Objective To compare the diagnostic value of CT and diffusion-weighted imaging in extremity soft tissue tumors. Methods A total of 104 cases of extremity soft tissue tumors were examined with CT scanning and MRI. All cases were histologically proven. Then we compared the CT value of various types of tumors. The b values of diffusion were 0 and 500 s/mm2. The apparent diffusion coefficient (ADC) values of a large region with no hemorrhage, necrosis, scar tissue, or calcification representing the lesion were measured. ADC values of benign tumors, malignant tumors and normal muscles were compared. Results There were 68 cases of benign tumors and 36 cases of malignant tumors. The CT findings of 45 cases and the MRI findings of 87cases were in accordance with pathological examination. The diagnosis of 59 cases by CT and 17 cases by MRI were wrong. The CT features of soft tissue tumors showed the low density masses. The features of lipoma or cyst were typical on CT. There were large differences among the different types of tumors performance on T1WI and T2WI. The ADC values of the malignant tumors were significantly lower than those of benign lesion sand muscles (P < 0.01). There was no significant difference in ADC values between benign lesions and muscles. there was significant difference between the detection level of CT and MRI (P < 0.01). Conclusion CT can clearly show soft tissue tumor lesions and to clarify their relationship and the surrounding tissue, but can not accurately characterize. MRI diffusion-weighted imaging can better differentiate benign and malignant, and speculate the histological lesions sources. MRI detection level is significantly higher than CT and more consistent with a higher degree of pathology. Thus in the preoperative diagnosis of soft tissue tumors, diffusion-weighted imaging MRI should be preferred.%目的：对比分析多层螺旋CT与MRI扩散加权成像对于四肢软组织肿瘤的诊断价值。方法：对于104例原发性四肢软组织肿瘤，均行CT检查和MRI检查，所有病例均经手术病理证实。 CT检查中比较各类肿瘤的CT值。 MRI检查中，MRI扩散加权成像的扩散敏感因子（b值）选取0，500 s/mm2，操作时尽量避开出血、坏死、瘢痕、钙化等不均质成分区，选取肿瘤实体部分最大感兴趣区，比较良、恶性肿瘤和肌肉组织的表观扩散系数（apparent diffusion coefficient，ADC）的差异。结果：在所有104例患者中，良性68例，恶性36例。CT检查与病理相符45例，MRI相符87例；定性错误和未定性：CT 59例，MRI 17例。软组织肿瘤在CT上显示为低密度肿块，其中脂肪瘤和囊肿表现具有特异性；MRI中，不同类型肿瘤的T1WI和T2WI表现差异较大，而恶性肿瘤的ADC值显著低于良性肿瘤和肌肉组织（P＜0．01）；但良性肿瘤和肌肉组织的ADC缺乏显著差异（P＞0．05）。CT和MRI的检测水平比较，P＜0．01。结论：CT能够清楚显示四肢软组织肿瘤病灶，并明确其和周围组织关系，但无法进行准确定性；MRI扩散加权成像可以更好地鉴别良恶性，并推测病变组织学来源。MRI检测水平显著高于CT，与病理相符度更高。因而在四肢软组织肿瘤的术前诊断中，应首选MRI扩散加权成像。
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