Temperature Dependent Tissue Properties and Ultrasonic Lesion Formation

1999 ◽  
Author(s):  
Michael C. Kolios ◽  
Michael D. Sherar ◽  
John W. Hunt
Keyword(s):  
Theoretical Model ◽  
High Intensity ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Bioheat Transfer ◽  
Tissue Temperature ◽  
Focal Region ◽  
Temperature Dependent ◽  
Size And Shape ◽  
Temperature Distributions

Abstract High intensity focused ultrasound has considerable potential for the noninvasive treatment of localised disease. A detailed understanding of the kinetics of tissue coagulation is required to optimise ultrasonic parameters. In this presentation a theoretical model was used to examine the effects of temperature dependent ultrasonic attenuation and absorption on the transient tissue temperature distributions and lesion dimensions. A finite difference algorithm was used to solve numerically the nonlinear form of the bioheat transfer equation in cylindrical coordinates. The lesion dimensions were calculated based on the time-temperature distributions in tissue by using a thermal dose threshold to define the lesion boundaries. The results were compared to published experimental data in which the the location of maximal energy deposition during short duration high intensity focused ultrasound irradiation of in vitro tissue was examined. It was found that the theoretical model did not predict the size and shape of the experimental lesions. To correctly predict lesion size and shape much higher values of attenuation and absorption were required than can be accounted for by thermal coagulation of the tissue alone. The values used suggest that for intensities greater than 3030 W/cm2 the effective local attenuation/absorption in the focal region increased by a factor of 10–20. It is finally shown that temperature dependent tissue changes should be incorporated in thermal models to avoid underestimation of the induced temperature distributions during high intensity focused ultrasound therapy.

scholarly journals Segmentation Method for Magnetic Resonance-Guided High-Intensity Focused Ultrasound Therapy Planning

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
A. Vargas-Olivares ◽  
O. Navarro-Hinojosa ◽  
M. Maqueo-Vicencio ◽  
L. Curiel ◽  
M. Alencastre-Miranda ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
High Intensity ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Segmentation Algorithm ◽  
Focal Region ◽  
Therapy Planning ◽  
Mr Images ◽  
Monitoring Method ◽  
Data Set

High-intensity focused ultrasound (HIFU) is a minimally invasive therapy modality in which ultrasound beams are concentrated at a focal region, producing a rise of temperature and selective ablation within the focal volume and leaving surrounding tissues intact. HIFU has been proposed for the safe ablation of both malignant and benign tissues and as an agent for drug delivery. Magnetic resonance imaging (MRI) has been proposed as guidance and monitoring method for the therapy. The identification of regions of interest is a crucial procedure in HIFU therapy planning. This procedure is performed in the MR images. The purpose of the present research work is to implement a time-efficient and functional segmentation scheme, based on the watershed segmentation algorithm, for the MR images used for the HIFU therapy planning. The achievement of a segmentation process with functional results is feasible, but preliminary image processing steps are required in order to define the markers for the segmentation algorithm. Moreover, the segmentation scheme is applied in parallel to an MR image data set through the use of a thread pool, achieving a near real-time execution and making a contribution to solve the time-consuming problem of the HIFU therapy planning.

Nonlinear Derating of High-Intensity Therapeutic Ultrasound Beams Using Gaussian Modal Sums

2013 ◽  
Author(s):  
Seyed Ahmad Reza Dibaji ◽  
Matthew R. Myers ◽  
Joshua E. Soneson ◽  
Rupak K. Banerjee
Keyword(s):  
High Intensity ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Nonlinear Propagation ◽  
Tissue Temperature ◽  
Medical Procedure ◽  
Pressure Amplitude ◽  
Pressure Trace ◽  
The Difference ◽  
Semi Empirical

