Jurković Slaven, Zauhar Gordana, Faj Dario, Radojcić Deni Smilović, Svabić Manda
Department of Radiotherapy and Oncology, University Hospital, Rijeka, Croatia.
Med Dosim. 2010 Spring;35(1):49-52. doi: 10.1016/j.meddos.2009.01.006. Epub 2009 Mar 4.
Intracavitary application of brachytherapy sources followed by external beam radiation is essential for the local treatment of carcinoma of the cervix. Due to very high doses to the central portion of the target volume delivered by brachytherapy sources, this part of the target volume must be shielded while being irradiated by photon beams. Several shielding techniques are available, from rectangular block and standard cervix wedge to more precise, customized step wedge filters. Because the calculation of a step wedge filter's shape was usually based on effective attenuation coefficient, an approach that accounts, in a more precise way, for the scattered radiation, is suggested. The method was verified under simulated clinical conditions using film dosimetry. Measured data for various compensators were compared to the numerically determined sum of the dose distribution around brachytherapy sources and one of compensated beam. Improvements in total dose distribution are demonstrated, using our method. Agreement between calculation and measurements were within 3%. Sensitivity of the method on sources displacement during treatment has also been investigated.
腔内近距离放射治疗源的应用随后进行外照射对于宫颈癌的局部治疗至关重要。由于近距离放射治疗源向靶区中心部分输送的剂量非常高，在光子束照射时，靶区的这一部分必须进行屏蔽。有几种屏蔽技术可供选择，从矩形挡块和标准宫颈楔形挡块到更精确的定制阶梯楔形滤过器。由于阶梯楔形滤过器形状的计算通常基于有效衰减系数，因此建议采用一种更精确考虑散射辐射的方法。该方法在模拟临床条件下使用胶片剂量测定法进行了验证。将各种补偿器的测量数据与近距离放射治疗源周围剂量分布和一个补偿束的数值确定总和进行了比较。使用我们的方法证明了总剂量分布的改善。计算值与测量值之间的一致性在3%以内。还研究了该方法在治疗期间对源位移的敏感性。
