3.0T乳腺扩散加权成像中b值的选择

Selection of b Value in Diagnosis of Breast Cancers with 3.0T DWI

目的探讨3.0T乳腺扩散加权成像(Diffusion Weighted Imaging,DWI)中b值大小及其在疾病诊断中的价值。方法收集5例正常乳腺受检者,19例乳腺良性病变患者及18例乳腺癌患者。采用GE公司Signa HDx 3.0T超导型全身磁共振成像(MRI)系统,进行乳腺常规MR(磁共振)扫描和DWI。扩散敏感系数(b)值分别取600、1000、1500 s/mm2。观察正常乳腺、乳腺良性病变和乳腺癌的常规MRI和DWI,测量其表观扩散系数(ADC)值并进行统计学分析。结果 b值不同得到的图像质量不同,b值越高对水分子扩散运动越敏感,但图像信噪比(SNR)、对比噪声比(CNR)越低,噪声越大,图像变形越严重;反之,b值越低,图像SNR、CNR越高,但对水分子扩散运动不敏感。b=1000 s/mm2时,正常组平均ADC值是1.89×10-3mm2/s,良性病变组平均ADC值是1.51×10-3mm2/s,乳腺癌组平均ADC值是1.06×10-3mm2/s。结论运用GE 3.0T超导磁共振系统进行乳腺扩散加权成像,b值取1000 s/mm2时,能获得优质的DWI,所测得的ADC值可以为乳腺癌及良性病变的鉴别诊断提供重要信息。

Objective To evaluate the effects of 3.0T DWI （Diffusion Weighted Imaging） with different b values （Diffusion Sensitivity Coefficient） in diagnosis of breast cancers. Methods Five cases with normal breasts （Normal Group）, 19 cases with breast benign lesions （Benign Lesions Group） and 18 cases with breast cancer （Breast Cancer Group） were collected and examined with conventional MR scanning and DWI breast imaging. Calculation and statistical analysis of ADC （Apparent Diffusion Coefficient） values were made in three groups respectively with b values of 600 s/mm2, 1000 s/mm2 and 1500s/mm2. Results The quality of images was decided by different b values. Higher b values would result in greater sensitivity to the motion of water molecules, lower SNR （Signal to Noise Ratio） and CNR （Contrast- noise Ratio）. More noise would cause greater distortion of the image. On the contrary, the lower b value was, the higher SNR and CNR the images would have. However, lower b values were not sensitive to the motion of water molecular. When b value was equal to 1000s/mm2, the mean ADC value of Normal Group was 1.89~10-3 mm2/s, Benign Lesions Group was 1.51~103 mmZ/s, Breast Cancer Group was 1.06x 10.3 mma/s. Conclusion High-quality DWI images can be obtained with application of GE 3.0T MR when b value is set at 1000 s/mm2. ADC can values provides important information for diagnosis of breast cancers and benign lesions.