| 1. |
- Abd-Ellah, Mahmoud Khaled, et al.
(författare)
-
A Review on Brain Tumor Diagnosis from MRI Images : Practical Implications, Key Achievements, and Lessons Learned
- 2019
-
Ingår i: Magnetic Resonance Imaging. - : Elsevier. - 0730-725X .- 1873-5894. ; 61, s. 300-318
-
Tidskriftsartikel (refereegranskat)abstract
- The successful early diagnosis of brain tumors plays a major role in improving the treatment outcomes and thus improving patient survival. Manually evaluating the numerous magnetic resonance imaging (MRI) images produced routinely in the clinic is a difficult process. Thus, there is a crucial need for computer-aided methods with better accuracy for early tumor diagnosis. Computer-aided brain tumor diagnosis from MRI images consists of tumor detection, segmentation, and classification processes. Over the past few years, many studies have focused on traditional or classical machine learning techniques for brain tumor diagnosis. Recently, interest has developed in using deep learning techniques for diagnosing brain tumors with better accuracy and robustness. This study presents a comprehensive review of traditional machine learning techniques and evolving deep learning techniques for brain tumor diagnosis. This review paper identifies the key achievements reflected in the performance measurement metrics of the applied algorithms in the three diagnosis processes. In addition, this study discusses the key findings and draws attention to the lessons learned as a roadmap for future research.
|
|
| 2. |
|
|
| 3. |
- Andersson, Jonathan, et al.
(författare)
-
MRI estimates of brown adipose tissue in children - Associations to adiposity, osteocalcin, and thigh muscle volume
- 2019
-
Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 0730-725X .- 1873-5894. ; 58, s. 135-142
-
Tidskriftsartikel (refereegranskat)abstract
- Context Brown adipose tissue is of metabolic interest. The tissue is however poorly explored in children. Methods: Sixty-three 7-year old subjects from the Swedish birth-cohort Halland Health and Growth Study were recruited. Care was taken to include both normal weight and overweight children, but the subjects were otherwise healthy. Only children born full term were included. Water-fat separated whole-body MRI scans, anthropometric measurements, and measurements of fasting glucose and levels of energy homeostasis related hormones, including the insulin-sensitizer osteocalcin, were performed. The fat fraction (FF) and effective transverse relaxation time (T-2(star)) of suspected brown adipose tissue in the cervical-supraclavicular-axillary fat depot (sBAT) and the FFs of abdominal visceral (VAT) and subcutaneous adipose tissue (SAT) were measured. Volumes of sBAT, abdominal VAT and SAT, and thigh muscle volumes were measured. Results: The FF in the sBAT depot was lower than in VAT and SAT for all children. In linear correlations including sex and age as explanatory variables, sBAT FF correlated positively with all measures of adiposity (p < 0.01), except for VAT FF and weight, positively with sBAT T-2* (p = 0.036), and negatively with osteocalcin (p = 0.017). When adding measures of adiposity as explanatory variables, sBAT FF also correlated negatively with thigh muscle volume (p < 0.01). Conclusions: Whole-body water-fat MRI of children allows for measurements of sBAT. The FF of sBAT was lower than that of VAT and SAT, indicating presence of BAT. Future studies could confirm whether the observed correlations corresponds to a hormonally active BAT.
|
|
| 4. |
- Andersson, Jonathan, et al.
(författare)
-
Water-fat separation incorporating spatial smoothing is robust to noise
- 2018
-
Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 0730-725X .- 1873-5894. ; 50, s. 78-83
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To develop and evaluate a noise-robust method for reconstruction of water and fat images for spoiled gradient multi-echo sequences.METHODS: The proposed method performs water-fat separation by using a graph cut to minimize an energy function consisting of unary and binary terms. Spatial smoothing is incorporated to increase robustness to noise. The graph cut can fail to find a solution covering the entire image, in which case the relative weighting of the unary term is iteratively increased until a complete solution is found. The proposed method was compared to two previously published methods. Reconstructions were performed on 16 cases taken from the 2012 ISMRM water-fat reconstruction challenge dataset, for which reference reconstructions were provided. Robustness towards noise was evaluated by reconstructing images with different levels of noise added. The percentage of water-fat swaps were calculated to measure performance.RESULTS: At low noise levels the proposed method produced similar results to one of the previously published methods, while outperforming the other. The proposed method significantly outperformed both of the previously published methods at moderate and high noise levels.CONCLUSION: By incorporating spatial smoothing, an increased robustness towards noise is achieved when performing water-fat reconstruction of spoiled gradient multi-echo sequences.
|
|
| 5. |
- Björkman-Burtscher, Isabella, et al.
(författare)
-
Quality assessment of localization technique performance in small volume in vivo 1H MR spectroscopy
- 1999
-
Ingår i: Magnetic Resonance Imaging. - 1873-5894. ; 17:10, s. 1511-1519
-
Tidskriftsartikel (refereegranskat)abstract
- A new phantom and evaluation method for experimental evaluation of 1H-magnetic resonance spectroscopy single volume localization techniques regarding signal contamination (C), defined as the part of the signal originating outside the volume of interest, is presented. The quality assessment method is based on a spherical phantom with an oil/water interface in order to reduce susceptibility effects, and applied for stimulated-echo acquisition method (STEAM) and spin-echo (SE) sequences, echo times of 270, 135, and 10 ms, and cubic volumes of interest (VOI) of 1(3), 1.5(3), 2(3), 2.5(3), and 3(3) cm3. To be able to mimic measurements of the contamination in three dimensions the physical gradients representing the three orthogonal directions for slice selection were shifted in the pulse sequences. Contamination values in one dimension differed between 6.5% and 8.4% in SE sequences, and between 0.7% and 13.8% in STEAM sequences. In STEAM sequences a decrease of C with increasing VOI size was observed while SE sequences showed comparable C values for the different VOI sizes tested. The total contamination in three dimensions were 19% and 18% in SE and STEAM sequences with a TE of 270 ms, and 7% in a STEAM sequence with a TE of 10 ms, respectively. The presented evaluation method is easily applied to the new phantom and showed high reproducibility.
|
|
| 6. |
- Brockstedt, Sara, et al.
