In some situation, because we are dealing with patients after all, an adequate ECG tracing may not be properly achieved. This could occur with patients suffering from arrhythmogenic right ventricular dysplasia (ARVD). In these individuals, an adequate gating signal may be obtained by application of peripheral application. Peripheral gating works the same as ECG gating. A photo sensor is attached to the patient's finger as opposed to leads being placed on the patient's chest or back. Gating by this technique may often produce images of good diagnostic quality, but attention must be paid if the images are used for functional analysis. The reason is that the peak of the peripheral gating is delayed in time from the ECG R-wave. In other words, the images obtained with peripheral gating will be out of phase when compared with those obtained with ECG gating
