INTRODUCTION Research in radiation-induced urinary morbidity is limited by lack of guidelines for contouring and dose assessment of the lower urinary tract. Based on literature regarding anatomy, physiology and imaging of the lower urinary tract, this study aimed to provide advice on contouring of relevant sub-structures, reference points and reference dimensions for gynaecological radiotherapy. MATERIAL AND METHODS 210 MRIs for Image-Guided Adaptive Brachytherapy (IGABT) were analysed in 105 locally advanced cervical cancer patients treated with radio(chemo)therapy. Sub-structures (trigone, bladder neck and urethra) were contoured and trigone height (TH) and width (TW) were measured. Internal urethral ostium (IUO) and Posterior inferior border of pubic symphysis-urethra (PIBS-U) points were used to identify proximal and middle/low urethra, respectively. Urethra reference length (URL) was defined as IUO and PIBS-U distance. TH, TW and URL were also quantified on 54 MRIs acquired for External Beam Radiotherapy (EBRT). RESULTS Median absolute differences in volumes and dimensions between first and second IGABT fraction were 0.7 cm3, 4.3 cm3, 0.2 cm, 0.3 cm and 0.2 cm for trigone, bladder neck, TH, TW and URL, respectively. Mean(±SD) TH and TW were 2.7(±0.4)cm and 4.4(±0.4)cm, respectively, with no significant difference (p = 0.15 and p = 0.06, respectively) between IGABT and EBRT. URL was significantly shorter in EBRT than in IGABT MRIs (p < 0.001). CONCLUSIONS This study proposed relevant urinary sub-structures and dose points and showed that standardized contouring is reproducible. Trigone reference dimensions are robust despite different bladder filling and treatment conditions. Standardized contouring and reference points may improve understanding of urinary morbidity.

中文翻译：

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基于 MRI 的妇科放疗下尿路功能亚结构轮廓

引言 由于缺乏下尿路轮廓和剂量评估指南，对辐射引起的泌尿系统疾病的研究受到限制。本研究基于有关下泌尿道解剖学、生理学和影像学的文献，旨在为妇科放疗的相关子结构、参考点和参考尺寸的轮廓绘制提供建议。材料和方法 对 105 名接受放（化）疗的局部晚期宫颈癌患者进行了 210 幅图像引导自适应近距离放射治疗 (IGABT) 的 MRI 分析。对亚结构（三角区、膀胱颈和尿道）进行轮廓绘制，并测量三角区的高度 (TH) 和宽度 (TW)。内尿道口（IUO）和耻骨联合-尿道后下缘（PIBS-U）点用于识别近端和中/低端尿道，分别。尿道参考长度 (URL) 被定义为 IUO 和 PIBS-U 距离。TH、TW 和 URL 也在为外束放射治疗 (EBRT) 获得的 54 次 MRI 上量化。结果 三角区、膀胱颈、TH、TW 和 URL 的第一个和第二个 IGABT 部分的体积和尺寸绝对差异中位数分别为 0.7 cm3、4.3 cm3、0.2 cm、0.3 cm 和 0.2 cm。平均 (±SD) TH 和 TW 分别为 2.7(±0.4)cm 和 4.4(±0.4)cm，IGABT 和 EBRT 之间没有显着差异（分别为 p = 0.15 和 p = 0.06）。EBRT 中的 URL 明显短于 IGABT MRI（p < 0.001）。结论 本研究提出了相关的泌尿亚结构和剂量点，并表明标准化轮廓是可重复的。尽管膀胱充盈和治疗条件不同，但 Trigone 参考尺寸仍然很可靠。