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Contrast-enhanced spectral mammography with a photon-counting detector
KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging. (Medical Imaging)
KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging. (Medical Imaging)
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2010 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 37, no 5, 2017-2029 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: Spectral imaging is a method in medical x-ray imaging to extract information about the object constituents by the material-specific energy dependence of x-ray attenuation. In particular, the detectability of a contrast agent can be improved over a lumpy background. We have investigated a photon-counting spectral imaging system with two energy bins for contrast-enhanced mammography. System optimization and the potential benefit compared to conventional non-energy-resolved imaging was studied.

Methods: A framework for system characterization was set up that included quantum and anatomical noise, and a theoretical model of the system was benchmarked to phantom measurements.

Results: It was found that optimal combination of the energy-resolved images corresponded approximately to minimization of the anatomical noise, and an ideal-observer detectability index could be improved more than a factor of two compared to absorption imaging in the phantom study. In the clinical case, an improvement close to 80% was predicted for an average glandularity breast, and a factor of eight for dense breast tissue. Another 70% was found to be within reach for an optimized system.

Conclusions: Contrast-enhanced spectral mammography is feasible and beneficial with the current system, and there is room for additional improvements.

Place, publisher, year, edition, pages
2010. Vol. 37, no 5, 2017-2029 p.
Keyword [en]
spectral imaging, mammography, contrast agent, photon counting, dual-energy subtraction, energy weighting, anatomical noise
National Category
Other Engineering and Technologies not elsewhere specified Computer Vision and Robotics (Autonomous Systems) Radiology, Nuclear Medicine and Medical Imaging Medical Laboratory and Measurements Technologies
URN: urn:nbn:se:kth:diva-11637DOI: 10.1118/1.3371689ISI: 000277242800009ScopusID: 2-s2.0-77952404690OAI: diva2:278575
EU, European Research Council, LSHCCT2007-037642
QC 20100714 ändrad från submitted till published 20110103Available from: 2009-11-27 Created: 2009-11-27 Last updated: 2011-01-03Bibliographically approved
In thesis
1. Spectral Mammography with X-Ray Optics and a Photon-Counting Detector
Open this publication in new window or tab >>Spectral Mammography with X-Ray Optics and a Photon-Counting Detector
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Early detection is vital to successfully treating breast cancer, and mammography screening is the most efficient and wide-spread method to reach this goal. Imaging low-contrast targets, while minimizing the radiation exposure to a large population is, however, a major challenge. Optimizing the image quality per unit radiation dose is therefore essential. In this thesis, two optimization schemes with respect to x-ray photon energy have been investigated: filtering the incident spectrum with refractive x-ray optics (spectral shaping), and utilizing the transmitted spectrum with energy-resolved photon-counting detectors (spectral imaging).

Two types of x-ray lenses were experimentally characterized, and modeled using ray tracing, field propagation, and geometrical optics. Spectral shaping reduced dose approximately 20% compared to an absorption-filtered reference system with the same signal-to-noise ratio, scan time, and spatial resolution. In addition, a focusing pre-object collimator based on the same type of optics reduced divergence of the radiation and improved photon economy by about 50%.

A photon-counting silicon detector was investigated in terms of energy resolution and its feasibility for spectral imaging. Contrast-enhanced tumor imaging with a system based on the detector was characterized and optimized with a model that took anatomical noise into account. Improvement in an ideal-observer detectability index by a factor of 2 to 8 over that obtained by conventional absorption imaging was found for different levels of anatomical noise and breast density. Increased conspicuity was confirmed by experiment. Further, the model was extended to include imaging of unenhanced lesions. Detectability of microcalcifications increased no more than a few percent, whereas the ability to detect large tumors might improve on the order of 50% despite the low attenuation difference between glandular and cancerous tissue. It is clear that inclusion of anatomical noise and imaging task in spectral optimization may yield completely different results than an analysis based solely on quantum noise.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. x, 56 p.
Trita-FYS, ISSN 0280-316X ; 2009:69
mammography; x-ray optics; photon counting; spectral shaping; spectral imaging; collimation; radiation dose; signal-to-noise ratio; quantum noise; anatomical noise; spatial resolution; x-ray flux;
National Category
Engineering and Technology Other Engineering and Technologies Atom and Molecular Physics and Optics Other Engineering and Technologies not elsewhere specified Electrical Engineering, Electronic Engineering, Information Engineering Medical Laboratory and Measurements Technologies Radiology, Nuclear Medicine and Medical Imaging
urn:nbn:se:kth:diva-11641 (URN)978-91-7415-516-7 (ISBN)
Public defence
2009-12-18, Kollegiesalen, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
QC 20100714Available from: 2009-12-04 Created: 2009-11-27 Last updated: 2010-07-15Bibliographically approved

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