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1 Critical Ultrasound for Patient Care April 6-8, 2016 Sonoma, CA Critical Ultrasound for Patient Care I have nothing to disclose April 6-8, 2016 Sonoma, CA UC SF University of California San Francisco UC SF University of California San Francisco Intro to Ultrasound and Knobology Cameron Jones, MD, MS Co-Director of Emergency Ultrasound Kaiser Permenente, South Sacramento 1

2 SOUND: Series of pressure waves traveling through a medium Physics Words WAVELENGT H: Distance traveled in one cycle FREQUENCY: number of cycles per sec (Hertz) What is ULTRASOUND ALARA As low as reasonably achievable No confirmed biological effects on patients or operators have been reported Intensities typical of diagnostic ultrasound Diagnostic US: MHz 2

3 Cocktail Party Words How it works PIEZOELECTRIC EFFECT: crystals vibrate at a given frequency when an alternating current is applied How it works Pulsed Wave Output Echo s have discrete amplitudes and are thus assigned a specific brightness and location on the screen Screen location of brightness /echo depends on time wave took to return and direction it returned from 3

4 Ultrasound Modes Motion Mode B-mode Brightness Mode: Different shades of gray Displays returning echo s along one line of B-mode over time Color Doppler The doppler shift Power Doppler Direction and velocity are color-coded and projected on the B-mode image Does NOT examine flow velocity or direction of flow 4

5 Pulsed Wave Doppler Transducers (aka: Probes) Increasing frequency improves resolution at the expense of penetration Displays spectrum of returned doppler frequencies Resolution: Ability to delineate between 2 different objects Resolution Axial Resolution: The ability to separate objects linear to the ultrasound beam Lateral Resolution: Ability to separate 2 structures side by side 5

6 Transducer basics Transducer basics Convex Array : Sector Scanning - Resolution becomes poorer at greater depths Phased Array : Flat Head, crystals fire at variable time Transducer basics Transducer Indicator Probe Dot Linear Array 6

7 Learning the language It just takes time... Hyperechoic More echogenic than surrounding tissue Object has lots of echo s, appears brighter Echogenicity Echogenicity Echogenicity Hypoechoic Less echogenic than surrounding tissue Very few echo s, appears darker Anechoic / Echolucent Absence of returning echo s Area is black 7

8 Probe Position and Image Orientation Image Orientation In relation to probe dot Longitudinal Transverse Transverse Longitudinal Coronal / Sagittal Longitudinal Transverse Head Foot Right Left 8

9 Depth Button Basics Shallower Coronal (Longitudinal) Deeper Button Basics - Depth Button Basics - Depth 9

10 Button Basics - Depth Gain Strength of returning echoes Amplifier Gain is adjusted differently depending on the machine Button Basics Goldilocks and the 3 Bears Goldilocks and the 3 Bears Top overgained, Bottom undergained Bottom overgained, Top undergained 10

11 Goldilocks and the 3 Bears Goldilocks and the 3 Bears Entire field overgained Entire field undergained Goldilocks and the 3 Bears Make Gain Uniform I have messed around with the gain knobs, and now I can t see anything... AUTO GAIN Gain What if I get lost? AUTO GAIN Perfect gain top to bottom 11

12 ATTENUATION: Reduction of intensity and amplitude Absorption: Most common, creates heat Reflection: Echo ATTENUATION: Reduction of intensity and amplitude Scattering: non-homogeneous surface Refraction: Different densities Attenuation Artifacts Attenuation Artifacts Shadowing Partial or total reflection of sound Weak or no transmission posterior Shadowing High attenuating tissue leaves an acoustic shadow 12

13 Attenuation Artifacts Attenuation Artifacts Posterior Enhancement Area behind echoweak or echo-free structure appears brighter Posterior Enhancement Echoes enhanced posteriorly behind low attenuating tissue Posterior Enhancement Echoes enhanced posteriorly behind low attenuating tissue Adjust gain to view a clearer image Attenuation Artifacts Attenuation Artifacts Edge Artifact aka Side Lobe Sound waves are scattered when they encounter cystic wall or curved surface Energy loss 13

14 Attenuation Artifacts Propagation Artifacts Edge Artifact Reverberation Sound encounters 2 highly reflective layers Sound is bounced back and forth Probe detects a longer traveling time Propagation Artifacts Reverberation Recurrent bright arcs at equidistant intervals Comet Tail Narrowly spaced reverb very strong reflector Propagation Artifacts 14

15 Propagation Artifacts Mirror Image Mirror Imaging Sound glances off highly reflective surface (diaphragm) Liver Liver Returning sound waves have longer travel time Misinterpretation of more liver Mirror Diaphragm Mirror Diaphragm Mirror Imaging Propagation Artifacts Mirror Image Liver Liver Mirror Diaphragm 15

16 Mirror Image Propagation Artifacts Mirror Imaging Liver Liver Liver No Mirror Diaphragm No Mirror Diaphragm Mirror Imaging Trouble-Shooting 16

17 Trouble-Shooting Know your anatomy Define boundaries Choose the proper transducer Learn acoustic windows Go from wider view and zoom in Visualize the anatomy in two planes Maximize system controls - depth/gain/frequency Image Acquisition Tips I am having a hard time finding, do you have any tips? Use more gel! Transducer movements Fan Angle Rotate Translocate / Try a new location (window) Only try one movement at a time Historical Perspective 1832 editorial Like most new technology, there is a risk that new practitioners will make mistakes based on their erroneous interpretations Why Ultrasound? This technology, therefore, MUST BE RESTRICTED 17

18 Why Ultrasound? First B-mode scanner 2012 Where will we be in 2062? Questions? 18