bluuebunny/crossref_metadata_2025 huggingface dataset:
Dictionary Generation and Matching with Conditional Invertible Neural Networks for Cardiac MR Fingerprinting
Authors: Fletcher Thomas , Velasco Carlos , Cruz Gastão , Schneider Alina , Botnar René , Prieto Claudia
Published: August 2023

Dictionary generation and pattern matching are two important bottlenecks in cardiac MRF. Dictionaries must be recalculated for each new scan as they depend on the subject’s heart rate variability and both dictionaries and the length of pattern matching grow exponentially with the number of parameters being considered. We propose a conditional invertible neural network capable of both dictionary generation and parameter estimation for T1, T2 and T1ρ cardiac MRF. The network achieves excellent results on EPG-generated data (inner product >0.999, parameters’ relative error <1.5%) and good results for in-vivo data (mean relative errors for myocardium ranging from 2.2% to 15.1%).
Free-Breathing Liver Fat Quantification using Radial Acquisition on a High-Performance 0.55T MRI System
Authors: Shih Shu-Fu , Cui Sophia , Zhong Xiaodong , Tasdelen Bilal , Yagiz Ecrin , Nayak Krishna , Wu Holden
Published: August 2023

MRI proton-density fat fraction (PDFF) is used for non-invasive diagnosis of fatty liver disease, and has been validated at 1.5T and 3T field strengths. There is renewed interest in lower field strengths, such as 0.55T, because of potential advantages such as lower hardware/siting costs and a larger bore diameter. This study investigated PDFF quantification at 0.55T and validated PDFF quantification at 0.55T using Cartesian and Radial Dixon techniques in a reference phantom, and demonstrated the feasibility of in vivo free-breathing radial liver PDFF quantification in healthy subjects at 0.55T.
Quasiperiodic Patterns in resting state fMRI signal reflect dynamics of cortical slow rhythms
Authors: Sharghi Vahid , Maltbie Eric , Pan Wen-Ju , Keilholz Shella , Gopinath Kaundinya
Published: August 2023

In this study, we tested hypothesis advanced by some groups that brain slow rhythms serve as the neurophysiological basis of resting state fMRI (rsfMRI). Putative suppression of cortical rhythms with an established technique, led to significant reduction in the amplitude of rsfMRI quasi-periodic patterns (QPPs), and enhancement in the rsfMRI measures of intrinsic functional connectivity FC in canonical brain function networks in rats. The results indicate cortical slow rhythms serve as the genesis of only the vigilance dependent components (e.g., QPP) of rsfMRI signals. Further attenuation of these non-specific signals enhances delineation of brain function networks.
The BigMac dataset: interconnecting MR signals with microstructure profiles in the cortex
Authors: Howard Amy , Huszar Istvan , Cottaar Michiel , Daubney Greg , Khrapitchev Alexandre , Mars Rogier , Mollink Jeroen , Roumazeilles Lea , Scott Connor , Smart Adele , Sallet Jerome , Jbabdi Saad , Miller Karla
Published: August 2023

Microscopy data can provide detailed descriptions of how cortical microstructure varies across the brain. However, the relationship between cortical microstructure and MRI signals remains relatively unexplored. Here we develop a pipeline to extract cortical profiles from co-registered MRI and microscopy data in the BigMac dataset. We compare cortical profiles of cell density and microstructural dispersion from Nissl-stained histology slides with matched profiles from structural and diffusion MRI. Using CCA we find modes of microstructure variation common to microscopy and structural MRI, but not diffusion, indicating variable sensitivity of the MR metrics to brain-wide variations in Nissl-stained cytoarchitecture.
Accelerated Magnetic Resonance Imaging with Flow-Based Priors
Authors: Fraaz Frederik , Heckel Reinhard
Published: August 2023

Convolutional neural networks trained end-to-end achieve state-of-the-art image quality for accelerated MRI. But end-to-end networks are trained for a specific undersampling operator. A more flexible approach that can work with any undersampling operator at inference is to train a generative image prior and impose it during reconstruction. In this work, we train a flow-based generator on image patches and then impose it as a prior in the reconstruction. We find that this method achieves slightly better reconstruction quality than state-of-the-art un-trained methods and slightly worse quality than neural networks trained end-to-end on the 4x accelerated multi-coil fastMRI dataset.
Hyperpolarized multiple quantum coherences at ultra-low magnetic fields increase 15N parahydrogen-induced polarization
Authors: Pravdivtsev Andrey , Kempf Nicolas , Plaumann Markus , Bernarding Johannes , Scheffler Klaus , Hövener Jan-Bernd , Buckenmaier Kai
Published: August 2023

We used signal amplification by reversible exchange of parahydrogen (SABRE) at low (~1 mT) and ultra-low (~1 μT, ULF) magnetic fields. We proposed and used ULF correlation spectroscopy (COSY) method to analyze PHIP spin order in real-time. Coherences up to the third-order were observed experimentally. Furthermore, we analyzed SABRE in alternating magnetic fields (alt-SABRE). We measured the evolution of 1H-15N zero-quantum coherences and have shown that they persist during field alternation and depend on the magnetic field strength. The resulting 15N-polarization in the alt-SABRE experiment was with magnetic was appoximately 30% higher.
Dynamic 1H MR spectroscopy of yeast metabolism during gamma irradiation using a 1.5T MR-Linac
Authors: Lawrence Liam , Iakovenko Viktor , Oakden Wendy , Chan Rachel , Stanisz Greg , Lau Angus
Published: August 2023

