Types of artifacts
• Artifacts associated with ultrasound beam
• Artifacts associated with multiple echoes.
• Artifacts associated with velocity errors.
• Artifacts associated with attenuation errors.
ARTIFACTS ASSOCIATED WITH ULTRASOUND
• ultrasound beam exits the transducer as a complex threedimensional bow-tie shape with additional off-axis lowenergy beams – side lobes.
• A strong reflector located outside of the main ultrasound
beam may generate echoes that are detectable by the
transducer. These echoes will be falsely displayed as
having originated from within the main beam.
BEAM WIDTH ARTIFACT
• Caused due to the widening of the main beam after the
• Image quality may be improved by adjusting the focal zone
to the level of interest and by placing the transducer at the
center of the object of interest.
ARTIFACTS ASSOCIATED WITH
• US assumes that an echo returns to the transducer after a
single reflection and that the depth of an object is related
to the time for this round trip.
• In the presence of two parallel highly reflective
surfaces, the echoes generated from the ultrasound beam
may be repeatedly reflected back and forth before
returning to the transducer for detection.
• The echo that returns to the transducer after a single
reflection will be displayed in the proper location. The
sequential echoes will take longer to return to the
transducer, and the ultrasound processor will erroneously
place the delayed echoes at an increased distance from
• At imaging, this is seen as multiple equidistantly spaced
linear reflections and is referred to as reverberation
COMET TAIL ARTIFACT
• Comet tail artifact is a form of reverberation.
In this artifact, the two reflective interfaces and thus
sequential echoes are closely spaced. On the display, the
sequential echoes may be so close together that
individual signals are not perceivable.
In addition, the later echoes may have decreased
amplitude secondary to attenuation; this decreased
amplitude is displayed as decreased width.
• The result is an artifact caused by the principle of
reverberation but with a triangular, tapered shape.
RING DOWN ARTIFACT
• In ring-down artifact, the transmitted ultrasound energy
causes resonant vibrations within fluid trapped between a
tetrahedron of air bubbles. These vibrations create a
continuous sound wave that is transmitted back to the
transducer. This phenomenon is displayed as a line or
series of parallel bands extending posterior to a gas
The display shows a bright reflector with an echogenic line
Left lateral decubitus US image of the gallbladder shows air and
fluid in the duodenum causing ring-down artifact.
MIRROR IMAGE ARTIFACTS
• Mirror image artifacts are also generated by the false
assumption that an echo returns to the transducer after a
• In this artifact, the primary beam encounters a highly
reflective interface. The reflected echoes then encounter
the “back side” of a structure and are reflected back
toward the reflective interface before being reflected to the
transducer for detection.
ARTIFACTS ASSOCIATED WITH VELOCITY
SPEED DISPLACEMENT ARTIFACT
• When sound travels through material with a velocity
significantly slower than the assumed 1540 m/sec, the
returning echo will take longer to return to the transducer.
• The image processor assumes that the length of time for a
single round trip of an echo is related only to the distance
traveled by the echo.
The echoes are thus displayed deeper on the image than
they really are.
• This is referred to as the speed displacement artifact
This artifact is encountered when the ultrasound beam
encounters an area of focal fat.
• A change in velocity of the ultrasound beam as it travels
through two adjacent tissues with different density and
elastic properties may produce a refraction artifact.
• In refraction, non-perpendicular incident ultrasound
energy encounters an interface between two materials
with different speeds of sound. When this occurs, the
incident ultrasound beam changes direction.
• The ultrasound display assumes that the beam travels in
a straight line and thus misplaces the returning echoes to
the side of their true location.
ARTIFACTS ASSOCIATED WITH ATTENUATION
• When the ultrasound beam encounters a focal material
that attenuates the sound to a greater
or lesser extent than in the surrounding tissue, the
strength of the beam distal to this structure will be either
weaker or stronger than in the surrounding field.
• Attenuation is also dependent on the frequency of the
ultrasound. Attenuation increases with increase in
• In soft tissues, the relationship between attenuation and
frequency is linear. In bone and water, attenuation
increases as the square of the frequency. In clinical
imaging, the different tissues an ultrasound beam
encounters attenuate the beam differently.
COLOR COMET-TAIL ARTIFACT
• The color comet-tail artifact is a rapidly alternating color
Doppler signal that occurs immediately deep in relation to
the object causing it. The artifact appears on images as a
linear aliased band of color.
• Can be accentuated by using maximum color gain and low
frequency curvilinear probes.
• Also called „twinkling sign‟.
• This artifact is not always reproducible, the causes not
• Can be used to image calcifications in various organs
where grey scale ultrasound may not be helpful.
• Is critical in identifying stones in the CBD especially in
mildly dilated or normal ducts.
• The artifact is helpful in imaging of patients with cystic
fibrosis in whom intrahepatic biliary stones are suspected
clinically but there are few or no gray-scale findings.
• Is useful in diagnosing subtle pancreatic and splenic
• In the kidney it is useful in diagnosing small calculi and
• There is higher sensitivity for identifying calculi in the
ureter, PUJ and cyst calcifications when this artifact is
• The color comet-tail artifact is helpful in evaluating intimal
plaques in the carotid system, abdominal aorta, and
peripheral arterial system.
• The color comet-tail artifact has been used in
identification of catheter tips and surgical clips, can aid
localization of needle tips during sonographically guided
biopsy, and can even help identify foreign bodies. In
appendicitis, an appendicolith can produce the artifact.
