Yonsei Med J.  2005 Feb;46(1):95-103. 10.3349/ymj.2005.46.1.95.

Comparison of Unmonochromatized Synchrotron Radiation and Conventional X-rays in the Imaging of Mammographic Phantom and Human Breast Specimens: A Preliminary Result

• Jung H
• Kim HJ
• Kim EK
• Hong JO
• Je JH
• Hwu Y
• Tsai WL
• Magaritondo G
• Yoo HS

• KMID: 2158118
• DOI: http://doi.org/10.3349/ymj.2005.46.1.95

Abstract

A simple imaging setup based on the principle of coherence-based contrast X-ray imaging with unmonochromatized synchrotron radiation was used for studying mammographic phantom and human breast specimens. The use of unmonochromatized synchrotron radiation simplifies the instrumentation, decreases the cost and makes the procedure simpler and potentially more suitable for clinical applications. The imaging systems consisted of changeable silicon wafer attenuators, a tungsten slit system, a CdWO4 scintillator screen, a CCD (Charge Coupled Device) camera coupled to optical magnification lenses, and a personal computer. In preliminary studies, a spatial resolution test pattern and glass capillary filled with air bubbles were imaged to evaluate the resOolution characteristics and coherence-based contrast enhancement. Both the spatial resolution and image quality of the proposed system were compared with those of a conventional mammography system in order to establish the characteristic advantages of this approach. The images obtained with the proposed system showed a resolution of at least 25micrometer on the test pattern with much better contrast, while the images of the capillary filled with air bubbles revealed coherence-based edge enhancement. This result shows that the coherence-based contrast imaging system, which emphasizes the refraction effect from the edge of materials of different refractive indexes, is applicable to imaging studies in fundamental medicine and biology, although further research works will be required before it can be used for clinical applications.

Keyword

Synchrotron radiation; mammography

MeSH Terms

Breast Diseases/*radiography
Comparative Study
Female
Humans
Mammography/*instrumentation/*methods
*Phantoms, Imaging
Pilot Projects
Research Support, Non-U.S. Gov't
*Synchrotrons
X-Rays

Figure

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  Fig. 1 Energy spectra of PLS white beam for different silicon wafers thicknesses. A series of attenuators was placed in the beam upstream of the sample position and the energy range and the photon flux were adjusted in the range of 6-25 keV and 1011 - 1012 photons/mm2/sec, respectively.

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  Fig. 2 Schematic diagram of unmonochromatized synchrotron radiation imaging set-up at PLS 5C1 beamline. Synchrotron radiation X-rays passing through the test objects then interact with the scintillator screen before being converted to a visible light image. The optical images were magnified by optical lenses, captured by a CCD camera and transferred to a computer for data acquisition and analysis.

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  Fig. 3 The images of the spatial resolution test pattern; (a) complete image, (b) small input field of 14 line pairs mm-1, and (C) small input field of 20 line pairs mm-1, obtained by the conventional mammography system (GE Senographe DMR) and (d) complete image, (e) small input field of 14 line pairs mm-1, and (f) small input field of 20 line pairs mm-1, obtained by the PLS 5C1 synchrotron imaging system. The PLS 5C1 unmonochromatized synchrotron imaging system provided a resolution of at least 20 line-pairs mm-1 (25 µm) with the resolution test pattern compared to the 14 line-pairs mm-1 (≈36 µm) spatial resolution obtained with the conventional mammography system.

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  Fig. 4 The modulation transfer function (MTF) of the PLS 5C1 SR imaging system at 1.5 × and 9.5 × optical magnifications for the horizontal direction in relation to the incident beam. The spatial resolution (10% of MTF) was found to be about 60 line pairs/mm (corresponds to 8.3 nm) for the imaging setup with 1.5 × optical magnification.

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  Fig. 5 The PLS 5C1 unmonochromatized synchrotron radiation images of a glass capillary tube filled with air bubbles for various object-to-detector (scintillator) distances viz. for (a) to (f), 50, 100, 200, 250, 300, and 470 mm, respectively. The sequential images illustrate the effect of the coherence-based contrast which operates by the mechanism of refraction-based edge enhancement within a certain range of object-detector distance values. (g) Cross-sectional intensity profile of the bubble along the vertical line in (f) (arbitrary units scaled to each other).

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  Fig. 6 Schematic and images of the mammographic accreditation phantom (Gammex RMI 156); (a) a schematic view of the mammographic phantom giving the test object sizes and positions, (b) radiographic image obtained with the conventional mammographic system, (c) partial image of artificial microcalcification obtained with the conventional mammography system, (d) partial image of artificial microcalcification obtained with the PLS 5C1 synchrotron imaging system. The synchrotron image of artificial microcalcification shows more details and clearer boundaries.

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  Fig. 7 Images of human breast cancer specimens preserved in formalin acquired from conventional mammographic system and the PLS 5C1 unmonochromatized synchrotron imaging system; (a) gross photographic image of specimen, (b) whole image, and (c) small input field of image b obtained with the conventional mammography system, (d) complete image, and (e) small input field of image obtained with the synchrotron radiation imaging system. In the images (b)-(e), white spots show the images of the microcalcifications detected in the breast cancer tissue. In the synchrotron radiation images, the contrast was enhanced and the details were depicted more sharply than in the conventional images. In particular, the edges of the calcification and mass were well defined. Here, the synchrotron radiation images were inverted for the purpose of comparison with the mammographic images. (In the synchrotron radiation images, the upper and right white bars indicate the needle used for hanging the specimen during image acquisition.)

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