ivo drug delivery are of growing interest to device manufacturers, research scientists, and clinicians; however, most research characterizing controlled release formulations occurs in vitro because the spatial and temporal distribution of drug delivery is difficult to measure in vivo. In this work, in vivo magnetic resonance imaging (MRI of local drug delivery was performed to visualize and quantify the time resolved distribution of MRI contrast agents. Three-dimensional maps (generated from -weighted images with varied were processed using noise-reducing filtering. A segmented region of contrast, from a thresholded image, was converted to concentration maps using the equation , where and are the precontrast and postcontrast map values, respectively. In this technique, a uniform estimated value for was used. Error estimations were performed for each step. The practical usefulness of this method was assessed using comparisons between devices located in different locations both with and without contrast. The method using a uniform , requiring no registration of pre- and postcontrast image volumes, was compared to a method using either affine or deformation registrations.
Full text. Nuclear medicine imaging techniques have great potential in the study of the behaviour of drug formulations and drug delivery systems in human subjects. No other technique can locate so precisely the site of disintegration of a tablet in the Gl tract, the depth of penetration of a nebulized solution into the lung, or the residence time of a drug on the cornea. By using the gamma camera to image the in vivo distribution of pharmaceutical formulations radio labelled with a suitable gamma emitting radionuclide, images may be used to quantify the biodistribution, release and kinetics of drug formulations and delivery from novel carrier systems and devices. Radionuclide tracer techniques allow correlation between the observed pharmacological effects and the precise site of delivery. The strength of the technique lies in the quantitative nature of radionuclide images. Example will be shown of studies which examine the rate of transit of orally-administered formulations through the GI tract, as well as describing the development of devices for specific targeting of drugs to the colon. Data will also demonstrate the effectiveness of devices such as spacers in pulmonary drug delivery, in both normal volunteers, and in asthmatic subjects. Such studies not only provide data on the nature and characteristics of a product, such as reliability and reproducibility but, may also be used in submission to Regulatory Authorities in product registration dossiers
Jason A. Ellis
Full Text Available Effective treatment for glioblastoma (GBM will likely require targeted delivery of several specific pharmacological agents simultaneously. Intra-arterial (IA delivery is one technique for targeting the tumor site with multiple agents. Although IA chemotherapy for glioblastoma (GBM has been attempted since the 1950s, the predicted benefits remain unproven in clinical practice. This review focuses on innovative approaches to IA drug delivery in treating GBM. Guided by novel in vitro and in vivo optical measurements, newer pharmacokinetic models promise to better define the complex relationship between background cerebral blood flow and drug injection parameters. Advanced optical technologies and tracers, unique nanoparticles designs, new cellular targets, and rational drug formulations are continuously modifying the therapeutic landscape for GBM. Personalized treatment approaches are emerging; however, such tailored approaches will largely depend on effective drug delivery techniques and on the ability to simultaneously deliver multidrug regimens. These new paradigms for tumor-selective drug delivery herald dramatic improvements in the effectiveness of IA chemotherapy for GBM. Therefore, within this context of so-called “precision medicine,” the role of IA delivery for GBM is thoroughly reassessed.
Full Text Available Pharmaceutical scientists throughout the world are trying