Department of Radiation Oncology, Memorial University Medical Center, Savannah, Georgia 31404, USA.
Med Phys. 2013 Sep;40(9):091716. doi: 10.1118/1.4819825.
Measurements were taken with optically stimulated luminescence dosimeters (OSLDs) and with RTQA2 radiochromic film to evaluate the use of each for in vivo dosimetry with intraoperative radiotherapy of the breast.
Nonlinear calibration curves were established for OSLDs and RTQA2 radiochromic film using the Intrabeam 50 kVp source. Measurements were taken in a water phantom and compared to absolute dose measurements taken with an ionization chamber to investigate the characteristics of both types of dosimeters, including energy response and radiative absorption. In vivo readings were taken on the skin and in the tumor cavity using OSLDs and RTQA2 radiochromic film for 10 patients and 20 patients respectively. A prescription of 20 Gy to the surface of the applicator was used for all in vivo measurements in this study.
OSLDs were found to have an approximate uncertainty of ± 7% for readings near the surface of the applicator and ± 17% for readings at distances typical to the skin. The radiative absorption by OSLD was negative, indicating that this type of dosimeter absorbs less radiation than water in the targeted intraoperative radiotherapy energy range. RTQA2 film exhibited no energy dependence and all film readings were within ± 8% of the delivered dose. The maximum radiative absorption in film was 8.5%. Radiochromic film measurements were found to be on average 18.2 ± 3.3 Gy for the tumor cavity and 2.1 ± 0.8 Gy for positions on the skin superior and inferior to the Intrabeam applicator. Average cavity measurements taken with OSLDs were 15.9 ± 3.9 Gy and average skin doses were 1.4 ± 0.8 Gy.
OSLDs produce results with an uncertainty comparable to other dosimeters near the surface of the applicator but the uncertainty increases to an unacceptably high level with distance from the applicator. RTQA2 radiochromic film is shown to be accurate both at the surface of the applicator and at distances of 1-2 cm.
使用光激励发光剂量计（OSLD）和 RTQA2 光致变色胶片进行测量，以评估在术中放疗的乳房内剂量测定中使用这两种方法的效果。
使用 Intrabeam 50 kVp 源建立 OSLD 和 RTQA2 光致变色胶片的非线性校准曲线。在水模体中进行测量，并与电离室进行的绝对剂量测量进行比较，以研究两种剂量计的特性，包括能量响应和辐射吸收。分别在 10 名患者和 20 名患者的皮肤和肿瘤腔内使用 OSLD 和 RTQA2 光致变色胶片进行体内读数。本研究中所有体内测量的应用器表面处方剂量均为 20 Gy。
OSLD 对接近应用器表面的读数的不确定度约为±7%，对距离皮肤典型位置的读数的不确定度约为±17%。OSLD 的辐射吸收为负值，表明这种类型的剂量计在目标术中放疗能量范围内吸收的辐射比水少。RTQA2 胶片没有能量依赖性，所有胶片读数均在输送剂量的±8%以内。胶片的最大辐射吸收为 8.5%。RTQA2 胶片的测量值平均为肿瘤腔内 18.2±3.3 Gy，应用器上方和下方皮肤位置为 2.1±0.8 Gy。OSLD 的平均腔测量值为 15.9±3.9 Gy，平均皮肤剂量为 1.4±0.8 Gy。
OSLD 在靠近应用器表面的区域产生的结果与其他剂量计的不确定度相当，但随着与应用器的距离增加，不确定性会增加到不可接受的水平。RTQA2 光致变色胶片在应用器表面和 1-2 cm 距离处均显示出准确性。
