Abstract
Objective: To compare three advanced imaging modalities: dual-energy computed tomography (DECT), single-photon emission computed tomography/computed tomography (SPECT/CT) and hyperpolarized gas MRI in chronic lung diseases.
Methodology: This prospective observational study was carried out at Liaquat University of Medical and Health Sciences (LUMHS) and the National Institute of Cardiovascular Diseases (NICVD), Karachi from June to September 2023. A sample of 90 individuals with chronic lung disease was selected and placed in three groups (n=30 each): Group A (DECT), Group B (SPECT/CT), and Group C (hyperpolarized gas MRI) through random assignment. Every patient received a pulmonary function test and then had an imaging. The volume of V/Q defects, mismatch score, and the sensitivity to lesions were considered as primary outcome measures. Analysis of Variance (ANOVA), Chi-square, and Pearson correlation were employed.
Results: Hyperpolarized gas MRI had the lowest V/Q defect volume (109.4±25.1 mL), the highest mismatch score (8.2±1.2), and the highest lesion detection sensitivity (91.4%), which were all significantly better than DECT and SPECT/CT (p<0.05 of all comparisons). MRI results had strong correlation with the main physiological indicators, including forced expiratory volume in one second (FEV₁), diffusing capacity of the lungs for carbon monoxide (DLCO), and arterial oxygen partial pressure (pO₂) (r=0.69-0.81, p<0.001).
Conclusion: Hyperpolarized gas MRI is more precise and clinically salient than DECT and SPECT/CT in identifying and estimating V/Q mismatch in chronic lung disease. It provides high-quality functional imaging and must be included in the diagnostic work-up of such patients.

Key words: Chronic lung disease, ventilation-perfusion mismatch, dual-energy CT, SPECT/CT, pulmonary imaging.