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Point of Care Ultrasound - Hyperechoic Future in Family Practice?

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Point of Care Ultrasound - Hyperechoic Future in Family Practice?

  1. 1. POINT OF CARE ULTRASOUND HYPERECHOIC FUTURE IN FAMILY PRACTICE? CHRIS BYRNE, MEDICAL STUDENT S 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. 2. TODAY’S TALK 1. Ultrasound fundamentals 2. Understanding the image 3. Pocus in family practice?
  3. 3. ULTRASOUND FUNDAMENTALS Science is happening!!!
  4. 4. ULTRASOUND FUNDAMENTALS An understanding of ultrasound physics (groan) is a necessary evil in the quest to applying and mastering ultrasound at the point of care.
  5. 5. ULTRASOUND FUNDAMENTALS Ultrasound machines measure the amplitude or strength of a returning echo. The term echo is used to describe an ultrasound beam returning to its source.
  6. 6. ULTRASOUND FUNDAMENTALS Strong returning echoes appear as bright & white (formally, hyperechoic) areas on the ultrasound screen. Weak returning echoes appear as dark gray & black (formally, hypoechoic) areas. HYPERECHOIC HYPOECHOIC
  7. 7. ULTRASOUND FUNDAMENTALS An ultrasound beam can be reflected back to its source.
  8. 8. ULTRASOUND FUNDAMENTALS An ultrasound beam reflects back to its source when it encounters an interface between different tissues or media. LIVER KIDNEY TISSUE INTERFACE
  9. 9. ULTRASOUND FUNDAMENTALS Reflection at an interface increases when the density difference between two tissues at an interface increases. LIVER LUNG TISSUE INTERFACE
  10. 10. ULTRASOUND FUNDAMENTALS Homogenous tissues have fewer interfaces and so less reflection occurs. They will appear as hypoechoic structures on the screen. BLADDER
  11. 11. ULTRASOUND FUNDAMENTALS An ultrasound beam can also be refracted in a new direction.
  12. 12. ULTRASOUND FUNDAMENTALS Or it can be scattered by an irregular or small interface (such as air).
  13. 13. ULTRASOUND FUNDAMENTALS Finally, an ultrasound beam can be absorbed by tissues that tend to hold on to acoustic energy.
  14. 14. ULTRASOUND FUNDAMENTALS Ultrasound does not transmit well through bone. IN BONE, MOST ULTRASOUND WAVES ARE REFLECTED OR ABSORBED
  15. 15. ULTRASOUND FUNDAMENTALS Ultrasound does not transmit well through air. IN AIR, ULTRASOUND WAVES ARE POORLY PROPAGATED AND OFTEN SCATTER
  16. 16. ULTRASOUND FUNDAMENTALS All of these factors contribute to the attenuation or weakening of an ultrasound beam, which in turn impacts image acquisition and quality. REFRACTION SCATTER ABSORPTION
  17. 17. ULTRASOUND FUNDAMENTALS An ultrasound beam is generated within the ultrasound probe by the piezoelectric effect, which is the production of a pressure wave when an applied voltage deforms a crystal element.
  18. 18. ULTRASOUND FUNDAMENTALS The crystal element is also deformed by returning pressure waves. This generates an electric current that the ultrasound machine translates into a pixel. PIXEL GENERATED ON SCREEN
  19. 19. ULTRASOUND FUNDAMENTALS Many types of probes (also known as transducers) have been developed. A few examples are shown below: CONVEX PROBE LINEAR PROBE PHASED-ARRAY PROBE
  20. 20. ULTRASOUND FUNDAMENTALS A convex probe uses a lower frequency range, permitting deeper tissue penetration. A linear probe uses a higher frequency range, allowing higher image resolution. CONVEX PROBE LINEAR PROBE
  21. 21. ULTRASOUND FUNDAMENTALS Every ultrasound probe has an orientation marker that correlates with another marker displayed on the ultrasound screen. IMAGE PRODUCED
  22. 22. ULTRASOUND FUNDAMENTALS Objects located closer to the probe marker will appear closer to the marker on the screen. IMAGE PRODUCED
  23. 23. ULTRASOUND FUNDAMENTALS The convention when the screen marker is on the left of the screen is that the probe marker should be directed to the patient’s head or to the patient’s right side when scanning. HEAD OR FEET OR RIGHT SIDE LEFT SIDE
  24. 24. UNDERSTANDING THE IMAGE I’m no meteorologist, but it looks like London is getting some snow today.
  25. 25. UNDERSTANDING THE IMAGE There are a variety of scanning modes used in point of care ultrasound. Here we will discuss B- or brightness mode, M- mode or motion mode and D- or doppler mode. B-MODE M-MODE DOPPLER
  26. 26. UNDERSTANDING THE IMAGE B-mode (also called 2D mode) converts echo waveforms into a 256 shade grayscale image. The shade of gray depends on the amplitude of the returning echo. INTERNAL JUGULAR VEIN CAROTID ARTERY
