目的:比较鼻咽癌精确放疗中应用KV级锥形束CT(kV-CBCT)不同配准方法对治疗中配准偏差的影响，为鼻咽癌图像引导下放疗选择更优的配准方法提供依据。方法：随机选取2021年02月-2021年10月在我科实施精确放疗的鼻咽癌患者10例，应用E1ekta Synergy^TMIGRT加速器机载kV-CBCT对其进行位置验证，首次治疗前及之后的每周一次扫描验证，将其与定位时图像进行配准。每次CBCT图像均分别进行骨性与灰度配准，并记录自动配准的结果，最后由医生、物理师共同参与手动调整摆位误差值，确认后发送到机器进行治疗。将两种不同配准方式的结果跟医生确认后的标准数值对比得到各自偏差值再行分析。结果：骨性配准相对于灰度配准在面背方向（Z）相对偏差更小（0.588±0.473 vs 0.885±0.670，P<0.05）；以1 mm偏差值为界区分配准优劣，同样面背方向（Z）骨性配准优的比例高于灰度配准（88% vs 70%，P<0.05）。而左右（X）、头脚（Y）方向差异无统计学意义（P均>0.05）。结论：鼻咽癌精确放疗三维验证时，应用CBCT图像配准中应以骨性配准为主，同时查看GTV或PTV的配准结果，从冠状位、矢状位和横断位等多方面比对微调后才能得到相对满意的配准结果。

关键词: 鼻咽肿瘤；放射治疗；图像引导放疗；锥形束CT；图像配准；线性误差

Objective: To compare the effects of different registration methods using kilovoltage cone-beam CT (kV-CBCT) in precise radiotherapy for nasopharyngeal carcinoma (NPC), and to provide evidence for selecting the optimal registration method for image-guided radiotherapy for NPC. Methods: Ten randomly selected patients with NPC who underwent precise radiotherapy in our department from February 2021 to October 2021 were included. The E1ekta SynergyTM IGRT accelerator with onboard kV-CBCT was used for position verification. CBCT scans were performed before the initial treatment and weekly thereafter, and registered with the reference images. Each CBCT image was registered using both bony and grayscale registration methods, and the results of automatic registration were recorded. The manual adjustment of positioning errors was performed by both the physician and physicist, and the confirmed adjustments were sent to the machine for treatment. The deviation values of each registration method were analyzed by comparing them with the standard values confirmed by the physician. Results: The bony registration method showed smaller relative deviations in the anterior-posterior direction (Z) compared to the grayscale registration method (0.588±0.473 vs 0.885±0.670, P<0.05). Using a 1 mm deviation as the threshold to distinguish registration quality, the bony registration method had a higher proportion of optimal registrations than the grayscale registration method in the anterior-posterior direction (Z) (88% vs 70%, P<0.05). There was no statistically significant difference in the left-right (X) and superior-inferior (Y) directions (P>0.05). Conclusion: In three-dimensional verification of precise radiotherapy for NPC, bony registration should be prioritized in CBCT image registration. It is recommended to evaluate the registration results of the gross tumor volume (GTV) or planning target volume (PTV) from multiple perspectives, such as coronal, sagittal, and transverse views, and make fine adjustments to achieve relatively satisfactory registration results.

Keywords: Nasopharyngeal carcinoma; Radiotherapy; Image-guided radiotherapy; Cone-beam CT; Image registration; Linear error.

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