1H MR spectroscopy (MRS) can detect metabolic changes in treated tumours that could indicate therapeutic response. MR response assessment might inform radiation dose plan adaptation on MRI linear accelerators (MR-Linacs). We report the first MRS experiments on a 1.5T MR-Linac. Dynamic spectra of yeast during fermentation were acquired with and without irradiation, to measure real-time changes in metabolism. Ethanol production was detectable. The Larmor frequency drifted by 33 Hz over 11 minutes during irradiation, degrading spectral quality. While no differences in ethanol production were detected between irradiation/control experiments, the phantom setup could be optimized to increase dose and improve repeatability.
Reliability and test-retest reproducibility of advanced diffusion metrics in healthy older adults
Authors: Barrett Rachel , Dallyn Robert , Cahart Marie-Stephanie , Stones Richard , Timmers Maarten , Williams Steven , Dell'Acqua Flavio
Published: August 2023

Reliability and test-retest reproducibility of simple and advanced diffusion metrics were evaluated in healthy older adults. Advanced models such as Diffusion Kurtosis Imaging, White Matter Tract Integrity, Neurite Orientation Dispersion and Density Imaging and other multi-compartment methods have greater specificity but lower reliability and reproducibility than simple models such as DTI and spherical harmonic metrics. All models nevertheless had good or acceptable reproducibilty and reliability in certain cases. Particular care may be given when planning clinical research applications with advanced metrics, as greater sample sizes and/or improved data quality may be needed.
Segmentation and Quantification of Venous structures and Perivascular Spaces in the Thalamus in Epilepsy Patients at 7T
Authors: Langan Mackenzie , Verma Gaurav , Smith Derek , Delman Bradley , Fields Madeline , Feldman* Rebecca , Balchandani* Priti
Published: August 2023

Here we outline a preliminary analysis using a novel method which leverages UHF neuroimaging to measure detectable differences in vasculature within the thalamus that may not be detectable at lower field strengths. We provide a tool for detection and quanitifcation of vessels, perivascular spaces, and subsequent overlaps within the thalamus which may be relevant to uncover possible underlying neuroinflammatory processes in focal epilepsy patients. In our analysis, we found a significant difference in the number of thalamic vessels in patients compared to controls, providing a possible marker to measure abnormal or disordered vessel growth possibly associated with increased seizure activity.
HyperCEST Performance of Liposomal Nanocarriers using a CrA-Lipopeptide Building Block
Authors: Schröder Leif , Jost Jan Oliver
Published: August 2023

MRI reporters for hyperpolarized 129Xe CEST need further improvement in order to sufficiently outcompete the intrinsic loss of hyperpolarization appearing under in vivo conditions. This study opens up a possibility by accelerating the CEST build-up for the well-known Xe host CrA-ma by two orders of magnitude. We designed a liposome decorated with a CrA-lipopeptide. To avoid inefficiency from back exchange, the lipopeptide fraction should be kept relatively low (e.g., 2 mol%). Complete saturation transfer could be easily achieved for maximum possible image contrast in 129Xe MRI scans. This study pinpoints a large flexibility for designing powerful HyperCEST agents.
Assessment of subtle BBB disruption using Focused Ultrasound: comparison between the contrast agent exchange rate and the water exchange rate
Authors: Bae Jonghyun , Zhang Jin , Stavarache Mihaela , Das Ayesha , Qayyum Sawwal , Kiser Karl , Kim Sungheon
Published: August 2023

This study explores two different approachs of measuring subtle BBB disruption. To induce different levels of BBB disruption, we used a focused ultrasound (FUS) sonication with intravenously injected microbubbles with an animal model. Each animal underwent FUS procedure with different acoustic power levels. We compared the changes measured using DCE-MRI with Gadolinium-based contrast agent for volume transfer rate constant and Ferumoxytol-based ACE-MRI to measure transendotheliel water exchange rate. Our results suggest that both the water exchange rate and the contrast exchange rate show sensitive detection of subtle BBB disruption, which could shed light on understanding different permeability changes in BBB.
Investigating Early Brain Development and Executive Function in Young Children
Authors: Pletcher Colleen , Heinrich Lauren , DiPiero Marissa , Alexander Andrew , Kecskemeti Steven , Planalp Elizabeth , Dean Douglas
Published: August 2023

The emergence of executive function (EF) in children is an important developmental process that impacts later cognitive and behavioral outcomes; however, much remains unknown about the neural processes underlying the development of EF. In this study, we quantified volumetric measures from structural MRI to investigate associations between EF and brain structure in children aged 3 to 10 years old. Results indicated that there were correlations between EF and structures in subcortical brain regions and regions of the frontal and parietal lobes.
Choreography Controlled (ChoCo) by synchronized video for motion artifact reproducibility and dataset generation
Authors: Dabrowski Oscar , Courvoisier Sébastien , Falcone Jean-Luc , Klauser Antoine , Songeon Julien , Kocher Michel , Chopard Bastien , Lazeyras Francois
Published: August 2023

In the age of artificial intelligence, there is a need for simple and inexpensive frameworks aimed at performing standardized reproducible motion-controlled experiments allowing the creation of datasets of motion corrupted in vivo MRI scans. Focused on human brain imaging, we propose ChoCo: a choreography controlled protocol for reproducible head motion and an ad-hoc hardware device for synchronization between an MRI scanner and a movie displaying motion to be performed. A proof of concept demonstrated that 6 participants were able to reproduce head choreographies accurately. The resulting motion corrupted brain images show qualitatively similar artifacts, confirming consistent motion reproduction among subjects.
Modelling inhomogeneous magnetization transfer in myelin and intra-/extra-cellular water in normal and injured rat spinal cords
Authors: Lam Michelle , Yung Andrew , Liu Jie , Tetzlaff Wolfram , Kozlowski Piotr
Published: August 2023

