Electrical impedance tomography for three-dimensional drug release monitoring

Department of Physics and Mathematics, University of Eastern Finland, Kuopio, Finland.
European journal of pharmaceutical sciences: official journal of the European Federation for Pharmaceutical Sciences (Impact Factor: 3.35). 10/2010; 41(2):407-13. DOI: 10.1016/j.ejps.2010.07.008
Source: PubMed


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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    • "The algorithms in the latter category were implemented through the calculation of the Dirichlet-to-Neumann map or Neumann-to-Dirichlet map, and the gray value at each pixel can be calculated directly and independently [11]–[14]. In recent years, 3-D ERT are used to monitor drug release three-dimensionally as a function of time [15], to serve as an adjunct modality for enhancing standard clinical ultrasound imaging of the prostate [16], to image the rapidly varying objects in the flow pipes [17], and to monitor sedimentation in the control and optimization of industrial sedimentation processes [18] and etc. Compared with the 2-D ERT, the 3-D ERT requires more spatial information; as a result, usually more electrodes are required. "
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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. DOI:10.1109/TIM.2012.2232475 · 1.79 Impact Factor
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    • "Electrical Impedance Tomography (EIT) is a technique that uses a set of electrodes surrounding a body to reconstruct the distribution of material inside (usually by visualizing the material's electrical conductivity). This technique has promising applications in medical monitoring, especially in the monitoring of ventilation and perfusion, diagnosis of pulmonary edema and pulmonary embolus , and in the detection of breast cancer [1] [2] [3] [4]. Usually, EIT determines the conductivity within the interior of a body (the sensing region) by measuring voltages on the surface, obtained on the basis of current patterns that are applied on the boundaries. "
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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. DOI:10.1088/1748-0221/8/03/P03004 · 1.40 Impact Factor
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    ABSTRACT: Despite decades of research, the study of suspension flows still continues to be a subject of great scientific interest. In the development of accurate models for suspension-related processes, prior knowledge of several flow characteristics is essential, such as spatial distribution of phases, flow regimen, relative velocity between phases, etc. Several non-invasive techniques of flow characterisation can be found in the literature, however, electrical tomography offers a vast field of possibilities due to its low cost, portability and, above all, safety of handling. In this paper, a review of the use of electrical tomography for industrial/process monitoring purposes will be presented, giving information about the evolution throughout the years and about the limitations and advantages of the different configurations. Moreover, the signal de-convolution strategies, to obtain the images of the process, will also be discussed. The most recent advances in both fields will be presented. Additionally, information about the strategy adopted by the authors to produce a portable EIT system will be described. Finally, the future challenges for electrical tomography will be addressed.
    Powder and particle 12/2011; 29. DOI:10.14356/kona.2011010 · 1.18 Impact Factor
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