Tobias C Wood¹ and Nikou Louise Damestani^1
1Neuroimaging, King's College London, London, United Kingdom

We demonstrate a proof-of-concept fMRI experiment using a BOLD-insensitive MT-prepared ZTE pulse sequence, which exploits the recently proposed Arterial Blood Contrast mechanism. We show tightly localised responses to a visual checkerboard task in a small number of subjects.

Sooyeon Ji¹, Eun-Jung Choi¹, Eung Yeop Kim², Dong Hoon Shin³, Hyeong-Geol Shin¹, and Jongho Lee^1
1Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea, Republic of, ²Department of Radiology, Gachon University Gil Medical Center, Incheon, Korea, Republic of, ³Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea, Republic of

A neuromelanin-sensitive imaging protocol based on a GRE sequence, sandwich-fsNM, is developed using multiple flow saturation pulses instead of MT pulses. The flow saturation pulses are located both superior and inferior to the imaging volume, like a sandwich, to avoid asymmetric MT across slices. The proposed protocol yields higher contrast between crus cerebri and substantia nigra and better visualizes locus coeruleus, compared to MT prepared GRE or TSE sequences.

Fábio Seiji Otsuka¹, Carlos Salmon¹, Otaciro Nasimento², and Maria Otaduy^3
1Physics Department, University of São Paulo, Ribeirão Preto, Brazil, ²Physics Institute, University of São Paulo, São Carlos, Brazil, ³Medical School, University of São Paulo, São Paulo, Brazil

On this work it was evaluated the EPR measurements at variable temperature on tissue samples from different brain regions. For all samples, four different peaks were observed and their relationship with temperature were analyzed. High-spin rhombic iron(g = 4.3), copper(g = 2.06, g = 2.28) and organic radical (g = 1.989) peaks showed a Curie behavior with antiferromagnetic contributions. By other hand, a broad peak centered at g = 2.0 showed an antiferromagnetic behavior with Curie contribution. Additionally, a fifth peak was observed only for the Locus Coeruleus sample with a temperature dependent g-value (3.62 - 2.55).

Caroline Le Ster¹, Franck Mauconduit¹, Christian Mirkes², Michel Bottlaender^3,4, Fawzi Boumezbeur¹, Boucif Djemai¹, Alexandre Vignaud¹, and Nicolas Boulant^1
1Paris-Saclay University, CEA, CNRS, BAOBAB, Neurospin, Gif-sur-Yvette, France, ²Skope MRT, Zurich, Switzerland, ³Paris-Saclay University, CEA, CNRS, INSERM, BioMaps, Service hospitalier Joliot, Orsay, France, ⁴UNIACT, Neurospin, CEA, Gif-sur-Yvette, France

An MR thermometry (MRT) method with field monitoring is proposed to improve the measurement of small temperature variations occurring in head MRI exams. MRT experiments were performed at 7T with concurrent radiofrequency heating and field monitoring on an agar-gel phantom and on an anaesthetized macaque. Inclusion of field fluctuations in image reconstruction showed beneficial for the measurement of small temperature rises as encountered in standard brain exams. 

Mert Şişman¹, Mehdi Sadighi¹, Hasan Hüseyin Eroğlu^2,3, and B. Murat Eyüboğlu^1
1Electrical and Electronics Engineering, Middle East Technical University (METU), Ankara, Turkey, ²Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Amager and Hvidovre, Denmark, ³Center for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs Lyngby, Denmark

Magnetohydrodynamic (MHD) flow occurs due to the Lorentz force formed by the interaction between the static magnetic field of the MR scanner and the externally injected electric current. The MR based imaging of MHD flow has become a research field of interest recently. The MHD flow can be extracted from the MR phase images obtained using a pulse sequence with flow-encoding gradients. In this study, the MHD flow distributions of a simulated model and a homogeneous experimental phantom are obtained. The MHD velocity contrast images reconstructed using simulated and experimental measurements are consistent.

