| 51. |
- Alamidi, Daniel, et al.
(author)
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Variable Flip Angle 3D Ultrashort Echo Time (UTE) T-1 Mapping of Mouse Lung: A Repeatability Assessment
- 2018
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In: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 48:3, s. 846-852
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Journal article (peer-reviewed)abstract
- Background: Lung T-1 is a potential translational biomarker of lung disease. The precision and repeatability of variable flip angle (VFA) T-1 mapping using modern 3D ultrashort echo time (UTE) imaging of the whole lung needs to be established before it can be used to assess response to disease and therapy. Purpose: To evaluate the feasibility of regional lung T-1 quantification with VFA 3D-UTE and to investigate long-and short-term T-1 repeatability in the lungs of naive mice. Field strength/Sequence: 3D free-breathing radial UTE (8 mu s) at 4.7T. Assessment: VFA 3D-UTE T-1 calculations were validated against T-1 values measured with inversion recovery (IR) in phantoms. Lung T-1 and proton density (S-0) measurements of whole lung and muscle were repeated five times over 1 month in free-breathing naive mice. Two consecutive T-1 measurements were performed during one of the imaging sessions. Statistical Tests: Agreement in T-1 between VFA 3D-UTE and IR in phantoms was assessed using Bland-Altman and Pearson's correlation analysis. The T-1 repeatability in mice was evaluated using coefficient of variation (CV), repeated-measures analysis of variance (ANOVA), and paired t-test. Results: Good T-1 agreement between the VFA 3D-UTE and IR methods was found in phantoms. T-1 in lung and muscle showed a 5% and 3% CV (1255 +/- 63 msec and 1432 +/- 42 msec, respectively, mean +/- SD) with no changes in T-1 or S-0 over a month. Consecutive measurements resulted in an increase of 2% in both lung T-1 and S-0. Data Conclusion: VFA 3D-UTE shows promise as a reliable T-1 mapping method that enables full lung coverage, high signal-to-noise ratio (similar to 25), and spatial resolution (300 mu m) in freely breathing animals. The precision of the VFA 3D-UTE method will enable better design and powering of studies.
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| 52. |
- Lundgren, Solveig M, 1943, et al.
(author)
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Radiographic research in Sweden - A review of dissertations
- 2019
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In: Radiography. - : Elsevier BV. - 1078-8174. ; 25
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Journal article (peer-reviewed)abstract
- Introduction: Radiographers have performed research since 1988 in Sweden. The amount of doctoral and licentiate dissertations written by registered diagnostic radiographers has increased considerably since 2000. How this new field of research was established and developed has facilitated understand of the boundaries that strengthen the professional evidence base. The aim of this dissertation review was to explore the nature and the current state of radiographic research, written by registered diagnostic radiographers in Sweden. Methods: Dissertations published between 1988 and 2017 were analysed both deductively and inductively with content analysis. Results: Radiographic research focused on structural factors, clinical radiography, radiographic technology and pedagogical approaches. The findings indicated a large interest in advancing patient information, wellbeing and care during examinations. The participants were predominantly clinical patients, followed by radiographers, adults/children and the general public. The most common study designs were descriptive with a trend towards interventional studies. Interviews and questionnaires were the most common data collection methods followed by clinical examinations and documents. Conclusion: The analyses demonstrate that the current radiographer research has its roots in clinical practice, focusing on pragmatic aspects and applied knowledge. The findings suggest that radiographer's dissertations meet the challenges of new technologies and working practise. If the knowledge is connected to the radiographic framework, radiography can be viewed as an independent discipline with its own philosophical base. When radiographers are encouraged to conduct research, evidence based knowledge increase which strengthens the profession. Radiography, as a scientific discipline is evolving in Sweden. (C) 2019 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.
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| 53. |
- Romu, Thobias, et al.
