Baseline Correction in Computed Radiography Images with 1D Morphological Filter
1
조회
0
다운로드
0
인용
0
참고문헌
키워드
초록
Computed radiography (CR) systems, which convert an analog signal recorded on a cassette into a digital image, combine the characteristics of analog and digital imaging systems. Compared to digital radiography (DR) systems, CR systems have presented difficulties in evaluating system performance because of their lower detective quantum efficiency, their lower signal-to-noise ratio (SNR), and lower modulation transfer function (MTF). During the step of energy-storing and reading out, a baseline offset occurs in the edge area and makes low-frequency overestimation. The low-frequency offset component in the line spread function (LSF) critically affects the MTF and other image-analysis or qualification processes. In this study, we developed the method of baseline correction using mathematical morphology to determine the LSF and MTF of CR systems accurately. We presented a baseline correction that used a morphological filter to effectively remove the low-frequency offset from the LSF. We also tried an MTF evaluation of the CR system to demonstrate the effectiveness of the baseline correction. The MTF with a 3-pixel structuring element (SE) fluctuated since it overestimated the low-frequency component. This overestimation led the algorithm to over-compensate in the low-frequency region so that high-frequency components appeared relatively strong. The MTFs with between 11- and 15-pixel SEs showed little variation. Compared to spatial or frequency filtering that eliminated baseline effects in the edge spread function, our algorithm performed better at precisely locating the edge position and the averaged LSF was narrower.
Abstract
Computed radiography (CR) systems, which convert an analog signal recorded on a cassette into a digital image, combine the characteristics of analog and digital imaging systems. Compared to digital radiography (DR) systems, CR systems have presented difficulties in evaluating system performance because of their lower detective quantum efficiency, their lower signal-to-noise ratio (SNR), and lower modulation transfer function (MTF). During the step of energy-storing and reading out, a baseline offset occurs in the edge area and makes low-frequency overestimation. The low-frequency offset component in the line spread function (LSF) critically affects the MTF and other image-analysis or qualification processes. In this study, we developed the method of baseline correction using mathematical morphology to determine the LSF and MTF of CR systems accurately. We presented a baseline correction that used a morphological filter to effectively remove the low-frequency offset from the LSF. We also tried an MTF evaluation of the CR system to demonstrate the effectiveness of the baseline correction. The MTF with a 3-pixel structuring element (SE) fluctuated since it overestimated the low-frequency component. This overestimation led the algorithm to over-compensate in the low-frequency region so that high-frequency components appeared relatively strong. The MTFs with between 11- and 15-pixel SEs showed little variation. Compared to spatial or frequency filtering that eliminated baseline effects in the edge spread function, our algorithm performed better at precisely locating the edge position and the averaged LSF was narrower.
참고문헌 (20)
- Morgan RH, "The frequency response characteristics of x-ray films and screens", Am. J. Roentgenol, 92(2), pp.426~440 (1964)
- Rossmann K, "Point spread-function, line spreadfunction, and modulation transfer function. Tools for the study of imaging systems", Radiology, 93(2), pp.257~272 (1969)
- Modulation transfer function of screen-film systems, "Doi K", International Commission on Radiation Units and Measurements, ~, pp.IICRU Report 41 (1986)
- Sones RA, "A method to measure the MTF of digital x-ray systems", Med. Pys, 11(2), pp.166~171 (1984)
- Hillen W, "Imaging performance of a digital storage phosphor system", Med. Phys, 11(2), pp.744~751 (1987)
- Morishita J, "Comparison of two methods for ac-curate measurement of modulation transfer functions of screen-film systems", Med. Phys, 22(2), pp.193~200 (1995)
- Barrett HH, "Radiological imaging: The theory of image formation, detection, and processing" (1996), Elsevier Science
- Bushberg JT, "The essential physics of medical imaging" (2011), Lippincott Williams & Wilkins: A Wolters Kluwer Company
- Samei E, "RSNA Categorical Course in Diagnostic Radiology Physics" (2003)
- Cunningham IA, "Signal and noise in modulation transfer function determinations using the slit, wire, and edge techniques", Med. Phys, 19(4), pp.1037~1044 (1992)
- International electrotechnical commission, "international standard IEC62220-1: Medical electrical equipment-Characteristics of digital imaging devices-Part 1: Determination of the detective quantum efficiency", IEC, ~ (2003)
- 김정민, "CR X선 영상의 복합잡음 감소에 관한 연구", 방사선기술과학, 30(1), pp.1~6 (2007), 대한방사선과학회
- 정회원, "다양한 디지털 방사선 시스템의 물리적 영상 특성 조사", 방사선기술과학, 40(3), pp.363~370 (2017), 대한방사선과학회[DOI]
- Neitzel U, "Determination of the modulation transfer function using the edge method: Influence of scattered radiation", Med. Phys, 31(12), pp.3485~3491 (2004)
- Shetty CM, "Computed Radiography Image Artifacts Revisited", AJR, 196, pp.W37~W47 (2011)
- 김용관, "Accurate Evaluation of Modulation Transfer Function Using the Fourier Shift Theorem", Journal of the Korean Physical Society, 71(12), pp.1064~1068 (2017), 한국물리학회
- Mackenzie A, "Validation of a method to convert an image to appear as if acquired using a different digital detector", Proc. SPIE, 7961 (2011)[DOI]
- Maragos P, "Morphological filters-Part I: Set-theoretic analysis", Proceedings of IEEE Transactions on Acoustics Speech and Signal, 35(8), pp.1153~1169 (1987)
- Maragos P, "Morphological filters-Part II : Their relations to median, order-statistic, and stack filters", Proceedings of IEEE Transactions on Acoustics Speech and Signal, 35(8), pp.1170~1184 (1987)
- Solomon C, "Fundamentals of digital image processing", pp.197~232 (2011), WILEY-BLACKWELL: John Wiley & Sons, Ltd