Quantitative lung SPECT applied on simulated early COPD and humans with advanced COPD

Area of Science:

• Nuclear Medicine
• Pulmonary Imaging
• Quantitative Analysis

Background:

• Chronic Obstructive Pulmonary Disease (COPD) is characterized by reduced lung ventilation, leading to inhomogeneities detectable in SPECT imaging.
• Disease advancement in COPD correlates with the severity of these ventilation defects.
• Accurate quantification of these inhomogeneities is crucial for disease monitoring.

Purpose of the Study:

• To develop a quantitative analysis method for measuring ventilation inhomogeneities in SPECT lung images.
• To validate the method's ability to differentiate between simulated normal and COPD lung SPECT images.
• To assess the method's efficacy in distinguishing advanced COPD patients from healthy individuals.

Main Methods:

• Monte Carlo simulations were used to create normal and COPD lung SPECT images with varying activity distributions.
• The coefficient of variance (CV) was calculated in small overlapping volumes of the 3D reconstructed activity distribution.
• A threshold value (CVT) was determined from normal lung CV distributions, and the area under the curve (AUC) above CVT (AUC(CVT)) was calculated.
• The method was applied to SPECT data from five healthy volunteers and five patients with advanced emphysema.

Main Results:

• The analysis method showed a significant difference (p < 0.001) between simulated normal and COPD lung SPECT images.
• The method detected approximately 5% ventilation reduction in simulated COPD, which was not visually apparent.
• In human subjects, the method clearly discriminated between healthy volunteers and patients with advanced COPD (p < 0.05).

Conclusions:

• The developed AUC(CVT) method demonstrates significant potential for quantitative analysis of ventilation inhomogeneities in SPECT lung imaging.
• The method successfully discriminated between healthy individuals and those with advanced COPD.
• Further clinical studies are warranted to evaluate the method's capability in detecting less advanced stages of COPD.