Kyriakou Y, Ertel D, Lapp R M, Kalender W A
Institute of Medical Physics, University of Erlangen-Nuernberg, Germany.
Br J Radiol. 2009 Mar;82(975):235-42. doi: 10.1259/bjr/24287373. Epub 2008 Dec 19.
The objective of this work was to reduce motion artefacts in non-gated dual-energy subtraction radiography whilst preserving the contrast-to-noise ratio (CNR) in regions with low motion. Dual-energy radiography provides material-selective information (soft-tissue and bone images) that may be used for improved detection of calcifications in lung nodules. The weighted logarithmic dual-energy subtraction of thoracic images performed without electrocardiogram gating results in motion-induced artefacts. The low-energy image was acquired at the usual dose setting at 60 kV. To obtain the high-energy (120 kV) information, a series of consecutive images at a time interval of 30 ms were made. The series integral dose was equivalent to the dose of a single conventional high-energy image. A motion-free merging technique was introduced that combines standard images yielding low image noise with phase-selective images yielding motion artefact-free image regions which are used for dual-energy subtraction. Evaluations of the method were performed with simulations and measurements using a C-arm system (Axiom Artis; Siemens AG, Germany) equipped with a flat detector of 40 x 30 cm(2). The merging approach conserved standard image noise levels and the CNR in areas without cardiac motion, whereas image noise in pericardial lung regions and in the heart was increased compared with standard images. Motion artefacts in the heart and in the lung areas close to the heart are significantly reduced in the material-selective images when compared with a standard non-gated subtraction.
这项工作的目标是减少非门控双能减影X线摄影中的运动伪影，同时保持低运动区域的对比度噪声比（CNR）。双能X线摄影提供了物质选择性信息（软组织和骨骼图像），可用于改进肺结节钙化的检测。在没有心电图门控的情况下进行胸部图像的加权对数双能减影会导致运动诱导的伪影。低能图像在60 kV的常规剂量设置下采集。为了获得高能（120 kV）信息，以30 ms的时间间隔拍摄了一系列连续图像。该系列的总剂量相当于一张常规高能图像的剂量。引入了一种无运动合并技术，该技术将产生低图像噪声的标准图像与产生无运动伪影图像区域的相位选择图像相结合，用于双能减影。使用配备40×30 cm²平板探测器的C形臂系统（Axiom Artis；德国西门子公司）通过模拟和测量对该方法进行了评估。合并方法在无心脏运动的区域保持了标准图像噪声水平和CNR，而与标准图像相比，心包肺区域和心脏中的图像噪声增加。与标准非门控减影相比，在物质选择性图像中，心脏和靠近心脏的肺区域的运动伪影显著减少。
