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Rajagopal S, Bogaard HJ, Elbaz MSM, Freed BH, Remy-Jardin M, van Beek EJR, Gopalan D, Kiely DG. Emerging multimodality imaging techniques for the pulmonary circulation. Eur Respir J 2024:2401128. [PMID: 39209480 DOI: 10.1183/13993003.01128-2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Accepted: 06/11/2024] [Indexed: 09/04/2024]
Abstract
Pulmonary hypertension (PH) remains a challenging condition to diagnose, classify and treat. Current approaches to the assessment of PH include echocardiography, ventilation/perfusion scintigraphy, cross-sectional imaging using computed tomography and magnetic resonance imaging, and right heart catheterisation. However, these approaches only provide an indirect readout of the primary pathology of the disease: abnormal vascular remodelling in the pulmonary circulation. With the advent of newer imaging techniques, there is a shift toward increased utilisation of noninvasive high-resolution modalities that offer a more comprehensive cardiopulmonary assessment and improved visualisation of the different components of the pulmonary circulation. In this review, we explore advances in imaging of the pulmonary vasculature and their potential clinical translation. These include advances in diagnosis and assessing treatment response, as well as strategies that allow reduced radiation exposure and implementation of artificial intelligence technology. These emerging modalities hold the promise of developing a deeper understanding of pulmonary vascular disease and the impact of comorbidities. They also have the potential to improve patient outcomes by reducing time to diagnosis, refining classification, monitoring treatment response and improving our understanding of disease mechanisms.
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Affiliation(s)
| | - Harm J Bogaard
- Department of Pulmonology, Amsterdam University Medical Center, Location VU Medical Center, Amsterdam, The Netherlands
| | - Mohammed S M Elbaz
- Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Benjamin H Freed
- Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | | | - Edwin J R van Beek
- Edinburgh Imaging, Queens Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Deepa Gopalan
- Department of Radiology, Imperial College Healthcare NHS Trust, London, UK
| | - David G Kiely
- Sheffield Pulmonary Vascular Disease Unit and NIHR Biomedical Research Centre Sheffield, Royal Hallamshire Hospital, Sheffield, UK
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Mummy D, Zhang S, Bechtel A, Lu J, Mammarappallil J, Leewiwatwong S, Costelle A, Swaminathan A, Driehuys B. Functional gas exchange measures on 129Xe MRI and spectroscopy are associated with age, sex, and BMI in healthy subjects. Front Med (Lausanne) 2024; 11:1342499. [PMID: 38651062 PMCID: PMC11033479 DOI: 10.3389/fmed.2024.1342499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 03/27/2024] [Indexed: 04/25/2024] Open
Abstract
Introduction Hyperpolarized 129Xe MRI and spectroscopy is a rapidly growing technique for assessing lung function, with applications in a wide range of obstructive, restrictive, and pulmonary vascular disease. However, normal variations in 129Xe measures of gas exchange across healthy subjects are not well characterized, presenting an obstacle to differentiating disease processes from the consequences of expected physiological heterogeneity. Here, we use multivariate models to evaluate the role of age, sex, and BMI in a range of commonly used 129Xe measures of gas exchange. Materials and methods Healthy subjects (N = 40, 16F, age 44.3 ± 17.8 yrs., min-max 22-87 years) with no history of cardiopulmonary disease underwent 129Xe gas exchange MRI and spectroscopy. We used multivariate linear models to assess the associations of age, sex, and body mass index (BMI) with the RBC:Membrane (RBC:M), membrane to gas (Mem:Gas), and red blood cell to gas (RBC:Gas) ratios, as well as measurements of RBC oscillation amplitude and RBC chemical shift. Results Age, sex, and BMI were all significant covariates in the RBC:M model. Each additional 10 years of age was associated with a 0.05 decrease in RBC:M (p < 0.001), each additional 10 points of BMI was associated with a decrease of 0.07 (p = 0.02), and males were associated with a 0.17 higher RBC:M than females (p < 0.001). For Mem:Gas, male sex was associated with a decrease and BMI was associated with an increase. For RBC:Gas, age was associated with a decrease and male sex was associated with an increase. RBC oscillation amplitude increased with age and RBC chemical shift was not associated with any of the three covariates. Discussion 129Xe MRI and spectroscopy measurements in healthy subjects, particularly the widely used RBC:M measurement, exhibit heterogeneity associated in part with variations in subject age, sex, and BMI. Elucidating the contributions of these and other factors to 129Xe gas exchange measurements is a critical component for differentiating disease processes from expected variation in healthy subjects. Notably, the Mem:Gas and RBC chemical shift appear to be stable with aging, suggesting that unexplained deviations in these metrics may be signs of underlying abnormalities.
