Demonstration of a novel source localization method in nuclear medicine based on ultrasound-guided double-photon angular correlation

In conventional gamma-ray imaging techniques in nuclear medicine, positron emission tomography based on coincidence detection of annihilation photons and single photon emission computed tomography using mechanical collimators are limited in spatial resolution to approximately 2-4 mm and 6-15 mm, respectively. In this study, we propose a novel gamma-ray imaging method based on measuring the angular correlation of cascade gamma rays with pulsed focused ultrasound application. When pulsed focused ultrasound with sufficient intensity to induce angular correlation changes is applied to a region containing $$^{111}$$ In, one-dimensional positional information can be obtained from the time difference between the start of the pulse emission and the change in angular correlation. We demonstrated angular correlation changes induced by pulsed focused ultrasound and investigated the dependence of the change magnitude of the angular correlation when the start time of the analysis time window is shifted from -3 $$\upmu $$ s to +3 $${\upmu }$$ s in 1 $${\upmu }$$ s intervals. The magnitude of the angular correlation change decreased as the analysis start time was shifted relative to the unshifted window. Because the shift time can be converted into distance using the ultrasound velocity in water, these results indicate the potential of pulsed focused ultrasound application and angular correlation measurements for source position discrimination.