Magnetic resonance multitasking for multidimensional assessment of cardiovascular system: Development and feasibility study on the thoracic aorta

Abstract

Purpose To develop an MR multitasking‐based multidimensional assessment of cardiovascular system (MT‐MACS) with electrocardiography‐free and navigator‐free data acquisition for a comprehensive evaluation of thoracic aortic diseases. Methods The MT‐MACS technique adopts a low‐rank tensor image model with a cardiac time dimension for phase‐resolved cine imaging and a T2‐prepared inversion‐recovery dimension for multicontrast assessment. Twelve healthy subjects and 2 patients with thoracic aortic diseases were recruited for the study at 3 T, and both qualitative (image quality score) and quantitative (contrast‐to‐noise ratio between lumen and wall, lumen and wall area, and aortic strain index) analyses were performed in all healthy subjects. The overall image quality was scored based on a 4‐point scale: 3, excellent; 2, good; 1, fair; and 0, poor. Statistical analysis was used to test the measurement agreement between MT‐MACS and its corresponding 2D references. Results The MT‐MACS images reconstructed from acquisitions as short as 6 minutes demonstrated good or excellent image quality for bright‐blood (2.58 ± 0.46), dark‐blood (2.58 ± 0.50), and gray‐blood (2.17 ± 0.53) contrast weightings, respectively. The contrast‐to‐noise ratios for the three weightings were 49.2 ± 12.8, 20.0 ± 5.8 and 2.8 ± 1.8, respectively. There were good agreements in the lumen and wall area (intraclass correlation coefficient = 0.993, P < .001 for lumen; intraclass correlation coefficient = 0.969, P < .001 for wall area) and strain (intraclass correlation coefficient = 0.947, P < .001) between MT‐MACS and conventional 2D sequences. Conclusion The MT‐MACS technique provides high‐quality, multidimensional images for a comprehensive assessment of the thoracic aorta. Technical feasibility was demonstrated in healthy subjects and patients with thoracic aortic diseases. Further clinical validation is warranted.

Three‐dimensional multicontrast blood imaging with a single acquisition: Simultaneous non‐contrast‐enhanced MRA and vessel wall imaging in the thoracic aorta

“…The measurement of lumen area (LA) and wall area (WA) was adopted from a previous publication 24,35 . For the accuracy analysis of LA and WA measurements, the images acquired with two sequences were reconstructed to be cross‐sectional perpendicular to the ascending and descending aorta.…”

“…Imaging parameters of the pulse sequences used in the present study The measurement of lumen area (LA) and wall area (WA) was adopted from a previous publication. 24,35 For the accuracy analysis of LA and WA measurements, the images acquired with two sequences were reconstructed to be cross-sectional perpendicular to the ascending and descending aorta. The inner and outer boundaries of the vessel wall on all the cross-sectional slices were manually traced by two radiologists.…”

Black‐Blood Contrast in Cardiovascular MRI

“…This approach exploits the relatively slowly varying nature of the MR signal along certain dimensions (eg, T 1 relaxation, cardiac and respiratory motion). Using a low‐rank tensor image model, highly undersampled images can be reconstructed at arbitrary timepoints on the inversion recovery curve for a certain cardiac and respiratory phase, such as at the zero‐crossing of the blood M z , yielding black‐blood contrast 144 . A unique property of this technique is the ability to obtain time‐resolved black‐blood images that is typically limited to bright‐blood techniques.…”

Using 5D flow MRI to decode the effects of rhythm on left atrial 3D flow dynamics in patients with atrial fibrillation

“…Recent explorations into multi-dimensional and self-gated imaging have pushed the boundaries of "conventional" cardiac imaging towards more efficient scan times and operator ease-of-use. [14][15][16][17][18][19][20][21][22][23][24] Recently, a fully self-gated free-running 5D flow framework was introduced. 19,21,23,25,26 This framework featured a continuous, free-running, 3D radial sequence, with interleaved three-directional velocity encoding as well as inherent self-gating projections to encode cardiac and respiratory motion without external gating signals.…”

“…However, current techniques are suboptimal in this context, as 4D flow techniques average data over multiple heart cycles, which prevents investigation of the effects of arrhythmic heartbeats and variable RR‐interval on atrial flow characteristics. Recent explorations into multi‐dimensional and self‐gated imaging have pushed the boundaries of “conventional” cardiac imaging towards more efficient scan times and operator ease‐of‐use 14‐24 …”