Fig. 1

Energy spectra of a Ra-223 vial around the air (a) and a Ra-223 vial in the chamber filled with iodine contrast media (CT value, 350 HU) (b) with the LEHR, MEGP and HEGP collimators or without any of collimator. LEHR low-energy high-resolution, MEGP medium-energy general purpose, HEGP high-energy general purpose