The objective of this study was to investigate the effect of field output factors (FOFs) according to the current protocol for small‐field dosimetry in conjunction to treatment planning system (TPS) commissioning. The calculated monitor unit (MU) for intensity‐modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans in Eclipse™ TPS were observed. Micro ion chamber (0.01 CC) (CC01), photon field diode (shielded diode) (PFD), and electron field diode (unshielded diode) (EFD) were used to measure percentage depth doses, beam profiles, and FOFs from 1 × 1 cm2 to 10 × 10 cm2 field sizes of 6 MV photon beams. CC01 illustrated the highest percentage depth doses at 10 cm depth while EFD exhibited the lowest with the difference of 1.6% at 1 × 1 cm2. CC01 also produced slightly broader penumbra, the difference with other detectors was within 1 mm. For uncorrected FOF of three detectors, the maximum percent standard deviation (%SD) was 5.4% at 1 × 1 cm2 field size. When the correction factors were applied, this value dropped to 2.7%. For the calculated MU in symmetric field sizes, beam commissioning group from uncorrected FOF demonstrated maximum %SD of 6.0% at 1 × 1 cm2 field size. This value decreased to 2.2% when the corrected FOF was integrated. For the calculated MU in IMRT‐SRS plans, the impact of corrected FOF reduced the maximum %SD from 6.0% to 2.5% in planning target volume (PTV) less than 0.5 cm3. Beam commissioning using corrected FOF also decreased %SD for VMAT‐SRS plans, although it was less pronounced in comparison to other treatment planning techniques, since the %SD remained less than 2%. The use of FOFs based on IAEA/AAPM TRS 483 has been proven in this research to reduce the discrepancy of calculated MU among three beam commissioning datasets in Eclipse™ TPS. The dose measurement of both symmetric field and clinical cases comparing to the calculation illustrated the dependence of the types of detector commissioning and the algorithm of the treatment planning for small field size.

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Introduction: This study aims to experimentally determine field output factors using the methodologies suggested by the IAEA-AAPM TRS-483 for small field dosimetry and compare with the calculation from Monte Carlo (MC) simulation. Methods: The IBA-CC01, Sun Nuclear EDGE and IBA-SFD detectors were employed to determine the uncorrected and the corrected field output factors for 6 MV photon beams. Measurements were performed at 100 cm source to axis distance, 10 cm depth in water, and the field sizes ranged from 1 × 1 to 10 × 10 cm2. The use of field output correction factors proposed by the TRS-483 was utilised to determine field output factors. The measured field output factors were compared to that calculated using the egs_chamber user code. Results: The decrease in the percentage standard deviation of the measured three detectors was observed after applying the field output correction factors. Measured field output factors using CC01 and EDGE detectors agreed with MC values within 3% for field sizes down to 1 × 1 cm2, except the SFD detector. Conclusions: The corrected field output factors agree with the calculation from MC, except the SFD detector. CC01 and EDGE are suitable for determining field output factors, while the SFD may need more implementation of the intermediate field method.

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This study aimed to evaluate the feasibility of using optically stimulated luminescence dosimeters (OSLDs), nanoDots, for the determination of an average glandular dose (AGD) with a specific digital breast tomosynthesis (DBT) system, whereas the X-ray tube was fixed (2D mode) and moved (3D mode). The entrance surface air kerma (ESAK) was measured by placing the nanoDots on the surface of a polymethyl methacrylate (PMMA) phantom with 25, 28, and 34 kV W/Rh techniques. The experimental setup of the ESAK measurement was simulated using a Monte Carlo simulation code to determine the ESAK and the backscatter factor (BSF). The AGD was calculated by dividing the ESAK values over the corresponding BSF factors for each PMMA phantom thickness and multiplying the AGD conversion factors. The AGD determination by the nan-oDots variated within ±5% for both 2D and 3D modes, compared to those determined using an ionization chamber. The results were similarly observed for the simulation, except for the 25 kV on the 3D mode. Regarding the International Atomic Energy Agency technical reports series number 457, the nanoDots can be used for the AGD determination with realistic 2D and 3D image acquisitions based on ±10% uncertainty.