Abstract: An infrared imaging camera (4) acquires a plurality of frames (94) of infrared radiation from a patient (P) positioned in a field-of-view (92) of the camera (4). Each frame (94) is acquired during a corresponding frame sample interval and each frame (94) corresponds to the infrared radiation acquired from an array of optical elements (90) in the field-of-view (92) during its frame sample interval. Plural rates of change are determined from infrared radiation received from the array of optical elements (90), with each rate of change corresponding to a change of infrared radiation received from the same optical element (90) in at least two frames (94). Each rate of change is mapped to a color or a shade of gray and the color or shade of gray of each rate of change is mapped to a position in an image corresponding to the position of the corresponding optical element (90) in the field-of-view (92).