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Optimizing dosimetric leaf gap parameters for radiation therapy: A comparative study using three diode-array
Yoshitsugu Matsumoto1, Ryosuke Sato2, Natsumi Futakami3
1Department of Radiation Oncology, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
Journal of Applied Clinical Medical Physics
|October 28, 2025
Summary
Diode array dosimeters like ArcCHECK, Delta4, and SRS MapCHECK can accurately determine the dosimetric leaf gap (DLG) values, comparable to ionization chambers. Small DLG variations result in clinically acceptable dose discrepancies.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- The dosimetric leaf gap (DLG) is crucial for accurate dose calculations in radiotherapy using the Eclipse system.
- Diode array dosimeters offer a fast, convenient method for determining DLG by measuring planar dose distributions.
Purpose of the Study:
- To compare DLG values derived from three diode array dosimeters (ArcCHECK, Delta4, SRS MapCHECK) with those from an ionization chamber (IC).
- To assess the reliability of diode array dosimeters in reproducing IC-based DLG values.
Main Methods:
- Optimal DLG values were determined for 6 MV, 10 MV, and FFF beams using ArcCHECK, Delta4, and SRS MapCHECK.
- IC-based DLG values were validated with radiochromic films.
- Twenty VMAT plans were recalculated with varying DLG values and compared to measured data using global/local gamma and dose difference criteria.
Main Results:
- The average DLG difference between IC and diode array dosimeters was -0.35 ± 0.23 mm.
- A -0.35 mm DLG difference corresponded to dose deviations of 0.27%–1.05%, within the acceptable clinical range.
- Radiochromic film verification using IC-based DLG values showed an average gamma pass rate of 98.7% ± 2.3%.
Conclusions:
- Diode array dosimeters can determine DLG values comparable to ionization chambers.
- Observed DLG discrepancies between methods lead to dose differences within the clinically acceptable range (approximately 1%).
