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Real-time phase-contrast imaging at the Kurchatov synchrotron radiation source
ARTICLE IN PRESS Nuclear Instruments and Methods in Physics Research A 603 (2009) 167–169
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Real-time phase-contrast imaging at the Kurchatov synchrotron radiation source D.K. Pogoreliy , K.M. Podurets, N.S. Pavlova RRC Kurchatov Institute, 1 Kurchatov Square, Moscow 123182, Russia
a r t i c l e in fo
abstract
Available online 3 January 2009
Experiments on the real-time in-line phase imaging of biological objects at the second generation synchrotron radiation source are reported. High intensity ‘‘pink’’ beam was obtained using the reduced electron beam energy of the accelerator. Optimal conditions for phase-contrast imaging at the low coherence source are discussed. & 2009 Elsevier B.V. All rights reserved.
Keywords: Synchrotron radiation Phase contrast X-ray imaging
1. Introduction Recently, the phase-contrast methods of X-ray imaging are being intensively developed [1,2], which make possible to obtain images of low absorbing objects which consist of light elements. Thus it became possible to imaging biological objects, indistinguishable at traditional investigation based on absorption. The necessary condition of the phase-contrast appearance is the presence of local coherence of the X-rays. Unlike the unique third generation sources of synchrotron radiation, the second generation ones and the laboratory sources give limited opportunities for obtaining intensive beams of radiation with high degree of coherence, so when using these sources great attention should be paid to the optimal choice of the setup parameters according to the parameters of object and the aim of investigation. This is an important problem because these sources are accessible for a wider community of the researchers. This paper is dedicated to the development of method of phase-contrast imaging of biological objects at the second generation source of synchrotron radiation, the Kurchatov synchrotron radiation source (KSRS). Biological objects have complicated hierarchic structural organization at different scaling levels, so different experimental approaches are being developed for imaging structures with different characteristic dimensions. When the mean inhomogeneity size is about 1 mm or more, the crystal optics setup [3] should be chosen for registration of the phase shifts at X-ray wave passing through object. On the micrometer scale the in-line imaging technique with distant source is preferable. The first experiment on the in-line imaging at the KSRS was reported in Ref. [4], where X-ray film was used for image recording with the aim of the source size
Corresponding author. Tel.:+7499 1967351; Fax: +7499 1967723.
E-mail addresses: [email protected], [email protected] (D.K. Pogoreliy). 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.12.146
determination. In the present work the task was to optimize the experiment for digital registration for real-time image recording.
2. Experimental The experiments were carried out at the beam from the bending magnet of the KSRS. The vertical size of the KSRS source is close to 200 mm, which is less than the value reported in Ref. [4]. The difference is concerned with improvement of the magnetic system of the storage ring. Typical length of the beamlines at the KSRS is about ZosE15–20 m, so defining for the sample to detector distance ZodE1 m the geometrical smear is about 10 mm (Fig. 1). Width of the first Fresnel zone (lZod)1/2 in this conditions at wavelength l=0.1 nm also values to about 10 mm, so the phase contrast in this conditions should appear in the presence of the first bright oscillation of intensity at the edge of the object’s image. So the optimal condition of phase-contrast imaging using this source is closeness of three values: geometric smear, width of the first Fresnel zone and spatial resolution. According to this it is reasonable to use detector with spatial resolution about 5 mm. Such detector was produced using CCD-camera with microscope objective and single-crystal scintillator BGO. Experiments were carried out with monochromatic and ‘‘pink’’ SR beams. Images of the test and biological objects obtained with the monochromatic beam with E=10 keV formed by crystal monochromator demonstrate the pronounced phase-contrast manifested in bright edging of the object images (Fig. 2). But it is obvious that monochromatization with Dl/lE10 5, typical for crystal monochromators, is excessive in this case and merely leads to unjustified loss of intensity. In fact, in our case exposure time was several tens second what is unacceptable for real-time imaging. In order to improve the brightness of the beam it is possible to use the white SR beam but in regular conditions spectrum of the
ARTICLE IN PRESS 168
D.K. Pogoreliy et al. / Nuclear Instruments and Methods in Physics Research A 603 (2009) 167–169
Fig. 1. Scheme of the experiment.
Fig. 4. Frames of phase-contrast movie. (a) Fishing-line (0.5 mm diameter), and (b) head of the bug. Exposure time 100 ms.