(author)
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Characterization of Brown Adipose Tissue by Water-Fat Separated Magnetic Resonance Imaging
- 2015
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In: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 42:6, s. 1639-1645
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Journal article (peer-reviewed)abstract
- Background: To evaluate the possibility of quantifying brown adipose tissue (BAT) volume and fat concentration with a high resolution, long echo time, dual-echo Dixon imaging protocol. Methods: A 0.42 mm isotropic resolution water-fat separated MRI protocol was implemented by using the second opposite-phase echo and third in-phase echo. Fat images were calibrated with regard to the intensity of nearby white adipose tissue (WAT) to form relative fat content (RFC) images. To evaluate the ability to measure BAT volume and RFC contrast dynamics, rats were divided into two groups that were kept at 48 or 22 degrees C for 5 days. The rats were then scanned in a 70 cm bore 3.0 Tesla MRI scanner and a human dual energy CT. Interscapular, paraaortal, and perirenal BAT (i/pa/pr-BAT) depots as well as WAT and muscle were segmented in the MRI and CT images. Biopsies were collected from the identified BAT depots. Results: The biopsies confirmed that the three depots identified with the RFC images consisted of BAT. There was a significant linear correlation (P< 0.001) between the measured RFC and the Hounsfield units from DECT. Significantly lower iBAT RFC (P=0.0064) and significantly larger iBAT and prBAT volumes (P=0.0017) were observed in the cold stimulated rats. Conclusion: The calibrated Dixon images with RFC scaling can depict BAT and be used to measure differences in volume, and fat concentration, induced by cold stimulation. The high correlation between RFC and HU suggests that the fat concentration is the main RFC image contrast mechanism.
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| 54. |
- Liu, Xixi, 1995, et al.
(author)
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Deep Nearest Neighbors for Anomaly Detection in Chest X-Rays
- 2024
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In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - 1611-3349 .- 0302-9743. ; 14349 LNCS, s. 293-302
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Conference paper (peer-reviewed)abstract
- Identifying medically abnormal images is crucial to the diagnosis procedure in medical imaging. Due to the scarcity of annotated abnormal images, most reconstruction-based approaches for anomaly detection are trained only with normal images. At test time, images with large reconstruction errors are declared abnormal. In this work, we propose a novel feature-based method for anomaly detection in chest x-rays in a setting where only normal images are provided during training. The model consists of lightweight adaptor and predictor networks on top of a pre-trained feature extractor. The parameters of the pre-trained feature extractor are frozen, and training only involves fine-tuning the proposed adaptor and predictor layers using Siamese representation learning. During inference, multiple augmentations are applied to the test image, and our proposed anomaly score is simply the geometric mean of the k-nearest neighbor distances between the augmented test image features and the training image features. Our method achieves state-of-the-art results on two challenging benchmark datasets, the RSNA Pneumonia Detection Challenge dataset, and the VinBigData Chest X-ray Abnormalities Detection dataset. Furthermore, we empirically show that our method is robust to different amounts of anomalies among the normal images in the training dataset. The code is available at: https://github.com/XixiLiu95/deep-kNN-anomaly-detection.
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| 55. |
- Narvaez, Omar, et al.
(author)
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Nonparametric distributions of tensor-valued Lorentzian diffusion spectra for model-free data inversion in multidimensional diffusion MRI
- 2024
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In: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 161:8
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Journal article (peer-reviewed)abstract
- Magnetic resonance imaging (MRI) is the method of choice for noninvasive studies of micrometer-scale structures in biological tissues via their effects on the time- and frequency-dependent (restricted) and anisotropic self-diffusion of water. While new designs of time-dependent magnetic field gradient waveforms have enabled disambiguation between different aspects of translational motion that are convolved in traditional MRI methods relying on single pairs of field gradient pulses, data analysis for complex heterogeneous materials remains a challenge. Here, we propose and demonstrate nonparametric distributions of tensor-valued Lorentzian diffusion spectra, or “D(ω) distributions,” as a general representation with sufficient flexibility to describe the MRI signal response from a wide range of model systems and biological tissues investigated with modulated gradient waveforms separating and correlating the effects of restricted and anisotropic diffusion.
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| 56. |
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| 57. |
- Björkman, Kristoffer, et al.
(author)
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Genotype-phenotype correlations in patients with complex I deficiency due to mutations in NDUFS1 and NDUFV1
- 2014
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In: Euromit 2014, 15-19 juni, Tampere, Finland.
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Conference paper (other academic/artistic)abstract
- Objectives: To study genotype-phenotype correlations in genes encoding complex I electron input module subunits. Materials and methods: We studied five patients with isolated complex I deficiency, three with NDUFS1 mutations and two with NDUFV1 mutations. A literature review of all reported cases of mutations in the affected genes was performed. Results: The literature review revealed pathological mutations in NDUFS1 for 18 patients in 17 families and correspondingly in NDUFV1 for 26 patients in 19 families. Unpublished clinical data for our five patients were added. Our study showed quite variable clinical courses; death before two years of age was seen in 41% of patients while 18% were alive at seven years. There was a significant difference between the NDUFS1 and NDUFV1 groups for clinical onset and life-span. Mutations in NDUFS1 were linked to a worse clinical course with earlier onset and earlier death. Conclusions: Genotype-phenotype correlations in patients with mutations affecting the genes that encode the electron input module of complex I vary, but patients with NDUFS1 mutation tend to have a worse clinical course than patients with NDUFV1 mutation. Identifying the mutations is of importance for accurate prognostic information and genetic counseling.
