Characterization and Optimization of Silicon-strip Detectors for Mammography and Computed Tomography
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
The goal in medical x-ray imaging is to obtain the image quality requiredfor a given detection task, while ensuring that the patient dose is kept as lowas reasonably achievable. The two most common strategies for dose reductionare: optimizing incident x-ray beams and utilizing energy informationof transmitted beams with new detector techniques (spectral imaging). Inthis thesis, dose optimization schemes were investigated in two x-ray imagingsystems: digital mammography and computed tomography (CT).
In digital mammography, the usefulness of anti-scatter grids was investigatedas a function of breast thickness with varying geometries and experimentalconditions. The general conclusion is that keeping the grid is optimalfor breasts thicker than 5 cm, whereas the dose can be reduced without a gridfor thinner breasts.
A photon-counting silicon-strip detector developed for spectral mammographywas characterized using synchrotron radiation. Energy resolution, ΔE/Ein, was measured to vary between 0.11-0.23 in the energy range 15-40 keV, which is better than the energy resolution of 0.12-0.35 measured inthe state-of-the-art photon-counting mammography system. Pulse pileup hasshown little effect on energy resolution.
In CT, the performance of a segmented silicon-strip detector developedfor spectral CT was evaluated and a theoretical comparison was made withthe state-of-the-art CT detector for some clinically relevant imaging tasks.The results indicate that the proposed photon-counting silicon CT detector issuperior to the state-of-the-art CT detector, especially for high-contrast andhigh-resolution imaging tasks.
The beam quality was optimized for the proposed photon-counting spectralCT detector in two head imaging cases: non-enhanced imaging and Kedgeimaging. For non-enhanced imaging, a 120-kVp spectrum filtered by 2half value layer (HVL) copper (Z = 29) provides the best performance. Wheniodine is used in K-edge imaging, the optimal filter is 2 HVL iodine (Z = 53)and the optimal kVps are 60-75 kVp. In the case of gadolinium imaging, theradiation dose can be minimized at 120 kVp filtered by 2 HVL thulium (Z =69).
Place, publisher, year, edition, pages
STOCKHOLM: KTH Royal Institute of Technology, 2016. , viii, 73 p.
TRITA-FYS, ISSN 0280-316X ; 0280-316X
mammography, anti-scatter grid, photon-counting, spectral computed tomography, silicon strip, ASIC, energy resolution, Compton scatter, material decomposition, K-edge imaging
Research subject Medical Technology
IdentifiersURN: urn:nbn:se:kth:diva-184092ISBN: 978-91-7595-919-1OAI: oai:DiVA.org:kth-184092DiVA: diva2:914033
2016-04-22, FA 31, ROSLAGSTULLSBACKEN 21, KTH, STOCKHOLM, 09:00 (English)
Maidment, Andrew, Professor
Danielsson, Mats, Professorxu, cheng, Doctor
QC 201604012016-04-012016-03-232016-04-01Bibliographically approved
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