Kiarash Emami MS, Presenter: Nothing to Disclose

Martin Fischer PhD, Abstract Co-Author: Nothing to Disclose

Jianliang Zhu, Abstract Co-Author: Nothing to Disclose

Warren Bruce Gefter MD, Abstract Co-Author: Consultant, Siemens AG

Joseph Shrager MD, Abstract Co-Author: Nothing to Disclose

Rahim Rajaei Rizi PhD, Abstract Co-Author: Nothing to Disclose

To assess the sensitivity of regional fractional ventilation (r) measured by hyperpolarized (HP) 3He MRI as a pulmonary functional marker versus the gold standard structural marker, mean linear intercept (Lm) to formation and progress of emphysema.

Emphysema model was induced with elastase in two groups of Sprague-Dawley rats corresponding to mild (5U/100g) and moderate (10U/100g). Both groups underwent PFT and were imaged at 5 and 10 weeks along with a group of controls. r was measured using HP 3He MRI by measuring the signal build-up after successive number of breaths. Regional maps of r were generated for each subject. After imaging session, histology was performed in the central portions of each lobe (left, upper and lower right) and Lm was calculated as a measure of alveolar size, corresponding to the degree of emphysema. Regional correlation of r and Lm was studied.

Lm shows an increase with both a higher elastase dose and the evolution of time, as expected. Regional fractional ventilation in both mild and moderate emphysema drops monotonically with time. Even though r approaches a similar value for both doses of elastase over the 10-week period, it shows a broader difference during early stages of disease, i.e. around 5 weeks. Lm difference is almost undistinguishable for these two levels of severity at the 5-week time point. Lm on the other hand shows a greater variation at 10-week points. Planar correlation of r and Lm depicts two statistically separable regimes: early stage (5-wks) dominated by changes in r and later stage (10-wks) dominated by Lm.

Results suggest that measurements of fractional ventilation by HP 3He MRI can potentially reveal changes in lung function which might not be observable in lung structure, as measured by Lm in this study, during the early stages of formation or progression of emphysema. Longitudinal studies on same subjects by measuring both function and structure of lung would be necessary to confirm the findings in cohorts.

Non-invasive repeatable lung screening by HP 3He MRI has a great potential in identifying onset of pulmonary disorders by quantitative measurement of lung function and structure.

Emami, K, Fischer, M, Zhu, J, Gefter, W, Shrager, J, Rizi, R, Early Detection of Emphysema by Hyperpolarized Helium-3 MRI through Measuring Regional Fractional Ventilation.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4442219.html