Kench Peter L, Rogers Linda, Esteves Ana, Gorjiara Tina, Mackonis Elizabeth Claridge, Morrell Stephen, McKenzie David R, Suchowerska Natalka
Discipline of Medical Imaging Science and Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, NSW 2006, Australia.
VectorLAB, Radiation Oncology, Chris O'Brien Lifehouse, Missenden Rd, Camperdown, Sydney, NSW 2050, Australia.
Phys Imaging Radiat Oncol. 2020 Nov 28;16:138-143. doi: 10.1016/j.phro.2020.11.003. eCollection 2020 Oct.
Cone Beam Computed Tomography (CBCT) is routinely used in radiotherapy to identify the position of the target volume. The aim of this study was to determine whether the CBCT dose, when followed by the treatment, influences the therapeutic outcomes as determined by in-vitro clonogenic cell survival in a radiobiological experiment.
Human cell lines, four cancer and one normal, were exposed to a 6 MV photon beam, produced by a linear accelerator. For half of each sample, a prior imaging dose was delivered using the on-board CBCT. A sample size of n = 103 was used to achieve statistical power.
The experimental group of cell lines exposed to CBCT imaging prior to treatment exhibited a reduction in mean cancer cell survival of ~17 times (p = 0.02) greater than predicted from the average dose response and equivalent to more than 5% of the therapeutic dose, compared to 11 times greater than predicted for normal cells (n.s.).
The greater than predicted reduction in survival resulting from the additional CBCT dose is consistent with radiation-induced bystander effects.
锥形束计算机断层扫描（CBCT）在放射治疗中常用于确定靶区位置。本研究的目的是在一项放射生物学实验中，确定治疗前进行CBCT扫描时的剂量是否会影响体外克隆形成细胞存活所确定的治疗效果。
将四种癌细胞系和一种正常细胞系暴露于直线加速器产生的6兆伏光子束下。对于每个样本的一半，使用机载CBCT给予预先设定的成像剂量。样本量为n = 103以达到统计学效力。
与正常细胞相比，治疗前接受CBCT成像的实验组癌细胞系平均存活降低约17倍（p = 0.02），大于根据平均剂量反应预测的值，相当于超过5%的治疗剂量，而正常细胞系为大于预测值11倍（无统计学意义）。
额外的CBCT剂量导致的大于预期的存活降低与辐射诱导的旁观者效应一致。
