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https://doi.org/10.1016/S0360-3016(00)00748-3

has been cited by the following article:

• TITLE: Detection of Spherical Gold Fiducials in kV X-Ray Images Using Intensity-Estimation-Based Method

  AUTHORS: Masaki Kokubo, Masahiro Yamada, Akira Sawada, Nobutaka Mukumoto, Yuki Miyabe, Takashi Mizowaki, Masahiro Hiraoka

  KEYWORDS: Fiducial Marker Detection, Intensity Estimation

  JOURNAL NAME: International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Vol.7 No.1, February 28, 2018

  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).