Sheryl L Herrera1, Morgan E Mercredi2, Richard Buist3, Melanie Martin2,4. 1. Physics and Astronomy, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada. umherres@myumanitoba.ca. 2. Physics and Astronomy, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada. 3. Radiology, University of Manitoba, Winnipeg, MB, R3E 0T6, Canada. 4. Physics, University of Winnipeg, Winnipeg, MB, R3B 2E9, Canada.
Abstract
OBJECT: Most early methods to infer axon diameter distributions using magnetic resonance imaging (MRI) used single diffusion encoding sequences such as pulsed gradient spin echo (SE) and are thus sensitive to axons of diameters > 5 μm. We previously simulated oscillating gradient (OG) SE sequences for diffusion spectroscopy to study smaller axons including the majority constituting cortical connections. That study suggested the model of constant extra-axonal diffusion breaks down at OG accessible frequencies. In this study we present data from phantoms to test a time-varying interstitial apparent diffusion coefficient. MATERIALS AND METHODS: Diffusion spectra were measured in four samples from water packed around beads of diameters 3, 6 and 10 μm; and 151 μm diameter tubes. Surface-to-volume ratios, and diameters were inferred. RESULTS: The bead pore radii estimates were 0.60±0.08 μm, 0.54±0.06 μm and 1.0±0.1 μm corresponding to bead diameters ranging from 2.9±0.4 μm to 5.3±0.7 μm, 2.6±0.3 μm to 4.8±0.6 μm, and 4.9±0.7 μm to 9±1 μm. The tube surface-to-volume ratio estimate was 0.06±0.02 μm-1 corresponding to a tube diameter of 180±70 μm. CONCLUSION: Interstitial models with OG inferred 3-10 μm bead diameters from 0.54±0.06 μm to 1.0±0.1 μm pore radii and 151 μm tube diameters from 0.06±0.02 μm-1 surface-to-volume ratios.
OBJECT: Most early methods to infer axon diameter distributions using magnetic resonance imaging (MRI) used single diffusion encoding sequences such as pulsed gradient spin echo (SE) and are thus sensitive to axons of diameters > 5 μm. We previously simulated oscillating gradient (OG) SE sequences for diffusion spectroscopy to study smaller axons including the majority constituting cortical connections. That study suggested the model of constant extra-axonal diffusion breaks down at OG accessible frequencies. In this study we present data from phantoms to test a time-varying interstitial apparent diffusion coefficient. MATERIALS AND METHODS: Diffusion spectra were measured in four samples from water packed around beads of diameters 3, 6 and 10 μm; and 151 μm diameter tubes. Surface-to-volume ratios, and diameters were inferred. RESULTS: The bead pore radii estimates were 0.60±0.08 μm, 0.54±0.06 μm and 1.0±0.1 μm corresponding to bead diameters ranging from 2.9±0.4 μm to 5.3±0.7 μm, 2.6±0.3 μm to 4.8±0.6 μm, and 4.9±0.7 μm to 9±1 μm. The tube surface-to-volume ratio estimate was 0.06±0.02 μm-1 corresponding to a tube diameter of 180±70 μm. CONCLUSION: Interstitial models with OG inferred 3-10 μm bead diameters from 0.54±0.06 μm to 1.0±0.1 μm pore radii and 151 μm tube diameters from 0.06±0.02 μm-1 surface-to-volume ratios.
Entities:
Keywords:
axons; diffusion; imaging; magnetic resonance imaging; phantoms
Authors: F Agosta; E Pagani; M Petrolini; D Caputo; M Perini; A Prelle; F Salvi; M Filippi Journal: AJNR Am J Neuroradiol Date: 2010-04-15 Impact factor: 3.825
Authors: Junzhong Xu; Hua Li; Kevin D Harkins; Xiaoyu Jiang; Jingping Xie; Hakmook Kang; Mark D Does; John C Gore Journal: Neuroimage Date: 2014-09-16 Impact factor: 6.556