An MR imaging technique called inhomogeneous magnetization transfer (ihMT) could potentially be used for quantitative myelin imaging by using T1D filtering to filter out the short dipolar relaxation time (T1D) components. However, to show that ihMT with T1D filtering is myelin-specific, we need to confirm that myelin has the longest T1D in nerve tissue. Here, we combined ihMT and myelin water imaging (MWI) to separate the ihMT signal in myelin water from intra-/extra-cellular water, which we fitted using a four-pool model with dipolar order reservoirs. Our model allowed us to connect myelin with myelin water and measure myelin’s T1D.
Repeatability of B1 Inhomogeneity Correction of Volumetric (3D) Glutamate CEST via High-Permittivity Dielectric Padding at 7T
Authors: Jacobs Paul , Nanga Ravi , Cember Abigail , Tisdall Dylan , Das Sandhitsu , Detre John , Roalf David , Reddy Ravinder
Published: August 2023

Dielectric pads were used to improve the contrast of volumetric (3D) gluCEST via enhanced homogenization of B1 fields. Effective placement of the pads required additional coverage of the face due to their physical size to achieve the saturated B1 strength necessary to recover the gluCEST signal from the anterior portions of the brain. The origin of gluCEST's need for high B1 is discussed, and examples of 3D gluCEST images acquired with and without the use of the dielectric pads are provided and repeatability of the 3D gluCEST in the presence of pad placement was determined.
Fiber coupling (FICO) measure using anisotropic smoothing of track orientation density images for tractogram filtering
Authors: Aydogan Dogu Baran
Published: August 2023

Tractography is a powerful tool to study structural connectivity of the brain. However, its accuracy is known to be limited and tractograms are contaminated with large numbers of false positive streamlines. In this work, we propose a novel tractogram filtering approach. Our method leverages the topographic regularity of connections with which nearby streamline tend to follow similar trajectories. With this observation, we introduce an anisotropic smoothing approach for track orientation density images. These images are back projected onto the streamlines, which provides information about fiber-to-bundle coupling (FICO). Streamlines are then filtered by thresholding their FICO value.
Multi-level fiber tractography in brain tumor patients using functional mapping for seeding
Authors: Zhylka Andrey , Pluim Josien , Kofler Florian , Radwan Ahmed , De Luca Alberto , Schroeder Axel , Wiestler Benedikt , Kirschke Jan , Menze Bjoern , Sunaert Stefan , Leemans Alexander , Krieg Sandro , Sollmann Nico
Published: August 2023

Navigated transcranial magnetic stimulation (nTMS) motor mapping allows locating function in the individual patient pre-operatively and, to a certain extent, decreases the false-positive rate for fiber tractography. However, the false-negative rate is still high. In this work we evaluate novel multi-level fiber tractography (MLFT) along with conventional deterministic algorithms in patients with motor-eloquent high-grade glioma, combined with nTMS mapping-based region of interest (ROI) placement. The results were compared based on the coverage of nTMS motor maps, revealing reconstruction of the corticospinal tract (CST) with significantly higher volume and better coverage of the eloquent motor cortex for MLFT.
Immediate changes in graph metrics following MRgFUS - an investigation using state-of-the-art diffusion image analysis
Authors: D'Souza Arkiev , Calamante Fernando , Kyle Kain , Tisch Stephen , Jonker Ben , Barnett Yael , Maamary Joel , Maller Jerome , Garber Justin , Barnett Michael , Wang Chenyu
Published: August 2023

MRgFUS (Magnetic Resonance guided focused ultrasound) is an emerging treatment for tremor. The neuroadaptations that accompany desirable clinical outcomes following treatment are not well understood. Diffusion imaging can non-invasively quantify the structural connectivity between brain regions and may help explain tremor suppression mechanisms. Here, advanced diffusion analysis techniques were used to construct structural connectomes before and immediately after MRgFUS treatment in 27 patients with tremor. Graph theory metrics were measured on baseline and follow-up connectomes and differences between sessions were investigated using paired t-tests. Network density, characteristic path length, global efficiency, degree and strength changed following surgery (p<0.05).
Platform for Real-Time Multiplane Targeting and Monitoring of Minimally-Invasive Image-Guided Prostate Cryoablation Procedures
Authors: Lilieholm Thomas , Moskwa Robert , Ozhinsky Eugene , Woodrum David , Block Walter , Koepsel Erica Knavel
Published: August 2023

Minimally invasive cryoablation is an effective and safe treatment option for localized low- and intermediate-risk prostate cancers. Precisely placed cryoprobes in cancerous regions of the prostate kill malignant cells by freezing local tissues while being less invasive than prostatectomy, and having a shorter treatment cycle than most radiotherapies. For accurate probe placement, MR-image guidance is often employed, coupled with external probe-guiding apparati. We developed a platform that enables a cohesive workflow to register the probe-guiding apparati, facilitate target selection, select and verify probe trajectory, and monitor the prostate in real-time using multiple planes during probe insertion and cryoablation freeze cycles.
A privacy-preserving federated learning infrastructure for prostate segmentation on T2-Weighted MRI
Authors: Zerka Fadila , Sunoqrot Mohammed , Abrahamsen Bendik , Patsanis Alexandros , Bathen Tone Frost , Elschot Mattijs
Published: August 2023