Fig. 2. Samples of phase-contrast images obtained with monochromatic beam with energy 10 keV. (a) Phase-contrast image of fishing-line (0.5 mm diameter). (b) Middle part of bug’s paw. Exposure time 30 s.
the experiments were carried out with the ‘‘pink’’ beam which is obtained at the reduced energy of the electrons in the storage ring, in our case we used 1.6 GeV instead of the regular 2.5 GeV. At this energy quantity of the high-energy photons is drastically reduced, and photons with Eo6 keV do not propagate through the beamline Be-windows. So the beam spectra becomes nearly monochromatic with peak at 12 keV with FWHM about 6 keV. Calculated spectra of KSRS bending magnet (at the same current) after Be-windows of beamline are shown on Fig. 3. In spite of losing maximum intensity by order of magnitude rough estimate of gain gives value about 300 times. Images obtained with ‘‘pink’’ beam almost does not differ from the images obtained with monochromatic beam—only the first intensity oscillation is clearly seen but exposure time was only about 100 ms. This improved intensity provides possibility to get real-time images and to make recording of a moving object. Phase-contrast image acquisition of moving model object and alive earth-warm and alive bug Pyrrhocoris apterus were carried out. In the pictures of a bug moving parts of the body and displacement of the internal features are clearly seen (Fig. 4).
3. Conclusion Fig. 3. SR spectra of Kurchatov SR source with energy of electron beam 2.5 and 1.6 GeV.
KSRS spreads to the energy about 40–50 keV and such highenergy quanta do not form the contrast and produce only background in the image. So for decrease of the exposure time
The experiments demonstrated possibility of phase-contrast imaging of objects with weak absorption using second generation sources with limited coherency. Also the potential to make realtime phase-contrast imaging (‘‘phase-contrast movie’’) of biological and other low Z-objects at Kurchatov SR source was demonstrated.
ARTICLE IN PRESS D.K. Pogoreliy et al. / Nuclear Instruments and Methods in Physics Research A 603 (2009) 167–169
References [1] K.M. Podurets, V.A. Somenkov, S. Shilstein, Zhurnal Tekhnicheskoy Fiziki 58 (6) (1989) 115. [2] A. Snigirev, I. Snigireva, V.G. Kohn, I. Schelokov, Rev. Sci. Instr. 66 (1995) 5486.
169
[3] A.A. Manushkin, D.K. Pogoreliy, K.M. Podurets, A.A. Vazina, T.S. Lagoda, V.A. Somenkov, Nucl. Instr.and Meth. Phys. Res. A 575 (2007) 225. [4] A.A. Snigirev, V.G. Kohn, E.H. Muhamedjanov, I.I. Snigireva, A.G. Maevskiy, V.V. Kvardakov, M.V. Kovalchuk, Poverkhnost. Rentgenovskie, sinchrotronnyie i neytronnie issledovaniya. 2007, No. 1, pp. 3–9.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Real-time phase-contrast imaging at the Kurchatov synchrotron radiation source D.K. Pogoreliy , K.M. Podurets, N.S. Pavlova RRC Kurchatov Institute, 1 Kurchatov Square, Moscow 123182, Russia
a r t i c l e in fo
abstract
Available online 3 January 2009
Experiments on the real-time in-line phase imaging of biological objects at the second generation synchrotron radiation source are reported. High intensity ‘‘pink’’ beam was obtained using the reduced electron beam energy of the accelerator. Optimal conditions for phase-contrast imaging at the low coherence source are discussed. & 2009 Elsevier B.V. All rights reserved.
Keywords: Synchrotron radiation Phase contrast X-ray imaging
1. Introduction Recently, the phase-contrast methods of X-ray imaging are being intensively developed [1,2], which make possible to obtain images of low absorbing objects which consist of light elements. Thus it became possible to imaging biological objects, indistinguishable at traditional investigation based on absorption. The necessary condition of the phase-contrast appearance is the presence of local coherence of the X-rays. Unlike the unique third generation sources of synchrotron radiation, the second generation ones and the laboratory sources give limited opportunities for obtaining intensive beams of radiation with high degree of coherence, so when using these sources great attention should be paid to the optimal choice of the setup parameters according to the parameters of object and the aim of investigation. This is an important problem because these sources are accessible for a wider community of the researchers. This paper is dedicated to the development of method of phase-contrast imaging of biological objects at the second generation source of synchrotron radiation, the Kurchatov synchrotron radiation source (KSRS). Biological objects have complicated hierarchic structural organization at different scaling levels, so different experimental approaches are being developed for imaging structures with different characteristic dimensions. When the mean inhomogeneity size is about 1 mm or more, the crystal optics setup [3] should be chosen for registration of the phase shifts at X-ray wave passing through object. On the micrometer scale the in-line imaging technique with distant source is preferable. The first experiment on the in-line imaging at the KSRS was reported in Ref. [4], where X-ray film was used for image recording with the aim of the source size
Corresponding author. Tel.:+7499 1967351; Fax: +7499 1967723.
E-mail addresses: [email protected], [email protected] (D.K. Pogoreliy). 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.12.146
determination. In the present work the task was to optimize the experiment for digital registration for real-time image recording.
