Open AccessSmall field electron beam dosimetry using MOSFET detector
Author(s) -
Amin Md Nurul,
Heaton Robert,
Norrlinger Bern,
Islam Mohammad K.
Publication year - 2010
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1120/jacmp.v12i1.3267
Subject(s) - dosimetry , dosimeter , ionization chamber , mosfet , materials science , imaging phantom , cathode ray , beam (structure) , electron , dose profile , linear particle accelerator , absorbed dose , optics , optoelectronics , physics , nuclear medicine , ion , nuclear physics , transistor , medicine , ionization , quantum mechanics , voltage
The dosimetry of very small electron fields can be challenging due to relative shifts in percent depth‐dose curves, including the location of d max , and lack of lateral electronic equilibrium in an ion chamber when placed in the beam. Conventionally a small parallel plate chamber or film is utilized to perform small field electron beam dosimetry. Since modern radiotherapy departments are becoming filmless in favor of electronic imaging, an alternate and readily available clinical dosimeter needs to be explored. We have studied the performance of MOSFET as a relative dosimeter in small field electron beams. The reproducibility, linearity and sensitivity of a high‐sensitivity microMOSFET were investigated for clinical electron beams. In addition, the percent depth doses, output factors and profiles have been measured in a water tank with MOSFET and compared with those measured by an ion chamber for a range of field sizes from 1 cm diameter to 10 cm × 10 cm for 6, 12, 16 and 20 MeV beams. Similar comparative measurements were also performed with MOSFET and films in solid water phantom. The MOSFET sensitivity was found to be practically constant over the range of field sizes investigated. The dose response was found to be linear and reproducible (within ± 1 % for 100 cGy). An excellent agreement was observed among the central axis depth dose curves measured using MOSFET, film and ion chamber. The output factors measured with MOSFET for small fields agreed to within 3% with those measured by film dosimetry. Overall results indicate that MOSFET can be utilized to perform dosimetry for small field electron beam. PACS number: 87.55.Qr