Table of contents 1 Why is particle size important?
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| STATIC IMAGE ANALYSIS
The samples measured by static image analysis typically rest on a slide that is moved by an automated stage. With the PSA300 static image analysis system a microscope and digital camera collect images of the particles as the slide is scanned. Samples prepared on slides can include powders, suspensions, or creams. Aerosol delivery forms such as metered dose inhalers or dry powder inhalers can be inspected using static image analysis by actuating the device onto a slide for measurement. In addition, particles in suspension (such as parenterals) can be collected on a filter for characterization. The majority of static image analysis measurements are made on powders, typically used for solid oral dosage forms. Most powders require a sample preparation step prior to analysis. Powder preparation devices—using either positive pressure to impact on a hard surface or pulling and releasing a vacuum—break apart agglomerates and create an even dispersion on the slide. After the sample has been prepared and the automated stage has presented multiple fields to the optics and camera for capture, a series of image processing steps occur in the software. The first step is to separate the particles from the background by setting a parameter with some threshold value. Setting this threshold can be done manually or automatically based on phases in the grayscale image or through a contrast threshold function based on the particle/background contrast. After the threshold operation is completed several functions may be applied to the image to improve the edge definition. The basic functions of erosion and dilation improve edge definition by performing opposite tasks of removing or adding dark pixels at the particle edge. Advanced functions using combinations of erosion and dilation steps such as delineation and convex hull improve the edge definition of particles, leading to accurate area and perimeter determinations that are critical for shape factor calculations. Other software functions perform the task of separating touching particles including the crossed fibers in order to quantify fiber length distributions and aspect ratios. figure 30 | BASIC IMAGE ANALYSIS FUNCTIONS Both static and dynamic image analysis involve these basic steps. tải về 7.54 Mb. Chia sẻ với bạn bè của bạn:
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