<p>Scar formation results from nonregenerative healing after tissue injury. Complications may occur if the scar grows beyond a certain threshold. Superficial X-ray radiotherapy offers significant advantages as an adjuvant method for surgical treatment of scars. Following the widespread application of the superficial X-ray radiotherapy system SRT-100, accurate dose measurements are key to the implementation of superficial X-ray radiotherapy. In this study, the absorbed dose measured in superficial X-ray radiotherapy was traced to the primary standard based on air kerma. According to this principle, based on the technical parameters of the SRT-100 system, this study establishes the corresponding reference radiation qualities by relying on an industrial X-ray tube and uses a free-air ionization chamber to obtain the corresponding correction factors through experiments and simulations to realize absolute air kerma measurements and uncertainty evaluations. In this context, air kerma calibration and associated uncertainty evaluations were performed for the parallel-plate transfer ionization chambers PTW23342 and PTW23344. The results show that the mean energies of the fluence spectra simulated at the X-ray tube voltages of 50, 70, and 100 kV were 26.2, 34.1, and 44.7 keV, respectively. The measured results of the first half-value layer at the three tube voltages were 0.538, 1.146, and 2.190 mmAl. The air kerma of three radiation qualities were 1.487, 1.436, and 1.268 mGy/s. The expanded measurement uncertainty of air kerma by the free-air ionization chamber was 0.94% (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$k = 2$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mo>=</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>), and the expanded uncertainties of the calibration factor in the two transfer ionization chambers were 1.00% (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$k=2$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mo>=</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>) and 0.96% (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$k=2$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mo>=</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>).</p>

Research on the absolute measurement of air kerma in superficial X-ray radiotherapy

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发表日期：

2026年5月19日

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Jun-Xia Bao,
Rui Zhao,
Xiao Zhang,
Jin-Jie Wu,
Wei-Cheng Ding,
Mao-Yuan Chang

摘要

Scar formation results from nonregenerative healing after tissue injury. Complications may occur if the scar grows beyond a certain threshold. Superficial X-ray radiotherapy offers significant advantages as an adjuvant method for surgical treatment of scars. Following the widespread application of the superficial X-ray radiotherapy system SRT-100, accurate dose measurements are key to the implementation of superficial X-ray radiotherapy. In this study, the absorbed dose measured in superficial X-ray radiotherapy was traced to the primary standard based on air kerma. According to this principle, based on the technical parameters of the SRT-100 system, this study establishes the corresponding reference radiation qualities by relying on an industrial X-ray tube and uses a free-air ionization chamber to obtain the corresponding correction factors through experiments and simulations to realize absolute air kerma measurements and uncertainty evaluations. In this context, air kerma calibration and associated uncertainty evaluations were performed for the parallel-plate transfer ionization chambers PTW23342 and PTW23344. The results show that the mean energies of the fluence spectra simulated at the X-ray tube voltages of 50, 70, and 100 kV were 26.2, 34.1, and 44.7 keV, respectively. The measured results of the first half-value layer at the three tube voltages were 0.538, 1.146, and 2.190 mmAl. The air kerma of three radiation qualities were 1.487, 1.436, and 1.268 mGy/s. The expanded measurement uncertainty of air kerma by the free-air ionization chamber was 0.94% ( $k = 2$ $k = 2$ ), and the expanded uncertainties of the calibration factor in the two transfer ionization chambers were 1.00% ( $k=2$ $k = 2$ ) and 0.96% ( $k=2$ $k = 2$ ).