Hyperechoic
structures or tissues that reflect much of the ultrasound energy back to the transducer and appear brightly on the image
Hypoechoic
structures or tissues that reflect little of the ultrasound energy back to the transducer and appear darker on the image
Anechoic
no reflection of energy -- appear darkest black
tissues in order of echogenicity
cortical bone, tendon/ligament, nerve, muscle, subcortical bone.
Noting normal expected views of tissues can allow for recognition of abnormalities, like a hypoechoic area of fluid around a tissue, or separation, disruption or retraction of a tissue that has ruptured.
advantages of ultrasound > MRI
higher resolution, portable, lower cost, no known hazards, ability to palpate while imaging at time of exam.
disadvantages of ultrasound
operator dependent, limited ability to show joint surfaces/intraarticular structures, can show cortical outline of bone but not beneath, does not cross air-tissue interfaces and obese patients are not imaged well with ultrasound.
Canadian C-Spine Rule and the NEXUS
evidence-based guidelines that help clinicians decide whether radiographic examination is necessary based on specific clinical criteria