Accessing medical data is highly protected by law and ethics, making data sharing difficult and time-consuming. Distributed learning in its various forms allows learning from medical data without these data ever leaving the medical institutions. In this study, we evaluate the Flower federated learning framework for prostate segmentation on T2-Weighted MRI. The results show that the Federated learning framework performs comparably to the reference (centralized learning) model.
Efficient, streamline-free white matter tract segmentation for intraoperative diffusion MRI.
Authors: Young Fiona , Hales Patrick , Mancini Laura , Bisdas Sotirios , Micallef Caroline , Yousry Tarek , Clark Christopher , Aquilina Kristian , Clayden Jonathan
Published: August 2023

Tractfinder is an atlas-based approach to segmenting white matter tracts without tractography, in subjects with space-occupying lesions. A shape and orientation prior is combined with fibre orientation distributions in the target data to produce a map of tract location. Results for a given tract can be obtained in a matter of minutes and are comparable to those afforded by clinical tractography. In future, tractfinder could be applied to intraoperative diffusion MRI to aid neuronavigation during brain surgery.
Hybrid 3T 8-channel Receive Array Using a Metamaterial Slab and Companion Loop Elements: Comparison to a Conventional Array
Authors: Rémillard Léo , Maunder Adam , Iyer Ashwin , De Zanche Nicola
Published: August 2023

Metamaterials (MTMs) have been used as passive elements to improve the receive sensitivity in MRI by enhancing the field locally, but not connected directly as receive elements. We present the design and construction of a novel 2D transmission line based MTM employed as a 4-port element combined with an additional 4-element coil array. Simulation and measurement of receive sensitivity are compared to those of a conventional 8-element coil array covering the same region. The receive sensitivity in a human torso sized phantom is found to be equivalent, while the MTM slab additionally enhances the transmit performance.
Coupling study between two concentric whole-body MRI birdcage coils: towards a whole-body X-nucleus coil
Authors: Heredia Juan Diego Sánchez , Wang Wenjun , Zhurbenko Vitaliy , Ardenkjær-Larsen Jan Henrik
Published: August 2023

The feasibility of integrating a whole-body X-nucleus birdcage in a wide-bore clinical 3T MR scanner is evaluated. The challenge is that this extension coil has to be tightly fit into the scanner bore, having a diameter just 16 mm smaller than the concentric 1H coil. Different configurations are proposed and evaluated with the purpose of minimizing interaction between the X-nucleus coil and the native 1H body coil of the scanner. Experimental results are in agreement with simulations and demonstrate a 1H coil detuning of 0.4 MHz due to co-integration with X-nucleus birdcage.
Multiresolution MR elastography reconstruction and comparison of different direct inversion algorithms in the liver
Authors: Pagé Gwenaël , Juléa Félicia , Paradis Valérie , Vilgrain Valérie , Valla Dominique , Van Beers Bernard , Garteiser Philippe
Published: August 2023

In this study we propose using a MR elastography reconstruction method adjust the ratio between wavelength and spatial resolution, by resampling the matrix of shear displacement locally, to optimize the quality of the reconstruction. This reconstruction algorithm was compared to existing direct inversion algorithms in phantoms, healthy volunteers and patients with liver fibrosis. We observed that the algorithm k-MDEV showing the best performance in phantoms and patients did not have the best repeatability. Our proposed method improved the diagnostic performance for advanced fibrosis, compared to classical direct inversion method, without a negative effect on repeatability.
Flexible Receive Array of Parallel-Resonance High-Impedance Coaxial Coils for 13C Imaging
Authors: Zhurbenko Vitaliy , Heredia Juan Diego Sanchez , Wang Wenjun , Ardenkjær-Larsen Jan Henrik
Published: August 2023

Self-resonant coils are well suitable for flexible array design. The size of such coils is dictated by the RF signal wavelength, which makes the design challenging at low frequencies. In this work, 13C tuning is achieved by combining distributed and lumped capacitance with the self-inductance of an RG-178 coaxial cable. A 1H trap is moved from the coil to the board of the preamplifier for better coil flexibility. The active 13C decoupling circuit is compact and broadband. The approach is used to develop a flexible 8-channel receive array of parallel-resonance coils for 13C-imaging. The array elements exhibit low noise correlation.
Evaluating iron overload in Nigrosome 1 via Quantitative Susceptibility Mapping at 7T in prodromal stages of Parkinson’s disease
Authors: Lancione Marta , Donatelli Graziella , Prete Eleonora Del , Campese Nicole , Frosini Daniela , Cencini Matteo , Costagli Mauro , Lucchi Giacomo , Tosetti Michela , Godani Massimiliano , Arnaldi Dario , Terzaghi Michele , Pacchetti Claudio , Cortelli Pietro , Bonanni Enrica , Ceravolo Roberto , Cosottini Mirco
Published: August 2023

iRBD is a prodromal stage of α-synucleinopathies, like PD. Iron deposition is increased in the substantia nigra of PD patients, mainly in Nigrosome-1 (N1). Here, we estimated N1 iron content in PD, iRBD patients and healthy controls using QSM at 7T to investigate group differences and correlation with disease duration. PD patients showed increased N1 susceptibility compared to controls and iRBD patients but no correlation with disease duration. N1 susceptibility in iRBD patients was not different from controls but correlated with disease duration. Hence, in prodromal stages of α-synucleinopathies, QSM can reveal progressive N1 iron accumulation as the disease evolves.
Diffusion MRI Connectometry with Motor and Cognitive Deficits of Pedunculopontine Nucleus Cholinergic Projections in Parkinson’s Disease
Authors: Seow Pohchoo , Shih Yao-Chia , Hartono Septian , Lee Weiling , Chong Say Lee , Chen Celeste Yan Teng , Tan Eng King , Chan Ling Ling
Published: August 2023

