A patient-specific, restraining device is fabricated directly from the patients diagnostic images, (e.g. Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and Ultrasound) fabricated by additive manufacturing techniques, also known as 3D printing, using an algorithm that directly translates the medical images into instructions for the 3D printer. The patient-specific restraining device incorporates dosimetry devices to allow for real-time, near real-time or after-the-fact measurement of delivered radiation at the entry and exit points on the body. Using a patients medical images and dose planning software, patient-specific dose calculations allows for the calculation of the predicted dose for each location of entry and exit of the beam on the restraining device. This restraining device and method may be used to measure irradiation dosages in real time, adjust dosage levels based on such measurements, and then deliver more accurate and precise treatments during advanced treatment techniques.