Implementation of Whole-Body MRI (MY-RADS) within the OPTIMUM/MUKnine multi-centre clinical trial for patients with myeloma.

BACKGROUND: Whole-body (WB) MRI, which includes diffusion-weighted imaging (DWI) and T1-w Dixon, permits sensitive detection of marrow disease in addition to qualitative and quantitative measurements of disease and response to treatment of bone marrow. We report on the first study to embed standardised WB-MRI within a prospective, multi-centre myeloma clinical trial (IMAGIMM trial, sub-study of OPTIMUM/MUKnine) to explore the use of WB-MRI to detect minimal residual disease after treatment. METHODS: The standardised MY-RADS WB-MRI protocol was set up on a local 1.5 T scanner. An imaging manual describing the MR protocol, quality assurance/control procedures and data transfer was produced and provided to sites. For non-identical scanners (different vendor or magnet strength), site visits from our physics team were organised to support protocol optimisation. The site qualification process included review of phantom and volunteer data acquired at each site and a teleconference to brief the multidisciplinary team. Image quality of initial patients at each site was assessed. RESULTS: WB-MRI was successfully set up at 12 UK sites involving 3 vendor systems and two field strengths. Four main protocols (1.5 T Siemens, 3 T Siemens, 1.5 T Philips and 3 T GE scanners) were generated. Scanner limitations (hardware and software) and scanning time constraint required protocol modifications for 4 sites. Nevertheless, shared methodology and imaging protocols enabled other centres to obtain images suitable for qualitative and quantitative analysis. CONCLUSIONS: Standardised WB-MRI protocols can be implemented and supported in prospective multi-centre clinical trials. Trial registration NCT03188172 clinicaltrials.gov; registration date 15th June 2017 https://clinicaltrials.gov/ct2/show/study/NCT03188172

A 3D discrete model of the diaphragm and human trunk

In this paper, a 3D discrete model is presented to model the movements of the trunk during breathing. In this model, objects are represented by physical particles on their contours. A simple notion of force generated by a linear actuator allows the model to create forces on each particle by way of a geometrical attractor. Tissue elasticity and contractility are modeled by local shape memory and muscular fibers attractors. A specific dynamic MRI study was used to build a simple trunk model comprised of by three compartments: lungs, diaphragm and abdomen. This model was registered on the real geometry. Simulation results were compared qualitatively as well as quantitatively to the experimental data, in terms of volume and geometry. A good correlation was obtained between the model and the real data. Thanks to this model, pathology such as hemidiaphragm paralysis can also be simulated.Comment: published in: "Lung Modelling", France (2006

MRI Visualization of Whole Brain Macro- and Microvascular Remodeling in a Rat Model of Ischemic Stroke: A Pilot Study

Using superparamagnetic iron oxide nanoparticles (SPION) as a single contrast agent, we investigated dual contrast cerebrovascular magnetic resonance imaging (MRI) for simultaneously monitoring macro- and microvasculature and their association with ischemic edema status (via apparent diffusion coefficient [ADC]) in transient middle cerebral artery occlusion (tMCAO) rat models. High-resolution T1-contrast based ultra-short echo time MR angiography (UTE-MRA) visualized size remodeling of pial arteries and veins whose mutual association with cortical ischemic edema status is rarely reported. ??R2?????R2*-MRI-derived vessel size index (VSI) and density indices (Q and MVD) mapped morphological changes of microvessels occurring in subcortical ischemic edema lesions. In cortical ischemic edema lesions, significantly dilated pial veins (p???=???0.0051) and thinned pial arteries (p???=???0.0096) of ipsilateral brains compared to those of contralateral brains were observed from UTE-MRAs. In subcortical regions, ischemic edema lesions had a significantly decreased Q and MVD values (p???<???0.001), as well as increased VSI values (p???<???0.001) than normal subcortical tissues in contralateral brains. This pilot study suggests that MR-based morphological vessel changes, including but not limited to venous blood vessels, are directly related to corresponding tissue edema status in ischemic stroke rat models

