In some embodiments, a safety system for a close range scanning machine inhibits collision of moving detector heads with a patient or other object. For example a proximity sensor and/or a collision sensor may guide to bring the head close enough to a patient and/or warn to prevent a collisions and or reduce impact. Parts that are in that are in the FOV of the detector may be transparent to the detected signal and/or uniformly affect the signal, facilitating identification of the source of the signal from the detector. In some embodiments, a dynamic motion restrictor is set during scanning according to the desired scanning position and/or the position of the patient. In some embodiments, a motion restrictor acts to prevent unbalanced motions.
