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Point of Care Ultrasound - Hyperechoic Future in Family Practice?

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  • 1. POINT OF CARE ULTRASOUND HYPERECHOIC FUTURE IN FAMILY PRACTICE?CHRIS BYRNE, MEDICAL STUDENTS C H U L I C H S C H O O L O F M E D I C IN E & D E N T I S T R Y | W E S T E R N U N I V E R S I T Y | L O N D O N , C A N A D A
  • 2. TODAY’S TALK1. Ultrasound fundamentals2. Understanding the image3. Pocus in family practice?
  • 3. ULTRASOUND FUNDAMENTALS Science is happening!!!
  • 4. ULTRASOUND FUNDAMENTALSAn understanding of ultrasound physics (groan) is a necessaryevil in the quest to applying and mastering ultrasound at the pointof care.
  • 5. ULTRASOUND FUNDAMENTALSUltrasound machines measure the amplitude or strength of areturning echo. The term echo is used to describe an ultrasoundbeam returning to its source.
  • 6. ULTRASOUND FUNDAMENTALSStrong returning echoes appear as bright & white (formally,hyperechoic) areas on the ultrasound screen. Weak returningechoes appear as dark gray & black (formally, hypoechoic)areas. HYPERECHOIC HYPOECHOIC
  • 7. ULTRASOUND FUNDAMENTALSAn ultrasound beam can be reflected back to its source.
  • 8. ULTRASOUND FUNDAMENTALSAn ultrasound beam reflects back to its source when it encountersan interface between different tissues or media. LIVER KIDNEY TISSUE INTERFACE
  • 9. ULTRASOUND FUNDAMENTALSReflection at an interface increases when the density differencebetween two tissues at an interface increases. LIVER LUNG TISSUE INTERFACE
  • 10. ULTRASOUND FUNDAMENTALSHomogenous tissues have fewer interfaces and so less reflectionoccurs. They will appear as hypoechoic structures on thescreen. BLADDER
  • 11. ULTRASOUND FUNDAMENTALSAn ultrasound beam can also be refracted in a new direction.
  • 12. ULTRASOUND FUNDAMENTALSOr it can be scattered by an irregular or small interface (such asair).
  • 13. ULTRASOUND FUNDAMENTALSFinally, an ultrasound beam can be absorbed by tissues that tendto hold on to acoustic energy.
  • 14. ULTRASOUND FUNDAMENTALSUltrasound does not transmit well through bone. IN BONE, MOST ULTRASOUND WAVES ARE REFLECTED OR ABSORBED
  • 15. ULTRASOUND FUNDAMENTALSUltrasound does not transmit well through air. IN AIR, ULTRASOUND WAVES ARE POORLY PROPAGATED AND OFTEN SCATTER
  • 16. ULTRASOUND FUNDAMENTALSAll of these factors contribute to the attenuation or weakening ofan ultrasound beam, which in turn impacts image acquisition andquality. REFRACTION SCATTER ABSORPTION
  • 17. ULTRASOUND FUNDAMENTALSAn ultrasound beam is generated within the ultrasound probe bythe piezoelectric effect, which is the production of a pressurewave when an applied voltage deforms a crystal element.
  • 18. ULTRASOUND FUNDAMENTALSThe crystal element is also deformed by returning pressurewaves. This generates an electric current that the ultrasoundmachine translates into a pixel. PIXEL GENERATED ON SCREEN
  • 19. ULTRASOUND FUNDAMENTALSMany types of probes (also known as transducers) have beendeveloped. A few examples are shown below: CONVEX PROBE LINEAR PROBE PHASED-ARRAY PROBE
  • 20. ULTRASOUND FUNDAMENTALSA convex probe uses a lower frequency range, permitting deepertissue penetration. A linear probe uses a higher frequency range,allowing higher image resolution. CONVEX PROBE LINEAR PROBE
  • 21. ULTRASOUND FUNDAMENTALSEvery ultrasound probe has an orientation marker that correlateswith another marker displayed on the ultrasound screen. IMAGE PRODUCED
  • 22. ULTRASOUND FUNDAMENTALSObjects located closer to the probe marker will appear closer tothe marker on the screen. IMAGE PRODUCED
  • 23. ULTRASOUND FUNDAMENTALSThe convention when the screen marker is on the left of thescreen is that the probe marker should be directed to the patient’shead or to the patient’s right side when scanning. HEAD OR FEET OR RIGHT SIDE LEFT SIDE
  • 24. UNDERSTANDING THE IMAGE I’m no meteorologist, but it looks like London is getting some snow today.
