Schad Oliver, Heidenreich Julius Frederik, Petri Nils, Kleineisel Jonas, Sauer Simon, Bley Thorsten Alexander, Nordbeck Peter, Petritsch Bernhard, Wech Tobias
Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany.
Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany.
Magn Reson Med. 2025 Oct;94(4):1731-1749. doi: 10.1002/mrm.30572. Epub 2025 Jun 16.
Electrocardiogram (ECG)-gated cine imaging in breath-hold enables high-quality diagnostics in most patients but can be compromised by arrhythmia and inability to hold breath. Real-time cardiac MRI offers faster and robust exams without these limitations. To achieve sufficient acceleration, advanced reconstruction methods, which transfer data into high-quality images, are required.
In this study, undersampled spiral balanced SSFP (bSSFP) real-time data in free-breathing were acquired at 1.5T in 16 healthy volunteers and five arrhythmic patients, with ECG-gated Cartesian cine in breath-hold serving as clinical reference. Image reconstructions were performed using a tailored and specifically trained score-based diffusion model, compared to a variational network and different compressed sensing approaches. The techniques were assessed using an expert reader study, scalar metric calculations, difference images against a segmented reference, and Bland-Altman analysis of cardiac functional parameters.
In participants with irregular RR-cycles, spiral real-time acquisitions showed superior image quality compared to the clinical reference. Quantitative and qualitative metrics indicate enhanced image quality of the diffusion model in comparison to the alternative reconstruction methods, although improvements over the variational network were minor. Slightly higher ejection fractions for the real-time diffusion reconstructions were exhibited relative to the clinical references with a bias of 1.1 ± 5.7% for healthy subjects.
The proposed real-time technique enables free-breathing acquisitions of spatio-temporal images with high quality, covering the entire heart in less than 1 min. Evaluation of ejection fraction using the ECG-gated reference can be vulnerable to arrhythmia and averaging effects, highlighting the need for real-time approaches. Prolonged inference times and stochastic variability of the diffusion reconstruction represent obstacles to overcome for clinical translation.
屏气状态下的心电图（ECG）门控电影成像能够为大多数患者提供高质量诊断，但可能会因心律失常和无法屏气而受到影响。实时心脏磁共振成像提供了更快且更可靠的检查，不存在这些限制。为了实现足够的加速，需要先进的重建方法将数据转换为高质量图像。
在本研究中，在1.5T场强下，对16名健康志愿者和5名心律失常患者进行了自由呼吸状态下欠采样螺旋平衡稳态自由进动（bSSFP）实时数据采集，以屏气状态下的ECG门控笛卡尔电影成像作为临床参考。使用定制的、经过专门训练的基于分数的扩散模型进行图像重建，并与变分网络和不同的压缩感知方法进行比较。通过专家阅片研究、标量指标计算、与分割参考的差异图像以及心脏功能参数的Bland-Altman分析对这些技术进行评估。
在RR周期不规则的参与者中，螺旋实时采集的图像质量优于临床参考。定量和定性指标表明，与其他重建方法相比，扩散模型的图像质量有所提高，尽管相对于变分网络的改进较小。实时扩散重建的射血分数相对于临床参考略高，健康受试者的偏差为1.1±5.7%。
所提出的实时技术能够在自由呼吸状态下高质量采集时空图像，在不到1分钟的时间内覆盖整个心脏。使用ECG门控参考评估射血分数可能容易受到心律失常和平均效应的影响，凸显了实时方法的必要性。扩散重建的推理时间延长和随机变异性是临床转化需要克服的障碍。
