Abstract: A system is disclosed for synchronizing the activation of an imaging device, such as an X-ray machine, with patient respiration. The imaging device includes a conventional trigger signal input for activating the imaging device in response to a preset signal. The system includes a respirator device, such as a ventilator or respiration band, which provides an output signal indicative of the degree of patient inspiration. A processing circuit is responsive to the output signal from the respiration device and generates the preset signal at a preselected degree of patient inspiration. The output signal from the processing circuit is coupled to the imaging device signal input to activate the imaging means at the preselected degree of patient inspiration.