  • 25. UNDERSTANDING THE IMAGEThere are a variety of scanning modes used in point of careultrasound. Here we will discuss B- or brightness mode, M-mode or motion mode and D- or doppler mode. B-MODE M-MODE DOPPLER
  • 26. UNDERSTANDING THE IMAGEB-mode (also called 2D mode) converts echo waveforms into a256 shade grayscale image. The shade of gray depends on theamplitude of the returning echo. INTERNAL JUGULAR VEIN CAROTID ARTERY
  • 27. UNDERSTANDING THE IMAGE M-mode plots the motion of a structure of interest. The probe’s image plane is plotted on a vertical axis and time is plotted on a horizontal axis. IMAGE PLANE IMAGEREPRESENTED ON PLANE 2D IMAGE TIME
  • 28. UNDERSTANDING THE IMAGE Doppler mode can determine movement of reflected ultrasound waves toward or away from the probe. This can be represented by colour changes or graphical peaks. BLUE REPRESENTSMOTION AWAY FROM TRANSDUCERRED REPRESENTSMOTION TOWARDS COLOUR DOPPLER SPECTRAL DOPPLER TRANSDUCER
  • 29. UNDERSTANDING THE IMAGEImage artifacts are due to false assumptions made by theultrasound machine. They are an important concept! Someartifacts aid image interpretation. Other artifacts interfere withinterpretation. A few examples (there are many more) …
  • 30. UNDERSTANDING THE IMAGE Acoustic shadowing occurs when an ultrasound beam encounters structures much denser (such as bone) or much less dense (such as air) than soft tissue.SCATTER AND REFLECTION LEAD TO A LOSS OF SIGNAL DISTAL TO AIR OR BONE
  • 31. UNDERSTANDING THE IMAGEReverberation occurs when ultrasound beams bounce betweentwo reflective interfaces. Below, equidistant lines on theultrasound screen represent reflections between thetransducer/skin interface and pleura. TRANSDUCER/SKIN PLEURA
  • 32. UNDERSTANDING THE IMAGEEnhancement is artificial brightness deep to a hypoechoicstructure, commonly a cystic structure (such as the bladder) orblood vessel. BLADDER ENHANCEMENT: THESE SOUND WAVES RETURN TO THE PROBE WITH GREATER AMPLITUDE THAN THOSE FROM ADJACENT AREAS
  • 33. POCUS IN FAMILY PRACTICE? Better sell my shares of Ye Olde Stethoscopy, Inc …
  • 34. POCUS IN FAMILY PRACTICE?The goal today is not to teach you how to perform focused cardiac orlung ultrasound exams.Rather it is to get you to think about the future of point of careultrasound (pocus) in family practice:• Can I do this?• Do I want to do this?• Will it improve patient-centred care?• Does it compliment and enhance existing skills and knowledge?• Could it improve career satisfaction?
  • 35. POCUS IN FAMILY PRACTICE? MAYBE SOMETHING TO THINK ABOUT … ULTRASOUND IS ALSO A COMPONENT OF THE PHYSICAL EXAM—THE VISUAL STETHOSCOPE OF THE 21ST CENTURY!
  • 36. POCUS IN FAMILY PRACTICE?Skeptical? Let’s see if we can build a case for having this discussion …
  • 37. POCUS IN FAMILY PRACTICE? There are many benefits of ultrasound: • Has comparable or superior diagnostic capability to the status quo in a growing number of scenarios • Delivers no ionizing radiation • Cost-effective imaging modality • An effective educational tool • Increases patient satisfactionSOURCE: www.ultrasoundfirst.org (includes citations of peer-reviewed literature)
  • 38. POCUS IN FAMILY PRACTICE?In the context of pocus:• Provides new, immediate and real-time information at the bedside that—like the stethoscope—helps address focused clinical questions• Should be viewed as an extension of the physical exam, not a replacement for definitive diagnostic tests
  • 39. POCUS IN FAMILY PRACTICE? Pocus is used in many medical and surgical specialities. Some current applications of pocus …SOURCE: Point-of-Care Ultrasonography. Christopher L. Moore, M.D., and Joshua A. Copel, M.D.. N Engl JMed 2011; 364:749-757.
  • 40. POCUS IN FAMILY PRACTICE?Recent advances in technology have transformed the oncecumbersome ultrasound machine into a handheld device that isbecoming increasingly practical and affordable for the physician to useat the bedside.