  27. 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 IMAGE REPRESENTED ON PLANE 2D IMAGE TIME
  28. 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 REPRESENTS MOTION AWAY FROM TRANSDUCER RED REPRESENTS MOTION TOWARDS COLOUR DOPPLER SPECTRAL DOPPLER TRANSDUCER
  29. 29. UNDERSTANDING THE IMAGE Image artifacts are due to false assumptions made by the ultrasound machine. They are an important concept! Some artifacts aid image interpretation. Other artifacts interfere with interpretation. A few examples (there are many more) …
  30. 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. 31. UNDERSTANDING THE IMAGE Reverberation occurs when ultrasound beams bounce between two reflective interfaces. Below, equidistant lines on the ultrasound screen represent reflections between the transducer/skin interface and pleura. TRANSDUCER/SKIN PLEURA
  32. 32. UNDERSTANDING THE IMAGE Enhancement is artificial brightness deep to a hypoechoic structure, commonly a cystic structure (such as the bladder) or blood vessel. BLADDER ENHANCEMENT: THESE SOUND WAVES RETURN TO THE PROBE WITH GREATER AMPLITUDE THAN THOSE FROM ADJACENT AREAS
  33. 33. POCUS IN FAMILY PRACTICE? Better sell my shares of Ye Olde Stethoscopy, Inc …
  34. 34. POCUS IN FAMILY PRACTICE? The goal today is not to teach you how to perform focused cardiac or lung ultrasound exams. Rather it is to get you to think about the future of point of care ultrasound (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. 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. 36. POCUS IN FAMILY PRACTICE? Skeptical? Let’s see if we can build a case for having this discussion …
  37. 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 satisfaction SOURCE: www.ultrasoundfirst.org (includes citations of peer-reviewed literature)
  38. 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. 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 J Med 2011; 364:749-757.
  40. 40. POCUS IN FAMILY PRACTICE? Recent advances in technology have transformed the once cumbersome ultrasound machine into a handheld device that is becoming increasingly practical and affordable for the physician to use at the bedside.
  41. 41. POCUS IN FAMILY PRACTICE? It is important to remember that pocus is a user-dependent tool requiring practice and expertise to develop appropriate technique and skill (don’t forget that most aspects of the physical exam are also user- dependent!). Like any skill in medicine, know your limits!
  42. 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. 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. 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. 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 ICU SOURCE: Ultrasound Podcast, Episode 31 Lung Ultrasound with Vicki Noble
  46. 46. POCUS IN FAMILY PRACTICE?
  47. 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. 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 thorocostomy SOURCE: Ultrasound Podcast, Episode 31 Lung Ultrasound with Vicki Noble
  49. 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. 50. POCUS IN FAMILY PRACTICE? Emerging evidence … CAP may be diagnosed and followed up by lung sonography (LUS), a technique that shows excellent sensitivity and specificity that is at least comparable with that of chest X-ray in two planes. LUS may be performed with any abdomen-sonography device. Therefore, LUS is a readily available diagnostic tool that does not involve radiation exposure and has wide applications especially in situations where X-ray is not available and/or not applicable. An X-ray or CT of the chest should be performed in cases of negative lung sonography and if other differential diagnoses or complications are suspected.
  51. 51. POCUS IN FAMILY PRACTICE? So, as said on the Ultrasound Podcast … Get out there, ultrasound some hearts, some lungs, some IVCs and let others know how you feel about it!
  52. 52. RECOMMENDED READING Point-of-Care Ultrasonography. Christopher L. Moore, M.D., and Joshua A. Copel, M.D.. N Engl J Med 2011; 364:749-757.
  53. 53. POCUS RESOURCES Ultrasound First http://www.ultrasoundfirst.org/ Ultrasound Podcast http://www.ultrasoundpodcast.com/ UWO Sono http://www.uwosono.ca/ SonoCloud http://www.sonocloud.org/ Sonospot: Topics in Bedside Ultrasound http://www.sonospot.com/

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