564 Table The characteristics of 3 kinds of photostimulable phosphor plates System Type Characteristics A RP-5PM Photostimulable phosphor plate for ph

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1 563 原著 Code No. 520 松尾 1, 2 悟 3 杜下淳次 1 4 片渕哲朗 2 藤田広志緒言 X phase contrast mammography PCM system X X X 1 12 / X 7, 8, 11 13, 20 computed radiography CR 8, 12, Evaluation of Edge Enhancement Effect of Phase Contrast Imaging Using Newly-developed Photostimulable Phosphor Plate Satoru Matsuo, 1, 2 Junji Morishita, 3 Tetsuro Katafuchi, 4 and Hiroshi Fujita 2 1 Department of Radiology, Shiga University of Medical Science 2 Department of Intelligent Image Information, Graduate School of Medicine, Gifu University 3 Department of Health Sciences, Faculty of Medical Sciences, Kyushu University 4 Department of Radiological Technology, Gifu University of Medical Science Received December 1, 2011; Revision accepted March 12, 2012 Code No. 520 Summary We investigated whether the use of a newly developed columnar-crystal-type photostimulable-phosphor plate (CP1M200, referred to as system C) helps to provide improved edge-enhanced effect in phase contrast imaging. Physical characteristics of 2 conventional particulate-crystal-type photostimulable-phosphor plates (RP-5PM, referred to as system A and RP-6M, referred to as system B) and system C were measured. Then, an acrylic plate phantom and RMI152 phantom were imaged using 3 types of plates, and the edge-enhancement effects were evaluated based on the profile curve of the acrylic plate phantom. Visual evaluation of the RMI152 phantom images was conducted. The results showed that the modulation transfer function (MTF) of system C was superior to those of the other systems. The WS of system C was superior to those of the other systems in the low frequency band region, and inferior to those of the other systems in the high frequency band region. The presence of an edge-enhanced image was not detectable in the profile curve of the acrylic plate in system A, although that was shown in systems B and C due to their excellent sharpness. In the visual image evaluation of the RMI152 phantom, image quality of system C was superior to those of the other systems. Phase contrast imaging with a digital detector of a columnar-crystal-type photostimulable-phosphor plate is considered to provide improved edge-enhancement over that of conventional plates. Key words: phase-contrast imaging, edge-enhancement, photostimulable phosphor plate, columnar crystal type *Proceeding author Vol. 68 No. 5 May 2012

2 564 Table The characteristics of 3 kinds of photostimulable phosphor plates System Type Characteristics A RP-5PM Photostimulable phosphor plate for phase contrast mammography Particulate type BaFX phosphor Thickness of phosphor layer: RP-5PM>RP-6M B RP-6M Photostimulable phosphor plate for mammography (contact imaging) Particulate type BaFX phosphor C CP1M200 Photostimulable phosphor plate for mammography (contact imaging) Columnar crystal type CsBr phosphor / 20 flat panel detector FPD / CR FPD MTF / 22 X / 18 X X X X 23, 24 presampled modulation transfer function MTF wiener spectrum; WS 10 RMI 使用機器および実験方法 CR Mermaid X MGU-100B REGIUS MODEL190 3 Table C A B C CsBr A B BaFI 0.1 mm X X 65 cm 49 cm mm cm mm mm ThinkCentre IBM region of interest; ROI, ROI

3 MTF WS X detective quantum efficiency DQE 25 International Electrotechnical Commission IEC Mo/Mo RQA-M2 : 28 kv cm X 2.0 mm RQA-M2 28 kv CR μgy radiation monitor system model 9015 raw data ROI ROI MTF edge spread function ESF CR mm cm ESF ESF line spread function LSF LSF MTF LSF MTF LSF MTF MTF MTF X MTF 7, 8, WS RQA-M2 28 kv μgy 20 ROI CR 20 WS 3 60 WS WS c WS m(u) WS c(u) 1 29 WS m(u)=ws c(u/m)/m 2 1 u M 1-2 X 10 mm 28 kv 5 mas 28 kv 16 mas Fig X S p 19 Fig. 1 X I air X I acrylic X I I 10 X I 10% 2 3 I air I 10% X I air10% I acrylic I 10% X I acrylic10% I acrylic10% I air10% D 1 D 2 4 X S p I air10%=i air I 10% 2 Vol. 68 No. 5 May 2012

4 566 Fig. 2 Input-output characteristics of 3 different types of photostimulable phosphor plates. Fig. 1 I acrylic10%=i acrylic+i 10% 3 S p=(i air10% I acrylic10%)/(d 2 D 1) An example of edge-enhancement image by phase contrast imaging and illustration of profile curve of the image. 3 RMI Diamondcrysta RDT23IWLM-D 0 10 cycles/mm 1.0 cycle/mm 1.0 cycle 10 3 RMI 結果 Fig. 2 log rel. Exp MTF 30 Fig. 3 3 MTF 2.0 cycles/mm MTF A B C A B C 0.769

5 567 a b Fig. 3 Presampled MTFs of 3 different types of photostimulable phosphor plates in the scanning direction of laser beam. (a) contact imaging (b) 1.75 times magnification imaging a b Fig. 4 WSs of 3 different types of photostimulable phosphor plates in the scanning direction of laser beam. (a) contact imaging (b) 1.75 times magnification imaging WS 3 31 Fig. 4 3 WS C WS 3 WS C A B WS Fig. 5 a b a Vol. 68 No. 5 May 2012