Mert Şişman¹, Mehdi Sadighi¹, and B. Murat Eyüboğlu^1
1Electrical and Electronics Engineering, Middle East Technical University (METU), Ankara, Turkey

Recently, it is shown that the magnetohydrodynamic (MHD) flow has potential in clinical applications. In addition, diffusion tensor imaging (DTI) is widely used as an exclusive clinical diagnostic method. To obtain the MHD flow velocity distributions in three directions, twelve acquisitions with flow-encoding gradients and external current injection are needed. By choosing flow-encoding directions carefully, it is possible to obtain MHD flow velocity and DT distributions from the MR phase and magnitude images of the same acquisition. In this study, the MHD flow and DT data of an imaging phantom are acquired simultaneously using a spin echo based pulse sequence.

Simone Poli¹, Lia Bally², Roland Wiest³, and Roland Kreis^1
1Department of Radiology and Biomedical Research, University of Bern, Bern, Switzerland, ²Department of Diabetes, Endocrinology, Nutritional Medicine and Metabolism, Inselspital, Bern University Hospital and University of Bern, Bern, CH, Bern, Switzerland, ³Institute of Diagnostic and Interventional Neuroradiology, Inselspital, Bern University Hospital and University of Bern, Bern, CH, Bern, Switzerland

This study aims to analyze the feasibility of indirect detection by ¹H MRS of cerebral metabolism following intake of deuterated glucose in humans on a clinical 7T system. Brain spectra before and after  [6,6’-²H₂]-glucose administration were simulated with realistic SNR and linewidth to evaluate the best achievable precision in quantifying specific deuterated and non-deuterated metabolites. We expect labeling of glutamate, lactate and glutamine to be observable from single spectra of large VOIs, but also in MRSI at resolutions of 2-5 cm³. The simulations were corroborated with phantom data but eventual feasibility will remain to be confirmed in vivo.

Nina Elina Hänninen^1,2, Mikko Johannes Nissi^1,2, Matti Hanni^1,3,4, Olli Gröhn⁵, Miika Tapio Nieminen^1,3,4, and Timo Liimatainen^1,4
1Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland, ²Department of Applied Physics, University of Eastern Finland, Kuopio, Finland, ³Medical Research Center, University of Oulu and Oulu University Hospital, Oulu, Finland, ⁴Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland, ⁵A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland

Relaxation times of tissues can depend on tissue orientation with respect to main magnetic field. However, these effects are still unknown in many biological tissues. Relaxation anisotropy provides a base to develop novel quantitative MRI contrasts and unwrap the theory behind different relaxation mechanisms. We investigated relaxation anisotropy of conventional and rotating frame relaxation parameters in brain, spinal cord, tendon, cartilage, kidney and cardiac muscle tissue. The findings show that relaxation anisotropy varies between relaxation parameters and between different tissue types.

Bart R. Steensma¹, Cornelis A.T. van den Berg¹, and Alexander J.E. Raaijmakers^2
1Center for Image Sciences - Computational Imaging Group, University Medical Center Utrecht, Utrecht, Netherlands, ²Biomedical Engineering - Medical Imaging Analysis, Eindhoven University of Technology, Eindhoven, Netherlands

To validate thermal simulations, high precision in vivo MR thermometry measurements are required. We demonstrate in vivo MR thermometry in the upper leg at 7T, where we improved the precision of our temperature measurements by using cardiac triggering with a PPU. The standard deviation in baseline measurements without RF heating decreased more than two-fold (0.1 ° C with PPU compared to 0.21 ° C without PPU). We were able to perform reproducible MR thermometry measurements in vivo,  with  local  temperature increases of  less than 1 °C. 

Thomas Lindner¹, Hanna Debus¹, and Jens Fiehler^1
1University Hospital Hamburg-Eppendorf, Hamburg, Germany

This study presents an approach to retrospectively remove contrast agent from the final images, denoted as "virtual non-contrast enhanced imaging"

Tristhal Parasram¹, Rongsheng Lu², Yi Chen², and Dan Xiao^1
1University of Windsor, Windsor, ON, Canada, ²Southeast University, Nanjing, China

Magnetic nanoparticles can bind to biomarkers. The particles dispersed in solution become clustered if the targets exist, leading to a different T₂ relaxation time. The relaxation switch mechanism has been applied as a biosensor for various biomarkers. However, the change in relaxation rate is related to the nanoparticle size and concentration. Some theoretical models have been applied to predict this rate of change in search for the optimal system parameters. In this work, an open-source Monte Carlo algorithm has been developed to simulate water diffusion in microscopic environments with nanoparticles and the effective T₂ relaxation times. 

