ディジタルファントムによる非線形適応型平滑化フィルタの評価

• Published in: 日本放射線技術学会雑誌 Vol. 64; no. 4; pp. 434 - 441
• Main Authors: 石屋, 博樹, 梁川, 功, 大下, 亮介, 森, 一生, 佐藤, 和宏, 後藤, 光範
• Format: Journal Article
• Language: Japanese
• Published: 公益社団法人 日本放射線技術学会 2008
• Subjects: adaptive filter; computed tomography (CT); digital phantom; image processing
• ISSN: 0369-4305; 1881-4883
• DOI: 10.6009/jjrt.64.434

As a result of the development of multi-slice CT, diagnoses based on three-dimensional reconstruction images and multi-planar reconstruction have spread. For these applications, which require high z-resolution, thin slice imaging is essential. However, because z-resolution is always based on a trade-off with image noise, thin slice imaging is necessarily accompanied by an increase in noise level. To improve the quality of thin slice images, a non-linear adaptive smoothing filter has been developed, and is being widely applied to clinical use. We developed a digital bar pattern phantom for the purpose of evaluating the effect of this filter and attempted evaluation from an addition image of the bar pattern phantom and the image of the water phantom. The effect of this filter was changed in a complex manner by the contrast and spatial frequency of the original image. We have confirmed the reduced effect of image noise in the low frequency component of the image, but decreased contrast or increased quantity of noise in the image of the high frequency component. This result represents the effect of change in the adaptation of this filter. The digital phantom was useful for this evaluation, but to understand the total effect of filtering, much improvement of the shape of the digital phantom is required.