Values (± standard deviations) of true T1, true T2 and excitation flip angle parameters measured on the Gd-DOTA doped phantoms by the gold-standard sequence, and T1 values derived from both post-processing methods of the MOLLI sequence.

<p>Values (± standard deviations) of true T1, true T2 and excitation flip angle parameters measured on the Gd-DOTA doped phantoms by the gold-standard sequence, and T1 values derived from both post-processing methods of the MOLLI sequence.</p

T1 (a), B1+ (b) and T2 (c) maps acquired on Gd-DOTA-doped phantoms using gold-standard sequences.

<p>T1 maps derived by the standard post-processing approach of the MOLLI sequence (d) and the novel simulation method (e). Mean relative errors between T1 values derived from gold standard sequence and the two different post-processing approaches of MOLLI sequence (f).</p

B0 (a,d) and B1+ (b,e) maps acquired respectively on the 2.2L agar phantom and on one of the volunteers.

<p>Inversion efficacy maps (c,f) were derived using a Bloch simulation of the 10 ms hyperbolic secant pulse used in the MOLLI sequence as well as B0 and B1+ constraints with a nominal B1 of 16.1μT.</p

Influence of the number of R-R recovery periods between inversion pulses on T1 values estimated by the standard (a) and the novel (b) post-processing approaches of MOLLI sequence.

<p>Influence of the number of R-R recovery periods between inversion pulses on T1 values estimated by the standard (a) and the novel (b) post-processing approaches of MOLLI sequence.</p

<i>In vivo</i> T2 and B1+ maps obtained using T2-prepared TrueFISP and Bloch-Siegert sequences, respectively (a and b).

<p><i>In vivo</i> T1 maps generated from standard and novel post-processing approaches of the MOLLI sequence (3HB) (c and d respectively). <i>In vivo</i> T1 maps generated from standard and novel post processing of the MOLLI sequence acquired without recovery period before second and third inversions (0HB) (e-f).</p

Robustness of both post-processing methods was assessed by Monte Carlo simulations.

<p>A large set of data (10⁵) was generated using the Bloch equations simulation and standard <i>in vivo</i> parameters: nominal flip angle α_nom = 24°, T2_nom = 41 ms, 400 < T1 < 2400 ms. For each dataset, the 11 points of the MOLLI sequence were modified with an additional noise corresponding to the experimental SNR. Datasets were then processed either by the standard or the novel post-processing approach using modified T2 and flip angle values (T2_mod and α_mod) randomly generated from standard deviations of T2 and B1+ mapping sequences. T1 values estimated by the two post-processing methods were compared to true T1 values (a). The T1 exploration window was divided into 20 intervals, wherein mean relative errors (b) as well as coefficient of variation of the values (c) were measured.</p

Deviation between true T1 values and T1 values determined by the standard post-processing approach as a function of T1 (a), T2 (b), nominal flip angle (c), and inversion efficacy η (d).

<p>The first dataset was generated using T2 = 60 ms, α = 35°, η = 1, the second with α = 35°, η = 1, T1 = 1180 ms, the third with T1 = 1180 ms, T2 = 60 ms, η = 1 and the fourth with T1 = 1180 ms, T2 = 60 ms, α = 35°. For each set of parameters, the 11 MOLLI points were reordered as a function of TI, and the 3-parameter model was adjusted on the recovery curve. T1 was then calculated (T1 = T1*×(B/A-1)) and compared to the true T1.</p

Texture analysis differentiates the four mouse strains.

<p>Two views of the same plot showing the clustering of mice groups after texture analysis from lower leg MRI. 1: wild-type, 2: <i>mdx/Large^myd</i>, 3: <i>Large^myd</i>, 4: <i>mdx</i> mice. MDF: Most Discriminant Features.</p

Muscle T2 for <i>mdx/Large^myd, Large^myd, mdx</i> and wild-type mice.

<p>Muscle T2 in milliseconds for the four mouse strains evaluated. *: Muscle T2 different from wild-type mice; #: muscle T2 different from <i>mdx</i> mice.</p

MRI versus histological analysis.

<p>MRI (A-D; TE = 40 ms, TR = 1500 ms) and histological images (H&E, magnification X12: E-H; magnification X200: I-L) of the left lower leg from <i>mdx/Large</i>^<i>myd</i> (A, E, I), Large^myd (B, F, J), <i>mdx</i> (C, G, K) and wild-type mice (D, H, L). The regions highlighted in the MRI (first row) and in the whole lower leg histological image (second row) are presented in a higher magnification in the third row. Different histological processes could be related to the hyperintensities regions in the MRI, such as clusters of degenerating cells (I), regenerating and adipose cells cells (K), and regions with mixed dystrophic characteristics (J).</p