High-resolution differential phase contrast imaging using a magnifying projection geometry with a microfocus x-ray source

Engelhardt, Martin; Baumann, J.; Schuster, M.; Kottler, Christian; Pfeiffer, Franz; Bunk, Oliver; Dávid, Christian

doi:10.1063/1.2743928

Cited by 128 publications

(97 citation statements)

References 20 publications

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“…3. In the present compact cone-beam geometry setup, the sensitivity is reduced by a factor of r 1 ∕l with r 1 being the source-to-sample and l the source-to-G1 distance (25,26). To correct for this, the reconstructed δ data was renormalized by a factor of l∕r 1 ¼ 1.2.…”

Section: Methodsmentioning

confidence: 99%

Experimental results from a preclinical X-ray phase-contrast CT scanner

Tapfer

Bech

Velroyen

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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114

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To explore the future clinical potential of improved soft-tissue visibility with grating-based X-ray phase contrast (PC), we have developed a first preclinical computed tomography (CT) scanner featuring a rotating gantry. The main challenge in the transition from previous bench-top systems to a preclinical scanner are phase artifacts that are caused by minimal changes in the grating alignment during gantry rotation. In this paper, we present the first experimental results from the system together with an adaptive phase recovery method that corrects for these phase artifacts. Using this method, we show that the scanner can recover quantitatively accurate Hounsfield units in attenuation and phase. Moreover, we present a first tomography scan of biological tissue with complementary information in attenuation and phase contrast. The present study hence demonstrates the feasibility of gratingbased phase contrast with a rotating gantry for the first time and paves the way for future in vivo studies on small animal disease models (in the mid-term future) and human diagnostics applications (in the long-term future).differential X-ray phase contrast | grating interferometer | X-ray imaging O ne of the main shortcomings of existing biomedical X-ray imaging systems is their weak contrast in soft tissue. This limitation can be addressed by phase-sensitive imaging methods that rely on the phase shift that X-rays undergo when passing through matter (1). The resultant refraction angle can be utilized as contrast mechanism in a grating-based interferometer in radiographic (2, 3) and tomographic acquisition mode (4, 5). In a computed tomography scan, quantitative information about the sample's composition can be extracted-i.e., the linear attenuation coefficient μ and decrement of the refractive index δ can be reconstructed (6-8). Because the grating-based phase-contrast imaging method is compatible with X-ray tube sources, when operated as Talbot-Lau interferometer (9), a translation to a clinical application scenario is currently discussed with great enthusiasm in the research community. Recent studies with laboratory X-ray sources have shown excellent imaging results with respect to softtissue contrast (10)(11)(12)(13)(14). In order to explore the envisioned clinical potential, we have developed a first preclinical phase-contrast CT scanner. This development represents an important milestone in the translation of phase-contrast imaging to clinical settings, as all grating-based phase-contrast setups, which are reported in the literature so far, use a rotating sample for tomographic scans. Because this mode of operation is obviously not preferable for intended in vivo animal studies, we have explored with this work the step from rotating sample to rotating gantry. The main challenge in this translation process was mechanical stability regarding the required precise alignment of the X-ray optical components (gratings). Even mechanical movements of either grating of only fractions of a micrometer during gantry rotation already c...

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Section: Methodsmentioning

confidence: 99%

Experimental results from a preclinical X-ray phase-contrast CT scanner

Tapfer

Bech

Velroyen

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

145

114

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“…The raw data were median-filtered for noise reduction (kernel size 3 Â 3). To correct for the cone-beam geometry, phase projections were renormalized 44 by a factor of d 1 d o ¼ 2:11, where d o denotes the focus sample distance. The measurement of the phantom was performed with an effective pixel size of 23.1 lm.…”

Section: B Micro Computed Tomographymentioning

confidence: 99%

Implementation of a double-grating interferometer for phase-contrast computed tomography in a conventional system nanotom® m

et al. 2018

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Visualizing the internal architecture of large soft tissue specimens within the laboratory environment in a label-free manner is challenging, as the conventional absorption-contrast tomography yields a poor contrast. In this communication, we present the integration of an X-ray double-grating interferometer (XDGI) into an advanced, commercially available micro computed tomography system nanotom ® m with a transmission X-ray source and a micrometer-sized focal spot. The performance of the interferometer is demonstrated by comparing the registered three-dimensional images of a human knee joint sample in phase- and conventional absorption-contrast modes. XDGI provides enough contrast (1.094 ± 0.152) to identify the cartilage layer, which is not recognized in the conventional mode (0.287 ± 0.003). Consequently, the two modes are complementary, as the present XDGI set-up only reaches a spatial resolution of (73 ± 6) μ m, whereas the true micrometer resolution in the absorption-contrast mode has been proven. By providing complimentary information, XDGI is especially a supportive quantitative method for imaging soft tissues and visualizing weak X-ray absorbing species in the direct neighborhood of stronger absorbing components at the microscopic level.

