Trapezoidal scanning (with steered color box)
The ability to understand the inherent advantages and disadvantages of using different transducers for specific modalities is critical to performing effective clinical diagnostic ultrasound studies. Because it is essential to use the right tools for each imaging situation, I devote a complete chapter to the subject of transducers in the 5th edition of Ultrasound Physic and Instrumentation.
The purpose behind designing a linear transducer that combines the mechanics of both a phased-sector transducer and an unsteered linear transducer is to extend the lateral field of view. Specific imaging situations, like carotid scanning, benefit from this advantage.
The animation sequence within this video helps you visualize that the trade-off to an extended field is that the beams interrogate at different angles on the left and right “wings”. It is important to maintain an awareness of the changing incident angles on those left and right sides of the image field.
How these wings are generated matters since many artifacts are angle-dependent. Additionally, the ability to assess flow direction in color Doppler is contingent on your talent in recognizing the angle between the beam and the flow.
This subject matter is discussed more thoroughly in Chapter 5: Transducers, of Frank Miele’s Ultrasound Physics and Instrumentation (5th edition). Trapezoidal Scanning is discussed specifically on page 131.
