ASIR或MBIR算法重建颈肩部CT图像质量总是优于FBP吗?

Is ASIR or MBIR always better than FBP algorithm at neck and shoulder CT images

目的比较滤过反向投影(filtered back projection,FBP),自适应迭代重建技术(adaptive statistical iterative reconstruction,ASIR),基于模型的迭代重建(model-based iterative reconstruction,MBIR)三种算法重建颈肩部CT平扫和增强图像质量。方法对20例患者颈肩部进行相对低剂量CT平扫及增强扫描,采用FBP,ASIR(权重50%),MBIR三种算法重建出颈肩部CT图像,测量甲状腺,腋下脂肪、锁骨下动脉及周围肌肉的CT值,采用方差分析比较三种重建算法图像的对比噪声比(contrast noise ratio,CNR)及噪声指数(noise index,NI)。同时,两名医生对图像进行主观评价,采用卡方检验比较三种重建算法的主观评级。结果颈肩部CT平扫和增强图像,MBIR和ASIR的CNR显著高于FBP,NI显著低于FBP。MBIR的CNR显著高于ASIR,NI显著低于ASIR。主观图像噪声和胸廓入口处射线硬化伪影,MBIR和ASIR显著优于FBP;主观图像对比,FBP显著优于MBIR和ASIR;小结构可视程度、主观视觉病灶可信度与诊断信心,三者不存在显著性差异。结论在相对低剂量扫描条件下,MBIR和ASIR能够显著降低颈肩部的主观和客观图像噪声,显著提高CNR。但是由于图像面貌的改变导致的主观图像对比的下降,未能显著提高小结构可视程度,主观视觉病灶可信度与诊断信心。

Objective To compare the qualities of plain and contrast enhanced images at the neck and shoulder reconstructed by three different algorithms：Filtered Back Projection （FBP）,Adaptive Statistical Iterative Reconstruction （ASIR） and Model-Based Iterative Reconstruction （MBIR）.Methods Twenty patients underwent cervical and shoulder CT scan with a low radiation dose before and after the injection of contrast media.Images were reconstructed by three different algorithms：FBP,ASIR （50％ weighted） and MBIR.CT values （HU） of thyroid gland,axillary fat subclavian artery and muscles were measured and recorded as mean ± standard deviation （SD）.Contrast-noise ratio （CNR） and noise index （NI） were calculated and compared among three sets of images with analysis of variance.Subjective image quality was assessed by two radiologists independently and compared with Chi-square test.Results On plain and contrast enhanced images of the neck and shoulder,significantly increased CNR and decreased NI were documented at MBIR and ASIR compared with FBP images （P ＜0.05）.And in some areas,CNR increased and NI decreased significantly at MBIR than at ASIR images （P ＜0.05）.Subjective image noise and artifacts were significantly reduced by MBIR than ASIR and FBP.Image contrast of FBP was significantly better than MBIR and ASIR.There were no significant differences on the visibility of bjective visual lesion conspicuity and diagnostic confidence among those three groups.Conclusion Objective and subjective image noise can be significantly reduced by MBIR and ASIR at the shoulder at a relative low radiation dose.However,the visibility of small structures,subjective visual lesion conspicuity and diagnostic confidence remain due to compromised the image contrast by MBIR and ASIR and the change of image appearance.