3D‐multi‐echo radial imaging of <sup>23</sup>Na (3D‐MERINA) for time‐efficient multi‐parameter tissue compartment mapping

Blunck, Yasmin; Josan, Sonal; Syeda, Warda; Moffat, Bradford A.; Ordidge, Roger J.; Cleary, Jon O.; Johnston, Leigh A.

doi:10.1002/mrm.26848

Cited by 24 publications

(75 citation statements)

References 59 publications

(180 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However as the bi‐exponential model can be envisaged as sampling

T_{2}^{*}

distribution at two discrete points, the fast and slow

T_{2}^{*}

estimates should lie reasonably close to mean

T_{2}^{*}

in voxels with relatively narrow

T_{2}^{*}

distributions. For example in CSF voxels without partial voluming, a relatively smaller number of compartments are observed and the mean

T_{2}^{*}

values are reasonably closer to the previous studies . The wide spread of mean

T_{2}^{*}

distribution in CSF (Figure A) is due to strong partial volume effects present at low resolution, which are also present in GM and WM voxels, as suggested by the large overlap between empirical probability distributions.…”

Section: Discussionsupporting

confidence: 84%

“…Imaging was performed on a research 7T MRI (Siemens Healthineers, Erlangen, Germany) with a transmit‐receive dual‐tuned 1H‐23Na head coil (QED, Mayfield Village, Ohio, USA). Sodium images were acquired with a radial multi‐echo 3D‐MERINA acquisition protocol with parameters: TR = 160 ms, FA = 90 ∘ , TRO = 2 ms. A total of 38 echoes were acquired with the initial TE = 0.4 ms defined as the time interval between the centre of the pulse to ADC onset. Images were acquired over an isotropic field of view of 20 cm and regridded offline in MATLAB onto an isotropic grid with a nominal resolution of 3.1 mm, Prior to acquisition, shimming was performed on the 1 H‐channel using 10 iterations of an inbuilt shimming procedure.…”

Section: Methodsmentioning

confidence: 99%

“…The BEM model employed in Blunck et al to obtain two‐compartment parameter mapping from multi‐echo 23 Na decay signal is presented here for the sake of comparison and reference . The BEM model assumes a two‐component exponential decay signal, attributed to satellite and central transitions caused by complex quadrupolar and dipole interactions of sodium spin systems in slow motions regimes,

M^{BE} false(t; M_{0}, T_{2_{short}}^{*}, T_{2_{long}}^{*} false) = M_{0} [0.6 exp ()(- \frac{t}{T_{2_{short}}^{*}}) + 0.4 exp ()(- \frac{t}{T_{2_{long}}^{*}})],

where t is the echo time,

T_{2_{short}}^{*}, T_{2_{long}}^{*}

are the short and long

T_{2}^{*}

decay parameters and M 0 is the signal at the first echo, t 0 .…”

Section: Theorymentioning

confidence: 99%

“…Typically, a bi‐exponential model (BE) is fit to the signal under the assumption of a single sodium compartment, with the fast and slow signal fractions corresponding to satellite and central spin transitions. The signal fractions are either kept variable or constrained to a 60/40 ratio based on 23 Na spin dynamics . In the recent 3D‐MERINA sequence for efficient multi‐echo sodium MRI acquisition, a bi‐exponential mixture (BEM) approach to fitting the decay model was proposed .…”

Section: Introductionmentioning

confidence: 99%

“…The signal fractions are either kept variable or constrained to a 60/40 ratio based on 23 Na spin dynamics . In the recent 3D‐MERINA sequence for efficient multi‐echo sodium MRI acquisition, a bi‐exponential mixture (BEM) approach to fitting the decay model was proposed . The BEM approach is a two‐step procedure, firstly fitting a BE model, again constrained to the 60/40 ratio in brain tissue, and secondly replacing the BE with a mono‐exponential (ME) fit in regions found to be implausible for a two‐component BE fit, namely CSF.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A continuum of components: Flexible fast fraction mapping in sodium MRI

Syeda

Blunck

Kolbe

et al. 2019

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

Purpose Parameter mapping in sodium MRI data is challenging due to inherently low SNR and spatial resolution, prompting the need to employ robust models and estimation techniques. This work aims to develop a continuum model of sodium T2*‐decay to overcome the limitations of the commonly employed bi‐exponential models. Estimates of mean T2*‐decay and fast component fraction in tissue are emergent from the inferred continuum model. MethodsA closed‐form continuum model was derived assuming a gamma distribution of T2* components. Sodium MRI was performed on four healthy human subjects and a phantom consisting of closely packed vials filled with an aqueous solution of varying sodium and agarose concentrations. The continuum model was applied to the phantom and in vivo human multi‐echo 7T data. Parameter maps by voxelwise model‐fitting were obtained. ResultsThe continuum model demonstrated comparable estimation performance to the bi‐exponential model. The parameter maps provided improved contrast between tissue structures. The fast component fraction, an indicator of the heterogeneity of localised sodium motion regimes in tissue, was zero in CSF and high in WM structures. ConclusionsThe continuum distribution model provides high quality, high contrast parameter maps, and informative voxelwise estimates of the relative weighting between fast and slow decay components.

show abstract

“…However as the bi‐exponential model can be envisaged as sampling