The ultrasounds which are emitted by the vibrations of
the crystals in the ultrasound probe interact with the tissues being explored and transmit
a return-echo (echogenic response). The denser the tissue, the stronger the echogenic
response. For example, calcifications such as stones produce the strongest echo and
liquids such as a full bladder transmit the weakest.
The stronger the echogenic response, the paler the image of the transmitting structure and
the weaker the response is, the darker the image. When an anatomic structure is explored
by ultrasound the echogenic response may be:
- hyperechogenic i.e. it transmits stronger echoes than
surrounding tissue;
- isoechogenic i.e. it transmits echoes which are similar to
those of surrounding areas and cannot be differentiated from them;
- hypoecgogenic i.e. it transmits weaker echoes than
surrounding tissues.
- transonic i.e. no echo transmission. To simplify the
explanation for this absence let's say that below a hyperechogenic structure sometimes
there is no echo transmission because the structure has generated a posterior shadow cone.
SYNONYMS
hyperechogenic = sound lucent = over-reflection
Isoechogenic= same-reflection
Hypoechogenic = poor or weak reflection
Transonic= asonic = no
reflection
Shadow cone= acoustic barrage
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