1. A treatment system, comprising: an imaging apparatus; a motion detecting apparatus to acquire measurement data indicative of a motion of a target, wherein the motion detecting apparatus comprises an ultrasound apparatus, and wherein the measurement data is ultrasound measurement data; a linear accelerator to deliver radiation treatment beams to the target; and a processing device coupled with the imaging apparatus, the motion detecting apparatus, and the linear accelerator, wherein the processing device is to: direct a first radiation treatment beam to the target; and in response to determining that the motion of the target is not within a treatment tolerance: cause the imaging apparatus to generate one or more x-ray images of the target, and pause the directing of the first radiation treatment beam to the target, wherein the processing device is further to: prior to treatment of the target, determine a treatment plan comprising planned delivery of a plurality of radiation treatment beams; receive selection of an initial image age threshold; determine that completing delivery of at least one radiation treatment beam of the planned delivery of the plurality of radiation treatment beams extends beyond the initial image age threshold; and modify the treatment plan by splitting the at least one radiation treatment beam into two or more radiation treatment beams, wherein delivery of each of the two or more radiation treatment beams is completed at or before the initial image age threshold.