Visualization of Radium-223 chloride using an omnidirectional gamma-ray imaging Compton camera for radioactive environmental monitoring

We investigated the possibility of visualizing low-level radioactive contamination by 223Ra chloride injection in medical facilities using a highly sensitive gamma-ray omnidirectional imaging Compton camera. The detector consisted of CsI(Tl) scintillator cubes of 3.5 cm in size, which acted as scatterers or absorbers. The measurements were carried out using the detector in the nuclear medicine facility, where the 223Ra sources (such as used vial, syringe, etc.) with the radioactivities of less than 1 MBq were placed inside the preparation room. We confirmed four groups of gamma-ray full-absorption peaks between 270 keV and 810 keV as expected in the energy spectrum made by the sum of energy deposits in two counter coincidence events. Furthermore, we successfully detected the direction of the 223Ra source in the reconstructed gamma-ray image. Our proposed technique would be used as a low-level imaging dose monitor to visualize radioactive contamination by 223Ra in medical facilities.