动态增强磁共振成像对直肠癌术前新辅助治疗疗效的评价

目的观察动态增强磁共振（DCE—MRI）能否在术前判断直肠癌新辅助治疗的疗效，比较常规T2WI与DCE—MRI对直肠癌术前T、N分期的准确性。方法收集术前或术后病理确诊的直肠癌患者40例。其中行术前新辅助治疗者22例，未进行术前新辅助治疗者18例。所有患者均在GE1．5T Twinspeed HD MR扫描仪行盆腔动态增强扫描。扫描序列包括T2WI压脂、T1WI、DWI，快速三维容积T1加权脂肪抑制成像增强扫描（3DLAVA）。分析动态增强瞌线的各项参数在新辅助治疗前后的变化，观察癌灶曲线上升速率。结果①对未进行术前治疗的直肠癌分期的准确性：DCE—MRI与常规T2WI对直肠癌T分期的准确性分别为83-3％和66．7％，对环周切缘阴性判断准确性为88-2％和70．6％。T2WI及DCE—MRI均能发现直径≥2mm的淋巴结。②对新辅助治疗后直肠癌再分期的准确性：DCE—MRI对T、N再分期的准确性可达86．4％：和81.8％，对环周切缘情况判断准确性为100％。而T2WI进行T、N再分期较困难。③治疗前癌灶的曲线上升速率明显高于正常肠管；治疗后达病理完全缓解组原癌灶部略低于下段正常肠管，但是差异不明显；治疗后未达病理完全缓解组癌灶部仍高于下段正常肠管。结论DCE—MRI对术前直肠癌分期的准确性高，并能够准确判断新辅助治疗后痛周切缘情况。癌灶与参照肠管的上升速率比较有助于在术前判断疗效。

Effects of neoadjuvant chemoradiotherapy prior to surgery on rectal cancer assessing by DCE-MRI

Objective： To evaluate dynamic contrast-enhanced MR imaging （DCE- MRI） in assessing pathologic responses in rectal cancer treated with neoadjuvant chemoradiotherapy （NCRT）, and to compare the diagnostic accuracy of T2WI and DCE-MRI in the preoperative T and N staging of rectal cancer. Materials and Methods： Forty patients with pathologically proven primary rectal cancer were enrolled in this study, 18 patients had no preoperative treatments, 22 patients treated with NCRT. DCE-MRI was performed in all patients on GE 1.5 T Twinspeed HD MR scanner. The rectal cancer stage was made according to the TNM classification criteria. Preoperative MRI assessment was compared with postoperative histopathological findings. Parameters of DCE-MRI curves including type of enhancement, the time of maximum uptake, the uptake velocity T, were analyzed. The normal rectum part was selected as control. Results： （1） For rectal cancer without NCRT, DCE-MRI had an accuracy of 83.3% for T staging, and T2WI had an accuracy of 66.7%. For predicting a clear circumferential resection margin （CRM）, DCE-MRI had an accuracy of 88.2%, and T2WI had an accuracy of 70.7%. Lymph nodes of diameter more than 2 mm could be found in DCE-MRI and T2WI. （2） For rectal cancer treated with NCRT, DCE-MRI had an accuracy of 86.4% for T staging and 81.8% for N staging in preoperative tumor restaging, and had an accuracy of 100% for predicting a clear CRM. However, T2WI could not distinguish stages for the tumor. （3） The T value of the lesions was equal to or lower than the normal rectum part in pathologic complete response （PCR） group, while the T value of the lesions was higher than normal rectum part in non-PCR group. Conclusion： DCE-MRI has high accuracy for preoperative tumor restaging, and play an important role for predicting circumferential resection margin status of rectal cancer treated with NCRT.