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  • 1. Aghion, S.
    et al.
    Ahlén, O.
    Amsler, C.
    Ariga, A.
    Ariga, T.
    Belov, A. S.
    Berggren, Karl
    Physics Department, European Organisation for Nuclear Research, Switzerland.
    Bonomi, G.
    Bräunig, P.
    Bremer, J.
    Brusa, R. S.
    Cabaret, L.
    Canali, C.
    Caravita, R.
    Castelli, F.
    Cerchiari, G.
    Cialdi, S.
    Comparat, D.
    Consolati, G.
    Derking, H.
    Di Domizio, S.
    Di Noto, L.
    Doser, M.
    Dudarev, A.
    Ereditato, A.
    Ferragut, R.
    Fontana, A.
    Genova, P.
    Giammarchi, M.
    Gligorova, A.
    Gninenko, S. N.
    Haider, S.
    Huse, T.
    Jordan, E.
    Jørgensen, L. V.
    Kaltenbacher, T.
    Kawada, J.
    Kellerbauer, A.
    Kimura, M.
    Knecht, A.
    Krasnický, D.
    Lagomarsino, V.
    Lehner, S.
    Magnani, A.
    Malbrunot, C.
    Mariazzi, S.
    Matveev, V. A.
    Moia, F.
    Nebbia, G.
    Nédélec, P.
    Oberthaler, M. K.
    Pacifico, N.
    Petràček, V.
    Pistillo, C.
    Prelz, F.
    Prevedelli, M.
    Regenfus, C.
    Riccardi, C.
    Røhne, O.
    Rotondi, A.
    Sandaker, H.
    Scampoli, P.
    Storey, J.
    Vasquez, M.A. Subieta
    Špaček, M.
    Testera, G.
    Vaccarone, R.
    Widmann, E.
    Zavatarelli, S.
    Zmeskal, J.
    A moiré deflectometer for antimatter2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, article id 2538Article in journal (Refereed)
    Abstract [en]

    The precise measurement of forces is one way to obtain deep insight into the fundamental interactions present in nature. In the context of neutral antimatter, the gravitational interaction is of high interest, potentially revealing new forces that violate the weak equivalence principle. Here we report on a successful extension of a tool from atom optics—the moiré deflectometer—for a measurement of the acceleration of slow antiprotons. The setup consists of two identical transmission gratings and a spatially resolving emulsion detector for antiproton annihilations. Absolute referencing of the observed antimatter pattern with a photon pattern experiencing no deflection allows the direct inference of forces present. The concept is also straightforwardly applicable to antihydrogen measurements as pursued by the AEgIS collaboration. The combination of these very different techniques from high energy and atomic physics opens a very promising route to the direct detection of the gravitational acceleration of neutral antimatter.

  • 2. Ariga, T.
    et al.
    Aghion, S.
    Ahlén, O.
    Amsler, C.
    Ariga, A.
    Belov, A. S.
    Berggren, Karl
    European Organisation for Nuclear Research, Switzerland.
    Bonomi, G.
    Bräunig, P.
    Bremer, J.
    Brusa, R. S.
    Cabaret, L.
    Canali, C.
    Caravita, R.
    Castelli, F.
    Cerchiari, G.
    Cialdi, S.
    Comparat, D.
    Consolati, G.
    Derking, H.
    Di Domizio, S.
    Di Noto, L.
    Doser, M.
    Dudarev, A.
    Ereditato, A.
    Ferragut, R.
    Fontana, A.
    Genova, P.
    Giammarchi, M.
    Gligorova, A.
    Gninenko, S. N.
    Haider, S.
    Huse, T.
    Jordan, E.
    Jørgensen, L. V.
    Kaltenbacher, T.
    Kawada, J.
    Kellerbauer, A.
    Kimura, M.
    Knecht, A.
    Krasniký, D.
    Lagomarsino, V.
    Lehner, S.
    Magnani, A.
    Malbrunot, C.
    Mariazzi, S.
    Matveev, V. A.
    Nebbia, G.
    Nédélec, P.
    Oberthaler, M. K.
    Pacifico, N.
    Petráček, V.
    Pistillo, C.
    Prelz, F.
    Prevedelli, M.
    Regenfus, C.
    Riccardi, C.
    Røhne, O.
    Rotondi, A.
    Sandaker, H.
    Scampoli, P.
    Storet, J.
    Subieta Vasquez, M. A.
    Špaček, M.
    Testera, G.
    Widmann, E.
    Yzombard, P.
    Zavaterelli, S.
    Zmeskal, J.
    Measuring GBAR with emulsion detector2014In: International Journal of Modern Physics, Conference Series, ISSN 2010-1945, Vol. 30Article in journal (Refereed)
  • 3.
    Berggren, Karl
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Spectral image quality and applications in breast tomosynthesis2018Doctoral 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.

