Bayesian Modeling of NMR Data: Quantifying Longitudinal Relaxation in Vivo, and in Vitro with a Tissue-Water-Relaxation Mimic (Crosslinked Bovine Serum Albumin)
- Autores: Meinerz K.1, Beeman S.2, Duan C.3, Bretthorst G.2, Garbow J.2,4, Ackerman J.2,3,4,5
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Afiliações:
- Department of Physics, Washington University
- Department of Radiology, Washington University
- Department of Chemistry, Washington University
- Alvin J. Siteman Cancer Center, Washington University
- Department of Internal Medicine, Washington University
- Edição: Volume 49, Nº 1 (2018)
- Páginas: 3-24
- Seção: Original Paper
- URL: https://journals.rcsi.science/0937-9347/article/view/248020
- DOI: https://doi.org/10.1007/s00723-017-0964-z
- ID: 248020
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Resumo
Recently, a number of magnetic resonance imaging protocols have been reported that seek to exploit the effect of dissolved oxygen (O2, paramagnetic) on the longitudinal 1H relaxation of tissue water, thus providing image contrast related to tissue oxygen content. However, tissue water relaxation is dependent on a number of mechanisms and this raises the issue of how best to model the relaxation data. This problem, the model selection problem, occurs in many branches of science and is optimally addressed by Bayesian probability theory. High signal-to-noise, densely sampled, longitudinal 1H relaxation data were acquired from rat brain in vivo and from a cross-linked bovine serum albumin (xBSA) phantom, a sample that recapitulates the relaxation characteristics of tissue water in vivo. Bayesian-based model selection was applied to a cohort of five competing relaxation models: (1) monoexponential, (2) stretched-exponential, (3) biexponential, (4) Gaussian (normal) R1-distribution, and (5) gamma R1-distribution. Bayesian joint analysis of multiple replicate datasets revealed that water relaxation of both the xBSA phantom and in vivo rat brain was best described by a biexponential model, while xBSA relaxation datasets truncated to remove evidence of the fast relaxation component were best modeled as a stretched exponential. In all cases, estimated model parameters were compared to the commonly used monoexponential model. Reducing the sampling density of the relaxation data and adding Gaussian-distributed noise served to simulate cases in which the data are acquisition-time or signal-to-noise restricted, respectively. As expected, reducing either the number of data points or the signal-to-noise increases the uncertainty in estimated parameters and, ultimately, reduces support for more complex relaxation models.
Sobre autores
Kelsey Meinerz
Department of Physics, Washington University
Email: ackerman@wustl.edu
Estados Unidos da América, Saint Louis, MO
Scott Beeman
Department of Radiology, Washington University
Email: ackerman@wustl.edu
Estados Unidos da América, Saint Louis, MO
Chong Duan
Department of Chemistry, Washington University
Email: ackerman@wustl.edu
Estados Unidos da América, Saint Louis, MO
G. Bretthorst
Department of Radiology, Washington University
Email: ackerman@wustl.edu
Estados Unidos da América, Saint Louis, MO
Joel Garbow
Department of Radiology, Washington University; Alvin J. Siteman Cancer Center, Washington University
Email: ackerman@wustl.edu
Estados Unidos da América, Saint Louis, MO; Saint Louis, MO
Joseph Ackerman
Department of Radiology, Washington University; Department of Chemistry, Washington University; Alvin J. Siteman Cancer Center, Washington University; Department of Internal Medicine, Washington University
Autor responsável pela correspondência
Email: ackerman@wustl.edu
Estados Unidos da América, Saint Louis, MO; Saint Louis, MO; Saint Louis, MO; Saint Louis, MO