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1. Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T

   https://doi.org/10.1002/mrm.28404  

   Liu, Yuchi ; Hamilton, Jesse ; Eck, Brendan ; Griswold, Mark ; Seiberlich, Nicole ( July 2020 , Magnetic Resonance in Medicine)

   This work aims to develop an approach for simultaneous water–fat separation and myocardial T₁and T₂quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.

   Two 15‐heartbeat cMRF sequences with different rosette trajectories designed for water–fat separation at 3T and 1.5T were implemented. Water T₁and T₂maps, water image, and fat image were generated with B₀inhomogeneity correction using a B₀map derived from the cMRF data themselves. The proposed water–fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T.

   Water T₁and T₂values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T₁but 2~3 ms higher T₂values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.

   Rosette cMRF provides fat images along with myocardial T₁and T₂maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.

    

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2. Cardiac phase-resolved late gadolinium enhancement imaging

   https://doi.org/10.3389/fcvm.2022.917180  

   Weingärtner, Sebastian ; Demirel, Ömer B. ; Gama, Francisco ; Pierce, Iain ; Treibel, Thomas A. ; Schulz-Menger, Jeanette ; Akçakaya, Mehmet ( September 2022 , Frontiers in Cardiovascular Medicine)

   Late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR) imaging is the clinical reference for assessment of myocardial scar and focal fibrosis. However, current LGE techniques are confined to imaging of a single cardiac phase, which hampers assessment of scar motility and does not allow cross-comparison between multiple phases. In this work, we investigate a three step approach to obtain cardiac phase-resolved LGE images: (1) Acquisition of cardiac phase-resolved imaging data with varyingT₁weighting. (2) Generation of semi-quantitative${\mathbf{\text{T}}}_{\mathbf{\text{1}}}^{\mathbf{\text{*}}}$maps for each cardiac phase. (3) Synthetization of LGE contrast to obtain functional LGE images. The proposed method is evaluated in phantom imaging, six healthy subjects at 3T and 20 patients at 1.5T. Phantom imaging at 3T demonstrates consistent contrast throughout the cardiac cycle with a coefficient of variation of 2.55 ± 0.42%.In-vivoresults show reliable LGE contrast with thorough suppression of the myocardial tissue is healthy subjects. The contrast between blood and myocardium showed moderate variation throughout the cardiac cycle in healthy subjects (coefficient of variation 18.2 ± 3.51%). Images were acquired at 40–60 ms and 80 ms temporal resolution, at 3T and 1.5, respectively. Functional LGE images acquired in patients with myocardial scar visualized scar tissue throughout the cardiac cycle, albeit at noticeably lower imaging resolution and noise resilience than the reference technique. The proposed technique bears the promise of integrating the advantages of phase-resolved CMR with LGE imaging, but further improvements in the acquisition quality are warranted for clinical use.

    

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3. Temporally resolved parametric assessment of Z‐magnetization recovery (TOPAZ): Dynamic myocardial T 1 mapping using a cine steady‐state look‐locker approach

   https://doi.org/10.1002/mrm.26887  

   Weingärtner, Sebastian ; Shenoy, Chetan ; Rieger, Benedikt ; Schad, Lothar R. ; Schulz‐Menger, Jeanette ; Akçakaya, Mehmet ( August 2017 , Magnetic Resonance in Medicine)

   To develop and evaluate a cardiac phase‐resolved myocardial T₁mapping sequence.

   The proposed method for temporally resolved parametric assessment of Z‐magnetization recovery (TOPAZ) is based on contiguous fast low‐angle shot imaging readout after magnetization inversion from the pulsed steady state. Thereby, segmented k‐space data are acquired over multiple heartbeats, before reaching steady state. This results in sampling of the inversion‐recovery curve for each heart phase at multiple points separated by an R‐R interval. Joint T₁andestimation is performed for reconstruction of cardiac phase‐resolved T₁andmaps. Sequence parameters are optimized using numerical simulations. Phantom and in vivo imaging are performed to compare the proposed sequence to a spin‐echo reference and saturation pulse prepared heart rate–independent inversion‐recovery (SAPPHIRE) T₁mapping sequence in terms of accuracy and precision.

   In phantom, TOPAZ T₁values with integratedcorrection are in good agreement with spin‐echo T₁values (normalized root mean square error = 4.2%) and consistent across the cardiac cycle (coefficient of variation = 1.4 ± 0.78%) and different heart rates (coefficient of variation = 1.2 ± 1.9%). In vivo imaging shows no significant difference in TOPAZ T₁times between the cardiac phases (analysis of variance:P = 0.14, coefficient of variation = 3.2 ± 0.8%), but underestimation compared with SAPPHIRE (T₁time ± precision: 1431 ± 56 ms versus 1569 ± 65 ms). In vivo precision is comparable to SAPPHIRE T₁mapping until middiastole (P > 0.07), but deteriorates in the later phases.

