Fully tuned RBF neural network controller for ultrasound hyperthermia cancer tumour therapy.

Thermal dose is an important clinical efficacy index for hyperthermia cancer treatment. This paper presents a new direct radial basis function (RBF) neural network controller for high-temperature hyperthermia thermal dose during the therapeutic procedure of cancer tumours by short-time pulses of high-intensity focused ultrasound (HIFU). The developed controller is stabilized and automatically tuned based on Lyapunov functions and ant colony optimization (ACO) algorithm, respectively. In addition, this thermal dose control system has been validated using one-dimensional (1-D) biothermal tissue model. Simulation results showed that the fully tuned RBF neural network controller outperforms other controllers in the previous studies by achieving targeted thermal dose with shortest treatment times less than 13.5 min, avoiding the tissue cavitation during the thermal therapy. Moreover, the maximum value of its mean integral time absolute error (MTAE) is 98.64, which is significantly less than the resulted errors for the manual-tuned controller under the same treatment conditions of all tested cases. In this study, integrated ACO method with robust RBF neural network controller provides a successful and improved performance to deliver accurate thermal dose of hyperthermia cancer tumour treatment using the focused ultrasound transducer without external cooling effect.

Measurement of thermal and ultrasonic properties of some biological tissues.

The measurement of thermal and ultrasonic properties of biological tissues is essential for the assessment of the temperature rise induced in vivo by diagnostic ultrasound. In this paper, we present measurements of thermal conductivity, thermal diffusivity, speed of sound and ultrasonic attenuation of fresh ex vivo porcine tissue, namely 'muscle' (from abdomen and leg), 'skin with subcutaneous fat' (from abdomen and leg), 'abdominal fat' and 'bone'. The measurements of the thermal properties of biological tissue samples are based on a transient method. Thermal property measurements show that subcutaneous fat has the lowest thermal conductivity (0.23 W m(-1) K(-1)), while muscle gives the highest values (0.46 W m(-1) K(-1)). Thermal diffusivity of muscle tissue recorded the highest value among the studied tissues (0.16 mm(2) s(-1)) while that of skin with subcutaneous fat gave the lowest value (0.11 mm(2) s(-1)). A scanning acoustic macroscope was used to measure attenuation coefficient and speed of sound for the tissue samples. The results for the speed of sound are broadly similar to those reported in the literature. The power law dependence of the attenuation coefficient of the form eta = a f (b) as a function of frequency was found to be more appropriate than the linear fit in this study.

A functional cardiovascular model with disorders.

This paper introduces a functional model of the cardiovascular system that is capable of describing its behavior in normal as well as pathologic cases. The developed model includes all the main compartments of the circulatory system and also the baroreflex-feedback regulatory mechanism. The model response to the incorporation of two critical cardiovascular disorders namely hypertension and acute congestive heart failure is realistic and within the expected range of the results of the literature experimental data.

The relationship between nuclear colour and opalescence on the LOCSIII scale and physical characteristics of cataract nuclei.

PURPOSE: To evaluate the compression characteristics of the human lens nucleocortex in relation to its LOCSIII clinical grading. METHODS: Sixteen subjects undergoing planned extracapsular cataract surgery had pre-operative slit-lamp examination and assessment of cataract LOCSIII grade followed by postoperative in vitro evaluation of the nucleus with measurement of 'linear compressibility' by a purpose-designed caliper incorporating a strain gauge, enabling the derivation of a graph of nuclear compression (D (mm) against applied force (F (N)). RESULTS: Nuclear colour correlates with the force required to compress a lens to 75% of its original depth (F75) (R = 0.625, P = 0.017). Nuclear opalescence correlates with the force required to compress a lens to 75% of its original depth (R = 0.651, P = 0.012) and inversely with linear compressibility (DeltaD/DeltaF, the slope of the graph of nuclear compression against applied force) (R = -0.610, P = 0.014). F75 is a direct and linear compressibility is an inverse related parameter of lens nucleus 'hardness'. CONCLUSION: A new instrument is described which allows measurement of 'hardness'-related compression characteristics of the human cataract in vitro. There is a relationship between the LOCSIII clinical classification of nuclear cataracts and mechanical compression characteristics of the cataractous lens. LOCSIII classification may aid the preoperative planning of an appropriate surgical approach to an individual cataract.