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Rita G Nunes
University of Lisbon, Portugal
Abstract: Diffusion Magnetic Resonance Imaging (dMRI) has become an essential tool both in research and in the clinic, taking advantage of the random motion of water molecules to probe tissue organization at a scale much finer than the achievable image spatial resolution. Although many clinic applications still rely on the basic quantification of the average diffusion coefficient or on mapping the main diffusion orientation with Diffusion Tensor Imaging, this research field has seen many developments since dMRI was first introduced. In this talk I will review some recent research efforts to address the limitations of basic dMRI, focusing on potential applications and ongoing challenges.
MichalRafal Zareba1,2, Magdalena Fafrowicz3, Tadeusz Marek3, Ewa Beldzik3, Halszka Oginska3, Aleksandra Domagalik2
1Faculty of Biology, Jagiellonian University, Kraków, Poland
2Malopolska Centre of Biotechnology, Jagiellonian University, Kraków, Poland
3Institute of Applied Psychology, Jagiellonian University, Kraków, Poland
Abstract: In recent decades magnetic resonance imaging (MRI) has established itself as the goldenvstandard for studying human brain structure and it has become increasingly more important to identify factors that may influence study outcomes and contribute to misleading conclusions. With the regional time-of-day (TOD) differences in structural brain metrics heavily neglected, this work set out to investigate this phenomenon with voxel-based (VBM) and surface-based morphometry (SBM) using the largest longitudinal dataset to date (N = 72). VBM revealedubiquitous and often bilaterally symmetric differences in local grey and white matter volume across multiple areas. The impact of TOD on regional SBM indices was less pronounced. After inclusion of image quality metrics in the models, however, the significant TOD findings were drastically limited. These results suggest that while TOD effect might be present in some regions of the brain, it is image quality that has a much more pronounced impact on experimental results. Nevertheless, both factors should be strictly controlled to prevent false positive findings in longitudinal MRI studies.
Dominika Ciupek1, Tomasz Pięciak2
1AGH University of Science and Technology, Kraków, Poland
2LPI, ETSI Telecomunicación, Universidad de Valladolid, Valladolid, Spain
Abstract: Diffusion magnetic resonance imaging is a non-invasive tool depicting directional properties of water diffusion in fibrous tissues such as the brain white matter (WM). The diffusion tractography, a numerical procedure, allows tracking these anisotropic features of the brain and combining them into the trajectories illustrating distant brain regions linkage. As the human brain systematically changes across the lifespan, measuring these connectivity-based alterations becomes an exciting challenge both from neuroscience and clinical views. This work studies the along-track variations and diffusion properties alterations of WM connections due to brain aging based on standard diffusion tensor imaging. The population study aggregates the group of healthy subjects (31F/31M, aged 8-75) scanned with the Connectome 3T Siemens and delivered with the Human Connectome Project. We observe the U-shape mean diffusion properties trajectories of the tract with a rapid elevation (+16.57% for FA) or decline (-13.40% for MD) during adolescence and early adulthood, and a gradual decline (-17.83% for FA) or increment (+12.87% for MD) respectively in adulthood with region-dependent peak between 20y and 35y. Our results suggest that the underlying brain aging-related processes (demyelination or axonal loss) affect brain pathways spatially different and under varying changing rates across the lifespan.
Funding:Dominika Ciupek acknowledges the AGH University of Science and Technology for the grant 78/GRANT/2022. Tomasz Pięciak acknowledges the Polish National Agency for Academic Exchange for grant PPN/BEK/2019/1/00421 under the Bekker programme and the Ministry of Science and Higher Education (Poland) under the scholarship for outstanding young scientists (692/STYP/13/2018). This research was supported by PLGrid Infrastructure (CYFRONET Academic Computer Centre, Kraków, Poland).
Marcin Sińczuk1,Jacek Rogala2, Nikodem Hryniewicz1, Ewa Piątkowska-Janko1,3, Piotr Bogorodzki
1Nalecz Institute of Biocybernetics and Biomedical Engineering PAS, Warsaw, Poland
2Nencki Institute of Experimental Biology PAS, Warsaw, Poland
3The Institute of Radioelectronics and Multimedia Technology, WEITI, Warsaw, Poland
Abstract: In a typical PRESS (Point RESolved Spectroscopy) sequence the water signal is suppressed to allow for metabolite peak quantification. On the other hand, water peak parameters are useful in further metabolite quantification or other specific studies like MR thermometry. Our study compared temperature estimates from two MR spectra with either suppressed or unsuppressed water peaks. We investigated how suppression pulses influence temperature estimates and whether suppressed or unsuppressed water peaks should be used in future MRS thermometry studies. Six calibration datasets were acquired from the phantom. Each uses suppressed and unsuppressed water peaks in conjunction with metabolites: NAA, Creatine, and Choline. In vivo data was acquired from 169 healthy adult subjects with PRESS sequence. Two spectra were acquired from each subject: One before 30 minute fMRI study and one after. Mean brain temperatures (in vivo) showed similar significant negative changes between pre and post-fMRI sessions. Comparisons reveal that unsuppressed water data yields higher temperatures and higher deviations overall than suppressed water data. We believe that using suppressed water peak data (where water peak is still visible) is preferable but it is also feasible to use spectra with unsuppressed water peak in conjunction with metabolites from highly suppressed spectral data.
Funding:This study was part of the grant NCBR nr POIR.01.01.01-00-0178/15-00
Alaa Alghanimy, Conor Martin, Lindsay Gallagher, William M. Holmes
Glasgow Experimental MRI Centre (GEMRIC), Institute of Neuroscience and Psychology, University of Glasgow
Abstract: The glymphatic system is a low resistance pathway, by which cerebrospinal fluid enters the brain parenchyma along perivascular spaces via AQP4 channels. It is hypothesised that the resulting convective flow of the interstitial fluid provides an efficient mechanism for the removal of waste toxins from the brain. Therefore, enhancing AQP4 function may protect against neurodegenerative diseases such as Alzheimer’s disease, in which the accumulation of harmful proteins and solutes is a hallmark feature. To this day, there have been no proven treatments to enhance the elimination of pathogenic proteins. Here, we test the effect of an AQP4 facilitator, TGN-073, on glymphatic transport in a normal rat brain by employing different MRI techniques. Surgical procedures were undertaken to catheterise the cisterna magna, thereby enabling infusion of an MRI tracer (Gd-DTPA). Before tracer infusion, either TGN-073 or the vehicle were given via intraperitoneal injection. Dynamic 3D T1 weighted imaging of glymphatic transport was undertaken over two hours. Further, the apparent diffusion coefficient was measured in different brain regions using diffusion-weighted imaging. We found that rats treated with TGN-073 showed the distribution of Gd-DTPA was more extensive and parenchymal uptake was higher compared with the vehicle group. Water diffusivity was increased in the brain of TGN-073 treated group, which indicates greater water flux. Our results indicate that compounds such as TGN-073 can improve glymphatic transport in the brain. Since glymphatic impairment due to AQP4 dysfunction is potentially associated with several neurological disorders such as Alzheimer’s disease, dementia and traumatic brain injury, enhancing AQP4 functionality is a promising future therapeutic target.
