Yen Tsung-Yu, Chuang Kai-Cheng, Fu Hsiao-Mei, Feng Chen-Ju, Lien Ke-Yu, Hsu Shih-Ming
Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei 112304, Taiwan.
Medical Physics and Radiation Measurements Laboratory, National Yang Ming Chiao Tung University, Taipei 112304, Taiwan.
J Clin Med. 2022 Apr 12;11(8):2154. doi: 10.3390/jcm11082154.
To develop a method of estimating surface dose in whole breast irradiation, we used an anthropomorphic phantom with accessories for the simulation of different breast sizes. The surface points, which are measured by TLDs, are set along with two main directions, superior-inferior and medial-lateral. The incident angle between the photon beam and the surface and the doses at 1 cm beneath the surface at every point are assessed by a computerized treatment planning system (cTPS). With the prescription dose of 200 cGy, the average surface doses under tangential irradiation are 97.73 (±14.96) cGy, 99.90 (±10.73) cGy, and 105.26 (±9.21) cGy for large, medium, and small breast volumes, respectively. The surface dose increased in the model of small breast volume without significance ( = 0.39). The linear analysis between surface dose and the incident angle is y = 0.5258x + 69.648, R = 0.7131 (x: incident angle and y: surface dose). We develop the percentage of skin surface dose with reference to a depth of 1 cm (PSDR1cm) to normalize the inhomogeneous dose. The relationship between incident angle and PSDR1cm is y = 0.1894x + 36.021, R = 0.6536 (x: incident angle and y: PSDR1cm) by linear analysis. In conclusion, the surface dose in whole breast irradiation could be estimated from this linear relationship between PSDR1cm and incident angle in daily clinical practice by cTPS. Further in vivo data should be studied to verify this formula.
为开发一种估算全乳照射中表面剂量的方法，我们使用了带有模拟不同乳房大小配件的人体模型。由热释光剂量计（TLD）测量的表面点沿着上下和内外两个主要方向设置。通过计算机治疗计划系统（cTPS）评估光子束与表面之间的入射角以及每个点表面下方1 cm处的剂量。在处方剂量为200 cGy的情况下，对于大、中、小乳房体积，切线照射下的平均表面剂量分别为97.73（±14.96）cGy、99.90（±10.73）cGy和105.26（±9.21）cGy。小乳房体积模型中的表面剂量增加但无统计学意义（P = 0.39）。表面剂量与入射角之间的线性分析为y = 0.5258x + 69.648，R = 0.7131（x：入射角，y：表面剂量）。我们开发了参考1 cm深度的皮肤表面剂量百分比（PSDR1cm）来归一化不均匀剂量。通过线性分析，入射角与PSDR1cm之间的关系为y = 0.1894x + 36.021，R = 0.6536（x：入射角，y：PSDR1cm）。总之，在日常临床实践中，可通过cTPS根据PSDR1cm与入射角之间的这种线性关系估算全乳照射中的表面剂量。应进一步研究体内数据以验证该公式。
