Quantitative measurements of localized density variations in cylindrical tablets using X-ray microtomography

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Imaging Technology

Background:

• Direct compaction in tablet manufacturing often leads to heterogeneous density distributions within tablets.
• These density variations can significantly influence the overall mechanical properties and performance of pharmaceutical tablets.
• Quantitative analysis of density heterogeneity in direct compaction has been limited.

Purpose of the Study:

• To quantitatively evaluate the density profile and heterogeneity in microcrystalline cellulose compacts produced by direct compaction.
• To assess the impact of varying mean porosity on density distribution using X-ray tomography.
• To investigate the relationship between peripheral and central densities in pharmaceutical tablets.

Main Methods:

• Utilized X-ray microtomography (XRM) to analyze density distribution in microcrystalline cellulose (Vivapur 12) tablets.
• Studied the validity of the Beer-Lambert law for accurate XRM analysis.
• Performed density calibration and generated detailed density maps with color-scale plots.

Main Results:

• Confirmed significant density heterogeneity in microcrystalline cellulose compacts across a porosity range of 7.7% to 33.5%.
• Quantified higher densities in the peripheral regions compared to the central regions of the tablets.
• Demonstrated the effectiveness of XRM in visualizing and quantifying density variations.

Conclusions:

• Direct compaction results in notable density variations within tablets, particularly higher densities at the periphery.
• X-ray tomography is a valuable tool for the quantitative assessment of density heterogeneity in pharmaceutical compacts.
• Mechanical properties should be evaluated considering both bulk and surface characteristics, as surface measurements like Brinell hardness may not represent the entire tablet.