Artifacts

ULTRASOUND

• any record or image obtained in the course of

applying a medical diagnostic technique which is

not representative of the structures under study but

is adventitious”.

• When evaluating anatomic structures, acoustic

artifacts result in added (not real), missing,

improperly located, brightness, shape or size

alterations

Ultrasound

• US waves wavelength and frequency are inversely related

• Low frequency - Better penetration of tissues – good resolution of deeper structures

• High frequency probes used for superficial structures visualization

• Higher frequency waves are more attenuated than lower frequency for a given distance

• 1-20Mhz probes• Atlas of Ultrasound-Guided Procedures in Interventional Pain Manag ement

• Increasing the transducer frequency improves the

spatial resolution at the expense of beam

penetration as a result of sound wave absorption. In

contrast, lower frequency transducers enable

assessment of deeper structures, but the spatial

resolution is lower.

• Angle of insonation

• maximum reflection achieved when the sound wave

is directed perpendicular to the imaged structure

• In addition to reflection, the sound waves also be

absorbed in the examined tissues, and the amount

of absorption increases with greater transducer

frequency and tissue viscosity.

• Acoustic Shadowing: Acoustic shadowing is the

reduction in amplitude of reflected sound caused by

reflectors that lie behind a strongly reflecting or

attenuating structure

Acoustic Reflection and Refraction

Acoustic Enhancement: Acoustic enhancement is a relative

increased echo amplitude caused by an intervening structure

of low attenuation

Ring-down and comet-tail artifacts

Reverbation

• Regional Anesthesia and Pain Medicine Vol. 32 No.

5 September–October 2007

• Ultrasound, Vol. 36, No. 4, 1995, pp 297-306.

• Seminars in Musculoskeletal Radiology Vol. 18 No.

1/2014