Abstract: A device for detecting thermal differentials emanating from a radiant source by transforming such differentials to visible representations that can be photographically recorded for subsequent diagnostical and analytical study. The device includes a light transmitting housing having one end supporting a resilient frame with a flexible thermally responsive screen an opposite end supporting a camera. The device is especially useful in the early detection of cancer or of other contralateral heat differentials in the body due to various abnormal or disease conditions or to monitor chemotherapy or progress of surgical recovery.