目的:总结我们使用自动束保持(ABH)技术进行全身前列腺立体定向身体放射治疗(SBRT)的经验,并评估10毫米(mm)直径的ABH耐受性。方法:分析了2018年1月3日至2021年3月使用ABH技术治疗的32例患者(160个分数)。治疗期间,每20度机架旋转获取kV图像,以可视化前列腺内的3-4个金基准以跟踪目标运动。如果基准中心落在公差圆(直径=10mm)之外,光束自动关闭重新成像和重新定位。记录了波束保持的数量和沙发平移运动的幅度。通过移动计划的等中心来计算与帧内运动的剂量学差异。主要结果:沙发垂直运动幅度(平均值±SD),纵向和横向分别为-0.7±2.5、1.4±2.9和-0.1±0.9mm,分别。对于大多数馏分(77.5%),没有必要纠正。需要一个的分数的数量,两个,或三次修正为15.6%,5.6%和1.3%,分别。在49项更正中,主要在垂直(31%)和纵向(39%)方向观察到大于3mm的沙发移位;在2%和6%的病例中,相应的沙发移位大于5mm.剂量测定,临床目标体积(CTV)的100%覆盖率下降不到2%(-1±2%),而PTV的覆盖率下降不到10%(-10±6%)。膀胱剂量,肠和尿道趋于增加(膀胱:ΔD10%:184±466cGy,ΔD40%:139±241cGy,肠道:ΔD1cm3:54±129cGy;ΔD5cm3:44±116cGy,尿道:ΔD0.03cm3:1±1%)。直肠剂量趋于减少(直肠:ΔD1cm3:-206±564cGy,ΔD10%:-97±426cGy;ΔD20%:-50±251cGy)。意义:随着从常规分级强度调制放射治疗到SBRT的转变,用于局部前列腺癌治疗,必须确保剂量递送在空间上是准确的,以便适当覆盖目标体积并限制剂量到周围器官.可以使用对基准标记和ABH成像的触发成像来实现帧内运动监测,以允许针对过度运动的重新成像和重新定位。
Objective: To summarize our institutional prostate stereotactic body radiation therapy (SBRT) experience using auto beam hold (ABH) technique for intrafractional prostate motion and assess ABH tolerance of 10-millimeter (mm) diameter.Approach: Thirty-two patients (160 fractions) treated using ABH technique between 01/2018 and 03/2021 were analyzed. During treatment, kV images were acquired every 20-degree gantry rotation to visualize 3-4 gold fiducials within prostate to track target motion. If the fiducial center fell outside the tolerance circle (diameter = 10 mm), beam was automatically turned off for reimaging and repositioning. Number of beam holds and couch translational movement magnitudes were recorded. Dosimetric differences from intrafractional motion were calculated by shifting planned isocenter.Main Results: Couch movement magnitude (mean ± SD) in vertical, longitudinal and lateral directions were -0.7 ± 2.5, 1.4 ± 2.9 and -0.1 ± 0.9 mm, respectively. For most fractions (77.5%), no correction was necessary. Number of fractions requiring one, two, or three corrections were 15.6%, 5.6% and 1.3%, respectively. Of the 49 corrections, couch shifts greater than 3 mm were seen primarily in the vertical (31%) and longitudinal (39%) directions; corresponding couch shifts greater than 5 mm occurred in 2% and 6% of cases. Dosimetrically, 100% coverage decreased less than 2% for clinical target volume (CTV) (-1 ± 2%) and less than 10% for PTV (-10 ± 6%). Dose to bladder, bowel and urethra tended to increase (Bladder: ΔD10%:184 ± 466 cGy, ΔD40%:139 ± 241 cGy, Bowel: ΔD1 cm3:54 ± 129 cGy; ΔD5 cm3:44 ± 116 cGy, Urethra: ΔD0.03 cm3:1 ± 1%). Doses to the rectum tended to decrease (Rectum: ΔD1 cm3:-206 ± 564 cGy, ΔD10%:-97 ± 426 cGy; ΔD20%:-50 ± 251 cGy).Significance: With the transition from conventionally fractionated intensity modulated radiation therapy to SBRT for localized prostate cancer treatment, it is imperative to ensure that dose delivery is spatially accurate for appropriate coverage to target volumes and limiting dose to surrounding organs. Intrafractional motion monitoring can be achieved using triggered imaging to image fiducial markers and ABH to allow for reimaging and repositioning for excessive motion.