A decay‐modeled compressed sensing reconstruction approach for non‐Cartesian hyperpolarized 129Xe MRI

• Published in: Magnetic resonance in medicine 2024-10, Vol.92 (4), p.1363-1375
• Main Authors: Plummer, Joseph W, Hussain, Riaz, Bdaiwi, Abdullah S, Soderlund, Stephanie A, Hoyos, Xavier, Lanier, John M, Garrison, William J, Juan Parra‐Robles, Willmering, Matthew M, Niedbalski, Peter J, Cleveland, Zackary I, Walkup, Laura L
• Format: Article
• Language: English
• Subjects: Accuracy; Cartesian coordinates; Compressed gas; Data exchange; Decay; Image acquisition; Image contrast; Image processing; Image quality; Image reconstruction; Iterative methods; Magnetic resonance imaging; Magnetization; Sharpness; Ventilation; Xenon 129
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.30188

PurposeHyperpolarized 129Xe MRI benefits from non‐Cartesian acquisitions that sample k‐space efficiently and rapidly. However, their reconstructions are complex and burdened by decay processes unique to hyperpolarized gas. Currently used gridded reconstructions are prone to artifacts caused by magnetization decay and are ill‐suited for undersampling. We present a compressed sensing (CS) reconstruction approach that incorporates magnetization decay in the forward model, thereby producing images with increased sharpness and contrast, even in undersampled data.MethodsRadio‐frequency, T1, and T2*$$ {\mathrm{T}}_2^{\ast } $$ decay processes were incorporated into the forward model and solved using iterative methods including CS. The decay‐modeled reconstruction was validated in simulations and then tested in 2D/3D‐spiral ventilation and 3D‐radial gas‐exchange MRI. Quantitative metrics including apparent‐SNR and sharpness were compared between gridded, CS, and twofold undersampled CS reconstructions. Observations were validated in gas‐exchange data collected from 15 healthy and 25 post‐hematopoietic‐stem‐cell‐transplant participants.ResultsCS reconstructions in simulations yielded images with threefold increases in accuracy. CS increased sharpness and contrast for ventilation in vivo imaging and showed greater accuracy for undersampled acquisitions. CS improved gas‐exchange imaging, particularly in the dissolved‐phase where apparent‐SNR improved, and structure was made discernable. Finally, CS showed repeatability in important global gas‐exchange metrics including median dissolved‐gas signal ratio and median angle between real/imaginary components.ConclusionA non‐Cartesian CS reconstruction approach that incorporates hyperpolarized 129Xe decay processes is presented. This approach enables improved image sharpness, contrast, and overall image quality in addition to up‐to threefold undersampling. This contribution benefits all hyperpolarized gas MRI through improved accuracy and decreased scan durations.