Read-out of radiosensitive gels with ultrasound elastography: technique description and preliminary studies

摘要

Ultrasound methods to read dose distributions from radiosensitive gels have been proposed as a low cost alternative to the conventional read-out with magnetic resonance imaging. Previous work [1] showed a dose dependence of the speed of sound and ultrasound attenuation for different formulations of gels. Such properties depend largely on the bulk elastic modulus, the density, and molecular relaxation mechanisms initiated by the acoustic modulation of pressure, density and temperature. Since radiation-induced polymerisation generates longer molecules or even cross-links between molecules, it might be expected that elastic properties like the shear elastic modulus or Young's modulus would be useful alternative properties to investigate as read-out parameters. Furthermore, recent progress in the field of medical ultrasound elasticity imaging [2] has demonstrated that various algorithms can track ultrasound echoes from tissues during the application of a small external stress resulting in real-time images of the medium deformation (strain). This may be done in three dimensions. It appears therefore that all components of a future read-out technique based on elastic properties are coming into place.