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. 2021 May;85(5):2709-2722.
doi: 10.1002/mrm.28626. Epub 2020 Dec 7.

Measuring pulmonary gas exchange using compartment-selective xenon-polarization transfer contrast (XTC) MRI

Faraz Amzajerdian  1   2 , Kai Ruppert  1 , Hooman Hamedani  1   2 , Ryan Baron  1 , Yi Xin  1   2 , Luis Loza  1 , Tahmina Achekzai  1 , Ian F Duncan  1 , Yiwen Qian  1   2 , Mehrdad Pourfathi  1 , Stephen Kadlecek  1 , Rahim R Rizi  1
Affiliations

Measuring pulmonary gas exchange using compartment-selective xenon-polarization transfer contrast (XTC) MRI

Faraz Amzajerdian et al. Magn Reson Med. 2021 May.

Abstract

Purpose: To demonstrate the feasibility of generating red blood cell (RBC) and tissue/plasma (TP)-specific gas-phase (GP) depolarization maps using xenon-polarization transfer contrast (XTC) MR imaging.

Methods: Imaging was performed in three healthy subjects, an asymptomatic smoker, and a chronic obstructive pulmonary disease (COPD) patient. Single-breath XTC data were acquired through a series of three GP images using a 2D multi-slice GRE during a 12 s breath-hold. A series of 8 ms Gaussian inversion pulses spaced 30 ms apart were applied in-between the images to quantify the exchange between the GP and dissolved-phase (DP) compartments. Inversion pulses were either centered on-resonance to generate contrast, or off-resonance to correct for other sources of signal loss. For an alternative scheme, inversions of both RBC and TP resonances were inserted in lieu of off-resonance pulses. Finally, this technique was extended to a multi-breath protocol consistent with tidal breathing, involving 30 consecutive acquisitions.

Results: Inversion pulses shifted off-resonance by 20 ppm to mimic the distance between the RBC and TP resonances demonstrated selectivity, and initial GP depolarization maps illustrated stark magnitude and distribution differences between healthy and diseased subjects that were consistent with traditional approaches.

Conclusion: The proposed DP-compartment selective XTC MRI technique provides information on gas exchange between all three detectable states of xenon in the lungs and is sufficiently sensitive to indicate differences in lung function between the study subjects. Investigated extensions of this approach to imaging schemes that either minimize breath-hold duration or the overall number of breath-holds open avenues for future research to improve measurement accuracy and patient comfort.

Keywords: XTC; dissolved-phase imaging; hyperpolarized xenon-129; lung MRI; xenon-polarization transfer contrast.

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Figures

Figure 1.
Figure 1.
(A) Schematic of a multi-breath XTC acquisition. The wash-ins allow adequate signal build-up and distribution for imaging, while the wash-outs ensure that no signal remains between the sets. The first set of acquisitions does not contain inversion pulses to account for T1 decay effects. For the second and third sets, inversion pulses are centered on either the RBC (218 ppm) or TP (198 ppm) resonance, as in the single-breath acquisition. (B) Representative inhale and exhale flows illustrating the free-breathing maneuver from the multi-breath protocol.
Figure 2.
Figure 2.
Schematic of a single-breath XTC image acquisition. A series of N inversion pulses are applied in-between three 2D multi-slice GP image sets (S1, S2, and S3). In order to maximize available signal, the first set of pulses was centered off-resonance (−218 or 198 ppm) to account for signal loss due to T1 decay, HXe removal via blood flow, or potential effects of the inversion pulses on the GP resonance, while the second set of pulses was centered on either the RBC (218 ppm) or TP (198 ppm) resonance to generate exchange-weighted contrast. The phase of the contrast-generating RF pulses was alternated between 0° and 180° to minimize the impact of regional B1 inhomogeneities.
Figure 3.
Figure 3.
Coronal fD maps from most anterior (A) to most posterior (P) in a healthy subject (H1) with inversion pulses centered at 178, 198, 218, and 238 ppm, demonstrating the selectivity of the inversion pulse profile.
Figure 4.
Figure 4.
Coronal TP:GP depolarization maps for a healthy volunteer, the asymptomatic smoker, and the COPD subject.
Figure 5.
Figure 5.
Coronal RBC:GP depolarization maps for a healthy volunteer, the asymptomatic smoker, and the COPD subject.
Figure 6.
Figure 6.
(A) Coronal projections of the RBC:TP depolarization ratio maps for a healthy volunteer, the asymptomatic smoker, and the COPD subject. (B) Plot of the mean RBC:TP depolarization ratio values for the left lung, right lung, and whole lung in each slice for each subject, from anterior to posterior.
Figure 7.
Figure 7.
Axial maps from a healthy volunteer (H3) based on a central slice through the lung. The top row depicts the T1-corrected TP:GP and RBC:GP depolarization maps generated from two separate breath-holds and the resulting RBC:TP depolarization ratio map. The bottom row shows the same type of maps as the row above, but generated from a single breath-hold measurement and uncorrected for T1 decay, with the off-resonance control RF pulse between S1 and S2 replaced by a second set of inversion pulses centered on the other DP resonance.
Figure 8.
Figure 8.
Coronal TP:GP and RBC:GP depolarization and RBC:TP depolarization ratio maps acquired with the multi-breath protocol in a healthy volunteer (H2).
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References

    1. Driehuys B, Martinez-Jimenez S, Cleveland ZI, et al. Chronic Obstructive Pulmonary Disease: Safety and Tolerability of Hyperpolarized 129Xe MR Imaging in Healthy Volunteers and Patients. Radiology. 2012;262(1):279–289. - PMC - PubMed
    1. Kirby M, Svenningsen S, Owrangi A, et al. Hyperpolarized 3He and 129Xe MR Imaging in Healthy Volunteers and Patients with Chronic Obstructive Pulmonary Disease. Radiology. 2012;265(2):600–610. - PubMed
    1. Salerno M, Altes TA, Mugler JP, Nakatsu M, Hatabu H, de Lange EE. Hyperpolarized noble gas MR imaging of the lung: Potential clinical applications. Eur J Radiol. 2001;40(1):33–44. - PubMed
    1. Virgincar RS, Cleveland ZI, Kaushik SS, et al. Quantitative analysis of hyperpolarized 129Xe ventilation imaging in healthy volunteers and subjects with chronic obstructive pulmonary disease. NMR Biomed. 2013;26(4):424–435. - PMC - PubMed
    1. Walkup LL, Thomen RP, Akinyi TG, et al. Feasibility, tolerability and safety of pediatric hyperpolarized 129Xe magnetic resonance imaging in healthy volunteers and children with cystic fibrosis. Pediatr Radiol. 2016;46(12):1651–1662. - PMC - PubMed

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