  • 4.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Mammography Solutions, 164 40 Kista, Sweden.
    Cederstrom, Bjorn
    Lundqvist, Mats
    Fredenberg, Erik
    Cascaded systems analysis of shift-variant image quality in slit-scanning breast tomosynthesis2018In: Medical PhysicsArticle in journal (Refereed)
  • 5.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Mammorgaphy Solutions.
    Cederström, Björn
    Philips Mammography Solutions.
    Lundqvist, Mats
    Philips Mammography Solutions.
    Fredenberg, Erik
    Philips Research.
    Characterization of photon-counting multislit breast tomosynthesis2018In: Medical Physics, E-ISSN 2473-4209Article in journal (Refereed)
    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. 

  • 6.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Mammography Solutions.
    Cederström, Björn
    Philips Mammography Solutions.
    Lundqvist, Mats
    Philips.
    Fredenberg, Erik
    Philips Research.
    Technical Note: Comparison of first‐ and second‐generation photon‐counting slit‐scanning tomosynthesis systems2018In: Medical PhysicsArticle in journal (Refereed)
    Abstract [en]

    Purpose: Digital breast tomosynthesis (DBT) is an emerging tool for breast-cancer screening and diagnostics. The purpose of this study is to present a second-generation photon-counting slitscanning DBT system and compare it to the first-generation system in terms of geometry and image quality. The study presents the first image-quality measurements on the second-generation system. Method: The geometry of the new system is based on a combined rotational and linear motion, in contrast to a purely rotational scan motion in the first generation. In addition, the calibration routines have been updated. Image quality was measured in the center of the image field in terms of in-slice modulation transfer function (MTF), artifact spread function (ASF), and in-slice detective quantum efficiency (DQE). Images were acquired using a W/Al 29 kVp spectrum at 13 mAs with 2 mm Al additional filtration and reconstructed using simple back-projection. Result: The in-slice 50% MTF was improved in the chest-mammilla direction, going from 3.2 to 3.5 lp/mm, and the zero-frequency DQE increased from 0.71 to 0.77. The MTF and ASF were otherwise found to be on par for the two systems. The new system has reduced in-slice variation of the tomographic angle. Conclusions: The new geometry is less curved, which reduces in-slice tomographic-angle variation, and increases the maximum compression height, making the system accessible for a larger population. The improvements in MTF and DQE were attributed to the updated calibration procedures. We conclude that the second-generation system maintains the key features of the photon-counting system while maintaining or improving image quality and improving the maximum compression height. 

  • 7.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Healthcare, Sweden.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Fredenberg, Erik
    Philips Healthcare, Sweden.
    Rayleigh imaging in spectral mammography2016In: MEDICAL IMAGING 2016: PHYSICS OF MEDICAL IMAGING, 2016, article id 97830AConference paper (Refereed)
    Abstract [en]

    Spectral imaging is the acquisition of multiple images of an object at different energy spectra. In mammography, dual-energy imaging (spectral imaging with two energy levels) has been investigated for several applications, in particular material decomposition, which allows for quantitative analysis of breast composition and quantitative contrast-enhanced imaging. Material decomposition with dual-energy imaging is based on the assumption that there are two dominant photon interaction effects that determine linear attenuation: the photoelectric effect and Compton scattering. This assumption limits the number of basis materials, i.e. the number of materials that are possible to differentiate between, to two. However, Rayleigh scattering may account for more than 10% of the linear attenuation in the mammography energy range. In this work, we show that a modified version of a scanning multi-slit spectral photon-counting mammography system is able to acquire three images at different spectra and can be used for triple-energy imaging. We further show that triple-energy imaging in combination with the efficient scatter rejection of the system enables measurement of Rayleigh scattering, which adds an additional energy dependency to the linear attenuation and enables material decomposition with three basis materials. Three available basis materials have the potential to improve virtually all applications of spectral imaging.

