Analysis of Coating Structures and Interfaces in Solid Oral Dosage Forms by Three Dimensional Terahertz Pulsed Imaging

Abstract

Three dimensional terahertz pulsed imaging (TPI) was evaluated as a novel tool for the nondestructive characterization of different solid oral dosage forms. The timedomain reflection signal of coherent pulsed light in the far infrared was used to investigate film-coated tablets, sugar-coated tablets, multilayered controlled release tablets, and soft gelatin capsules. It is possible to determine the spatial and statistical distribution of coating thickness in single and multiple coated products using 3D TPI. The measurements are nondestructive even for layers buried underneath other coating structures. The internal structure of coating materials can be analyzed. As the terahertz signal penetrates up to 3 mm into the dosage form interfaces between layers in multilayered tablets can be investigated. In soft gelatin capsules it is possible to measure the thickness of the gelatin layer and to characterize the seal between the gelatin layers for quality control. TPI is a unique approach for the nondestructive characterization and quality control of solid dosage forms. The measurements are fast and fully automated with the potential for much wider application of the technique in the process analytical technology scheme. ß

Terahertz-Wave Spectroscopy for Precise Histopathological Imaging of Tumor and Non-tumor Lesions in Paraffin Sections

“…However, THz waves can sufficiently identify molecular composition based on the vibration of the molecular framework, and are applicable to many analytical fields such as chemistry and pharmaceutics (Nishizawa et al 2003;Taday 2004;Wallace et al 2004b;Nishizawa 2005;Liu et al 2007;Zeitler et al 2007). …”

Terahertz technologies: present and future

“…Both pulsed and CW THz waves can be applied to tomographic imaging of layer structure of tablets, internal structures of objects, material inspection, security applications, etc. [42,43,44,45,46,47,48] In addition to the above limited examples, a wide range of nondestructive inspection and testing applications have been reported in order to find real and specific needs which cannot be duplicated by competing technologies.…”

Terahertz pulsed imaging in vivo: measurements and processing methods

“…This allows the frequency dependent complex dielectric permittivity to be directly calculated at terahertz frequencies. In addition to this useful ability, pulsed sources afford good axial resolution (30 μm has been reported, 17 however this is dependent on the refractive index of the medium). Although in-plane resolution is classically diffraction limited to approximately 200 μm (at 1.5 THz, dependent on frequency), there have been numerous studies exploring near-field techniques to overcome this limitation and increase resolution.…”