Validation of a therapeutic radiation treatment involves using an applicator balloon surrounding an X-ray radiation source to support a plurality of X-ray sensor elements (XRSE). The XRSE are supported on the applicator balloon at distributed locations to sense applied radiation from the radiation source. At least one parameter of the applied radiation which has been sensed by the XRSE is compared to a corresponding parameter of a predetermined radiation treatment plan. Based on the comparing, a determination is made as to whether one or more requirements of the predetermined radiation treatment plan have been satisfied.