| 31. |
- Petridou, Elia, et al.
(author)
-
Breast fat volume measurement in a wide-bore 3T MR: comparison of traditional mammographic density evaluation with MR density measurements using automatic segmentation.
- 2015
-
Conference paper (other academic/artistic)abstract
- Aims and objectivesVariations in breast density in imaging are caused by varying proportions of fat and fibro-glandular tissue. Breast density is an independent marker of breast cancer risk and therefore a number of techniques have been developed to measure breast density using different imaging modalities. The aim of this research was to compare a fully automated technique of producing volumetric measurements of fat and fibroglandular breast tissue from segmented magnetic resonance imaging (MRI) and to compare with the well-established, observer-dependent Breast Imaging Reporting and Data Systems (BI-RADS) density classification using mammography.Methods and materialsThis was a prospective inter-method comparison study. The study design was a prospective analysis of volumetric breast density obtained from breast MRI scans compared with mammographic breast density using BIRADS. Ethical approval for the study was obtained from the local Research Ethics Committee. 40 women undergoing mammography and dynamic breast MRI as part of their clinical management were recruited. Fat-water separated MR images derived from a 2 point Dixon technique using phase-sensitive reconstruction and atlas based segmentation were obtained before and after the administration of intravenous gadolinium. Breast density, which was defined the proportion of breast fat subtracted from the total volume of the breast, was assessed using proprietary software (Advanced MR Analytics (AMRA), Linköping, Sweden). The method was previously described and first used for measurement of abdominal fat.The results were compared to the widely used four-quartile quantitative BIRADS scale undertaken by two experienced breast radiologists. ResultsThe mean unenhanced breast percentage of fibro-glandular tissue measured on MRI was 0.31 ± 0.22 (mean ± SD) for the left and 0.29 ± 0.21 for the right. The mean density on the contrast-enhanced images was 0.32 ± 0.19 for the left and 0.32 ± 0.2 for right. There was "almost perfect" correlation between the quantification pre and post-contrast breast fibro- glandular tissue quantification: Spearman correlation rho=0.98 (95% confidence intervals (CI): 0.97-0.99) for the left and rho=0.99 (CI: 0.98-0.99) for the right.For each of the BIRADS scores 1-4 observer 1 scored a total number of breasts as n=2,35,26,15 (total 80) and observer 2 scored n=4,25,45,16 respectively. Correlation between BIRADS scores and automated MRI breast density was significant for both operators, Spearman Correlation coefficient rho=0.75. ConclusionAutomated breast fat density measurement using MR correlates strongly with the current mammographic standard BIRADS. Results for percentage fibro-glandular component on unenhanced breast MR correlate very closely with post-contrast MR. Breast density measurements derived from automated segmentation of unenhanced breast MRI could be used instead of mammographic measurements for assessing breast cancer risk.
|
|
| 32. |
- Romu, Thobias, et al.
(author)
-
A randomized trial of cold-exposure on energy expenditure and supraclavicular brown adipose tissue volume in humans
- 2016
-
In: Metabolism-Clinical and Experimental. - : Elsevier BV. - 0026-0495 .- 1532-8600. ; 65:6, s. 926-934
-
Journal article (peer-reviewed)abstract
- Objective. To study if repeated cold-exposure increases metabolic rate and/or brown adipose tissue (BAT) volume in humans when compared with avoiding to freeze. Design. Randomized, open, parallel-group trial. Methods. Healthy non-selected participants were randomized to achieve cold-exposure 1 hour/day, or to avoid any sense of feeling cold, for 6 weeks. Metabolic rate (MR) was measured by indirect calorimetry before and after acute cold-exposure with cold vests and ingestion of cold water. The BAT volumes in the supraclavicular region were measured with magnetic resonance imaging (MRI). Results. Twenty-eight participants were recruited, 12 were allocated to controls and 16 to cold-exposure. Two participants in the cold group dropped out and one was excluded. Both the non-stimulated and the cold-stimulated MR were lowered within the group randomized to avoid cold (MR at room temperature from 1841 +/- 199 kCal/24 h to 1795 +/- 213 kCal/24 h, p = 0.047 cold-activated MR from 1900 +/- 150 kCal/24 h to 1793 +/- 215 kCal/24 h, p = 0.028). There was a trend towards increased MR at room temperature following the intervention in the cold-group (p = 0.052). The difference between MR changes by the interventions between groups was statistically significant (p = 0.008 at room temperature, p = 0.032 after cold-activation). In an on-treatment analysis after exclusion of two participants that reported >= 8 days without cold-exposure, supraclavicular BAT volume had increased in the cold-exposure group (from 0.0175 +/- 0.015 1 to 0.0216 +/- 0.014 1, p = 0.049). Conclusions. We found evidence for plasticity in metabolic rate by avoiding to freeze compared with cold-exposure in a randomized setting in non-selected humans.
|
|
| 33. |
- Romu, Thobias, et al.
