Tang Xueyan, Beltran Chris J, Furutani Keith M, Gilson Graham S, Gustafson Jon, Herman Michael G, Ito Shima, Johnson Jed E, Kruse Jon J, Long Kenneth M, Mundy Daniel W, Remmes Nicholas B, Tasson Ali M, Whitaker Thomas J, Matysiak Witold, Tryggestad Erik J
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota, USA.
J Appl Clin Med Phys. 2025 Jul;26(7):e70156. doi: 10.1002/acm2.70156.
Proton therapy offers precise tumor targeting while minimizing damage to surrounding healthy tissue, making it especially valuable for treating tumors near critical organs and in pediatric patients. However, its success depends on accurate beam delivery, requiring rigorous quality assurance (QA) to maintain treatment precision and effectiveness.
This study aims to standardize the measurement of key aspects of proton therapy delivery, such as gantry and couch isocentricity, spot position accuracy, and spot size consistency. The goal is to enhance the delivery accuracy of proton therapy across various clinical settings, improving patient outcomes.
The QA framework uses the Octopoint phantom, Gafchromic film, and spot position monitor (SPM) log data to evaluate proton beam isocentricity, spot position, and spot size. The Octopoint phantom, made from acrylic, was used with Gafchromic films at various gantry and couch angles to measure isocentricity. MATLAB tools were used to analyze spot positions, and SPM logs provided verification. Sensitivity tests were conducted to assess the system's response to intentional shifts and errors, ensuring alignment with clinical QA standards.
The Octopoint phantom's stepwise two-dimensional (2D) fitting process, validated against film-measured dose profiles, accurately identified beam and ball bearing (BB) centroid locations. Isocentricity tests conducted over 8 months across four gantries demonstrated consistent beam-to-BB radial offsets. The phantom showed excellent repeatability, with a maximum standard deviation of 0.1 mm across various couch-gantry combinations. Sensitivity testing across all axes revealed a strong alignment between intended shifts and measured values. Over the course of a year, film measurements tracked spot position and size consistency, with deviations remaining within acceptable clinical limits. Comparisons with SPM data further confirmed the system's reliability in maintaining beam accuracy across different gantry angles and energy levels.
This study presents a reliable QA framework for ensuring precision in proton therapy delivery. By combining the Octopoint phantom, Gafchromic film analysis, and SPM log file evaluation, we effectively measured isocentricity, spot position accuracy, and spot size stability. The framework demonstrated adaptability across various clinical QA tasks, enhancing the accuracy and safety of proton therapy treatments.
质子治疗能够精确靶向肿瘤，同时将对周围健康组织的损伤降至最低，这使其在治疗靠近关键器官的肿瘤以及儿科患者时具有特别重要的价值。然而，其成功取决于精确的束流传输，这需要严格的质量保证（QA）来维持治疗的精度和有效性。
本研究旨在规范质子治疗传输关键方面的测量，如机架和治疗床的等中心性、束斑位置精度和束斑尺寸一致性。目标是提高质子治疗在各种临床环境中的传输精度，改善患者治疗效果。
QA框架使用Octopoint模体、放射变色胶片和束斑位置监测器（SPM）日志数据来评估质子束的等中心性、束斑位置和束斑尺寸。由丙烯酸制成的Octopoint模体与放射变色胶片一起在不同的机架和治疗床角度下使用，以测量等中心性。使用MATLAB工具分析束斑位置，SPM日志提供验证。进行了灵敏度测试，以评估系统对故意偏移和误差的响应，确保符合临床QA标准。
Octopoint模体的逐步二维（2D）拟合过程，通过与胶片测量的剂量分布进行验证，准确识别了束流和滚珠轴承（BB）的质心位置。在四个机架上进行的为期8个月的等中心性测试表明，束流与BB的径向偏移一致。该模体显示出出色的重复性，在各种治疗床 - 机架组合中最大标准偏差为0.1毫米。在所有轴向上进行的灵敏度测试表明，预期偏移与测量值之间具有很强的一致性。在一年的时间里，胶片测量跟踪了束斑位置和尺寸的一致性，偏差仍在可接受的临床范围内。与SPM数据的比较进一步证实了该系统在不同机架角度和能量水平下维持束流精度的可靠性。
本研究提出了一个可靠的QA框架，以确保质子治疗传输的精度。通过结合Octopoint模体、放射变色胶片分析和SPM日志文件评估，我们有效地测量了等中心性、束斑位置精度和束斑尺寸稳定性。该框架在各种临床QA任务中表现出适应性，提高了质子治疗的准确性和安全性。
