Methods and systems are provided for analyzing a respiratory motion waveform acquired during acquiring imaging data with a molecular imaging device. In one embodiment, a method comprises acquiring imaging data with a molecular imaging apparatus, analyzing a respiratory motion waveform acquired during the acquiring imaging data, and applying gating to the acquired imaging data based on the analyzed respiratory motion waveform. In this way, gating may be applied to the acquired imaging data in order to generate an image for medical diagnosis with increased image quality and accuracy.