Adams Quentin E, Xu Jinghzu, Breitbach Elizabeth K, Li Xing, Enger Shirin A, Rockey William R, Kim Yusung, Wu Xiaodong, Flynn Ryan T
Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242.
Medical Physics Unit, McGill University, 1650 Cedar Ave, Montreal, Quebec H3G 1A4, Canada.
Med Phys. 2014 May;41(5):051703. doi: 10.1118/1.4870441.
To present a novel needle, catheter, and radiation source system for interstitial rotating shield brachytherapy (I-RSBT) of the prostate. I-RSBT is a promising technique for reducing urethra, rectum, and bladder dose relative to conventional interstitial high-dose-rate brachytherapy (HDR-BT).
A wire-mounted 62 GBq(153)Gd source is proposed with an encapsulated diameter of 0.59 mm, active diameter of 0.44 mm, and active length of 10 mm. A concept model I-RSBT needle/catheter pair was constructed using concentric 50 and 75 μm thick nickel-titanium alloy (nitinol) tubes. The needle is 16-gauge (1.651 mm) in outer diameter and the catheter contains a 535 μm thick platinum shield. I-RSBT and conventional HDR-BT treatment plans for a prostate cancer patient were generated based on Monte Carlo dose calculations. In order to minimize urethral dose, urethral dose gradient volumes within 0-5 mm of the urethra surface were allowed to receive doses less than the prescribed dose of 100%.
The platinum shield reduced the dose rate on the shielded side of the source at 1 cm off-axis to 6.4% of the dose rate on the unshielded side. For the case considered, for the same minimum dose to the hottest 98% of the clinical target volume (D(98%)), I-RSBT reduced urethral D(0.1cc) below that of conventional HDR-BT by 29%, 33%, 38%, and 44% for urethral dose gradient volumes within 0, 1, 3, and 5 mm of the urethra surface, respectively. Percentages are expressed relative to the prescription dose of 100%. For the case considered, for the same urethral dose gradient volumes, rectum D(1cc) was reduced by 7%, 6%, 6%, and 6%, respectively, and bladder D(1cc) was reduced by 4%, 5%, 5%, and 6%, respectively. Treatment time to deliver 20 Gy with I-RSBT was 154 min with ten 62 GBq (153)Gd sources.
For the case considered, the proposed(153)Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%-44% if the clinician allows a urethral dose gradient volume of 0-5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed (153)Gd-based I-RSBT technique in reasonable treatment times.
介绍一种用于前列腺间质旋转屏蔽近距离放射治疗（I-RSBT）的新型针、导管和辐射源系统。相对于传统的间质高剂量率近距离放射治疗（HDR-BT），I-RSBT是一种有前景的技术，可降低尿道、直肠和膀胱的剂量。
提出一种线装62GBq（153）钆源，其封装直径为0.59mm，活性直径为0.44mm，活性长度为10mm。使用同心的50和75μm厚的镍钛合金（镍钛诺）管构建了一个概念模型I-RSBT针/导管对。针的外径为16号（1.651mm），导管包含一个535μm厚的铂屏蔽。基于蒙特卡罗剂量计算，为一名前列腺癌患者生成了I-RSBT和传统HDR-BT治疗计划。为了使尿道剂量最小化，允许尿道表面0-5mm范围内的尿道剂量梯度体积接受低于规定剂量100%的剂量。
铂屏蔽将源的屏蔽侧离轴1cm处的剂量率降低到未屏蔽侧剂量率的6.4%。对于所考虑的病例，对于相同的临床靶体积最热的98%的最小剂量（D（98%）），对于尿道表面0、1、3和5mm范围内的尿道剂量梯度体积，I-RSBT分别将尿道D（0.1cc）降低到低于传统HDR-BT的29%、33%、38%和44%。百分比相对于规定剂量100%表示。对于所考虑的病例，对于相同的尿道剂量梯度体积，直肠D（1cc）分别降低了7%、6%、6%和6%，膀胱D（1cc）分别降低了4%、5%、5%和6%。使用十个62GBq（153）钆源进行I-RSBT输送20Gy的治疗时间为154分钟。
对于所考虑的病例，如果临床医生允许尿道周围0-5mm的尿道剂量梯度体积接受低于规定剂量的剂量，则所提出的基于（153）钆的I-RSBT系统有可能将尿道剂量相对于HDR-BT降低29%-44%。为了在合理的治疗时间内实施所提出的基于（153）钆的I-RSBT技术，多源方法是必要的。
