Electrical impedance tomography for three-dimensional drug release monitoring.
ABSTRACT Electrical impedance tomography (EIT) was adapted to monitor drug release three-dimensionally as a function of time. EIT is an electrical imaging modality in which the three-dimensional conductivity distribution inside an object is computed based on electrical measurements from the boundaries. Here, the three-dimensional concentration distribution was monitored with the help of the experimentally determined relationship between drug concentration and conductivity. The EIT monitoring was carried out with propranolol hydrochloride tablets in an apparatus similar to USP dissolution apparatus 2. The release profiles estimated using EIT matched well with the UV/VIS spectrophotometric analyses that were performed as a reference. There are several benefits conferred by three-dimensional monitoring, i.e., comprehensive information about the release process; no need to take samples during experiments; and not essential to assume homogenous concentration distribution in the drug release analysis. EIT is an in-line technique, and moreover, it is non-intrusive and non-invasive. The possibilities and the characteristics of the EIT monitoring are described in detail, and some potential drug release applications are proposed. EIT is especially encouraged to be exploited for research and development purposes.
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ABSTRACT: Adirect reconstruction method for three-dimensional (3-D) electrical resistance tomography was introduced by using the factorization method. Compared with the traditional image reconstruction algorithms based on the sensitivity/Jacobian matrix, the conductivity distribution in any part of the 3-D region of interest can be obtained directly and independently. A new way to calculate the Neumann-to-Dirichlet map was also introduced by using the adjacent current pattern. Several phantoms were constructed for image reconstruction in three dimensions. The data were collected from 16 electrodes on a single cross section, which can be only used to produce two-dimensional images in the literature. Neither matrix inversion nor iteration was used in the process of image reconstruction. The reconstructed results validated the feasibility of the method.IEEE Transactions on Instrumentation and Measurement 05/2013; 62(5):999-1007. · 1.36 Impact Factor
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ABSTRACT: In this paper, Calderon’s method is applied to a chest-like sensing region, as monitored by electrical impedance tomography. This method provides a direct algorithm for image reconstruction, where the gray value at any pixel of the reconstructed image is computed using a direct and independent approach. The major calculations of image reconstruction in Calderon’s method are implemented for a circular boundary and, as a result, the complicated calculations of the scattering transform, as required by non-circular boundaries, are avoided. A unique conformal transformation is used to map a unit disk onto a sensing region with a non-circular boundary, such as a chest-like region. A new method to calculate the Dirichlet-to-Neumann map is also introduced, which is used to compute the scattering transform. The feasibility of the proposed method has been validated by testing the construction of phantoms with chest-like boundaries. Data collected from the chest of a male subject has been used to visualize lung movement, as monitored by the electrical impedance tomography system.Journal of Instrumentation 03/2013; 8(3):P03004. · 1.66 Impact Factor