This document provides guidance on optimizing ultrasound images for critical care applications. It discusses adjusting various image settings like depth, focal zones, harmonics and M-mode to improve image quality for assessing lungs, IVC, and heart. M-mode is recommended for measuring movement and dimensions more accurately than B-mode. The challenges of cardiac imaging are also covered, noting the need for higher frame rates and reduced averaging and spatial resolution to capture fast heart motion. Narrowing the sector width and decreasing depth can help optimize the cardiac image within these limits.

1. Image optimization for critical care US Critical Care Ultrasound Course SAH & RNSH 2011

2. Summary Revision: basic image optimization B- mode, M-mode, Doppler LUNG IVC HEART

3. Revision: basic image optimisation

4. Revision: basic image optimisation Patient position (supine? left lateral?) Lighting (dark) Enough gel Right probe Right orientation Right preset Right depth Overall gain Individual TGC/DGC sliders

5. Revision: basic image optimisation Frequency Focal Zones (how deep? how many?) Cheat buttons - Auto –optimize Harmonics Change your angle & pressure Zoom

6. Harmonics (THI) As a sound wave travels through tissue, the high pressure bit (compressing tissue) moves faster than the rarefactional component. This distorts the wave! and generates higher frequency components ( harmonics ) deep in the tissues. eg 3MHz wave creates 6MHz, 12 MHz harmonics

7. Harmonics (THI) Q: So what? A: it turns out that aberrant/artefact signals are too weak to generate harmonic waves. THI takes advantage of this: i.e. it displays only the harmonic signals. THI images have: reduced noise and clutter improved spatial resolution (harmonic beams are narrower than the original)

8. Same Kidney, difficult patient No Harmonics With Harmonics

9. Top tip: Harmonics (THI) = another great button Don ’t use it for the lung For other regions, give it a go If it makes the image worse, press again to turn it off Best for mid-depth images. harmonic generation does not take place near the skin, so THI no use there. Also less useful in far field.

10. M mode

11. M mode = motion mode Press ‘ M ’ button once & a line appears Use touch pad / track ball to move the line to area of interest Press ‘ M ’ again to plot a graph of what that line sees versus time Stationary stuff = straight line Moving things = curved/ dots

12. M-mode: what ’ s the point? CONS If angles wrong, measurements wrong! Easier to stuff up than B-mode IF IN DOUBT, USE B MODE PROS M-mode (motion mode) = movement along a single line of info against time Single line therefore much better sensitivity & resolution More accurate dimensions

13. M mode: poorly contractile LV

14. M mode: IVC changing with respiration

15. Doppler

16. Doppler effect Probe sends a sound wave of known frequency If it hits object moving towards probe, the returning sound wave is higher frequency If object moving away, the returning wave is lower frequency

17. Today: we leave Doppler alone Master the basics first Know your limitations

18. Sreening exam: scanning the lungs

19. LUNGS: probe & preset PROBE Not the linear array (too much fine detail!) … False neg PTX (movement) … False pos PTX (pain) The curved probe is best Image quality Anatomy The phased array probe fits b/w ribs & gets round the back PRESET One with plenty of greyscale/ dynamic range Abdo preset (abdo > FAST) NOT cardiac preset Turn off the fancy filters: THI, compounding/MB etc- they make the artefacts harder to see!

20. Depth & alignment DEPTH 5cm: just for pleura eg sliding 10cm: to confirm true B lines 15cm: anatomical relations, diaphragm, effusions PROBE ALIGNMENT Surprisingly, stay sagittal (perpendicular to ribs) Only turn parallel if interrogating structures further eg solid areas

21. Screening exam: the IVC

22. Probe & preset PROBE C urved probe is best Image quality Anatomy Phased array probe if already on TTE PRESET Whatever preset you’re on is fine

23. Screening exam: single view heart Keep it simple Same probe & preset

24. Trans thoracic echocardiogram (TTE) We ’re not in Kansas any more

25. B-mode top tips for cardiac scan Roll the patient to the left Sector /phased probe Cardiac preset (image ‘ round the wrong way ’ ) ‘ Jerky ’ image (less averaging) Dynamic range decreased (more contrast) Line density decreased Sector width narrowed ECG leads can help but we rarely have time! What does all this mean?

26. The bottom line The heart beats very quickly We need to capture this movement accurately So we maximise ‘ temporal resolution ’ = increased frame rate And we turn off averaging = only ‘ true ’ images are seen But we sacrifice something to achieve this: mainly spatial resolution i.e. the image has less anatomical detail = lower ‘ line density ’ And less greyscale /dynamic range (ie it ’ s a more ‘ black & white ’ picture) So we need to try certain ‘ tricks ’ to improve our image within these limits e.g: - decrease depth - zoom the image - decrease sector width

27. Why the jerky image? Image not as smooth No averaging = no ‘ fudging ’ What you see on screen is really there

28. What ’ s Line Density? How many lines per frame A high line density is desirable for high resolution imaging of small parts (thyroid, breast testes…), A lower line density is useful in cardiac applications as it allows significantly higher frame rates. Reference: LOGIQ 9 Basic User Manual, Direction 5140804 -100 Rev.3 5-24

29. Sector Width (Scan Area) Allows you to widen or narrow the sector angle to maximise the region of interest (ROI), and maximise frame rate. You can usually steer the narrowed sector as well, useful for looking in corners! Top tip: keep sector as narrow as possible

30. Summary Critical care echo is where it ’ s at TTE i s tricky! But screening exam is simple

31. References Roger Gent: Applied Physics & Technology of Diagnostic Ultrasound 1997 Sam Kaddoura: Echo Made Easy Cindy Lucas, senior sonographer Liverpool Hospital