Tutorial on Tutorial on Ultrasound Ultrasound

Imaging Imaging ArtefactsArtefacts

Uni of SA Uni of SA

Ultrasound Physics 1Ultrasound Physics 1Prepared by Sean McPeakePrepared by Sean McPeake

Artefact 1Artefact 1

The artefact seen deep to the measured structure on the image below is one of the important criteria in the diagnosis of this lesion.

[1] Name the artefact and the lesion.

[2] Discuss the formation of the artefact.

The artefact in question has aided in the diagnosis of this lesion ( ) too!

Artefact 2Artefact 2[1] Name the artefact seen deep to the renal calculus in Image A and discuss its formation.

When a calculus is small, like the one seen at the left ureteric orifice in Image B, little or no shadowing will be seen.

[2] Approximately how big must a calculus be to cast a shadow?

[3] Why is the depth of the calculus important?

[4] What imaging parameter changes could be made to improve the visualisation of the shadow behind such a small calculus? Explain your answers.

Image A Image B

Artefact 2 may be seen deep to calculi as in Image A but it may also be seen deep to bowel gas as in Image B. Differentiate between the two shadows seen

Image AImage B

Artefact 3Artefact 3This image is of a surgical staple in the dorsal aspect of a foot. The staple itself is the linear echogenic structure a little under 1 cm long.

[1] Name the artefact seen deep to the staple.

[2] Explain in detail the formation of this artefact

Image A Image B

In image A & B the same small cortical cyst in the left kidney is being imaged. For Image A the transducer was placed directly over the cyst in both the beamwidth and slice thickness planes. For Image B an angled approach was used.

Explain the relative ‘masking’ of the cyst in Image A.

Artefact 4Artefact 4In the posterior aspect of this urinary bladder false echoes (blue arrow) are shown within the lumen of the bladder. Name and discuss the formation of this artefact

More anteriorly in the bladder further false echoes are shown (red arrow) Name and discuss the cause of these echoes.

Artefact 5Artefact 5This image was taken at right angles to the one on the previous slide. What do you think is the cause of the false echoes seen in the posterior aspect of the bladder? Name the artefact involved and contrast it to the artefact seen in the posterior part of the bladder on the previous slide.

Complete this statement. Artefacts 4 & 5 are both P _ _ _ _ _ _ V _ _ _ _ _ artefacts

Artefact 6Artefact 6

Name and with the aid of a sketch describe the formation of the artefact causing the curvilinear band of false echoes through the urinary bladder in the image below.

Artefact 7Artefact 7

Image A Image B

Images A & B are transverse images of the abdominal aorta. For Image A the transducer was placed slightly away from the midline, whereas in Image B the transducer was on the abdominal midline.

Explain with the aid of a diagram why the aorta has a ‘double barrel’ appearance in Image B.

From most angles there seems to be only one calculus in the left VUJ, but when scanning in the midline there at times appears to be two. Explain.

MIDLINE SCAN

Abnormal thickening of the nuchal fold >6mm at 18-20 weeks gestation has a strong association with chromosomal abnormality. When this fetus’ nuchal fold was scanned through a midline approach the fold looked thick. However with an oblique scan away from the midline it looked normal. Explain

Artefact 8 & 9Artefact 8 & 9

Image A Image B

Though the appearance on the image is similar the cause of the artefacts shown in Image A & B are different. In Image A the artefact is caused by the presence of gas in the biliary tree. In Image B the artefact is caused by the presence of crystals in abnormal sinuses in the gall bladder wall.

Name the two different artefacts and briefly discuss the formation of each.

Artefact 10Artefact 10In this coronal image the upper pole of the left kidney is being imaged through the spleen but the lower pole is not. Although only mild in this case, explain what has caused the apparent ‘fractured’ appearance to the kidney.

Ultrasound imaging identified a contour abnormality and probable solid mass at the upper pole of this left kidney (blue arrow). However subsequent contrast enhanced CT scanning of the abdomen revealed no abnormality here. What is the cause of this ‘pseudo-mass’ then?

Another example of the same artefact.

Artefact 11 Artefact 11 A subtle but appreciable bend appears to have occurred in the needle as it passes from subcutaneous fat to breast tissue during this FNAB. When the procedure was complete the needle was examined carefully and appeared completely straight. What is the explanation of this appearance?

Another example of Artefact 11

Artefact 12Artefact 12

Image A Image B

In abdominal ultrasound imaging the soft tissue-air interface adjacent the diaphragm almost invariably gives rise to apparent liver-like tissue superior to the diaphragm on the image. On occasions a there will be an apparent double image of a specific structure, such as the small haemangioma in Image A or the Hepatic vein and IVC in Image B.

With the aid of a diagram explain the formation of these double images.

During this Paediatric Renal Ultrasound Scan a cystic lesion (blue star) was transiently seen deep to the urinary bladder. The lesion strangely seemed to come and go as gas in the bowel deep to the bladder peristalsed around. When the patient emptied their bladder, careful scanning showed no cyst in the pelvis.

Give a explanation of this imaging artefact.

Artefact 13Artefact 13

Image A Image B

Image A & B are of the same section of the same Achilles tendon. The only technical difference between the two Images is a subtle change of scan angle between images. The anechoic area (blue arrow) in Image B is not real. Discuss the cause of this artefact.

The anechoic area (blue star) at the insertion of this supraspinatus tendon is another example of the artefact seen on the previous slide. This artefact is very common in the supraspinatus tendon because the tendon fibres curve over the humeral head. Briefly explain how a sonographer overcomes this in the practical setting.

Equipment Artefacts Equipment Artefacts

During this Early Pregnancy scan the transducer was accidentally dropped. When scanning resumed a vertically aligned anechoic band was seen in a constant location down the left hand side of the image.

Explain these appearances.

Note appearance of active transducer wiped clean with an isowipe

Operator ArtefactsOperator Artefacts

Image A Image B

Both of the images below are not of diagnostic quality. Explain why and what likely operator errors have caused the artefact in each case.