Shih Tian-Yu, Wu Jay, Shih Cheng-Ting, Lee Yao-Ting, Wu Shin-Hua, Yao Chun-Hsu, Hsieh Bor-Tsung
Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan.
Department of Medical Imaging and Radiological Science, Central Taiwan University of Sciences and Technology, Taichung, Taiwan.
PLoS One. 2016 Mar 14;11(3):e0151300. doi: 10.1371/journal.pone.0151300. eCollection 2016.
With advances in therapeutic instruments and techniques, three-dimensional dose delivery has been widely used in radiotherapy. The verification of dose distribution in a small field becomes critical because of the obvious dose gradient within the field. The study investigates the dose distributions of various field sizes by using NIPAM polymer gel dosimeter. The dosimeter consists of 5% gelatin, 5% monomers, 3% cross linkers, and 5 mM THPC. After irradiation, a 24 to 96 hour delay was applied, and the gel dosimeters were read by a cone beam optical computed tomography (optical CT) scanner. The dose distributions measured by the NIPAM gel dosimeter were compared to the outputs of the treatment planning system using gamma evaluation. For the criteria of 3%/3 mm, the pass rates for 5 × 5, 3 × 3, 2 × 2, 1 × 1, and 0.5 × 0.5 cm2 were as high as 91.7%, 90.7%, 88.2%, 74.8%, and 37.3%, respectively. For the criteria of 5%/5 mm, the gamma pass rates of the 5 × 5, 3 × 3, and 2 × 2 cm2 fields were over 99%. The NIPAM gel dosimeter provides high chemical stability. With cone-beam optical CT readouts, the NIPAM polymer gel dosimeter has potential for clinical dose verification of small-field irradiation.
随着治疗仪器和技术的进步，三维剂量递送已在放射治疗中广泛应用。由于射野内明显的剂量梯度，小射野剂量分布的验证变得至关重要。本研究使用NIPAM聚合物凝胶剂量计研究了不同射野大小的剂量分布。该剂量计由5%明胶、5%单体、3%交联剂和5 mM THPC组成。辐照后，延迟24至96小时，然后用锥形束光学计算机断层扫描（光学CT）扫描仪读取凝胶剂量计。使用伽马评估将NIPAM凝胶剂量计测量的剂量分布与治疗计划系统的输出结果进行比较。对于3%/3 mm的标准，5×5、3×3、2×2、1×1和0.5×0.5 cm2射野的通过率分别高达91.7%、90.7%、88.2%、74.8%和37.3%。对于5%/5 mm的标准，5×5、3×3和2×2 cm2射野的伽马通过率超过99%。NIPAM凝胶剂量计具有高化学稳定性。通过锥形束光学CT读数，NIPAM聚合物凝胶剂量计在小射野照射的临床剂量验证方面具有潜力。
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