The objective of this study is to analyze small field photon beams acquired with commonly available detectors. Beam profiles of 6 MV photons from the Siemens Primus Linear Accelerator were measured with a micro ion chamber (IC CC01, IBA) and linear diode array (LDA-99SC, IBA). Data was acquired using a water phantom for small fields (0.5×0.5 cm2 to 4×4 cm2) at depth of maximum dose, 5 cm and 10 cm. Profiles were also generated with EGSnrc Monte Carlo code. Measured and simulated profiles were compared in terms of percentage difference of the area under the simulated and measured profiles (PD), ratio of the measured to simulated dose at the point of maximum deviation within the central region of profile (R), full width half maximum (FWHM) and penumbra. For field sizes ≥1×1 cm2, the maximum PD is 3.17 % and 2.87 % for IC and LDA respectively, whereas R is in the range of 0.95–1.05 for IC and 0.99–1.05 for LDA. LDA measured FWHM and penumbra are also in better agreement with the simulated results. This study demonstrated that LDA can be used for acquisition of beam profiles for field size as low as 1×1 cm2.
M.Aspradakis, et al., IPEM Report 103: Small field MV photon dosimetry, 2010.
2.
I.J.Das, et al., Small fields: Nonequilibrium radiation dosimetry, Medical Physics35 (2008), 206–215.
3.
P.Francescon, et al., Total scatter factors of small beams: A multidetector and Monte Carlo study, Medical Physics35 (2008), 504–513.
4.
IAEA, T., 398, Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water.Vienna International Atomic Energy Agency, 2000.
5.
J.M.Lárraga-Gutiérrez, et al., Properties of a commercial PTW-60019 synthetic diamond detector for the dosimetry of small radiotherapy beams, Physics in Medicine and Biology60 (2015), 905–924.
6.
F.Marsolat, et al., A new single crystal diamond dosimeter for small beam: Comparison with different commercial active detectors, Physics in Medicine and Biology58 (2013), 7647–7660.
7.
M.Tyler,, et al., Characterization of small-field stereotactic radiosurgery beams with modern detectors, Physics in Medicine and Biology58 (2013), 7595–7608.
8.
G.Cranmer-Sargison, et al., Experimental small field 6MV output ratio analysis for various diode detector and accelerator combinations, Radiotherapy and Oncology100 (2011), 429–435.
9.
J.M.Lárraga-Gutiérrez, Experimental determination of field factors () for small radiotherapy beams using the daisy chain correction method, Physics in Medicine and Biology60 (2015), 5813–5831.
10.
S.Tanny, et al., Correction factor measurements for multiple detectors used in small field dosimetry on the Varian Edge radiosurgery system, Medical Physics42 (2015), 5370–5376.
11.
S.Russo, et al., Small field output factors evaluation with a microDiamond detector over 30 Italian centers, Physica Medica32 (2016), 1644–1650.
12.
H.F.Godson, et al., Small field output factors: Comparison of measurements with various detectors and effects of detector orientation with primary jaw setting, Radiation Measurements85 (2016), 99–110.
13.
P.Z.Liu, et al., Small field correction factors for the IBA Razor, Physica Medica32 (2016), 1025–1029.
14.
H.F.Godson, et al., Analysis of small field percent depth dose and profiles: Comparison of measurements with various detectors and effects of detector orientation with different jaw settings.Journal of medical physics/Association of Medical Physicists of India41 (2016), 12.
15.
J.Gersh, et al., SU-E-T-125: High-resolution linear diode array for use in stereotactic beam commissioning, Medical Physics39 (2012), 3731–3732.
16.
S.Gholampourkashi, et al., Monte Carlo and analytic modeling of an Elekta Infinity linac with Agility MLC: Investigating the significance of accurate model parameters for small radiation fields, Journal of Applied Clinical Medical Physics20 (2019), 55–67.
17.
R.G.LeãoJr, et al., Validação de um modelo computacional de acelerador linear VARIAN CLINAC 2100 utilizando o código EGSnrc para utilização em dosimetria de pequenos campos, Brazilian Journal of Radiation Sciences6 (2018).
18.
S.Hashimoto, et al., Field-size correction factors of a radiophotoluminescent glass dosimeter for small-field and intensity-modulated radiation therapy beams, Medical Physics45 (2018), 382–390.
A.Asadi, et al., Monte Carlo evaluation of the potential benefits of flattening filter free beams from the Oncor® clinical linear accelerator, Journal of X-ray Sciece and Technology26 (2018), 281–302.
J.U.Würfel, Dose measurements in small fields, Medical Physics1 (2013), 81–90.
24.
G.X.Ding, et al., Commissioning stereotactic radiosurgery beams using both experimental and theoretical methods, Physics in Medicine and Biology51 (2006), 2549–2566.
25.
H.Bouchard, et al., Detector dose response in megavoltage small photon beams. I. Theoretical concepts, Medical Physics42 (2015), 6033–6047.
26.
E.E.Wilcox, et al., Evaluation of GAFCHROMIC® EBT film for CyberKnife® dosimetry, Medical Physics34 (2007), 1967–1974.
27.
C.Martens, et al., The value of the PinPoint ion chamber for characterization of small field segments used in intensity-modulated radiotherapy, Physics in Medicine & Biology45 (2000), 2519–2530.
28.
J.A.Gersh, et al., The clinical impact of detector choice for beam scanning, Journal of Applied Clinical Medical Physics15 (2014), 174–193.
29.
S.B.Scarboro, et al., Variations in photon energy spectra of a 6MV beam and their impact on TLD response, Medical Physics38 (2011), 2619–2628.
30.
E.E.Wilcox, et al., Accuracy of dose measurements and calculations within and beyond heterogeneous tissues for 6MV photon fields smaller than 4cm produced by Cyberknife, Medical Physics35 (2008), 2259–2266.
