两种不同超高b值扩散加权成像在前列腺癌MRI检查中对图像质量的影响

Effect of Two Different Diffusion Weighted Imaging with Ultra-high b Values on Image Quality in Postate Cancer MRI

目的比较超高b值读出方向分段采样平面回波成像(RS-EPI)和常规单次激发平面回波成像(SS-EPI)在前列腺癌MRI检查中对图像质量的影响。资料与方法回顾性分析33例在3.0T MR上均行SS-EPI和RS-EPI超高b值扩散加权成像检查的前列腺癌患者的影像资料(b=1000、2000、3000 s/mm^2),分别由1名副主任医师和1名技师在不提供任何临床资料及MRI序列信息的情况下,以轴面T2WI抑脂序列作为参照,针对2种扩散加权成像图像从病灶显示的清晰度、图像解剖变形、图像锐利度、细节显示方面进行独立主观评分。由第3名医师在工作站上测量图像的信噪、对比噪声比和对比度,比较常规SS-EPI和RS-EPI两组间的图像质量。结果 2名阅片者在共同评价2种序列图像(b=1000、2000、3000 s/mm^2)在病灶显示的清晰度、解剖变形、图像锐利度及细节显示方面具有很好的一致性(Kappa>0.70)。RS-EPI和SS-EPI序列在不同超高b值图像质量的主观评价(清晰度、解剖变形、图像锐利度、细节显示)及客观评价(信噪比、对比度及对比噪声比)中,RS-EPI序列图像质量的各项指标在b=1000 s/mm^2时主观评估部分指标差异无统计学意义(P>0.05),而其客观评估及b值选取2000、3000 s/mm^2时,主、客观评价的各项指标明显优于SS-EPI(P<0.001)。结论超高b值RS-EPI序列与常规SS-EPI序列相比明显提高了图像质量的多个指标,更有利于早期前列腺癌的检出及鉴别。

Purpose To compare the difference between readout-segmented echo planar imaging(RS-EPI)and conventional single shot echo planar imaging(SS-EPI)on image quality with ultra-high b value for prostate cancer MRI.Materials and Methods The image data of 33 patients with prostate disease who underwent both SS-EPI and RS-EPI on 3.0T MR scanner(with ultra-high b value of 1000,2000 and 3000 s/mm2)were retrospectively analyzed.Independent subjective scoring was performed for the image quality of the two diffusion weighted images in four aspects:lesion clarity,anatomical distortion,image sharpness and detail display,using the axial T2WI anti-lipid sequence as the reference.All the images were separately analyzed by two experienced radiologists blinded to any clinical information as well as MRI sequence information.The signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR)and contrast were also measured on the workstation by a third physician.The comparison of image quality between conventional SS-EPI and RS-EPI groups was performed.Results The two readers had good consistency in all the four subjective aspects when evaluating the two kinds of diffusion weighted images,with Kappa>0.70.With b value of 2000 and 3000 s/mm2,the subjective evaluation indicators(lesion clarity,anatomical distortion,image sharpness and detail display)and objective evaluation indicators(SNR,contrast and CNR)of RS-EPI were significantly better than those of SS-EPI(P<0.001);while with b value of 1000 s/mm2,the objective evaluation indicators of RS-EPI were significantly better than those of SS-EPI(P<0.001),but there was no statistically significant difference in the subjective evaluation indicators(P>0.05).Conclusion Compared with the conventional SS-EPI,ultra-high b value RS-EPI sequence significantly improves the image quality,which is more conducive to the detection and identification of early prostate cancer.