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Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Parraga, Grace

Abstract

Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction caused by airway remodelling and parenchymal destruction. Clinically, observation of COPD is performed using spirometry, but this technique only provides a global measure of lung health. To supplement these clinical measurements, thoracic computed tomography (CT) and hyperpolarized gas magnetic resonance imaging (MRI) have been used to measure regional structure and function abnormalities. Although CT and MRI have been used to research COPD, combination of both modalities into an interrelated image has never been performed. Therefore, we developed an image processing pipeline to combine MRI-CT information into a multi-parametric response map. In a COPD cohort, multi-parametric measurements became more abnormal as disease severity increased, were related to pulmonary function and quality of life, and revealed novel disease labels. This technique has potential to visualize and quantify the transition phases of COPD allowing for the possible identification of new treatment targets.

Summary for Lay Audience

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide. Presently, there is no cure for COPD so treatment focuses on alleviating symptoms, reducing exacerbations and hospitalizations, and improving quality of life. COPD is diagnosed and monitored using spirometry, a method for measuring airflow at the mouth. While spirometry is widely available and easy to use, it provides only a global measurement of lung function and cannot provide any regional information about the underlying abnormalities present within patients’ lungs.

To supplement spirometry, medical imaging has been used to provide regional measurements as well as information about the underlying abnormalities present within the lungs. Two imaging techniques used in studying COPD are x-ray computed tomography (CT) and hyperpolarized gas magnetic resonance imaging (MRI). Chest CT is used to measure structural changes within the lungs such as tissue destruction and airway abnormalities; whereas hyperpolarized gas MRI measures lung function by using an inhaled gas to identify unventilated regions of the lung known as ventilation defects. Typically, research in COPD uses either CT or MRI, but never a combination of the two in a single complementary image.

In this study, we developed a technique to combine information from both CT and MRI into a single lung map and used this map to categorize patient with COPD. We observed that combined CT-MRI labels became more abnormal with increasing disease severity, were associated with measurements of pulmonary function, quality of life, and exercise capacity, and visualized possible transitory phases of COPD. This study is the first to use a combined CT-MRI label map approach in the investigation of COPD, and the visualization ability of this combined CT-MRI label map may allow for the identification of new treatment targets and endpoints.

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