   The proposed sequence allows cardiac phase‐resolved T₁mapping with integratedassessment at a temporal resolution of 40 ms. Magn Reson Med 79:2087–2100, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

    

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4. Fast chemical exchange saturation transfer imaging based on PROPELLER acquisition and deep neural network reconstruction

   https://doi.org/10.1002/mrm.28376  

   Guo, Chenlu ; Wu, Jian ; Rosenberg, Jens T. ; Roussel, Tangi ; Cai, Shuhui ; Cai, Congbo ( June 2020 , Magnetic Resonance in Medicine)

   To develop a method for fast chemical exchange saturation transfer (CEST) imaging.

   The periodically rotated overlapping parallel lines enhanced reconstruction (PROPELLER) sampling scheme was introduced to shorten the acquisition time. Deep neural network was employed to reconstruct CEST contrast images. Numerical simulation and experiments on a creatine phantom, hen egg, and in vivo tumor rat brain were performed to test the feasibility of this method.

   The results from numerical simulation and experiments show that there is no significant difference between reference images and CEST‐PROPELLER reconstructed images under an acceleration factor of 8.

   Although the deep neural network is trained entirely on synthesized data, it works well on reconstructing experimental data. The proof of concept study demonstrates that the combination of the PROPELLER sampling scheme and the deep neural network enables considerable acceleration of saturated image acquisition and may find applications in CEST MRI.

    

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5. Chronic statin therapy is associated with enhanced cutaneous vascular responsiveness to sympathetic outflow during passive heat stress

   https://doi.org/10.1113/JP278237  

   Greaney, Jody L. ; Stanhewicz, Anna E. ; Kenney, W. Larry ( August 2019 , The Journal of Physiology)

   Impairments in both central sympathetic and peripheral microvascular function contribute to blunted reflex cutaneous vasodilatation during heat stress in healthy older adults.

   Hypercholesterolaemia is associated with decrements in neurovascular function; however, little is known about the impact of hypercholesterolaemia on the integrated responses to heat stress. Further, whether chronic statin therapy alters skin sympathetic outflow or its relation to cutaneous vascular conductance during heat stress is unknown.

   We demonstrate that reflex cutaneous vasodilatation is impaired in older hypercholesterolaemic adults but not in formerly hypercholesterolaemic adults currently treated with a statin compared to age‐matched controls.

   Additionally, chronic statin treatment‐induced improvements in reflex vasodilatation are mediated, in part, by increases in end‐organ responsiveness to efferent sympathetic outflow during whole‐body heating.

   These data add to the growing body of literature substantiating the beneficial pleiotropic neurovascular effects of chronic statin treatment and provide further support for the use of statins to confer additional cardioprotective benefits in older adults.

   Attenuated reflex cutaneous vasodilatation in healthy human ageing is mediated by alterations in both central (sympathetic outflow) and peripheral (microvascular endothelial) function. Hypercholesterolaemia is associated with further impairments in neurovascular function. HMG‐CoA reductase inhibitors (statins) improve cutaneous endothelium‐dependent dilatation; however, whether statin therapy alters skin sympathetic nervous system activity (SSNA) or its relation to cutaneous vascular conductance (CVC) during passive heat stress is unknown. We hypothesized that (1) hypercholesterolaemic older adults would demonstrate blunted increases in both SSNA and CVC during passive heating and (2) chronic statin treatment would improve the response range and sensitivity of the SSNA:CVC relation. Reflex vasodilatation in response to a 1.0°C rise in oral temperature (T_or; water perfused suit) was induced in 13 healthy normocholesterolaemic adults (62 ± 2 years; LDL = 113 ± 7 mg/dl), 10 hypercholesterolaemic adults (60 ± 1 years; LDL = 183 ± 2 mg/dl), and 10 previously hypercholesterolaemic adults (64 ± 1 years; LDL = 102 ± 2 mg/dl) treated with lipophilic statin (10–40 mg daily). SSNA (peroneal microneurography) and red cell flux (laser‐Doppler flowmetry) in the innervated dermatome (dorsum of foot) were continuously measured. Reflex vasodilatation was blunted in hypercholesterolaemic adults, but not in statin‐treated adults, compared to normocholesterolaemic adults (at ∆T_or = 1.0°C: normal = 36 ± 1%CVC_max, high = 32 ± 1%CVC_max, statin = 38 ± 1%CVC_max;P < 0.01). ∆SSNA was not different (at ∆T_or = 1.0°C: normal: ∆ = 393 ± 96%, high: ∆ = 311 ± 120%, statin: ∆ = 256 ± 90%;P = 0.11). The slope of the SSNA:CVC relation was blunted in hypercholesterolaemic adults (0.02 ± 0.03%CVC_max/%_baseline) compared to both normocholesterolaemic (0.09 ± 0.02%CVC_max/%_baseline;P = 0.024) and statin‐treated (0.12 ± 0.05%CVC_max/%_baseline;P = 0.03) adults. Chronic statin treatment improves reflex cutaneous vasodilatation in formerly hypercholesterolaemic older adults by increasing end‐organ responsiveness to sympathetic outflow during passive heat stress.

    

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