scholarly journals Keratorefractive Effect of High Intensity Focused Ultrasound Keratoplasty on Rabbit Eyes

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Zhiyu Du ◽  
Pisong Yan ◽  
Qiang Luo ◽  
Dan Zhang ◽  
Yu Zhang
Keyword(s):  
High Intensity ◽  
Focused Ultrasound ◽  
Corneal Stroma ◽  
Major Axis ◽  
High Intensity Focused Ultrasound ◽  
Focal Region ◽  
Corneal Curvature ◽  
Noninvasive Technique ◽  
The Difference ◽  
Group 2

Purpose. To evaluate high intensity focused ultrasound (HIFU) as an innovation and noninvasive technique to correct presbyopia by altering corneal curvature in the rabbit eye.Methods. Eighteen enucleated rabbit eyes were treated with a prototype HIFU keratoplasty. According to the therapy power, these eyes were divided three groups: group 1 (1 W), group 2 (2 W), and group 3 (3 W). The change in corneal power was quantified by a Sirius Scheimpflug camera. Light microscopy (LM) and transmission electron microscopy (TEM) were performed to determine the effect on the corneal stroma.Results. In the treated eyes, the corneal curvature increases from 49.42 ± 0.30 diopters (D) and 48.00 ± 1.95 D before procedure to 51.37 ± 1.11 D and 57.00 ± 1.84 D after HIFU keratoplasty application in groups 1 and 3, respectively. The major axis and minor axis of the focal region got longer when the powers of the HIFU got increased; the difference was statistically significant (p<0.05). LM and TEM showed HIFU-induced shrinkage of corneal stromal collagen with little disturbance to the underlying epithelium.Conclusions. We have preliminarily exploited HIFU to establish a new technique for correcting presbyopia. HIFU keratoplasty will be a good application prospect for treating presbyopia.

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.

High-Intensity Focused Ultrasound Ablation of Pancreatic Cancer

2019 ◽  
Vol 03 (03) ◽  
pp. 243-252
Author(s):  
Gianluca Maria Varano ◽  
Giovanni Mauri ◽  
Luca Mascagni ◽  
Paolo Della Vigna ◽  
Guido Bonomo ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
High Intensity ◽  
Focused Ultrasound ◽  
Advanced Disease ◽  
Mechanical Energy ◽  
High Intensity Focused Ultrasound ◽  
Pancreatic Tumors ◽  
Noninvasive Technique ◽  
Invasive Approach ◽  
Cancer Management

AbstractPancreatic cancer is one of the leading causes of cancer deaths, and many patients, with advanced disease, suffer from severe pain that can heavily affect their quality of life. In patients with advanced disease, an eminent role is played by percutaneous techniques, which cause tumor necrosis with a minimally invasive approach. High-intensity focused ultrasound (HIFU) is a relatively recent noninvasive technique that allows ablation of different solid tumors including uterine fibroids, and hepatic, renal, and pancreatic tumors. HIFU technology is based on external emission of an ultrasound beam, which has larger amplitudes than the regular diagnostic probes, focused on a precise target, allowing mechanical energy transfer through the tissues and tumor ablation due to thermal and nonthermal effects. Multiple clinical trials have been performed to evaluate the safety, feasibility, and efficacy of HIFU for the palliation of pancreatic tumors, alone or in combination with chemotherapy. Tumor-related pain relief was achieved in the vast majority of reported cases, and no significant side effects were recorded. This review aims to provide a description of HIFU physical principles, briefly summarize the clinical experience, to date, in HIFU treatment of pancreatic cancer, and discuss the possible future challenges, limitations, and insights in HIFU and pancreatic cancer management.

Characterization of the Harmonic Generation from Cavitating Bubbles Interacted with a Diagnostic Ultrasound in the Focal Region of High Intensity Focused Ultrasound

2006 ◽  
Vol 321-323 ◽  
pp. 1123-1128 ◽  
Author(s):  
Min Joo Choi ◽  
Gwan Suk Kang ◽  
Dong Guk Paeng ◽  
Sung Min Rhim ◽  
Moo Ho Bae ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Harmonic Generation ◽  
High Intensity ◽  
Focused Ultrasound ◽  
Harmonic Component ◽  
Diagnostic Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Focal Region ◽  
Current Harmonic

Harmonic image (HI) has been proposed to be promising for visualizing lesions produced by therapeutic high intensity focused ultrasound (HIFU). The study characterizes harmonics generated from the bubble cavitating at the focal region of a therapeutic HIFU field in response to a typical diagnostic ultrasound. Based on Gilmore model, it was simulated the nonlinear dynamics of the bubble being resonated at 1 MHz of the therapeutic ultrasound and driven by a typical 3.5 MHz diagnostic pulse. It was shown that harmonic generation increased with MI in a sigmoid pattern where the rapid and transient changes occurred between 0.5 and 2 in MI. For whole ranges of MI (less than 8), the sub-harmonic was the predominant in magnitudes over other harmonic bands. This reveals that, if HI is considered for improving the detection of focal legion highly cavitating caused by a HIFU field, the sub-harmonic component would be a preferred parameter rather than the 2nd harmonic which has been commonly used in current harmonic imaging.

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