arXiv subjects

Seth A. Smith

Publications and source records attributed to Seth A. Smith.

4 recordsLinked to original sources

arXiv2026

Harmonization mitigates diffusion MRI scanner effects in infancy: insights from the HEALthy Brain and Childhood Development (HBCD) study

The HEALthy Brain and Childhood Development (HBCD) Study is an ongoing longitudinal initiative to understand population-level brain maturation; however, large-scale studies must overcome site-related variance and preserve biologically relevant signal. In addition to diffusion-weighted magnetic resonance imaging images, the HBCD dataset offers analysis-ready derivatives for scientists to conduct their analysis, including scalar diffusion tensor (DTI) metrics in a predetermined set of bundles. The purpose of this study is to characterize HBCD-specific site effects in diffusion MRI data, which have not been systematically reported. In this work, we investigate the sensitivity of HBCD bundle metrics to scanner model-related variance and address these variations with ComBat-GAM harmonization within the current HBCD data release 1.1 across six scanner models. Following ComBat-GAM, we observe zero statistically significant differences between the distributions from any scanner model following FDR correction and reduce Cohen's f effect sizes across all metrics. Our work underscores the importance of rigorous harmonization efforts in large-scale studies, and we encourage future investigations of HBCD data to control for these effects.

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arXiv2025

Low-Cost and Detunable Wireless Resonator Glasses for Enhanced Eye MRI with Concurrent High-Quality Whole Brain MRI

Purpose: To develop and evaluate a wearable wireless resonator glasses design that enhances eye MRI signal-to-noise ratio (SNR) without compromising whole-brain image quality at 7 T. Methods: The device integrates two detunable LC loop resonators into a lightweight, 3D-printed frame positioned near the eyes. The resonators passively couple to a standard 2Tx/32Rx head coil without hardware modifications. Bench tests assessed tuning, isolation, and detuning performance. B1$^+$ maps were measured in a head/shoulder phantom, and SNR maps were obtained in both phantom and in vivo experiments. Results: Bench measurements confirmed accurate tuning, strong inter-element isolation, and effective passive detuning. Phantom B1$^+$ mapping showed negligible differences between configurations with and without the resonators. Phantom and in vivo imaging demonstrated up to about a 3-fold SNR gain in the eye region, with no measurable SNR loss in the brain. Conclusion: The wireless resonator glasses provide a low-cost, easy-to-use solution that improves ocular SNR while preserving whole-brain image quality, enabling both dedicated eye MRI and simultaneous eye-brain imaging at ultrahigh field.

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arXiv2025

Comparison and calibration of MP2RAGE quantitative T1 values to multi-TI inversion recovery T1 values

While typical qualitative T1-weighted magnetic resonance images reflect scanner and protocol differences, quantitative T1 mapping aims to measure T1 independent of these effects. Changes in T1 in the brain reflect structural changes in brain tissue. Magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) is an acquisition protocol that allows for efficient T1 mapping with a much lower scan time per slab compared to multi-TI inversion recovery (IR) protocols. We collect and register B1-corrected MP2RAGE acquisitions with an additional inversion time (MP3RAGE) alongside multi-TI selective inversion recovery acquisitions for four subjects. We use a maximum a posteriori (MAP) T1 estimation method for both MP2RAGE and compare to typical point estimate MP2RAGE T1 mapping, finding no bias from MAP MP2RAGE but a sensitivity to B1 inhomogeneities with MAP MP3RAGE. We demonstrate a tissue-dependent bias between MAP MP2RAGE T1 estimates and the multi-TI inversion recovery T1 values. To correct this bias, we train a patch-based ResNet-18 to calibrate the MAP MP2RAGE T1 estimates to the multi-TI IR T1 values. Across four folds, our network reduces the RMSE significantly (white matter: from 0.30 +/- 0.01 seconds to 0.11 +/- 0.02 seconds, subcortical gray matter: from 0.26 +/- 0.02 seconds to 0.10 +/- 0.02 seconds, cortical gray matter: from 0.36 +/- 0.02 seconds to 0.17 +/- 0.03 seconds). Using limited paired training data from both sequences, we can reduce the error between quantitative imaging methods and calibrate to one of the protocols with a neural network.

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arXiv2017

Estimated Incidence of Ophthalmic Conditions Associated with Optic Nerve Disease in Middle Tennessee

Aims. The objective of this paper is to determine the incidence of ophthalmic disease potentially leading to optic nerve disease in Middle Tennessee. Methods. We use a retrospective population-based incidence study design focusing on the population of middle Tennessee and its nearby suburbs (N=3 397 515). The electronic medical records for all patients evaluated or treated at a large tertiary care hospital and clinics with an initial diagnosis of a disease either affecting the optic nerve, or potentially associated with optic nerve disease, between 2007 and 2014 were retrieved and analyzed. Results. 18 291 patients (10 808 F) with 18 779 incidence events were identified with an age range of 0-101 years from the query of the Vanderbilt BioVU. Estimated age-adjusted incidence per 100 000 population per year was 198.4/145.1 (glaucoma F/M), 14.4/11.4 (intrinsic optic nerve disease F/M), 10.6/5.8 (optic nerve edema F/M), 6.1/6.6 (orbital inflammation F/M), and 23.7/6.7 (thyroid disease F/M). Glaucoma incidence was strongly correlated with age with the incidence sharply increasing after age 40. Optic nerve edema incidence peaked in the 25-34 old females. African American population has increased likelihood of glaucoma, orbital inflammation, and thyroid disease. Conclusions. Mapping the incidence of pathologies of the optic nerve is essential to the understanding of the relative likelihood of these conditions and impacts upon public health. We find incidence of optic nerve diseases strongly varies by gender, age, and race which have not been previously studied using a unified framework or within a single metropolitan population

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