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Affiliation(s)
- David Mummy
- Department of Radiology, Duke University, Durham, NC, United States
| | - Shuo Zhang
- Department of Radiology, Duke University, Durham, NC, United States
| | - Aryil Bechtel
- Department of Radiology, Duke University, Durham, NC, United States
| | - Junlan Lu
- Medical Physics Graduate Program, Duke University, Durham, NC, United States
| | | | | | - Anna Costelle
- Medical Physics Graduate Program, Duke University, Durham, NC, United States
| | | | - Bastiaan Driehuys
- Department of Radiology, Duke University, Durham, NC, United States
- Medical Physics Graduate Program, Duke University, Durham, NC, United States
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
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Lu J, Alenezi F, Bier E, Leewiwatwong S, Mummy D, Kabir S, Rajagopal S, Robertson S, Niedbalski PJ, Driehuys B. Optimized quantitative mapping of cardiopulmonary oscillations using hyperpolarized 129 Xe gas exchange MRI: Digital phantoms and clinical evaluation in CTEPH. Magn Reson Med 2024; 91:1541-1555. [PMID: 38084439 PMCID: PMC10872359 DOI: 10.1002/mrm.29965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 02/03/2024]
Abstract
PURPOSE The interaction between 129 Xe atoms and pulmonary capillary red blood cells provides cardiogenic signal oscillations that display sensitivity to precapillary and postcapillary pulmonary hypertension. Recently, such oscillations have been spatially mapped, but little is known about optimal reconstruction or sensitivity to artifacts. In this study, we use digital phantom simulations to specifically optimize keyhole reconstruction for oscillation imaging. We then use this optimized method to re-establish healthy reference values and quantitatively evaluate microvascular flow changes in patients with chronic thromboembolic pulmonary hypertension (CTEPH) before and after pulmonary thromboendarterectomy (PTE). METHODS A six-zone digital lung phantom was designed to investigate the effects of radial views, key radius, and SNR. One-point Dixon 129 Xe gas exchange MRI images were acquired in a healthy cohort (n = 17) to generate a reference distribution and thresholds for mapping red blood cell oscillations. These thresholds were applied to 10 CTEPH participants, with 6 rescanned following PTE. RESULTS For undersampled acquisitions, a key radius of0.14 k max $$ 0.14{k}_{\mathrm{max}} $$ was found to optimally resolve oscillation defects while minimizing excessive heterogeneity. CTEPH participants at baseline showed higher oscillation defect + low (32 ± 14%) compared with healthy volunteers (18 ± 12%, p < 0.001). For those scanned both before and after PTE, oscillation defect + low decreased from 37 ± 13% to 23 ± 14% (p = 0.03). CONCLUSIONS Digital phantom simulations have informed an optimized keyhole reconstruction technique for gas exchange images acquired with standard 1-point Dixon parameters. Our proposed methodology enables more robust quantitative mapping of cardiogenic oscillations, potentially facilitating effective regional quantification of microvascular flow impairment in patients with pulmonary vascular diseases such as CTEPH.
