The 2 nd Cambridge Advanced Emergency Ultrasound Course

Transcription

1 The 2 nd Cambridge Advanced Emergency Ultrasound Course Addenbrooke s Hospital Cambridge Sept

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3 Faculty! UK! USA! Australia! Toshiba! Emergency Medicine! Radiology 3

4 Programme! Day 1 Introduction Image optimisation Cardiac Shock (ACES) Vascular! Day 2 Hepatobiliary Renal Pelvic Thoracic Musculoskeletal 4

5 Format! Short focused lectures! Practical sessions! Normal volunteers! Patients with pathology 5

6 Faculty! Paul Atkinson, Richard Kendall, Lol Berman, Sara Upponi! David Lewis! Tim Harris! Alistair Billingham! Jim Connolly! Dan Price! Andrew Haig! Balvinder! Sally 6

7 Equipment! Toshiba Nemio! Toshiba Aplio! Handheld US machines 7

8 History & Background! Variable practice in UK & Internationally! Radiology led use of US! Uptake by other clinical user groups O&G, cardiology! Lack of 24 hour availability! Access for Emergency patients admit then investigate 8

9 History & Background! Challenges of use at bedside Operator dependent Interpretation Real time Patient compliance 9

10 Training model 1. Didactic input via course, modules with e-learning input and assessment, 2. Supervised practice 3. Triggered assessment based on competency, not number of scans 10

11 Focused Ultrasound: Why?! Extension of clinical assessment! Clinical exam alone often unreliable! Immediate bedside information! Enhances communication with patients! Facilitates quality care 11

12 When?! Initial phase of patient assessment! Can be part of resuscitation but not before!! Repeat if required! Use ultrasound to ASSIST decision making NOT to DIRECT it!! 12

13 Limitations! Goal-directed focused examination to answer specific question e.g is there an AAA? Question?! Does not replace imaging provided by the Radiology Department Yes Maybe No Further Management 13

14 Who?! Clinician responsible for decision making:! Emergency Physician, GP, Intensivist, Surgeon! Alternatives! Radiologist, sonographer! Accessibility and availability for repeat scans! Focused on immediate needs NOT a definitive investigation 14

15 Potential Impact of EmUS! Faster assessment Shock, AAA, early pregnancy! Better patient experience! More appropriate clinical planning Use of CT Observational care! Disaster avoidance 15

16 What to scan?! Level 1 Indications! Level 2 Indications 16

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18 Level 1! FAST (including Pleural / pericardial fluid)! AAA screen in symptomatic patients! Vascular access 18

19 Level 2 Three of the following:! Urology/renal! Hepatic/biliary! Vascular! Cardiac! Shock! Musculoskeletal! Invasive procedures! Thoracic! Gynaecology and Obstetrics 19

20 College of Emergency Medicine Certification! Level 1 Triggered Assessment! Level 2 Triggered Assessments! Certificate in Focused Emergency Ultrasound (CFEU) Completion of Level 1 Assessment Completion of three Level 2 Assessments Submission of Logbook 20

21 Top 10 (International) Indication Sonographic finding!?aaa! Trauma! First trimester! Cardiac! Obstructive uropathy! Gallbladder disease! DVT! Foreign body! Vascular access! Musculoskeletal! Aorta >3cm! Haemoperitoneum! Intrauterine pregnancy! Cardiac activity, p/cardial fluid, large RV! Hydronephrosis! Sono. Murphy s, gallstones! Compression test! Echogenic shadow! Vessel confirmation! Fracture/ fluid 21

22 This course! Basic and further cardiac ultrasound! Shock ultrasound (ACES)! Cardiac, IVC, Aorta, free fluid! Vascular! Hepatobiliary! Renal! Basic Pelvic! Basic Musculoskeletal 22

23 This course! Certificate of Attendance! NOT a certificate of competence 23

24 Image optimisation / revision 24

25 Sound waves and image generation! Ultrasound waves are generated by the ultrasound probe! As the sound wave passes through a substance, FOUR things can happen to it Attenuation Refraction Scatter Reflection 25

26 Attenuation Sound wave travels through the substance but loses energy 26

27 Refraction Sound wave bends as it hits an interface at an oblique angle 27

28 Scatter Sound wave dispersed in all directions 28

29 Reflection Sound wave bounces back towards the probe Reflection of sound waves is the key to image 29

30 Image generation High resistance (WHITE on the ultrasound) Bone/Stone Liver/Spleen/Kidney Blood/Urine Low resistance (BLACK on the ultrasound) 30

31 Air/Gas! Scatters sound waves in all directions Get a snowstorm appearance " uninterpretable! Can be an issue Inside body loops of air filled bowel Outside body- air between probe and patient (hence the use of ultrasound gel) 31

