3D model-based super-resolution motion-corrected cardiac T1 mapping

Abstract

Objective: To provide 3D high-resolution cardiac T1 maps using model-based super-resolution reconstruction (SRR). Approach: Due to signal-to-noise ratio (SNR) limitations and the motion of the heart during imaging, often 2D T1 maps with only low through-plane resolution (i.e. slice thickness of 6 to 8 mm) can be obtained. Here, a model-based SRR approach is presented, which combines multiple stacks of 2D acquisitions with 6 to 8 mm slice thickness and generates 3D high-resolution T1 maps with a slice thickness of 1.5 to 2 mm. Every stack was acquired in a different breath hold (BH) and any misalignment between BH was corrected retrospectively. The novelty of the proposed approach is the BH correction and the application of model-based SRR on cardiac T1 Mapping. The proposed approach was evaluated in numerical simulations and phantom experiments and demonstrated in four healthy subjects. Main results: Alignment of BH states was essential for SRR even in healthy volunteers. In simulations, respiratory motion could be estimated with an RMS error of 0.18 ± 0.28 mm. SRR improved the visualization of small structures. High accuracy and precision (average standard deviation of 69.62 ms) of the T1 values was ensured by SRR while the detectability of small structures increased by 40%. Significance: The proposed SRR approach provided T1 maps with high in-plane and high through-plane resolution (1.3×1.3×1.5 to 2 mm³). The approach led to improvements in the visualization of small structures and precise T1 values.

3D whole heart k-space-based super-resolution cardiac T1 mapping using rotated stacks

“…Since the non-smoothness of the L1-norm, as well as the non-linear function q, make solving problem 4 challenging, a variable splitting (Wang et al 2008, Bano et al 2020, Corona et al 2021, Hufnagel et al 2022 approach was used: Auxiliary variables ≔ ( ) G w q t t for all t and ≔ G n were introduced, and these equalities were relaxed by including two quadratic penalty terms, weighted by a and b. This yielded equation (5): A .…”

“…As nomenclature, the HR SRR result will in the following be denoted by SRR and a LR map by LR. The subscript then describes the geometry of the SRR acquisition (rot for rotated or transl for translated (Hufnagel et al 2022)), and the superscript the type of SRR reconstruction (i for image-space based (Hufnagel et al 2022) or k for k-space-based). So, the proposed method yielded SRR k rot .…”

“…In quantitative imaging, model-based SRR incorporates the knowledge about the signal model (for example T1 relaxation) and data acquisition model into the optimization. Commonly (Van Steenkiste et al 2016, Van Steenkiste et al 2017, Beirinckx et al 2020, Hufnagel et al 2022, image-space-based SRR is used, where the LR images are reconstructed in an initial step, then serve as a starting point for the SRR and the difference between the acquired LR dynamics and those predicted from the SRR result is minimized. Others (Bano et al 2020, Corona et al 2021) used a k-space-based SRR approach, minimising the difference between the acquired k-space data and the one predicted from the SRR result.…”

“…In addition to limited spatial resolution, the coverage of the entire heart is another challenge for cardiac SRR. Previous image-space-based cardiac T1 mapping SRR methods (Hufnagel et al 2022) used LR stacks in short-axis orientation (SAX), which were shifted to each other to improve resolution along the SE direction but could only cover the ventricles. So far, whole-heart T1 mapping with high isotropic resolution (below or equal to 1.5 mm) is only possible with long acquisition times (>9 min) (Milotta et al 2020, Nordio et al 2020, Qi et al 2019a, Qi et al 2019b, Phair et al 2023.…”

Kardiovaskuläre MRT: akute Myokarditis und myokardiale Mitbeteiligung bei Systemerkrankungen

“…Trotzdem ist es insbesondere bei den quantitativen Techniken notwendig, Normwerte entsprechend den spezifischen Bedingungen zu verwenden. In der Zukunft ist zu erwarten, dass sich schnellere und genauere Techniken etablieren werden, da eine Vielzahl von Physikern in enger Kooperation mit Klinikern an der ständigen Weiterentwicklung der CMR arbeitet [41,42].…”