Surface dosimetry for breast radiotherapy in the presence of immobilization cast material
Surface dosimetry for breast radiotherapy in the presence of immobilization cast material
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DOI：
10.1088/0031-9155/56/4/008
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发表时间：
2011-02-21
影响因子：
3.5
通讯作者：
Rosenfeld, Anatoly
中科院分区：
文献类型：
--
作者：
Kelly, Andrew;Hardcastle, Nicholas;Rosenfeld, Anatoly
治愈性乳房放疗通常会给患者带来不同程度的外观损伤。影响美容上可接受的乳房放射治疗的一个问题是大下垂乳房的外部轮廓，这通常会导致皮肤褶皱受到高剂量的照射。通常采用热塑性铸件来固定乳房，以保持设置的可重复性并限制皮肤褶皱的出现。本文旨在确定由于使用热塑性固定铸件而引起的表面剂量变化。使用放射性变色薄膜和 MOSFET 探测器在代表不同皮肤层的水当量深度范围内测量临床混合适形/IMRT 乳房计划的皮肤剂量。放射变色薄膜用作积分剂量计，而 MOSFET 则用于实时剂量测定，以将皮肤剂量的贡献与各个 IMRT 段隔离。将胶片条放置在乳房的不同位置，并使用 MOSFET 测量沿胶片条间隔的 16 个位置的皮肤剂量，以进行数据比较。结果显示，使用 Gafchromic EBT 薄膜和 MOSFET 测量时，存在固定铸件时的皮肤剂量分别增加至不存在固定铸件时的 45.7% 和 62.3%。由于固定模型引起的皮肤剂量的增加随光束入射角度的变化而变化，并且当光束正常入射到模型上时最大。与出口剂量条件相比，入口剂量条件下固定铸件的表面剂量增加更大。
Curative breast radiotherapy typically leaves patients with varying degrees of cosmetic damage. One problem interfering with cosmetically acceptable breast radiotherapy is the external contour for large pendulous breasts which often results in high doses to skin folds. Thermoplastic casts are often employed to secure the breasts to maintain setup reproducibility and limit the presence of skin folds. This paper aims to determine changes in surface dose that can be attributed to the use of thermoplastic immobilization casts. Skin dose for a clinical hybrid conformal/IMRT breast plan was measured using radiochromic film and MOSFET detectors at a range of water equivalent depths representative of the different skin layers. The radiochromic film was used as an integrating dosimeter, while the MOSFETs were used for real-time dosimetry to isolate the contribution of skin dose from individual IMRT segments. Strips of film were placed at various locations on the breast and the MOSFETs were used to measure skin dose at 16 positions spaced along the film strips for comparison of data. The results showed an increase in skin dose in the presence of the immobilization cast of up to 45.7% and 62.3% of the skin dose without the immobilization cast present as measured with Gafchromic EBT film and MOSFETs, respectively. The increase in skin dose due to the immobilization cast varied with the angle of beam incidence and was greatest when the beam was normally incident on the phantom. The increase in surface dose with the immobilization cast was greater under entrance dose conditions compared to exit dose conditions.