Advanced Self-Assessment Questions: Images

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Appendix 4 Advanced Self-Assessment Questions: Images

1. The following sonogram shows air injected into the field of imaging. Which of the following is true:

A. The acoustic impedance of air is markedly high and therefore results in a strong echo reflection within soft tissue.

B. The acoustic impedance of air is markedly low and therefore results in a strong echo within soft tissue.

C. The acoustic impedance of air is markedly high and therefore results in no echo within soft tissue.

D. The acoustic impedance of air is markedly low and therefore results in no echo within soft tissue.

2. The artifact shown above is:

A. caused by differences in the speed of sound within the overlying soft tissue.

B. caused by refraction that occurs at the interface of tissues with different speeds of sound.

C. referred to as bayonet artifact because of the resemblance of the needle echoes to the shape of a bayonet.

D. all of the above.

3. The artifact shown above is:

A. caused by differences in attenuation of sound waves within the overlying soft tissue and blood vessels.

B. caused by differences in the speed of sound within the overlying soft tissue.

C. referred to as posterior acoustic enhancement because the deeper echoes are amplified.

D. all of the above.

4. Given the image shown above (A), the transducer manipulation most likely (or necessary) to place the entire needle tip and shaft within the field of imaging (B) is (a small amount of):

A. compression.

5. While scanning the cervical triangle, the following sonogram is obtained.

Please identify:

A. the sternocleidomastoid muscle.

B. the anterior and posterior tubercles of a cervical transverse process.

C. a ventral ramus.

6. While scanning the infraclavicular region, the following sonogram is obtained. Please identify:

A. the pectoralis major muscle.

B. the pectoralis minor muscle.

C. the second part of the axillary artery.

D. the axillary vein.

E. the medial cord of the brachial plexus.

7. While scanning the subgluteal region, the following sonogram is obtained. Please identify:

A. the conjoint tendon of the semitendinosus and biceps femoris.

C. the sciatic nerve.

Answers to Image Questions

Echo reflections are determined by acoustic impedance mismatch. If there are large changes in acoustic impedance, a strong echo results. The acoustic impedance of air is very low because it is very compressible.

CLINICAL SIGNIFICANCE: If air is injected into the field, acoustic shadowing will result. Note that the term “anechoic” implies absence of echoes with sound transmission (and not necessarily a dark image display that can result from sound absorption or reflection).

REFERENCE: Gray AT. Ultrasound-guided regional anesthesia: current state of the art. Anesthesiology 2006;104:368–73.

These are characteristics of bayonet artifact.

CLINICAL SIGNIFICANCE: Structures are only displayed in their true anatomic position if the speed of sound in soft tissue is the same as that assumed to interconvert time and distance for echo ranging (1540 m/sec). Sometimes this results in a needle trajectory that is not anticipated, particularly during lateral approach to popliteal block.

REFERENCE: Gray AT, Schafhalter-Zoppoth I. “Bayonet artifact” during ultrasound-guided transarterial axillary block. Anesthesiology 2005;102:1291–2.

These are characteristics of posterior acoustic enhancement artifact.

CLINICAL SIGNIFICANCE: Posterior acoustic enhancement artifacts can resemble echogenic peripheral nerves. This is particularly common in the infraclavicular and femoral regions because echoes deep to the axillary and femoral arteries are amplified and yet not attenuated like other parts of the sound field.

REFERENCE: Filly RA, Sommer FG, Minton MJ. Characterization of biological fluids by ultrasound and computed tomography. Radiology 1980;134(1):167–71.

A partial lineup with in-plane technique is shown.

CLINICAL SIGNIFICANCE: This is one of the most common mistakes by novices when learning in-plane approach to regional blocks. One of the first skills to learn for ultrasound-guided interventions is to correctly distinguish the needle tip and shaft.

REFERENCE: Sites BD, Spence BC, Gallagher JD, et al. Characterizing novice behavior associated with learning ultrasound-guided peripheral regional anesthesia. Reg Anesth Pain Med 2007;32(2):107–15.

Answer 5: See labeled sonogram.

CLINICAL SIGNIFICANCE: Ultrasound landmarks for regional block.

Answer 6: See labeled sonogram.

CLINICAL SIGNIFICANCE: Ultrasound landmarks for regional block.

Answer 7: See labeled sonogram.

CLINICAL SIGNIFICANCE: Ultrasound landmarks for regional block.

Related

Atlas of Ultrasound-Guided Regional Anesthesia 2e