An introduction to ultrasound transducers
To make use of the full potential of the ultrasound system at a hospital, having the right accessories is incredibly important. Correct ultrasound transducer types are vital to the performance of the ultrasound system. Also known as a probe, ultrasound transducer is basically a device that produces sound waves that bounce off body tissues and make echoes. The transducer receives the echoes and sends them to a computer, which uses them in order to create an image called sonogram. Ultrasound transducer by many popular brands is available in the market today. PHILIPS 1356A , for example, is a popular fetal ultrasound transducer,
An ultrasound transducer converts electrical energy into mechanical energy and back again, on the basis of the piezoelectric effect. The hand-held part of the ultrasound machine is responsible for the production and detection of ultrasound waves. It comprises of:
Crystal/ceramic element with piezoelectric properties: It usually features lead zirconate titanate (PZT), and may include a single element or be a broadband transducer with multiple elements. The thickness of the element is determined the desired resonance frequency. While a thinner element produces high frequency oscillation, a thicker element produces a lower frequency oscillation.
Positive and ground electrodes on the faces of the element: This supports the electrical connection. The positive electrode is in the back of the element, while ground electrode is on the front of the element.
Damping (backing) block: The ultrasound transducer adheres to the back of the crystal (behind the positive electrode), and absorbs ultrasound energy directed backward. It attenuates stray ultrasound signals from the housing, while dampening the resonate vibrations in the element that creates a shorter spatial pulse length. This allows for better axial resolution but higher bandwidth.
Matching layer: The interface between the transducer element and the tissue allows for around 100% transmission of the ultrasound from the element into the tissues by reducing the reflection owing to traversing different mediums. Layers of materials with acoustic impedances that are between the transducer material and soft tissue help in achieving this goal. Each of the layers can is one-quarter wavelength thick.
Housing: It includesPlastic Housing , acoustic insulator, and metal shield, and ensures the electrical insulation and protection of the element.
Transducers can produce an ultrasound beam in two ways, linear array or phased array. In case the shape at the top of the images matches the shape at the bottom of the image, then it would be a linear array. If the shapes are different, then it is a phased array. Details of ultrasound transducers and other biomedical supplies like GE Masimo LNC SPO2 can be found online.