Quantitative imaging and correction for cascade gamma radiation of 76Br with 2D and 3D PET

Several positron emitting nuclides with applications in PET, such as Br-76, I-124, In-110m and Y-86, also emit gamma radiation in their decays. Measured coincidences between annihilation photons and this cascade gamma radiation are essentially true coincidences and the standard PET corrections do not account for them. We investigated the performance of Br-76 in 2D and 3D PET, the effect of the gamma radiation emitted by Br-76 on quantitative accuracy and the distribution of cascade gamma radiation coincidences in 2D and 3D PET sinograms. A correction method for cascade gamma radiation coincidences was implemented and evaluated. Count rate linearity was affected by the gamma radiation from the Br-76 decay. Spatial resolution and sphere recovery were slightly worse for Br-76 compared to F-18. Correction for cascade gamma radiation coincidences by subtraction of a linear projection tail fit improved total correction accuracy to similar values as for positron-only emitters such as F-18, and improved image contrast significantly.