초고자장 자기공명영상의 B1+ 불균일성 완화를 위한 전자기 퍼텐셜 기반의 하이브리드 모드 성형 연구

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2021. 2. 박남규.Magnetic resonance imaging (MRI) is one of the most popular diagnostic imaging tools with its safety and applicability. By increasing the strength of operating B0, MRI has improved image quality, and recent research has enabled the imaging modality to increase the operating B0 fields over 7T, which is in the ultra-high-field (UHF) range. UHF MRI has various advantages, including the enhancement of the signal-to-noise ratio (SNR), spectral and spatial resolutions, and contrast. Especially, UHF MRI has an irreplaceable strength in precise scanning of the brain tissue to examine various neurological disorders. Nonetheless, the increase of the operating magnetic field causes the severe issue of RF B1+ field inhomogeneity, which is detrimental to homogeneous retrieval of the intensity, SNR, and contrast in MR image. To tackle the critical issue of inhomogeneity, a multitude of approaches for shimming the B1+ inhomogeneity have been proposed. Among them, RF passive shimming by pad structure filled with dielectric materials has proven its validity as a safe and well-compatible solution applicable to clinical applications. While successful in controlling the field distribution, most of the past efforts utilizing the local enhancement of B1+ in the vicinity of the pad structures, especially those in contact with the body, often resulted in deterioration of the global B1+ homogeneity over the ROI. Therefore, a study on a scheme for achieving the global homogeneity of B1+ is required. In this dissertation, we propose the notion of the mode shaping based on the evanescent coupling of the electromagnetic potentials to address the issue of B1+ field homogeneity. Treating the human head as a resonator, we apply an auxiliary potential well evanescent coupled to the head potential, to investigate the effects of the auxiliary potential configuration on the mode shaping and the resultant field homogenization. From the analysis and optimization, we obtain a robust mode shaping pad solution to achieve 2D global homogenization of axial B1+ field for the phantom of various geometry and the realistic voxel model of heterogeneous materials, which is applicable to the conventional 2D MRI scanning. Furthermore, extending the mode shaping approach with symmetry breaking, we propose the mode shaping solutions for 3D global homogenization of B1+ field. For the practical assessment of the feasibility of the mode shaping solutions, the SAR and robustness analysis of the solutions are also conducted. We believe that this study will expand the capability of the RF passive shimming in UHF MRI by providing an unconventional viewpoint and systematic guideline for the mitigation of B1+ inhomogeneity.자기 공명 영상법은 안정성과 확장성을 바탕으로 가장 광범위하게 이용되고 있는 영상 기법 중 하나이다. 자기 공명 영상법은 동작 정 자기장을 높임으로써 영상의 질을 향상시킬 수 있는데, 최근에는 7T 이상의 초고자장 자기 공명 영상법이 활용되고 있다. 초고자장 자기 공명 영상법은 신호 대비 잡음도, 공간 시간 해상도, 대조도 등을 향상시키는데, 이를 통해 특히 뇌 정밀 영상 촬영에 대체 불가한 강점을 가진다. 이러한 장점에도 불구하고 정 자기장의 증가는 고주파 신호 B1+ 필드의 불균일성을 야기하며, 이는 다시 이미지 퀄리티를 떨어뜨리는 등 원치 않는 영향으로 이어진다. B1+ 필드 불균일성 문제를 해결하기 위해 다양한 방법이 시도되었으며, 이 중에서도 유전체 물질로 채운 구조물인 패드를 이용한 수동 보정 접근은 기존 시스템에 호환이 되고 안정성을 인정받아 임상에서의 적용 가능성이 알려져 있는 대표적인 전략이다. 필드 패턴을 바꾸어주는 효과를 기반으로 하여 관심 영역에 붙여 주변부의 불균일성을 성공적으로 완화하는 이 방법은 최근 고 유전체 물질의 활용과 더불어 관심을 받고 있지만, 관심 부분 영역 전체에 대해서는 악영향을 수반하므로 광역 균일화를 위한 방법에 대한 연구가 필요하다. 본 학위 논문에서는, B1+ 필드의 광역 균일화를 위한 방법으로 퍼텐셜의 에바네센트 커플링을 기반으로 한 모드 성형 방식을 제안한다. 인체를 공진기로 보고 그것과 에바네센트 결합을 하는 보조 퍼텐셜을 적용함으로써 모드 성형 능력을 확인하였으며, 그것을 조절함으로써 스캐닝하려는 대상의 형태나 물질 분포에 강건한 축성 B1+ 필드의 광역 균일화를 구현할 수 있다. 또한, 해당 개념을 확장하여 삼차원 광역 균일화를 수행하는 모드 성형법을 제안한다. 이와 더불어, 이러한 모드 성형법의 실제적 적용가능성을 평가하기 위해 SAR와 강건성 분석을 수행하였다. 본 연구는 초고자장 자기 공명 영상법의 B1+ 불균일성 완화에 대한 색다른 시각과 체계적인 방법을 제공함으로써 고주파 신호 균일화에의 수동 보정 방법의 역할을 확장하는 지침이 될 것으로 기대된다.Abstract i Table of Contents iv List of Tables viii List of Figures ix Chapter 1. Introduction 1 1.1 Ultra-high-field magnetic resonance imaging: promising scheme for clinical imaging 2 1.2 Inhomogeneity problem in UHF MRI: Motivation 5 1.3 Dissertation overview 7 Chapter 2. Theory and method for the B1+ shimming 9 2.1 Electromagnetics in the UHF MRI 10 2.1.1 Principal physics of MRI system in view of electromagnetics 10 2.1.2 Issue of RF B1+ field inhomogeneity in UHF MRI 14 2.2 B1 shimming in UHF MRI 17 2.2.1 Current approaches and achievements for B1+ shimming 17 2.2.2 Background and motivation of our strategy for B1 shimming: mode shaping pad 21 2.3 Optical mode shaping based on evanescent coupling for mitigation of B1+ inhomogeneity 23 2.3.1 UHF MRI systems as an optical waveguide 23 2.3.2 Mode shaping via evanescent coupling in optics 24 2.3.3 Evanescent coupling of electromagnetic potentials in UHF MRI 26 2.4 Conclusion 29 Chapter 3. Hybrid mode shaping with auxiliary EM potential for global 2D homogenization 30 3.1 Mode shaping for 2D MRI scanning 31 3.2 Concept of hybrid mode shaping with auxiliary EM potential 34 3.3 Optimization process 38 3.4 Effect of the phantom and pad geometry and other material parameters of the pad 47 3.5 Effect of the inhomogeneous distribution of materials: human voxel model 52 3.6 Effect of the mode shaping potential pad on the SAR distributions 56 3.7 Robustness and stability of the mode shaping solution 59 3.8 Conclusion 61 Chapter 4. Hybrid mode shaping with auxiliary EM potential for global 3D homogenization 63 4.1 Mode shaping for 3D MRI scanning 64 4.2 Hat pad potential for lower-order mode excitation 66 4.3 Asymmetric shifted pad potential 72 4.4 Effect of the shifted potential pad on the SAR distribution 79 4.5 Robustness of the mode shaping with asymmetric potential pad 81 4.6 Conclusion 83 Chapter 5. Conclusion 84 Appendix A. Supplements for Chapter 3 86 A.1 Material and geometry for the MIDA voxel model 86 A.2 Excitation with realistic TEM coils 91 Appendix B. Supplements for Chapter 4 93 B.1 Cylinder can solution for the global homogenization 93 Appendix C 97 Bibliography 98 Abstract in Korean 109Docto

