Andreas Voskrebenzev, Agilo Kern, Lea Behrendt, Filip Klimes, Marcel Gutberlet, Gesa Pöhler, Frank Wacker, Jens Vogel-Claussen

Pulmonary function parameters like the ratio of expiratory volume in one second (FEV1) and forced vital capacity (FVC) are the current gold standard for disease diagnosis and monitoring. However, early disease detection remains limited due to missing regional information. In this study the forced expiratory maneuver was captured with a dynamic MRI acquisition, as used in Fourier decomposition or phase-resolved functional lung imaging (PREFUL), for FEV1/FVC mapping. Results were compared with spirometry, PREFUL and hyperpolarized MRI in four healthy subjects and one patient with cystic fibrosis and suggest a potentially increased sensitivity in comparison with the tidal breathing approach.

Tanguy Boucneau, Brice Fernandez, Peder Larson, Luc Darrasse, Xavier Maître

Spirometry is a routine tool in pulmonology to challenge lung function. It is sensitive and specific to several common lung diseases. Nevertheless, spirometry provides a global measurement at the mouth that only characterizes the pulmonary response as a whole, and cannot specifically address regional affections. We developed a 3D MRI-based technique to non-invasively perform local spirometry throughout the lung. The final outcome is a 3D map with voxel-wise flow-volume loops over the organ. The potential of this technique is demonstrated by its sensitivity to normal, thoracic, and diaphragmatic breathings and its related regional specificity in a healthy subject.

Ipshita Bhattacharya, Rajiv Ramasawmy, Delaney McGuirt, Christine Mancini, Robert Lederman, Joel Moss, Marcus Chen, Robert Balaban, Adrienne Campbell-Washburn

Signal dephasing at high field and low proton density, has limited the use of MRI for lung imaging. We revisit the problem, using a low field (0.55T) scanner which, due to low magnetic susceptibility, improves the signal at air-tissue boundaries like lung. Moreover, because oxygen has increased r1 relaxativity at low field, oxygen inhalation can be used to significantly increase lung signal at 0.55T. Combined, these advantages makes lung MRI lucrative at low field. In this abstract we demonstrate oxygen-enhanced lung MRI at 0.55T in healthy volunteers and Lymphangioleiomyomatosis (LAM)  patients.  

Elianna Bier, Ziyi Wang, Aparna Swaminathan, John Nouls, Mu He, Joseph Mammarappallil, Sheng Lou, Sudarshan Rajagopal, Bastiaan Driehuys

This work sought to identify a non-invasive means to detect pulmonary arterial hypertension (PAH). ¹²⁹Xenon MRI and dynamic spectroscopy were acquired in healthy volunteers and subjects with chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), left heart failure (LHF), and PAH. COPD was differentiated from PAH by increased ventilation and barrier defects, while IPF was differentiated by increased barrier uptake. PAH and LHF subjects had similar imaging features but could be differentiated by their RBC signal oscillation amplitudes. ¹²⁹Xe MR imaging and spectroscopy appears capable of differentiating PAH from COPD, IPF, and LHF. 

James Eaden, Paul Hughes, Ho-Fung Chan, Oliver Rodgers, Guilhem Collier, Graham Norquay, Matthew Austin, Laurie Smith, Jim Lithgow, Nicholas Weatherley, Helen Marshall, Andrew Swift, Stephen Renshaw, Colm Leonard, Sarah Skeoch, Nazia Chaudhuri, Geoff Parker, Stephen Bianchi, Jim Wild

Preliminary findings are presented from a prospective, longitudinal, multicentre MRI biomarker study of patients presenting with interstitial lung disease (ILD) including drug induced ILD, hypersensitivity pneumonitis, idiopathic pulmonary fibrosis and connective tissue disease ILD. At the time of writing, 27 patients have undergone baseline hyperpolarised xenon-129 (¹²⁹Xe) MR spectroscopy (MRS) and ¹²⁹Xe diffusion-weighted MRI. Our findings suggest significant differences in mean ¹²⁹Xe apparent diffusion coefficient between the ILD subtypes at baseline but no significant differences in the red blood cell / tissue plasma ratio from dissolved ¹²⁹Xe MRS. We also demonstrate correlation between pulmonary function tests and ¹²⁹Xe MRI measures.

