正交千/兆伏级图像评估OSI系统在非共面放疗中的精确性

Evaluation of the accuracy of optical surface imaging system in non-coplanar radiotherapy using orthogonal kV/MV images

目的评估光学体表成像(OSI)系统立体定向放射外科(SRS)算法在单中心非共面治疗多发性脑转移瘤过程中成像的精确性。方法回顾性分析2022年2—4月在四川大学华西医院行单中心非共面放疗的15例多发性脑转移瘤患者和剂量模体的数据。患者和模体均在非共面角度下,分别采用千/兆伏级系统和OSI系统成像,以千/兆伏级成像为参考图像,分析OSI对模体和患者成像的精确性。将OSI系统与千/兆伏级系统之间的差异定义为精确性,其差异绝对值≤1.00 mm/0.50°的百分比定义为阈值合格率。使用Origin软件绘制雷达图和Bland-Altman图做统计分析。结果OSI系统对模体成像时,在左右、头脚、腹背、偏转、翻滚、俯仰六维方向上的平均差异分别为0.03 mm、-0.09 mm、-0.27 mm、0.04°、0.17°、-0.19°,最大值分别为-2.20 mm、-2.30 mm、-1.20 mm、0.60°、-1.00°、-1.00°。OSI系统对15例患者成像时,在六维方向上的平均差异分别为0.44 mm、0.16 mm、-0.20 mm、-0.11°、0.10°、-0.12°,最大值分别为-1.80 mm、2.00 mm、0.90 mm、-0.90°、-0.70°、0.80°。其中平移误差均主要出现在左右和头脚方向。OSI系统对模体和患者成像时,左右方向上的阈值合格率分别为77%和75%,在头脚方向上分别为82%和89%,在六维方向上同时满足±1.00 mm和±0.50°阈值条件的占比分别为57%和56%。结论采用新型SRS算法的OSI系统不能满足多发性脑转移瘤单中心非共面放疗的高精度要求,特别是在左右和头脚方向,不建议将其用于非共面图像引导。

Objective To evaluate the accuracy of the optical surface imaging system(OSI)using stereotactic radiosurgery(SRS)algorithm in single-center non-coplanar treatment of multiple brain metastases.Methods Data of phantom and 15 patients with multiple brain metastases who underwent single-center non-coplanar radiotherapy in West China Hospital of Sichuan University from February to April 2022 were retrospectively analyzed.kV/MV and OSI imaging were used for imaging of the patients and phantoms under the same non-coplanar couch angle,respectively.The accuracy of OSI imaging of the phantoms and patients was evaluated using kV/MV imaging as reference image.The difference between the OSI and kV/MV systems is defined as accuracy,and the percentage of the absolute difference≤1.00 mm in the translational direction or≤0.50°in the rotational direction is defined as the threshold pass rate.Origin software was used to draw radar maps and Bland-Altman plots for statistical analysis.Results When OSI images were used for the phantom imaging,the average differences in six-dimensional directions of lateral,long,vertical,rotational,roll and pitch were 0.03 mm,-0.09 mm,-0.27 mm,0.04°,0.17°and-0.19°,respectively.The maximum values were-2.20 mm,-2.30 mm,-1.20 mm,0.60°,-1.00°,and-1.00°,respectively.When OSI system was utilized for the imaging of 15 patients,the average differences in six-dimensional directions were 0.44 mm,0.16 mm,-0.20 mm,-0.11°,0.10°,and-0.12°,respectively.The maximum values were-1.80 mm,2.00 mm,0.90 mm,-0.90°,-0.70°,and 0.80°,respectively.The translational errors mainly occurred in the lateral and long directions.The qualified rates of the threshold values of the phantoms and patients were 77%and 75%in the lateral direction,82%and 89%in the long direction,respectively.In addition,57%and 56%of patients met the threshold conditions of±1.00 mm and±0.50°in the six-dimensional directions,respectively.Conclusions The OSI system using new SRS algorithm cannot meet the high accuracy requirements of single-center non-coplanar radiotherapy for multiple brain metastasis,especially in the lateral and long directions.It is not recommended for non-coplanar image guidance.