Department of Radiology, Northshore University HealthSystem, Evanston, IL, USA.
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
J Cardiovasc Magn Reson. 2021 Nov 1;23(1):127. doi: 10.1186/s12968-021-00808-2.
Recently, we reported a novel neuroimaging technique, unbalanced T1 Relaxation-Enhanced Steady-State (uTRESS), which uses a tailored 3D unbalanced steady-state free precession (3D uSSFP) acquisition to suppress the blood pool signal while minimizing bulk motion sensitivity. In the present work, we hypothesized that 3D uSSFP might also be useful for dark blood imaging of the chest. To test the feasibility of this approach, we performed a pilot study in healthy subjects and patients undergoing cardiovascular magnetic resonance (CMR).
The study was approved by the hospital institutional review board. Thirty-one adult subjects were imaged at 1.5 T, including 5 healthy adult subjects and 26 patients (44 to 86 years, 10 female) undergoing a clinically indicated CMR. Breath-holding was used in 29 subjects and navigator gating in 2 subjects. For breath-hold acquisitions, the 3D uSSFP pulse sequence used a high sampling bandwidth, asymmetric readout, and single-shot along the phase-encoding direction, while 3 shots were acquired for navigator-gated scans. To minimize signal dephasing from bulk motion, electrocardiographic (ECG) gating was used to synchronize the data acquisition to the diastolic phase of the cardiac cycle. To further reduce motion sensitivity, the moment of the dephasing gradient was set to one-fifth of the moment of the readout gradient. Image quality using 3D uSSFP was good-to-excellent in all subjects. The blood pool signal in the thoracic aorta was uniformly suppressed with sharp delineation of the aortic wall including two cases of ascending aortic aneurysm and two cases of aortic dissection. Compared with variable flip angle 3D turbo spin-echo, 3D uSSFP showed improved aortic wall sharpness. It was also more efficient, permitting the acquisition of 24 slices in each breath-hold versus 16 slices with 3D turbo spin-echo and a single slice with dual inversion 2D turbo spin-echo. In addition, lung and mediastinal lesions appeared highly conspicuous compared with the low blood pool signals within the heart and blood vessels. In two subjects, navigator-gated 3D uSSFP provided excellent delineation of cardiac morphology in double oblique multiplanar reformations.
In this pilot study, we have demonstrated the feasibility of using ECG-gated 3D uSSFP for dark blood imaging of the heart, great vessels, and lungs. Further study will be required to fully optimize the technique and to assess clinical utility.
最近，我们报道了一种新的神经影像学技术，不平衡 T1 弛豫增强稳态（uTRESS），它使用定制的 3D 不平衡稳态自由进动（3D uSSFP）采集来抑制血池信号，同时最小化整体运动敏感性。在本研究中，我们假设 3D uSSFP 也可能对胸部的黑血成像有用。为了测试这种方法的可行性，我们在健康受试者和接受心血管磁共振（CMR）的患者中进行了一项试点研究。
该研究得到了医院机构审查委员会的批准。在 1.5T 下对 31 名成年受试者进行成像，包括 5 名健康成年受试者和 26 名患者（44 至 86 岁，10 名女性），他们接受了临床指征的 CMR。29 名受试者进行屏气采集，2 名受试者进行导航门控采集。对于屏气采集，3D uSSFP 脉冲序列使用高采样带宽、非对称读出和沿相位编码方向的单次激发，而导航门控扫描采集 3 次。为了最小化整体运动引起的信号去相位，使用心电图（ECG）门控将数据采集与心脏周期的舒张期同步。为了进一步降低运动敏感性，将去相位梯度的力矩设置为读出梯度的力矩的五分之一。所有受试者的 3D uSSFP 图像质量均良好至优秀。胸主动脉的血池信号均匀抑制，主动脉壁轮廓锐利，包括 2 例升主动脉瘤和 2 例主动脉夹层。与可变翻转角 3D 涡轮自旋回波相比，3D uSSFP 显示出更好的主动脉壁锐利度。它也更高效，允许在每次屏气采集 24 个切片，而 3D 涡轮自旋回波采集 16 个切片，双反转 2D 涡轮自旋回波采集 1 个切片。此外，与心脏和血管内的低血池信号相比，肺部和纵隔病变显得非常明显。在 2 名受试者中，导航门控 3D uSSFP 在双斜多平面重建中提供了出色的心脏形态描绘。
在这项试点研究中，我们已经证明了 ECG 门控 3D uSSFP 用于心脏、大血管和肺部黑血成像的可行性。需要进一步研究以充分优化该技术并评估其临床应用价值。
