直肠癌 PTV 内可变气腔的剂量学影响。

IF 2 4区 医学 Q3 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Eujin Chan, Simon K Goodall, Robert Finnegan, Paul Moorfoot, Michael Jameson, Leon Dunn
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引用次数: 0

摘要

目的:本研究旨在确定直肠气量变化对治疗计划质量的影响,并随后从治疗期间可接受的直肠气量方面为日常锥束计算机断层扫描(CBCT)评估限制提供信息:方法: 选择了 12 名在计划 CT 中显示 PTV 内有直肠空气的直肠癌患者。方法:选择了 12 例在规划 CT 上显示 PTV 内有直肠空气的直肠癌患者,进行了一项研究,以评估因空气体积扩大而导致的计划质量下降。在每个病例中,气腔容积在膀胱和直肠轮廓变形的同时,使用 3、5、7 和 10 毫米的预定边距进行三维等向膨胀。对骨骼解剖结构施加约束以限制变形。然后,根据扩大的气腔容积重新计算参考计划,为所有 12 名患者生成治疗计划:结果:随着气腔的扩大,与参考计划相比,D98%覆盖率的最大相对变化减少了10.8%±3.5%,而D2%则增加了3.5%±0.9%。气腔的位置对 D98% 的变化有显著影响,扩张了 3 毫米。当气腔容积超过 17 立方厘米时,D98% 覆盖率低于 95%。平均而言,每次扩张后,D2% 覆盖率增加 0.5%。与参考方案相比,在最大扩展时,观察到 102% 和 105% 等剂量的广泛覆盖:结论:气腔容积超过 17 立方厘米可能会降低高剂量 PTV 的覆盖率,同时增加 102% 和 105% 等剂量的覆盖区域。推断出的临床 CBCT 指南建议任何方向的最大阈值为直径 3.2 厘米。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Dosimetric impact of variable air cavity within PTV for rectum cancer.

Purpose: The aim of this study is to determine the impact of rectal air volume changes on treatment plan quality, and subsequently inform daily cone-beam computed tomography (CBCT) evaluation constraints, in terms of acceptable rectal air volume during treatment.

Methods: Twelve rectal cancer patients who exhibited rectal air within the PTV on their planning CT were selected. A study was conducted to evaluate the deterioration in plan quality due to expanding air volume. For each case, the air cavity volume was isotropically expanded in three dimensions using predefined margins of 3, 5, 7, and 10 mm, while deforming bladder and rectum contours. A constraint was applied to the bony anatomy to restrict the deformation. Treatment plans were then generated for all twelve patients by recalculating the reference plan with the expanded air cavity volume.

Results: As the air cavity expanded, the maximum relative change in D98% coverage, compared to the reference plan, decreased by 10.8% ± 3.5%, while the D2% increased by 3.5% ± 0.9%. The positioning of the air cavity notably influenced the D98% variability with the 3 mm expansion. D98% coverage falls below 95% when the air cavity volume exceeds 17 cm3. On average, D2% coverage increased by 0.5% with each expansion. At the largest expansion, extensive coverage of 102% and 105% isodoses was observed compared to the reference plan.

Conclusion: Air cavity volumes above 17 cm3 can potentially degrade the high-dose PTV coverage while increasing the regions covered by the 102% and 105% isodoses. Clinical CBCT guidelines were deduced, recommending a maximum threshold of 3.2 cm in diameter in any direction.

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来源期刊
CiteScore
3.60
自引率
19.00%
发文量
331
审稿时长
3 months
期刊介绍: Journal of Applied Clinical Medical Physics is an international Open Access publication dedicated to clinical medical physics. JACMP welcomes original contributions dealing with all aspects of medical physics from scientists working in the clinical medical physics around the world. JACMP accepts only online submission. JACMP will publish: -Original Contributions: Peer-reviewed, investigations that represent new and significant contributions to the field. Recommended word count: up to 7500. -Review Articles: Reviews of major areas or sub-areas in the field of clinical medical physics. These articles may be of any length and are peer reviewed. -Technical Notes: These should be no longer than 3000 words, including key references. -Letters to the Editor: Comments on papers published in JACMP or on any other matters of interest to clinical medical physics. These should not be more than 1250 (including the literature) and their publication is only based on the decision of the editor, who occasionally asks experts on the merit of the contents. -Book Reviews: The editorial office solicits Book Reviews. -Announcements of Forthcoming Meetings: The Editor may provide notice of forthcoming meetings, course offerings, and other events relevant to clinical medical physics. -Parallel Opposed Editorial: We welcome topics relevant to clinical practice and medical physics profession. The contents can be controversial debate or opposed aspects of an issue. One author argues for the position and the other against. Each side of the debate contains an opening statement up to 800 words, followed by a rebuttal up to 500 words. Readers interested in participating in this series should contact the moderator with a proposed title and a short description of the topic
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