Prog Med Phys.  2023 Mar;34(1):1-9. 10.14316/pmp.2023.34.1.1.

Feasibility of a Linear Diode Array Detector for Commissioning of a Radiotherapy Planning System

• Hong SM
• Lee U
• Kim Sw
• Goh Y
• Park MJ
• Jeong C
• Kwak J
• Cho B

• KMID: 2541141
• DOI: http://doi.org/10.14316/pmp.2023.34.1.1

Abstract

Purpose
Although ionization chambers are widely used to measure beam commissioning data, point-by-point measurements of all the profiles with various field size and depths are timeconsuming tasks. As an alternative, we investigated the feasibility of a linear diode array for commissioning a treatment planning system.
Methods
The beam data of a Varian TrueBeam ® radiotherapy system at 6 and 10 MV with/without a flattening filter were measured for commissioning of an Eclipse Analytical Anisotropic Algorithm (AAA) ver.15.6. All of the necessary beam data were measured using an IBA CC13 ionization chamber and validated against Varian “Golden Beam” data. After validation, the measured CC13 profiles were used for commissioning the Eclipse AAA (AAA _CC13 ). In addition, an IBA LDA-99SC linear diode array detector was used to measure all of the beam profiles and for commissioning a separate model (AAA _LDA99 ). Finally, the AAA _CC13 and AAA _LDA99 dose calculations for each of the 10 clinical plans were compared.
Results
The agreement of the CC13 profiles with the Varian Golden Beam data was confirmed within 1% except in the penumbral region, where ≤2% of a discrepancy related to machinespecific jaw calibration was observed. Since the volume was larger for the CC13 chamber than for the LDA-99SC chamber, the penumbra widths were larger in the CC13 profiles, resulting in ≤5% differences. However, after beam modeling, the penumbral widths agreed within 0.1 mm. Finally the AAA _LDA99 and AAA _CC13 dose distributions agreed within 1% for all voxels inside the body for the 10 clinical plans.
Conclusions
In conclusion, the LDA-99SC diode array detector was found to be accurate and efficient for measuring photon beam profiles to commission treatment planning systems.

Keyword

Radiotherapy; Photon beam commissioning; Treatment planning system; Ionization chamber; Diode array detector

Figure

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  Fig. 1 Comparison of the profiles (40×40 cm2, dmax) measured by CC13 in this study with those of Varian Golden Beam data. (a) 6MV, (b) 6MV FFF, (c) 10MV, (d) 10MVFFF.

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  Fig. 2 Comparison of the LDA-99 and CC13 profiles measured at 6 MV with a flattening filter (FF) or flattening filter free (FFF) (field size=40×40 cm2): (a) 6 MV FF at dmax, (b) 6 MV FFF at dmax, (c) 6 MV FF at a depth of 30 cm, (d) 6 MV FFF at a depth of 30 cm.

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  Fig. 3 Comparison of the LDA99 and CC13 profiles measured at 10 MV with a flattening filter (FF) or flattening filter free (FFF) (field size=40×40 cm2): (a) 10 MV FF at dmax, (b) 10 MV FFF at dmax, (c) 10 MV FF at a depth of 30 cm, (d) 10 MV FFF at a depth of 30 cm.

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  Fig. 4 Comparison of the AAALDA99 and AAACC13 profiles at 6 MV with a flattening filter (FF) and flattening filter free (FFF) (field size=40×40 cm2): (a) 6 MV FF at dmax, (b) 6 MV FFF at dmax, (c) 6 MV FF at 30 cm, (d) 6 MV FFF at 30 cm. AAA, Analytical Anisotropic Algorithm.

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  Fig. 5 Comparison of the AAALDA99 and AAACC13 profiles at 10 MV with a flattening filter (FF) and flattening filter free (FFF) (field size=40×40 cm2): (a) 10 MV FF at dmax, (b) 10 MV FFF at dmax, (c) 10 MV FF at 30 cm, (d) 10 MV FFF at 30 cm. AAA, Analytical Anisotropic Algorithm.

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  Fig. 6 Dose difference between AAALDA99 and AAACC13 for liver stereotactic body radiotherapy. (a) Dose-difference color map in the sagittal plane. (b) Dose profile as it crosses the planning target volume in the cranio–caudal direction. AAA, Analytical Anisotropic Algorithm.

Reference

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