Accelerated interleaved spiral‐IDEAL imaging of hyperpolarized 129 Xe for parametric gas exchange mapping in humans

Self Cite

Purpose To assess the feasibility of hyperpolarized 129Xe multiple‐breath washout MRI in pediatric cystic fibrosis (CF) participants with preserved lung function. Fractional ventilation (r), defined as the fractional gas replacement per breath, was mapped using 2 signal models: (1) constant T1 and (2) variable T1 as a function of the hyperpolarized gas washout. Methods A total of 17 pediatric participants were recruited (mean age 11.7 ± 2.8 years), including 7 children with clinically stable CF and 10 aged‐matched healthy controls. Pulmonary function tests were performed, including spirometry, to measure the forced expiratory volume in 1 second and nitrogen multiple‐breath washout to measure the lung clearance index. Hyperpolarized 129Xe MRI was performed during consecutive breaths of air following a single 129Xe inhalation, and fractional ventilation maps were calculated. Results The forced expiratory volume in 1 second was similar in both groups (P = .32), but there was a statistically significant difference in lung clearance index between healthy and CF participants (P = .001). With variable T1 modeling, CF participants had a mean r of 0.44 ± 0.08 and healthy participants had a mean r of 0.37 ± 0.12 (P = .20). With constant T1 modeling, CF participants had a mean r′ of 0.48 ± 0.08, and healthy participants had a mean r′ of 0.43 ± 0.12 (P = .32). Therefore, assuming a constant T1 leads to a relative bias in r of 15.1% ± 6.4% and 20.8% ± 7.4% for CF and healthy participants, respectively (P = .12). Conclusion This study demonstrates that hyperpolarized 129Xe multiple‐breath washout imaging is feasible in pediatric participants with CF, and inclusion of variable T1 modeling reduces bias in the fractional ventilation measurements.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Assessing the feasibility of hyperpolarized ¹²⁹Xe multiple‐breath washout MRI in pediatric cystic fibrosis

Couch

Morgado

Kanhere

et al. 2019

Self Cite

“…Second, pulmonary physiological status was evaluated on the seventh day after the instillation; more time points should be added to investigate the evolution of injury caused by PM 2.5 . Third, as a concept‐of‐proof study, only whole‐lung gas exchange was measured using CSSR; however, dissolved xenon imaging techniques should also be added for visualizing the heterogeneity of gas exchange caused by PM 2.5 ‐related diseases in future studies . Also, the diffusing capacity of the lungs for carbon monoxide should be added in future studies to comprehensively evaluate changes in gas exchange function caused by PM 2.5 .…”

Section: Discussionmentioning

confidence: 99%

Quantitative evaluation of lung injury caused by PM_2.5 using hyperpolarized gas magnetic resonance

Zhang

et al. 2019

Purpose:To demonstrate the feasibility of 129 Xe MR in evaluating the pulmonary physiological changes caused by PM 2.5 in animal models. Methods: Six rats were treated with PM 2.5 solution (16.2 mg/kg) by intratracheal instillation twice a week for 4 weeks, and another six rats treated with normal saline served as the control cohort. Pulmonary function tests, hyperpolarized 129 Xe multi-b diffusion-weighted imaging, and chemical shift saturation recovery MR spectroscopy were performed on all rats, and the pulmonary structure and functional parameters were obtained from hyperpolarized 129 Xe MR data. Additionally, histological analysis was performed on all rats to evaluate alveolar septal thickness. Statistical analysis of all the obtained parameters was performed using unpaired 2-tailed t tests. Results: Compared with the control group, the measured exchange time constant increased from 11.74 ± 2.39 to 14.00 ± 2.84 ms (P < .05), and the septal wall thickness increased from 6.17 ± 0.48 to 6.74 ± 0.52 μm (P < .05) in the PM 2.5 cohort by 129 Xe MR spectroscopy, which correlated well with that obtained using quantitative histology (increased from 5.52 ± 0.32 to 6.20 ± 0.36 μm). Additionally, the mean TP/GAS ratio increased from 0.828 ± 0.115 to 1.019 ± 0.140 in the PM 2.5 cohort (P = .021). Conclusions: Hyperpolarized 129 Xe MR could quantify the changes in gas exchange physiology caused by PM 2.5 , indicating that the technique has the potential to be a useful tool for evaluation of pulmonary injury caused by air pollution in the future. K E Y W O R D Sair pollution, gas exchange, hyperpolarized 129 Xe, lung injury, PM 2.5 570 | ZHANG et Al.

“…AF = 10 (13 k‐space lines out of 128 per image) can be used for accelerated 129 Xe MRI morphometry measurements to reduce the slice thickness down to 15 mm and keep the breath‐hold time under the 16 s. The feasibility of the AF = 10 approach has been recently demonstrated for a single young healthy subject . The expected SNR loss of the short TE b = 0 image because of the smaller slice volume can be compensated using the larger flip angle (less gradient steps in the y‐direction) and more sensitive RF coils, specifically the multi‐channel phased receive arrays …”

Section: Discussionmentioning

confidence: 99%

Accelerated ¹²⁹Xe MRI morphometry of terminal airspace enlargement: Feasibility in volunteers and those with alpha‐1 antitrypsin deficiency

Ouriadov

Guo

McCormack

et al. 2019

Purpose Multi‐b diffusion‐weighted hyperpolarized inhaled‐gas MRI provides imaging biomarkers of terminal airspace enlargement including ADC and mean linear intercept (Lm), but clinical translation has been limited because image acquisition requires relatively long or multiple breath‐holds that are not well‐tolerated by patients. Therefore, we aimed to accelerate single breath‐hold 3D multi‐b diffusion‐weighted 129Xe MRI, using k‐space undersampling in imaging direction using a different undersampling pattern for different b‐values combined with the stretched exponential model to generate maps of ventilation, apparent transverse relaxation time constant (T2∗), ADC, and Lm values in a single, short breath‐hold; accelerated and non‐accelerated measurements were directly compared. Methods We evaluated multi‐b (0, 12, 20, 30, and 45.5 s/cm2) diffusion‐weighted 129Xe T2∗/ADC/morphometry estimates using acceleration factor (AF = 1 and 7) and multi‐breath sampling in 3 volunteers (HV), and 6 participants with alpha‐1 antitrypsin deficiency (AATD). Results For the HV subgroup, mean differences of 5%, 2%, and 8% were observed between fully sampled and undersampled k‐space for ADC, Lm, and T2∗ values, respectively. For the AATD subgroup, mean differences were 9%, 6%, and 12% between fully sampled and undersampled k‐space for ADC, Lm and T2∗ values, respectively. Although mean differences of 1% and 4.5% were observed between accelerated and multi‐breath sampled ADC and Lm values, respectively, mean ADC/Lm estimates were not significantly different from corresponding mean ADCM/LmM or mean ADCA/LmA estimates (all P > 0.60 , A = undersampled and M = multi‐breath sampled). Conclusions Accelerated multi‐b diffusion‐weighted 129Xe MRI is feasible at AF = 7 for generating pulmonary ADC and Lm in AATD and normal lung.