Phase contrast enhancement of x-ray mammography: a design study

Kotre, C J; Birch, I P

doi:10.1088/0031-9155/44/11/312

Cited by 80 publications

(59 citation statements)

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“…Similarly, when d 2 is small, there will be no distance for phase-contrast effects to be expressed before being recorded at the image receptor. 8 For larger d 1 and d 2 , the tube loading becomes very high, and for increasing d 2 , consideration must be made of geometrical blurring and increasing radiation dose at the object if the receptor dose is kept constant. To demonstrate these trends, a set of images were produced for d 1 fixed at 2 m in conjunction with d 2 5 0, 1, 1.5, 2 and 2.5 m. A second set was recorded with d 2 fixed at 1 m, and d 1 5 2, 2.5, 3 and 3.5 m. In each case, a correction image identical to the test image but without the test object in place was also recorded.…”

Section: Phase-contrast Imagingmentioning

confidence: 99%

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Phase-contrast and magnification radiography at diagnostic X-ray energies using a pseudo-microfocus X-ray source

Kotre

Robson²

2014

BJR

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Cite this article as: Kotre CJ, Robson KJ. Phase-contrast and magnification radiography at diagnostic X-ray energies using a pseudo-microfocus X-ray source. Br J Radiol 2014;87:20130734. FULL PAPER Phase-contrast and magnification radiography at diagnostic X-ray energies using a pseudo-microfocus X-ray source 1 C J KOTRE, PhD Objective: To investigate the use of conventional diagnostic X-ray tubes for applications in which specialist microfocus sources are normally required. Methods: A conventional diagnostic X-ray tube was used in conjunction with a range of apertures to investigate improvements in spatial resolution using a line-pairs test object. Phase-contrast effects were investigated by varying source-to-object and object-to-receptor distances using a 2-French catheter as a clinically realistic test object.Results: For magnification radiography using a computed radiography receptor and conventional X-ray tube with a 1-mm nominal focus size, the limiting spatial resolution was improved from 3.55 line-pairs per millimetre, for a conventional contact image, to 5.6 line-pairs per millimetre, for a 32 magnified view with a 250-mm aperture. For inline phase-contrast radiography, phase contrast enhancement of a 2-French catheter was demonstrated, and the expected trends with variations in source-toobject and object-to-receptor distances were found.Images of a neonatal phantom demonstrated a subtle improvement in visibility of a superimposed 1-French catheter simulating a percutaneously inserted central catheter for no increase in patient radiation dose. Conclusion: Spatial resolution improvement and visible phase contrast can be produced in clinically relevant objects using a pseudo-microfocus geometry at X-ray energies in the normal diagnostic range, using conventional diagnostic X-ray tubes and image receptors. The disadvantages of the proposal are the large distances required to produce phase contrast and limitations imposed by the resulting tube loading. Advances in knowledge:It is possible to use conventional diagnostic X-ray equipment in applications that normally require microfocus X-ray sources. This presents some possibilities for clinical applications.The rotating anode X-ray tube is by far the most common X-ray source used in diagnostic radiology. The engineering compromises inherent in the bevelled tungsten-rhenium rotating anode design deliver a relatively high radiation output with an adequate field coverage and heat dissipation for most radiology work, combined with an X-ray focus size that does not lead to visible geometric unsharpness in normal use. A common nominal X-ray focus size for general radiography is 1.0 or 1.2 mm with a switchable 0.6-mm fine focus. Although these sizes cover normal medical radiographic imaging requirements, there are specialist applications where a microfocus X-ray source is required. Commercial laboratory microfocus X-ray units commonly operate at relatively low energies and at low output, the output being restricted by the heat capacity of the typically station...

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Section: Phase-contrast Imagingmentioning

confidence: 99%

“…8 Although this work has demonstrated some imaging advantages to this geometry, it is clear that it would be restricted to projections where the distances could be accommodated.…”

Section: Focus-to-image Receptor Distancementioning

confidence: 99%

Phase-contrast and magnification radiography at diagnostic X-ray energies using a pseudo-microfocus X-ray source

Kotre

Robson²

2014

BJR

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“…The in-line phase-contrast x-ray imaging is a technique using the free space diffraction of phase-shifted x-rays to form the interference fringes at tissues' boundaries and interfaces in images. [1][2][3][4][5][6][7][8] In fact, for over 100 years, the tissue attenuation differences have been the sole contrast mechanism for medical x-ray imaging. However, when x-rays traverse the body parts, as a wave x-rays undergo phase shifts as well.…”

Section: Introductionmentioning

confidence: 99%

“…The settings for the inline phase-sensitive imaging are similar to that of conventional x-ray imaging, provided a source with very small focal spot and a sufficiently large object-detector distance are required. 5,7,8 In the inline imaging setting, x-rays undergo phase shifts as traversing the imaged object, and then diffract freely over a sufficiently large distance before reaching the detector. In this way, the tissues' phase contrast manifests as the dark-bright diffraction fringes at tissues' boundaries and interfaces in the measured images.…”

