As seen in section 3.1, AR was the choice of visualization more often compared to VR in the procedures with Freehand SPECT that we analyzed. However, this does not imply that AR is superior to VR. The usage of AR and VR strongly depends on the requirements within the current surgical workflow stage. AR was generally used to obtain a big picture of the activity distribution over the patient anatomy; however the VR mode was mostly preferred whenever more accurate measurement and localization was required. According to the users, having two complementary viewing modes improved the overall usefulness of the device.