Digital imaging analyzes aerosol inhalers
Developing effective dry powder formulations and aerosol inhalers involves analysis of how dry powder particles are emitted when the inhaler is activated. In the past, performing this analysis has required the use of high-speed, single-lens reflex cameras and professional-grade film in a time-consuming and costly process.
To eliminate these limitations, Won Chi and his colleagues at Primedica (Cambridge, MA) have developed a digital method of recording and analyzing images from aerosol inhalers using off-the-shelf image-processing hardware and software. As part of a product-development cycle for a dry-powder inhaler (DPI) from Allen and Hanbury (Research Triangle Park, NC), Chi built a specially designed plume-geometry chamber.
To analyze the dry-power and inhaler effects, DPIs are fired into the chamber and the resulting digital plume is captured with a Depict-IT 1296 ¥ 1024-pixel, progressive-scan, CCD camera from Opteon (Cambridge, MA). After digitization with Opteon`s PCI-based DepictMaster frame grabber, the images are transferred to host memory on an Intel Pentium II-based PC. "In operation," says Chi, "a minimum of three emissions from both the prototype DPI and Allen and Hanbury`s established Rotohaler inhaler were captured by the frame grabber and stored on the PC`s hard drive."
To determine the density profile and the plume velocity of each image, Chi and his colleagues customized the XCaliper OCX software tools from FLIR Systems (Portland, OR) with the Visual C++ 5.0 Professional Integrated Development environment from Microsoft (Redmond, WA). The data demonstrate that the analysis software tools were comparable to those derived with manual analysis techniques.
