Simultaneous multi‐slice cardiac cine with Fourier‐encoded self‐calibration at 7 Tesla

Purpose:To develop a 2D radial multislice MP2RAGE sequence for fast and reliable T 1 mapping at 7 T in mice and for MR thermometry. Methods: The 2D-MP2RAGE sequence was performed with the following parameters: TI 1 -TI 2 -MP2RAGE TR = 1000-3000-9000 ms. The multiple dead times within the sequence were used for interleaved multislice acquisition, enabling one to acquire six slices in 9 seconds. The excitation pulse shape, inversion selectivity, and interslice gap were optimized. In vitro comparison with the inversion-recovery sequence was performed. The T 1 variations with temperature were measured on tubes with T 1 ranging from 800 ms to 2000 ms. The sequence was used to acquire T 1 maps continuously during 30 minutes on the brain and abdomen of healthy mice. Results: A three-lobe cardinal sine excitation pulse, combined with an inversion slice thickness and an interslice gap of respectively 150% and 50% of the imaging slice thickness, led to a SD and bias of the T 1 measurements below 1% and 2%, respectively. A linear dependence of T 1 with temperature was measured between 10°C and 60°C. In vivo, less than 1% variation was measured between successive T 1 maps in the mouse brain. In the abdomen, no obvious in-plane motion artifacts were observed but respiratory motion in the slice dimension led to 6% T 1 underestimation. Conclusion: The multislice MP2RAGE sequence could be used for fast wholebody T 1 mapping and MR thermometry. Its reconstruction method would enable onthe-fly reconstruction.

Section: Discussionmentioning

confidence: 99%

2D multislice MP2RAGE sequence for fast T₁ mapping at 7 T: Application to mouse imaging and MR thermometry

Faller

Trotier

Rousseau

et al. 2020

“…A prospectively electrocardiographic-triggered cardiac PC 2D cine MR sequence with three-directional velocity encoding 30 was extended to include k-t acceleration 13 and autocalibrated MB CAIPIRINHA. 28,29 This combination is not straightforward, because for each technique certain conditions with respect to the sampling patterns and the RF phases have to be fulfilled. Before presenting the rationale for the combination of the two techniques, a brief introduction to autocalibrated MB CAIPIRINHA and k-t acceleration is provided.…”

Section: Sequence Descriptionmentioning

confidence: 99%

“…The benefits of MB have been demonstrated in cardiac MRI, [19][20][21][22][23][24][25][26][27] and the technique was recently extended to TPM with one-directional velocity encoding. 28 Two recent studies have also demonstrated the benefit of autocalibrated MB, 28,29 a variant of MB-CAIPIRINHA encoding that does not require external reference scans for the reconstruction, thus limiting the number of required breath-holds to only one.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Autocalibrated cardiac tissue phase mapping with multiband imaging and k‐t acceleration

Ferrazzi

Bassenge

Mayer

et al. 2020

Purpose To develop an autocalibrated multiband (MB) CAIPIRINHA acquisition scheme with in‐plane k‐t acceleration enabling multislice three‐directional tissue phase mapping in one breath‐hold. Methods A k‐t undersampling scheme was integrated into a time‐resolved electrocardiographic‐triggered autocalibrated MB gradient‐echo sequence. The sequence was used to acquire data on 4 healthy volunteers with MB factors of two (MB2) and three (MB3), which were reconstructed using a joint reconstruction algorithm that tackles both k‐t and MB acceleration. Forward simulations of the imaging process were used to tune the reconstruction model hyperparameters. Direct comparisons between MB and single‐band tissue phase‐mapping measurements were performed. Results Simulations showed that the velocities could be accurately reproduced with MB2 k‐t (average ± twice the SD of the RMS error of 0.08 ± 0.22 cm/s and velocity peak reduction of 1.03% ± 6.47% compared with fully sampled velocities), whereas acceptable results were obtained with MB3 k‐t (RMS error of 0.13 ± 0.58 cm/s and peak reduction of 2.21% ± 13.45%). When applied to tissue phase‐mapping data, the proposed technique allowed three‐directional velocity encoding to be simultaneously acquired at two/three slices in a single breath‐hold of 18 heartbeats. No statistically significant differences were detected between MB2/MB3 k‐t and single‐band k‐t motion traces averaged over the myocardium. Regional differences were found, however, when using the American Heart Association model for segmentation. Conclusion An autocalibrated MB k‐t acquisition/reconstruction framework is presented that allows three‐directional velocity encoding of the myocardial velocities at multiple slices in one breath‐hold.

“…This suggests that g-factor noise enhancement with appropriate CAIPIRINHA shifting of slices will not be the limiting factor on multiband acceleration in cardiac bSSFP. Although MB2 acceleration has negligible impact on image quality, residual unfolding artefacts begin to appear with higher MB factors (3)(4), predominantly effecting the basal slices. These are more evident Figure 5, the mean and [max] value increased from 1.13 [2.20] to 1.46 [3.63]).…”

Section: In Vivo Evaluation Of Frequency Responsementioning

confidence: 99%

Simultaneous multislice imaging of the heart using multiband balanced SSFP with blipped‐CAIPI

Price

Cordero‐Grande

Malik

et al. 2019

Purpose In this work, we explore the use of multiband (MB) balanced steady‐state free precession (bSSFP) with blipped‐controlled aliasing in parallel imaging (CAIPI), which avoids the issues of altered frequency response associated with RF phase cycling, and show its application to accelerating cardiac cine imaging. Methods Blipped and RF‐cycled CAIPI were implemented into a retrospective‐gated segmented cine multiband bSSFP sequence. The 2 methods were compared at 3T using MB2 to demonstrate the effect on frequency response. Further data (4 subjects) were acquired at both 1.5T and 3T collecting 12‐slice short axis stacks using blipped‐CAIPI with MB acceleration factors of 1–4. The impact on SNR and contrast was evaluated along with g‐factors at different accelerations. Results Data acquired with blipped‐CAIPI multiband bSSFP up to factor 4 yielded functional cine data with good SNR and contrast, while reliably keeping dark‐band artefacts clear of the heart at 1.5T. SAR limits the maximum MB acceleration, particularly at 3T, where minimum TR increase is problematic and leakage artefacts are more prevalent. Mean g‐factors across the heart were measured at 1.00, 1.06, and 1.12 for MB2–MB4, whereas blood‐pool SNR measures (end‐diastole) decreased by 11.8, 21.5, and 36.9%; ultimately LV‐myocardium CNR remained sufficient at 1.5T with values ranging: 15.6, 13.4, 11.9, and 9.6 (MB1–MB4). Conclusion Blipped‐CAIPI multiband bSSFP can be used in cardiovascular applications without affecting the frequency response because of controlled aliasing and can be readily incorporated into segmented cine acquisitions without adding any additional constraints because of phase cycling requirements. The method was used to collect full ventricular coverage within a single breath‐hold.