1,721,061 research outputs found
Artificial Intelligence and tomosynthesis for breast cancer detection
Full text linkContains fulltext :
201151.pdf (Publisher’s version ) (Open Access)Radboud University, 26 maart 2019Promotor : Karssemeijer, N. Co-promotores : Sechopoulos, I., Mann, R.M
Functional CT imaging of the lung: Subtraction CT as a novel technique
No full textContains fulltext :
212659.pdf (Publisher’s version ) (Open Access)Radboud University, 16 december 2019Promotor : Prokop, Mathias Co-promotores : Brink, M., Sechopoulos, I
Objective image quality assessment in X-ray breast imaging
No full textContains fulltext :
212645.pdf (Publisher’s version ) (Open Access)Radboud University, 12 december 2019Promotor : Karssemeijer, N. Co-promotores : Broeders, M.J.M., Veldkamp, W.J.H., Sechopoulos, I
Detection and minimally invasive treatment of small breast cancers
Full text linkContains fulltext :
236661.pdf (Publisher’s version ) (Open Access)Radboud University, 06 oktober 2021Promotor : Sechopoulos, I. Co-promotores : Mann, R.M., Strobbe, L., Bult, P.216 p
Mammography dose estimates do not reflect any specific patient's breast dose
No full textIt is with great interest that we read the article by Gennaro et al published recently in this journal [ 1
]. It is clear that the introduction of the European Directive 2013/59/Euratom transposition has brought forth a need to evaluate the appropriateness and real meaning of many of the dosimetry estimates used every day in our field. It is therefore of great value that work such as this one is done, in which we can actually gauge the level of accuracy that we can expect from common dose estimates. This is especially true for the values provided by the imaging systems themselves, that tend to form part of the official record, in the form of specific DICOM tags in image headers and/or in Radiation Dose Structured Reports (RDSRs). As demonstrated by the authors, it is encouraging that “the best accuracy” metric “that can be calculated” shows that the system-calculated organ dose has an overall mean relative difference of only 8.7%, making this automated calculated metric suitable for most of the purposes listed in the European Directive
Noise and spatial resolution characteristics of a clinical computed tomography scanner dedicated to the breast
No full textThis work aims at evaluating the spatial resolution and noise in 3D images acquired with a clinical Computed Tomography scanner dedicated to the breast (BCT). The presampled modulation transfer function (MTF) and the noise power spectrum (NPS) are measured. In addition, the capability of the system in showing simulated lesions and microcalcification clusters was assessed via a phantom test. The impact of the selected reconstruction algorithm on MTF, NPS, and simulated lesion visibility was evaluated. The available algorithms are the Standard (Std) and Calcification (Calc) reconstructions, which use an isotropic reconstructed voxel edge of 0.273 mm and the high-resolution (HR) reconstruction algorithm that uses an isotropic reconstructed voxel edge of 0.190 mm. The spatial frequency (expressed in mm-1 ) at which the MTF curve goes down to 10% (MTF10%) was found to be 1.0 mm-1 for the case of Std reconstruction in radial direction at the chest-wall; this value increases to 1.3 mm-1 and 1.5 mm-1 for the HR and Calc reconstructions, respectively. The distance from the isocenter did not impact the system spatial resolution. As expected, the improvement in the spatial resolution in the Calc and HR reconstruction algorithms is accompanied by an increase in the noise, especially at the higher frequencies, as shown in the 1D NPS. A phantom study showed that both simulated soft lesion with diameter of 1.8 mm and microcalcification cluster with grain diameter of 0.29 mm are visible, no matter what reconstruction algorithm is selected. Microcalcifications with diameter of 0.20 mm and 0.13 mm do not appear to be visible
Empirical detector model for simulated breast exams with a dedicated breast CT scanner
No full textThis work proposes an empirical model for tuning spatial resolution and noise in simulated images in virtual clinical trials in x-ray breast imaging. In extending previous studies performed for direct conversion a-Se detectors used in digital mammography and digital breast tomosynthesis, this work introduces the model for the case of cone-beam computed tomography dedicated to the breast that uses a indirect conversion flat-panel detector. In the simulations, the detector is modeled as an absorbing layer whose material and thickness reflect those of the scintillator of the detector of a clinical scanner. The simulated images are then computed as a dose deposit map. The detector response curve, modulation transfer function (MTF) and noise power spectrum (NPS) were measured on a real detector. The same measurements were replicated in-silico for the simulated detector and scanner. The comparison of simulated and measured detector response curves permits to recover pixel values at the clinical scale. The difference between the simulated and measured MTFs permitted to introduce a linear filter for compensating simulated model simplification that determines a better spatial resolution in the simulated images with respect to real images. This filter presented a Gaussian shape in the Fourier domain with a standard deviation of 1.09 mm-1 , derived from those of the measured and simulated MTF curves, of 0.86 mm-1 and 1.41 mm-1 , respectively. Finally, the analysis of the NPS permits to compensate for noise characteristics due to the simulated model simplifications. The model applied to the simulated projection images produced MTF and normalized NPS in simulated 3D images, comparable to those obtained for the clinical scanner
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
