Sensitivity study of the acoustic nonlinearity parameter for measuring temperatures during High Intensity Focused Ultrasound treatment

Abstract

The aim of High Intensity Focused Ultrasound (HIFU) is to locally increase the temperature in a body. For an adequate application of the treatment it is important to measure non-invasively the temperature profiles in the heated region. Most efficiently, this is done with the same modality as being used for heating. Consequently, the preferred measuring method should rely on the temperature dependence of an acoustic medium parameter. The goal of this study is to determine which parameter is most sensitive to temperature changes. To find the most suitable parameter, the temperature dependence of the speed of sound (SOS), the density of mass and the acoustic nonlinearity parameter B/A are compared for water. The temperature dependence of the SOS and the mass density are obtained by interpolating values found in literature. Since measured values of the B/A parameter are only known for a few coarsely distributed temperature values, it has been synthesised from a two-dimensional function describing the SOS versus temperature and pressure. It turns out that the B/A parameter is far more sensitive for temperature changes than the other parameters. Comparison with measured B/A values confirms the idea that nonlinear acoustics is a favourite candidate to measure temperature profiles.

The acoustical properties of IEC agar-based tissue mimicking material over the frequency range 4.5MHz to 50MHz - a longitudinal study

“…The 3 dB bandwidths of the Vevo 770® transducers were measured at room temperature in this thesis. Additional probe characterisation at human body temperature may be needed due to the variations in the nonlinear parameters of degassed deionised water (Van Dongen & Verweij, 2008) found at higher temperatures . It is known that nonlinear effects of degassed water increase with increasing temperature (Van Dongen & Verweij, 2008).…”

“…Additional probe characterisation at human body temperature may be needed due to the variations in the nonlinear parameters of degassed deionised water (Van Dongen & Verweij, 2008) found at higher temperatures . It is known that nonlinear effects of degassed water increase with increasing temperature (Van Dongen & Verweij, 2008). Van Dongen et al, (2008) Based on the data provided in Chapters 3, 4 and 5, in order to manufacture a QA phantom which is relevant at higher frequencies; a TMM should be developed to closely match the SoS and the attenuation of small animal soft tissue at these ultrasound frequencies.…”

“…It is known that nonlinear effects of degassed water increase with increasing temperature (Van Dongen & Verweij, 2008). Van Dongen et al, (2008) Based on the data provided in Chapters 3, 4 and 5, in order to manufacture a QA phantom which is relevant at higher frequencies; a TMM should be developed to closely match the SoS and the attenuation of small animal soft tissue at these ultrasound frequencies. In order to produce a TMM suitable for high frequency QA phantoms some extra steps need to be taken.…”

A feasibility study for non-invasive thermometry using non-linear ultrasound

“…Even when the treatment planning is being based on non-linear acoustics, the restricted knowledge about tissue boundaries and tissue behaviour, and the formation of bubbles and cavitation, will lead to uncertainties that call for thermometry during treatment. On the other hand, as this paper confirms, the acoustic nonlinearity parameter B/A is very sensitive to the temperature changes [44,45,61] and may be the best choice as a basis for non-invasive thermometry. A practical issue that needs to be overcome is the restricted quantitative knowledge about the temperature dependency of B/A (and other relevant acoustic parameters) for many biological tissues.…”

Ultrasound coefficient of nonlinearity imaging

“…The coefficient of nonlinearity β is a particularly suitable feature for discriminating the tissues relevant to this application, because fatty tissues are known to have a high coefficient of nonlinearity [1]. In addition to the possibility of employing β for tissue discrimination, using it to obtain information about temperature variations might also be possible [8]. Monitoring temperature variations is not only of interest during cardiac ablation; it could also be utilized during, e.g., high-intensity focused ultrasound and hyperthermia for cancer treatment.…”