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Affiliation(s)
- Junlan Lu
- Medical Physics Graduate Program, Duke University, Durham, North Carolina, USA
| | - Fawaz Alenezi
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Elianna Bier
- Biomedical Engineering, Duke University, Durham, North Carolina, USA
| | | | - David Mummy
- Radiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Sakib Kabir
- Radiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Sudarshan Rajagopal
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Scott Robertson
- Clinical Imaging Physics Group, Duke University Medical Center, Durham, North Carolina, USA
| | - Peter J. Niedbalski
- Division of Pulmonary, Critical Care, and Sleep Medicine, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Bastiaan Driehuys
- Medical Physics Graduate Program, Duke University, Durham, North Carolina, USA
- Biomedical Engineering, Duke University, Durham, North Carolina, USA
- Radiology, Duke University Medical Center, Durham, North Carolina, USA
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Khan SL, Mathai SC. Scleroderma pulmonary arterial hypertension: the same as idiopathic pulmonary arterial hypertension? Curr Opin Pulm Med 2023; 29:380-390. [PMID: 37461869 PMCID: PMC11334969 DOI: 10.1097/mcp.0000000000001001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
PURPOSE OF REVIEW Pulmonary arterial hypertension (PAH) is a common complication of systemic sclerosis (SSc), which confers significant morbidity and mortality. The current therapies and treatment strategies for SSc-associated PAH (SSc-PAH) are informed by those used to treat patients with idiopathic PAH (IPAH). There are, however, important differences between these two diseases that impact diagnosis, treatment, and outcomes. RECENT FINDINGS Both SSc-PAH and IPAH are incompletely understood with ongoing research into the underlying cellular biology that characterize and differentiate the two diseases. Additional research seeks to improve identification among SSc patients in order to diagnose patients earlier in the course of their disease. Novel therapies specifically for SSc-PAH such as rituximab and dimethyl fumarate are under investigation. SUMMARY Although patients with SSc-PAH and IPAH present with similar symptoms, there are significant differences between these two forms of PAH that warrant further investigation and characterization of optimal detection strategies, treatment algorithms, and outcomes assessment.
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Affiliation(s)
- Sarah L Khan
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Foo CT, Langton D, Thompson BR, Thien F. Functional lung imaging using novel and emerging MRI techniques. Front Med (Lausanne) 2023; 10:1060940. [PMID: 37181360 PMCID: PMC10166823 DOI: 10.3389/fmed.2023.1060940] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 04/03/2023] [Indexed: 05/16/2023] Open
Abstract
Respiratory diseases are leading causes of death and disability in the world. While early diagnosis is key, this has proven difficult due to the lack of sensitive and non-invasive tools. Computed tomography is regarded as the gold standard for structural lung imaging but lacks functional information and involves significant radiation exposure. Lung magnetic resonance imaging (MRI) has historically been challenging due to its short T2 and low proton density. Hyperpolarised gas MRI is an emerging technique that is able to overcome these difficulties, permitting the functional and microstructural evaluation of the lung. Other novel imaging techniques such as fluorinated gas MRI, oxygen-enhanced MRI, Fourier decomposition MRI and phase-resolved functional lung imaging can also be used to interrogate lung function though they are currently at varying stages of development. This article provides a clinically focused review of these contrast and non-contrast MR imaging techniques and their current applications in lung disease.
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Affiliation(s)
- Chuan T. Foo
- Department of Respiratory Medicine, Eastern Health, Melbourne, VIC, Australia
- Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC, Australia
| | - David Langton
- Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC, Australia
- Department of Thoracic Medicine, Peninsula Health, Frankston, VIC, Australia
| | - Bruce R. Thompson
- Melbourne School of Health Science, Melbourne University, Melbourne, VIC, Australia
| | - Francis Thien
- Department of Respiratory Medicine, Eastern Health, Melbourne, VIC, Australia
- Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC, Australia
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