A new approach to overcome the inconveniences in electron dosimetry associated with the beam scanning technique in linacs

Abstract

The therapeutic advantages of scanned electron beams from medical linear accelerators are accompanied by difficulties in electron dosimetry. Owing to short-time dose inhomogeneities in the treatment field, implicit in the system, time-consuming point-by-point measurements of dose distributions are normally required. However, by triggering the measuring time synchronously with the slow scan frequency, the time necessary to record reliable dose distributions can be shortened considerably. The instrumentation for the computer-controlled dosimetry system developed for this task is described. The results of our measurements show that reproducibility in dose within +/- 1% is achievable in less than 6.3 s per point for scanned electron beams.

AAPM Task Group Report 290: Respiratory motion management for particle therapy

“…77,78 US was first used with proton beams in 1958 79 and was extensively used with electron beams during the 1970s and 1980s. 80 A description of various scan patterns that have been used for particle beam therapy is provided in Moyers and Vatnitsky. 81 When the US is used with particle beams, it is usually performed with a static range modulator (such as a ridge filter), or in concert with the energy stacking technique.…”

“… 77 , 78 US was first used with proton beams in 1958 79 and was extensively used with electron beams during the 1970s and 1980s. 80 A description of various scan patterns that have been used for particle beam therapy is provided in Moyers and Vatnitsky. 81…”

“…The US is a beam delivery technique that spreads the beam laterally across the target, and it provides a lateral dose profile similar to that achieved by the DS technique 77,78 . US was first used with proton beams in 1958 79 and was extensively used with electron beams during the 1970s and 1980s 80 . A description of various scan patterns that have been used for particle beam therapy is provided in Moyers and Vatnitsky 81…”

Clinical electron‐beam dosimetry: Report of AAPM Radiation Therapy Committee Task Group No. 25

“…The probe may provide an instantaneous reading (e.g., ionization chamber or silicon diode) or one to be read later (e.g., film). If the beam is spread by a scanning magnet, the beam must be sampled either synchronously (Ertan et al, 1984) or for times as long as one minute to achieve 1% to 2% accuracy, making the operation of isodose tracking devices impractical, except for the case of reading film. Film dosimetry, which offers a convenient method of obtaining a complete set of isodose curves, is discussed in Sec.…”