Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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
Digital Mammography with a Photon Counting Detector in a Scanned Multislit Geometry
KTH, School of Engineering Sciences (SCI), Physics.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Mammography screening aims to reduce the number of breast cancer deaths by early detection of the disease, which is one of the leading causes of deaths for middle aged women in the western world. The risk from the x-ray radiation in mammography is relatively low but still a factor in the benefit-risk ratio of screening. The characterization and optimization of a digital mammography system is presented in this thesis. The investigated system is shown to be highly dose efficient by employing a photon counting detector in a scanning multislit geometry.

A novel automatic exposure control (AEC) is proposed and validated in clinical practise. The AEC uses the leading detector edge to measure the transmission of the breast. The exposure is modulated by altering the scan velocity during the scan. A W-Al anode-filter combination is proposed.

The characterization of the photon counting detector is performed using the detective quantum efficiency. The effect of the photon counting detector and the multislit geometry on the measurement method is studied in detail. It is shown that the detector has a zero-frequency DQE of over 70\% and that it is quantum limited even at very low exposures.

Efficient rejection of image-degrading secondary radiation is fundamental for a dose efficient system. The efficiency of the scatter rejection techniques currently used are quantified and compared to the multislit geometry.

A system performance metric with its foundation in statistical decision theory is discussed. It is argued that a photon counting multislit system can operate at approximately half the dose compared to several other digital mammography techniques.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , viii, 41 p.
Series
Trita-FYS, ISSN 0280-316X ; 2007:28
Keyword [en]
mammography, digital, photon counting, scanning, detective quantum effciency, scattered radiation, automatic exposure control
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-4322ISBN: 978-91-7178-622-7 (print)OAI: oai:DiVA.org:kth-4322DiVA: diva2:11798
Public defence
2007-04-20, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100825Available from: 2007-03-30 Created: 2007-03-30 Last updated: 2010-08-25Bibliographically approved
List of papers
1. AEC for scanning digital mammography based on variation of scan velocity
Open this publication in new window or tab >>AEC for scanning digital mammography based on variation of scan velocity
2005 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 32, no 11, 3367-3374 p.Article in journal (Refereed) Published
Abstract [en]

A theoretical evaluation of nonuniform x-ray field distributions in mammography was conducted. An automatic exposure control (AEC) is proposed for a scanning full field digital mammography system. It uses information from the leading part of the detector to vary the scan velocity dynamically, thus creating a nonuniform x-ray field in the scan direction. Nonuniform radiation fields were also created by numerically optimizing the scan velocity profile to each breast's transmission distribution, with constraints on velocity and acceleration. The goal of the proposed AEC is to produce constant pixel signal-to-noise ratio throughout the image. The target pixel SNR for each image could be set based on the breast thickness, breast composition, and the beam quality as to achieve the same contrast-to-noise ratio between images for structures of interest. The results are quantified in terms of reduction in entrance surface air kerma (ESAK) and scan time relative to a uniform x-ray field. The theoretical evaluation was performed on a set of 266 mammograms. The performance of the different methods to create nonuniform fields decreased with increased detector width, from 18% to 11% in terms of ESAK reduction and from 30% to 25% in terms of scan time reduction for the proposed AEC and detector widths from 10 to 60 mm. Some correlation was found between compressed breast thickness and the projected breast area onto the image field. This translated into an increase of the ESAK and decrease of the scan time reduction with breast thickness. Ideally a nonuniform field in two dimensions could reduce the entrance dose by 39% on average, whereas a field nonuniform in only the scanning dimension ideally yields a 20% reduction. A benefit with the proposed AEC is that the risk of underexposing the densest region of the breast can be virtually eliminated.

Keyword
mammography; exposure control; scanning; slit; slot ; SCREEN-FILM MAMMOGRAPHY; REGIONAL EXPOSURE CONTROL; IMAGE QUALITY; FILTER COMBINATIONS; CHEST RADIOGRAPHY; MONTE-CARLO; SYSTEM; ANODE; CONTRAST; OPTIMIZATION
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6938 (URN)10.1118/1.2089487 (DOI)000233385800018 ()2-s2.0-28044435613 (Scopus ID)
Note
QC 20100825Available from: 2007-03-30 Created: 2007-03-30 Last updated: 2017-12-14Bibliographically approved
2. Scatter rejection in multislit digital mammography
Open this publication in new window or tab >>Scatter rejection in multislit digital mammography
2006 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 33, no 4, 933-940 p.Article in journal (Refereed) Published
Abstract [en]

The scatter to primary ratio (SPR) was measured on a scanning multislit full-field digital mammography system for different thickness of breast equivalent material and different tube voltages. Scatter within the detector was measured separately and was found to be the major source of scatter in the assembly. Measured total SPRs below 6% are reported for breast range 3-7 cm. The performance of the multislit assembly is compared to other imaging geometries with different scatter rejection schemes by using the scatter detective quantum efficiency.

