Free-breathing Pulmonary Relaxometry at 0.55T
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Published on: November 10, 2023
Pavlos Panos1, Oliver Bieri1, Maurice Pradella2
1Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland; Department of Radiology, Division of Radiological Physics, University Hospital Basel, Basel, Switzerland.
Purpose:
To evaluate the feasibility of an integrated, free-breathing workflow for automated 2D pulmonary relaxometry (T1, T2) at 0.55T.
Methods:
A 2D inversion recovery balanced steady-state free precession (IR-bSSFP) sequence was adapted to achieve high-temporal sampling of its transient phase at 0.55T. IR-bSSFP relaxometry was validated in manganese-doped phantoms using reference methods and tested in eight healthy volunteers as well as one patient. A fully automated pipeline was developed, featuring multi-contrast registration for motion correction and deep learning-based lung segmentation to enable voxel-wise nonlinear fitting for T1 and T2 map generation.
Results:
Phantom results were in agreement with reference scans. The proposed free-breathing framework effectively mitigated respiratory motion, yielding quantitative maps in close agreement with breath-hold references. Average healthy lung parenchyma relaxation times were T1 = (920 ± 40)ms and T2 = (90 ± 8)ms. In a patient case, the method successfully distinguished a solid lung mass from surrounding parenchyma, with the lesion showing elevated T1 (950 vs 800ms in the surrounding parenchyma).
Conclusions:
Simultaneous free-breathing T1 and T2 mapping of the lung is feasible at 0.55T using a fully automated pipeline. By eliminating breath-holds and external gating, this approach may improve patient compliance, demonstrating technical feasibility in a clinical setting and offering potential for future clinical evaluation.
