Diffusion tensor MR microscopy of tissues with low diffusional anisotropy

Bajd, Franci; Mattea, Carlos; Stapf, Siegfried; Sersa, Igor

doi:10.1515/raon-2016-0018

Figures & Tables

A simulation flowchart for analysis of selected commonly used and random/isotropic diffusion sensitizing gradients (DSG) configurations.

Simulated two dimensional maps of D̅2 (DA signal - to - [SNR]), D̅3 (DA, SNR) - D̅1 (DA, SNR), and fractional anisotropy (FA)(DA, SNR) for four representative, commonly used diffusion sensitizing gradients (DSG) configurations from Table 1 (#1, #8, #13 and #16).

Panels on the left show simulated average values of diffusion tensor eigenvalues D1,D2 and D3 (A), of average diffusion constant ADC(C) and of fractional anisotropy FA(E) as a function of condition number 1<CN<104 for random diffusion sensitizing gradients (DSG) configurations. Panels on the right (B,D,F) display the zoomed left-side panels for condition numbers in the range 1<CN<10. Solid-line curves (E,F) correspond to best fits of the model function [Eq. 12] to the simulated data. The graphical insert in panel (A) illustrates the selected random DSG configuration with NDSG = 220.

Characteristic values of the simulated correlations between FA and condition number(CN)for random diffusion sensitizing gradients (DSG) configurations as a function of NDSG: maximal, average and minimal values of FA (A), best fit parameters αFA, κFA and fit quality R2(B). The arrow designates a crossover, at which apparent fractional anisotropy drops below fractional anisotropy FA ~0.01. The graphical insert in panel A illustrates the selected random DSG configuration with NDSG = 220.

Simulated average fractional anisotropy FA (solid symbols) and the corresponding condition number CN(void symbols) as a function of NDSG for random (blue symbols) and isotropic (red symbols) diffusion sensitizing gradients (DSG) configurations. The graphical insert illustrates a distribution of DSG directions in a random and an isotropic DSG configuration with NDSG = 200.

The results of numerical simulations with three different fractional anisotropy (FA) values: 0, 0.1, and 0.3 for isotropic (FA = 0) vs. anisotropic (FA = 0.1, 0.3) case.

$Experimental 1D DT-MRM results of the cone-shaped water phantom: 2D MR image of the phantom with the corresponding signal-to-noise ratio (SNR) 1D profile along the phantom axis (top left) and stack plots of the diffusion tensor quantities (D1, D2, D3, average diffusion coefficient [ADC] and FA) as 1D profiles as a function of NDSG. Isotropic diffusion sensitizing gradients (DSG) configurations were used. The white dotted curve depicts the region with noticeably reduced fractional anisotropy.$

Experimental 1D DT-MRM results of the cone-shaped water phantom: 2D MR image of the phantom with the corresponding signal-to-noise ratio (SNR) 1D profile along the phantom axis (top left) and stack plots of the diffusion tensor quantities (D1, D2, D3, average diffusion coefficient [ADC] and FA) as 1D profiles as a function of NDSG. Isotropic diffusion sensitizing gradients (DSG) configurations were used. The white dotted curve depicts the region with noticeably reduced fractional anisotropy.

Experimental DT-MRM results of articular cartilage-on-bone samples in a form of 2D maps of D1, D2, D3, average diffusion coefficient (ADC) and fractional anisotropy (FA). The maps were obtained with a spatial resolution of either 78 μm (A) or 156 μm (B). Solid white boxes indicate three different ROI regions for signal-to-noise ratio (SNR) determination, while dashed white lines encircle droplets of liquid expelled from the cartilage tissue. White arrows denote the compression zone.

A list of the analyzed commonly used diffusion sensitizing gradients (DSG) configurations in DTI, adopted from12, along with the corresponding values of NDSG, condition number(CN) and P_

#	Scheme name	N_DSG[1]	CN[1]	P[%]
1	Tetrahedral	6	9.148	16.53
2	Cond 6	6	5.984	14.19
3	Decahedral	10	2.748	10.70
4	Jones noniso	7	2.560	12.13
5	Dual-gradient	6	2.000	11.44
6	Jones 10	10	1.624	9.67
7	Jones 20	20	1.615	8.10
8	Jones 30	30	1.594	7.16
9	Papadakis	12	1.587	9.29
10	Jones 6	6	1.583	11.04
11	Muthupallai	6	1.581	11.11
12	Tetraortho	7	1.527	10.68
13	DSM 6	6	1.323	11.41
14	DSM 10	10	1.324	10.02
15	DSM 20	20	1.668	8.43
16	DSM 30	30	1.430	7.45
17	DSM 40	40	1.401	6.87

Average values of average diffusion coefficient (ADC) and fractional anisotropy (FA) in three different regions of an uncompressed and compressed cartilage sample obtained with two different spatial resolutions

	Higher resolution (78 μm)		Lower resolution (156 μm)
	ADC [10⁻⁹ m²/s]	FA[1]	ADC [10⁻⁹ m²/s]	FA[1]
Uncompressed cartilage	0.99±0.13	0.27±0.13	1.12±0.14	0.14±0.08
Compression zone	0.63±0.42	0.87±0.27	1.01±0.82	0.82±0.23
Liquid droplet	1.35±0.11	0.24±0.06	1.34±0.19	0.11±0.04

Diffusion tensor MR microscopy of tissues with low diffusional anisotropy

Figures & Tables

A list of the analyzed commonly used diffusion sensitizing gradients (DSG) configurations in DTI, adopted from12, along with the corresponding values of NDSG, condition number(CN) and P_

Average values of average diffusion coefficient (ADC) and fractional anisotropy (FA) in three different regions of an uncompressed and compressed cartilage sample obtained with two different spatial resolutions

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