Miniaturized Focused Ultrasound Transducers for Intravascular Therapies

2017 ◽  
Author(s):  
Jinwook Kim ◽  
Huaiyu Wu ◽  
Xiaoning Jiang
Keyword(s):  
Focused Ultrasound ◽  
Radius Of Curvature ◽  
Ultrasound Transducers ◽  
Element Analysis ◽  
Aperture Diameter ◽  
Beam Focusing ◽  
Concave Lens ◽  
Ultrasound Energy ◽  
Forward Looking

Intravascular ultrasound approach has shown its advantages for thrombectomy. Catheter-directed ultrasound techniques have realized safe therapies by suppressing mechanical contact and penetration of excessive ultrasound energy through the tissue. One limitation of this approach is the lack of the sufficient ultrasound energy for fast thrombectomy because typical catheter-mounted transducers have high-frequency and low acoustic power. In this work, we aim to resolve this problem by designing miniaturized focused ultrasound transducers for improved therapeutic efficacy, which can generate low-frequency, sufficient pressure output within the confined insonation beam. This study builds upon our previous initial design of sub-megahertz, forward-looking, focused ultrasound transducers for preliminary in vitro study on microbubble-mediated thrombolysis. 650 kHz, forward-looking, concave-aperture ultrasound transducers were designed and mounted on 5–6 F catheters. The effect of design factors including aperture diameter, radius-of-curvature, and concave lens acoustic impedance on focusing performance were analyzed by using finite element analysis. Although the theoretical prerequisites for ideal beam focusing were not fulfilled due to the spatial limitation, the simulation results showed that practical design of the concave lens with the small geometrical aperture still enables to generate confined beam with a reasonable focal gain. Experimental validation results confirmed that the focal gain of 9 dB can be achievable. The measured transmitting sensitivity of the concave aperture transducer is 22.5 kPa/Vpp.

scholarly journals Preclinical study to improve microbubble-mediated drug delivery in cancer using an ultrasonic probe with an interchangeable acoustic lens

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seunghyun Lee ◽  
Hoyoon Jeon ◽  
Shinyong Shim ◽  
Maesoon Im ◽  
Jinsik Kim ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Focused Ultrasound ◽  
Pressure Field ◽  
Ultrasound Irradiation ◽  
Radius Of Curvature ◽  
Control Group ◽  
Ultrasonic Probe ◽  
Acoustic Lens ◽  
Concave Lens

AbstractFocused ultrasound with microbubbles (FUS-MBs) has shown that it can lead to an efficient drug delivery system (DDS) involving the oscillation and destruction of the MB but is limited in drug delivery due to its narrow pressure field. However, unfocused ultrasound with MBs (UUS-MBs) and an interchangeable acoustic lens can tune and enhance the pressure field for MB destruction to overcome the disadvantages of FUS-MB DDSs. We designed a lens suitable for an ultrasound-phased array probe and studied the optimal treatment conditions for MB destruction in vitro through an optical imaging setup. The DDS effects were evaluated in a rat hepatoma model using doxorubicin (DOX) treatment. A concave lens with a radius of curvature of 2.6 mm and a thickness of 4 mm was selected and fabricated. UUS-MBs with the acoustic lens at 60 Vpp for 32 cycles and a PRF of 1 kHz could induce MB destruction, promoting the DDS even under fluidic conditions. In the animal experiment, the UUS-MBs in the acoustic lens treatment group had a higher concentration of DOX in the tumor than the control group. Our system suggests uses an acoustic lens to increase DDS effectiveness by providing sufficient ultrasound irradiation to the MBs.

scholarly journals EAP-FUS022 (Yoo): FUS Mediated Reversible Modulation of Region Specific Brain Function

2017 ◽  
Author(s):  
Seung-Schik Yoo ◽  
Jong-Hwan Lee ◽  
Yongzhi Zhang ◽  
Wonhye Lee ◽  
Krisztina Fischer ◽  
...  
Keyword(s):  
Brain Function ◽  
Focused Ultrasound ◽  
Brain Area ◽  
Brain Regions ◽  
Neural Cells ◽  
Low Intensity ◽  
Functional Modulation ◽  
Ultrasound Energy ◽  
Sonication Parameters

The goal of the proposed research is to investigate the feasibility of using low-intensity and lowfrequency focused ultrasound energy to reversibly modulate the activity of a region-specific brain area. We will modulate the cortical activity from an animal brain using FUS sonication, as monitored by real-time functional MRI. Prior to the animal experiment, in-vitro phantoms containing neural cells will be constructed and sonicated to estimate the range of suitable sonication parameters. This work is expected to provide an unprecedented opportunity for the transient functional modulation of targeted brain regions, creating a new line of applications, such as FUS-mediated functional mapping.

A Beam Corrected Estimation of the Frequency Dependent Attenuation of Biological Tissues from Backscattered Ultrasound

1983 ◽  
Vol 5 (2) ◽  
pp. 136-147 ◽  
Author(s):  
M.J.T.M. Cloostermans ◽  
J.M. Thijssen
Keyword(s):  
Attenuation Coefficient ◽  
Focused Ultrasound ◽  
Accurate Method ◽  
Biological Tissues ◽  
Acoustic Attenuation ◽  
Simple Method ◽  
Frequency Dependent ◽  
Ultrasound Energy

A practical and highly accurate method of estimation of the frequency-dependent slope of the acoustic attenuation coefficient, α1, using backscattered ultrasound energy is presented. The influence or the focused ultrasound beam is experimentally measured and a simple method for incorporating the field effects in the estimate of α1 is described. The accuracy of the estimate of α1in vitro which appears to be of the order of 10 percent, demonstrates the feasibility of in vivo applications of the technique.

Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating

1990 ◽  
Vol 48 (1) ◽  
pp. 198-199
Author(s):  
Ryo Iiyoshi ◽  
Susumu Maruse ◽  
Hideo Takematsu
Keyword(s):  
Electron Beam ◽  
Tungsten Wire ◽  
Local Heating ◽  
Electron Gun ◽  
Original Position ◽  
Beam Power ◽  
Radius Of Curvature ◽  
High Brightness ◽  
Beam Focusing ◽  
Time Operation

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.

scholarly journals A novel method for estimating the focal size of two confocal high-intensity focused ultrasound transducers

2005 ◽  
Vol 117 (6) ◽  
pp. 3740-3749 ◽  
Author(s):  
Wen-Shiang Chen ◽  
Ping-Mo Ma ◽  
Hao-Li Liu ◽  
Chih-Kuang Yeh ◽  
Min-Shin Chen ◽  
...  
Keyword(s):  
High Intensity ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Ultrasound Transducers ◽  
Novel Method

scholarly journals Focused ultrasound radiosensitizes human cancer cells by enhancement of DNA damage

2021 ◽  
Author(s):  
Xinrui Zhang ◽  
Mariana Bobeica ◽  
Michael Unger ◽  
Anastasia Bednarz ◽  
Bjoern Gerold ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Metabolic Activity ◽  
Focused Ultrasound ◽  
Double Strand Breaks ◽  
High Intensity Focused Ultrasound ◽  
Dna Double Strand Breaks ◽  
Strand Breaks

Abstract Purpose High-intensity focused ultrasound (HIFU/FUS) has expanded as a noninvasive quantifiable option for hyperthermia (HT). HT in a temperature range of 40–47 °C (thermal dose CEM43 ≥ 25) could work as a sensitizer to radiation therapy (RT). Here, we attempted to understand the tumor radiosensitization effect at the cellular level after a combination treatment of FUS+RT. Methods An in vitro FUS system was developed to induce HT at frequencies of 1.147 and 1.467 MHz. Human head and neck cancer (FaDU), glioblastoma (T98G), and prostate cancer (PC-3) cells were exposed to FUS in ultrasound-penetrable 96-well plates followed by single-dose X‑ray irradiation (10 Gy). Radiosensitizing effects of FUS were investigated by cell metabolic activity (WST‑1 assay), apoptosis (annexin V assay, sub-G1 assay), cell cycle phases (propidium iodide staining), and DNA double-strand breaks (γH2A.X assay). Results The FUS intensities of 213 (1.147 MHz) and 225 W/cm2 (1.467 MHz) induced HT for 30 min at mean temperatures of 45.20 ± 2.29 °C (CEM43 = 436 ± 88) and 45.59 ± 1.65 °C (CEM43 = 447 ± 79), respectively. FUS improves the effect of RT significantly by reducing metabolic activity in T98G cells 48 h (RT: 96.47 ± 8.29%; FUS+RT: 79.38 ± 14.93%; p = 0.012) and in PC-3 cells 72 h (54.20 ± 10.85%; 41.01 ± 11.17%; p = 0.016) after therapy, but not in FaDu cells. Mechanistically, FUS+RT leads to increased apoptosis and enhancement of DNA double-strand breaks compared to RT alone in T98G and PC-3 cells. Conclusion Our in vitro findings demonstrate that FUS has good potential to sensitize glioblastoma and prostate cancer cells to RT by mainly enhancing DNA damage.

ANALYSIS OF AN INTERNAL FIXATION OF A LONG BONE FRACTURE

2005 ◽  
Vol 05 (01) ◽  
pp. 89-103 ◽  
Author(s):  
K. RAMAKRISHNA ◽  
I. SRIDHAR ◽  
S. SIVASHANKER ◽  
V. K. GANESH ◽  
D. N. GHISTA
Keyword(s):  
Stress Shielding ◽  
Axial Loading ◽  
Bending Moment ◽  
Fracture Site ◽  
Long Bone ◽  
Radius Of Curvature ◽  
Element Analysis ◽  
Long Bone Fracture ◽  
Fracture Interface ◽  
Tensile Surface

A major concern when a fractured bone is fastened by stiff-plates to the bone on its tensile surface is excessive stress shielding of the bone. The compressive stress shielding at the fracture-interface immediately after fracture-fixation delays bone healing. Likewise, the tensile stress shielding of the healed bone underneath the plate also does not enable it to recover its tensile strength. Initially, the effect of a uniaxial load and a bending moment on the assembly of bone and plate is investigated analytically. The calculations showed that the screws near the fracture site transfers more load than the screws away from the fracture site in axial loading and it is found that less force is required when the screw is placed near to fracture site than the screw placed away from the fracture site to make the bone and plate bend with same radius of curvature when subjected to bending moment. Finally, the viability of using a stiffness graded bone-plate as a fixator is studied using finite element analysis (FEA): the stiffness-graded plate cause less stress-shielding than stainless steel plate.

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