Waqas Majeed¹, Axel J. Krafft², Sunil Patil¹, Henrik Odéen³, John Roberts³, Florian Maier², Dennis L. Parker³, and Himanshu Bhat^1
1Siemens Medical Solutions USA Inc., Malvern, PA, United States, ²Siemens Healthcare GmbH, Erlangen, Germany, ³Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States

Low field MRI offers advantages such as reduced cost and improved safety of implantable and interventional devices, and reduced RF energy deposition over high field alternatives. However, the accuracy of proton resonance frequency (PRF) thermometry suffers at low field due to reduced signal to noise ratio as well as lower temperature-sensitivity of MR phase. In this study we demonstrate that reduced off-resonance effects, increased T2* and shorter T1 associated with low field can be leveraged to achieve high quality MR thermometry in the brain and prostate at 0.55T.

Chang-Sheng Mei¹, Shenyan Zong², and Guofeng Shen^2
1Department of Physics, Soochow University, Taipei, Taiwan, ²Biomedical Instrument Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

The proton resonance frequency (PRF) offset, which is linear to the temperature changes, has been developed and applied for thermal ablation therapies. However, the conventional PRF-based thermometry is limited in temperature measurements of fat due to the absence of hydrogen bonds. In this work, we proposed a revised and retrospective PRF method merged with the nonlinear circle fitting, to detect the accurate phase changes of water for achieving temperature measurements in aqueous and adipose tissues. The in vitro water-bathing heating for phantom and ex vivo focused ultrasound (FUS) heating for swine tissues were performed to verify the proposed method.

Michael Malmberg¹, Dennis L Parker², and Henrik L Odéen^2
1Biomedical Engineering, University of Utah, Salt Lake City, UT, United States, ²Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States

Neglecting the effects of T₂* changes in the single reference variable flip angle (SR-VFA) method for T₁-mapping produces a substantial systematic bias on T₁ that increases with TE, T1 changes, and T₂* changes. These effects were simulated using 1000 noisy signals of a single voxel using the SPGR equation. It was found that the bias can be corrected by measuring T₂* changes dynamically, at the expense of noise, which noise could be mitigated through weighted T₁-map combinations across echo times. Multi-echo T₁-mapping with the SR-VFA method could be combined with PRFS thermometry to allow fast, accurate T₁-mapping of heterogeneous tissue.

Iva VilasBoas-Ribeiro¹, Sergio Curto¹, Gerard C. van Rhoon^1,2, and Margarethus M. Paulides^1,3
1Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands, ²Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands, ³Center for Care and Cure Technologies Eindhoven (C3Te), Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

Proton resonant frequency shift is the most frequently used method for MR-thermometry. This method is sensitive to patient motion which poses issues that affect the MR-thermometry accuracy. Few studies have evaluated MR thermometry in the pelvis, but only in volumes far from the regions with air motion, and without an objective patient data exclusion criteria. In this study, we assessed accuracy of MR thermometry for a selected group of patients with cervical carcinoma. We showed that changing gastrointestinal air volume was an important confounder for MR thermometry accuracy and that this can be exploited for selection criteria prior to treatment.

Henrik Odéen¹, Sara L Johnson¹, Allison H Payne¹, and Dennis L Parker^1
1Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States

Simultaneous PRF/T1 measurements using a single reference variable flip angle method is used to investigate the utility of T1 as a complimentary measure to thermometry for treatment outcome in MR guided thermal interventions, such as focused ultrasound. Both temperature and thermal dose have been shown to be inaccurate indicators of treatment outcome, creating a potential need for alternative quantitative metrics. This can be of particular value in adipose tissues where PRF has very low sensitivity. It is shown that the slope of the T1 vs. temperature curve correlates with amount of delivered thermal dose.

