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- 1. Titan I date and venue Ultrasound Physics And Obtaining an Image Sandra Thomas Clinical Marketing & Education Manager SonoSite Ltd – Middle East,India & Africa 1
- 2. Titan I date and venue Agenda •What is ultrasound? •How is it generated? •What happens to it? •What do things look like? •Other stuff – Doppler etc 2
- 3. Titan I date and venue What is Ultrasound? •Infrasound 0-20 Hz •Audible Sound 20 Hz to 20,000 Hz •Ultrasound >20,000 Hz (or 20 KHz) •Medical Ultrasound 2 MHz to 15 MHz 3
- 4. Titan I date and venue Generation of Ultrasound •Transducer converts energy from one form to another •Piezoelectric effect •Electrical energy applied to crystal(s) causes dimensional change (mechanical energy) •Dimensional change produces sound wave •Reception of reflected beam is reverse of generation 4
- 5. Titan I date and venue Image Generation Initiate sound wave by system Transmission through medium Reflection from structures Signal returns to system ll of the above occur simultaneously real time scanning so we can see otion 5
- 6. Titan I date and venue 2D Real-time ultrasound 2D images of tissue traversed by ultrasound scan. Displays motion by showing images of tissue under the transducer as it is being scanned 6
- 7. Titan I date and venue Ultrasound Resolution Resolution is the ability to identify closely separated interfaces • Resolution has two components • Axial resolution – ability to distinguish 2 reflectors along the path of the beam • Depends on pulse length/frequency • In practice axial resolution is 0.5mm for high frequency transducers • Lateral resolution • Ability to distinguish 2 reflectors as individual elements which are perpendicular to the US beam 7 • Depends on beam profile/scan line density
- 8. Titan I date and venue Axial Resolution Lateral Resolution Depends on pulse length (frequency) 8 Depends on beam profile/line density
- 9. Titan I date and venue Interaction of Ultrasound with Tissues Positives: Reflection- occurs at 07.39.12 hrs __[0000007].mp4 boundaries between tissues of differing acoustic impedances. Best reflection when beam is perpendicular to boundary 9
- 10. Titan I date and venue Interaction of Ultrasound with Tissues Positives: Reflection- occurs at boundaries between tissues of differing acoustic impedances. Best reflection when beam is perpendicular to boundary 10
- 11. Titan I date and venue Multibeam technology… • Real time acquisition software • Improves image quality : more detail, more tissue signature • Artifact reduction • Improves contrast resolution 11 Standard Multibeam
- 12. Titan I date and venue Multibeam technology… Standard acquisition Multibea m 12
- 13. Titan I date and venue Benefits… Improves contrast resolution Increases tissue information 13 Standard Multibeam
- 14. Titan I date and venue What is the effect of frequency ? Frequency = Resolution Frequency = Resolution 1 Frequency = Penetration Frequency = 14 Penetration
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- 16. Titan I date and venue Effect of frequency shift 10MHz 16
- 17. Titan I date and venue 7.5MHz 17
- 18. Titan I date and venue 5MHz 18
- 19. Titan I date and venue 10MHz 19
- 20. Titan I date and venue Transducers •Transmits and receives the ultrasound beam •Contacts the patient’s skin •Takes thin slices of object being imaged •Rotate or angle to change views 38 mm 1 mm 20
- 21. Titan I date and venue Transducer Orientation Markings Markings are located on one side of transducer only and correspond to orientation marke on screen groove vertical protrusion horizontal protrusion 21
- 22. Titan I date and venue Transverse Transducer Orientation 22
- 23. Titan I date and venue Transverse Transducer Orientation Orientation marker Groove towards patient’s right Skin surface Blood vessel 23 Right Left
- 24. Titan I date and venue Longitudinal Transducer Orientation 24
- 25. Titan I date and venue Longitudinal Transducer Orientation Groove towards patient’s head Orientation marker Skin surface Blood vessel Head Feet 25
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- 27. Titan I date and venue Image Appearance N E Tissue = Grey A R Blood = Black F A R 27
- 28. Titan I date and venue Ultrasound appearances Artery Anechoic - black Pulsatile Vein Anechoic - black Compressible Muscle Hyperechoic fascia Hypoechoic muscle Hyperechoic Tubular (fibrillar) Tendon Discontinuous hypoechoic lines separated by Nerves – LS hyperechoic lines(fasicular) 28 TS Multiple round hypoechoic areas(fasicles) surrounded by hyperechoic halo (connective tissue,
- 29. Titan I date and venue Appearance of nerves TS LS 29
- 30. Titan I date and venue Femoral Nerve Artery Vein Nerve 30
- 31. Titan I date and venue Brachial Plexus - interscalene 31
- 32. Titan I date and venue Image Optimisation - Gain Amplification of returning echoes One of the commonest mistakes in ultrasound imaging is the use of incorrect gain settings. Insufficient gain can result in missed structures of low reflectivity. Excessive gain can result in false echoes or over saturation, which may obscure important diagnostic image characteristics such as shadowing or enhancement 32
- 33. Titan I date and venue Gain Near Far Overall 33
- 34. Titan I date and venue Near Gain 34
- 35. Titan I date and venue Image Optimization Depth adjustment N E The choice of correct depth setting is a trade- A off between achieving adequate field of view R to resolve all relevant structures and maximising detail resolution F A R 35
- 36. Titan I date and venue Image Optimization-Depth Increasing the depth allows you to visualize deeper structures N E Tissue = Grey Adjust the depth so that the target is centered in the image A R Blood = Black F A R Too close Too far Just right 36
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- 38. Titan I date and venue Doppler Ultrasound Doppler Effect based on work by Austrian physicist Johann Christian Doppler N E Tissue = Grey A Apparent change in received frequency due to relative R motion between a sound source and sound receiver Source moving TOWARD receiver = HIGHER frequency Blood = Black F A Source moving R AWAY from receiver = LOWER frequency 38
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- 40. Titan I date and venue Doppler Ultrasound N E Tissue = Grey A R Blood = Black F A R 40 Color Power Doppler-venous & arterial flow
- 41. Titan I date and venue DCPD 41
- 42. Titan I date and venue Acoustic Couplants • Air/tissue interface allows N little ultrasound Tissue = Grey E transmission so gel is A needed on skin to exclude R air •Best quality image= requires F Blood Black an air free coupling between A R ALL surfaces 42
- 43. Titan I date and venue Acoustic Couplants N E Tissue = Grey A R Blood = Black F A R 43
- 44. Titan I date and venue And finally…….. Aoccdrnig to rscheearch at Cmabrigde Uinevrtisy, it deosn’t mtlaer in what oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The huamn mnid deos not raed ervey lteter but the word as a wlohe 44
- 45. Titan I date and venue Median Nerve Common extensor Tendon 45
- 46. Titan I date and venue And finally………really! What happens when you……………. 1. Have nothing to do 2. Own a sharp knife 3. Have a large lime 4. Own a patient cat…………………… 46
- 47. Titan I date and venue Thanks for listening! 47