Featured Article: Image Analysis In The Pharmaceutical Industry

By MARK BUMILLER

Microscopy has been a standard tool for particle characterization for many years. The USP <776> standard for optical microscopy was first introduced in the second supplement of the USP 23-NF 18 in 1995. Starting around 1985, pharmaceutical laboratories began automating microscopic analysis by integrating microscopes to frame grabber cards and custom-written software. Microscope manufacturers began offering packages for particle size analysis during this same time period. These early systems were sometimes developed for counting particles trapped on filters to inspect contamination within parenteral drugs. Also at this time, the USP <788> test for Particulate Matter in Injections was expanded to include a procedure for microscopic analysis.

By 1995, instrument vendors began marketing image analysis systems for particle characterization, both for suspensions and powders. Pharmaceutical laboratories now can purchase complete turnkey systems that can be validated and operational at the same time as other particle-sizing techniques. The rapid developments in computers, digital cameras, and software have facilitated the adoption of image analysis in modern particle

Image analysis systems fit into two general categories: static and dynamic. Static image analysis measures samples that typically rest on a slide moved by an automated stage. A microscope and digital camera collect an image of the particles on the slide each time the stage stops during a scan. Dynamic image analyzers measure samples that flow through a cell or in front of the optics, which collect an image of particles with a strobe or through timed image captures.