Output factor determination based on Monte Carlo simulation for small cone field in 10-MV photon beam

Abstract

The difficulty of measuring output factor (OPF) in a small field has been frequently discussed in recent publications. This study is aimed to determine the OPF in a small field using 10-MV photon beam and stereotactic conical collimator (cone). The OPF was measured by two diode detectors (SFD, EDGE detector) and one micro-ion chamber (PinPoint 3D chamber) in a water phantom. A Monte Carlo simulation using simplified detector model was performed to obtain the correction factor for the detector measurements. About 12% OPF difference was observed in the measurement at the smallest field (7.5 mm diameter) for EDGE detector and PinPoint 3D chamber. By applying the Monte Carlo-based correction factor to the measurement, the maximum discrepancy among the three detectors was reduced to within 3%. The results indicate that determination of OPF in a small field should be carefully performed. Especially, detector choice and appropriate correction factor application are very important in this regard.

Monte‐Carlo calculation of output correction factors for ionization chambers, solid‐state detectors, and EBT3 film in small fields of high‐energy photons

“… 16 Determination of output factors and output correction factors for photon energies ≥10 MV was performed in the works of Refs. 1 , 25 , 26 , 27 and Refs., 28 , 29 respectively. In the present paper, the values of the output correction factor were determined in the small fields of 10, 15, 18, and 20 MV photon beams for a set of detectors widely used in clinical dosimetry: a diode detector Dosimetry Diode E (type 60017), a diamond detector microDiamond (type 60019), as well as an EBT3 dosimetric film, and four models of micro‐ionization chambers: a Semiflex Chamber (type 31010), a Semiflex 3D Chamber (type 31021), a PinPoint Chamber (type 31015), and a PinPoint 3D Chamber (type 31016).…”

“…In addition, the measured output factors for small fields require applying of correction factors for the ratio of the detector readings 16 . Determination of output factors and output correction factors for photon energies ≥10 MV was performed in the works of Refs 1,25–27 . and Refs., 28,29 respectively.…”

Evaluation of nanoDot optically stimulated luminescence dosimeter for cone-shaped small-field dosimetry of cyberknife stereotactic radiosurgery unit: A monte carlo simulation and dosimetric verification study

“…All of three factors can affect detector response, and therefore, there are several studies focusing on the critical selection of detectors for small fields and their verification to improve the accuracy and precision of measured dose. [3456789] Total scatter factors in small fields were investigated by Francescon et al . [10] in which scatter factors measured with different detectors have shown a variability for the smallest collimators of Cyberknife system.…”