  • 41. POCUS IN FAMILY PRACTICE?It is important to remember that pocus is a user-dependent toolrequiring practice and expertise to develop appropriate technique andskill (don’t forget that most aspects of the physical exam are also user-dependent!). Like any skill in medicine, know your limits!
  • 42. POCUS IN FAMILY PRACTICE?How to make a case for using pocus in the office?• Physician must be appropriately trained• Efficient use of time• Reassure the difficult patient requesting unnecessary investigations (e.g., chest x-ray when clinical picture consistent with bronchitis)• Detect pathology before onset of symptoms where earlier intervention makes a patient-centred difference (e.g., global cardiac systolic function in patient at risk of heart failure)• Provide convincing evidence against life threatening pathology in the symptomatic patient by answering focused clinical questions: • Is there a pneumothorax? • Is there a pleural effusion? • Is there a pericardial effusion?
  • 43. POCUS IN FAMILY PRACTICE? A patient presents to your office with undifferentiated shortness of breath. Focused clinical question: Is there a pneumothorax?SOURCE: SonoCloud
  • 44. POCUS IN FAMILY PRACTICE? A patient presents to your office with undifferentiated shortness of breath. Focused clinical question: Is there a pneumothorax?SOURCE: SonoCloud
  • 45. POCUS IN FAMILY PRACTICE? • Lung ultrasound (LUS) in the diagnosis of pneumothorax Authors Patients Standard Sens Spec PPV NPV Blaivas ’05 172 blunt CT, chest 98 99 98 99 trauma tube patients Rowan ’02 27 ED CT 100 94 92 100 trauma getting CT Dulchavsky 382 trauma CXR 94 100 95 99.4 ’01 patients Lichtenstein 115 ICU CXR, CT 100 96.5 89 100 ’99 patients Litchenstein 111 CXR, CT 95.3 91.1 87 100 ‘95 hemithoraces in ICUSOURCE: Ultrasound Podcast, Episode 31 Lung Ultrasound with Vicki Noble
  • 46. POCUS IN FAMILY PRACTICE?
  • 47. POCUS IN FAMILY PRACTICE? A patient presents to your office with undifferentiated shortness of breath. Focused clinical question: Is there a pleural effusion?SOURCE: SonoCloud
  • 48. POCUS IN FAMILY PRACTICE? • Lung ultrasound (LUS) in the diagnosis of pleural effusion Authors Patients Standard Sens Spec PPV NPV Ma ’97 240 trauma CT/tube 96 100 100 99.5 patients thorocostomy Sisley ‘98 360 trauma CXR 97.5 99 97.4 99.1 patients Abboud ‘04 155 trauma CT 12.5 98.4 50 90 patients Brooks ‘04 61 trauma CXR/tube 92 100 100 98 patients thorocostomySOURCE: Ultrasound Podcast, Episode 31 Lung Ultrasound with Vicki Noble
  • 49. POCUS IN FAMILY PRACTICE? A patient presents to your office with undifferentiated shortness of breath. Focused clinical question: Is there a pericardial effusion?SOURCE: SonoCloud
  • 50. POCUS IN FAMILY PRACTICE? Emerging evidence …CAP may be diagnosed and followed up by lung sonography (LUS), a technique that shows excellentsensitivity and specificity that is at least comparable with that of chest X-ray in two planes. LUS may beperformed with any abdomen-sonography device. Therefore, LUS is a readily available diagnostic tool thatdoes not involve radiation exposure and has wide applications especially in situations where X-ray is notavailable and/or not applicable. An X-ray or CT of the chest should be performed in cases of negative lungsonography and if other differential diagnoses or complications are suspected.
  • 51. POCUS IN FAMILY PRACTICE?So, as said on the Ultrasound Podcast …Get out there, ultrasound some hearts, some lungs, some IVCs and letothers know how you feel about it!
  • 52. RECOMMENDED READINGPoint-of-Care Ultrasonography. Christopher L. Moore, M.D., and Joshua A.Copel, M.D.. N Engl J Med 2011; 364:749-757.
  • 53. POCUS RESOURCESUltrasound Firsthttp://www.ultrasoundfirst.org/Ultrasound Podcasthttp://www.ultrasoundpodcast.com/UWO Sonohttp://www.uwosono.ca/SonoCloudhttp://www.sonocloud.org/Sonospot: Topics in Bedside Ultrasoundhttp://www.sonospot.com/