Rangarajan Ramya
Department of Radiation Oncology, Government Royapettah Hospital, India.
Rep Pract Oncol Radiother. 2018 Jan-Feb;23(1):57-60. doi: 10.1016/j.rpor.2017.12.006. Epub 2018 Jan 12.
The aim of the study is to evaluate the differences in dosimetry between tandem-ovoid and tandem-ring gynaecologic brachytherapy applicators in image based brachytherapy.
Traditionally, tandem ovoid applicators were used to deliver dose to tumor in intracavitary brachytherapy. Tandem-ring, tandem-cylinder and hybrid intracavitary, interstitial applicators are also used nowadays in cervical cancer brachytherapy.
100 CT datasets of cervical cancer patients (stage IB2 - IIIB) receiving HDR application (50 tandem-ovoid and 50 tandem-ring) were studied. Brachytherapy was delivered using a CT-MRI compatible tandem-ovoid (50 patients) and a tandem-ring applicator (50 patients). DVHs were calculated and D2cc was recorded for the bladder and rectum and compared with the corresponding ICRU point doses. The point B dose, the treated volume, high dose volume and the treatment time were recorded and compared for the two applicators.
The mean D2cc of the bladder with TR applicator was 6.746 Gy. TO applicator delivered a mean D2cc of 7.160 Gy to the bladder. The mean ICRU bladder points were 5.60 and 5.63 Gy for TR and TO applicator, respectively. The mean D2cc of the rectum was 4.04 Gy and 4.79 Gy for TR and TO applicators, respectively. The corresponding ICRU point doses were 5.10 Gy and 5.66 Gy, respectively.
The results indicate that the OAR doses assessed by DVH criteria were higher than ICRU point doses for the bladder with both tandem-ovoid and tandem-ring applicators whereas DVH based dose was lower than ICRU dose for the rectum. The point B dose, the treated volume and high dose volume was found to be slightly higher with the tandem-ovoid applicator. The mean D2cc dose for the bladder and rectum was lower with tandem-ring applicators. The clinical implication of the above dosimetric differences needs to be evaluated further.
本研究旨在评估基于影像的近距离放射治疗中，串联卵形施源器和串联环形妇科近距离放射治疗施源器之间的剂量学差异。
传统上，串联卵形施源器用于腔内近距离放射治疗中向肿瘤输送剂量。如今，串联环形、串联圆柱形以及混合腔内、组织间施源器也用于宫颈癌近距离放射治疗。
研究了100例接受高剂量率（HDR）治疗（50例使用串联卵形施源器，50例使用串联环形施源器）的宫颈癌患者（IB2期 - IIIB期）的CT数据集。使用与CT - MRI兼容的串联卵形施源器（50例患者）和串联环形施源器（50例患者）进行近距离放射治疗。计算剂量体积直方图（DVH），记录膀胱和直肠的D2cc，并与相应的国际辐射单位与测量委员会（ICRU）点剂量进行比较。记录并比较两种施源器的B点剂量、治疗体积、高剂量体积和治疗时间。
串联环形施源器治疗时膀胱的平均D2cc为6.746 Gy。串联卵形施源器使膀胱的平均D2cc为7.160 Gy。串联环形和串联卵形施源器的ICRU膀胱点平均剂量分别为5.60 Gy和5.63 Gy。串联环形和串联卵形施源器治疗时直肠的平均D2cc分别为4.04 Gy和4.79 Gy。相应的ICRU点剂量分别为5.1 Gy和5.66 Gy。
结果表明，对于膀胱，使用串联卵形和串联环形施源器时，根据DVH标准评估的危及器官（OAR）剂量高于ICRU点剂量，而对于直肠，基于DVH的剂量低于ICRU剂量。发现串联卵形施源器的B点剂量、治疗体积和高剂量体积略高。串联环形施源器治疗时膀胱和直肠 的平均D2cc剂量较低。上述剂量学差异的临床意义需要进一步评估。
