Abstract: Disclosed is a computer-implemented method of transmitting identification information of a medical instrument. The method encompasses comparing a digital image of an instrument tray and an instrument to a digital image of just the instrument tray to determine the identity of the instrument. A characteristic geometry such as its envelope is assigned to the instrument, and a characteristic quantity of the envelope such as its aspect ratio may be used to identify the instrument. Based on determining, from the image of the instrument and the instrument tray, the relative position between those two entities, the method determines whether the instrument has been taken from the instrument tray, and accordingly instructs a medical computing system about this determination. The medical computing system may then determine whether the correct instrument has been taken from the instrument has been taken from the instrument tray, for example by comparison with medical procedure planning data.