Method for temporarily marking a region of interest (ROI) at a body surface of a patient , comprising - providing a medical imaging device having a bore and a table , wherein the table is transferable between a first position, in which at least a part of the patient is located inside the bore , and a second positon, in which at least the part of the patient is located outside the bore , wherein a medical image data set of the patient , comprising the body surface of the patient, is recordable by the medical imaging device , when the patient is in the first position; - providing an optical sensor device for recording an image of the patient for registering a position and/or a motion of the patient ; - providing a light source for marking a spot on the body surface of the patient as the region of interest (ROI) in the second position, wherein for matching their coordinate systems, the medical imaging device and the optical sensor device are calibrated with each other permanently, in particular in an installation step, wherein after calibration, the medical imaging device and the light source share a common coordinate system and are correlated to each other permanently, the method further comprising - recording a medical image data set of the body surface of the patient by the medical imaging device , - reconstructing and presenting the medical image data set on a screen to a user, - receiving a region of interest at the surface of the patient selected by the user on the screen, - recording an image data set of the body surface of the patient by the optical sensor device when the patient is in the second position, - co-registering the medical image data set and the image data set and - steering or controlling the light source such that a spot on the body surface of the patient corresponding to the region of interest is marked, when the patient is in the second position. - providing a medical imaging device having a bore and a table , wherein the table is transferable between a first position, in which at least a part of the patient is located inside the bore , and a second positon, in which at least the part of the patient is located outside the bore , wherein a medical image data set of the patient , comprising the body surface of the patient, is recordable by the medical imaging device , when the patient is in the first position; - providing an optical sensor device for recording an image of the patient for registering a position and/or a motion of the patient ; - providing a light source for marking a spot on the body surface of the patient as the region of interest (ROI) in the second position, wherein for matching their coordinate systems, the medical imaging device and the optical sensor device are calibrated with each other permanently, in particular in an installation step, wherein after calibration, the medical imaging device and the light source share a common coordinate system and are correlated to each other permanently, the method further comprising - recording a medical image data set of the body surface of the patient by the medical imaging device , - reconstructing and presenting the medical image data set on a screen to a user, - receiving a region of interest at the surface of the patient selected by the user on the screen, - recording an image data set of the body surface of the patient by the optical sensor device when the patient is in the second position, - co-registering the medical image data set and the image data set and - steering or controlling the light source such that a spot on the body surface of the patient corresponding to the region of interest is marked, when the patient is in the second position. <EOS>