(författare)
-
High-resolution diffusion imaging using phase-corrected segmented echo-planar imaging
- 2000
-
Ingår i: Magnetic Resonance Imaging. - 1873-5894. ; 18:6, s. 649-657
-
Tidskriftsartikel (refereegranskat)abstract
- Diffusion magnetic resonance imaging (MRI) was performed with a high-resolution segmented echo-planar imaging technique, which provided images with substantially less susceptibility artifacts than images obtained with single-shot echo-planar imaging (EPI). Diffusion imaging performed with any multishot pulse sequence is inherently sensitive to motion artifacts and in order to reduce motion artifacts, the presented method utilizes navigator echo phase corrections, performed after a one-dimensional Fourier transform along the frequency-encoding direction. Navigator echo phases were fitted to a straight line prior to phase correction to avoid errors from internal motion. In vivo imaging was performed using electro cardiographic (ECG) triggering. Apparent diffusion coefficient (ADC) maps were calculated on a pixel-by-pixel basis using up to seven diffusion sensitivities, ranging from b = 0 to 1129 x 10(6) s/m(2).
|
|
| 7. |
- Brockstedt, Sara, et al.
(författare)
-
Quantitative diffusion coefficient maps using fast spin-echo MRI
- 1998
-
Ingår i: Magnetic Resonance Imaging. - 1873-5894. ; 16:8, s. 877-886
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we have evaluated the performance of a diffusion-sensitive fast spin-echo (FSE) pulse sequence. The proposed pulse sequence utilises velocity-compensating diffusion-encoding gradients and includes the collection of navigator echoes. Spoiler gradients were inserted in the slice-selecting direction to minimise effects from stimulated echoes. Calculations of the b values showed that cross-terms between imaging gradients and diffusion gradients only led to a marginal increase of b values. Pixel-wise calculation of apparent diffusion coefficient (ADC) maps was performed numerically, considering cross-terms between diffusion-encoding and imaging gradients. The sequences investigated used echo train lengths of 16, 8 and 4 echoes and were encoded in either the slice-, frequency- or phase-encoding direction. In order to allow for higher b values a pulse-sequence version using non-motion compensating diffusion-encoding gradients was written. Phantom measurements were performed and the diffusion coefficients of water and acetone were reasonable. Seven healthy volunteers (age 28-50 years) were examined and apparent diffusion coefficient values agreed well with expected values. Diffusion-weighted images, apparent diffusion coefficient maps and images corresponding to the trace of the diffusion tensor of good quality were retrieved in vivo.
|
|
| 8. |
- Carlbom, Lina, et al.
(författare)
-
Pre-transplantation ³¹P-magnetic resonance spectroscopy for quality assessment of human pancreatic grafts : A feasibility study
- 2017
-
Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 0730-725X .- 1873-5894. ; 39, s. 98-102
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the feasibility of using (31)P-MRS for objective non-invasive quality assessment of human pancreas grafts prior to transplantation or islet isolation.Materials and methods: Pancreata from 5 human donors, 3 males and 2 females, aged 49-78years, with body mass index (BMI) 22-31kg/m(2), were included. Pancreata were perfused with histidine-tryptophan-ketoglutarate solution during procurement and stored in hypothermic condition (4°C) for 21-44h. During the period of hypothermic storage repeated spectra were obtained for each graft by (31)P-MRS (1.5Tesla) to measure the cold ischemia time (CIT) dependent changes of the phosphorous metabolites adenosine triphosphate (ATP), phosphomonoesters (PME), phosphodiesters (PDE) and inorganic phosphate (Pi), in the grafts. Graft temperature was measured immediately before and after MR-examination. Reference spectrum for non-viable tissue was obtained after graft exposure to room temperature.Results: PME/Pi, PDE/Pi and ATP/Pi spectral intensities ratios decreased with increasing CIT, reflecting the decreased viability of the grafts. PME/Pi ratio was the most discriminatory variable at prolonged CIT. (31)P-MRS could be performed without significantly increasing graft temperature.Conclusions: (31)P-MRS may provide quantitative parameters for evaluating graft viability ex vivo, and is a promising tool for objective non-invasive assessment of the quality of human pancreas grafts prior to transplantation or islet isolation.
|
|
| 9. |
- Colsenet, Roxane, et al.
(författare)
-
Diffusion of polyethyleneglycols in casein solutions and gels as studied by pulsed field gradient NMR
- 2005
-
Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 1873-5894 .- 0730-725X. ; 23:2, s. 347-348
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular transport characterized by diffusion coefficients is a key feature of food processes and especially in dairy processes. Caseins represent 80% of the protein content in milk and are directly involved in the formation of dairy gels. Consequently, providing a quantitative description of the solute diffusion in casein gels should contribute significantly to rationalization of the dairy processes. The objectives of this study were to study the self-diffusion coefficient of molecular probes [polyethyleneglycol (PEGs)] in casein solutions and gels, in particular with regard to the effects of the probe molecular size and casein concentration. We have shown that the PEG diffusion was an efficient tool to reveal the structural information relative to the gel matrix structure. (c) 2005 Elsevier Inc. All rights reserved.
|
|
| 10. |
|
|
