Comparative Evaluation of Single-Voxel and Multi-Voxel Proton Magnetic Resonance Spectroscopy Using Small-Sized Voxels in Healthy Beagle Dogs: A Pilot Study

Use of single voxel intermediate echo time magnetic resonance spectroscopy at 3 Tesla in dogs with meningoencephalitis of unknown origin

Introduction Magnetic resonance spectroscopy (MRS) is a magnetic resonance imaging (MRI) sequence that identifies and quantifies metabolites within brain tissue by identifying the degree and amplitude of the chemical shift. MRS is rarely used in veterinary medicine due to a lack of published research and familiarity with scanning techniques and interpretation. By evaluating relative changes to metabolite concentration within brain tissue, this sequence can identify pathologic processes. This study evaluated the use of a single voxel, intermediate echo time MRS sequence at 3T in dogs with non-infectious meningoencephalitis of unknown origin (MUO) to determine the feasibility and utility of this scan as an additional diagnostic tool for this disease. Methods MRS was incorporated into MRI scans of client-owned dogs presenting to the University of Missouri Veterinary Health Center (MU VHC). Dogs with MUO were diagnosed antemortem based on history, imaging findings, cerebrospinal fluid analysis, and/or response to therapy. Dogs with structurally normal brains on MRI were used as a control group. Dogs aged 1-10 years were included in the study, identifying 18 normal dogs and 4 dogs with MUO. Patient signalment, clinical information, and clinical history details were recorded and compared. Metabolite height, area, and ratios were compared between groups. A secondary evaluation of dogs with seizures was performed to identify if a time-dependent association with MRI changes or metabolite area existed. Results This study found a statistically significant increase in choline peak height (p = 0.001) and area (p = 0.003) within the patients within the MUO cohort compared to dogs in the normal group. The height of the creatine peak was also significantly higher in the MUO group (p = 0.04), though the overall concentration indicated by peak area was not. Other trends, including a decreased NAA/creatine ratio and an increased NAA height and area, lactate height, and choline/creatine ratio, were identified in the MUO group. All MUO patients and all but one normal dog had a measurable lactate peak, indicating that a small amount of lactate concentration may be incidental in the dog brain at 3T. The presence of postictal changes in dogs with seizures was found not to be related to days since the last seizure. The NAA/Cr ratio had a time-dependent positive correlation to days since the last seizure. Lastly, a dog with a genetic neurodegenerative disease was identified during the acquisition of this study, and this dog's MRS spectra may be the first described in dogs with this disease. Discussion This study found several significant differences between groups, some of which were expected (increased choline in the MUO group) and some unexpected (increased NAA in dogs with MUO). This investigation showed that this MRS method is feasible, creates good quality spectral data, and could have diagnostic benefit in dogs with MUO. Further validation of this pilot study, notably with baseline correction and reevaluation of NAA concentration, is needed before adopting this sequence into the standard diagnostic workup for dogs with MUO.

Regional normal-appearing white matter metabolic profiles and cognition in early relapsing-remitting multiple sclerosis: a multi-voxel proton magnetic resonance spectroscopy study.

Testing the reliability of novel Voxel Placement approaches for Magnetic Resonance Spectroscopy

Both MGRP and SSVR improved voxel placement and metabolite measurement reproducibility compared with conventional anatomy-based placement and improved within-subject reproducibility across repeated sessions, providing a robust approach for longitudinal single-voxel MRS studies.

Canine brain imaging with a new low-field portable (0.05 T) MRI scanner: a pilot in vivo comparison to conventional 1.5 T

This pilot study successfully translated a previously developed LF MRI canine cadaver brain protocol for in vivo application and compared the acquired images with paired 1.5 T MRI images from 21 different canine patients, representing the first in vivo usage and evaluation of a 0.05 T MRI in a clinical veterinary context.

7 Tesla MRI with Quantitative Susceptibility Mapping: qualitative grading and quantitative focal measurements of the substantia nigra as a potential biomarker for Parkinson's disease.

PURPOSE Parkinson's disease (PD) is characterized by dopaminergic neuronal loss in the substantia nigra (SN). Imaging biomarkers sensitive to nigral pathology are limited. This study evaluated susceptibility changes in the SN using quantitative susceptibility mapping (QSM) and susceptibility-weighted imaging (SWI) at 7 Tesla MRI, and explored associations with clinical variables. METHODS In this exploratory cross-sectional study, 76 healthy controls (HC) and 26 PD patients underwent 7 Tesla QSM; SWI was available in 53 HC and all PD patients. Grading of dorsal (SN) was performed on QSM and SWI using a four-point scale. Using Sectra IDS7, focal susceptibility values were measured in QSM images in anterior and dorsal SN ROIs. Correlation analyses with clinical variables were performed. RESULTS Intra-rater reliability for repeated focal SN measurements ranged from moderate to excellent (ICC range 0.68-0.95). Focal dorsal SN susceptibility was significantly higher in PD patients compared with HC (p < 0.001). The area under the ROC curve for dorsal SN was 0.90 ( 95% CI 0.80-0.99). A two-step QSM approach combining visual grading and focal susceptibility measurement showed sensitivity of 88.5% and specificity of 89.5%. No clinical correlations remained significant after FDR correction. CONCLUSION In this exploratory 7 Tesla MRI study, the focal dorsal SN susceptibility was significantly higher in PD patients. A combined QSM approach using visual grading followed by focal susceptibility measurement may provide added value in the imaging assessment of PD. These exploratory findings require validation in larger, preferably multicentre cohorts, with all readers blinded to disease status.

Magnetic Resonance Imaging of the Neonatal Brain: Modalities, Scoring Systems, and Clinical Applications

Magnetic resonance imaging (MRI) has become the gold standard for evaluating brain injury and development in newborn infants, providing structural, metabolic, and functional information without ionizing radiation. This review comprehensively examines the principal MRI modalities used in current neonatal neuroimaging for a novice/intermediate-level reader—including conventional T1- and T2-weighted imaging, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping, diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS), susceptibility-weighted imaging (SWI), volumetric analysis, arterial spin labeling (ASL), and functional connectivity MRI—with particular attention to their applications in preterm and term populations. Additionally, validated MRI scoring systems for quantifying brain injury severity and predicting neurodevelopmental outcomes are reviewed and summarized. Understanding the technical principles, clinical applications, and limitations of these modalities is essential for optimal interpretation of neonatal brain MRI, and for advancing prognostication and therapeutic decision-making in this vulnerable population.