[论文解读] Clinical Validation of two Surface Imaging Systems for Patient Positioning in Percutaneous Radiotherapy

Manfred Wiencierz, Kathrin Kruppa+1 more|arXiv (Cornell University)|Feb 11, 2016

Advanced Radiotherapy Techniques参考文献 18被引用 5

一句话总结

本研究临床验证了两种放射治疗体表成像系统——Catalyst（C-Rad）和AlignRT（VisionRT）——在螺旋断层放疗中患者摆位的应用。与传统皮肤标记相比，两种系统均能减少摆位误差，尤其在盆腔和胸部区域表现更优，其中AlignRT因覆盖更广的体表面积而展现出更高的准确性，尽管统计变异性仍是临床安全边界设定的挑战。

ABSTRACT

Precise patient positioning and thus precise positioning of the planning target volume (PTV) is a prerequisite for effective treatment in percutaneous radiation therapy. Conventional imaging modalities used to ensure exact positioning for treatment typically involve additional radiation exposure of the patient. A different approach to patient alignment without additional exposure is provided by optical 3D surface scanning and registration systems. We investigated two systems Catalyst and AlignRT, which allowed us to generate and validate surface images of 50 patients undergoing irradiation on a Tomotherapy system. We compared the positions proposed by these two surface imaging systems (SIS) with the actual adjustments in patient positions made on the basis of MVCT scans. With the two SIS, the surface of every single patient was repeatedly recorded throughout treatment. In addition, we performed a systematic analysis of both systems using a body phantom. At least 10 surface images were available from each patient included in the analysis. The large number of patients allowed us to subdivide the study population into three groups by body region treated: head & neck, chest, and pelvic. The results for each of these three body regions were separately analyzed. Thus, the focus of our investigation is on body regions registered with the two systems rather than tumor entities. For AlignRT, for instance, we found an improvement in positioning for the Pelvic region of 0.9mm in 75% and 6.4mm in 95% of the collected data in comparison to conventional marker alignment. The two systems were most accurate in the head & neck region, where conventional mask alignment is already sufficiently accurate. The other two body regions, pelvic and chest, might benefit from positioning by SIS. But for both systems there is still a need for improvement to reduce statistical variation.

研究动机与目标

• 评估两种体表成像系统（Catalyst与AlignRT）在经皮放疗中患者摆位的准确性。
• 比较基于SIS的摆位与传统皮肤标记对齐及MVCT引导下的修正结果。
• 评估系统在不同解剖区域（头颈部、胸部、盆腔）的表现。
• 识别SIS测量中系统性误差与变异性来源。
• 确定SIS在常规放疗中临床可行性和安全边界。

提出的方法

• 在Tomotherapy系统上，体表成像系统（SIS）在治疗分次过程中采集患者体表的三维扫描。
• 每位患者的体表在多个治疗分次中被多次扫描（≥10次），以进行纵向分析。
• 将SIS结果与基于MVCT扫描获得的患者摆位修正结果（金标准）进行对比。
• 使用体模在受控条件下系统评估SIS性能。
• 参考体表为计划CT重建的体表轮廓（外部CT参考）或SIS生成的内部体表（内部光学参考）。
• 统计分析包括在各个方向平移与旋转位移中，摆位偏差的百分位数（P75、P90、P95）

实验结果

研究问题

• RQ1 Catalyst与AlignRT在患者摆位中的准确性与传统皮肤标记对齐相比如何？
• RQ2 在不同解剖区域中，SIS获取的摆位修正结果中系统性误差与随机误差分别是什么？
• RQ3 体表覆盖范围是否影响SIS在纵向（y轴）与旋转摆位中的准确性？
• RQ4 SIS能否将患者摆位不确定性降低至临床安全边界以下，特别是在未使用头罩固定区域如胸部与盆腔？
• RQ5 参考体表类型（外部CT参考 vs. 内部光学参考）如何影响SIS配准的准确性？

主要发现

• 对于盆腔区域患者，与传统标记对齐相比，AlignRT在P75百分位数上将摆位误差减少了0.9 mm，在P95百分位数上减少了6.4 mm。
• AlignRT在所有三个解剖区域中均表现出更优的准确性，尤其在盆腔与胸部区域，归因于更广的体表覆盖。
• Catalyst在纵向（y轴）摆位中表现出更高的系统性误差，可能由于体表覆盖面积有限，影响整体准确性。
• 两种系统在P75百分位数内均处于可接受的临床边界范围内，但P95百分位数超过了典型计划安全边界，表明仍存在残余变异性。
• 使用外部CT重建的参考体表相比内部SIS参考体表能提升准确性，尽管其在常规工作流程中实用性较低。
• 头颈部患者从SIS中获益最少，因为传统头罩固定已能提供极高的摆位准确性。