Does quantitative lung SPECT detect lung abnormalities earlier than lung function tests? Results of a pilot study

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Respiratory Physiology

Background:

• Lung ventilation heterogeneity is a known issue in conditions like COPD and asthma.
• Current imaging methods like PET, MRI, and SPECT can visualize this heterogeneity.
• Quantitative analysis using SPECT-derived coefficient of variation (CV) can map and measure lung heterogeneity.

Purpose of the Study:

• To explore the use of SPECT imaging to detect mild ventilation heterogeneities in lung-healthy subjects.
• To quantitatively measure ventilation heterogeneity using the area under the compensated CV density curve (AUC(CV > CVT)).

Main Methods:

• Fourteen healthy subjects and two patients with airway disease underwent SPECT imaging after inhaling 99mTc-Technegas.
• Ventilation heterogeneity was quantified using AUC(CV > 20%) after compensating for activity uptake variations.
• Correlations between AUC(CV > 20%) and lung function parameters, age, and height were analyzed.

Main Results:

• Patients with lung function abnormalities showed significantly higher AUC(CV > 20%) values than healthy subjects.
• AUC(CV > 20%) values correlated positively with age and height, indicating increased heterogeneity with age and depending on lung size.
• Strong correlations were observed between AUC(CV > 20%) and lung function indices like RV/TLC and DLCOc.

Conclusions:

• A subset of healthy subjects exhibited elevated AUC(CV > 20%) values despite normal lung function tests.
• This suggests that SPECT-based ventilation heterogeneity measurement can potentially detect early-stage lung disease before conventional tests.