COLOR DOPPLER SONOGRAM SHOWS PROMINENT COLOR COMET-TAIL
ARTIFACT FROM STONE (ARROW) WITHIN NONDILATED COMMON BILE DUCT.
COLOR COMET-TAIL ARTIFACT CAN HELP DIFFERENTIATE POLYPS ON
NONDEPENDENT WALL OF GALLBLADDER FROM ADENOMYOMATOSIS.
• Composed of microbubbles.
• Consists of a microbubble shell usually made of
albumin, galactose, lipid or polymers and a gas core
composed of air or heavy gases like perfluorocarbon or
• Microbubbles have a high degree of echogenicity. The
echogenicity difference between the gas in the
microbubbles and the soft tissue surroundings of the
body is immense. Thus the microbubble contrast agents
enhances the reflection of the ultrasound waves, to
produce a unique sonogram with increased contrast due
to the high echogenicity difference.
• CEUS requires contrast-specific software on the
ultrasound equipment that suppresses the signal from the
background tissue leaving only the signal from the
• Pulse inversion harmonic imaging is used whereby two
signals are sent down a single scan line and the second is
a mirror image of the first. Echoes from both pulses are
collected by the transducer and summed.
• Linear reflectors, such as normal tissue, produce no net
signal. However, nonlinear reflectors, such as
microbubbles, produce echoes that are asymmetric and
do not sum to zero. The result is that echoes from bubbles
are detected preferentially using this method, improving
image contrast between tissue and microbubbles.
• Microbubbles are attached with ligands that bind certain
molecular markers that are expressed by the area of
imaging interest are then injected systemically in a small
• Microbubbles theoretically travel through the circulatory
system, eventually finding their respective targets and
• The ultrasound system converts the strong echogenicity
into a contrast-enhanced image of the area of
interest, revealing the location of the bound microbubbles.
• Inflammation: Contrast agents may be designed to bind to
certain proteins that become expressed in inflammatory
diseases such as Crohn's disease and atherosclerosis.
• Thrombosis and thrombolysis: Activated platelets are
major components of blood clots (thrombi). Microbubbles
can be conjugated with a ligand specific for activated
glycoprotein IIb/IIIa (GPIIb/IIIa), which is the most
abundant platelet surface receptor. The microbubbles will
specifically bind to activated platelets and allow real-time
molecular imaging of thrombosis, such as in myocardial
• Can also be used to image malignant tissues, as a way to
deliver genes and drugs to the tissues.
Organ Edge Delineation: Microbubbles can enhance the
contrast at the interface between the tissue and blood.
Blood Volume and Perfusion: contrast-enhanced ultrasound
holds the promise for (1) evaluating the degree of blood perfusion
in an organ or area of interest and (2) evaluating the blood volume
in an organ or area of interest.
Lesion Characterization: contrast-enhanced ultrasound plays a
role in the differentiation between benign and malignant focal liver
APPROVED CONTRAST AGENTS IN INDIA
• SonoVue® - (sulphur hexafluoride microbubbles) Left
ventricular opacification / endocardial border
definition, breast, liver, portal vein, extracranial
carotid, peripheral ateries (macrovascular and
• Definity® - (Perflutren lipid microsphere) Left ventricular
opacification / endocardial border definition, liver, kidney.
• Piscaglia and Bolondi, in a retrospective review of
European experience with the use of microbubble contrast
agents in more than 23,000 patients, reported adverse
effects (AE) in 29 cases, of which only two were graded as
serious; the rest, 27, were nonserious (23 mild, three
moderate and one severe). The overall reporting rate of
serious AE was 0.0086%. Overall, only four AEs required
treatment (two serious, two nonserious including one
moderate and one severe AEs).
CHARACTERIZATION OF LIVER LESIONS.
In a study by Fuminori et all, the overall rate of correct
diagnosis of lesions by the blinded reviewers significantly
improved from 68.4% for unenhanced ultrasound to 88.9% for
CEUS. In addition, the overall rate of correct diagnosis with
CEUS was significantly higher than that with CT (80.5%). In
classification of the lesions into the five types, the rates of
correct diagnosis of HCC, metastasis, and hemangioma were
significantly higher for CEUS than for unenhanced
ultrasound. In particular, all 17 cases of hemangioma were
correctly diagnosed with CEUS (100%). The performance of
CEUS in the correct diagnosis of metastasis was superior to
that of CT.
In terms of correct classification of lesions as malignant or
benign, the overall accuracy and sensitivity significantly
improved from 86.3% and 89.0% for unenhanced ultrasound
to 97.4% and 98.8% for CEUS
SOME OF THE CURRENT USES OF CEUS.
• Contrast enhanced voiding urosonography.
• Monitoring of tumor response to anti-angiogenic therapy.
• Monitoring of local ablative therapy in HCC and
• Characterization of kidney lesions.
• Charecterization of liver lesions.
• To characterize pancreatic lesions.
• Blunt abdominal trauma.
• Transcranial vascular imaging.
• Assessment of atherosclerotic plaques.
• US Artifacts. Myra K. Feldman, Sanjeev Katyal, Margaret
S. Blackwood. Radiographics, 2009.
• Sonographic Artifacts and Their Origins. Kathleen A.
Scanlan. AJR Am J Roentgenol. 1991 Jun;156(6):1267-72.
• Color Comet-Tail Artifact: Clinical Applications. Hisham
Tchelepi, Philip W. Ralls. AJR, 2009.
• Contrast-Enhanced Ultrasound: What Is the Evidence and
What Are the Obstacles?. Stephanie R. Wilson, Lennard D.
Greenbaum. AJR, DOI:10.2214/AJR.09.2553.