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Author Spotlight: Standardization and Best Practices for Advancing Lung Imaging Using 129Xe MRI
Published on: November 21, 2023
Assessment of pulmonary morphometry using hyperpolarized 129 Xe diffusion-weighted MRI with variable-sampling-ratio
Qian Zhou1,2, Haidong Li1,2, Qiuchen Rao1
1Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, Wuhan, China.
Background:
Hyperpolarized (HP) 129 Xe multiple b-values diffusion-weighted magnetic resonance imaging (DW-MRI) has been widely used for quantifying pulmonary microstructural morphometry. However, the technique requires long acquisition times, making it hard to apply in patients with severe pulmonary diseases, who cannot sustain long breath holds.
Purpose:
To develop and evaluate the technique of variable-sampling-ratio compressed sensing (VCS) patterns for accelerating HP 129 Xe multiple b-values DW-MRI in humans.
Methods:
Optimal variable sampling ratios and corresponding k-space undersampling patterns for each b-value were obtained by retrospective simulations based on the fully sampled (FS) DW-MRI dataset acquired from six young healthy volunteers. Then, the FS datasets were retrospectively undersampled using both VCS patterns and conventional compressed sensing (CS) pattern with a similar average acceleration factor. The quality of reconstructed images with retrospective VCS (rVCS) and CS (rCS) datasets were quantified using mean absolute error (MAE) and structural similarity (SSIM). Pulmonary morphometric parameters were also evaluated between rVCS and FS datasets. In addition, prospective VCS multiple b-values 129 Xe DW-MRI datasets were acquired from 14 cigarette smokers and 13 age-matched healthy volunteers. The differences of lung morphological parameters obtained with the proposed method were compared between the groups using independent samples t-test. Pearson correlation coefficient was also utilized for evaluating the correlation of the pulmonary physiological parameters obtained with VCS DW-MRI and pulmonary function tests.
Results:
Lower MAE and higher SSIM values were found in the reconstructed images with rVCS measurement when compared to those using conventional rCS measurement. The details and quality of the images obtained with rVCS and FS measurements were found to be comparable. The mean values of the morphological parameters derived from rVCS and FS datasets showed no significant differences (p > 0.05), and the mean differences of measured acinar duct radius, mean linear intercept, surface-to-volume ratio, and apparent diffusion coefficient with cylinder model were -0.87%, -2.42%, 2.04%, and -0.50%, respectively. By using the VCS technique, significant differences were delineated between the pulmonary morphometric parameters of healthy volunteers and cigarette smokers (p < 0.001), while the acquisition time was reduced by four times.
Conclusion:
A fourfold reduction in acquisition time was achieved using the proposed VCS method while preserving good image quality. Our preliminary results demonstrated that the proposed method can be used for evaluating pulmonary injuries caused by cigarette smoking and may prove to be helpful in diagnosing lung diseases in clinical practice.
Insights
Variable-sampling-ratio compressed sensing (VCS) accelerates hyperpolarized 129 Xe diffusion-weighted MRI, reducing scan times fourfold. This technique preserves image quality, enabling effective evaluation of lung injuries in smokers.
Area of Science:
- Pulmonary imaging
- Magnetic Resonance Imaging (MRI)
- Medical Physics
Background:
- Hyperpolarized (HP) 129 Xe diffusion-weighted MRI (DW-MRI) quantifies lung microstructure but requires long acquisition times.
- This lengthy acquisition is challenging for patients with severe lung diseases unable to sustain breath holds.
Purpose of the Study:
- To accelerate HP 129 Xe DW-MRI using variable-sampling-ratio (VCS) compressed sensing patterns.
- To evaluate the efficacy of VCS for human pulmonary imaging.
Main Methods:
- Retrospective simulations determined optimal VCS patterns for multiple b-values.
- Image quality was assessed using MAE and SSIM, comparing VCS with conventional CS.
- Pulmonary morphometric parameters were evaluated between VCS and fully sampled datasets.
- Prospective VCS DW-MRI was performed on smokers and healthy volunteers.
Main Results:
- VCS achieved a fourfold reduction in acquisition time with comparable image quality to fully sampled data.
- Reconstructed images using VCS showed lower MAE and higher SSIM than conventional CS.
- No significant differences in morphometric parameters were found between VCS and fully sampled datasets.
- Significant differences in lung parameters were identified between smokers and healthy controls using VCS.
Conclusions:
- VCS significantly accelerates HP 129 Xe DW-MRI while maintaining diagnostic image quality.
- The method shows promise for evaluating smoking-induced lung injuries and clinical diagnosis of lung diseases.
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