Marcus Couch, Jonathan Rayment, Robert Grimm, Andreas Voskrebenzev, Jens Vogel-Claussen, Felix Ratjen, Giles Santyr

Hyperpolarized ¹²⁹Xe MRI provides robust measurements of ventilatory function through the measurement of the ventilation defect percent (VDP). Recent progress in ¹H-based free-breathing techniques (phase-resolved functional lung; PREFUL) allows for the calculation of fractional ventilation maps, which can be similarly processed to calculate VDP. While hyperpolarized ¹²⁹Xe is an established research technique, PREFUL MRI is simple to implement on any MRI scanner and therefore has good potential for use in future clinical trials in cystic fibrosis (CF). In this study, VDP measurements performed using hyperpolarized ¹²⁹Xe and PREFUL MRI were compared and correlated with pulmonary function tests in pediatric CF.

Rachel Eddy, Andrew Westcott, Geoffrey Maksym, David McCormack, Grace Parraga

¹²⁹Xe MRI ventilation defects were previously shown to be greater and more numerous than ³He MRI ventilation defects in patients with chronic obstructive pulmonary disease (COPD) and asthma, however the underlying biomechanical explanation for these differences has not been determined. Here we evaluated the relationships of ³He and ¹²⁹Xe MRI ventilation defect percent (VDP) with oscillometry measurements acquired in patients to better understand the lung biomechanical constraints that lead to such differences. ¹²⁹Xe VDP was significantly related to total respiratory-system resistance whereas ³He was not which may suggest increased sensitivity of ¹²⁹Xe to resistance throughout the entire airway tree.

Matthew Willmering, Peter Niedbalski, Hui Wang, Laura Walkup, Ryan Robison, James Pipe, Zackary Cleveland, Jason Woods

Functional lung imaging via inhaled hyperpolarized ¹²⁹Xe MRI has been shown to provide sensitive regional maps of ventilation and gas-exchange. Traditionally, ventilation images are acquired via standard Cartesian or less commonly radial sequences. Previously reported results have shown promise for 2D-spiral sequences with increased SNR and/or shorter acquisition lengths. In this study, a 3D-spiral sequence (FLORET) was implemented and compared to Cartesian, radial, and 2D-spiral acquisition techniques. This is the first implementation and comparison of a 3D-spiral UTE technique to acquire hyperpolarized gas images.

Mu He, Ziyi Wang, Leith Rankine, Elianna Bier, John Nouls, Bastiaan Driehuys

Both multi-slice GRE and 3D-radial acquisitions can image regional ventilation in the lungs. Here, we sought to evaluate the accuracy of the ventilation images acquired as part of a 3D-radial gas-exchange acquisition by comparing them with those acquired with a standard GRE acquisition. Linear-binning quantification was applied on both acquisitions to derive the quantitative metrics, through which we found good qualitative and modest pixel-wise agreement between the two ventilation scans. With further reconciliation of bias-field correction and threshold-setting for the 3D-radial pipeline, it could become a one-stop shop for single-breath ventilation and gas exchange imaging.

Gang Xiao, Wei-Cheng Rong, Zhong-Qiang Shi, Xiao-Cheng Wei, Wen Wang, Yu-Chuan Hu, Guang-Bin Cui

To explore the performance of MR radiomics in predicting the pathological classification and staging of thymic epithelial tumors (TETs), we built two radiomics models based on support vector machine. Besides, we developed a radiomics nomogram for predicting risk stratification of advanced TETs. The models achieved an area under the curve of 77.1% or 90.8% in the test cohort in distinguishing low-, high-risk thymomas and thymic carcinomas or early and advanced TETs. The radiomics model, symptom, and pericardial effusion constituted a radiomics nomogram, with a C-index of 0.957 in the test cohort. Thus, MR radiomics can be useful for assessing TETs.

