Influence of the Transducer Acoustic Power on Focal Location of the Beam During HIFU Ablation Procedure

2012 ◽  
Author(s):  
Seyed Ahmad Reza Dibaji ◽  
Rupak K. Banerjee
Keyword(s):  
Experimental Data ◽  
Temperature Rise ◽  
Inverse Method ◽  
Focused Ultrasound ◽  
Clinical Importance ◽  
Acoustic Power ◽  
High Intensity Focused Ultrasound ◽  
Focal Distance ◽  
Initial Location ◽  
Tissue Mimicking Material

The location of High Intensity Focused Ultrasound (HIFU) beam in a tissue medium is an important parameter in assessment of the thermal field as it influences the temperature rise in the tissue. Our hypothesis is that the location of the beam can be affected by the power of the transducer. HIFU procedure with 30s of sonication time was performed at different powers of transducer (5 to 60 W) as well as different initial locations of beam in a tissue mimicking material. Eight thermocouples were embedded at 4 different layers in a phantom to measure the temperature rise during HIFU procedure. An inverse method based on experimental data and optimization algorithm was used to find the actual location of beam based on the experimental data. Our experimental data showed that for a higher power (60 W) as compared to a lower power (5 W), the focal distance that the actual position of beam moves away from its initial location increased with the raise in power. Thus, beam location can change at different powers of transducer. Using inverse method we showed that there is a direct linear correlation (R2 = 0.95) between the transducer power and the distance that beam moves away from its initial location. Therefore, it is of great clinical importance to study the effects of transducer power on the location of HIFU beam in an attempt to minimize the damage to healthy cells.

Temperature Rise in Tissue Mimicking Material During HIFU Procedures

2007 ◽  
Author(s):  
Subhashish Dasgupta ◽  
Prasanna Hariharan ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
Temperature Rise ◽  
Focused Ultrasound ◽  
Acoustic Power ◽  
Tumor Ablation ◽  
High Intensity Focused Ultrasound ◽  
Tissue Temperature ◽  
Invasive Technique ◽  
Operational Parameters ◽  
Tissue Mimicking Material

High Intensity Focused Ultrasound (HIFU) has shown considerable promise as a minimally-invasive technique for various therapeutic applications such as tumor ablation and vessel cauterization. The efficacies of these HIFU procedures depend on various operational parameters such as total acoustic power, pulse duration and transducer dimensions. In this study, the effect of total acoustic power on the tissue temperature rise is studied both experimentally and numerically. Experimentally, HIFU ablations, at different acoustic powers, were carried out in a tissue mimicking material embedded with thermocouples. Temperature rise measured from the in-vitro experiments were then validated with the numerical computations. Results show that experimental and numerical temperature rise match accurately. Our numerical model was able to predict the peak temperature rise within ∼12% of the experimental results. Results also show that the tissue temperature rise is linearly proportional to the input acoustic power. For the acoustic power levels considered in this study, the results suggest that acoustic non-linearity does not play a major role on the tumor ablation procedure.

High Intensity Focused Ultrasound (HIFU) Transducer Characterization Using Acoustic Streaming

2007 ◽  
Author(s):  
Prasanna Hariharan ◽  
Ronald A. Robinson ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
High Intensity ◽  
Focused Ultrasound ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Acoustic Streaming ◽  
Acoustic Power ◽  
High Intensity Focused Ultrasound ◽  
Medical Ultrasound ◽  
Intensity Field ◽  
Streaming Velocity

A new, non-perturbing optical measurement technique was developed to characterize medical ultrasound fields generated by High Intensity Focused Ultrasound (HIFU) transducers using a phenomenon called ‘acoustic streaming’. The acoustic streaming velocity generated by HIFU transducers was measured experimentally using Digital Particle Image Velocimetry (DPIV). The streaming velocity was then calculated numerically using the finite-element method. An optimization algorithm was developed to back-calculate acoustic power and intensity field by minimizing the difference between experimental and numerical streaming velocities. The intensity field and acoustic power calculated using this approach was validated with standard measurement techniques. Results showed that the inverse method was able to predict acoustic power and intensity fields within 10% of the actual value measured using standard techniques, at the low powers where standard methods can be safely applied. This technique is also potentially useful for evaluating medical ultrasound transducers at the higher power levels used in clinical practice.

Delineation of Noise Signals From MRI Measured Temperature Rise During HIFU Ablation Procedure

2011 ◽  
Author(s):  
Subhashish Dasgupta ◽  
Seyed Ahmed Dibaji ◽  
Janaka Wansapura ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
Temperature Rise ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Heat Equations ◽  
Intensity Level ◽  
Measured Temperature ◽  
Mr Thermometry ◽  
Porcine Liver ◽  
Heating Phase ◽  
Set Up

A relatively recent and non invasive method for characterizing thermal fields generated by high intensity focused ultrasound (HIFU) transducers is Magnetic Resonance (MR) Thermometry method. However, noise signals generated by external RF sources infiltrate the scanner orifice and limit its ability to measure temperature rise during the heating or ablation phase. In this study, MRI monitored HIFU ablations are performed on freshly excised porcine liver samples, at varying sonication times, 20, 30 and 40 s at a constant acoustic intensity level of 1244 W/cm2. Temperature rise during the procedure is measured using Proton Resonant Frequency MR thermometry. Preliminary experiments without an adequate noise filter, failed to record temperature rise during the heating phase. A low pass R-C filter circuit is subsequently incorporated into the experimental set up to prevent infiltration of noise signals in the MRI orifice. This modified RC filter enables measurement of temperature rise during the heating phase followed by temperature decay during cooling. The measured data is within 12% agreement with the temperature rise computed by solving the acoustic and heat equations.

scholarly journals Estimation of Acoustic Power Output from Electrical Impedance Measurements

Acoustics ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 37-50
Author(s):  
Gergely Csány ◽  
Michael Gray ◽  
Miklós Gyöngy
Keyword(s):  
Power Output ◽  
High Intensity ◽  
Electrical Impedance ◽  
Focused Ultrasound ◽  
Low Cost ◽  
Acoustic Power ◽  
High Intensity Focused Ultrasound ◽  
Ultrasound Transducers ◽  
Impedance Measurements ◽  
Primary Advantage

A method is proposed for estimating the acoustic power output of ultrasound transducers using a two-port model with electrical impedance measurements made in three different propagation media. When evaluated for two high-intensity focused ultrasound transducers at centre frequencies between 0.50 and 3.19 MHz, the resulting power estimates exceeded acoustic estimates by 4.5–21.8%. The method was shown to be valid for drive levels producing up to 20 MPa in water and should therefore be appropriate for many HIFU (high-intensity focused ultrasound) applications, with the primary advantage of employing relatively low-cost, non-specialist materials and instrumentation.

Sign in / Sign up

Export Citation Format

Share Document