6 568 a b Fig. 5 Profile curves of the acrylic plate edge, obtained with 3 different types of photostimulable phosphor plates for (a) contact image and (b) phase contrast image. Fig. 6 Images of acrylic phantom of screws obtained with 3 different types of photostimulable phosphor plates for phase contrast images. S p A B C b A B C S p A B C S p Fig. 6 C > B > A A > C > B 10 Fig. 7 C > B > A cycles/mm C A B

7 569 Fig. 7 De-composed images of acrylic phantom of screws obtained with 3 different types of photostimulable phosphor plates by phase contrast imaging, all of which are processed with the band-pass filter. Fig RMI-152 C > B > A C A = B = C 3. 考察 C A B A B CR X X X WS Q 5 32 (. ) G MTF ( uv, ) WSQ ( uv, ) = q q G 5 q q d q d X 3 C CsBr X A B BaFI 23, 24 Fig. 4 3 q q d C A B A q d WS Q MTF 1.0 q d Vol. 68 No. 5 May 2012

8 570 Fig. 8 The profile curve of de-composed images of acrylic phantom obtained by the band-pass filter. (a) cycles/mm (b) cycles/mm C A B 0.5 cycle/mm WS WS Q MTF 10.0 cycles/mm WS S p 60 X C B A Fig. 6 C A B MTF C A B WS 3 C B 6.0 cycles/mm 1.75 C WS B Fig. 9 Fig cycles/mm cycles/mm X 3 pixel C A B Fig. 7 Fig. 8 C 4. 結語 /

9 571 Fig. 9 Profile curves of phantom images, shown in Fig. 7, to the x-axis (average value of the 3 pixels in the center) in the spatial frequency bands cycles/mm and cycles/mm. (a) cycles/mm (b) cycles/mm a b 謝辞参考文献 1 Wilkins SW, Gureyev TE, Gao DA, et al. Phase-contrast imaging using polychromatic hand x rays. Nature 1996; 384: Pogany A, Gao D, Wilkins SW. Contrast and resolution in imaging with a microfocus x-ray source. Rev Sci Instrum 1997; 68(7): Fitzgerald R. Phase-sensitive x-ray imaging. Phys Today 2000; 53(7): Monnin P, Bulling S, Hoszowska J, et al. Quantitative characterization of edge enhancement in phase contrast x-ray imaging. Med Phys 2004; 31(6): Kotre CJ, Birch IP. Phase contrast enhancement of x-ray mammography: a design study. Phys Med Biol 1999; 44(11): Ishisaka A, Ohara H, Honda C. A new method of analyzing edge effect in phase contrast imaging with incoherent x-rays. Opt Rev 2000; 7(6): X X X 2002; 22(1): X X 2002; 65(7): Wu X, Liu H. Clinical implementation of x-ray phase-contrast imaging: theoretical foundations and design considerations. Med Phys 2003; 30(8): Vol. 68 No. 5 May 2012

10 Wu X, Liu H. A new theory of phase-contrast x-ray imaging based on Wigner distributions. Med Phys 2004; 31(9): X X KONICA MINOLTA TECHNOLOGY REPORT 2004; 1: ; 21(3): Matsuo S, Katafuchi T, Tohyama K, et al. Evaluation of edge effect due to phase contrast imaging for mammography. Med Phys 2005; 32(8): X 2005; 61(2): X 2006; 23(2): Tanaka T, Honda C, Matsuo S, et al. The first trial of phase contrast imaging for digital full-field mammography using a practical molybdenum x-ray tube. Invest Radiol 2005; 40(7): Honda C, Ohara H, Gido T. Image quality of phase contrast mammography. Digital Mammography. Zwiggelaar R (Ed.), Springer Lectures Notes in Computer Science (LNCS) series 2006; LNCS4046: ; 23(4): Matsuo S, Fujita H, Morishita J, et al. Preliminary evaluation of a phase contrast imaging with digital mammography. Digital Mammography. Krupinski EA (Ed.), Springer Lectures Notes in Computer Science (LNCS) series 2008; LNCS5116: Yamazaki A, Ichikawa K, Kodera Y. Investigation of physical image characteristics and phenomenon of edge enhancement by phase contrast using equipment typical for mammography. Med Phys 2008; 35(11): Matsuo S, Morishita J, Katafuchi T, et al. Image-quality assessment method for digital phase-contrast imaging based on two-dimensional power spectral analysis. Radiol Phys Technol 2012; 5(1): ; 60(3): CsBr CR KONICA MINOLTA TECH- NOLOGY REPORT 2006; 3: REGIUS210 CR / CP1S200 KONICA MINOLTA TECHNOLOGY REPORT 2011; 8: IEC , Ed.1.0: Medical electrical equipment-characteristics of digital X-ray imaging devices-part 1-2: determination of detective quantum efficiency detectors used in mammography. International Electrotechnical Commission, IEC 61267, Ed. 2.0: Medical Diagnostic X-ray equipment- Radiation conditions for use in the determination of characteristics. International Electrotechnical Commission, FPD X 2008; 64(1): Doi K, Imhof H. Noise reduction by radiographic magnification. Radiology 1977; 122(2): CR FPD 2010; 66(9): Noise Power Spectrum. 2009; 65(12): Doi K, Holje G, Loo LN, et al. MTF s and Wiener spectra of radiographic screen-film systems. Washington, HHS Publication FDA , 図表の説明 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Table 3 3 MTF MTF a b 3 a b 3 a b 3 3 RMI-152 a b Fig cycles/mm cycles/mm X 3 pixel a cycles/mm b cycles/mm

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07_学術.indd Arts and Sciences computed radiography CRpresampled MTF Measurement of presampled MTFs with computed radiography (CR) by contrast method using smoothed square-wave. 1 16813 1, 2 1 1 1 2 Key words: contrast