ULTRASOUND: ULTRASOUND TRANSDUCERS

         A transducer converts one type of energy into another. Based upon the pulse-echo principle occurring with ultrasound piezoelectric crystals, ultrasound transducers convert:
          – Electricity into sound = pulse
          – Sound into electricity = echo

• Pulse of sound is sent to soft tissues
• Pulsing is determined by the transducer or probe crystal(s) and is not operator controlled.

• Echo produced by soft tissues
• Tissue interaction with sound =acoustic propagation properties
• Echoes are received by the transducer crystals
• Echoes are interpreted and processed by the ultrasound machine

Transducer Types
• Mechanical

• Electronic
– Linear Arrays
– Curved Arrays

– Phased Arrays

Linear - the linear array scanners produce sound waves parallel to each other and produces a rectangular image. The width of the image and number of scan lines are the same at all tissue levels. This has the advantage of good near field resolution. Often used with high frequencies ie 7MHz. Can be used for viewing surface texture of the liver. There disadvantage is artifacts when applied to a curved part of the body creating air gaps between skin and transducer.

12L LINEAR PROBE
Taken by, Ms.Praseetha

12L LINEAR PROBE
Photo Taken by, Ms.Praseetha

Sector/Vector - Produces a fan like image that is narrow near the transducer and increase in width with deeper penetration. It is useful when scanning between the ribs as it fits in the intercostal space. The disadvantage is poor near field resolution.

3S sector probe

Curved - Often with frequencies of 2 - 5 MHz (to allow for a range of patients from obese to slender). It is a compromise of the Linear and Sector scanners. The density of the scan lines decreases with increasing distance from the transducer. Can be difficult to use in curved regions of the body eg. the spleen behind the left costal margin.

taken by,
C60e/5-2MHz Ms.Praseetha

3D Transducers

Matrix Transducer

3 to 1 MHz extended operating frequency range
2D Matrix phased array with 2,400 elements
2D, biplane (Live xPlane), triggered full volume, Live 3D Echo, Color Doppler with 2D, biplane and 3D,Harmonic Imaging

Mechanical 3D Tranducer