Design and experimental testing of air slab caps which convert commercial electron diodes into dual purpose, correction‐free diodes for small field dosimetry

Abstract

It is possible to create a diode which does not require corrections for small field output factor measurements. This has been performed and verified experimentally. The ability of a detector to be "correction-free" depends strongly on its design and composition. A nonwater-equivalent detector can only be "correction-free" if competing perturbations of the beam cancel out at all field sizes. This should not be confused with true water equivalency of a detector.

Spectral distribution of particle fluence in small field detectors and its implication on small field dosimetry

“…The influence on the electron spectrum of detectors with extracameral components of high atomic number and density suggests that adding extracameral components of low atomic number and density could counterbalance some of the small field effects. This was in fact proposed in Refs., that investigated possible correction‐free detectors by incorporating low‐density components to the detector design.…”

Correction factor measurements for multiple detectors used in small field dosimetry on the Varian Edge radiosurgery system

“…1,[10][11][12][13]27 The selection of these detectors covers a broad selection of choices available to clinical physicists, including a newly released chamber with the Exradin A26. Despite semiconducting diodes and single-crystal diamond detectors being prominently featured in many recent publications, [2][3][4][5]25,[27][28][29][30] microchambers remain a common instrument for their familiarity and well-studied properties in conventional dosimetry. 11,13,[31][32][33][34][35] Moving from Monte Carlo derived correction factors toward measured values is an important step in ensuring that the majority of clinics can implement accurate small field dosimetry.…”

“…It has been extensively studied by other publications for use in small field dosimetry. 4,11,12,25 The Sun Nuclear EDGE diode is only configured for use in the horizontal mounting.…”

“…The study of small fields has been a very extensive area of research over the last two decades and has been repeatedly modeled with Monte Carlo studies, measurement of output factors and profiles, and detector comparison. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Alfonso et al 15 proposed a new formalism for the calculation of dose to small fields which corrects detector readings on a machine and field-size specific basis. The true dose to water for a clinical field of a given beam quality can be traced to the known dose to water for the machine-specific reference field by measuring the ratio of detector responses in each field and applying the appropriate correction factor for the detector, beam quality, and field size.…”

Detector dose response in megavoltage small photon beams. I. Theoretical concepts

“…In a situation where overall correction factors are needed, the geometry of the detector must be entirely modeled to account for all the effects. It is worth noting that previous studies have proposed modifying the design of detectors using density compensation to minimize these effects, 23,29,89,90 although it is unlikely that these modifications can apply to all disequilibrium situations at once.…”