| 1. |
- Cahn, R N, et al.
(författare)
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Detective quantum efficiency dependence on x-ray energy weighting in mammography
- 1999
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Ingår i: Medical physics. - Medical physics : Wiley. - 0094-2405. ; 26:12, s. 2680-2683
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Tidskriftsartikel (refereegranskat)abstract
- An evaluation of the dependence of detective quantum efficiency (DQE) on the incident energy spectrum has been made for mammography. The DQE dependence on the energy spectrum has been evaluated for energy-integrating detectors, photon-counting detectors, and detectors that measure the energy of each photon. To isolate the effect of the x-ray energy spectrum the detector has been assumed to be ideal, i.e., all noise sources are assumed to be zero except for quantum fluctuations. The result shows that the improvement in DQE, if the energy-integrating detector is compared to a single-photon counting detector, is of the order of 10%. Comparing the energy-integrating detector and the detector measuring the energy for each photon the improvement is around 30% using a molybdenumanodespectrum typical in mammography. It is shown that the optimal weight factors to combine the data in the case the energy is measured are very well approximated if the weight factors are proportional to E−3." style="position: relative;" tabindex="0" id="MathJax-Element-1-Frame" class="MathJax">E−3. Another conclusion is that in calculating the DQE, a detector should be compared to one that uses ideal energy weighting for each photon since this provides the best signal-to-noise ratio. This has generally been neglected in the literature.
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| 2. |
- Cederström, B., et al.
(författare)
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Lesion characterization in spectral photon-counting tomosynthesis
- 2017
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Ingår i: Medical Imaging 2017. - : SPIE - International Society for Optical Engineering. - 9781510607095
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Konferensbidrag (refereegranskat)abstract
- It has previously been shown that 2D spectral mammography can be used to discriminate between (likely benign) cystic and (potentially malignant) solid lesions in order to reduce unnecessary recalls in mammography. One limitation of the technique is, however, that the composition of overlapping tissue needs to be interpolated from a region surrounding the lesion. The purpose of this investigation was to demonstrate that lesion characterization can be done with spectral tomosynthesis, and to investigate whether the 3D information available in tomosynthesis can reduce the uncertainty from the interpolation of surrounding tissue. A phantom experiment was designed to simulate a cyst and a tumor, where the tumor was overlaid with a structure that made it mimic a cyst. In 2D, the two targets appeared similar in composition, whereas spectral tomosynthesis revealed the exact compositional difference. However, the loss of discrimination signal due to spread from the plane of interest was of the same strength as the reduction of anatomical noise. Results from a preliminary investigation on clinical tomosynthesis images of solid lesions yielded results that were consistent with the phantom experiments, but were still to some extent inconclusive. We conclude that lesion characterization is feasible in spectral tomosynthesis, but more data, as well as refinement of the calibration and discrimination algorithms, are needed to draw final conclusions about the benefit compared to 2D.
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| 3. |
- Cederström, B, et al.
(författare)
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Multi-prism x-ray lens
- 2002
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Ingår i: Appl Phys Lett. ; 81:8, s. 1399-1401
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Tidskriftsartikel (refereegranskat)
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| 4. |
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| 5. |
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| 6. |
- Lundqvist, M., et al.
(författare)
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Evaluation of a photon-counting X-ray imaging system
- 2001
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 48:4, s. 1530-1536
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Tidskriftsartikel (refereegranskat)abstract
- A digital imaging system has been developed for mammography using silicon strip detectors operated in a pulse-counting mode and configured in a scanned slit geometry. More than 90% of the photons are absorbed in the sensor. The scatter rejection is very efficient and the image formation is nearly optimal since each X ray is processed individually. The result is a very dose-efficient system. In this paper, we present measurements that verify that the performance of the readout electronics is sufficient to count photons at high rates with high quantum efficiency and a charge collection efficiency that does not limit the dose efficiency. The spatial resolution of the system was measured to provide a modulation transfer function of approximately 0.5 at a spatial frequency of 10 lp/mm. Images of a mammography phantom were recorded experimentally to test overall system performance.
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| 7. |
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| 8. |
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| 9. |
- Shastri, S D, et al.
(författare)
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High-energy X-ray optics with silicon saw-tooth refractive lenses
- 2007
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495 .- 1600-5775. ; 14:part 2, s. 204-211
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Tidskriftsartikel (refereegranskat)abstract
- Silicon saw-tooth refractive lenses have been in successful use for vertical focusing and collimation of high-energy X-rays (50-100 keV) at the 1-ID undulator beamline of the Advanced Photon Source. In addition to presenting an effectively parabolic thickness profile, as required for aberration-free refractive optics, these devices allow high transmission and continuous tunability in photon energy and focal length. Furthermore, the use of a single-crystal material (i.e. Si) minimizes small-angle scattering background. The focusing performance of such saw-tooth lenses, used in conjunction with the 1-ID beamline's bent double-Laue monochromator, is presented for both short (1:0.02) and long (1:0.6) focal-length geometries, giving line-foci in the 2 µm-25 µm width range with 81 keV X-rays. In addition, a compound focusing scheme was tested whereby the radiation intercepted by a distant short-focal-length lens is increased by having it receive a collimated beam from a nearer (upstream) lens. The collimation capabilities of Si saw-tooth lenses are also exploited to deliver enhanced throughput of a subsequently placed small-angular-acceptance high-energy-resolution post-monochromator in the 50-80 keV range. The successful use of such lenses in all these configurations establishes an important detail, that the pre-monochromator, despite being comprised of vertically reflecting bent Laue geometry crystals, can be brilliance-preserving to a very high degree.
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