Determination of smoothness of canisters containing inhalable medicaments

A method for determining a smoothness index of a metered dose container having an inner core comprising the steps of

• a) subjecting said inner core of said metered dose container containing at least one pharmacologically active agent to reflected light photomicrography to obtain a digital image containing a plurality of pixels of said inner core;
• b) determining from said digital image the brightness of each of said pixels and quantifying said brightness by assigning an integer value thereto, wherein said value corresponds to an amount of brightness;
• and
• c) comparing said brightness of said pixel to a reference standard to determine the smoothness index of said inner core of said metered dose container.