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PHYSICS > CH 20 - ARTIFACTS > Flashcards

CH 20 - ARTIFACTS Flashcards

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0
Q

ARTIFACT RESULT FROM?

A
  • VIOLATION OF ASSUMPTIONS
  • EQUP MALFUNCTION OR POOR DESIGN
  • PHYSICS OF U/S
  • OPERATOR ERROR
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1
Q

THISIS SIMPLY AN ERROR IN IMAGING?

A

ARTIFACT

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2
Q

WHAT ARE THE 6 ASSUMPTIONS OF IMAGING SYSTEM?

A
  • 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.
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3
Q

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.

A

REVERBERATION

RESEMBLES A LADDER

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4
Q

THIS IS AN ARTIFACT THAT APPEARS AS A SOLID HYPERECHOIC LINE DIRECTED DOWNWARD. IS CREATED WHEN CLOSELY SPACED REVERBERATIONS MERGE LIKE GAS BUBBLES.

A

COMET TAIL AKA RING DOWN ARTIFACT

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5
Q

THIS APPEARS AS A HYPOECHOIC OR ANECHOIC REGION EXTENDING DOWNWARD FROM A VERY STRONG ATTENUATING MEDIUM.

A

SHADOWING

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6
Q

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.

A

EDGE SHADOW

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7
Q

THIS APPEARS AS A HYPERECHOIC REGION BENEATH TISSUES WITH ABNORMALLY LOW ATTENUATION. NOT RELATED TO SPEED.

A

ENHANCEMENT

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8
Q

THIS IS A FORM OF ENHANCEMENT THAT APPEARS FROM SIDE-TO-SIDE OF AN IMAGE. APPEARS AS AN INCORRECT TGC SETTING.

A

FOCAL ENHANCEMENT

RESULTS FROM INCREASED INTENSITY AT THE FOCUS.

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9
Q

THIS ARTIFACT IS CREATED WHEN SOUND REFLECTS OFF OF A STRONG REFLECTOR AND IS REDIRECTED TWD A 2ND STRUCTURE. CAUSING A REPLICA.

A

MIRROR IMAGE

IT WILL BE PLAED DEEPER THAN THE REAL STRUCTURE.
A BRIGHT REFLECTOR LIES ON A STRAIGHT LINE BETWEEN ARTIFACT & TRD.

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10
Q

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.

A

SPEED ERROR

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11
Q

IF THE SPEED ERROR IS GOING FASTER THAN SOFT TISSUE THE DISTANCES WILL BE TOO?

A

SMALL

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12
Q

IF THE MEDIUM’S SPEED IS SLOWER THAN THAT IN SOFT TISSUE THE DISTANCES WILL BE TOO?

A

LARGE

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13
Q

WHAT ARE SPEED ERRORS ALSO CALLED?

A

RANGE ERROR ARTIFACT OR RANGE AMBIGUITY ARTIFACT

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14
Q

WHAT ARE THE CHARACTERISTICS OF SPEED ERRORS?

A
  • CORRECT # OF REFLECTORS
  • IMPROPER DEPTH
  • APPEARS AS A STEP-OFF
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15
Q

THIS ARTIFACT APEARS WHEN SOUND ENERGY IS TRANSMITTED IN A DIRECTION OTHER THAN ALONG THE BEAM’S MAIN AXIS.

A

LOBES - ARE WEAKER THAN THE PRIMARY BEAM. THEY DEGRADE LATERAL RESOLUTION

16
Q

THIS TYPE OF LOBE IS CREATED BY USING A SINGLE CRYSTAL TRD LIKE A MECHANICAL PROBE.

A

SIDE LOBES

17
Q

THIS LOBE IS CREATED BY USING AN ARRAY TRD.

A

GRATING LOBES

18
Q

THE PROCESS OF DIFFERENTIAL EXCITATION THAT IS USED TO CORRECT GRATING LOBES IS?

A

APODIZATION

19
Q

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.

A

REFRACTION - CAUSES A SIDE BY SIDE COPY AT THE SAME DEPTH

20
Q

THIS IS AN ELEVATIONAL PLANE ARTIFACT THAT APPEARS WHEN THE BEAM DIMENSION IS GREATER THAN THE REFLECTOR SIZE.

A

SLICE THICKNESS

  • IS REDUCED BY A 1 1/2 DIMENSIONAL ARRAY TRD
21
Q

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
A

LATERAL RESOLUTION

22
Q

THIS IS CREATED WHEN A LONG PULSE STRIKES 2 CLOSELY SPACES STRUCTURES THAT ONE IS IN FRONT OF THE OTHER.

A

AXIAL RESOLUTION

PHYSICS (2 decks)

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