cones are generated per DPECT coincidence event and the intersection can be taken as system matrix component. It was reported that DPECT in Compton imaging reduces background and improves spatial resolution in Compton camera application.[1] In addition to previous DPECT study using Compton camera, this study utilizes additional properties of cascade photons.[2,3]
Angular correlation is about the angle between the first and the second photons in cascade. 111In was used in this study and 245 keV is the second photon and its polarization shows correlation. Figure 1(a) shows the description of cascade photons. Figure 1(b) shows differential Compton scattering cross section of 245 keV on azimuthal scattering angle in case of 90° angular correlation angle and different polar scattering angles. The information on azimuthal angle dependence has potential to further improve the quality of the image.
Geant4 simulation was conducted to using 111In point source. List-mode Maximum Likelihood Expectation Maximization (MLEM) was used to reconstruct images from double coincidence events. System matrix with polarization information was calculated event by event from theoretical angular and polarization correlation and energy deposition in each detector. The difference between corrected and uncorrected images is shown in Figure 1(c) and (d). Additional details will be reported.
[1] M. Uenomachi, Y. Mizumachi, et. al. Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip. 954, 161682 (2020).
[2] D. R. Hamilton, Phys. Rev. 58, 122 (1940).
[3] D. R. Hamilton, Phys. Rev. 74, 782 (1948).
