Medical Ultrasound Imaging
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Searchterm 'Field of View' found in 7 articles
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Field of View
(FOV) The field of view is the plane or area depicted by the ultrasound transducer.
Convex Transducer
Convex transducers are today standard on every new scanner. A convex surface allows the scanning of a larger area with a smaller array. The method of focusing and beam sweeping of a convex or curvilinear / curved array is similar to a linear array transducer, except of the shape of the probe and the sector format of the created image.
The better fit to the body, caused by the curved shape with smaller convex contact surface, and the wider field of view further from the transducer face are advantages in abdominal ultrasound.
However, also a convex array is often too large to image the heart when probing between the ribs. Caused by combining a large field of view with smallest array size, phased array transducers are the best choice in cardiac ultrasound.

See also Curved Transducer.

Curved Transducer
A curved or curvilinear array transducer is similar to a linear array except that the image created has a sector-type format. A curvilinear array gives a large footprint and near field with a wide sector. Usually, curved transducers are described by the radius of curvature in mm. The transducer elements control the characteristics and direction of the sound beam.
Curvilinear transducers have a wider field of view from the transducer face. Sector scanners are most useful for cardiac ultrasound examinations where the beam is directed between the ribs to image the heart.
Also called convex transducer.
Equipment Preparation
Equipment Preparation is an essential step in ensuring optimal ultrasound imaging quality and maintaining a safe and hygienic scanning environment. The following considerations should be taken into account:
Ultrasound Machine Warm-Up:
The ultrasound scanner should be turned on and allowed to warm up for at least 5 minutes before initiating the examination. This allows the system to stabilize and ensures consistent performance.
Transducer Selection:
The appropriate pobe should be selected based on the type of examination required, as well as the patient's body size, weight, and habitus. Different transducer offer varying frequencies, field of view, and imaging capabilities, allowing for tailored imaging based on the specific clinical needs.
Power Settings and Techniques:
Prior to beginning the examination, it is crucial to verify and adjust the power settings and imaging techniques according to the examination protocol. This ensures that the ultrasound machine is optimized for the specific diagnostic requirements
Acoustic Couplant Application:
An adequate amount of acoustic couplant, such as warmed ultrasound gel, should be applied to the patient's skin or the transducer surface. This gel serves as a medium that promotes maximum transmission of the sound beam by eliminating air interfaces, leading to improved image quality.
Transducer Cleaning and Probe Covers:
All transducers should be cleaned and readily available for use with each patient. While endocavitary ultrasound probes are often protected by single-use disposable probe covers, it is important to maintain proper hygiene by performing a high-level disinfection of the probe between each use. Additionally, using a probe cover as an additional measure can help keep the probe clean and minimize the risk of cross-contamination.

By following these equipment preparation guidelines, healthcare professionals can ensure accurate and safe ultrasound examinations while promoting infection control measures and maintaining a hygienic environment for both patients and staff.
See also Environmental Protection, Portable Ultrasound Machine, Ultrasound Accessories and Supplies, and Ultrasound System Performance.
Transducer
A transducer is a device, usually electrical or electronic, that converts one type of energy to another. Most transducers are either sensors or actuators. A transducer (also called probe) is a main part of the ultrasound machine. The transducer sends ultrasound waves into the body and receives the echoes produced by the waves when it is placed on or over the body part being imaged.
Ultrasound transducers are made from crystals with piezoelectric properties. This material vibrates at a resonant frequency, when an alternating electric current is applied. The vibration is transmitted into the tissue in short bursts. The speed of transmission within most soft tissues is 1540 m/s, producing a transit time of 6.5 ms/cm. Because the velocity of ultrasound waves is constant, the time taken for the wave to return to the transducer can be used to determine the depth of the object causing the reflection.
The waves will be reflected when they encounter a boundary between two tissues of different density (e.g. soft tissue and bone) and return to the transducer. Conversely, the crystals emit electrical currents when sound or pressure waves hit them (piezoelectric effect). The same crystals can be used to send and receive sound waves; the probe then acts as a receiver, converting mechanical energy back into an electric signal which is used to display an image. A sound absorbing substance eliminates back reflections from the probe itself, and an acoustic lens focuses the emitted sound waves. Then, the received signal gets processed by software to an image which is displayed at a monitor.
Transducer heads may contain one or more crystal elements. In multi-element probes, each crystal has its own circuit. The advantage is that the ultrasound beam can be controlled by changing the timing in which each element gets pulsed. Especially for cardiac ultrasound it is important to steer the beam.
Usually, several different transducer types are available to select the appropriate one for optimal imaging. Probes are formed in many shapes and sizes. The shape of the probe determines its field of view.
Transducers are described in megahertz (MHz) indicating their sound wave frequency. The frequency of emitted sound waves determines how deep the sound beam penetrates and the resolution of the image. Most transducers are only able to emit one frequency because the piezoelectric ceramic or crystals within it have a certain inherent frequency, but multi-frequency probes are also available.
See also Blanking Distance, Damping, Maximum Response Axis, Omnidirectional, and Huygens Principle.
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