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Finite difference modelling of the temperature rise in non-linear medical ultrasound fields

Finite difference modelling of the temperature rise in non-linear medical ultrasound fields
Finite difference modelling of the temperature rise in non-linear medical ultrasound fields
Non-linear propagation of ultrasound can lead to increased heat generation in medical diagnostic imaging due to the preferential absorption of harmonics of the original frequency. A numerical model has been developed and tested that is capable of predicting the temperature rise due to a high amplitude ultrasound field. The acoustic field is modelled using a numerical solution to the Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation, known as the Bergen Code, which is implemented in cylindrical symmetric form. A finite difference representation of the thermal equations is used to calculate the resulting temperature rises. The model allows for the inclusion of a number of layers of tissue with different acoustic and thermal properties and accounts for the effects of non-linear propagation, direct heating by the transducer, thermal diffusion and perfusion in different tissues. The effect of temperature-dependent skin perfusion and variation in background temperature between the skin and deeper layers of the body are included. The model has been tested against analytic solutions for simple configurations and then used to estimate temperature rises in realistic obstetric situations. A pulsed 3 MHz transducer operating with an average acoustic power of 200 mW leads to a maximum steady state temperature rise inside the foetus of 1.25°C compared with a 0.6°C rise for the same transmitted power under linear propagation conditions. The largest temperature rise occurs at the skin surface, with the temperature rise at the foetus limited to less than 2°C for the range of conditions considered.
finite difference modelling, non-linear propagation, temperature
0041-624X
273-277
Divall, S.A.
a97fc542-0d7e-49d1-a124-7872a5e3ab68
Humphrey, V.F.
ece34fc9-f0a8-4aa7-808f-c43d7f7cd55a
Divall, S.A.
a97fc542-0d7e-49d1-a124-7872a5e3ab68
Humphrey, V.F.
ece34fc9-f0a8-4aa7-808f-c43d7f7cd55a

Divall, S.A. and Humphrey, V.F. (2000) Finite difference modelling of the temperature rise in non-linear medical ultrasound fields. Ultrasonics, 38 (1), 273-277. (doi:10.1016/S0041-624X(99)00121-3).

Record type: Article

Abstract

Non-linear propagation of ultrasound can lead to increased heat generation in medical diagnostic imaging due to the preferential absorption of harmonics of the original frequency. A numerical model has been developed and tested that is capable of predicting the temperature rise due to a high amplitude ultrasound field. The acoustic field is modelled using a numerical solution to the Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation, known as the Bergen Code, which is implemented in cylindrical symmetric form. A finite difference representation of the thermal equations is used to calculate the resulting temperature rises. The model allows for the inclusion of a number of layers of tissue with different acoustic and thermal properties and accounts for the effects of non-linear propagation, direct heating by the transducer, thermal diffusion and perfusion in different tissues. The effect of temperature-dependent skin perfusion and variation in background temperature between the skin and deeper layers of the body are included. The model has been tested against analytic solutions for simple configurations and then used to estimate temperature rises in realistic obstetric situations. A pulsed 3 MHz transducer operating with an average acoustic power of 200 mW leads to a maximum steady state temperature rise inside the foetus of 1.25°C compared with a 0.6°C rise for the same transmitted power under linear propagation conditions. The largest temperature rise occurs at the skin surface, with the temperature rise at the foetus limited to less than 2°C for the range of conditions considered.

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More information

Published date: 2000
Keywords: finite difference modelling, non-linear propagation, temperature

Identifiers

Local EPrints ID: 10148
URI: https://eprints.soton.ac.uk/id/eprint/10148
ISSN: 0041-624X
PURE UUID: b3510067-e5fc-49ea-a1e5-d851003f0b3d

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Date deposited: 26 May 2005
Last modified: 17 Jul 2017 17:07

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Contributors

Author: S.A. Divall
Author: V.F. Humphrey

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