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Characterization of photon-counting multislit breast tomosynthesis
KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Mammorgaphy Solutions.ORCID iD: 0000-0001-9152-9089
Philips Mammography Solutions.
Philips Mammography Solutions.
Philips Research.
2018 (English)In: Medical Physics, E-ISSN 2473-4209Article in journal (Refereed) Published
Abstract [en]

Purpose: It has been shown that breast tomosynthesis may improve sensitivity and specificity compared to two-dimensional mammography, resulting in increased detection-rate of cancers or lowered call-back rates. The purpose of this study is to characterize a spectral photon-counting multislit breast tomosynthesis system that is able to do single-scan spectral imaging with multiple collimated x-ray beams. The system differs in many aspects compared to conventional tomosynthesis using energyintegrating flat-panel detectors. Methods: The investigated system was a prototype consisting of a dual-threshold photon-counting detector with 21 collimated line detectors scanning across the compressed breast. A review of the system is done in terms of detector, acquisition geometry, and reconstruction methods. Three reconstruction methods were used, simple back-projection, filtered back-projection and an iterative algebraic reconstruction technique. The image quality was evaluated by measuring the modulation transfer-function (MTF), normalized noise-power spectrum, detective quantum-efficiency (DQE), and artifact spread-function (ASF) on reconstructed spectral tomosynthesis images for a total-energy bin (defined by a low-energy threshold calibrated to remove electronic noise) and for a high-energy bin (with a threshold calibrated to split the spectrum in roughly equal parts). Acquisition was performed using a 29 kVp W/Al x-ray spectrum at a 0.24 mGy exposure. Results: The difference in MTF between the two energy bins was negligible, that is, there was no energy dependence on resolution. The MTF dropped to 50% at 1.5 lp/mm to 2.3 lp/mm in the scan direction and 2.4 lp/mm to 3.3 lp/mm in the slit direction, depending on the reconstruction method. The full width at half maximum of the ASF was found to range from 13.8 mm to 18.0 mm for the different reconstruction methods. The zero-frequency DQE of the system was found to be 0.72. The fraction of counts in the high-energy bin was measured to be 59% of the total detected spectrum. Scantimes ranged from 4 s to 16.5 s depending on voltage and current settings. Conclusions: The characterized system generates spectral tomosynthesis images with a dual-energy photon-counting detector. Measurements show a high DQE, enabling high image quality at a low dose, which is beneficial for low-dose applications such as screening. The single-scan spectral images open up for applications such as quantitative material decomposition and contrast-enhanced tomosynthesis. 

Place, publisher, year, edition, pages
John Wiley & Sons, 2018.
Keywords [en]
ASF; DQE; MTF; photon-counting; spectral imaging; tomosynthesis
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:kth:diva-228318DOI: 10.1002/mp.12684ISI: 000424809700008Scopus ID: 2-s2.0-85038253497OAI: oai:DiVA.org:kth-228318DiVA, id: diva2:1209056
Note

QC 20180522

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-05-22Bibliographically approved
In thesis
1. Spectral image quality and applications in breast tomosynthesis
Open this publication in new window or tab >>Spectral image quality and applications in breast tomosynthesis
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the 1970s, it was determined that screening mammography is an efficient tool in fighting the increasing number of women dying from breast cancer, and many countries have established screening programs since then. Mammography systems have improved substantially over the years with one of the major advances being the transition from x-ray film to digital x-ray detectors. Following this development, the number of women dying from breast cancer has decreased, but there is still much room for improvement. One technology that is changing the breast imaging landscape is breast tomosynthesis; tomographic imaging with in-plane resolution similar to that of mammography, albeit limited height resolution. Breast tomosynthesis is commonly implemented with flat-panel detectors, but line detectors in a slit-scanning geometry can also be used. The latter configuration allows for more complex detector technologies, such as spectral photon-counting detectors that enable single-shot spectral imaging. The combination of spectral imaging and tomosynthesis opens up for a range of new applications, but the slit scanning geometry, which differs substantially from that of flat-panel tomosynthesis systems, and the factors affecting image quality have not been well understood. This thesis aims at filling this gap. Image quality and the parameters that influence image quality in spectral photon-counting slit-scanning breast tomosynthesis are characterized and analyzed using cascaded-systems modelling and linear image quality metrics. In addition, the thesis goes into characterizing the x-ray properties of breast tissue, an important input parameter for accurate material decomposition of in-vivo tissue. Material decomposition with spectral imaging opens up a range of applications, such as accurate measurement of volumetric breast density and spectral lesion characterization for decision support as part of mammography screening, and contrast-enhanced K-edge imaging for diagnostics. Tomosynthesis combined with material decomposition has the potential to improve these methods further by, for instance, separating lesions or regions of interest from surrounding fibro-glandular tissue in quantitative 3D maps of breast tissue.

Abstract [sv]

På 1970-talet fann man att mammmografiscreening är en effektiv metod för att bekämpa ökningen av antalet kvinnor som dör av bröstcancer, och sedan dess har screeningprogram etablerats i en rad länder. Den tekniska utvecklingen av mammografisystem har under åren varit stor, och en av de största förändringarna var övergången från analoga till digitala röntgendetektorer. Antalet kvinnor som dör av bröstcancer har följaktligen minskat men det finns fortfarande utrymme för förbättring. En teknik som håller på att förändra marknadslandskapet för bröstavbildning idag är brösttomosyntes, d.v.s. tomografisk avbildning med en planupplösning liknande den i mammografi men med begränsad höjdupplösning. Brösttomosyntes görs vanligtvis med areadetektorer (s.k. flat-panel-detektorer) men det går också att använda linjedetektorer i en slitskannande geometri. Den senare tekniken tillåter mer avancerad detektorteknologi såsom fotonräknande detektorer som möjliggör spektralavbildning i varje exponering. Kombinationen av spektralavbildning och tomosyntes öppnar för nya tillämpningar men geometrin, som skiljer sig från den som används tillsammans med areadetektorer, och den bildkvalitet som tekniken ger upphov till har hittills varit relativt outforskade. Målet med den här avhandlingen är att fylla den luckan. Bildkvalitet och de parametrar som påverkar bildkvalitet i spektral fotonräknande och slitskannande brösttomosyntes karaktäriseras och analyseras med hjälp av kaskadmodellering och linjära bildkvalitetsmått. Avhandlingen undersöker även röntgenkaraktärisering av bröstvävnad som ger viktig information för att kunna göra materialdekomposition på vävnad in vivo. Materialdekomposition med spektral avbildning möjliggör en rad nya tillämpningar såsom noggrann mätning av volymetrisk bröstdensitet och karaktärisering av lesioner för beslutsstöd som en del av mammografiscreening, samt kontrastförstärkt K-kants avbildning för diagnostik. Tomosyntes kombinerat med spektralavbildning har potentialen att förbättra dessa tekniker ytterligare genom att separera lesioner eller områden av intresse från omkringliggande fibroglandulär vävnad i kvantitativa 3D-kartor av bröstvävnad.

Place, publisher, year, edition, pages
Stockholm: Kungliga Tekniska högskolan, 2018. p. 51
Series
TRITA-SCI-FOU ; 2018:30
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Medical Technology
Identifiers
urn:nbn:se:kth:diva-228342 (URN)978-91-7729-842-7 (ISBN)
Public defence
2018-06-15, Svedbergssalen (FD5), Roslagstullsbacken 21, Albanova Universitetscentrum, Kungl Tekniska högskolan, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2013-5816
Note

QC 20180522

Available from: 2018-05-22 Created: 2018-05-22 Last updated: 2018-05-22Bibliographically approved

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