Preclinical models using single photon emission computed tomography (SPECT) ventilation/perfusion (V/Q) imaging show early changes to the lung caused by cigarette smoke exposure, according to a study published in the April issue of The Journal of Nuclear Medicine.
Chronic obstructive pulmonary disease (COPD), often associated with cigarette smoking, frequently is undiagnosed before its symptomatic stages. Researchers are investigating ways to detect and diagnose COPD in earlier stages.
Canadian researchers used SPECT V/Q, followed by CT scan to study mice that underwent whole-body exposure to mainstream cigarette smoke for 50 minutes twice daily, five days a week, for either eight or 24 weeks. Scans were performed after the final cigarette smoke exposure and on age-matched control mice. The scans were followed by collection of histologic lung sections. A semiautomated quantitative analysis of airspace enlargement was applied to whole histology slices.
The findings showed that there was functional impairment in the lungs of the smoke-exposed mice, due to increased inflammation and airspace enlargement. Airspace enlargement was also significantly increased at eight weeks of cigarette smoke exposure and was still more pronounced at 24 weeks.
This functional impairment, measured with SPECT V/Q imaging, identified COPD characteristics before CT was able to detect structural changes in the lungs.
“CT was not capable of discriminating control from cigarette-exposed animals at either time point, even with greater resolution and respiratory gating,” the authors wrote. In addition, V/Q mismatching progressively increased during cigarette smoke exposure in mice compared to age-matched control mice and offered insight into the underlying pathology causing COPD.
“Our preclinical study suggests that not only can V/Q imaging detect early and small changes in lung pathology, the type of V/Q mismatching could provide insight into the underlying pathologies, which current measures of lung function are unable to do,” study author N. Renee Labiris, PhD, said in a release.
“V/Q imaging is a common nuclear medicine technique, and SPECT/CT systems are increasingly used in clinical practice,” Labiris noted. “As such, the technology examined in this study can be carried out in both preclinical and clinical settings, enabling researchers to translate preclinical investigations of disease, associated functional abnormalities and future drug targets into an improved understanding and management of the disease in patients.”