A Multivariate Surface-Based Analysis of the Putamen in Premature Newborns: Regional Differences within the Ventral Striatum

Many children born preterm exhibit frontal executive dysfunction, behavioral problems including attentional deficit/hyperactivity disorder and attention related learning disabilities. Anomalies in regional specificity of cortico-striato-thalamo-cortical circuits may underlie deficits in these disorders. Nonspecific volumetric deficits of striatal structures have been documented in these subjects, but little is known about surface deformation in these structures. For the first time, here we found regional surface morphological differences in the preterm neonatal ventral striatum. We performed regional group comparisons of the surface anatomy of the striatum (putamen and globus pallidus) between 17 preterm and 19 term-born neonates at term-equivalent age. We reconstructed striatal surfaces from manually segmented brain magnetic resonance images and analyzed them using our in-house conformal mapping program. All surfaces were registered to a template with a new surface fluid registration method. Vertex-based statistical comparisons between the two groups were performed via four methods: univariate and multivariate tensor-based morphometry, the commonly used medial axis distance, and a combination of the last two statistics. We found statistically significant differences in regional morphology between the two groups that are consistent across statistics, but more extensive for multivariate measures. Differences were localized to the ventral aspect of the striatum. In particular, we found abnormalities in the preterm anterior/inferior putamen, which is interconnected with the medial orbital/prefrontal cortex and the midline thalamic nuclei including the medial dorsal nucleus and pulvinar. These findings support the hypothesis that the ventral striatum is vulnerable, within the cortico-stiato-thalamo-cortical neural circuitry, which may underlie the risk for long-term development of frontal executive dysfunction, attention deficit hyperactivity disorder and attention-related learning disabilities in preterm neonates. © 2013 Shi et al

Cardiac adaptations to 60 day head-down-tilt bed rest deconditioning. Findings from the AGBRESA study