Altered brain cholinergic activity has gained attention in Parkinson’s disease (PD). However, the effects of cholinergic dysregulation on motor and cognitive functions remain unclear. This is partly contributed by the limited capability of conventional MRI techniques to detect microstructural changes in the deep brain. We evaluated the cholinergic projections in 36 PD patients and 58 asymptomatic healthy controls using diffusion MRI connectometry. Local diffusion changes in the cholinergic projections showed significant correlations to motor onset, and clinical motor scores in PD compared to control subjects. Our results suggest underlying neuronal inflammation and compensatory mechanisms in early PD-related neural dysfunction.
Isotropic resolution volumetric liver T2 mapping using a free-breathing navigator-gated radial stack-of-stars T2-prepared Dixon acquisition
Authors: Zamskiy Mark , Weiss Kilian , Harder Felix , Ruschke Stefan , Makowski Marcus , Braren Rickmer , Karampinos Dimitrios
Published: August 2023

Volumetric liver T2-mapping is of interest in the characterization of focal lesions and diffuse disease but remains technically challenging due to respiratory motion. The present work introduces a novel T2-prepared (T2prep) radial stack-of-stars two-point Dixon gradient echo sequence (T2prep-SoS-Dixon-TFE) for achieving motion-robust 3D isotropic T2-mapping in navigator-gated scans using a B0/B1-insusceptible modified adiabatic BIR-4 RF-pulse for T2prep. T2-mapping is performed via dictionary matching to Bloch simulations for the Dixon-decomposed water signal. The proposed method enables motion-robust liver fat confounder-free volumetric T2 quantification in better agreement with MRS compared to GraSE and may improve the clinical applicability of free-breathing abdominal T2-mapping.
Anisotropy of T2 and T1ρ Relaxation in Bovine Articular Cartilage at 3 T
Authors: Kantola Ville , Karjalainen Jouni , Jaakola Tomi , Leskinen Henri , Nissi Mikko , Nieminen Miika , Casula Victor
Published: August 2023

Multiple studies have investigated the orientation dependence of T2 and T1ρ relaxation in articular cartilage using ultra-high field magnets. This study aims to replicate these findings in a clinical measurement setting, performing a series of measurements at multiple orientations on a 3 T clinical scanner using large ex vivo joint samples. Function of a previously suggested relaxation model was confirmed in a low field-strength environment. Anisotropic components of T2 and T1ρ relaxation varied widely depending on the measured parameter, the spin-lock frequency, the magnetization preparation used for the spin-lock experiment (continuous wave/adiabatic), and the considered cartilage layer (superficial/deep half).
Clinical assessment of the degenerative lumbar osseous morphology using zero echo time magnetic resonance imaging (ZTE-MRI)
Authors: Bowen Hou , Liu Chanyuan , Li Yitong , Xiong Yan , Wang Jingyi , Liu Weiyin , Li Xiaoming
Published: August 2023

Lumbar degenerative disease increases with age and is common in the elderly population. The symptoms caused by the osseous degeneration affect the quality of life. Zero echo time (ZTE) sequence could capture and reveal short-T2 materials, allowing to obtain osseous information without ionizing radiation. The ZTE performed similarly to multi-slice computed tomography (MSCT) on the ordinal variables and most measurements of osseous spine. ZTE-MRI could offer more cortical bone details than conventional MRI images and might be a valid alternative to CT for assessment of lumbar osseous morphology to some extent.
Evaluation of Placenta Oxygenation and Perfusion in A Rat Model of Fetal Growth Restriction Using Quantitative T2* Mapping and 3D DCE-MRI
Authors: Darwish Fatimah Al , Coolen Bram , Terstappen Fieke , van Kammen Caren , Alles Lindy , Schiffelers Raymond , lely Titia , Strijkers Gustav
Published: August 2023

Developing preclinical imaging techniques in the field of preeclampsia is essential to test the effectiveness of new therapeutic approaches. We applied T2* weighted and three-dimensional dynamic contrast-enhanced MRI in a pregnant rat model of reduced uterine perfusion pressure (RUPP) to test their feasibility and ability to detect differences in placental oxygenation and perfusion in RUPP rats compared to control. These techniques produced high-quality data that enabled the assessment of oxygenation and perfusion parameters. Oxygenation was decreased in RUPP placenta; however, perfusion parameters did not reveal differences, which requires further investigations.
B0 field distortions monitoring and correction for 3D non-Cartesian fMRI acquisitions using a field camera: Application to 3D-SPARKLING at 7T
Authors: Amor Zaineb , G.R. Chaithya , Le Ster Caroline , Daval-Frérot Guillaume , Boulant Nicolas , Mauconduit Franck , Mirkes Christian , Ciuciu Philippe , Vignaud Alexandre
Published: August 2023

The benefit of retrospective correction of static and dynamic $$$B_{0}$$$ field imperfections was studied on non-Cartesian compressed sensing-based acquisition patterns by taking as an example 3D-SPARKLING encoding scheme. Long-TR dynamic acquisitions of T2*-weighted MRI (fMRI-like) volumes were acquired at 7T, retrospectively corrected, and the evaluation of the corrections was based on the image quality and the gain in temporal signal-to-noise ratio (tSNR). We found that correcting for the static and dynamic $$$0^{th}$$$ order contributions is enough to enhance the image quality and tSNR significantly (up to 22% gain in median tSNR).
Reusable 3D Printed Ex-vivo Brain Enclosure and Two-Piece Cutting Guide for Axial and Coronal MRI Registration with Gross Anatomy Photographs
Authors: Berardinelli Jacob , Kofler Julia , Schweitzer Noah , Farhat Nadim , Santini Tales , Sajewski Andrea , Mettenburg Joseph , Ikonomovic Milos , Aizenstein Howard , Ibrahim Tamer
Published: August 2023

