Assessment of lymph node status in rectal cancer by ;imaging

治疗前准确诊断淋巴结转移与患者手术方式的选择、放化疗方案的制定以及患者预后判断密切相关。目前临床常用的直肠癌淋巴结转移影像诊断方法包括，核磁共振成像（MRI）、直肠腔内超声（ERUS）、多排螺旋 CT （MDCT）以及 PET-CT等，但相关研究中关于直肠癌淋巴结转移的影像诊断标准并不统一。将体积大小作为直肠癌淋巴结分期的标准准确性较低，应用高分辨MRI分析淋巴结形态、边缘与信号特征显著提高了诊断准确性。然而，图像分辨率限制及研究者对于形态特征理解的差异都将可能导致研究结果可重复性欠佳。超磁敏感铁氧颗粒强化MRI（USPIO-MRI）被用于转移性淋巴结诊断以及直肠癌放化疗效果的评价。尽管其可重复性有明显提高，但未被批准应用于临床实践。作为功能影像成像方法，扩散加权MRI （DW-MRI）能够敏感地发现淋巴结，但其诊断转移性淋巴结的特异性较低。由于空间分辨率有限，PET-CT不能发现小而转移的淋巴结，诊断敏感性较低。对于直肠系膜内的转移性淋巴结，ERUS和高分辨率MRI具有相似的诊断准确性。而MRI及DW-MRI诊断视野明显大于ERUS，对于盆腔侧方淋巴结以及直肠上动静脉周围淋巴结能够有效筛选和诊断。 MDCT可以用于胸部及腹部盆腔的检查，能够筛选远处转移的淋巴结。就直肠癌淋巴结诊断诊断而言，应采用不同的影像方法或者多种影像方法相结合的方式才能更有效地达成不同的临床目的。Assessment of lymph node status in patients with rectal cancer is important before operation and neoadjuvant treatment because it has an influence on definition of operative plan, strategy of chemoradiotherapy and prognosis of the patients with rectal cancer. The imaging modalities that can be used to assess lymph node status include magnetic resonance imaging (MRI), endorectal ultrasonography (ERUS), multi-row detector computer tomography (MDCT), and PET-CT. The existing imaging criteria for metastatic lymph nodes in rectal cancer have not been reached. Combined with morphologic and functional imaging characteristics can be accurately predict metastatic lymph nodes. Based on the size of lymph node, the accuracy of rectal cancer N stage defined by imaging modality is poor. If the border and signal intensity of lymph nodes are used to predict the metastasis , the sensitivity and specificity can be significantly improved. However, the reproducibility needs an improvement because of limitation in imaging quality and difference in ability of imaging interpretation. In comparison , ultra small superparamagnetic iron oxide MRI (USPIO-MRI) has relatively higher reproducibility in definition of the metastatic lymph nodes while it is not permitted as an imaging tool used in clinical practice. In addition, USPIO-MRI has been used to evaluate the lymph node response to chemotherapy. As functional imaging tool, DW-MRI has high sensitivity in detection of lymph nodes, while the specificity is low. In contrast, PET-CT has lower sensitivity because of the limitation in imaging resolution, which can not find the small metastatic lymph nodes. ERUS and high resolution MRI have similar ability in distinguishing metastatic and benign nodes within mesorectum. While MRI and DW-MRI have greater diagnostic view than ERUS, thus they can effectively screen and diagnose the pelvic lateral lymph nodes and rectal upper arteriovenous lymph nodes. MDCT is the better choice in screening chest and abdominal metastatic lymph nodes compared with other modalities. The proper selection of imaging modality or combination of multi-modalities is necessary for special purpose in clinical practice.PubMed中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)6630-6331