The role of dendritic spines in water exchange measurements with diffusion MRI: Time-Dependent Single Diffusion Encoding MRI
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| author | Şimşek, Kadir Chakwizira, Arthur Nilsson, Markus Palombo, Marco |
| author_facet | Şimşek, Kadir Chakwizira, Arthur Nilsson, Markus Palombo, Marco |
| contents | Time-dependent diffusion MRI (dMRI) with single diffusion encoding (SDE) probes water dynamics in biological tissues, but signal interpretation depends on microstructure. While prior work focused on restricted/hindered diffusion and membrane permeation, diffusion-mediated exchange between dendritic shafts and spines in gray matter (GM) remains understudied. We hypothesize that impermeable spiny dendrites produce time-dependent SDE signals mimicking permeative exchange and investigate how spine density biases exchange time estimates.
Using Monte Carlo simulations and narrow escape theory, we quantify spine-shaft exchange times (3-26 ms), matching cortical permeative exchange estimates. A modified two-compartment Karger model characterizes time-dependent SDE signals but yields biased exchange estimates, reflecting spine volume fraction rather than morphology. Unaccounted diffusion-mediated exchange introduces up to 80% bias in NEXI/SMEX model estimates. We propose an extended three-compartment Karger model incorporating both diffusion-mediated (spine-shaft) and permeative (intra-extracellular) exchange. However, this model cannot uniquely separate membrane permeability from spine volume effects.
Our findings emphasize that dendritic spines should be considered in SDE-based exchange studies and caution against attributing exchange solely to permeability. Advanced methods are needed to disentangle these mechanisms in GM. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_18229 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The role of dendritic spines in water exchange measurements with diffusion MRI: Time-Dependent Single Diffusion Encoding MRI Şimşek, Kadir Chakwizira, Arthur Nilsson, Markus Palombo, Marco Medical Physics Biological Physics Time-dependent diffusion MRI (dMRI) with single diffusion encoding (SDE) probes water dynamics in biological tissues, but signal interpretation depends on microstructure. While prior work focused on restricted/hindered diffusion and membrane permeation, diffusion-mediated exchange between dendritic shafts and spines in gray matter (GM) remains understudied. We hypothesize that impermeable spiny dendrites produce time-dependent SDE signals mimicking permeative exchange and investigate how spine density biases exchange time estimates. Using Monte Carlo simulations and narrow escape theory, we quantify spine-shaft exchange times (3-26 ms), matching cortical permeative exchange estimates. A modified two-compartment Karger model characterizes time-dependent SDE signals but yields biased exchange estimates, reflecting spine volume fraction rather than morphology. Unaccounted diffusion-mediated exchange introduces up to 80% bias in NEXI/SMEX model estimates. We propose an extended three-compartment Karger model incorporating both diffusion-mediated (spine-shaft) and permeative (intra-extracellular) exchange. However, this model cannot uniquely separate membrane permeability from spine volume effects. Our findings emphasize that dendritic spines should be considered in SDE-based exchange studies and caution against attributing exchange solely to permeability. Advanced methods are needed to disentangle these mechanisms in GM. |
| title | The role of dendritic spines in water exchange measurements with diffusion MRI: Time-Dependent Single Diffusion Encoding MRI |
| topic | Medical Physics Biological Physics |
| url | https://arxiv.org/abs/2506.18229 |