MRI在鉴别鼻咽癌放疗后局部复发与纤维化的应用研究

Localized Tumor Recurrence Versus Postradiation Fibrosis in the Nasopharynx:Differentiation with MRI

本研究对经CT 扫描证实鼻咽部有软组织密度肿块的36例鼻咽癌放疗后患者行MRI 扫描,并以8例未经治疗的鼻咽癌患者作对照。对各病变信号强度的分析结果显示:放疗后纤维化在T_1WI 和T_2WI 上多显示为低或稍低信号强度;肿瘤在T_1WI 上多显示为稍高信号强度,但与纤维化有一定重叠,在T_2WI 上肿瘤信号强度明显增强,与纤维化区别最明显,对诊断起主要作用.但肿瘤的信号强度变化缺乏特异性,放疗后水肿和炎症可有类似表现,应注意鉴别。

Magnetic resonance imaging(MRI)was conducted on 36 patients withnasopharyngeal carcinoma(NPC)verified by biopsy,cytology or longperiod follow-up.All had undergoneradiation therapy and presented a softtissue mass in the nasopharynx by CTscan.Of 36 patients,14 had tumorrecurrence,20 had only radiation fi-brosis,1 had postradiation edema and1 had inflammatory change.Another8 patients with untreated NPC ma-de up a comparison group.The results showed that MRI maybe a noninvasive method for distin-guishing radiation fibrosis from localrecurrent NPC(p<0.01).Radiationfibrosis usually has low signal inten-sity(similar to muscle)on both T_1-and T_2-weighted spin-echo sequen-ces_.T_2-weighted images were most hel-pful in distinguishing recurrent tu-mor from radiation fibrosis,becausetheir T_2 relaxation time and signalintensity were different.However,the postradiation edema and infectionin nasopharynx may have similarsignal intensity to that of neoplasm and may be therefore confused withrecurrent tumor.The positve predicti-ve value,negative predictive value,sensitivity and specificity of MRIwere:71%,88%,86% and 75% respe-ctively.The overall diagnostic accu-racy rate was 79% with these signalintensity characteristics.