Temperature dependent ultrasonic characterization of biological media

Abstract

Quantitative ultrasound (QUS) is an imaging technique that can be used to quantify tissue microstructure giving rise to scattered ultrasound. Other ultrasonic properties, e.g., sound speed and attenuation, of tissues have been estimated versus temperature elevation and found to have a dependence with temperature. Therefore, it is hypothesized that QUS parameters may be sensitive to changes in tissue microstructure due to temperature elevation. Ultrasonic backscatter experiments were performed on tissue-mimicking phantoms and freshly excised rabbit and beef liver samples. The phantoms were made of agar and contained either mouse mammary carcinoma cells (4T1) or chinese hamster ovary cells (CHO) as scatterers. All scatterers were uniformly distributed spatially at random throughout the phantoms. All the samples were scanned using a 20-MHz single-element f/3 transducer. Quantitative ultrasound parameters were estimated from the samples versus increases in temperature from 37C to 50 C in 1 C increments. Two QUS parameters were estimated from the backscatter coefficient [effective scatterer diameter (ESD) and effective acoustic concentration (EAC)] using a spherical Gaussian scattering model. Significant increases in ESD and decreases in EAC of 20%-40% were observed in the samples over the range of temperatures examined. The results of this study indicate that QUS parameters are sensitive to changes in temperature. Gaussian scattering model k wavelength Z 0 acoustic impedance of the surrounding medium Z acoustic impedance of the scatterers q density of the sample

Quantitative imaging of temperature elevations in tissues due to thermal therapies

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Quantitative ultrasound assessment of ultrasound therapy in rodent mammary tumors: In vivo and ex vivo results

“…3). This behavior is comparable to temperature-dependent BSC estimates in liver and cell pellets [21], though these estimates were generated under slightly different experimental conditions. Statistical analysis (MANOVA) did not reveal a significant difference between these four BSC curves examined together.…”

Real-time implementation of a dual-mode ultrasound array system: In vivo results

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