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“…Absorption-to-DPC geometric scaling factor grating, i.e., the G 2 grating, typically with a 50% duty cycle, 3,4,6,[9][10][11]15 is placed in front of the detector. This grating is translated by a fraction of the grating pitch along the u axis m times: u g = kp 2 /m (k = 1, 2, .…”

Section: Iia Differential Phase Contrast Imagingmentioning

confidence: 99%

“…Although numerous studies have been conducted to demonstrate the feasibility of differential phase contrast (DPC) imaging [1][2][3][4][5][6][7] and DPC computed tomography (DPC-CT) (Refs. 8-16) using a Talbot-Lau interferometer, several questions remain unanswered on how to fully understand and optimize such systems for clinical applications.…”

Section: Introductionmentioning

confidence: 99%

Fundamental relationship between the noise properties of grating-based differential phase contrast CT and absorption CT: Theoretical framework using a cascaded system model and experimental validation

Bevins

Zambelli

et al. 2013

Med. Phys.

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Purpose: Using a grating interferometer, a conventional x-ray cone beam computed tomography (CT) data acquisition system can be used to simultaneously generate both conventional absorption CT (ACT) and differential phase contrast CT (DPC-CT) images from a single data acquisition. Since the two CT images were extracted from the same set of x-ray projections, it is expected that intrinsic relationships exist between the noise properties of the two contrast mechanisms. The purpose of this paper is to investigate these relationships. Methods: First, a theoretical framework was developed using a cascaded system model analysis to investigate the relationship between the noise power spectra (NPS) of DPC-CT and ACT. Based on the derived analytical expressions of the NPS, the relationship between the spatial-frequencydependent noise equivalent quanta (NEQ) of DPC-CT and ACT was derived. From these fundamental relationships, the NPS and NEQ of the DPC-CT system can be derived from the corresponding ACT system or vice versa. To validate these theoretical relationships, a benchtop cone beam DPC-CT/ACT system was used to experimentally measure the modulation transfer function (MTF) and NPS of both DPC-CT and ACT. The measured three-dimensional (3D) MTF and NPS were then combined to generate the corresponding 3D NEQ. Results: Two fundamental relationships have been theoretically derived and experimentally validated for the NPS and NEQ of DPC-CT and ACT: (1) the 3D NPS of DPC-CT is quantitatively related to the corresponding 3D NPS of ACT by an inplane-only spatial-frequency-dependent factor 1/f 2 , the ratio of window functions applied to DPC-CT and ACT, and a numerical factor C g determined by the geometry and efficiency of the grating interferometer. Note that the frequency-dependent factor is independent of the frequency component f z perpendicular to the axial plane. (2) The 3D NEQ of DPC-CT is related to the corresponding 3D NEQ of ACT by an f 2 scaling factor and numerical factors that depend on both the attenuation and refraction properties of the image object, as well as C g and the MTF of the grating interferometer. Conclusions: The performance of a DPC-CT system is intrinsically related to the corresponding ACT system. As long as the NPS and NEQ of an ACT system is known, the corresponding NPS and NEQ of the DPC-CT system can be readily estimated using additional characteristics of the grating interferometer.

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High-resolution differential phase contrast imaging using a magnifying projection geometry with a microfocus x-ray source

Cited by 128 publications

References 20 publications

Experimental results from a preclinical X-ray phase-contrast CT scanner

Experimental results from a preclinical X-ray phase-contrast CT scanner

Implementation of a double-grating interferometer for phase-contrast computed tomography in a conventional system nanotom® m

Fundamental relationship between the noise properties of grating-based differential phase contrast CT and absorption CT: Theoretical framework using a cascaded system model and experimental validation

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