Instituto de Sistemas e Robótica - Lisboa and Departamento de Bioengenharia, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
Hospital da Luz Learning Health, Luz Saúde, Lisbon, Portugal.
Magn Reson Med. 2023 Aug;90(2):539-551. doi: 10.1002/mrm.29661. Epub 2023 Apr 10.
Enabling fast and accessible myocardial T mapping is crucial for extending its clinical application. We introduce Open-MOLLI-SMS combining simultaneous multi-slice (SMS) with auto-calibration and variable-rate selective excitation (VERSE)-multiband pulses to obtain all slices in a fast single-shot T mapping sequence.
Open-MOLLI-SMS was developed by integrating SMS with the open-source method Open-MOLLI previously implemented in Pulseq. Three methods were integrated for Open-MOLLI-SMS: (1) auto-calibration blip patterns to ensure consistency between the data and coil information; (2) a blipped-balanced SSFP (bSSFP) readout to induce controlled aliasing in parallel imaging shifts without disturbing the bSSFP frequency response; and (3) a VERSE-multiband pulse for minimizing the achievable TR and the specific absortion rate (SAR) impact of SMS. Two (SMS2) or three (SMS3) slices were excited simultaneously and encoded with an in-plane acceleration factor of 2. Experiments were performed in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom and five healthy volunteers.
Phantom results show accurate T estimates for reference values between 400 to 2200 ms. Artifacts were visible for Open-MOLLI-SMS3 but not replicated in vivo. In vivo Open-MOLLI-SMS (T = 993 ± 10 ms; T = 1031 ± 17 ms) provided similar values to mean T single-band Open-MOLLI estimates (T = 1005 ± 47 ms). Open-MOLLI-SMS2 provided the closest estimates to the reference.
This proof-of-principle implementation study demonstrates the feasibility of speeding up T -mapping acquisitions and increasing coverage by combining auto-calibration strategies with a blipped-bSFFP readout and VERSE multiband RF excitation pulses. The proposed methodology was built on the Open-MOLLI mapping sequence, which provides a fast means for prototyping and enables open-source sharing of the method.
实现快速、便捷的心肌 T 映射对于扩展其临床应用至关重要。我们介绍了结合同时多层（SMS）与自动校准和变速选择性激发（VERSE）-多带脉冲的 Open-MOLLI-SMS，以在快速单次 T 映射序列中获得所有切片。
Open-MOLLI-SMS 通过将 SMS 与以前在 Pulseq 中实现的开源方法 Open-MOLLI 集成来开发。Open-MOLLI-SMS 集成了三种方法：（1）自动校准信标点图案，以确保数据与线圈信息之间的一致性；（2）使用带有平衡闪烁的稳态自由进动（bSSFP）读出，在不干扰 bSSFP 频率响应的情况下在并行成像偏移中诱导受控混叠；（3）使用 VERSE 多带脉冲来最小化 SMS 的可实现 TR 和特定吸收率（SAR）的影响。同时激发两个（SMS2）或三个（SMS3）切片，并在平面内以 2 的加速因子进行编码。实验在国际磁共振医学学会/国家标准与技术研究院体模和五名健康志愿者中进行。
体模结果显示，对于 400 至 2200 ms 的参考值，T 估计值准确。Open-MOLLI-SMS3 可见伪影，但在体内未复制。体内 Open-MOLLI-SMS（T = 993 ± 10 ms；T = 1031 ± 17 ms）提供的数值与平均 T 单带 Open-MOLLI 估计值（T = 1005 ± 47 ms）相似。Open-MOLLI-SMS2 提供了最接近参考值的估计值。
这项原理验证实施研究证明了通过将自动校准策略与带闪烁的 bSFFP 读出和 VERSE 多带 RF 激发脉冲相结合，加快 T 映射采集并增加覆盖范围的可行性。所提出的方法基于 Open-MOLLI 映射序列，该序列为原型设计提供了快速手段，并实现了方法的开源共享。
