CH 20 - ARTIFACTS Flashcards
ARTIFACT RESULT FROM?
- VIOLATION OF ASSUMPTIONS
- EQUP MALFUNCTION OR POOR DESIGN
- PHYSICS OF U/S
- OPERATOR ERROR
THISIS SIMPLY AN ERROR IN IMAGING?
ARTIFACT
WHAT ARE THE 6 ASSUMPTIONS OF IMAGING SYSTEM?
- SOUND TRAVELS IN A STRAIGHT LINE
- SOUND TRAVELS STRAIGHT TO A REFLECTOR & BACK
- SOUND TRAVELS IN SOFT TISSUE AT EXACTLY 1540 M/S
- REFLECTIONS ONLY HAPPEN FROM STRUCTURES IN THE BEAMS MAIN AXIS
- IMAGING PLANE IS VERY THIN
- STRENGTH OF REFLECTION IS RELATED TO THE TISSUE CREATING THE REFLECTION.
THIS IS AN ARTIFACT THAT IS DISPLAYED AS MULTIPLE, EQUALLY SPACED ECHOES CAUSED BY THE BOUNCING OF SOUND WAVE BETWEEN 2 STRONG REFLECTORS POSITIONED PARALLEL TO THE U/S.
REVERBERATION
RESEMBLES A LADDER
THIS IS AN ARTIFACT THAT APPEARS AS A SOLID HYPERECHOIC LINE DIRECTED DOWNWARD. IS CREATED WHEN CLOSELY SPACED REVERBERATIONS MERGE LIKE GAS BUBBLES.
COMET TAIL AKA RING DOWN ARTIFACT
THIS APPEARS AS A HYPOECHOIC OR ANECHOIC REGION EXTENDING DOWNWARD FROM A VERY STRONG ATTENUATING MEDIUM.
SHADOWING
THIS IS A FORM OF SHADOWING THAT APPEARS AS A HYPOECHOIC REGION THAT EXTENDS ALONG A CURVED REFLECTOR. IT IS CAUSED BY A DIVERGED BEAM THAT RESULTS IN A DROP OF ITENSITY.
EDGE SHADOW
THIS APPEARS AS A HYPERECHOIC REGION BENEATH TISSUES WITH ABNORMALLY LOW ATTENUATION. NOT RELATED TO SPEED.
ENHANCEMENT
THIS IS A FORM OF ENHANCEMENT THAT APPEARS FROM SIDE-TO-SIDE OF AN IMAGE. APPEARS AS AN INCORRECT TGC SETTING.
FOCAL ENHANCEMENT
RESULTS FROM INCREASED INTENSITY AT THE FOCUS.
THIS ARTIFACT IS CREATED WHEN SOUND REFLECTS OFF OF A STRONG REFLECTOR AND IS REDIRECTED TWD A 2ND STRUCTURE. CAUSING A REPLICA.
MIRROR IMAGE
IT WILL BE PLAED DEEPER THAN THE REAL STRUCTURE.
A BRIGHT REFLECTOR LIES ON A STRAIGHT LINE BETWEEN ARTIFACT & TRD.
THIS IS CREATED WHEN A SOUND WAVE PROPAGATES THROUGH A MEDIUM AT A SPEED OTHER THANT THAT OF SOFT TISSUE. CORRECT NUMBER OF REFLECTORS ARE DISPLAYED JUST APPEAR AT THE WRONG DEPTH.
SPEED ERROR
IF THE SPEED ERROR IS GOING FASTER THAN SOFT TISSUE THE DISTANCES WILL BE TOO?
SMALL
IF THE MEDIUM’S SPEED IS SLOWER THAN THAT IN SOFT TISSUE THE DISTANCES WILL BE TOO?
LARGE
WHAT ARE SPEED ERRORS ALSO CALLED?
RANGE ERROR ARTIFACT OR RANGE AMBIGUITY ARTIFACT
WHAT ARE THE CHARACTERISTICS OF SPEED ERRORS?
- CORRECT # OF REFLECTORS
- IMPROPER DEPTH
- APPEARS AS A STEP-OFF
THIS ARTIFACT APEARS WHEN SOUND ENERGY IS TRANSMITTED IN A DIRECTION OTHER THAN ALONG THE BEAM’S MAIN AXIS.
LOBES - ARE WEAKER THAN THE PRIMARY BEAM. THEY DEGRADE LATERAL RESOLUTION
THIS TYPE OF LOBE IS CREATED BY USING A SINGLE CRYSTAL TRD LIKE A MECHANICAL PROBE.
SIDE LOBES
THIS LOBE IS CREATED BY USING AN ARRAY TRD.
GRATING LOBES
THE PROCESS OF DIFFERENTIAL EXCITATION THAT IS USED TO CORRECT GRATING LOBES IS?
APODIZATION
THIS OCCURS WHEN A SOUND PULSE CHANGES DIRECTION DURING TRANSMISSION. OCCURS WHEN A SOUND WAVE STRIKES A BOUNDARY OBLIQUELY AND THE MEDIA ON EITHER SIDE OF THE BOUNDARY HAVE DIFFERENT PROP SPEEDS.
REFRACTION - CAUSES A SIDE BY SIDE COPY AT THE SAME DEPTH
THIS IS AN ELEVATIONAL PLANE ARTIFACT THAT APPEARS WHEN THE BEAM DIMENSION IS GREATER THAN THE REFLECTOR SIZE.
SLICE THICKNESS
- IS REDUCED BY A 1 1/2 DIMENSIONAL ARRAY TRD
THIS OCCURS WHEN A BEAM IS WIDER THAN THE DISTANCE BETWEEN TWO REFLECTORS THAT ARE LOCATED SIDE BY SIDE OR PERP TO THE BEAM.
- 2 OBJ’S APPEAR AS 1
- MAY DISPLAY A SMALL REFLECTOR AS A WIDE LINE
LATERAL RESOLUTION
THIS IS CREATED WHEN A LONG PULSE STRIKES 2 CLOSELY SPACES STRUCTURES THAT ONE IS IN FRONT OF THE OTHER.
AXIAL RESOLUTION
