arXiv subjects

Gonzalo G. Rodriguez

Publications and source records attributed to Gonzalo G. Rodriguez.

3 recordsLinked to original sources

arXiv2026

Multinuclear fingerprinting

We developed a new magnetic resonance imaging method called multinuclear fingerprinting (MNF) which leverages simultaneously-acquired proton (1H) and sodium (23Na) data to generate seven quantitative maps of the whole brain: proton density (PD), T1 and T2 relaxation times from water, and tissue sodium concentration (TSC), T1, T2short and T2long from Na+ ions. MNF consists of two parts: (1) simultaneous 1H/23Na magnetic resonance fingerprinting (MRF), and (2) a super-resolution (SR) algorithm to increase the 23Na resolution to match the 1H resolution. It was tested on the brain of seven healthy subjects at 7 T, with a final resolution of 1.5x1.5x5 mm3 for all maps acquired in 13 min. MNF could provide new fundamental insights into the inter-relationship between morphology (i.e. tissue structure from the 1H maps) and physiology (i.e. ion homeostasis from the 23Na maps) in vivo to help improve our understanding of the human brain in general, and to study neuropathologies and their treatments. Since all 1H/23Na MRF data is acquired simultaneously, all images are exactly co-registered with identical spatial and temporal resolutions. MNF could be useful in future longitudinal studies for assessing local time-dependent and conjoint 1H/23Na MR changes during tasks or interventions. MNF was initially developed for neuroimaging, but it can be adapted to any other parts of the body.

physics.med-ph↗

arXiv2025

Correlation-weighted 23Na magnetic resonance fingerprinting in the brain

We developed a new sodium magnetic resonance fingerprinting ($^\text{23}\text{Na}$ MRF) method for the simultaneous mapping of $\text{T}_\text{1}$, $\text{T}_\text{2,long}^{*}$, $\text{T}_\text{2,short}^{*}$ and sodium density with built-in $Δ\text{B}_{1}^{+}$ (radiofrequency transmission inhomogeneities) and $Δ\text{f}_\text{0}$ corrections (frequency offsets). We based our $^\text{23}\text{Na}$ MRF implementation on a 3D FLORET sequence with 23 radiofrequency pulses. To capture the complex spin ${\frac{\text{3}}{\text{2}}}$ dynamics of the $^\text{23}\text{Na}$ nucleus, the fingerprint dictionary was simulated using the irreducible spherical tensor operators formalism. The dictionary contained 831,512 entries covering a wide range of $\text{T}_\text{1}$, $\text{T}_\text{2,long}^{*}$, $\text{T}_\text{2,short}^{*}$, $Δ\text{B}_\text{1}^{+}$ factor and $Δ\text{f}_\text{0}$ parameters. Fingerprint matching was performed using the Pearson correlation and the resulting relaxation maps were weighted with a subset of the highest correlation coefficients corresponding to signal matches for each voxel. Our $^\text{23}\text{Na}$ MRF method was compared against reference methods in a 7-compartment phantom, and applied in brain in five healthy volunteers at 7 T. In phantoms, $^\text{23}\text{Na}$ MRF produced values comparable to those obtained with reference methods. Average sodium relaxation time values in cerebrospinal fluid, gray matter and white matter across five healthy volunteers were in good agreement with values previously reported in the literature.

physics.med-ph↗

arXiv2020

A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals

We present a fast field-cycling NMR relaxometer with added magnetic resonance imaging capabilities. The instrument operates at a maximum proton Larmor frequency of 5 MHz for a sample volume of 35 mL. The magnetic field homogeneity across the sample is 1400 ppm. The main field is generated with a notch-coil electromagnet of own design, fed with a current whose stability is 220 ppm. We show that images of reasonable quality can still be produced under such conditions. The machine is being designed for concept testing of the involved instrumentation and specific contrast agents aimed for field-cycling magnetic resonance imaging applications. The general performance of the prototype was tested through localized relaxometry experiments, T1-dispersion weighted images, temperature maps and T1-weighted images at different magnetic field intensities. We introduce the concept of positive and negative contrast depending on the use of pre-polarized or non-polarized sequences. The system is being improved for pre-clinical studies in small animals.

physics.med-ph↗