The Scheme of the Grating Interferometer Setup at ID19 Is Shown in Figure 1

Sztrokay et al. “Assessment of Grating-based X-ray Phase Contrast Computed Tomography for Differentiation of Invasive Ductal Darcinoma and Ductal Carcinoma in-situ in an Experimental Ex-vivo Set-up”

Supplementary Online Material

Supplementary Methods

The scheme of the grating interferometer setup at ESRF beamline ID19 is shown in Figure 1 of the main manuscript. Not shown are the wiggler and the monochromator on the left side of the specimen. The wiggler produces the X-rays; the double-crystal monochromator selects the desired photon energy for imaging. A summary of the most important beamline parameters is provided in Table S1 (see also [1]).

Table S1 ESRF beamline ID19 parameter used for the measurements presented in this manuscript.

Phase Contrast and Absorption Computed Tomography: The principle of grating-based PC-CT and the projection acquisition is explained in detail in [2-8]. The X-rays pass through the object and are attenuated and refracted. The refraction causes a change in the direction of the X-ray path, which can be measured indirectly using an interferometer as shown in Figure 1 of the main manuscript. The phase-contrast and the absorption-contrast images are acquired simultaneously with this method. The device consists of two x-ray optical gratings [9; 10]: the phase grating produces an interference pattern in discrete distances downstream the X-ray beam, and the analyzer grating is used to detect the pattern of several micrometer periods with a standard X-ray imaging detector by scanning the analyzer grating with respect to the phase grating [2]. The method can be transferred to standard laboratory sources by adding an additional absorbing transmission grating, which increases the coherence of the X-ray source.

The grating interferometer was placed 150 m downstream the highly coherent wiggler source at the experimental hutch of the beamline ID19 at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). The following gratings were used for our measurements: a silicon phase grating with a period of 4.8 m, and a thickness of 29.5 m; an absorption gold analyzer grating with a period of 2.4 m and a thickness of 74 m. The 9th fractional Talbot distance of 481 mm was chosen to achieve high sensitivity. From the detected changes of the interference pattern the absorption and the phase-contrast information is extracted simultaneously. For a full tomography scan, 1199 projection images from different angles are collected by rotating the specimen by 360 degrees. For every projection four phase-steps of the analyzer grating over one grating period were recorded. The tomographic reconstruction was performed using the standard filtered backprojection algorithm with a Hilbert filter for PC-CT and Ram-Lak filter for the standard absorption CT [4].

The specimens were measured with grating-based phase contrast using monochromatic radiation of 23.0 keV. The energy was optimized to the specimen size, which already had to be reduced to fit the field of view. The available energy range at the beamline ID19 for grating-based phase-contrast imaging is between 17 keV and 82 keV. Each set of gratings is optimized for a dedicated energy. Using the gratings at an energy deviating from the design energy is possible (see interferometers at laboratory sources with a broad spectrum), but reduces image quality significantly. We used a FReLoN CCD camera E2V-SN42 with a 125 m thick LuAG scintillator, and optics with an effective pixel size of 30 m for the measurements. Every 100th projection, 10 reference projections without the sample were acquired for flat field correction. The total exposure time of the measurement including the flat-field projections was 1:28 hours.

References

1Weitkamp T, Tafforeau P, Boller E, et al. (2010) Status and evolution of the ESRF beamline ID19. X-Ray Optics and Microanalysis, Proceedings, 1221:33-38.

2Weitkamp T, Diaz A, David C, et al. (2005) X-ray phase imaging with a grating interferometer. Optics Express, 13(16):6296-6304.

3Pfeiffer F, Weitkamp T, Bunk O, David C (2006) Phase retrieval and differential phase-contrast imaging with low-brilliance X-ray sources. Nat Phys, 2(4):258-261.

4Pfeiffer F, Kottler C, Bunk O, David C (2007) Hard x-ray phase tomography with low-brilliance sources. Phys Rev Lett, 98(10):108105.

5Pfeiffer F, Bunk O, David C, et al. (2007) High-resolution brain tumor visualization using three-dimensional x-ray phase contrast tomography. Phys Med Biol, 52(23):6923-6930. doi: S0031-9155(07)56900-9 [pii]

10.1088/0031-9155/52/23/010

6Takeda T, Momose A, Itai Y, Wu J, Hirano K (1995) Phase-Contrast Imaging with Synchrotron X-Rays for Detecting Cancer Lesions. Academic Radiology, 2(9):799-803.

7Momose A, Takeda T, Itai Y (1995) Phase-Contrast X-Ray Computed-Tomography for Observing Biological Specimens and Organic Materials. Review of Scientific Instruments, 66(2):1434-1436.

8Momose A, Yashiro W, Takeda Y, Suzuki Y, Hattori T (2006) Phase tomography by X-ray Talbot interferometry for biological imaging. Jpn J Appl Phys 1, 45(6A):5254-5262. doi: Doi 10.1143/Jjap.45.5254

9David C, Bruder J, Rohbeck T, et al. (2007) Fabrication of diffraction gratings for hard X-ray phase contrast imaging. Microelectron Eng, 84(5-8):1172-1177. doi: DOI 10.1016/j.mee.2007.01.151

10Reznikova E, Mohr J, Boerner M, Nazmov V, Jakobs PJ (2008) Soft X-ray lithography of high aspect ratio SU8 submicron structures. Microsyst Technol, 14(9-11):1683-1688. doi: DOI 10.1007/s00542-007-0507-x

Supplementary Movies - Legends

Supplementary Movie 1 Axial phase-contrast images of the tumor-bearing sample.

Supplementary Movie 2 Coronal phase-contrast images of the tumor-bearing sample.

Supplementary Movie 3 Axial absorption-contrast images of the tumor-bearing sample.

Supplementary Movie 4 Coronal absorption-contrast images of the tumor-bearing sample.

Supplementary Movie 5 Axial phase-contrast images of the unaffected sample.

Supplementary Movie 6 Coronal phase-contrast images of the unaffected sample.

Supplementary Movie 7 Axial absorption-contrast images of the unaffected sample.

Supplementary Movie 8 Coronal absorption-contrast images of the unaffected sample.