(author)
-
Characterization of Brown Adipose Tissue by Water-Fat Separated Magnetic Resonance Imaging
- 2015
-
In: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 42:6, s. 1639-1645
-
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.
|
|
| 34. |
- Romu, Thobias, 1984-
(author)
-
Fat-Referenced MRI : Quantitative MRI for Tissue Characterization and Volume Measurement
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- The amount and distribution of adipose and lean tissues has been shown to be predictive of mortality and morbidity in metabolic disease. Traditionally these risks are assessed by anthropometric measurements based on weight, length, girths or the body mass index (BMI). These measurements are predictive of risks on a population level, where a too low or a too high BMI indicates an increased risk of both mortality and morbidity. However, today a large part of the world’s population belongs to a group with an elevated risk according to BMI, many of which will live long and healthy lives. Thus, better instruments are needed to properly direct health-care resources to those who need it the most.Medical imaging method can go beyond anthropometrics. Tomographic modalities, such as magnetic resonance imaging (MRI), can measure how we have stored fat in and around organs. These measurements can eventually lead to better individual risk predictions. For instance, a tendency to store fat as visceral adipose tissue (VAT) is associated with an increased risk of diabetes type 2, cardio-vascular disease, liver disease and certain types of cancer. Furthermore, liver fat is associated with liver disease, diabetes type 2. Brown adipose tissue (BAT), is another emerging component of body-composition analysis. While the normal white adipose tissue stores fat, BAT burns energy to produce heat. This unique property makes BAT highly interesting, from a metabolic point of view.Magnetic resonance imaging can both accurately and safely measure internal adipose tissue compartments, and the fat infiltration of organs. Which is why MRI is often considered the reference method for non-invasive body-composition analysis. The two major challenges of MRI based body-composition analysis are, the between-scanner reproducibility and a cost-effective analysis of the images. This thesis presents a complete implementation of fat-referenced MRI, a technique that produces quantitative images that can increase both inter-scanner and automation of the image analysis.With MRI, it is possible to construct images where water and fat are separated into paired images. In these images, it easy to depict adipose tissue and lean tissue structures. This thesis takes water-fat MRI one step further, by introducing a quantitative framework called fat-referenced MRI. By calibrating the image using the subjects' own adipose tissue (paper II), the otherwise non-quantitative fat images are made quantitative. In these fat-referenced images it is possible to directly measure the amount of adipose tissue in different compartments. This quantitative property makes image analysis easy and accurate, as lean and adipose tissues can be separated on a sub-voxel level. Fat-referenced MRI further allows the quantification and characterization of BAT.This thesis work starts by formulating a method to produce water-fat images (paper I) based on two gradient recall images, i.e.\ 2-point Dixon images (2PD). It furthers shows that fat-referenced 2PD images can be corrected for T2*, making the 2PD body-composition measurements comparable with confounder-corrected Dixon measurements (paper III}).Both the water-fat separation method and fat image calibration are applied to BAT imaging. The methodology is first evaluated in an animal model, where it is shown that it can detect both BAT browning and volume increase following cold acclimatization (paper IV). It is then applied to postmortem imaging, were it is used to locate interscapular BAT in human infants (paper V). Subsequent analysis of biopsies, taken based on the MRI images, showed that the interscapular BAT was of a type not previously believed to exist in humans. In the last study, fat-referenced MRI is applied to BAT imaging of adults. As BAT structures are difficult to locate in many adults, the methodology was also extended with a multi-atlas segmentation methods (paper VI).In summary, this thesis shows that fat-referenced MRI is a quantitative method that can be used for body-composition analysis. It also shows that fat-referenced MRI can produce quantitative high-resolution images, a necessity for many BAT applications.
|
|
| 35. |
|
|
| 36. |
- Romu, Thobias, et al.
