Dosimetry is a measurement and/or calculation of absorbed dose of energy per unit mass of the irradiated target material. In medical applications, the target material is usually the patient, where several modes of diagnostics and therapy rely on ionizing irradiation, including radiotherapy, x-rays, electrons, protons, neutrons, and heavy ions. For example, in radiation therapy for cancer, the goal is to deliver the maximum dose to a tumor, while minimizing the dose to the normal surrounding tissue. In such applications, it is important to characterize the source of the radiation beam such that the amount of energy absorbed by the patient, in both normal and cancerous tissues, can be predicted to potentially tailor the therapeutic dose of radiation. However, dosimetry methods to date are time and labor intensive, resulting in large amounts of information which need to be processed to determine the characteristics of the radiation source.
A researcher at the University of Michigan has developed a novel, accurate real-time thin-film, flat-panel dosimetry device. The device includes a medium whose radiological properties are similar to that of a human tissue in which the dose is determined, and a sensor placed adjacent to this medium. Upon radiation, the energy is absorbed in the medium due to emission of high energy electrons. The resulting electrons and holes generated in the sensor are then extracted as an indication of energy of the incident radiation. This device can make dosimetric measurements for a variety of situations including those involving megavoltage beams, which may include measuring absolute dose, relative dose distributions in phantoms, quality assurance of machine output, beam flatness and symmetry, measurement of temporally varying and transmission for exit dosimetry for patients.
Applications and Advantages
- radiation oncology to dosimetrically characterize megavoltage therapy beams
- can be used for both medical and non-medical applications
- accurate, real-time dosimetry