Lim Tze Yee, Luo Dershan, Moradi-Kurdestany Jamshid, Wang Xin, Tailor Ramesh
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, United States.
Department of Radiation Oncology, Mercy Coletta Cancer Center, Oklahoma City, OK 73120, United States.
Br J Radiol. 2025 Aug 1;98(1172):1298-1304. doi: 10.1093/bjr/tqaf107.
Kilovoltage x-ray therapy, which includes superficial x-rays and orthovoltage x-rays, is particularly suited for treatments near the skin surface. Radiation dose deposition at depth is typically characterized by percentage depth dose (PDD) curves. However, PDD data are difficult to obtain in kilovoltage x-ray therapy, hence clinics often rely on British Journal of Radiology Supplement 25 (BJR-25) archival data. This study measured PDD for different energies and field sizes on the Xstrahl 300 kilovoltage x-ray therapy unit for comparison with BJR-25 data.
We irradiated EBT3 film in water using different energy and field size combinations, then, compared the acquired PDD curves with BJR-25 data. We used 75, 125, and 250 kVp beams, for 10 × 10 cm2 open field, 4 × 4 cm2 closed-ended square applicator, and open-ended circular applicators of 1.5, 2.0, 2.8, and 4.7 cm diameter.
PDD for different energies and field sizes on the Xstrahl 300 kilovoltage x-ray therapy unit agreed well with BJR-25 data. The average difference between measured and BJR-25 data was -0.3 ± 1.8%; 85.9% of the individual local differences were within ±3%, 94.8% within ±4%, and 99.5% within ±5%.
The PDD curves presented here, together with BJR-25 data, can serve as useful comparison datasets for the commissioning of kilovoltage x-ray machines.
Our film-based measurement technique provides high spatial resolution PDD datapoints for a modern kilovoltage x-ray unit, adding to the limited published data in the kilovoltage energy range.
千伏级X射线治疗，包括浅表X射线和深部X射线，特别适用于皮肤表面附近的治疗。深度处的辐射剂量沉积通常用百分深度剂量（PDD）曲线来表征。然而，在千伏级X射线治疗中很难获得PDD数据，因此临床通常依赖《英国放射学杂志增刊25》（BJR - 25）的存档数据。本研究在Xstrahl 300千伏级X射线治疗装置上测量了不同能量和射野大小的PDD，以便与BJR - 25数据进行比较。
我们使用不同能量和射野大小组合在水中照射EBT3胶片，然后将获取的PDD曲线与BJR - 25数据进行比较。我们使用了75、125和250 kVp的射线束，用于10×10 cm²开放射野、4×4 cm²封闭式方形限光筒以及直径为1.5、2.0、2.8和4.7 cm的开放式圆形限光筒。
Xstrahl 300千伏级X射线治疗装置上不同能量和射野大小的PDD与BJR - 25数据吻合良好。测量数据与BJR - 25数据的平均差异为 -0.3±1.8%；85.9%的个体局部差异在±3%以内，94.8%在±4%以内，99.5%在±5%以内。
这里呈现的PDD曲线以及BJR - 25数据，可作为千伏级X射线机调试的有用比较数据集。
我们基于胶片的测量技术为现代千伏级X射线装置提供了高空间分辨率的PDD数据点，补充了千伏能量范围内有限的已发表数据。
