Ultrasound Transducers PDF

Common type of Transducers Convex Phased Linear array array array Linear Array A more complete name for what is commonly called a linear array is linear sequenced array. Voltage pulses applied to element groups sequentially, with each group acting l...

Common type of Transducers Convex Phased Linear array array array Linear Array A more complete name for what is commonly called a linear array is linear sequenced array. Voltage pulses applied to element groups sequentially, with each group acting like a larger transducer for focused beams and high resolution. Linear ultrasound transducers typically use frequencies between 7 and 15 MHz for detailed imaging of superficial structures. Linear Array The linear image consists of parallel scan lines produced by pulses originating at different points across the surface of the array but that all travel in the same vertical direction (parallel). A drawback is the lack of ability to steer or shape the beam. A linear array produces rectangular images composed of many parallel, vertical scan lines. A voltage pulse is applied simultaneously to all elements in a small group: first to elements 1 to 4 (for example) as a group (A), then to elements 2 to 5 (B), and so on across the transducer assembly (C-E). The process is then repeated (F). G, An image generated from a linear array. H, A linear array transducer. Convex Array A convex array, also called a curved array, is constructed as a curved line of elements rather than a straight one. The complete name for this transducer is convex sequenced array. The convex array operates similarly to the linear array but produces a sector image. Curved ultrasound transducers typically use frequencies between 3.5-5 MHz for deep structures. A, Convex arrays send pulses out in different directions from different points across the curved array surface. B, A sector-type image with a curved top is produced by a convex array. C, A convex array transducer.  Why is it that low- frequency ultrasound waves are not typically emitted in a linear shape? Phased Array The phased array is operated by applying voltage pulses to most or all elements (not a small group) in the assembly, but with small (less than 1 μs) time differences (called phasing), steering the sound beam in desired directions. By adjusting the timing delays between pulses, the beam can be made to sweep across an area, creating a sector-shaped image without mechanical movement. Phased Array This electronic scanning allows for quick, consistent imaging, producing sector images similar to those obtained by manually rotating a single-element transducer. Often referred to as electronic sector transducers due to their ability to electronically scan and produce sector images. Phased ultrasound transducers typically use frequencies between 3.5-5 MHz for intercostal spaces (echocardiography) The key differences between linear and curved array ultrasound transducers Feature Linear Array Curved Array o Element Shape Beam Shape Straight line Parallel lines Curved line Divergent lines Sector/wedge- Field of View Rectangular shaped Frequency Range Higher (7-15 MHz) Lower (3.5 -5 MHz) Imaging Depth Superficial Deeper tissues Abdominal, Applications Small parts, vascular OB/GYN