Prospective correction of patient-specific respiratory motion in myocardial T₁ and T₂ mapping

Respiratory motion in cardiovascular MRI presents a challenging problem with many potential solutions. Current approaches require breath-holds, apply retrospective image registration, or significantly increase scan time by respiratory gating. Myocardial T₁ and T₂ mapping techniques are particularly sensitive to motion as they require multiple source images to be accurately aligned prior to the estimation of tissue relaxation. We propose a patient-specific prospective motion correction (PROCO) strategy that corrects respiratory motion on the fly with the goal of reducing the spatial variation of myocardial parametric mapping techniques.

A rapid, patient-specific training scan was performed to characterize respiration-induced motion of the heart relative to a diaphragmatic navigator, and a parametric mapping pulse sequence utilized the resulting motion model to prospectively update the scan plane in real-time. Midventricular short-axis T₁ and T₂ maps were acquired under breath-hold or free-breathing conditions with and without PROCO in 7 healthy volunteers and 3 patients. T₁ and T₂ were measured in 6 segments and compared to reference standard breath-hold measurements using Bland-Altman analysis.

PROCO significantly reduced the spatial variation of parametric maps acquired during free-breathing, producing limits of agreement of -47.16 to 30.98 ms (T₁ ) and -1.35 to 4.02 ms (T₂ ), compared to -67.77 to 74.34 ms (T₁ ) and -2.21 to 5.62 ms (T₂ ) for free-breathing acquisition without PROCO.

Patient-specific respiratory PROCO method significantly reduced the spatial variation of myocardial T₁ and T₂ mapping, while allowing for 100% efficient free-breathing acquisitions.