Demanes D J, Rege S, Rodriquez R R, Schutz K L, Altieri G A, Wong T
California Endocurietherapy Cancer Center, Oakland 94609, USA.
Int J Radiat Oncol Biol Phys. 1999 Apr 1;44(1):211-9. doi: 10.1016/s0360-3016(98)00453-2.
This paper describes California Endocurietherapy's (CET) high-dose-rate (HDR) multichannel cylinder, the rationale for its design, procedure for its insertion, and the dosimetry involved in its use. A study was done that compared the doses achieved using the CET multichannel cylinder to the same cylinder if it only had a central channel.
The CET multichannel vaginal cylinder was inexpensively constructed, using parts from various suppliers. After insertion in the patient, the cylinder is affixed to a base plate to prevent displacement. Two sets of orthogonal films (without and with rectal barium) are taken in preparation for digitization of the catheters, bladder, rectal, and pelvic sidewall points. Using HDR brachytherapy planning software, the dose distribution is adjusted to achieve the prescribed dose (5 Gy HDR) 5 mm lateral to the cylinder surface, 5 mm lateral at the proximal parametrial tissue, and 4 mm superior to the vaginal apex. Doses to the bladder and rectum are limited to approximately 85% and 75%, respectively, of the prescribed dose. The plan is optimized on geometric parameters. For dose comparison to treatment using a central channel cylinder, the lateral channels are de-activated, leaving only the central channel activated. Dose points are placed 5 mm laterally and superiorly from the cylinder surface, and the plan is optimized to deliver a uniform dose to the defined dose points. The doses and treatment volumes are statistically compared.
The CET multichannel cylinder allows much better dose control than the central channel cylinder. The multichannel cylinder achieves lower bladder and rectal doses by 14% and 15%, respectively, when compared to the central channel cylinder. By increasing the dwell times of certain dwell positions, the prescription dose is achieved in the vaginal apex and proximal parametrial tissues and along the length of the cylinder.
The multichannel cylinder enables more flexibility in isodose shaping and dose control to various points and structures when compared to the conventional central channel cylinder.
本文描述了加利福尼亚近距离放射治疗公司（CET）的高剂量率（HDR）多通道施源器，阐述了其设计原理、插入步骤以及使用过程中的剂量测定方法。开展了一项研究，比较使用CET多通道施源器与仅具有中央通道的同一施源器所达到的剂量。
CET多通道阴道施源器采用来自不同供应商的部件，成本低廉。插入患者体内后，将施源器固定在底板上以防止移位。拍摄两组正交胶片（有无直肠钡剂），为导管、膀胱、直肠和盆腔侧壁点的数字化做准备。使用HDR近距离放射治疗计划软件，调整剂量分布，以在施源器表面外侧5毫米、近端宫旁组织外侧5毫米以及阴道顶端上方4毫米处达到规定剂量（5 Gy HDR）。膀胱和直肠所接受的剂量分别限制在规定剂量的约85%和75%。根据几何参数对计划进行优化。为了与使用中央通道施源器的治疗进行剂量比较，停用外侧通道，仅激活中央通道。剂量点置于施源器表面外侧和上方5毫米处，对计划进行优化，以便向定义的剂量点提供均匀剂量。对剂量和治疗体积进行统计学比较。
CET多通道施源器比中央通道施源器能实现更好的剂量控制。与中央通道施源器相比，多通道施源器使膀胱和直肠剂量分别降低了14%和15%。通过增加某些驻留位置的驻留时间，在阴道顶端、近端宫旁组织以及施源器长度范围内均可达到处方剂量。
与传统的中央通道施源器相比，多通道施源器在等剂量塑形以及对不同点和结构的剂量控制方面具有更大的灵活性。
