IJMPCERO  Vol.7 No.1 , February 2018
Detection of Spherical Gold Fiducials in kV X-Ray Images Using Intensity-Estimation-Based Method
Abstract: Fiducial marker detection algorithms in kilovoltage x-ray images using physical characteristics of transmission x-ray have been proposed. It, however, has been suggested recently that factors besides transmission x-ray affect x-ray images. The purpose of this study was to develop a new fiducial detection algorithm using fiducial intensity estimation based on physical characteristics of x-ray images with gold fiducials. First, x-ray images of a fiducial on a water-equivalent phantom were acquired. It was observed that the ratio of background to fiducial intensity in the images decreased as phantom thickness increased. Based on the negative correlation, we identified a function for estimating fiducial intensity that consists of background intensity and the amount of scattered radiation by the other x-ray source of an orthogonal imaging system and a treatment beam. Then, we developed an algorithm that extracts fiducial candidates using the estimation function. Its performance was measured using x-ray images which had 3824 fiducials altogether. The average number of false-positive detection of the proposed algorithm in single image was one-tenth of an algorithm considering only transmission x-ray. The proposed algorithm detected 99.5% of all fiducials under an error of 1.0 mm, while the other algorithm detected 94.7% or less (Clinical trial number: UMIN000005324).
Cite this paper: Kokubo, M. , Yamada, M. , Sawada, A. , Mukumoto, N. , Miyabe, Y. , Mizowaki, T. , Hiraoka, M. (2018) Detection of Spherical Gold Fiducials in kV X-Ray Images Using Intensity-Estimation-Based Method. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 7, 115-130. doi: 10.4236/ijmpcero.2018.71010.

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