Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
J Med Imaging Radiat Sci. 2020 Sep;51(3):394-403. doi: 10.1016/j.jmir.2020.04.001. Epub 2020 May 20.
Alignment tattoos on a lax abdomen contribute to misalignment of patients undergoing abdomino-pelvic radiotherapy (RT). The present study was undertaken to assess setup reproducibility in gynecologic cancer patients positioned identically but aligned for treatment to machine isocenter by two different ways.
A prospective study in 35 women treated with radical RT for gynecologic malignancy was undertaken. A RT planning contrast-enhanced computed tomography scan in the supine position using an foot and ankle positioning device was done, and three reference points tattooed on the reference plane, anteriorly at the mons pubis and one on each side laterally at a fixed table top-to-vertical height of 10 cm, whereas a fourth point was tattooed at the xiphoid in the anterior midline. Patients were aligned using either a field center, that is, conventional method (Arm I, n = 18) or by a new setup isocenter (Arm II, n = 17) defined by a cranial offset of 4 cm to the reference plane for daily treatment. Anterior and right lateral digitally reconstructed radiograph setup fields were created at the treatment isocenters and compared with orthogonal megavoltage portal images (PI) taken during initial 3 days of RT and subsequently twice weekly. Setup deviations-rotations and translations were analysed in mediolateral (ML), craniocaudal, and anteroposterior direction. No online and offline corrections were performed. Population systematic error and random error were calculated and planning target volume margins required were estimated using van Herk's formula.
Arm I had 209 PI while Arm II had 188 PI. Patients in arm II had a lesser systematic error in the ML direction. Patients with large pelvic girth (>95 cm) were susceptible for greater movements during treatment, more so in Arm I, major shifts (>5 mm) with respect to Arm II in the ML direction (37% vs. 22%, P = .001). A larger planning target volume expansion was required in Arm I (1.6 cm) compared with Arm II (0.9 cm). The margin expansion required from clinical target volume in anteroposterior direction was about 0.6 cm and about a cm in the craniocaudal direction in both the arm.
Alignment of patient with anterior tattoo at the relatively immobile portion of lower abdomen (mons pubis) Arm II (setup) is superior to a more cranial location over the flabby abdomen during radiation treatment.
在腹部松弛的情况下，对齐纹身会导致接受腹盆部放射治疗（RT）的患者错位。本研究旨在评估通过两种不同方法将治疗机器等中心点对齐的妇科癌症患者的摆位重复性。
对 35 名接受根治性 RT 治疗妇科恶性肿瘤的女性进行前瞻性研究。在仰卧位使用足踝定位装置进行 RT 计划增强 CT 扫描，并在参考平面上标记三个参考点，分别在前耻骨处、外侧各一个，固定在台面到垂直高度为 10cm 处，而第四个点标记在前中线胸骨处。患者使用场中心（传统方法，Arm I，n=18）或通过新的设定等中心点（Arm II，n=17）进行对齐，后者在参考平面上向颅侧偏移 4cm 进行日常治疗。在治疗等中心点创建前后和右侧数字重建射野图像（DRR），并与初始 RT 第 3 天拍摄的正交兆伏门控图像（PI）进行比较，随后每周两次进行比较。分析了中侧（ML）、头尾和前后方向的摆位偏差-旋转和平移。未进行在线和离线校正。使用 van Herk 公式计算了人群系统误差和随机误差，并估计了计划靶区体积所需的扩展。
Arm I 有 209 个 PI，而 Arm II 有 188 个 PI。Arm II 的患者在 ML 方向上的系统误差较小。骨盆周长较大（>95cm）的患者在治疗过程中更容易发生较大的运动，在 Arm I 中更明显，与 Arm II 相比，在 ML 方向上的主要偏移（>5mm）（37%对 22%，P=0.001）。与 Arm II（0.9cm）相比，Arm I 所需的计划靶区体积扩展更大（1.6cm）。前后方向从临床靶区到靶区的扩展约为 0.6cm，头脚方向约为 1cm。
将患者的纹身与下腹部相对固定的下部（耻骨）对齐（Arm II （设定））优于在放射治疗期间在松弛的腹部上进行更靠颅侧的位置对齐。
