Radiation Dosimetry, Three‐Dimensional

Abstract Accurate delivery of radiation therapy is essential for the treatment to have the greatest probability of success. Determining the dose delivered by radiation beams and radioactive sources requires complex dosimetry procedures and sophisticated computerized treatment planning software. Validating the software to assure its accuracy is an essential component of the quality assurance program in a radiation therapy department. In recent years, radiation therapy has evolved to take advantage of new treatment delivery capabilities and ever‐more complex treatment planning techniques. These techniques allow the dose distribution to be tailored to closely match the shape of the target volume and avoid nearby sensitive tissues. Consequently, dosimetric validation devices must also allow the accurate measurement of dose in three dimensions. Conventional dosimetry systems measure the dose at a point or in a plane, and mapping a 3D dose distribution is difficult at best. As a result, there is a need for a reliable 3D radiation dosimetry system, with the capability of integrating the dose from a complex, and possibly dynamic treatment, so that the delivered dose can be mapped and compared with computer simulations. Today, the only true 3D dosimeters are radiosensitive gels and plastics that can be constructed to fill volumes and conform to complex surfaces. The science behind these dosimeters is developing rapidly, and their routine use in the clinic is believed to be imminent.