Biology subjects

emir, u.

Publications and source records attributed to emir, u..

4 recordsLinked to original sources

bioRxiv2024

Multi-site Ultrashort Echo Time 3D Phosphorous MRSI repeatability using novel Rosette Trajectory (PETALUTE)

PurposeThis study aims 1) to implement an operator-independent acquisition, reconstruction, and processing pipeline using a novel rosette k-space pattern for UTE 31P 3D MRSI and 2) to evaluate the clinical applicability and replicability at different experimental setups. MethodsA multicenter repeatability study was conducted for the novel UTE 31P 3D Rosette MRSI at three institutions with different experimental setups. Non-localized 31P MRSI data of 5 healthy subjects at each site were acquired with an acquisition delay of 65 s and a final resolution of 10 x 10 x 10 mm3 in 9 min. Spectra were quantified using the LCModel package. The potential acceleration was achieved using compressed sensing on retrospectively undersampled data. Reproducibility at each site was evaluated using the inter-subject coefficient of variance. ResultsThis novel acquisition and advanced processing techniques yielded high-quality spectra and enabled the detection of the critical brain metabolites at three different sites with different hardware specifications. In vivo, feasibility with an acceleration factor of 4 in 6.75 min resulted in a mean Cramer-Rao lower bounds below 20% for PCr, ATPs, PME, and the mean CoV of ATP/PCr resulted in below %20. ConclusionWe demonstrated that UTE 31P 3D Rosette MRSI acquisition, combined with compressed sensing and LCModel analysis, allows patient-friendly, operator-independent, high-resolution 31P MRSI to be acquired at clinical setups.

neuroscience↗

bioRxiv2022

High-Resolution 3D Ultra-Short Echo Time MRI with Rosette k-Space Pattern for Brain Iron Content Mapping

BackgroundThe iron concentration increases during normal brain development and is identified as a risk factor for many neurodegenerative diseases, it is vital to monitor iron content in the brain non-invasively. PurposeThis study aimed to quantify in vivo brain iron concentration with a 3D rosette-based ultra-short echo time (UTE) magnetic resonance imaging (MRI) sequence. MethodsA cylindrical phantom containing nine vials of different iron concentrations (iron (II) chloride) from 0.5 millimoles to 50 millimoles and six healthy subjects were scanned using 3D high-resolution (0.94x0.94x0.94 mm3) rosette UTE sequence at an echo time (TE) of 20 s. ResultsIron-related hyperintense signals (i.e., positive contrast) were detected based on the phantom scan, and were used to establish an association between iron concentration and signal intensity. The signal intensities from in vivo scans were then converted to iron concentrations based on the association. The deep brain structures, such as the substantia nigra, putamen, and globus pallidus, were highlighted after the conversion, which indicated potential iron accumulations. ConclusionThis study suggested that T1-weighted signal intensity could be used for brain iron mapping.

neuroscience↗

bioRxiv2021

Myelin Imaging Using 3D Dual-echo Ultra-short Echo Time MRI with Rosette k-Space Pattern

PurposeThis study aimed to develop a new 3D dual-echo rosette k-space trajectory, specifically for ultra-short echo time (UTE) magnetic resonance imaging (MRI) applications. The direct imaging of the myelin bilayer, which has ultra-short transverse relaxation time (uT2), was acquired to test the performance of the proposed UTE sequence. Theory and MethodsThe rosette trajectory was developed based on rotations of a petal-like pattern in the kx-ky plane, with oscillated extensions in kz-direction for 3D coverage. Five healthy volunteers were recruited and underwent ten dual-echo 3D rosette UTE scans with various echo times (TEs). Dual-exponential complex model fitting was performed on the magnitude data to separate uT2 signals, with the output of uT2 fraction, uT2 value, and long T2 value. ResultsThe reconstructed images signal contrast between whiate matter (WM) and grey matter (GM) increased with longer TEs. The WM regions had higher uT2 fraction values than GM (10.9%{+/-}1.9% vs. 5.7%{+/-}2.4%). The uT2 value was approximately 0.15 milliseconds in WM. ConclusionThe higher uT2 fraction value in WM compared to GM demonstrated the ability of the proposed sequence to capture rapidly decaying signals.

neuroscience↗

bioRxiv2020

High-Resolution Metabolic Mapping of the Cerebellum Using a Reduced Field of View (Zoomed) Magnetic Resonance Spectroscopic Imaging

PurposeThe human cerebellum plays an important role in functional activity cerebrum which is ranging from motor to cognitive activities since due to its relaying role between spinal cord and cerebrum. The cerebellum poses many challenges to magnetic resonance spectroscopic imaging (MRSI) due to the caudal location, the susceptibility to physiological artifacts and partial volume artifact due to its complex anatomical structure. Thus, in present study, we propose a high-resolution MRSI acquisition scheme for the cerebellum. MethodsA zoomed or reduced-field of view (rFOV) metabolite-cycled full-intensity magnetic resonance spectroscopic imaging (MRSI) at 3T with a nominal resolution of 62.5 L was developed. Single-slice rFOV MRSI data were acquired from the cerebellum of 5 healthy subjects with a nominal resolution of 2.5{square}x{square}2.5{square}mm2 in 9{square}minutes 36. Spectra were quantified with LCModel. A spatially unbiased atlas template of the cerebellum was used for analyzing metabolite distributions in the cerebellum. ResultsThe high quality of the achieved spectra enabled to generate a high-resolution metabolic map of total N-acetylaspartate, total creatine, total choline, glutamate+glutamine and myo-inositol with Cramer-Rao lower bounds below 50%. A spatially unbiased atlas template of the cerebellum-based region of interest (ROIs) analysis resulted in spatially dependent metabolite distributions in 9 ROIs. The group-averaging across subjects in the Montreal Neurological Institute-152 template space allowed to generate a very high-resolution metabolite maps in the cerebellum. ConclusionThese findings indicate that very high-resolution metabolite probing of cerebellum is feasible using rFOV or zoomed MRSI at 3T.

neuroscience↗