Kristanto Wisnumurti, Tuncay Volkan, Vliegenthart Rozemarijn, van Ooijen Peter M A, Oudkerk Matthijs
Department of Radiology, Center for Medical Imaging - North East Netherlands, University Medical Center Groningen, University of Groningen, PO BOX 30001, 9700RB, Groningen, The Netherlands.
Int J Cardiovasc Imaging. 2015 Feb;31(2):429-36. doi: 10.1007/s10554-014-0554-1. Epub 2014 Oct 18.
Lumen contrast-enhancement influences non-calcified atherosclerotic plaque Hounsfield-unit (HU) values in computed tomography (CT). This study aimed to construct and validate an algorithm to correct for this influence. Three coronary vessel phantoms with 1, 2, and 4 mm circular hollow lumina; with normal and plaque-infested walls were scanned simultaneously in oil using a dual-source CT scanner. Scanning was repeated as the lumina were alternately filled with water and four contrast solutions (100-400 HU, at 100 HU intervals). Images were reconstructed at 0.4 mm x-y pixel size. Pixel-by-pixel comparisons of contrast-enhanced and non-contrast-enhanced images confirmed exponential declining patterns in lumen contrast-enhancement influence on wall HU-values from the lumen border (y = Ae(-λx) + c). The median difference of the inside and outside 2-pixel radius part of the contrast-enhanced coronary phantom wall to the reference (non-contrast-enhanced images) was 45 and 2 HU, respectively. Based on the lumen contrast-enhancement influence patterns, a generalized correction algorithm was formulated. Application of the generalized correction algorithm to the inside 2-pixel radius part of the wall reduced the median difference to the reference to 4 HU. In conclusion, lumen contrast-enhancement influence on the vessel wall can be defined by an exponential approximation, allowing correction of the CT density of the vessel wall closest to the lumen. With this correction, a more accurate determination of vessel wall composition can be made.
管腔对比增强会影响计算机断层扫描（CT）中未钙化动脉粥样硬化斑块的亨氏单位（HU）值。本研究旨在构建并验证一种算法以校正这种影响。使用双源CT扫描仪在油中同时扫描三个具有1毫米、2毫米和4毫米圆形中空管腔的冠状动脉模型；管腔壁正常和有斑块。当管腔交替填充水和四种对比剂溶液（100 - 400 HU，间隔100 HU）时重复扫描。以0.4毫米×0.4毫米的像素尺寸重建图像。对比增强图像和非对比增强图像的逐像素比较证实了管腔对比增强对管壁HU值从管腔边界起的影响呈指数下降模式（y = Ae(-λx) + c）。对比增强冠状动脉模型壁的内外2像素半径部分与参考（非对比增强图像）的中位数差异分别为45 HU和2 HU。基于管腔对比增强影响模式，制定了一种通用校正算法。将通用校正算法应用于管壁内侧2像素半径部分，使与参考的中位数差异降至4 HU。总之，管腔对比增强对血管壁的影响可用指数近似来定义，从而可校正最接近管腔的血管壁CT密度。通过这种校正，可以更准确地确定血管壁成分。
