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目的探讨肝脏扩散加权成像(DWI)时,b值与图像质量的相关性。方法对20例正常志愿者及60例行肝占位性病变患者行DWI并测量信噪比(SNR)及对比噪声比(CNR)。结果b为100s/mm2、300s/mm2时DWI图像的SNR平均值>5,b为600s/mm2、1100s/mm2时,SNR<5;随着b值的增大,血流灌注对表观扩散系数(ADC)影响逐渐减少,而图像伪影增多,CNR逐渐降低,囊性病变较实性病变的CNR降低明显。结论进行DWI扫描时选取b值为300~600s/mm2时最为合适。
Objective To investigate the correlation between b value and image quality in liver diffusion weighted imaging (DWI). Methods DWI was performed on 20 normal volunteers and 60 patients with liver space occupying lesions to measure signal to noise ratio (SNR) and contrast to noise ratio (CNR). Results The average SNR of DWI images with b = 100s / mm2 and 300s / mm2 was> 5, and the SNR was less than 5 with b = 600s / mm2 and 1100s / mm2. As the b value increased, The influence of ADC (ADC) decreased gradually, but the image artifacts increased and CNR decreased gradually. The CNR of cystic lesions was significantly lower than that of real lesions. Conclusion DWI scan when the b value of 300 ~ 600s / mm2 most appropriate.