title: Location-dependent analysis of porosity and pore direction in tablets.
abstract: OBJECTIVE
  Several phenomena in tablets indicate that an inhomogeneous pore distribution is formed during the compaction process. Examples are lamination and the capping of corners. In order to gain an understanding of the relation between structure and compact properties, analyzing the structure in a location dependent manner would be extremely useful. Our aim was to visualize and to quantitatively analyze the pore distribution in compacts.
  
  
  METHODS
  This was done by embedding a cubic (sodium chloride) compact with polymer, allowing the compact to be cut without disrupting the structure. By doing so, it was possible to make scanning electron microscopic images from different angles at different locations in the compact. These images were made binary with a two-means cluster algorithm (Isodata) after which the porosity could be calculated. Counting the number of transitions from the pixels in the pores to the pixels in the sodium chloride particles in two perpendicular directions allows us to construct a measure for the anisotropic connectivity of the particles.
  
  
  RESULTS
  The results show an increase in porosity toward the bottom of the compact and showed a preferred orientation of the pores in the direction of compression.
  
  
  CONCLUSIONS
  The proposed method is suitable for analyzing the pore distribution quantitatively and for evaluating anisotropy.
authors.affiliation: Department of Pharmaceutical Technology and Biopharmacy, Groningen University Institute for Drug Exploration (GUIDE), Ant. Deusinglaan 1, 9713 AV, Groningen, The Netherlands. y.s.wu@rug.nl
authors.forename: Yu San
authors.initials: YS
authors.lastname: Wu
authors.forename: Henderik W
authors.initials: HW
authors.lastname: Frijlink
authors.forename: Lucas J
authors.initials: LJ
authors.lastname: van Vliet
authors.forename: Ietse
authors.initials: I
authors.lastname: Stokroos
authors.forename: Kees
authors.initials: K
authors.lastname: van der Voort Maarschalk
mesh_terms: D016880:Anisotropy; D004339:Drug Compounding; D007091:Image Processing, Computer-Assisted; D008855:Microscopy, Electron, Scanning; D016062:Porosity; D012965:Sodium Chloride; D013607:Tablets
chemical_list: D013607:Tablets; D012965:Sodium Chloride