Liu Mengke, Li Bin, Hao Kun, Zhang Yan, Hao Qi, Li Xingpeng, Wang Rengui
Department of Radiology, Beijing Shijitan Hospital, Capital Medical University, Beijing, China.
Department of MRI, Beijing Shijitan Hospital, Capital Medical University, Beijing, China.
Quant Imaging Med Surg. 2023 Aug 1;13(8):4839-4851. doi: 10.21037/qims-22-795. Epub 2023 Jun 5.
The staging of primary lower extremity lymphedema (LEL) is difficult yet vital in clinical work, and magnetic resonance imaging (MRI) can be used for quantitative assessment of primary LEL due to its high resolution for soft tissues. In this study, we evaluated the value of MRI-based soft tissue area measurements for staging primary LEL.
A total of 90 consecutive patients with clinically diagnosed primary lower limb lymphoedema from January 2017 to December 2019 in Beijing Shijitan Hospital were enrolled retrospectively. Short time inversion recovery (STIR) sequence was applied to measure the total, muscle, bone, and subcutaneous areas in the upper 1/3 level of the bilateral lower calf. The difference between the affected and unaffected calf regarding the subcutaneous area was obtained, and (subcutaneous area)/(bone area) and (subcutaneous area)/(muscle area) were calculated. According to the International Society of Lymphology (ISL) clinical staging standard established in 2020, all patients were divided into stages I, II, and III, accordingly. Statistical analysis was performed to determine the validity of MRI measurements in staging LEL.
There were 33 patients classified as stage I clinically, 44 patients as stage II, and 13 patients as stage III. There were significant differences in total, subcutaneous, the difference in subcutaneous area of limbs, subcutaneous/bone (S/B), and subcutaneous/muscle (S/M) between stage I and II as well as between stage I and III (P<0.001), but not between stage II and III (P=0.706, 0.329, and 0.229, respectively). A positive correlation was detected between the clinical stage and difference in subcutaneous area of limbs (rho =0.752, P<0.001), S/B (rho =0.747, P<0.001), S/M (rho =0.709, P<0.001), and subcutaneous (rho =0.723, P<0.001). For staging primary LEL, receiver operating characteristic (ROC) curves indicated that the difference in subcutaneous area of limbs had the best discrimination ability among parameters [area under the ROC curve (AUC) =0.950; 95% confidence interval (CI): 0.875-0.987; sensitivity: 95.45%; specificity: 84.85%], followed by S/B (AUC =0.930; 95% CI: 0.848-0.975; sensitivity: 77.27%; specificity: 93.94%) and S/M (AUC =0.895; 95% CI: 0.804-0.953; sensitivity: 77.27%; specificity: 90.91%). The ROC curves indicated that subcutaneous area (AUC =0.927; 95% CI: 0.844-0.974; sensitivity: 84.09%, specificity: 90.91%) and total (AUC =0.852; 95% CI: 0.753-0.923; sensitivity: 70.45%; specificity: 90.91%) also had discrimination ability between stage I and II.
The measurement of the soft tissue area of the calf may be used as an auxiliary method for staging primary LEL. For patients with unilateral primary LEL, the difference in subcutaneous area of limbs could be a specific indicator to distinguish clinical stage I from II.
原发性下肢淋巴水肿（LEL）的分期在临床工作中虽困难但至关重要，磁共振成像（MRI）因其对软组织的高分辨率可用于原发性LEL的定量评估。在本研究中，我们评估了基于MRI的软组织面积测量对原发性LEL分期的价值。
回顾性纳入2017年1月至2019年12月在北京世纪坛医院临床诊断为原发性下肢淋巴水肿的90例连续患者。采用短时间反转恢复（STIR）序列测量双侧小腿上1/3水平的总面积、肌肉面积、骨骼面积和皮下面积。获取患侧与健侧小腿皮下面积的差值，并计算（皮下面积）/（骨骼面积）和（皮下面积）/（肌肉面积）。根据2020年建立的国际淋巴学会（ISL）临床分期标准，将所有患者相应分为I期、II期和III期。进行统计分析以确定MRI测量在LEL分期中的有效性。
临床分类为I期的患者有33例，II期44例，III期13例。I期与II期以及I期与III期之间在总面积、皮下面积、肢体皮下面积差值、皮下/骨骼（S/B）和皮下/肌肉（S/M）方面存在显著差异（P<0.001），但II期与III期之间无显著差异（分别为P = 0.706、0.329和0.229）。临床分期与肢体皮下面积差值（rho = 0.752，P<0.001）、S/B（rho = 0.747，P<0.001）、S/M（rho = 0.709，P<0.001）和皮下面积（rho = 0.723，P<0.001）之间存在正相关。对于原发性LEL分期，受试者操作特征（ROC）曲线表明，肢体皮下面积差值在各参数中具有最佳的鉴别能力[ROC曲线下面积（AUC）= 0.950；95%置信区间（CI）：0.875 - 0.987；敏感性：95.45%；特异性：84.85%]，其次是S/B（AUC = 0.930；95% CI：0.848 - 0.975；敏感性：77.27%；特异性：93.94%）和S/M（AUC = 0.895；95% CI：0.804 - 0.953；敏感性：77.27%；特异性：90.91%）。ROC曲线表明，皮下面积（AUC = 0.927；95% CI：0.844 - 0.974；敏感性：84.09%，特异性：90.91%）和总面积（AUC = 0.852；95% CI：0.753 - 0.923；敏感性：70.45%；特异性：90.91%）在I期和II期之间也具有鉴别能力。
小腿软组织面积测量可作为原发性LEL分期的辅助方法。对于单侧原发性LEL患者，肢体皮下面积差值可能是区分临床I期和II期的特异性指标。
