Measurement of Gd-DTPA diffusion though PVA hydrogel using a novel magnetic resonance imaging method

Department of Chemical and Biochemical Engineering, University of Western Ontario, London, Ontario, N6A 5B9, Canada.
Biotechnology and Bioengineering (Impact Factor: 4.13). 12/1999; 65(4):459-67. DOI: 10.1002/(SICI)1097-0290(19991120)65:43.0.CO;2-O
Source: PubMed


Polyvinyl alcohol-cryogel (PVA-C) is a hydrogel that is an excellent tissue mimic. In order to characterize mass transfer in this material, as well as to demonstrate in principle the ability to noninvasively measure solute diffusion in tissue, we measured the diffusion coefficient of the magnetic resonance (MR) contrast agent gadolinium diethylene triaminopentaacetic acid (Gd-DTPA) through PVA-C using a clinical MR imager. The method involved filling thick-walled rectangular PVA-C "cups" with known concentrations of Gd-DTPA solutions. Then by using a fast inversion recovery spin echo MR imaging protocol, a signal "null" contour was created in the MR image that corresponded to a second, known concentration of Gd-DTPA. By collecting a series of MR images through the PVA-C wall as a function of time, the displacement of this second known isoconcentration contour could be tracked. Application of Fick's second law of diffusion yielded the diffusion coefficient. Seven separate experiments were performed using various combinations of initial concentrations of Gd-DTPA within the PVA-C cups (3.2, 25.6, or 125 mM) and tracked isoconcentrations contours (0.096, 0.182, or 0.435 mM Gd-DTPA). The experimental results and the predictions of Fick's law were in excellent agreement. The diffusivity of Gd-DTPA through 10% PVA hydrogel was found to be (2.6 +/- 0.04) x 10(-10) m(2)/s (mean +/- s.e.m.). Separate permeability studies showed that the diffusion coefficient of Gd-DTPA through this hydrogel did not change with an applied pressure of up to 7.1 kPa. Accurate measurements could be made within 30 min if suitable Gd-DTPA concentrations were selected. Due to the excellent repeatability and fast data acquisition time, this technique is very promising for future in vivo studies of species transport in tissue.

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    • "However, the application of contrast agents in NMR microscopy is relatively uncommon. Examples of such applications are characterizations of CA diffusion in hydrogels [7] [8] and measurements of concentration maps of CA in animal cell bioreactor systems [9]. Here, we use Cu ions and the chelate Gd-DTPA as contrast agents for probing the permeability of microcapsules. "
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    Journal of Magnetic Resonance 05/2012; 221:11-8. DOI:10.1016/j.jmr.2012.05.009 · 2.51 Impact Factor
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    • "Included structures can be used for reference marker points, and may be constructed of PVA-C, to benefit from its multi-modal properties, or of a different material, like plastic pellets or pockets of MR contrast agents. It was found, however, that any soluble liquid would not stay localized, but would diffuse through the phantom, as found using gadolinium (Gordon et al 1999). "
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    ABSTRACT: Poly(vinyl alcohol) cryogel, PVA-C, is presented as a tissue-mimicking material, suitable for application in magnetic resonance (MR) imaging and ultrasound imaging. A 10% by weight poly(vinyl alcohol) in water solution was used to form PVA-C, which is solidified through a freeze-thaw process. The number of freeze-thaw cycles affects the properties of the material. The ultrasound and MR imaging characteristics were investigated using cylindrical samples of PVA-C. The speed of sound was found to range from 1520 to 1540 m s(-1), and the attenuation coefficients were in the range of 0.075-0.28 dB (cm MHz)(-1). T1 and T2 relaxation values were found to be 718-1034 ms and 108-175 ms, respectively. We also present applications of this material in an anthropomorphic brain phantom, a multi-volume stenosed vessel phantom and breast biopsy phantoms. Some suggestions are made for how best to handle this material in the phantom design and development process.
    Physics in Medicine and Biology 01/2005; 49(24):5529-46. DOI:10.1088/0031-9155/49/24/009 · 2.76 Impact Factor
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    ABSTRACT: Thesis research directed by: Chemical Engineering. Title from t.p. of PDF. Thesis (Ph. D.) -- University of Maryland, College Park, 2004. Includes bibliographical references. Text.
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