去伪影算法对头颈部肿瘤患者钛板植入术后放疗的剂量影响

目的:通过去伪影前、后CT各组织的CT值和剂量比较,探讨金属伪影消减(metal artifact reduction,MAR)算法对头颈部钛板植入术后放疗计划的剂量影响.方法:选择上海交通大学医学院附属第九人民医院2019年10月-2020年3月收治的头颈部肿瘤患者20例,均为术中植入钛板进行下颌骨重建患者.在模拟定...

Impact of metal artifact reduction algorithms on dosimetry of postoperative radiotherapy for head and neck cancer patients with titanium plate implantation

PURPOSE: To explore the value of metal artifact reduction(MAR) algorithms on radiotherapy dose calculation by comparing the CT values and radiation doses before and after MAR. METHODS: Twenty head and neck cancer patients admitted to Shanghai Ninth People's Hospital,Shanghai Jiao Tong University School of Medicine during Oct 2019 to March 2020 were selected. All of them underwent mandibular reconstruction with titanium plate implantation before radiotherapy. Their CT simulation scans and the images after MAR were collected. The organs at risk(OAR) were contoured by auto-segmentation software on CT images after MAR and the contouring was duplicated to original CT scan, with both the CT values of OAR recorded. Two 40 cm×40 cm opposite irradiated fields were planned with anterior margin of the second cervical vertebra set as central point, and then dose calculations were collected for paired t test with SPSS 21.0 software package. RESULTS: The average CT values of all the organs and tissue changed significantly after MAR based on MAR algorithms, compared with the original planning CT images. The average rate of change was 26.29%, with a range from 5.04%-127.19%.There was significant difference in average CT values of organs between before and after MAR except for larynx, bilateral parotid glands, pharyngeal tonsil, pituitary gland and thyroid gland. There was no significant difference in radiation dose change between the two groups, with the exception of oral cavity. CONCLUSIONS: MAR algorithms can effectively reduce metal artifacts on CT scans, but the CT values were also significantly changed, which inevitably influenced the dose calculation. It is suggested that CT images after MAR could be performed as references for target area contouring, but not suitable for dose calculation for planning of radiotherapy.