Liang Li Heng, Tomic Nada, Vuong Te, Aldelaijan Saad, Bekerat Hamed, DeBlois Francois, Seuntjens Jan, Devic Slobodan
Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Medical Physics Unit, McGill University, Montreal, Quebec, Canada.
Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Oncology Department, McGill University, Montreal, Quebec, Canada.
Brachytherapy. 2018 Jan-Feb;17(1):234-243. doi: 10.1016/j.brachy.2017.09.016.
The Papillon technique using 50-kVp soft X-rays to treat rectal adenocarcinomas was developed and clinically implemented in the 1960s. We describe differences between accurate dosimetry and clinical implementation of this technique that is extending from its very inception to date.
A renaissance of the Papillon technique occurred with two recently introduced 50-kVp systems: Papillon+ by Ariane and a custom-made rectal applicator (consisting of a surface applicator inserted into a proctoscope) by iCAD's Xoft Axxent Electronic Brachytherapy (eBT) System (iCad, Inc., Sunnyvale, CA). In contrast to the initial design, we investigated the impact of introducing a plastic lid, which would provide more reproducible and more accurate dose delivery across the rectal adenocarcinoma patient population. We use both parallel-plate chamber and radiochromic film dosimeters to determine differences in basic dosimetry characteristics (beam half-value layers, outputs, percent depth doses, and profiles) between the Xoft Electronic Brachytherapy rectal applicator system with and without the plastic lid in place.
Compared to the open-cone applicator, the proposed applicator with the plastic lid produces a slightly harder (more penetrating) beam quality (half-value layer of 1.4 vs. 1.3-mm Al), but with reduced output (by 33%), and a slightly broader beam with flatness not worse than 3% and symmetry not worse than 2%.
In addition to characterizing beam properties modified by the possible introduction of the plastic cap, we also pointed out and addressed misconceptions in the use of radiochromic films for dose measurements at low-energy photon beams.
20世纪60年代研发并临床应用了采用50千伏峰值软X射线治疗直肠腺癌的帕皮永技术。我们描述了该技术从最初创立至今在精确剂量测定和临床应用方面的差异。
随着最近推出的两个50千伏峰值系统，帕皮永技术得以复兴：阿丽亚娜公司的帕皮永+系统，以及iCAD公司的Xoft Axxent电子近距离放射治疗（eBT）系统定制的直肠施源器（由插入直肠镜的表面施源器组成）（iCad公司，加利福尼亚州桑尼维尔）。与最初设计不同，我们研究了引入塑料盖的影响，这将为直肠腺癌患者群体提供更可重复、更准确的剂量输送。我们使用平行板电离室和放射变色胶片剂量计来确定Xoft电子近距离放射治疗直肠施源器系统在有和没有塑料盖的情况下基本剂量测定特征（束半值层、输出剂量、百分深度剂量和剂量分布）的差异。
与开放式锥形施源器相比，带有塑料盖的拟用施源器产生的束质稍硬（更具穿透性）（半值层为1.4毫米铝，而开放式为1.3毫米铝），但输出剂量降低（降低33%），且束稍宽，平坦度不超过3%，对称性不超过2%。
除了表征可能引入塑料盖对束特性的改变外，我们还指出并解决了在低能光子束剂量测量中使用放射变色胶片时的误解。