Keyword
mammography, scatter, scanning, slit, slot, reduction, radiography, radiation, contrast, grids, scatter/primary, performance, removal, energy
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-15637 (URN)10.1118/1.2179122 (DOI)000237038300015 ()2-s2.0-33645525594 (Scopus ID)
Note
QC 20100825Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Spectral shaping for photon counting digital mammography
Open this publication in new window or tab >>Spectral shaping for photon counting digital mammography
2007 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 580, no 2, 1046-1049 p.Article in journal (Refereed) Published
Abstract [en]

The spectral shaping properties of conventional filters have been evaluated for a photon counting digital mammography system, and the result has been compared with the theoretical spectrum from a multi-prism X-ray lens (MPL). The absorption filters and the MPL were evaluated using a theoretical model of the system which has been verified experimentally. The spectral shaping performance is quantified with the spectral quantum efficiency (SQE), calculated as the polychromatic signal-difference-to-noise ratio (SDNR) squared over the optimal monochromatic SDNR squared at the same average glandular dose. The MPL increases the SQE by 25% compared to the investigated absorption filter when compared with a Tungsten anode. This translates into a potential dose reduction of 20% at maintained SDNR.

Keyword
mammography; photon counting; spectrum; filter; X-ray optics; multi-prism lens
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6940 (URN)10.1016/j.nima.2007.06.087 (DOI)000250128000046 ()2-s2.0-34548514027 (Scopus ID)
Note
QC 20100825. Uppdaterad från Accepted till Published 20100825. Konferens: 3rd International Conference on Imaging Techniques in Subatomic Physics, Astrophysics, Medicine, Biology and Industry, Stockholm, SWEDEN, JUN 27-30, 2006.Available from: 2007-03-30 Created: 2007-03-30 Last updated: 2017-12-14Bibliographically approved
4. Physical characterization of a scanning photon counting digital mammography system based on Si-strip detectors
Open this publication in new window or tab >>Physical characterization of a scanning photon counting digital mammography system based on Si-strip detectors
2007 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 34, no 6, 1918-1925 p.Article in journal (Refereed) Published
Abstract [en]

The physical performance of a scanning multislit full field digital mammography system was determined using basic image quality parameters. The system employs a direct detection detector comprised of linear silicon strip sensors in an edge-on geometry connected to photon counting electronics. The pixel size is 50 mu m and the field of view 24 x 26 cm(2). The performance was quantified using the presampled modulation transfer function, the normalized noise power spectrum and the detective quantum efficiency (DQE). Compared to conventional DQE methods, the scanning geometry with its intrinsic scatter rejection poses additional requirements on the measurement setup, which are investigated in this work. The DQE of the photon counting system was found to be independent of the dose level to the detector in the 7.6-206 mu Gy range. The peak DQE was 72% and 73% in the scan and slit direction, respectively, measured with a 28 kV W-0.5 mm Al anodefilter combination with an added 2 mm Al filtration.

Keyword
mammography; detective quantum efficiency; scanning; MODULATION TRANSFER-FUNCTION; IMAGE QUALITY CHARACTERIZATION; QUANTUM EFFICIENCY; PERFORMANCE; ENERGY
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6941 (URN)10.1118/1.2731032 (DOI)000247479600008 ()2-s2.0-34447303835 (Scopus ID)
Note
QC 20100825. Uppdaterad från Accepted till Published 20100825.Available from: 2007-03-30 Created: 2007-03-30 Last updated: 2017-12-14Bibliographically approved
5. Evaluation of an AEC system for scanning photon counting mammography based on variation of scan velocity
Open this publication in new window or tab >>Evaluation of an AEC system for scanning photon counting mammography based on variation of scan velocity
(English)In: Medical physics (Lancaster), ISSN 0094-2405Article in journal (Other academic) Submitted
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6942 (URN)
Note
QS 20120328Available from: 2007-03-30 Created: 2007-03-30 Last updated: 2017-12-14Bibliographically approved

Open Access in DiVA

fulltext(593 kB)2485 downloads
File information
File name FULLTEXT01.pdfFile size 593 kBChecksum MD5
5589a1922e34571156228cadd8657b0dd1bcd2e80f722a57a602e0702fc22ab027eea92b
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Åslund, Magnus
By organisation
Physics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 2485 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

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 653 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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