Quantitative evaluation of sternocleidomastoid muscle fibrosis after radiotherapy for nasopharyngeal carcinoma based on mapping technique of MRI / 中华放射学杂志

ABSTRACT

Objective:To investigate the feasibility and clinical value of MRI quantitative evaluation technique in detecting sternocleidomastoid muscle fibrosis in patients with nasopharyngeal carcinoma (NPC) after radiotherapy.Methods:From August 2019 to March 2021, 45 patients with clinically confirmed NPC after radiotherapy and 30 healthy controls who underwent physical examination in Lishui Hospital of Zhejiang University were enrolled in our study. According to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer (RTOG/EORTC) classification criteria of late radiation reactions respectively, the sternocleidomastoid muscle injury in the NPC group was divided into grade Ⅰ, Ⅱ and Ⅲ, which included 8, 32 and 5 patients respectively. All patients underwent T 1 mapping and T 2 mapping imaging of the neck. Firstly, the mapping images of sternocleidomastoid muscle between the two groups were analyzed and compared. Using NUMARIS/4 software of Siemens image post-processing workstation, the region of interest was manually drawn along the edge of sternocleidomastoid muscle at the level of laryngeal chamber in axial mapping diagram. Then, T 1 and T 2 values and the long and short diameters of sternocleidomastoid muscle were measured respectively. Finally, the differences of the parameters between the two groups were compared by independent sample t-test, Spearman rank correlation was used to analyze the relationship between the average T 1 and T 2 values of bilateral sternocleidomastoid muscles and the grade of late radiation injury. Results:Compared with the control group, the shape of sternocleidomastoid muscle in the NPC group was smaller in shape, with irregular edge and uneven increase of T 1 mapping color scale. There was no significant difference in muscle signal in T 2 mapping. The T 1 values of left and right sternocleidomastoid muscles in the NPC group were (1 524.7±97.6) and (1 496.5±93.2) ms respectively, which were significantly higher than those in the normal control group [(1 231.5±85.3) and (1 275.9±90.9) ms] ( P<0.05), and the T 2 values of left and right sternocleidomastoid muscles in the NPC group were (28.4±4.8) and (28.4±3.6) ms respectively, which were lower than those in the normal control group [(30.4±3.5) and (30.4±3.5) ms] ( P<0.05). The long and short diameters of bilateral sternocleidomastoid muscles in the NPC group were shorter than those in the control group ( P<0.05). The average T 1 and T 2 values of bilateral sternocleidomastoid muscles in NPC patients after radiotherapy were (1 510.6±95.4) and (28.4±4.2) ms respectively, The T 1 value was positively correlated with the classification of advanced radiation injury ( r=0.78, P<0.001), and T 2 value was negatively correlated with the level of advanced radiation injury ( r=-0.87, P<0.001). Conclusion:Mapping quantitative evaluation technique can noninvasively and objectively detect and evaluate sternocleidomastoid muscle fibrosis after NPC radiotherapy, which has potential clinical application value.