Canis ISSN: 2398-2942

Ultrasound: machine settings

Contributor(s): Alison Dickie

Introduction

  • Ultrasound is high frequency sound (1.5-15+ MHz used for veterinary ultrasonography).
  • Pulse echo principle is used whereby a pulse of sound is emitted and an echo is returned after interacting with tissue.
  • The expected course of the ultrasound beam can be measured and plotted by assuming a constant velocity of sound.
  • There are many artefacts in ultrasonography and it is important to evaluate every organ in at least two planes to ensure any lesion is genuine.
  • A systematic approach is helpful in ensuring no part of an organ is missed.
  • For abdominal ultrasound the entire abdomen should be examined (rather than just a single organ) as this helps in identifying lesions that may not be expected. It also allows practice in recognizing the normal appearance of the various organs.
Orientation
  • On all transducers there is a mark or button, which shows the orientation of the sound beam. It is helpful to hold the transducer with thumb or forefinger on the mark to aid orientation.
  • On the monitor there is usually a mark on one edge of the image which corresponds with the side with the mark on the transducer.
  • As long as a consistent orientation is used it doesn't matter which way the image on the screen is displayed but it helps with interpreting images if the same orientation is used for every examination.
  • Generally for dorsal and sagittal images the cranial aspect should be displayed on the left of the monitor screen.
  • With echocardiography by convention the base of the heart is displayed to the right of the screen.
  • For transverse images the right side of the animal should be displayed on the left of the screen (as in radiology).
Terminology
  • Anechoic- no echoes so appears black.
  • Hypoechoic- few echoes returned so appears dark gray.
  • Hyperechoic- large numbers of echoes returned so appears bright.
  • Echotexture- described as fine or coarse and by degree of uniformity, eg homogenous, complex, heterogeneous.
  • Order of increasing echogenicity of body tissues (taken from Veterinary Diagnostic Ultrasoundby Nyland and Mattoon):
    • Bile, urine.
    • Renal medulla.
    • Muscle.
    • Renal cortex.
    • Liver.
    • Storage fat.
    • Spleen.
    • Prostate.
    • Renal sinus.
    • Structural fat, vessel walls.
    • Bone, gas, organ boundaries.

Equipment

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Preparation

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Type of scan

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Further Reading

Publications

Refereed papers

Other sources of information

  • Nyland T G & Mattoon J S (1995) Veterinary Diagnostic Ultrasound. W B Saunders. ISBN 0721627455.


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