Definition of airway composition within gamma camera images

The efficacies of inhaled pharmacologic drugs in the prophylaxis and treatment of airway diseases could be improved if particles were selectively directed to appropriate sites. In the medical arena, planar gamma scintillation cameras may be employed to study factors affecting such particle deposition patterns within the lung. The value and versatility of such instruments, however, are compromised by the limited resolution of their images. Specifically, it is not possible to determine the composition of their central (C) or large airway, intermediate (I), and peripheral (P) or small airway zones. We present an analytical model to assist the clinician in the systematic analysis and interpretation of gamma camera images. Using the Cray Y-MP supercomputer, a range of human lung morphologies has been mapped to function as templates that can be superimposed on scans. The model is intended to complement laboratory regimens by providing a previously unavailable method to define the C, I, and P zones of the human lung generation by generation. A quantitative value now can be assigned to the degree of overlapping that exists in the images. For example, for a "typical" lung morphology consisting of 16,777,215 airways (total), the C zone itself may contain 1,608,246 airways, of which 1,595,940, or 99.2%, are alveolated airways. By identifying composition, our intent is to integrate the model into future aerosol therapy protocols and thereby assist procedures that target delivery of airborne pharmaceuticals.