Disclosed herein is an image forming method for forming an image on a reversible thermo-sensitive recording medium provided with a recording layer containing liquid crystal that exhibits a solid phase or a fixed phase at a room temperature and a cholesteric liquid crystal phase at higher temperature. In a preferred embodiment, the control circuit and corresponding method of the present invention compares a clock signal and the gate drive output of a PWM controller in order to recognize a failure condition and to rapidly provide control of the synchronous rectifier so as to prevent large negative current flow through the synchronous rectifier which may otherwise result in component damage. The thread releasing mechanism releases the thread when the threading hook is moving backward. A device connected to the microprocessor compares characteristic responses to actual signal parameters. The present invention enables the localized application of topical medications, thereby providing direct treatment to the area of the body in need.