Few important points on the basics of muscloskeletal ultrasound

1. Fundamentals of
Musculoskeletal Ultrasound
By
Samar Tharwat
Lecturer of Internal Medicine
(Rheumatology & Immunology)

3. Introduction
Ultrasonography:
• Safe
• Low-cost
• No ionizing radiation
• Few technical limitations
• Real-time dynamic studies and interventions
• Easy comparison with the contralateral side

4. Limitations of MSK US
• Limited field of view
• Lower resolution at greater depths
• Unable to penetrate bone
• Operator dependent
• Equipment – cost

5. BASIC PHYSICS

6. Frequency
• Higher frequency =a better resolution
• Lower frequency = better penetration.

7. • Overview and guidance:7.5 and 10 MHz
• Deeper-located structures (hip & shoulder):2–6 MHz
• Detailed study: 15–18 or 20 MHz
a.3.5 MHz
b.8 MHz
c.18 MHz

8. Reflection
• The higher the reflection, the higher the
echogenicity (soft tissue/bone interface )( white)
• On the other hand, fluid in a bursa or blood
vessels has a very low acoustic impedance (black)

10. The transducer or probe
Types of transducers

11. Probe Markers
a Probe side with marker.
b Probe side with no marker

12. Different screen marker showing either companies logo or
initials’ letter

13. Button for flipping the screen marker from right to left

14. Probe Handling When
Scanning
• Longitudinal: towards the patient head
• The transverse: to the right side

15. Transducer positioning
• Simultaneous contact with:
Transducer
Skin surface,
Examiner’s hand
• Maintains proper pressure of transducer
on the skin

16. Gain
• Obtain an interpretable image
• Decreased gain will give a black image
• Increased gain will give a white image

17. Depth adjustment
• It is best to have the structure that is being
examined in the center of the screen

18. Focal Zone
• Set Focal Zone to location of interest

19. Magnification scale (scale, zoom)
Image magnification. a Non-enlarged image ( arrow shows the region which is
enlarged in B). b Magnified image. c Zoom button

20. Color Flow Imaging (CFI)
• Blood flow ( direction&velocity)

21. Power Doppler Imaging (PDI)
• Amplitude of the Doppler signal
• More sensitive (Small vessels)

22. Echogenicity

23. Terminology
• Anechoic : black image (fluid)
Transonic image— a superficial vein

24. Hyper-, iso- , or hypoechoic
• Hyperechoic: brighter than the reference structure
• Hypoechoic: darker

32. All ultrasound machines are equipped
with various facilities:
• Measurement: distances, perimeters, areas..etc
• Marking areas of interest
• General information: date, time, transducer
frequency ,operating mode of the device, the
institution
• Images are stored on sensitive papers or on
devices with large capacity of digital memory

33. Pitfalls in Musculoskeletal Ultrasound

34. Oxford English dictionary defines artifacts:
“something observed in a scientific
investigation or experiment that is not
naturally present.”

35. Classification of US pitfalls

36. Artifacts Due to Transducer
Position
• Anisotropy:
• US beam is not strictly perpendicular to
the examined tissue mostly in tendons
mainly at the point of its insertion

37. • Anisotropy can be beneficial for confirming tendon position
• The artifact can be produced in the linear tendon while the
surrounding nonlinear echogenic fat is not affected
Anisotropy of the triceps tendon, it
shows a hypoechoic area at its
distal end (a) which
disappeared on correcting the
probe angulation (b)

38. Transducer Handling

39. Acoustic shadow
• Focal attenuation of ultrasound due to complete reflection
(bone or calcification and some foreign bodies)
Acoustic shadow extends posterior to intramuscular calcification ( arrow)

40. Shadowing
• Clean: bone

41. lateral shadowing
Subcutaneous cyst, showing lateral shadows due to refraction ( arrows)

42. Acoustic enhancement (amplification)
Selective increasing in the intensity of echoes
beyond an anechoic structure (a cystic structure or
blood vessel)
Acoustic enhancement extends posterior to baker cyst ( arrow)

43. Reverberation
Transverse view on the anterior shoulder. An anechoic
image (subdeltoid bursitis) is shown under deltoid muscle
with a needle inserted in it. Reverberation artifact of the
needle is shown behind it ( arrows)

44. Cartilage Interface Sign

45. Drop-Out Pitfall

46. Insufficient Knowledge of the
Machine Settings

47. Taking a good ultrasound picture is
an art. Interpreting it is a science

48. The Third Eye of the Rheumatologist