A 3D printed re-usable box enclosure and two-piece cutting guide were developed to produce high quality 7T MR images that can be easily registered to gross anatomy and histology. Cuts can be made parallel or at multiple angles at 5mm intervals in both the axial and coronal orientations.
The Larmor Frequency of a White Matter Magnetic Microstructure Model with Multiple Sources
Authors: Sandgaard Anders , Kiselev Valerij , Shemesh Noam , Jespersen Sune
Published: August 2023

Mapping tissue magnetic properties with MRI may improve the diagnosis of diseases and enhance our understanding of their basic mechanisms. However, MRI signals are sensitive to both structure and magnetic susceptibility, the so-called “magnetic microstructure”, rendering accurate susceptibility estimation a great challenge. Here, we present an analytical expression for the Larmor frequency of a white matter model of myelinated axons with axially symmetric microscopic susceptibility anisotropy and orientation dispersion. The modelled axons are surrounded by microscopic spherical inclusions with a scalar susceptibility. This goes beyond previous models of white matter magnetic microstructure.
Linking functional and structural brain organisation with behaviour in healthy adults
Authors: Forde Natalie , Llera Alberto , Buitelaar Jan , Beckmann Christian
Published: August 2023

Understanding brain-behaviour correlates is challenging. Multimodal approaches increase the sensitivity to brain-behaviour relationships. Here we integrated grey matter density maps, structural connectivity metrics and functional connectopic (gradient) maps from 676 participants of the HCP, with the hypothesis that these more advanced measures of both structural and functional organisation would improve sensitivity to brain-behaviour associations. Our results show 1 component significantly associated with various behavioural measures including multiple measures of alcohol use. This component was composed of structural modalities. There was little shared variance between structural measures and functional gradients across the components.
Structural disconnections in brain tumours: investigating the similarity of Direct and Indirect Approaches
Authors: Villani Umberto , Silvestri Erica , Moretto Manuela , Colpo Maria , Salvalaggio Alessandro , Corbetta Maurizio , Cecchin Diego , Bertoldo Alessandra
Published: August 2023

Gliomas are amongst the most common primary brain tumours in adults and are often associated with poor prognosis. Understanding the extent of white matter (WM) which is affected outside the tumoral lesion may be of paramount importance to explain cognitive deficits and the clinical progression of the disease. Thus, we apply both direct (i.e., tractography based) and indirect (i.e., atlas based) approaches to quantifying WM structural disconnections in a cohort of 50 glioma patients. We eventually compare the disconnections maps provided by the two methodologies in terms of spatial similarity and discuss their critical use in this field.
Investigating complex-valued neural networks applied to phase-cycled bSSFP for multi-parametric quantitative tissue characterization
Authors: Birk Florian , Steiglechner Julius , Scheffler Klaus , Heule Rahel
Published: August 2023

The bSSFP sequence is highly sensitive to relaxation parameters, tissue microstructure, and off-resonance frequencies, which has recently been shown to enable multi-parametric tissue characterization in the human brain using real-valued NNs. In this work, a new approach based on complex-valued NNs for voxel-wise simultaneous multi-parametric quantitative mapping with phase-cycled bSSFP input data is presented, possibly facilitating data handling. Relaxometry parameters (T1, T2) and field map estimates (B1+, ΔB0) could be quantified with high robustness and accuracy. The quantitative results were compared for different activation functions, favoring phase-sensitive implementations.
B1+ Correction for 7T FID-CRT-MRSI
Authors: Lazen Philipp , Strasser Bernhard , Cadrien Cornelius , Sharma Sukrit , Hingerl Lukas , Niess Eva , Motyka Stanislav , Lipka Alexandra , Spurny-Dworak Benjamin , Brandner Christoph , Gruber Stephan , Bogner Wolfgang , Lanzenberger Rupert , Rössler Karl , Trattnig Siegfried , Hangel Gilbert
Published: August 2023

We implemented B1+ correction for our metabolite concentration estimation and analyzed the influence of B1+ inhomogeneities. Since the B1+ field is relatively homogeneous in the center of the brain anyways, the biggest effects were observed closer to the fringes of the brain. The concentration estimates increased between 1.0% and 5.6% for different metabolites when comparing B1+ correction to simple T1 correction, remaining within the spectrum of values established by previous literature.
Preliminary development of a Magnetic Resonance Fingerprinting framework for fast multiparametric low-field NMR relaxometry
Authors: Spinelli Giovanni Vito , Brizi Leonardo , Barbieri Marco , Zama Fabiana , Landi Germana , Bortolotti Villiam , Remondini Daniel , Testa Claudia
Published: August 2023

A novel application of Magnetic Resonance Fingerprinting (MRF) on low-field NMR is presented. To successfully implement MRF, the correlation between the static and the radio-frequency fields has to be measured, because the evolution of the signal cannot be analyzed without accounting for magnetic fields inhomogeneities. Experimental results have been validated by simulations and compared using the RMSE. This preparatory evaluation allows the use of MRF for NMR parameters quantification. Then, an artificial intelligence approach for parameters reconstruction has been used to overcome the limitation of the standard dictionary approaches when several parameters have to be estimated.
The combined use of MEGA- editing and asymmetric-PRESS methods improve the precision of cerebral lactate detection in healthy adults
Authors: Jugé Lauriane , Ball Iain , Rae Caroline
Published: August 2023

