Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Optimization Of Beam Quality For Photon-Counting Spectral Computed Tomography In Head Imaging: Simulation Study
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. (Physics of Medical imaging)ORCID iD: 0000-0001-8560-3262
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.ORCID iD: 0000-0002-5092-8822
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.ORCID iD: 0000-0002-3039-9791
2015 (English)In: Journal of Medical Imaging, ISSN 2329-4302, E-ISSN 2329-4310, Vol. 2, no 4, 043504-1-043504-16 p., 043504Article in journal (Refereed) Published
Abstract [en]

Head computed tomography (CT) plays an important role in the comprehensive evaluation of acutestroke. Photon-counting spectral detectors, as promising candidates for use in the next generation of x-ray CTsystems, allow for assigning more weight to low-energy x-rays that generally contain more contrast information.Most importantly, the spectral information can be utilized to decompose the original set of energy-selectiveimages into several basis function images that are inherently free of beam-hardening artifacts, a potential ad-vantage for further improving the diagnosis accuracy. We are developing a photon-counting spectral detector forCT applications. The purpose of this work is to determine the optimal beam quality for material decomposition intwo head imaging cases: nonenhanced imaging and K-edge imaging. A cylindrical brain tissue of 16-cm diam-eter, coated by a 6-mm-thick bone layer and 2-mm-thick skin layer, was used as a head phantom. The imagingtarget was a 5-mm-thick blood vessel centered in the head phantom. In K-edge imaging, two contrast agents,iodine and gadolinium, with the same concentration (5mg∕mL) were studied. Three parameters that affect beamquality were evaluated: kVp settings (50 to 130 kVp), filter materials (Z¼13to 83), and filter thicknesses [0 to 2half-value layer (HVL)]. The image qualities resulting from the varying x-ray beams were compared in terms oftwo figures of merit (FOMs): squared signal-difference-to-noise ratio normalized by brain dose (SDNR2∕BD) andthat normalized by skin dose (SDNR2∕SD). For nonenhanced imaging, the results show that the use of the 120-kVp spectrum filtered by 2 HVL copper (Z¼29) provides the best performance in both FOMs. When iodine isused in K-edge imaging, the optimal filter is 2 HVL iodine (Z¼53) and the optimal kVps are 60 kVp in terms ofSDNR2∕BD and 75 kVp in terms of SDNR2∕SD. A tradeoff of 65 kVp was proposed to lower the potential riskof skin injuries if a relatively long exposure time is necessarily performed in the iodinated imaging. In the case ofgadolinium imaging, both SD and BD can be minimized at 120 kVp filtered with 2 HVL thulium (Z¼69). Theresults also indicate that with the same concentration and their respective optimal spectrum, the values ofSDNR2∕BD and SDNR2∕SD in gadolinium imaging are, respectively, around 3 and 10 times larger thanthose in iodine imaging. However, since gadolinium is used in much lower concentrations than iodine in theclinic, iodine may be a preferable candidate for K-edge imaging.

Place, publisher, year, edition, pages
SPIE , 2015. Vol. 2, no 4, 043504-1-043504-16 p., 043504
Keyword [en]
photon counting, spectral computed tomography, material decomposition, K-edge imaging
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:kth:diva-184602DOI: 10.1117/1.JMI.2.4.043504ISI: 000374235100015OAI: oai:DiVA.org:kth-184602DiVA: diva2:916323
Note

QC 20160401

Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2017-11-30Bibliographically approved
In thesis
1. Characterization and Optimization of Silicon-strip Detectors for Mammography and Computed Tomography
Open this publication in new window or tab >>Characterization and Optimization of Silicon-strip Detectors for Mammography and Computed Tomography
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.
Series
TRITA-FYS, ISSN 0280-316X ; 0280-316X
Keyword
mammography, anti-scatter grid, photon-counting, spectral computed tomography, silicon strip, ASIC, energy resolution, Compton scatter, material decomposition, K-edge imaging
National Category
Medical Engineering
Research subject
Medical Technology
Identifiers
urn:nbn:se:kth:diva-184092 (URN)978-91-7595-919-1 (ISBN)
Public defence
2016-04-22, FA 31, ROSLAGSTULLSBACKEN 21, KTH, STOCKHOLM, 09:00 (English)
Opponent
Supervisors
Note

QC 20160401

Available from: 2016-04-01 Created: 2016-03-23 Last updated: 2016-04-01Bibliographically approved

Open Access in DiVA

fulltext(3373 kB)53 downloads
File information
File name FULLTEXT01.pdfFile size 3373 kBChecksum SHA-512
06a50b297e5c82023a44f7e532fd9de82bc2159ff9d89a7ca75f643160d74f2ff2e50816988ed7189089c006a1d2918138d6d005a14adddf2c6bd0c05f0860d1
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Chen, HanXu, ChengPersson, MatsDanielsson, Mats
By organisation
Physics of Medical Imaging
In the same journal
Journal of Medical Imaging
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 53 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 42 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf