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Ultrasound Physics
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
For a given clinical examination, it is important to make the correct choice of ultrasound transducer. Each hand-held transducer contains an arrangement of piezoelectric elements that collectively vibrates to transmit controlled pulses of ultrasound into the body. Each type of probe has been optimised for a specific imaging application, with the size and arrangement of elements, and range of ultrasound frequencies that can be emitted and received by the transducer, carefully selected to provide an appropriate field of view and suitable image quality.
Importation and Visualization of Ultrasound Data
Published in Johan Helmenkamp, Robert Bujila, Gavin Poludniowski, Diagnostic Radiology Physics with MATLAB®, 2020
Tobias Erlöv, Magnus Cinthio, Tomas Jansson
The raw ultrasound data, called Radio Frequency (RF) data, is an oscillating signal describing the sound pressure measured at the transducer face at a time corresponding to the depth where the echo is produced in the image. A linear array ultrasound transducer typically consists of 256 piezo-electric elements placed in a row. A traditional ultrasound image is created line by line, where each line results from a beam-formed combination of pulses from an appropriate aperture (certain number of active piezoelectric elements). Hence, one raw ultrasound image could typically consist of up to 256 columns, where each column describes how the sound pressure varies with time (= depth) in the corresponding tissue segment. The B-Mode (Brightness Mode) image that normally is displayed during medical ultrasound examinations is the amplitude of the sound pressure where brighter pixels correspond to stronger echoes. In other words, the B-Mode image is the amplitude (envelope) of the RF data, usually with some additional post processing. Figure 20.1 shows a partial line of RF data and the corresponding envelope. The B-Mode images can normally be exported as standardized DICOM images. The RF data, which contains more information and is commonly used in research environments, is usually not exportable from clinical scanners and never in DICOM format.
Ultrasound in Assisted Reproductive Technology: Anatomy and Core Examination Skills
Published in Arianna D'Angelo, Nazar N. Amso, Ultrasound in Assisted Reproduction and Early Pregnancy, 2020
Prescan preparations include giving an information leaflet on TVS before or on arrival for the scan appointment. This would give the patient an opportunity to consider having TVS or TAS or clarify elements of the examination. The patient should also empty her bladder before coming to the scan room. TVS should always be undertaken in the presence of a female chaperone, and this must be documented in the notes. The date of the last menstrual period should be documented, and the ultrasound transducer cleaned and disinfected as described in Chapter 19. The sonographer should wear gloves on both hands. The sonographer should also exclude latex allergy to avoid its serious consequences. Latex-free probe covers and gloves should be available in the clinic. Sachets of sterile gel should be used for the outside of the cover. Aprons or personal protective devices might be used for infection control.
Evaluation of the dual-frequency transducer for controlling thermal ablation morphology using frequency shift keying signal
Published in International Journal of Hyperthermia, 2022
Wenchang Huang, Chuanlong Ning, Rui Zhang, Jie Xu, Beiyi Chen, Zhangjian Li, Yaoyao Cui, Weiwei Shao
The frequency characteristics of the ultrasound transducer were measured before the experiment of thermal ablation, as the selection of an appropriate operating frequency is critical. The impedance analyzer (E4991A, Agilent Technologies-IES, Inc., USA) was used to measure the impedance curves of the transducer. The acoustic field distribution properties of the transducer were tested in an automatic three-dimensional (3D) sound field measurement system (UMS3, Precision Acoustics Ltd, Dorset, UK) as shown in Figure 4. In the experiments, deionized and degasified water was used. The transducer was driven by a sinusoidal pulse signal with 10 cycles, 500 Hz PRF. The output sound pressure was calculated by converting the original voltage output received by needle hydrophones (NH0500, Precision Acoustics, Ltd, UK). The hydrophone was perpendicular to the surface of the transducer on the precision positioning platform (TS303, BOCIC, Ltd., China). Electrical power was measured by a power meter (RS-70, Nissei Co., Ltd., China). Sound power was measured by a radiative force balance (RFB, Precision Acoustics Ltd., USA).
Experimental validation of acoustic and thermal modeling in heterogeneous phantoms using the hybrid angular spectrum method
Published in International Journal of Hyperthermia, 2021
Megan Hansen, Douglas Christensen, Allison Payne
A scanning hydrophone (HNR-0500, Onda Corporation, Sunnyvale, CA) was used to directly measure the 2D pressure patterns of the ultrasound beam after propagation through the P-type phantoms. Both the homogeneous and heterogeneous P-Type phantoms were placed in the pre-focal zone of a focused ultrasound transducer mounted vertically in a degassed water-filled testing column, as seen in Figure 1(a). Phantoms were supported by a platform designed to avoid interference with the propagating beam and to secure the phantom’s position, ensuring positional consistency across each testing configuration. The focused ultrasound transducer was a 256-element phased array (Imasonic, Voray-sur-l’Ognon, France; frequency: 940 kHz; focal length: 10 cm; aperture: 14.4 × 9.8 cm; full-width-half-maximum intensity pressure pattern: 1.8 × 2.5 × 10.9 mm in water; acoustic power: 2.3 W) [30]. The deionized water in the testing column was degassed prior to testing (<2 ppm) to prevent beam scattering and hydrophone damage. A 2D scan with 0.25-mm isotropic resolution over a 1.0 × 1.0-cm area was centered around the focal point of the beam. The measured 2D complex pressure pattern was then propagated into a 3D volume matching the relevant portion of the simulated model size using the angular spectrum approach [22] for comparison with HAS- and k-Wave-simulated patterns.
Pulsed radiofrequency ablation of genicular nerve versus intra-articular radiofrequency ablation combined with platelets rich plasma for chronic kneeosteoarthritis
Published in Egyptian Journal of Anaesthesia, 2021
Sameh El-Tamboly, Mohammed Medhat, Ragab Khattab, Hamed Darwish, Akram deghady
All procedures was carried out under local anesthesia, in operation room. The skin was palpated to localize the anterior patellar region with the knee angled at 30–45 degrees. The patella was visualized using a 5–10 MHz linear probe in a trans-axial anatomical plane. The transducer was moved proximally until the patella was no longer visualized. After the best ultrasound image was gained in this location, the skin was marked on the probe position. Using strict aseptic procedure (skin sterilization, ultrasound transducer covering, and sterile ultrasound gel). Local anesthesia was obtained with lidocaine using a 25-gauge 10 cm needle under live ultrasound guidance from a lateral to medial transverse approach [12]. Then, moved along the same needle track, 10 cm a 22-gauge Quincke needle was inserted into the knee joint under real-time ultrasound imaging. 2 mL 1% lidocaine were injected inside the joint while observing the suprapatellar pouch filling in real time. RF introducer cannula 10 cm 22-gauge with a stylet that was placed intra-articularly in two planes through a predefined area. After a successful placement, the stylet in the introducer was pulled out and RF probe was inserted via the introducer needle. Subsequently, PRF was activated for 15 minutes with 42°C degree and a pulse span of 20 milliseconds, at 2 Hz. Then 20 ml PRP were injected intra-articular using another entry site using ultrasound guide. The patients’ evaluation were done in a prospective manner from patient baseline value, at the end of the treatment, follow-ups 3, 6 and 12 months later.