Real-time in vivo luminescence dosimetry in radiotherapy and mammography using Al₂O₃:C

New treatment and clinical imaging techniques have created a need for accurate and practical in vivo dosimeters in radiation medicine. This work describes the development of a new optical-fiber radiation dosimeter system, based on radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon-doped aluminium oxide (Al₂O₃:C), for applications in radiotherapy and mammography. This system offers several features, such as a small detector, high sensitivity, real-time read-out, and the ability to measure both dose rate and absorbed dose. Measurement protocols and algorithms for the correction of responses were developed to enable a reliable absorbed dose assessment from the RL and OSL signals. At radiotherapy energies, the variation of the signal with beam parameters was smaller than 1% (1 SD). Treatment-like experiments in phantoms, and in vivo measurements during complex patient treatments (such as intensity-modulated radiation therapy) indicate that the RL/OSL dosimetry system can reliably measure the absorbed dose within 2%. The real-time RL signal also enables an individual dose assessment from each field. The RL/OSL dosimetry system was also used during mammography examinations. In such conditions, the reproducibility of the measurements showed to be around 3%. In vivo measurements on three patients showed that the presence of the RL/OSL probes did not degrade the diagnostic quality of the radiograph and that the system could be used to measure exit doses (i.e., absorbed doses on the inferior surface of the breast). A Monte carlo study proved that the energy dependence of the RL/OSL system at these low energies could be reduced by optimizing the
design of the probes. It is concluded that the new RL/OSL dosimetry system shows considerable potential for applications in both radiotherapy and mammography.