User:Jadrian Miles/Diffusion simulation - Revision history

Jadrian Miles at 01:08, 24 March 2009

2009-03-24T01:08:46Z

← Older revision		Revision as of 01:08, 24 March 2009
Line 5:		Line 5:
	* τ<sub>intra</sub> ~= 306 ms (but authors claim it's a bad fit) (ibid) (exchange times; see page 178 and ref 35)		* τ<sub>intra</sub> ~= 306 ms (but authors claim it's a bad fit) (ibid) (exchange times; see page 178 and ref 35)

			Human histology would be useful: hand-compute volume fraction of intracellular fluid, extracellular fluid, and myelin, as well as axon gauges.

			What about parallel DWIs and microscale histology on a sheep or macaque brain?

			Parameters:
			* direction: 1, 2, n
			* directional coherence: ignore, scalar
			* exchange: ignore, constant, per-compartment
			* isotropic D: constant globally, constant intra / extra, per-compartment
			* gauge: constant, per-compartment, fixed distribution, distribution per-compartment
			* volume fraction: intra / extra, per-compartment

	~~Human histology would be useful~~: ~~hand~~-~~compute volume fraction~~ of ~~intracellular fluid~~, ~~extracellular fluid~~, and ~~myelin, as well as axon gauges~~.		The experiment:
			# Generate lots of detailed 1-voxel numerical phantoms and run diffusion simulation on them to generate DWIs in a dense sampling of q-space. Now you have ground truth (kinda).
			# For a given phantom, fix all parameters but two at known correct values and then analyze the ambiguity between the free parameters. Treat one as independent and vary its assumed value; find the value of the other that best recreates the DWIs. Your output is a dependent-variable value ''and'' a DWI error.
			# For each pair of parameters, scatter-plot (or multi-line plot) the relationship between them over all phantoms.
			# Generalize some ambiguity rules and theorize about 'em.

Jadrian Miles at 00:47, 24 March 2009

2009-03-24T00:47:04Z

← Older revision		Revision as of 00:47, 24 March 2009
Line 1:		Line 1:
	* Axon gauges in range 0.25 -- 10 μm (wzhou cite 1)		* Axon gauges in range 0.25 -- 10 μm (wzhou cite 1). "Extra-thick" axons (~20μm) are rare; about 3% occurrence at most, and only in certain structures.
	* Hindered diffusion differs from free diffusion by a "tortuosity" value (Nicholson "Diffusion and related transport mechanisms" '01)		* Hindered diffusion differs from free diffusion by a "tortuosity" value (Nicholson "Diffusion and related transport mechanisms" '01)
	* Volume fraction is ~80% intra? (Nilsson MRI '08)		* Volume fraction is ~80% intra? (Nilsson MRI '08)

Jadrian Miles: New page: * Axon gauges in range 0.25 -- 10 μm (wzhou cite 1) * Hindered diffusion differs from free diffusion by a "tortuosity" value (Nicholson "Diffusion and related transport mechanisms" '01)...

2009-03-23T03:00:37Z

New page: * Axon gauges in range 0.25 -- 10 μm (wzhou cite 1) * Hindered diffusion differs from free diffusion by a "tortuosity" value (Nicholson "Diffusion and related transport mechanisms" '01)...

New page

* Axon gauges in range 0.25 -- 10 μm (wzhou cite 1)
* Hindered diffusion differs from free diffusion by a "tortuosity" value (Nicholson "Diffusion and related transport mechanisms" '01)
* Volume fraction is ~80% intra? (Nilsson MRI '08)
* Extracellular free D ~= 1.08 μm<sup>2</sup>/ms (ibid)
* τ<sub>intra</sub> ~= 306 ms (but authors claim it's a bad fit) (ibid) (exchange times; see page 178 and ref 35)

Human histology would be useful: hand-compute volume fraction of intracellular fluid, extracellular fluid, and myelin, as well as axon gauges.