Pilot point temperature regulation for thermal lesion control during ultrasound thermal therapy

Abstract

The fundamental goal of ultrasound thermal therapy is to provide proper thermal lesion formations for effective tumour treatment. The quality of the therapy depends mostly on its positional precision. To date, most ultrasound thermal therapy treatments have focused on the formation of power or temperature patterns. The non-linear and time-delay effects of thermal dose formation prohibit direct control of the thermal dose distribution. In the paper, the control of thermal lesions by regulation of the temperature of a pilot point is proposed. This scheme utilises the high correlation between temperature elevation and thermal dose at the forward boundary of thermal lesions. To verify the feasibility, a 2D ultrasound phased array system was used to generate thermal lesions of various sizes, and the temperature elevation required to generate a thermal dose threshold was investigated. Results showed that the required temperature elevation was found to be a reasonably constant value of 52.5 degrees C under differing conditions when the focal area was small. When the focal area under consideration was large, the required temperature elevation became a monotonic function of blood perfusion rate, ranging from 49.2 to 52.5 degrees C. When the reference temperature of the pilot point was set at a conservative value (52.5 degrees C), the thermal lesions were controlled precisely under a wide range of blood perfusion and power pattern changes, tested by using a more realistic model that takes into account thermal-induced attenuation and blood perfusion changes. This changed the complex thermal dose control problem into a simple temperature regulation problem, which makes implementation of thermal lesion control easier, giving the scheme a high potential for application to current ultrasound thermal therapy systems.

A unified approach to combine temperature estimation and elastography for thermal lesion determination in focused ultrasound thermal therapy

“…Second, the tissue damage due to heating is accompanied by tissue expansion, which could also contaminate the echo time displacements. The transition in our experiments was observed when the local temperature change reached 20 • C (an absolute temperature of 50 • C), very close to tissue-denaturing temperature levels reported in the literature (Graham et al 1999, Liu et al 2004.…”

Prostate thermal therapy with high intensity transurethral ultrasound: The impact of pelvic bone heating on treatment delivery

“…The maximum temperature threshold was set at 85 C for the 3 cm and 4 cm gland, but increased to 90 C in the 5 cm gland in order to lower treatment time. Pilot-point treatment control was implemented at the target boundary [71]. For the planar and curvilinear applicators, power is applied and regulated as above to treat a narrow zone of the prostate, and successively rotated to the next scan position when the outer target boundary reaches the 52 C threshold.…”

Simultaneous temperature and magnetization transfer (MT) monitoring during high‐intensity focused ultrasound (HIFU) treatment: Preliminary investigation on ex vivo porcine muscle

“…The TD, which has been related to the equivalent heating time around 43°C, has thus been defined to estimate the effect of heating (18,19,32):…”