Section: Introductionmentioning

confidence: 99%

Robustness of phase retrieval methods in x‐ray phase contrast imaging: A comparison

Yan

Liu

2011

Medical Physics

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Purpose: The robustness of the phase retrieval methods is of critical importance for limiting and reducing radiation doses involved in x-ray phase contrast imaging. This work is to compare the robustness of two phase retrieval methods by analyzing the phase maps retrieved from the experimental images of a phantom. Methods: Two phase retrieval methods were compared. One method is based on the transport of intensity equation (TIE) for phase contrast projections, and the TIE-based method is the most commonly used method for phase retrieval in the literature. The other is the recently developed attenuation-partition based (AP-based) phase retrieval method. The authors applied these two methods to experimental projection images of an air-bubble wrap phantom for retrieving the phase map of the bubble wrap. The retrieved phase maps obtained by using the two methods are compared. Results: In the wrap's phase map retrieved by using the TIE-based method, no bubble is recognizable, hence, this method failed completely for phase retrieval from these bubble wrap images. Even with the help of the Tikhonov regularization, the bubbles are still hardly visible and buried in the cluttered background in the retrieved phase map. The retrieved phase values with this method are grossly erroneous. In contrast, in the wrap's phase map retrieved by using the AP-based method, the bubbles are clearly recovered. The retrieved phase values with the AP-based method are reasonably close to the estimate based on the thickness-based measurement. The authors traced these stark performance differences of the two methods to their different techniques employed to deal with the singularity problem involved in the phase retrievals. Conclusions: This comparison shows that the conventional TIE-based phase retrieval method, regardless if Tikhonov regularization is used or not, is unstable against the noise in the wrap's projection images, while the AP-based phase retrieval method is shown in these experiments to be superior to the TIE-based method for the robustness in performing the phase retrieval.

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“…Also, for the radiography based on the phase shift mechanism, the absorbed dose is considerably lower in comparison to the conventional absorption radiography, see, e.g., refs. [1,2,3].…”

Section: Introductionmentioning

confidence: 99%

X-ray phase contrast imaging at MAMI

et al. 2006

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Abstract. Experiments have been performed to explore the potential of the low emittance 855 MeV electron beam of the Mainz Microtron MAMI for imaging with coherent X-rays. Transition radiation from a microfocused electron beam traversing a foil stack served as X-ray source with good transverse coherence. Refraction contrast radiographs of low absorbing materials, in particular polymer strings with diameters between 30 and 450 µm, were taken with a polychromatic transition radiation X-ray source with a spectral distribution in the energy range between 8 and about 40 keV. The electron beam spot size had standard deviation σ h = (8.6 ± 0.1) µm in the horizontal and σv = (7.5 ± 0.1) µm in the vertical direction. X-ray films were used as detectors. The source-to-detector distance amounted to 11.4 m. The objects were placed in a distance of up to 6 m from the X-ray film. Holograms of strings were taken with a beam spot size σv = (0.50 ± 0.05) µm in vertical direction, and a monochromatic X-ray beam of 6 keV energy. A good longitudinal coherence has been obtained by the (111) reflection of a flat silicon single crystal in Bragg geometry. It has been demonstrated that a direct exposure CCD chip with a pixel size of 13 × 13 µm 2 provides a highly efficient on-line detector. Contrast images can easily be generated with a complete elimination of all parasitic background. The on-line capability allows a minimization of the beam spot size by observing the smallest visible interference fringe spacings or the number of visible fringes. It has been demonstrated that X-ray films are also very useful detectors. The main advantage in comparison with the direct exposure CCD chip is the resolution. For the Structurix D3 (Agfa) X-ray film the standard deviation of the resolution was measured to be σ f = (1.2 ± 0.4) µm, which is about a factor of 6 better than for the direct exposure CCD chip. With the small effective X-ray spot size in vertical direction of σv = (1.2±0.3) µm and a geometrical magnification of up to 7.4 high-quality holograms of tiny transparent strings were taken in which the holographic information is contained in up to 18 interference fringes.PACS. 87.59.Bh X-ray radiography -52.59.Px Hard X-ray sources -41.50.+h X-ray beams and X-ray optics -07.85.Fv X-and gamma-ray sources, mirrors, gratings, and detectors -07.85.Nc X-ray and gamma-ray spectrometers

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Phase contrast enhancement of x-ray mammography: a design study

Cited by 80 publications

References 9 publications

Phase-contrast and magnification radiography at diagnostic X-ray energies using a pseudo-microfocus X-ray source

Phase-contrast and magnification radiography at diagnostic X-ray energies using a pseudo-microfocus X-ray source

Robustness of phase retrieval methods in x‐ray phase contrast imaging: A comparison

X-ray phase contrast imaging at MAMI

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