Güler Ezgi, Vural Volkan, Ünal Emre, Köse Ilgaz Çağatay, Akata Deniz, Karcaaltıncaba Muşturay, Hazırolan Tuncay
Department of Radiology, Faculty of Medicine, Hacettepe University; Ankara-Turkey.
Anatol J Cardiol. 2016 Feb;16(2):119-24. doi: 10.5152/akd.2015.5920. Epub 2015 Feb 11.
To determine the effect of "Iterative Reconstruction in Image Space" (IRIS) on image quality by comparing reconstructions of both medium and sharp kernels when evaluating coronary calcifications or stents during coronary computed tomography (CT) angiography.
Thirty one consecutive patients were scanned with an electrocardiogram-gated helical technique on a dual-source CT system. Image reconstruction was performed using standard filtered back projection (FBP) and IRIS algorithm on both medium and sharp kernels (B26f, I26f, B46f, I46f). Each reconstruction was derived from the same raw data. Two blinded readers graded image quality using a five-point scale. Noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) were obtained. Noise was derived from the ascending aorta and left ventricle. SNR was obtained from sinus Valsalva, interventricular septum, and coronary vessels. CNR was obtained from septum, coronary vessels, and left ventricle. Comparisons of paired results between FBP and IRIS images were analyzed using the repeated measures analysis of variance method. Interreader correlation was assessed using weighted Kappa statistic.
Noise values of the ascending aorta and left ventricle were significantly lower in the images reconstructed with IRIS than those reconstructed with FBP for the evaluation of the same filters. SNR and CNR values were higher in the IRIS images (p<0.05). Interreader agreement for four reconstructions was interpreted as moderate (κ=0.40-0.59).
IRIS significantly reduced image noise and improved imaging of coronary calcifications or stents. When combined with a sharp kernel, IRIS can improve image quality by reducing the negative effects of decreased signal that may result from using a sharp kernel.
在冠状动脉计算机断层扫描（CT）血管造影评估冠状动脉钙化或支架时，通过比较中等和锐利内核的重建图像，确定“图像空间迭代重建”（IRIS）对图像质量的影响。
31例连续患者在双源CT系统上采用心电图门控螺旋技术进行扫描。使用标准滤波反投影（FBP）和IRIS算法在中等和锐利内核（B26f、I26f、B46f、I46f）上进行图像重建。每次重建均来自相同的原始数据。两名不知情的阅片者使用五点量表对图像质量进行分级。获取噪声、信噪比（SNR）、对比噪声比（CNR）。噪声来自升主动脉和左心室。SNR来自主动脉窦、室间隔和冠状动脉。CNR来自室间隔、冠状动脉和左心室。使用重复测量方差分析方法分析FBP和IRIS图像配对结果的比较。使用加权Kappa统计量评估阅片者间的相关性。
对于相同滤波器的评估，IRIS重建的图像中升主动脉和左心室的噪声值显著低于FBP重建的图像。IRIS图像中的SNR和CNR值更高（p<0.05）。四名阅片者对四种重建的一致性被解释为中等（κ=0.40-0.59）。
IRIS显著降低了图像噪声，改善了冠状动脉钙化或支架的成像。当与锐利内核结合使用时，IRIS可以通过减少使用锐利内核可能导致的信号降低的负面影响来提高图像质量。