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| 58. |
- Latini, Francesco, M.D. 1982-
(author)
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Significance of white matter anatomy in interpreting features and behaviour of low-grade gliomas and implications for surgical treatment
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Diffuse gliomas are extremely heterogeneous tumours characterized by slow growth but extensive infiltration. Their kinetic features reflect the complex interaction over time with the surrounding brain, influencing treatment planning and outcome. Indeed, resection of diffuse gliomas present a surgical challenge due to their invasiveness and the preferential location in eloquent regions. White matter bundles are the main eloquent limit to surgical resection, but this anatomical-functional information cannot be predicted preoperatively on the individual level. The incomplete description of the human brain connectome, the complex application of pathological/lesion model to the brain connectomic organization, and the underestimated role of white matter anatomy in radiological classification systems are among the major limitations for the comprehension of the glioma/white matter interaction. The overall aim of this thesis was to explore a new approach and new techniques to study the glioma/white matter interaction. A combination of white matter dissection and diffusion tensor tractography (DTT) was used to describe the connectomic organization of two major temporo-occipital connections, the inferior and the middle longitudinal fasciculus. This information was applied to patients with diffuse gliomas, demonstrating how white matter analysis was important to decode patient specific cognitive and language impairment. A new classification system for diffuse gliomas, the Brain-Grid, was created, merging local radiological anatomy with a DTT atlas for infiltration analysis. This standardized radiological tool provided information on subcortical extension (tumour invasiveness), speed, and preferential direction of glioma progression. Applied to a larger cohort of patients, differences were detected between diffuse gliomas subtypes. Tumour invasiveness and the preferential location, type, and extent of white matter involvement differed, impacting overall survival. Regional differences in white matter infiltration were detected among five major white matter bundles, and possible favourable morphological and diffusion features were investigated with transmission electron microscopy and DTT. Fibre diameter, myelin thickness, and the organization of the white matter fibres were different in regions with high infiltration frequency, providing a possible link to the preferential location of diffuse gliomas. Finally, the white matter connectivity, tumour-induced neuroplasticity, clinical and demographic information, preoperative assessment (neuropsychological and language evaluation) were compared with intraoperative findings during awake surgery. Neuropsychological impairment was associated with more invasive tumours and a higher risk of the intraoperative finding of eloquent tumour. The pattern of early cortical neuroplasticity seemed exhausted at the time of diagnosis, with age as a factor predicting the neuroplasticity potential. The combined use of these new techniques revealed new insights into the glioma/white matter interaction. The results provided in this thesis, describe a new way to structure the multidisciplinary perioperative management of these patients. This new information may improve the functional outcome at the individual level, resulting in prolonged survival for adults with diffuse gliomas.
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| 59. |
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| 60. |
- Wang, Chunliang, 1980-, et al.
(author)
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An interactive software module for visualizing coronary arteries in CT angiography
- 2008
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In: International Journal of Computer Assisted Radiology and Surgery. - Heidelberg/Berlin : Springer. - 1861-6410 .- 1861-6429. ; 3:1-2, s. 11-18
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Journal article (peer-reviewed)abstract
- A new software module for coronary artery segmentation and visualization in CT angiography (CTA) datasets is presented, which aims to interactively segment coronary arteries and visualize them in 3D with maximum intensity projection (MIP) and volume rendering (VRT).Materials and Methods: The software was built as a plug-in for the open-source PACS workstation OsiriX. The main segmentation function is based an optimized “virtual contrast injection” algorithm, which uses fuzzy connectedness of the vessel lumen to separate the contrast-filled structures from each other. The software was evaluated in 42 clinical coronary CTA datasets acquired with 64-slice CT using isotropic voxels of 0.3–0.5 mm.Results: The median processing time was 6.4 min, and 100% of main branches (right coronary artery, left circumflex artery and left anterior descending artery) and 86.9% (219/252) of visible minor branches were intact. Visually correct centerlines were obtained automatically in 94.7% (321/339) of the intact branches.Conclusion: The new software is a promising tool for coronary CTA post-processing providing good overviews of the coronary artery with limited user interaction on low-end hardware, and the coronary CTA diagnosis procedure could potentially be more time-efficient than using thin-slab technique.
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