First evidence of phase-contrast imaging with laboratory sources and active pixel sensors

Olivo, Alessandro; Arvanitis, Costas D.; Bohndiek, Sarah E.; Clark, A.; Prydderch, M.; Turchetta, R.; Speller, Robert

doi:10.1016/j.nima.2007.08.154

Cited by 21 publications

(15 citation statements)

References 15 publications

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“…However, its speed is limited by the need to scan an analyzer grating. Techniques based on precisely aligned coded apertures have also shown phase-contrast effects in transmission image[12], but more than one exposure is needed to separate phase-contrast information from absorption.…”

mentioning

confidence: 99%

Single-shot x-ray differential phase-contrast and diffraction imaging using two-dimensional transmission gratings

et al. 2010

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We describe an x-ray differential phase contrast imaging method based on two-dimensional transmission gratings that are directly resolved by an x-ray camera. X-ray refraction and diffraction in the sample lead to variations of the positions and amplitudes of the grating fringes on the camera. These effects can be quantified through spatial harmonic analysis. The use of 2D gratings allows differential phase contrast in several directions to be obtained from a single image. When compared to previous grating-based interferometry methods, this approach obviates the need for multiple exposures and separate measurements for different directions, and thereby accelerates imaging speed.

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confidence: 99%

Single-shot x-ray differential phase-contrast and diffraction imaging using two-dimensional transmission gratings

et al. 2010

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“…Complementary metal-oxide semiconductor (CMOS) active pixel sensors (APS) are commonly used in commercial products such as digital cameras, mobile phones, and webcams and recent advancements have produced sensors suitable for use in scientific applications such as medical imaging. [18][19][20] The addressable read-out architecture characteristic of APS sensors provides fast full frame or region-ofinterest (ROI) read-out and allows for the construction of small pixel and large area sensors without the corresponding decrease in frame-rate associated with a sequential read-out. The increased read-out rate also allows the use of a more efficient scintillator without an increase in the number of saturated pixels.…”

Section: Introductionmentioning

confidence: 99%

“…However in the case of moving tumours, such as those located in the lung, the Planning Target Volume (PTV) is often defined to include the position of the tumour at all times 20 resulting in the irradiation of healthy tissue 4 . To ameliorate this effect and improve the therapeutic ratio information describing the motion of the tumour may be used to gate the treatment 5 , or possibly to adapt the delivery to account for the motion 6 .…”

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confidence: 99%

Imaging of moving fiducial markers during radiotherapy using a fast, efficient active pixel sensor based EPID

et al. 2011

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The purpose of this work was to investigate the use of an experimental CMOS (Complementary Metal-OxideSemiconductor) APS (Active Pixel Sensor) for tracking of moving fiducial markers during radiotherapy. The APS has an active area of 5.4 x 5.4 cm and maximum full frame read-out rate of 20 frame s −1 , with the option to read out a Region-Of-Interest (ROI) at an increased rate. It was coupled to a 4 mm thick ZnWO4 scintillator which provided a quantum efficiency (QE) of 8% for a 6 MV x-ray treatment beam. The APS was compared with a standard iViewGT flat panel amorphous Silicon (a-Si) Electronic Portal Imaging Device (EPID), with a QE of 0.34% and a frame-rate of 2.5 frame s −1 . To investigate the ability of the two systems to image markers, four gold cylinders of length 8 mm and diameter 0.8, 1.2, 1.6 and 2 mm were placed on a motion platform. Images of the stationary markers were acquired using the APS at a frame-rate of 20 frame s −1 , and a dose-rate of 143 MU min −1 to avoid saturation. EPID images were acquired at the maximum frame-rate of 2.5 frame s −1 , and a reduced dose-rate of 19 MU min −1 to provide a similar dose per frame to the APS. Signal-to-Noise Ratio (SN R) of the background signal and Contrast-to-Noise Ratio (CN R) of the marker signal relative to the background were evaluated for both imagers at doses of 0.125 to 2 MU. Image quality and marker visibility was found to be greater in the APS with SN R ∼5 times greater than in the EPID and CN R up to an order of magnitude greater for all four markers. To investigate the ability to image and track moving markers the motion platform was moved to simulate a breathing cycle with period 6 s, amplitude 20 mm and maximum speed 13.2 mm s −1 . At the minimum integration time of 50 ms a tracking algorithm applied to the APS data found all four markers with a success rate of ≥92% and positional error ≤90 µm. At an integration time of 400 ms the smallest marker became difficult to detect when moving. The detection of moving markers using the a-Si EPID was difficult even at the maximum dose-rate of 592 MU min −1 due to the lower QE and longer integration time of 400 ms. This work demonstrates that a fast read-out, high QE APS may be useful in the tracking of moving fiducial markers during radiotherapy. Further study is required to investigate the tracking of markers moving in 3-D in a treatment beam attenuated by moving patient anatomy. This will require a larger sensor with ROI read-out to maintain speed and a manageable data-rate.

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“…The results obtained with coherent X-ray phase imaging provided promising diagnostic capabilities, but the need for synchrotron sources has prevented their mainstream clinical use. Recently, partially coherent X-ray phase microscopy methods that use laboratory X-ray sources have been investigated in greater detail and shown to be diagnostically valuable [15].…”

Section: Introduction and Background 1phase Imaging With Partially Cmentioning

confidence: 99%

Using the phase-space imager to analyze partially coherent imaging systems: bright-field, phase contrast, differential interference contrast, differential phase contrast, and spiral phase contrast

Mehta

Sheppard

2010

Journal of Modern Optics

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Various methods that use large illumination aperture (i.e. partially coherent illumination) have been developed for making transparent (i.e. phase) specimens visible. These methods were developed to provide qualitative contrast rather than quantitative measurement -coherent illumination has been relied upon for quantitative phase analysis. Partially coherent illumination has some important advantages over coherent illumination and can be used for measurement of the specimen's phase distribution. However, quantitative analysis and image computation in partially coherent systems have not been explored fully due to the lack of a general, physically insightful and computationally efficient model of image formation. We have developed a phase-space model that satisfies these requirements. In this paper, we employ this model (called the phase-space imager) to elucidate five different partially coherent systems mentioned in the title. We compute images of an optical fiber under these systems and verify some of them with experimental images. These results and simulated images of a general phase profile are used to compare the contrast and the resolution of the imaging systems. We show that, for quantitative phase imaging of a thin specimen with matched illumination, differential phase contrast offers linear transfer of specimen information to the image. We also show that the edge enhancement properties of spiral phase contrast are compromised significantly as the coherence of illumination is reduced. The results demonstrate that the phase-space imager model provides a useful framework for analysis, calibration, and design of partially coherent imaging methods.

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First evidence of phase-contrast imaging with laboratory sources and active pixel sensors

Cited by 21 publications

References 15 publications

Single-shot x-ray differential phase-contrast and diffraction imaging using two-dimensional transmission gratings

Single-shot x-ray differential phase-contrast and diffraction imaging using two-dimensional transmission gratings

Imaging of moving fiducial markers during radiotherapy using a fast, efficient active pixel sensor based EPID

Using the phase-space imager to analyze partially coherent imaging systems: bright-field, phase contrast, differential interference contrast, differential phase contrast, and spiral phase contrast

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