The present invention provides medical devices 100, 300, 400, 500, 600 including camera systems 102, 102 ′, 102 ″ that image a portion 418 of subject 108 mounted on subject support 106. The medical device further includes a display system 104 that renders the position feedback indicators 130, 900. The display system is configured so that the position feedback indicator is visible to the subject when the subject is resting on the subject support. Execution of the machine executable instruction 120 causes the processor 114, which controls the medical device, to use the camera system to acquire the base point position image 122 (200) and to repeatedly acquire the subsequent image 124 using the camera system (200). 202), by inputting the base point position image and the subsequent image into the image conversion algorithm 128, the image conversion 126 from at least a part of the box cell of the base point position image to the box cell of the subsequent image is repeatedly calculated (204), and the position feedback is performed. Indicators 130, 900 are repeatedly rendered on the display (206). The position feedback indicator is controlled by image transformation.
