A feasibility study of ultrasound as a monitoring method for hyperthermia therapy

Abstract

Hyperthermia therapy is one of the therapy method used for cancer treatment. It has shown to be an effective way of treating the cancerous tissue when compared to surgery, chemotherapy and radiation. However, hyperthermia needs a real time monitoring method in ensuring a consistent heat delivery and preventing any damages to the nearby tissue. Ultrasound is one of the modalities that have great potential for local hyperthermia monitoring, as it is nonionizing, convenient, and has relatively simple signal processing requirement compared to Magnetic Resonance Imaging (MRI) and Computed Tomography (CT). B-Mode ultrasound provides sufficient temperature sensitivity and yields good spatial resolution for thermal monitoring meanwhile A Mode ultrasound involves only one-dimensional (1D) signal processing which enables a quantitative measurement on different types of breast tissues to be conducted faster. Therefore, this study was conducted to investigate and to compare the most optimum ultrasound temperature dependent's parameters in normal and pathological breast tissue between A-Mode and B-Mode ultrasound which involve the measurement of the attenuation and backscatter coefficients for A-Mode and determination of pixels value and standard deviation for B-Mode. For this purpose, a series of experiment was conducted on 40 female Sprague Dawley rats in which 30 pathological rats were used as infected study while 10 of healthy rats were group as control purposes. The pathological and normal rats were dissected and exposed to hyperthermia at 40°C, 45°C, 50°C and 55°C. Meanwhile, at 37°C was used as normal body temperature before hyperthermia. A-Mode and B-Mode of 7.5Mhz and 6Mhz was used simultaneously before, during and after the hyperthermia exposure. Result obtained shows that, for A-Mode, in both normal and infected tissue, the temperature value of 45°C was chosen to be an optimum temperature dependent for attenuation calculation and temperature value of 40°C was selected for backscatter energy. In B-Mode analysis, based on pixel values calculation of segmented area, result shows in normal tissues where the temperature value of 40°C was chosen, the standard deviation of 11.779 was obtained. Meanwhile for infected tissue condition, at 50°C the standard deviation value shown to be 7.95 as compared to the others temperature. Therefore, it is shown that, a combination of both A-Mode and B-Mode ultrasound can be used as another potential approach since its attenuation and backscatter coefficient of A-Mode, the pixels value and standard deviation of B-Mode is very sensitive to the tissue structure in monitoring hyperthermia therapy with respect to the changes of temperature.