Eri Matsuyama MS, Presenter: Nothing to Disclose

Du-Yih Tokugi Tsai PhD, Abstract Co-Author: Nothing to Disclose

Yongbum Lee PhD, Abstract Co-Author: Nothing to Disclose

Masaru Sekiya PhD, Abstract Co-Author: Nothing to Disclose

Takashi Sekikawa BS, Abstract Co-Author: Nothing to Disclose

Masaki Tsurumaki MSC, Abstract Co-Author: Nothing to Disclose

An important criterion for accepting any type of medical imaging system is the quality of the images produced by the imaging system. In this study, we proposed an information-entropy-based metric as a useful tool for combined characterization of noise and resolution properties in digital radiography.

The concept of information entropy describes with how much randomness (or uncertainty) there is in an image. If the uncertainty is measured before and after imaging, the reduction in the uncertainty, i.e., information entropy, is a quantitative measure of the information transmitted by the image. The image quality then can be quantitatively compared when the transmitted information (TI) provided by the images are known. Two acrylic step wedges with 0-1-2-3-4-5 mm and 0-2-4-6-8-10 mm in thickness were used as subjects (phantoms) in the study. The specified exposure factors were kept at 42kV and 10mA but the exposure time was varied ranging from 0.1 sec to 0.5 sec. An imaging plate for digital radiography was used as a detector to record x-ray intensities. We performed three experiments: the first experiment was conducted to verify the effect of noise, the second for analyzing the effect of resolution (blur) and the third for investigating the combined effect of deteriorated blur and noise on the images.

The TI value increased with the decrease of image noise and decreased with the increase of deterioration of blur. Our experimental results also confirmed that the combined effect of deteriorated blur and noise on the images can be analyzed using the TI metric. Furthermore, a pilot comparison of the new metric proposed with MTF and noise power spectrum was shown and discussed.

Our results indicate that the amount of TI is closely correlated with both image noise and image blur. Also, the results demonstrate the potential usefulness of the proposed method for evaluation of physical quality of the images obtained from imaging systems.

Information-entropy measure is useful for characterizing and analyzing the combined effect of deteriorated blur and noise on the images obtained from digital radiographic imaging systems.

Matsuyama, E, Tsai, D, Lee, Y, Sekiya, M, Sekikawa, T, Tsurumaki, M, Quantitative Characterization of Noise and Resolution Properties of Digital Radiography Using an Information-Entropy Measure.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5005749.html