Marta Tibiletti, Josephine Naish, Paul Hughes, Helen Marshall, Colm Leonard, Sarah Skeoch, Nazia Chaudhuri, Ian Bruce, James Eaden, Stephen Bianchi, Jim Wild, Geoff Parker

We developed automatic methods to extract the AIF for lung first pass perfusion DCE and compared their performance with manual selection of an ROI in the pulmonary artery (PA). Dynamic enhancement was calculated by simple subtraction and with a shuffle subtraction. Early enhancing voxels with the highest enhancing values were selected. We demonstrated that the shuffle subtraction is a more robust method, since it avoids including the early enhancing subclavian vein. Our results suggest obtaining the AIF automatically from pixels within the RV may be more robust against partial volume effects and removes inter-reader variability.

William Meadus, Richard Thompson, Robert Stobbe, Christian Beaulieu

The goal of this study was to develop and validate a fast, robust and quantitative MRI method for the evaluation of lung water density, for the detection of pulmonary edema. Short lung T2* necessitates ultrashort TE (UTE) acquisitions. We propose a novel optimized UTE Yarn-Ball k-space trajectory that uses ~15% of the pure radial readouts arms required to achieve full sampling. Phantom studies validated accurate water density quantification. A dual-echo approach enabled automated lung tissue segmentation. An optimized Yarn-Ball k-space trajectory yields three-dimensional spin-density weighted lung water images (2.5mm isotropic resolution), without the need for breath-holding, in ~2 minutes.

Mary Neal, Ben Pippard, A John Simpson, Pete Thelwall

¹⁹F-MRI of inhaled perfluoropropane (PFP) can be used to assess pulmonary ventilation. PFP has a short in vivo T₂^* (~2ms) arising from magnetic field inhomogeneity in the lung, reflecting the different magnetic susceptibilities of adjacent alveolar walls and gas components. Intravenous injection of a paramagnetic contrast agent to the pulmonary circulation can transiently reduce these magnetic susceptibility gradients, raising the T₂^* of inhaled PFP in regions directly adjacent to well-perfused lung. We present the first in man demonstration of combined pulmonary ventilation and perfusion assessment using ¹⁹F-MRI of inhaled PFP with concurrent administration of a gadolinium-based contrast agent.

Helen Marshall, Andreas Voskrebenzev, Alberto Biancardi, Bilal Tahir, Laurie Smith, Jim Wild, Jens Vogel-Claussen

Free-breathing non-contrast enhanced ¹H MRI techniques show promise as a surrogate for ventilation imaging but more validation against methods which directly image lung ventilation is needed in patients.  The aim of this work was to investigate the relationship between ¹H free-breathing and ³He breath-hold ventilation images in patients with CF. Phase-resolved functional lung (PREFUL) ¹H and ³He ventilation images were compared in 10 patients with CF.  Qualitative similarities were observed between techniques to varying degrees.  Ventilation defect percentage showed strong correlation between methods and with FEV₁, although median and inter-quartile range fractional ventilation values were not related.

Wei Zha, Kevin Johnson, Robert Cadman, Scott Nagle, Sean Fain

Three-dimensional dynamic imaging using free-breathing oxygen-enhanced (OE) ultrashort echo time (UTE) MRI can measure change of partial pressure of oxygen (ΔPO₂) and wash-in/out time constants. Nine healthy subjects underwent the dynamic OE MRI protocol at 1.5T. A subset of 4 subjects underwent repeated exams and 2 of these 4 underwent the same protocol at 3.0T on the same day. The inter-exam variations at 1.5T suggest good quantitative measurements of lung function and wash-in/out dynamics with variations observed in ΔPO_2max. The parametric maps imply comparable wash-in/out time constants and normal ventilation measured at 1.5T vs. 3.0T.