Scanning path optimization for ultrasound surgery (original) (raw)
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Optimal Control Methods for Ultrasound Surgery
In this paper, a two-stage control method is proposed to control thermal dose and temperature in ultrasound surgery. The first part in the proposed scheme consists of nonlinear model-based feedforward control. The focusing as well as the scanning path of the foci is chosen by the feedforward controller. The presented feedforward scheme leads to a large dimensional nonlinear control problem which is solved with gradient based algorithm. The temperature measurements during the ultrasound surgery can be adopted from the magnetic resonance imaging (MRI). In the second part of the control scheme these temperature measurements with LQG feedback control and Kalman filter are used to compensate the modeling errors which may arise in the feedforward part. The LQG controller and Kalman filter are derived by linearizing the original nonlinear state equation with respect to the feedforward control trajectories. The presented control scheme is tested with numerical simulations and feasible solutions can be achieved with both feedback and feedforward controllers. In addition, simulations indicate that the LQG scheme can compensate large modeling errors.
Optimal Control In High Intensity Focused Ultrasound Surgery
Optimization in Medicine, 2008
Summary. When an ultrasound wave is focused in biological tissue, a part of the energy of the wave is absorbed and turned into heat. This phenomena is used as a dis-tributed heat source in ultrasound surgery, in which the aim is to destroy cancerous tissue by causing thermal ...
Modeling Focused Ultrasound Exposure for the Optimal Control of Thermal Dose Distribution
The Scientific World Journal, 2012
Preclinical studies indicate that focused ultrasound at exposure conditions close to the threshold for thermal damage can increase drug delivery at the focal region. Although these results are promising, the optimal control of temperature still remains a challenge. To address this issue, computer-simulated ultrasound treatments have been performed. When the treatments are delivered without taking into account the cooling effect exerted by the blood flow, the resulting thermal dose is highly variable with regions of thermal damage, regions of underdosage close to the vessels, and areas in between these two extremes. When the power deposition is adjusted so that the peak thermal dose remains close to the threshold for thermal damage, the thermal dose is more uniformly distributed but under-dosage is still visible around the thermally significant vessels. The results of these simulations suggest that, for focused ultrasound, as for other delivery methods, the only way to control temper...
Feedforward and Feedback Control of Ultrasound Surgery
Applied Numerical …, 2006
In this paper, a two stage method is used to control the thermal dose distribution in ultrasound surgery. In the first stage, a model-based nonlinear optimal control problem is solved, leading to an optimal feedforward thermal dose distribution. The control inputs are the real and ...
Fast estimation model of pressure-temperature response for planning focused ultrasound surgery
2017
FAST ESTIMATION MODEL OF PRESSURE-TEMPERATURE RESPONSE FOR PLANNING FOCUSED ULTRASOUND SURGERY by Tariq Mohammad Arif High Intensity Focused Ultrasound (HIFU) is becoming a widely accepted modality for extracorporeal non-invasive hyperthermia and surgical procedures. Since ultrasonic transducers need to operate in various challenging body locations, the arrangement of their array elements can be optimized to improve the capability of controlling focus intensity. In the first part of this dissertation, patterns of pressure field variations with several selected design variables (kerf, transducer element’s number and element’s width-height) are studied. These patterns indicate that there is a more suitable shape and arrangement of transducer elements in a specified area to achieve highest possible pressure. In order to obtain this arrangement, a Genetic Algorithm (GA) based evolutionary global search method is used to optimize the design shape and the distribution of ultrasonic transd...
Mathematical Modelling of Breast Cancer Thermo-therapy Treatment : Ultrasound-based Approach
2016
Breast cancer is a disease which affects the cells in the breast, it caused by an uncontrolled division of abnormal cells that can be either benign or malignant in the breast tissues. In this study, models of an ultrasound spherical phased tissue that can be used for thermotherapy treatment of tumours in the intact breast are presented. The first analytical model, examines the temperature rise in the tissue due to ultrasound without metabolic heat source and the heat deposition in the biological tissues and also 3-Dimensional temperature distribution during ultrasound thermotherapy. In the second model a modified heat transfer equation was used to compute temperature profiles with the addition of metabolic heat source in the tissue. The presented models show that for a comparatively small tumour (2 cm in diameter) and a point heat source set at 45 C , only a small portion in the internal part of the tumour would be damaged and/or destroyed within a duration of about 100 seconds. The...
Pilot point temperature regulation for thermal lesion control during ultrasound thermal therapy
Medical & Biological Engineering & Computing, 2004
The fundamenta/ goa/ of u/trasound therma/ 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°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 ° C. When the reference temperature of the pilot point was set at a conservative value (52.5 ° 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.
The aim of this study is to investigate the feasibility of the heating on the tumor periphery by using high intensity focused ultrasound (HIFU) during thermal surgery. The pressure field induced by high intensity focused ultrasound transducer was solved by the Rayleigh-Sommerfeld diffraction integral. The temperature distribution was solved by the Pennes bioheat transfer equation. Numerical results show that even in the tumor periphery with high blood perfusion the thermal lesion can effectively cover the wanted therapeutic region for a rapid HIFU heating. The modality of heating on the tumor periphery by using high intensity focused ultrasound may provide an approach to eradication of a solid tumor with high blood perfusion in the periphery.
A numerical study on thermal ablation of brain tumor with intraoperative focused ultrasound
Journal of Thermal Biology, 2019
Focused ultrasound surgery (FUS) is a non-invasive thermal therapeutic method which has been emerged in the field of brain tumors treatment. During intraoperative brain surgery, application of FUS can significantly increase the accuracy of thermal ablation of tumor while reducing undesirable damage to healthy brain tissue. The main objective of this study is acquiring acoustic transducer specifications to achieve optimum thermal treatment in the tumoral tissue. 2D and 3D models are constructed from patient-specific brain MRI images which consist of a malignant vascular tumor. Acoustic pressure and temperature are obtained by using homogenous Helmholtz and bio-heat transfer equations according to insignificant nonlinear effect. Besides that, thermal lesion induced by FUS is obtained by the thermal dose function. Results show the significance of blood vessels' cooling effect on the temperature profile. Moreover, correlation between temperature profile and transducer's operating parameter including power, frequency and duty cycle is obtained. Artificial neural network analysis is conducted to estimate required transducer parameters for optimum temperature rise.