Here, we combined two 1H-MRS methods that have shown utility for detecting lactate in the brain, MEGA- editing and use of an asymmetric-PRESS and compared this approach (MEGA-APRESS) with MEGA-PRESS and A-PRESS in phantoms and eight individuals. MEGA-APRESS showed improved precision compared to MEGA-PRESS. Both editing approaches were greatly superior to A-PRESS alone.
Advancing Concussion Assessment in Pediatrics (A-CAP): Longitudinal changes in brain metabolites in pediatric concussion
Authors: La Parker , Harris Ashley , Walker Robyn , Joyce Julie , Bell Tiffany , Craig William , Doan Quynh , Beauchamp Miriam , Zemek Roger , (PERC) Pediatric Emergency Research Canada , Yeates Keith , Harris Ashley
Published: August 2023

Disruptions in brain metabolites following concussion are commonly reported in the literature. However, studies have typically included only one timepoint, studied adults and/or had limited sample size. In the largest MRS dataset in pediatric concussion to date, we show that metabolites do not differ significantly over time points with longitudinal data collected sub-acutely (<14 days post-injury) and at 3- or 6-months follow-up. This lack of change may indicate that metabolites are relatively stable, that changes are regionally specific or occur more acutely, or there are subgroups that need to be specifically considered.
Performance Analysis of Undersampling Strategies for Multi-Shell Diffusion MRI
Authors: Aygun Elif , Saritas Emine Ulku
Published: August 2023

Multi-shell dMRI metrics quantify information on micro-properties of neural tissue and can be used as markers for neurological diseases. The protocols used to acquire dMRI data often have prolonged acquisition times. In this work, we propose different undersampling strategies that reduce the acquisition time to half, and evaluate how the performances of multi-shell dMRI metrics change under these strategies. The results show that, while the best performing strategy changes for each metric, 3-shell gradient schemes with small variance of b-vector density on consecutive shells demonstrate improved performance. Additionally, more complex dMRI metrics exhibit relatively increased sensitivity to undersampling.
Nanoscopic materials for quantitative water exchange phantoms
Authors: Swanson Scott , Malyarenko Dariya , Chenevert Thomas
Published: August 2023

Nanoparticle lipid vesicles are developed with controllable water exchange to provide a ground-truth benchmark for MR methods which measure exchange. Diffusion data are collected as a function of diffusion delay Δ. An exchange time, τ, is measured to be 164 ms in a phantom with a highly fluid membrane. These materials should help to clarify water dynamics in complex systems.
Understanding inhomogeneous MT (ihMT) in multi-parameter mapping of human brain: Towards larger ihMT, higher resolution, and influence of T1d
Authors: Helms Gunther , Vaculčiaková Lenka , Pine Kerrin , Möller Harald , Weiskopf Nikolaus
Published: August 2023

Inhomogenous Magnetization Transfer (ihMT), the differential response to irradiation at single and dual frequency offsets, is more complex than MT approaches. Expressing ihMT in terms of MT-saturation (ihMTsat) is a first step to quantification as it corrects for underlying T1 and B1+. Larger ihMTsat was observed for smaller frequency offsets, which is explained using MTsat as proxy for bound pool saturation. For longer TR, ihMTsat increased faster than MTsat indicating recovery of dipolar order as ihMTsat increased super-linearly to 1.1pu in WM and 0.2pu in GM at TR=52ms. ihMTsat mapping in vivo was performed at 1.3mm isotropic resolution.
Acquisition optimization for cortical ihMTsat imaging
Authors: Rowley Christopher , Leppert Ilana , Campbell Jennifer , Pike G , Tardif Christine
Published: August 2023

Sequence simulations are used to compare different conventional and boosted saturation schemes and imaging protocols for the purpose of high-resolution ihMTsat cortical imaging. The simulations are constrained to a maximum of four minutes per volume. We find an optimal region for conventional saturation that produces the greatest ihMTsat. For the boosted approach, larger ihMTsat values are found with respect to the conventional approach, and ihMTsat increases with longer TRs. However, the practical utility of the boosted approach for cortical imaging is hampered by a wider PSF associated with higher turbo factors. Simulated ihMTsat findings are supported by in vivo data.
Simultaneous imaging of positive and negative chemical exchange contrast: On the implementation of the RACETE-technique on a clinical 3T-system
Authors: Schirmer Verena , Gram Maximilian , Albertova Petra , Mayer Simon , Blaimer Martin , Jakob Peter Michael , Gutjahr Fabian Tobias
Published: August 2023

Contrary to the basic principle of CEST, the RACETE technique allows for the direct detection of positive chemical exchange contrast. This method, which was previously demonstrated only under ultra-high field conditions at 7T-17.5T, has now successfully been implemented on a clinical 3T scanner in initial phantom experiments. Furthermore, we present a novel dual-contrast RACETE-technique for simultaneous imaging of the positive RACETE and the negative CEST contrast.
Microscopically Anisotropic and Randomly Oriented 3D Printed MRI Phantom for Size, Orientation, and Anisotropy Validation in Diffusion Imaging
Authors: Witherspoon Velencia , Komlosh Michal , Benjamini Dan , Basser Peter , Lavrik Nick
Published: August 2023

Microscopically anisotropic but globally isotropic DTI MRI phantom was designed and fabricated using a 2 Photon Nanoscribe 3D Printer. The capillary array blocks were measured aligned and randomly oriented to determine the ability of ddPFG and DTI to characterize local anisotropy in a globally isotropic system. These experiments combined computational methods can provide MRI phantoms that can be employed to validate novel or proposed microstructure imaging experiments.
Soy lecithin: a phantom material for the adjustment of apparent diffusion coefficient in magnetic resonance imaging
Authors: Fritz Victor , Martirosian Petros , Machann Jürgen , Schick Fritz
Published: August 2023

