Knobology: A guide to ultrasound scanners and settings for Rheumatologists

Transcript

1. Knobology Dr Daniel Fascia Consultant Musculoskeletal Radiologist E ff ective use of Ultrasound equipment
2. Table of Contents • The ultrasound scanner - a visual tour • Probes - when to use • Parameters for scanning • What it means • What it does • Effective use • Live Demonstration of parameters (with Dr Rahoz Aziz)
3. Typical Radiology USS setup
5. Ergonomics - for patient, for operator Equipment - more than just a machine Posture and positioning Cleaning & maintenance of machine / environment
6. The Ultrasound Scanner • Screen (hint: it moves) • Gel holder (warms it) • Probe holders • Secondary screen (setting state) • Keyboard (pretty useless - labels) • Knobs a plenty (parameters) • Trackball + buttons • Motorised handles (positioning) • Probes and their cables
7. The Key Parametric Controls
9. Gain Depth Colour Doppler Power Doppler Pulse Wave Doppler Freeze Frame Store it… Frequency Focus The mouse
10. Time Gain Compensation Display of settings and Advanced controls
11. Don’t be duped into buying an USS machine with only a touch screen. Lack of haptic feedback. Need to look away from the output display / patient to change settings. Manufacturers cheaping out. Buttons are best
12. Probe selection
13. Curved Linear Micro-linear (hockey stick)
14. Curved Linear Micro-linear (hockey stick)
15. Zero role for this probe in Musculoskeletal imaging
16. Does it all. Large footprint. Tendinopathic supraspinatus
17. Does it all. Large footprint. MCP joint and f lexor tendon
18. Similar but magni f ied view. Flexor tenosynovitis
19. Choosing probes for MSK & Rheumatology
20. Parameters
21. Gain • “Turn up the volume” • Ampli f ies returning sound waves • Uniform brightness increase • Increase: reduces contrast • Decrease: increases contrast • Too high: washed out image • Too low: dark, nothing to see • Degree of personal preference!
22. Overall Gain
23. Time Gain Compensation • Tune the Graphic equalizer • Selective adjustment of brightness at different depths • Corresponds to different sound wave frequencies • Basically: make the deep bits brighter (in reality…) • Consider if that frequency is the issue in reality
24. Time Gain Compensation (EQ) Nothing applied Deep boost curve
25. Time Gain Compensation (EQ) Nothing applied Deep boost curve
26. Depth • “Framing of the anatomy” • Adjusts how deep the ultrasound scans by changing the range of echoes displayed. • More depth: Lower frame rate + larger f ield of view. • Too shallow: missing anatomy • Too deep: reduced spatial resolution, tiny structures. Wasted space.
27. Depth Truncating deeper anatomy Redundant space on bottom of image
28. Frequency • “Bass, mid, high” • USS emit soundwaves (MHz range) • High freq (super f icial structure): • High spatial resolution • Low penetration • Low freq (Deep structure): • Lower spatial resolution • Deeper penetration
29. Frequency 8Mhz 10MHz 18MHz
30. Practical Guide to Frequency Presets are your friend if this makes your head hurt
31. Focus • Let’s make this easy… • Place the focus arrow just deep to the thing you are interested in • Or use a machine that autofocuses
32. Doppler • Potentially complex • Doppler effect to detect transit of blood in and out of frames • Colour: Directional • Power: All directions considered • Pulse Wave: advanced waveforms • Microvascular f low Doppler
33. Rheumatology: Algorithm 1. Forget Doppler: Get good anatomical B-mode images 2. If you see synovial thickening, tenosynovitis, effusion, erosion 3. Stabilise image + invoke Doppler 4. Colour Doppler vs Power Doppler: It doesn’t matter* 5. Summative Assessment: History, examination, biochemistry, anatomical scan + functional overlay (Doppler) * Dr Fascia thinks Power Doppler is a scam
34. Comparison of Doppler Techniques
35. Comparison of Doppler Techniques Default Power Doppler settings tend to be more suitable for Rheumatology use case (synovitis)
36. Advanced Doppler Learn to customise Doppler settings for your machine Pulse Repeat Frequency (500-700Hz) for synovitis MCP/PIPJs Low wall f ilter Moderate gain Avoid: Overgain, too low a wall f ilter, excessive probe pressure Calibrate yourself to the Doppler sensitivity
37. Cautionary tales with Doppler
38. Motion: operator
39. Chatty patient 💬 Tell the patient to politely shut up when you scan them
40. Doppler FOV too large Low anatomical detail: Low frame rate: Artefacts
41. Doppler FOV too small Not a good overview of the synovium and tenosynovium
42. False positives: Arteries, Veins nearby Con f irm with Pulsed Wave Doppler Venous waveform Reverse arterial waveform
43. Appropriate sizing and positioning Flexor tendon is the structure of Doppler interest in this case
44. Panoramic Imaging Great for long, continuous structures Excellent anatomical overview Operator technical skill to pull it off Higher end machines Panorama image of whole f inger palmar surface, f lexor tendon, sheath and all joints DP IP PP MC
45. Live Demonstration Parameters in action by Dr Rahoz Aziz