Zacharaki E I, Matsopoulos G K, Asvestas P A, Nikita K S, Gröndahl K, Gröndahl H-G
Institute of Communication and Computer Systems, National Technical University of Athens, Greece.
Dentomaxillofac Radiol. 2004 Nov;33(6):379-90. doi: 10.1259/dmfr/21571843.
To establish a digital subtraction radiography scheme for aligning clinical in vivo radiographs based on the implementations of an automatic geometric registration method and a contrast correction technique.
Thirty-five pairs of in vivo dental radiographs from four clinical studies were used in this work. First, each image pair was automatically aligned by applying a multiresolution registration strategy using the affine transformation followed by the implementation of the projective transformation at full resolution. Then, a contrast correction technique was applied in order to produce subtraction radiographs and fused images for further clinical evaluation. The performance of the proposed registration method was assessed against a manual method based on the projective transformation.
The qualitative assessment of the experiments based on visual inspection has shown advantageous performance of the proposed automatic registration method against the manual method. Furthermore, the quantitative analysis showed statistical difference in terms of the root mean square (RMS) error estimated over the whole images and specific regions of interest.
The proposed automatic geometric registration method is capable of aligning radiographs acquired with or without rigorous a priori standardization. The methodology is pixel-based and does not require the application of any segmentation process prior to alignment. The employed projective transformation provides a reliable model for registering intraoral radiographs. The implemented contrast correction technique sequentially applied provides subtraction radiographs and fused images for clinical evaluation regarding the evolution of a disease or the response to a therapeutic scheme.
基于自动几何配准方法和对比度校正技术的实现，建立一种用于对齐临床体内X光片的数字减影血管造影方案。
本研究使用了来自四项临床研究的35对体内牙科X光片。首先，通过应用多分辨率配准策略，使用仿射变换自动对齐每对图像，然后在全分辨率下实施投影变换。然后，应用对比度校正技术以生成减影X光片和融合图像，用于进一步的临床评估。将所提出的配准方法的性能与基于投影变换的手动方法进行比较评估。
基于视觉检查的实验定性评估表明，所提出的自动配准方法相对于手动方法具有优势性能。此外，定量分析表明，在整个图像和特定感兴趣区域估计的均方根（RMS）误差方面存在统计学差异。
所提出的自动几何配准方法能够对齐在有或没有严格先验标准化的情况下获取的X光片。该方法基于像素，在对齐之前不需要应用任何分割过程。所采用的投影变换为口腔内X光片的配准提供了可靠的模型。依次应用的对比度校正技术提供了减影X光片和融合图像，用于关于疾病演变或治疗方案反应的临床评估。