The aim of this work was to systematically investigate whether lecithin is suitable for the construction of a diffusion phantom that covers and simulates ADC-values occurring in human tissue. For this, aqueous solutions of different lecithin concentrations (0%-10%) were prepared and measured by DWI. The presented results showed that lecithin is a suitable agent for simulating a wide variety of ADC-values. Even low concentrations showed a strong decrease in the ADC-value of water. However, with increasing concentration, lecithin also showed a strong influence on T2, so that ADC and T2 cannot be set independently from one another in lecithin-based phantoms.
ACUTE CAFFEINE ADMINISTRATION AS A CONFOUND FOR q-MRI and volumetric MRI STUDIES
Authors: Sumra Vishaal , Chavez Sofia
Published: August 2023

Changes in cerebral blood flow (CBF) have the ability to confound structural and quantitative MRI studies. Caffeine is widely consumed and leads to strong decreases in CBF. Moderate caffeine users were scanned before and after caffeinated and decaffeinated coffee over two separate days. Percentage change in CBF maps, quantitative T1 maps, and estimates of grey matter volume (GMV) were assessed for the caffeinated coffee and decaffeinated coffee days. Robust decreases in CBF were observed, along with changes in T1 maps and estimates of GMV. Caffeine intake should be considered in studies relying on structural and quantitative MRI measures.
Qualitative and Quantitative Imaging Phenotypes can Predict CDKN2A/B Homozygous Deletion Status in IDH-mutant Astrocytomas
Authors: Park Yae Won , Park Ki Sung , Ahn Sung Soo , Park Inho , Kim Se Hoon
Published: August 2023

CDKN2A/B homozygous deletion is a key molecular marker in the 2021 WHO classification of IDH-mutant astrocytomas; presence of CDKN2A/B homozygous deletion results in a grade of 4. On multivariable analysis, infiltrative pattern, larger tumor volume, and higher 95th percentile of nCBV were independent predictors of CDKN2A/B homozygous deletion. The infiltrative pattern and larger volume may be reflected from the increased tumor cell proliferation, whereas the higher 95th percentile of nCBV may reflect the increased angiogenesis due to CDKN2A/B homozygous deletion.
Dynamic Contrast Enhanced MR Wavelet-Based Radiomics Analysis for Characterization of Tumor Heterogeneity of Rat Brain Tumors
Authors: Bagher-Ebadian Hassan , Brown Stephen , Valadie Olivia , Rey Julian , Sarntinoranont Malisa , Ewing James , Chetty Indrin
Published: August 2023

Wavelet-analysis of DCE-MR images was performed to explore the association between radiomics information and relaxivity-change (ΔR1) in human U251n tumors grown in rat brains. Sixteen DCE-MRI experiments (8 rats before- and after- radiation) were studied. Wavelet-decomposition analysis was performed using ΔR1 time trace. Frequency-based localized approximations of ΔR1 with four degrees of regularities were estimated and compared to the volume-transfer-constant (Ktrans, calculated from a modified Tofts-model pharmacokinetic analysis). Results confirm strong associations between wavelet-based radiomic information and contrast uptake/flow/leakage in the tumor vasculature. Results suggest that radiomics has potential as a biomarker of tumor physiology.
Development of USPIO-DM1-5D3-CF750: An image-guided targeted drug delivery system for prostate cancer therapy
Authors: Hapuarachchige Sudath , Si Ge , Foss Catherine , Barinka Cyril , Artemov Dmitri
Published: August 2023

Prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancers (PC) compared to normal tissues. Hence, PSMA can be used as a diagnostic biomarker and biological target to deliver drugs in PC therapy. In this study, we have conjugated ultra-small superparamagnetic iron oxide nanoparticles with mertansine (DM1), a chemotherapeutic drug, novel anti-PSMA 5D3 antibody, and NIR CF-750 fluorophore. This multimodality image-guided drug delivery system was evaluated in PC mouse models using in vivo fluorescent imaging and MRI at 9.4T. Promising results encourage further development of targeted image-guided drug delivery platforms for PC therapy.
ALFONSO: A versatiLe Formulation fOr N-dimensional Signal mOdel fitting of MR spectroscopy data and its application in MRS of body lipids
Authors: Ruschke Stefan , Karampinos Dimitrios
Published: August 2023

Multi-dimensional MR spectroscopy is frequently used for the probing of MR properties including the characterization of the water–fat environment in body applications. Previously, many studies used an ad-hoc multi-step approach where the fitting of the spectral content and the signal modelling was performed in separate steps albeit the theoretically compromised precision when compared to a joint fitting and modelling approach. ALFONSO allows the convenient and yet flexible definition of joint fitting and modelling strategies. Its utility and supremacy are demonstrated for the quantification of fat fraction in the liver, ADC in bone marrow and lipid droplet size in a phantom
Test-retest repeatability of radiomic features derived from T2w MRI in prostate cancer patients
Authors: Wichtmann Barbara , Albert Steffen , Santos Daniel Pinto dos , Attenberger Ulrike , Baessler Bettina
Published: August 2023

Radiomics enables the extraction of quantitative features from medical images, potentially augmenting the characterization of healthy and diseased tissue. Before these features can be routinely used as biomarkers in clinical practice, however, their repeatability and reproducibility must be ensured. This study seeks to investigate feature repeatability in an in-vivo, clinical test-retest dataset of prostate cancer patients. Our results show that the majority (71.8%) of radiomic features extracted from in-vivo, clinical T2-weighted images was not repeatable, emphasizing the need for repeatability and reproducibility studies.