Techniques in X-ray computed tomography in the evaluation of drug release systems and their application

Advancement of site-specific drug delivery systems has been hampered by the shortage of direct techniques for sampling and analysis of drug concentrations at the site of action. Because the potential target is often deeply imbedded within an organ, the local concentration of a drug delivered via implantable devices and its movement in tissue and vasculature (regarded as one significant aspect of pharmacokinetics) are often difficult to obtain with traditional methods like plasma and urine analysis, and alternative methods are highly sought after. Imaging is a natural candidate for this application. Thanks to modern technology, clinical imaging modalities with high spatial and temporal resolution combined with exceptional sensitivity and ease of use have greatly impacted the current diagnosis and treatment of diseases. Although all types of modalities are excellent candidates for pharmacokinetic imaging, X-ray Computed Tomography (CT) possesses a unique combination of speed, resolution and inherent simplicity in quantitative analysis that makes it an attractive choice. This chapter provides a general overview of CT methods in pharmacokinetic imaging with a specific application to the development and evaluation of a drug release system for local chemotherapy of liver tumors.