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Contrast and stability of the axon diameter index from microstructure imaging with diffusion MRI.

Dyrby TB, Sogaard LV, Hall MG, Ptito M, Alexander DC - Magn Reson Med (2012)

Bottom Line: Data were acquired on a fixed monkey brain and Monte-Carlo simulations supported the results.Increasing Gmax reduces within-voxel variation of the axon diameter index and improves contrast beyond what is achievable with higher signal-to-noise ratio.These results emphasize the key-role of Gmax for enhancing contrast between axon diameter distributions and are, therefore, relevant in general for microstructure imaging methods and highlight the need for increased Gmax on future commercial systems.

View Article: PubMed Central - PubMed

Affiliation: Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.

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Voxel-wise estimation of axon diameter index in the CC of the fixed monkey brain. Axon diameter index obtained from sessions I (a–d) and II (e–h), shown in a midsagittal slice for Gmax = 60, 140, 200, and 300 mT/m. The range of diameters is shown by the color bar. High agreement between the two sessions is observed. Higher Gmax improves spatial coherence and more anatomical details appear. Abbreviations: Genu (CC-G), midbody (CC-M), and splenium (CC-S) regions of CC, fornix (For), and anterior commissure (AC).
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fig05: Voxel-wise estimation of axon diameter index in the CC of the fixed monkey brain. Axon diameter index obtained from sessions I (a–d) and II (e–h), shown in a midsagittal slice for Gmax = 60, 140, 200, and 300 mT/m. The range of diameters is shown by the color bar. High agreement between the two sessions is observed. Higher Gmax improves spatial coherence and more anatomical details appear. Abbreviations: Genu (CC-G), midbody (CC-M), and splenium (CC-S) regions of CC, fornix (For), and anterior commissure (AC).

Mentions: The voxel-wise axon diameter indices in the midsagittal plane of CC for all Gmax shown in Figure 5 clearly get less noisy with higher Gmax. Regional clusters of different axon diameter indices, especially in splenium, fornix, and anterior commissure, become clear as Gmax increases, especially for Gmax > 140 mT/m. The simulations in Figure 1 predict a reduction in variation of a′ at higher Gmax, and it is clearly seen from Figure 5 how this enhances the anatomical detail visible in the axon diameter index map.


Contrast and stability of the axon diameter index from microstructure imaging with diffusion MRI.

Dyrby TB, Sogaard LV, Hall MG, Ptito M, Alexander DC - Magn Reson Med (2012)

Voxel-wise estimation of axon diameter index in the CC of the fixed monkey brain. Axon diameter index obtained from sessions I (a–d) and II (e–h), shown in a midsagittal slice for Gmax = 60, 140, 200, and 300 mT/m. The range of diameters is shown by the color bar. High agreement between the two sessions is observed. Higher Gmax improves spatial coherence and more anatomical details appear. Abbreviations: Genu (CC-G), midbody (CC-M), and splenium (CC-S) regions of CC, fornix (For), and anterior commissure (AC).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4199276&req=5

fig05: Voxel-wise estimation of axon diameter index in the CC of the fixed monkey brain. Axon diameter index obtained from sessions I (a–d) and II (e–h), shown in a midsagittal slice for Gmax = 60, 140, 200, and 300 mT/m. The range of diameters is shown by the color bar. High agreement between the two sessions is observed. Higher Gmax improves spatial coherence and more anatomical details appear. Abbreviations: Genu (CC-G), midbody (CC-M), and splenium (CC-S) regions of CC, fornix (For), and anterior commissure (AC).
Mentions: The voxel-wise axon diameter indices in the midsagittal plane of CC for all Gmax shown in Figure 5 clearly get less noisy with higher Gmax. Regional clusters of different axon diameter indices, especially in splenium, fornix, and anterior commissure, become clear as Gmax increases, especially for Gmax > 140 mT/m. The simulations in Figure 1 predict a reduction in variation of a′ at higher Gmax, and it is clearly seen from Figure 5 how this enhances the anatomical detail visible in the axon diameter index map.

Bottom Line: Data were acquired on a fixed monkey brain and Monte-Carlo simulations supported the results.Increasing Gmax reduces within-voxel variation of the axon diameter index and improves contrast beyond what is achievable with higher signal-to-noise ratio.These results emphasize the key-role of Gmax for enhancing contrast between axon diameter distributions and are, therefore, relevant in general for microstructure imaging methods and highlight the need for increased Gmax on future commercial systems.

View Article: PubMed Central - PubMed

Affiliation: Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.

Show MeSH