Sugimoto Aiko, Katsuragawa Shigehiko, Uchiyama Yoshikazu, Shiraishi Junji
Graduate School of Health Sciences, Kumamoto University, Japan.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2013 Aug;69(8):855-63. doi: 10.6009/jjrt.2013_jsrt_69.8.855.
A temporal subtraction image, which is obtained by subtraction of a previous image from a current one, can enhance interval changes on a chest radiograph by removal of most normal structures. However, subtraction artifacts, which tend to reduce its effectiveness in the detection of interval changes, were still included in the conventional method. In this study, we have developed a pixel matching technique to reduce artifacts in the temporal subtraction images. With this technique, the pixel value in a nonlinearly warped previous image is replaced by a pixel value within a kernel, which is closest to the pixel value on a current image. For evaluation of the proposed method, one hundred temporal subtraction images with a simulated nodule were used. When the kernel size of 3×3 was employed in the pixel matching technique, the misregistration artifacts decreased by 72%, and the contrast-to-noise ratio of the simulated lung nodules was increased by 5% in comparison with the conventional method. However, the area of the simulated nodule on the subtraction image decreased by 6%. Our results indicated that the pixel matching technique can enhance simulated nodules, with a substantial reduction of misregistration artifacts in comparison with conventional subtraction images. Therefore, we believe that the temporal subtraction method with the pixel matching technique would assist radiologists' diagnoses for detection of lung nodules in digital chest radiography.
通过从当前图像中减去先前图像获得的时间减影图像，可以通过去除大多数正常结构来增强胸部X光片上的间隔变化。然而，传统方法中仍然存在减法伪影，这往往会降低其在检测间隔变化方面的有效性。在本研究中，我们开发了一种像素匹配技术来减少时间减影图像中的伪影。使用该技术，非线性扭曲的先前图像中的像素值被内核内最接近当前图像上像素值的像素值所取代。为了评估所提出的方法，使用了100张带有模拟结节的时间减影图像。当在像素匹配技术中采用3×3的内核大小时，与传统方法相比，配准误差伪影减少了72%，模拟肺结节的对比度噪声比提高了5%。然而，减影图像上模拟结节的面积减少了6%。我们的结果表明，与传统减影图像相比，像素匹配技术可以增强模拟结节，并大幅减少配准误差伪影。因此，我们认为采用像素匹配技术的时间减影方法将有助于放射科医生在数字胸部X光检查中诊断肺结节。
