Abstract
TG-69 is a task group report of the AAPM on the use of radiographic film for dosimetry. Radiographic films have been used for radiation dosimetry since the discovery of x-rays and have become an integral part of dose verification for both routine quality assurance and for complex treatments such as soft wedges (dynamic and virtual), intensity modulated radiation therapy (IMRT), image guided radiation therapy (IGRT), and small field dosimetry like stereotactic radiosurgery. Film is convenient to use, spatially accurate, and provides a permanent record of the integrated two dimensional dose distributions. However, there are several challenges to obtaining high quality dosimetric results with film, namely, the dependence of optical density on photon energy, field size, depth, film batch sensitivity differences, film orientation, processing conditions, and scanner performance. Prior to the clinical implementation of a film dosimetry program, the film, processor, and scanner need to be tested to characterize them with respect to these variables. Also, the physicist must understand the basic characteristics of all components of film dosimetry systems. The primary mission of this task group report is to provide guidelines for film selection, irradiation, processing, scanning, and interpretation to allow the physicist to accurately and precisely measure dose with film. Additionally, we present the basic principles and characteristics of film, processors, and scanners. Procedural recommendations are made for each of the steps required for film dosimetry and guidance is given regarding expected levels of accuracy. Finally, some clinical applications of film dosimetry are discussed.
Highlights
Radiographic films based on silver halideAgHemulsions are widely used for relative dosimetry of external radiation treatment beams in the megavoltage energy range
Film dosimetry provides an attractive method for measuring dose distributions in phantoms for dose characterization and/or verification, or to perform quality control tests of radiation beamse.g., correspondence between light field and radiation treatment field, field flatness and field symmetry
Film dosimetry offers a convenient and quick method of obtaining a two-dimensional dose distribution from which a set of isodose curves can be obtained in the film plane
Summary
Radiographic films based on silver halideAgHemulsions are widely used for relative dosimetry of external radiation treatment beams in the megavoltage energy range. These films are convenient to use, providing permanent records of integrated spatial dose distributions. Film dosimetry has become even more popular and is indispensable for verifying advanced irradiation technique dose distributions such as produced from a soft wedge, intensitymodulated radiotherapyIMRT, and stereotactic radiosurgery. These new radiotherapy technologies make complexshaped tumor conformal irradiation feasible and clinically deliverable. The two-dimensional nature of film offers the option of selecting the orientation of the film relative to the dose distribution and, because it is an integrating dosimeter, aids in the measurement of dynamically delivered dose distributions
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have