Journal article
Thermodynamics of movable inductively heated seeds for the treatment of brain tumors
Medical physics (Lancaster), Vol.18(4), pp.794-803
07/1991
DOI: 10.1118/1.596633
PMID: 1921889
Abstract
A thermodynamic study is presented of temperature distributions created by an inductively heated 6‐mm‐diam Ni sphere imbedded i
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o and i
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o into porcine brain tissue. This study was performed in support of the development of a system that creates localized heat‐induced lesions in deep‐seated brain tumors. In this system, a magnetic ‘‘seed’’ will be remotely repositioned within the brain by an externally produced magnetic field. Convective effects of a hot moving seed will produce a different thermodynamic situation than that arising from an array of static implants. In this work, a study is presented of part of the expected change, in which a static sphere is heated to high temperature. Measurements were made of the temporal and spatial dependence of the temperature rise in the vicinity of the heated sphere, i
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o in four animals and in one that was euthanized immediately prior to experimentation. These results are used for parameter estimation with a theoretical model based on a point source solution to a form of the thermal diffusion equation, i.e., the ‘‘bioheat transfer equation.’’ With this model thermal distributions from a power source of arbitrary geometry can be found using appropriate integration methods, and the method has widespread applicability. Estimates of blood flow rates, tissue thermal conductivity, and seed power absorption were found using the parameter estimation algorithm. The estimated blood perfusion exhibits a step increase following the first heating in multiple heating experiments. Thermal conductivity estimated using data from the nonperfused (i
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o) animal is 0.6 W/m °C. Seed power absorption is estimated correspondingly to be 0.9 W, a result confirmed independently with calorimetry. Statistical uncertainty is established for the radial decrease of the tissue temperature rise created by this method. This result allows estimation of a cell death boundary uncertainty of 0.6 mm, caused by fluctuations in power delivered to the seed, uncertainty in the temperature probe placements, and thermal properties such as blood perfusion and tissue thermal conductivity.
Details
- Title: Subtitle
- Thermodynamics of movable inductively heated seeds for the treatment of brain tumors
- Creators
- J. A Molloy - Department of Physics, University of Virginia, Charlottesville, Virginia 22901R. C Ritter - Department of Physics, University of Virginia, Charlottesville, Virginia 22901W. C Broaddus - Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia 22908M. S Grady - Department of Neurological Surgery, University of Washington, Seattle, Washington 98104M. A Howard - Department of Neurological Surgery, University of Washington, Seattle, Washington 98104E. G Quate - Department of Nuclear Engineering and Engineering Physics, University of Virginia, Charlottesville, Virginia 22901G. T Gillies - Department of Nuclear Engineering and Engineering Physics, University of Virginia, Charlottesville, Virginia 22901
- Resource Type
- Journal article
- Publication Details
- Medical physics (Lancaster), Vol.18(4), pp.794-803
- DOI
- 10.1118/1.596633
- PMID
- 1921889
- ISSN
- 0094-2405
- eISSN
- 2473-4209
- Number of pages
- 10
- Date published
- 07/1991
- Academic Unit
- Neurology; Iowa Neuroscience Institute; Neurosurgery; Otolaryngology
- Record Identifier
- 9984020770202771
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