Magnetic Resonance Imaging and Its Applications to Solid Pharmaceutical Dosage Forms
Nuclear magnetic resonance (NMR) in the form of both spectroscopy and imaging are powerful tools in most areas of scientific research. NMR spectroscopy yields quantitative information such as chemical species concentration and their three-dimensional molecular structure. The addition of pulsed magnetic field gradients to a spectroscopic experiment then provides non-invasive localised information in three spatial dimensions, i.e., a magnetic resonance image. This powerful combination of magnetic resonance imaging with NMR spectroscopy makes it possible to probe local chemical, physical and mass transport phenomena (in the form of diffusion and flow) and is particularly suited to study the dissolution behaviour of solid pharmaceutical dosage forms. This Chapter will focus on the fundamentals of the theory behind quantitative magnetic resonance spectroscopy and imaging, and highlights the importance of understanding the origins of the various magnetic resonance contrast mechanisms that are inherent in the systems discussed. Examples will be drawn from both model and real pharmaceutical solid dosage forms undergoing dissolution testing in a USP-IV dissolution cell under pharmacopeial conditions to illustrate the ideas discussed in the main text.
KeywordsNuclear magnetic resonance Magnetic resonance imaging Dissolution Solid dosage forms Quantitative Mass-transport T1 and T2 relaxation
The author wishes to thank Dr Chen Chen (Charlie) for his assistance in preparing the manuscript and for expertly performing the data acquisition and processing of the results from the dissolution experiments on the model HPMC/TDFH dosage form.
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