1. A method of triggering an imaging process, comprising: obtaining breathing signals, the breathing signals representing a breathing of a subject that fluctuates in amplitude in response to the subject breathing freely, wherein the breathing signals are generated in a period during which the subject is allowed to breathe freely; analyzing the breathing signals to identify a non-periodicity in the breathing of the subject, wherein the identified non-periodicity is a deviation from a normal breathing pattern, the deviation being characterized as to exclude gradual breathing pattern variation that occurs over time; and after the non-periodicity has occurred, generating a signal to cause an imaging process to begin in response to the identified non-periodicity; wherein the acts of analyzing and generating are performed during a radiation treatment procedure; and wherein the method further comprises using an image from the imaging process to verify an item for the radiation treatment procedure.