Aims: Reduced physical activity increases the risk of heart failure; however, non-invasive methodologies detecting subclinical changes in myocardial function are not available. We hypothesized that myocardial, left ventricular, systolic strain measurements could capture subtle abnormalities in myocardial function secondary to physical inactivity. Methods and results: In the AGBRESA study, which assessed artificial gravity through centrifugation as potential countermeasure for space travel, 24 healthy persons (eight women) were submitted to 60 day strict -6° head-down-tilt bed rest. Participants were assigned to three groups of eight subjects: a control group, continuous artificial gravity training on a short-arm centrifuge (30 min/day), or intermittent centrifugation (6 × 5 min/day). We assessed cardiac morphology, function, strain, and haemodynamics by cardiac magnetic resonance imaging (MRI) and echocardiography. We observed no differences between groups and, therefore, conducted a pooled analysis. Consistent with deconditioning, resting heart rate (∆8.3 ± 6.3 b.p.m., P < 0.0001), orthostatic heart rate responses (∆22.8 ± 19.7 b.p.m., P < 0.0001), and diastolic blood pressure (∆8.8 ± 6.6 mmHg, P < 0.0001) increased, whereas cardiac output (∆-0.56 ± 0.94 L/min, P = 0.0096) decreased during bed rest. Left ventricular mass index obtained by MRI did not change. Echocardiographic left ventricular, systolic, global longitudinal strain (∆1.8 ± 1.83%, P < 0.0001) decreased, whereas left ventricular, systolic, global MRI circumferential strain increased not significantly (∆-0.68 ± 1.85%, P = 0.0843). MRI values rapidly returned to baseline during recovery. Conclusion: Prolonged head-down-tilt bed rest provokes changes in cardiac function, particularly strain measurements, that appear functional rather than mediated through cardiac remodelling. Thus, strain measurements are of limited utility in assessing influences of physical deconditioning or exercise interventions on cardiac function

Degenerative cervical spine changes among early career fighter pilots : a 5-year follow-up

Introduction Degenerative changes of the cervical spine often cause disability and flight duty limitations among Finnish Air Force (FINAF) fighter pilots. We aimed to study the effect of +Gz exposure on degenerative changes in the cervical spine by comparing cervical MRIs of FINAF fighter pilots and controls. Methods At baseline, the volunteer study population consisted of 56 20-year-old FINAF male fighter pilots (exposure group) and 56 21-year-old Army and Navy cadets (control group). Both groups underwent MRI of the cervical spine at the baseline and after 5 years. Degenerative changes evaluated using MRI included intervertebral disc (IVD) degeneration (Pfirrmann classification), disc herniations, uncovertebral arthrosis, Schmorl’s nodes, Modic changes, spinal canal stenosis, kyphosis and scoliosis. Results The degree of IVD degeneration in the whole cervical spine increased significantly in both populations with no between-group differences. The prevalence of disc herniations also tended to increase in both populations with no difference in the incidence over the follow-up. However, pilots proved to have more disc herniations at the baseline and at the follow-up. There were virtually no between-group differences in other assessed degenerative changes. Discussion We found that IVD degeneration and the prevalence of disc herniations increased at a similar rate for fighter pilots and non-flying military students when all cervical levels were summed up. The lack of difference may be explained by the relatively low cumulative +Gz exposure during the first 5 years of a pilots’ career

NiftyNet: a deep-learning platform for medical imaging

Medical image analysis and computer-assisted intervention problems are increasingly being addressed with deep-learning-based solutions. Established deep-learning platforms are flexible but do not provide specific functionality for medical image analysis and adapting them for this application requires substantial implementation effort. Thus, there has been substantial duplication of effort and incompatible infrastructure developed across many research groups. This work presents the open-source NiftyNet platform for deep learning in medical imaging. The ambition of NiftyNet is to accelerate and simplify the development of these solutions, and to provide a common mechanism for disseminating research outputs for the community to use, adapt and build upon. NiftyNet provides a modular deep-learning pipeline for a range of medical imaging applications including segmentation, regression, image generation and representation learning applications. Components of the NiftyNet pipeline including data loading, data augmentation, network architectures, loss functions and evaluation metrics are tailored to, and take advantage of, the idiosyncracies of medical image analysis and computer-assisted intervention. NiftyNet is built on TensorFlow and supports TensorBoard visualization of 2D and 3D images and computational graphs by default. We present 3 illustrative medical image analysis applications built using NiftyNet: (1) segmentation of multiple abdominal organs from computed tomography; (2) image regression to predict computed tomography attenuation maps from brain magnetic resonance images; and (3) generation of simulated ultrasound images for specified anatomical poses. NiftyNet enables researchers to rapidly develop and distribute deep learning solutions for segmentation, regression, image generation and representation learning applications, or extend the platform to new applications.Comment: Wenqi Li and Eli Gibson contributed equally to this work. M. Jorge Cardoso and Tom Vercauteren contributed equally to this work. 26 pages, 6 figures; Update includes additional applications, updated author list and formatting for journal submissio

Symmetric diffeomorphic modeling of longtudinal structural MRI

This technology report describes the longitudinal registration approach that we intend to incorporate into SPM12. It essentially describes a group-wise intra-subject modeling framework, which combines diffeomorphic and rigid-body registration, incorporating a correction for the intensity inhomogeneity artifact usually seen in MRI data. Emphasis is placed on achieving internal consistency and accounting for many of the mathematical subtleties that most implementations overlook. The implementation was evaluated using examples from the OASIS Longitudinal MRI Data in Non-demented and Demented Older Adults