(author)
-
Robust Water Fat Separated Dual-Echo MRI by Phase-Sensitive Reconstruction
- 2017
-
In: Magnetic Resonance in Medicine. - : Wiley-Blackwell. - 0740-3194 .- 1522-2594. ; 78:3, s. 1208-1216
-
Journal article (peer-reviewed)abstract
- Purpose: To develop and evaluate a robust water-fat separation method for T1-weighted symmetric two-point Dixon data.Methods: A method for water-fat separation by phase unwrapping of the opposite-phase images by phase-sensitive reconstruction (PSR) is introduced. PSR consists of three steps; 1, identification of clusters of tissue voxels; 2, unwrapping of the phase in each cluster by solving Poisson’s equation; 3, find the correct sign of each unwrapped opposite-phase cluster, so that the water-fat images are assigned the correct identities. The robustness was evaluated by counting the number of water-fat swap artifacts in a total of 733 image volumes. The method was also compared to commercial software.Results: In the water-fat separated image volumes, the PSR method failed to unwrap the phase of one cluster and misclassified 10. One swap was observed in areas affected by motion and was constricted to the affected area. Twenty swaps were observed surrounding susceptibility artifacts, none of which spread outside the artifact affected regions. The PSR method had fewer swaps when compared to commercial software.Conclusion: The PSR method can robustly produce water-fat separated whole-body images based on symmetric two-echo spoiled gradient echo images, under both ideal conditions and in the presence of common artifacts.
|
|
| 37. |
- Romu, Thobias, et al.
(author)
-
The effect of flip-angle on body composition using calibrated water-fat MRI.
- 2016
-
Conference paper (other academic/artistic)abstract
- This study tested how the flip angle affects body composition analysis by MRI, if adipose tissue is used as an internal intensity reference. Whole-body water-fat images with flip angle 5° and 10° were collected from 29 women in an ongoing study. The images were calibrated based on the adipose tissue signal and whole-body total adipose, lean and soft tissue volumes were measured. A mean difference of 0.29 L, or 0.90 % of the average volume, and a coefficient of variation of 0.40 % was observed for adipose tissue.
|
|
| 38. |
|
|
| 39. |
-
Special issue on ICPR 2014 awarded papers
- 2016
-
Editorial collection (peer-reviewed)abstract
- We, the Guest Editors of this special issue of Pattern Recognition Letters are pleased to share these contributions with you. The papers included here are based on work from the 22nd International Conference on Pattern Recognition (IAPR) in Stockholm, Sweden, held August 24–28, 2014. The papers selected for this special issue were those winning one of the IAPR awards, as well as one paper by a former student of the winner of the KS Fu Prize, Prof. Jitendra Malik. Taken together, this body of work represents some of the finest research being conducted by the IAPR community worldwide, it builds on a rich legacy of accomplishment by the entire community, and it offers a view to the future, to where we are going as a scientific community.For each of the award-winning papers, the authors were asked to revise and extend their contributions to full journal length and to provide true added value vis-à-vis the original conference submission. In some cases, the authors elected to modify the titles slightly, and in some cases the list of authors has also been modified. The resulting manuscripts were sent out for full review by a different set of referees than those who reviewed the conference versions. The process, including required revisions, was in accordance with the standing editorial policy of Pattern Recognition Letters, resulting in the final versions accepted and appearing here. These are thoroughly vetted, high-caliber scientific contributions.It has been our honor to serve as Guest Editors for this special issue. We would like to thank the Editors of Pattern Recognition Letters for allowing us this opportunity. We are especially grateful to Dr. Gabriella Sanniti di Baja for her enthusiasm, support, and her willingness to keep prodding us along to bring the special issue through to completion. We would also like to thank all of those who reviewed the papers, both originally for the conference and subsequently for the journal, and those who served on the ICPR awards and KS Fu Prize committees.Finally, we express our heartfelt gratitude to all of the authors for taking the time to prepare these versions for our collective enlightenment, sharing their knowledge, innovation, and discoveries with the rest of us.
|
|
| 40. |
- West, Janne, et al.
(author)
-
Automatic combined whole-body muscle and fat volume quantification using water-fat separated MRI in postmenopausal women
- 2015
-
In: International Society for Magnetic Resonance in Medicine Annual Meeting.
-
Conference paper (other academic/artistic)abstract
- Quantitative and exact measurements of fat and muscle in the body are important when addressing some of the greatest health-challenges today. In this study whole-body combined regional muscle and fat volume quantification was validated in a group of postmenopausal women, where the body composition is changing. Twelve subjects were scanned with a 4-echo 3D gradient-echo sequence. Water and fat image volumes were calculated using IDEAL, and image intensity correction was performed. Subsequently, automatic tissue segmentation was established using non-rigid morphon based registration. Whole-body regional fat and muscle segmentation could be performed with excellent test-retest reliability, in a single 7-minutes MR-scan.
|
|