2. Experimental The experiments were carried out at the beam from the bending magnet of the KSRS. The vertical size of the KSRS source is close to 200 mm, which is less than the value reported in Ref. [4]. The difference is concerned with improvement of the magnetic system of the storage ring. Typical length of the beamlines at the KSRS is about ZosE15–20 m, so defining for the sample to detector distance ZodE1 m the geometrical smear is about 10 mm (Fig. 1). Width of the first Fresnel zone (lZod)1/2 in this conditions at wavelength l=0.1 nm also values to about 10 mm, so the phase contrast in this conditions should appear in the presence of the first bright oscillation of intensity at the edge of the object’s image. So the optimal condition of phase-contrast imaging using this source is closeness of three values: geometric smear, width of the first Fresnel zone and spatial resolution. According to this it is reasonable to use detector with spatial resolution about 5 mm. Such detector was produced using CCD-camera with microscope objective and single-crystal scintillator BGO. Experiments were carried out with monochromatic and ‘‘pink’’ SR beams. Images of the test and biological objects obtained with the monochromatic beam with E=10 keV formed by crystal monochromator demonstrate the pronounced phase-contrast manifested in bright edging of the object images (Fig. 2). But it is obvious that monochromatization with Dl/lE10 5, typical for crystal monochromators, is excessive in this case and merely leads to unjustified loss of intensity. In fact, in our case exposure time was several tens second what is unacceptable for real-time imaging. In order to improve the brightness of the beam it is possible to use the white SR beam but in regular conditions spectrum of the
ARTICLE IN PRESS 168
D.K. Pogoreliy et al. / Nuclear Instruments and Methods in Physics Research A 603 (2009) 167–169
Fig. 1. Scheme of the experiment.
Fig. 4. Frames of phase-contrast movie. (a) Fishing-line (0.5 mm diameter), and (b) head of the bug. Exposure time 100 ms.
Fig. 2. Samples of phase-contrast images obtained with monochromatic beam with energy 10 keV. (a) Phase-contrast image of fishing-line (0.5 mm diameter). (b) Middle part of bug’s paw. Exposure time 30 s.
the experiments were carried out with the ‘‘pink’’ beam which is obtained at the reduced energy of the electrons in the storage ring, in our case we used 1.6 GeV instead of the regular 2.5 GeV. At this energy quantity of the high-energy photons is drastically reduced, and photons with Eo6 keV do not propagate through the beamline Be-windows. So the beam spectra becomes nearly monochromatic with peak at 12 keV with FWHM about 6 keV. Calculated spectra of KSRS bending magnet (at the same current) after Be-windows of beamline are shown on Fig. 3. In spite of losing maximum intensity by order of magnitude rough estimate of gain gives value about 300 times. Images obtained with ‘‘pink’’ beam almost does not differ from the images obtained with monochromatic beam—only the first intensity oscillation is clearly seen but exposure time was only about 100 ms. This improved intensity provides possibility to get real-time images and to make recording of a moving object. Phase-contrast image acquisition of moving model object and alive earth-warm and alive bug Pyrrhocoris apterus were carried out. In the pictures of a bug moving parts of the body and displacement of the internal features are clearly seen (Fig. 4).
3. Conclusion Fig. 3. SR spectra of Kurchatov SR source with energy of electron beam 2.5 and 1.6 GeV.
KSRS spreads to the energy about 40–50 keV and such highenergy quanta do not form the contrast and produce only background in the image. So for decrease of the exposure time
The experiments demonstrated possibility of phase-contrast imaging of objects with weak absorption using second generation sources with limited coherency. Also the potential to make realtime phase-contrast imaging (‘‘phase-contrast movie’’) of biological and other low Z-objects at Kurchatov SR source was demonstrated.
ARTICLE IN PRESS D.K. Pogoreliy et al. / Nuclear Instruments and Methods in Physics Research A 603 (2009) 167–169
References [1] K.M. Podurets, V.A. Somenkov, S. Shilstein, Zhurnal Tekhnicheskoy Fiziki 58 (6) (1989) 115. [2] A. Snigirev, I. Snigireva, V.G. Kohn, I. Schelokov, Rev. Sci. Instr. 66 (1995) 5486.
169
[3] A.A. Manushkin, D.K. Pogoreliy, K.M. Podurets, A.A. Vazina, T.S. Lagoda, V.A. Somenkov, Nucl. Instr.and Meth. Phys. Res. A 575 (2007) 225. [4] A.A. Snigirev, V.G. Kohn, E.H. Muhamedjanov, I.I. Snigireva, A.G. Maevskiy, V.V. Kvardakov, M.V. Kovalchuk, Poverkhnost. Rentgenovskie, sinchrotronnyie i neytronnie issledovaniya. 2007, No. 1, pp. 3–9.