  • 8.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Eriksson, Mikael
    Hall, Per
    Wallis, Matthew
    Fredenberg, Erik
    In-vivo measurement of the effective atomic number of breast skin using spectral mammography2018In: Article in journal (Refereed)
  • 9.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Royal Inst Technol KTH, Dept Phys, Stockholm, Sweden.;Philips Mammog Solut, Kista, Sweden..
    Eriksson, Mikael
    Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden..
    Hall, Per
    Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden.;South Gen Hosp, Dept Oncol, Stockholm, Sweden..
    Walliss, Matthew G.
    Addenbrookes Hosp, Cambridge Breast Unit, Cambridge, England.;Addenbrookes Hosp, NIHR Cambridge Biomed Res Ctr, Cambridge, England..
    Fredenberg, Erik
    Philips Res, Kista, Sweden..
    In vivo measurement of the effective atomic number of breast skin using spectral mammography2018In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 63, no 21, article id 215023Article in journal (Refereed)
    Abstract [en]

    X-ray characteristics of body tissues are of crucial importance for developing and optimizing x-ray imaging techniques, in particular for dosimetry and spectral imaging applications. For breast imaging, the most important tissues are fibro-glandular, adipose and skin tissue. Some work has and is being done to better characterize these tissue types, in particular fibro-glandular and adipose tissue. In the case of breast skin, several recent studies have been published on the average skin thickness, but with regards to x-ray attenuation, the only published data, to the knowledge of the authors, is the elemental composition analysis of Hammerstein et al (1979 Radiology 130 485-91). This work presents an overview of breast skin thickness studies and a measurement of the effective atomic number (Z(eff)) of breast skin using spectral mammography. Z(eff), which together with the density forms the attenuation, is used to validate the work by Hammerstein et al, and the dependence of clinical parameters on Z(eff) is explored. Measurements were conducted on the skin edge of spectral mammograms using clinical data from a screening population (n = 709). The weighted average of breast skin thickness reported in studies between 1997 and 2013 was found to be 1.56 +/- 0.28 mm. Mean Z(eff) was found to be 7.365 (95% CI: 7.364,7.366) for normal breast skin and 7.441 (95% CI: 7.440,7.442) for the nipple and areola. Z(eff) of normal breast skin is in agreement with Hammerstein et al, despite the different methods and larger sample size used. A small but significant increase in Z(eff) was found with age, but the increase is too small to be relevant for most applications. We conclude that normal breast skin is well described by a 1.56 mm skin layer and the elemental composition presented by Hammerstein et al (1979 Radiology 130 485-91) and recommend using these characteristics when modelling breast skin.

  • 10.
    Berggren, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Healthcare, S-17141 Solna, Sweden.
    Lundqvist, Mats
    Cederstrom, Bjorn
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Fredenberg, Erik
    Physical characterization of photon-counting tomosynthesis2015Conference paper (Refereed)
    Abstract [en]

    Tomosynthesis is emerging as a next generation technology in mammography. Combined with photon-counting detectors with the ability for energy discrimination, a novel modality is enabled - spectral tomosynthesis. Further advantages of photon-counting detectors in the context of tomosynthesis include elimination of electronic noise, efficient scatter rejection (in some geometries) and no lag. Fourier-based linear-systems analysis is a well-established method for optimizing image quality in two-dimensional x-ray systems. The method has been successfully adapted to three-dimensional imaging, including tomosynthesis, but several areas need further investigation. This study focuses on two such areas: 1) Adaption of the methodology to photon-counting detectors, and 2) violation of the shift-invariance and stationarity assumptions in non-cylindrical geometries. We have developed a Fourier-based framework to study the image quality in a photon-counting tomosynthesis system, assuming locally linear, stationary, and shift-invariant system response. The framework includes a cascaded-systems model to propagate the modulation-transfer function (MTF) and noise-power spectrum (NPS) through the system. The model was validated by measurements of the MTF and NPS. High degrees of non-shift invariance and non-stationarity were observed, in particular for the depth resolution as the angle of incidence relative the reconstruction plane varied throughout the imaging volume. The largest effects on image quality in a given point in space were caused by interpolation from the inherent coordinate system of the x-rays to the coordinate system that was used for reconstruction. This study is part of our efforts to fully characterize the spectral tomosynthesis system, we intend to extend the model further to include the detective-quantum efficiency, observer modelling, and spectral effects.