Mitsuki Rikitake¹, Junichi Hata², Fumiko Seki³, Shinsuke Ishigaki⁴, Kuniyuki Iwata-Endo⁴, Nobuyuki Iwade⁴, Takako Shirakawa¹, Hirotaka James Okano², Hideyuki Okano⁵, and Gen Sobue^4
1Department of Redioligical Science, Human Health Science,　Tokyo Metroplitan University, Tokyo, Japan, ²Jikei University Graduate School of Medicine, Tokyo, Japan, ³Central Institute for Experimental Animals, Kanagawa, Japan, ⁴Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan, ⁵RIKEN Center of Brain Science, Saitama, Japan

Symptom of FTLD is known brain atrophy and neurodegeneration predominantly in frontal and temporal lobes.However, the regularity of neurodegeneration and image analysis methods have not been established.The purpose of this study was to conduct multiparametric MRI to analyze the neurodegeneration caused by FTLD using structural MRI and fMRI.We used marmosets, which have a relatively similar brain structure to humans, as the experimental subjects.Statistical imaging analysis using diffusion MRI showed gray matter degeneration was observed, mainly in the caudate nucleus.The fMRI showed decreased brain activity in the frontal lobe and basal ganglia.

Elise Noelle Woodward¹, Matthew S Fox^1,2, Tingting Wu³, Hacene Serrai¹, David G McCormack⁴, Grace Parraga^3,4,5,6, and Alexei Ouriadov^1,2,6
1Physics and Astronomy, Western University, London, ON, Canada, ²Lawson Health Research Centre, London, ON, Canada, ³Department of Medical Biophysics, Western University, London, ON, Canada, ⁴Department of Medicine, Respirology, Western University, London, ON, Canada, ⁵Robarts Research Institute, London, ON, Canada, ⁶School of Biomedical Engineering, Western University, London, ON, Canada

In this study, we demonstrated a possible solution to underestimation of the global mean that can mask the severity of emphysema progression. Four patients with Alpha-1 Anti-Trypsin Deficiency disorder  (AATD) were measured in 2014 using hyperpolarized He to measure lung function, and again in 2018 to measure lung function. While it is evident looking at morphometry images that there is a significant reduction in pixels and therefore emphysema progression, it is not at first evident in morphometry estimates. By normalizing these morphometry estimates of ADC/Lm, we can better characterize emphysema progression in individuals with AATD

Tyler Blazey¹, Galen D Reed², Joel R Garbow¹, and Cornelius von Morze^1
1Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, MO, United States, ²GE Healthcare, Dallas, TX, United States

Hyperpolarization greatly increases the sensitivity of MRI studies of 13C-labeled substances. To expand our ability to investigate in vivo metabolism with hyperpolarized MRI, we developed a metabolite-specific 2D EPI pulse sequence with custom flyback spatially-selective RF pulses for [1-13C]pyruvate and [1-13C]lactate at 4.7T. Spectral profiles for each metabolite obtained using a [13C]urea phantom showed good correspondence with simulated profiles. In vivo testing was performed by imaging the liver and kidney of a rat following the injection of hyperpolarized [1-13C]pyruvate. Both the temporal and spatial resolution of [1-13C]pyruvate and [1-13C]lactate images was higher with our metabolite-specific EPI sequence than with CSI.

Dominik Weidlich¹, Julius Honecker², Claudine Seeliger², Daniela Junker¹, Marcus R. Makowski¹, Hans Hauner², Dimitrios C. Karampinos¹, and Stefan Ruschke^1
1Department of Diagnostic and Interventional Radiology, School of Medicine, Technical University of Munich, Munich, Germany, ²Else Kröner Fresenius Center for Nutritional Medicine, Technical University of Munich, Freising, Germany

A non-invasive method allowing the probing of the relative ω-3 fatty acid content in adipose tissue has the potential to reveal unknown metabolic patterns in physiology and pathology. In the current study, a model-based triglyceride mapping scheme is extended to enable the differentiation between ω-3 and non-ω-3 fatty acids by exploiting additional knowledge about the chemical shift properties. This extended scheme is combined with a chemical shift encoding imaging sequence and evaluated in a phantom validation experiment against gas chromatography–mass spectrometry. Furthermore, feasibility is demonstrated in both in vitro and in vivo settings.