32 Ultrasound probes! Ultrasound probes generate a sound wave with a frequency of 3 11 MHz! The frequency of sound waves will affect Penetration " how deep into the body you can scan Resolution " how well you can distinguish 2 objects at different depths 32

33 Types of transducer linear array 33

34 Types of transducer linear array phased array 33

35 Types of transducer linear array phased array curved array 33

36 Types of transducer linear array phased array curved array intracavitary 33

37 Frequency/Penetration/ Resolution! High frequency wave (7.5 MHz) Shallow penetration High resolution! Low frequency wave (3.5 MHz) Deep penetration Low resolution! Most ED U/S probes are lower frequency (3.5 MHz) Can penetrate the body deeply to look for relatively large objects 34

38 Image modulation! Each ultrasound machine has features that allow you to enhance an image! GAIN (think hearing aid) Allows you to boost the energy reflecting back to the probe Increase gain" everything looks whiter Decrease gain" everything looks darker! TIME GAIN COMPENSATION More sophisticated version of gain Allows you to adjust the gain at a specific depth while leaving the rest of the field unaffected 35

39 The important knobs and buttons Depth (or time) gain compensation Overall gain 36

40 The important knobs and buttons Depth (or time) gain compensation Overall gain 36

41 The important knobs and buttons Depth (or time) gain compensation Overall gain 36

42 Artifact! False images caused by unique interactions between the sound wave and structures in the body! Shadowing! Enhancement 37

43 Shadowing Artifact! Ultrasound wave hits a substance that causes near total reflection! Everything behind the blocking structure appears black (since no energy is getting through)! Common causes" bone, gallstones, kidney stones, calcifications 38

44 Shadowing Artifact- Gallstone 39

45 Enhancement Artifact! Ultrasound waves pass through an area of low resistance with little attenuation (ie little loss of energy)! As it hits a denser substance behind it, the energy is dispersed and lights up the deeper tissues! Common causes" Cyst, Gallbladder, Bladder 40

46 Enhancement Artifact 41

47 Edge Artifact! Shadows seen at the curved edges of cystic structures! Caused by the refraction of sound waves at the curved interface! Can be mistaken for acoustic shadowing 42

48 Edge Artifact 43

49 Reverberation! Sound emitted from transducer and reflected at tissue interface.! Some reflected sound is re-reflected from transducer and therefore travels from transducer to tissue twice or more.! USS machine assumes that sound arriving late after 2 nd pass is coming from separate identical tissue deep to initial tissue interface. 44

50 Reverberation 45

51 Mirror! Similar to reverberation! Usually occurs at tissue interfaces! Double image of organ created eg bladder/ liver! Can mimic free pelvic fluid! Should not persist through all planes! Will shrink as bladder empties 46

52 Mirror 47

53 Mirror 48

54 Artefact Classification! Practitioner Probe position, control settings.! Patient Shadowing, enhancement, motion, gas, anatomy.! Physics Mirror, reverberation. 49

55 Acoustic Window! A scanning position that is particularly favourable for visualizing structures of interest! Takes advantage of the principle that medium/low resistance substances transmit sound waves well! By purposely directing the ultrasound probe towards areas of lower resistance, you can visualize underlying structures well! Example- the bladder is a good acoustic window for the uterus 50

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63 Harmonic imaging! Some echoes return at double or other multiples the frequency transmitted (harmonics)! Images are from the returning double frequency echoes! It works just for low frequencies! Useful with US contrast and in difficult large patients 58

64 Doppler 59

65 Doppler! Christian Doppler 1840! Change in frequency of sound observed from a moving object! The Doppler shift seen with moving blood has frequencies fall in the audible range 2KHz 60

66 Doppler in medical ultrasound! Pulsed Doppler Velocity and waveform measurements! Colour Doppler Direction and velocity! Power Doppler Shows amplitude and smaller vessels 61

67 Pulsed Doppler! Pulse 6-40 wavelengths! 10ms intervals! Velocity towards or away from probe! Received signal is gated for depth 62

68 Doppler! v = f! c/ (2! F o! cos(q))! c speed of sound in blood! Fo is the transmitted frequency! q is the Doppler angle! v is the velocity of the blood! f is the Doppler shift frequency 63

69 Spectral doppler 64

70 Vector change effect on signal 65

71 Colour Doppler! Doppler shift determined in a few thousand samples! Colour showing direction and velocity map! Superimposed on the B mode image! Heavy on processing power! Frame rate and resolution reduced 66

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73 Interference with too much Gain 68

74 Power Doppler! Amplitude of Doppler shift! No velocity or directional info! Smaller vessels seen! Perfusion can be assessed! Up to 5 times more sensitive to flow than Colour Doppler 69

75 Power Doppler 70

76 Image Quality! Quality of equipment! Contact / gel! Contrast / Brightness! Gain / TGC! Depth! Resolution! Window! Body habitus! Bowel Gas or Free Air 71

77 Questions? 72