Systems for establishing a reproducible breath-holding pattern during radiotherapy are disclosed. An exemplary image-guided radiotherapy system (100) may include an airway breathing controller (ABC) device (160), which may block airflow to the patient during imaging and/or radiotherapy to immobilize a target tumor. A patient may practice breath-holding during a training session until a reproducible breath-hold pattern is established. The patient may perform the breath-hold pattern in imaging and/or radiotherapy sessions, during which physiological signals may be measured from the patient and compared to baseline signals collected during the training session. Variation between measured signals and baseline signals may indicate unreproducible breath-holding, in which case radiation delivery may be altered or halted.