High intensity focused ultrasound (HIFU) is a noninvasive medical procedure during which a large amount of energy is deposited in a short duration which causes sudden localized rise in tissue temperature, and ultimately, cell necrosis. In assessing the influence of HIFU on biological tissue, semi-empirical mathematical models can be useful for predicting thermal effects. These models require values of the pressure amplitude in the tissue of interest, which can be difficult to obtain experimentally. One common method for estimating the pressure amplitude in tissue is to operate the HIFU transducer in water, measure the pressure amplitude, then multiply by a scaling factor that accounts for the difference in attenuation between water and tissue. This procedure can be accurate when the ultrasound amplitude is low, and the pressure trace in tissue is proportional to that in water. Because of this proportionality, the procedure for reducing the amplitude from water to tissue is called linear derating. At higher intensities, however, harmonics of the fundamental frequency are generated due to nonlinear propagation effects. Higher harmonics are attenuated differently in water and tissue (Hamilton and Blackstock [1]), and the pressure waves in water and tissue are no longer proportional to one another. Techniques for nonlinearly transforming pressure amplitudes measured in water to values appropriate for tissue are therefore desirable when bioeffects of higher intensity procedures are being studied. These techniques are labeled “nonlinear derating”.

High-Intensity Focused Ultrasound Scattering at Mammal Vertebrae

2020 ◽  
Author(s):  
David Sanford ◽  
Christoph Schaal
Keyword(s):  
High Intensity ◽  
Laboratory Experiments ◽  
Energy Deposition ◽  
Focused Ultrasound ◽  
Complex Geometry ◽  
Ex Vivo ◽  
Pulsed Laser ◽  
High Intensity Focused Ultrasound ◽  
Focal Region ◽  
Homogeneous Media

Abstract High-intensity focused ultrasound (HIFU) is used clinically to heat cells therapeutically or to destroy them through heat or cavitation. In homogeneous media, the highest wave amplitudes occur at a predictable focal region. However, HIFU is generally not used in the proximity of bones due to wave absorption and scattering. Ultrasound is passed through the skull in some clinical trials, but the complex geometry of the spine poses a greater targeting challenge and currently prohibits therapeutic ultrasound treatments near the vertebral column. This paper presents a comprehensive experimental study involving shadowgraphy and hydrophone measurements to determine the spatial distribution of pressure amplitudes from induced HIFU waves near vertebrae. First, a bone-like composite plate that is partially obstructing the induced waves is shown to break the conical HIFU form into two regions. Wave images are captured using pulsed laser shadowgraphy, and hydrophone measurements over the same region are compared to the shadowgraphy intensity plots to validate the procedure. Next, shadowgraphy is performed for an individual, clean, ex-vivo feline vertebra. The results indicate that shadowgraphy can be used to determine energy deposition patterns and to determine heating at a specific location. The latter is confirmed through additional temperature measurements. Overall, these laboratory experiments may help determine the efficacy of warming specific nerve cells within mammal vertebrae without causing damage to adjacent tissue.

Intensity Based Simulation of the Temperature Prediction in the Focal Region of Liver Using MRI-Guided High Intensity Focused Ultrasound (HIFU)

2016 ◽  
Vol 13 (10) ◽  
pp. 6728-6732
Author(s):  
P Revathy ◽  
V Sadasivam ◽  
T. Ajith Bosco Raj
Keyword(s):  
Focused Ultrasound ◽  
Treatment Time ◽  
Prediction Method ◽  
Treatment Temperature ◽  
High Intensity Focused Ultrasound ◽  
Bioheat Transfer ◽  
Transfer Model ◽  
Focal Region ◽  
Temperature Elevation ◽  
Temperature Prediction

In this research paper a new temperature prediction method is proposed to predict the temperature in liver during thermal ablation which also takes in to account the blood flow cooling. The proposed method suggest a modification of Pennes bioheat transfer equation (PBHTE) inorder to more accurately predict the treatment temperature. The temperature elevation by the proposed heat transfer model is compared with the PBHTE model and the other two heat continuum models by Wulff and Klinger. Appropriate temperature prediction is useful in treatment planning. This may reduce the recurrence level of cancer. Further the reduction in treatment time increases patient safety.

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