  • 11. Cederström, B.
    et al.
    Fredenberg, E.
    Berggren, Karl
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Mammography Solutions, Philips, Sweden.
    Erhard, K.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Wallis, M.
    Lesion characterization in spectral photon-counting tomosynthesis2017In: Medical Imaging 2017: Physics of Medical Imaging, SPIE - International Society for Optical Engineering, 2017, Vol. 10132, article id 1013205Conference paper (Refereed)
    Abstract [en]

    It has previously been shown that 2D spectral mammography can be used to discriminate between (likely benign) cystic and (potentially malignant) solid lesions in order to reduce unnecessary recalls in mammography. One limitation of the technique is, however, that the composition of overlapping tissue needs to be interpolated from a region surrounding the lesion. The purpose of this investigation was to demonstrate that lesion characterization can be done with spectral tomosynthesis, and to investigate whether the 3D information available in tomosynthesis can reduce the uncertainty from the interpolation of surrounding tissue. A phantom experiment was designed to simulate a cyst and a tumor, where the tumor was overlaid with a structure that made it mimic a cyst. In 2D, the two targets appeared similar in composition, whereas spectral tomosynthesis revealed the exact compositional difference. However, the loss of discrimination signal due to spread from the plane of interest was of the same strength as the reduction of anatomical noise. Results from a preliminary investigation on clinical tomosynthesis images of solid lesions yielded results that were consistent with the phantom experiments, but were still to some extent inconclusive. We conclude that lesion characterization is feasible in spectral tomosynthesis, but more data, as well as refinement of the calibration and discrimination algorithms, are needed to draw final conclusions about the benefit compared to 2D.

  • 12. Fredenberg, Erik
    et al.
    Berggren, Karl
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Health Systems, Sweden.
    Bartels, Matthias
    Erhard, Klaus
    Volumetric Breast-Density Measurement Using Spectral Photon-Counting Tomosynthesis: First Clinical Results2016In: Breast Imaging, IWDM 2016, Springer, 2016, p. 576-584Conference paper (Refereed)
    Abstract [en]

    Measurements of breast density have the potential to improve the efficiency and reduce the cost of screening mammography through personalized screening. Breast density has traditionally been evaluated from the dense area in a mammogram, but volumetric assessment methods, which measure the volumetric fraction of fibro-glandular tissue in the breast, are potentially more consistent and physically sound. The purpose of the present study is to evaluate a method for measuring the volumetric breast density using photon-counting spectral tomo-synthesis. The performance of the method was evaluated using phantom measurements and clinical data from a small population (n = 18). The precision was determined to be 2.4 percentage points (pp) of volumetric breast density. Strong correlations were observed between contralateral (R-2 = 0.95) and ipsilateral (R-2 = 0.96) breast-density measurements. The measured breast density was anti-correlated to breast thickness, as expected, and exhibited a skewed distribution in the range [3.7 %, 55 %] and with a median of 18 %. We conclude that the method yields promising results that are consistent with expectations. The relatively high precision of the method may enable novel applications such as treatment monitoring.

  • 13. Fredenberg, Erik
    et al.
    Erhard, Klaus
    Berggren, Karl
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging. Philips Healthcare, S-17141 Solna, Sweden.
    Dance, David R.
    Young, Kenneth C.
    Cederstrom, Bjorn
    Johansson, Henrik
    Lundqvist, Mats
    Moa, Elin
    Homan, Hanno
    Willsher, Paula
    Kilburn-Toppin, Fleur
    Wallis, Matthew
    X-ray attenuation of adipose breast tissue: In-vitro and in-vivo measurements using spectral imaging2015In: MEDICAL IMAGING 2015: PHYSICS OF MEDICAL IMAGING, 2015, Vol. 9412, article id 94121UConference paper (Refereed)
    Abstract [en]

    The development of new x-ray imaging techniques often requires prior knowledge of tissue attenuation, but the sources of such information are sparse. We have measured the attenuation of adipose breast tissue using spectral imaging, in vitro and in vivo. For the in-vitro measurement, fixed samples of adipose breast tissue were imaged on a spectral mammography system, and the energy-dependent x-ray attenuation was measured in terms of equivalent thicknesses of aluminum and poly-methyl methacrylate (PMMA). For the in-vivo measurement, a similar procedure was applied on a number of spectral screening mammograms. The results of the two measurements agreed well and were consistent with published attenuation data and with measurements on tissue-equivalent material.

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