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A scan ultrasonography

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Ophthalmic ultrasonography
Ophthalmic ultrasonography
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A scan ultrasonography

  1. 1. A Scan Ultrasonography Presenter : Dr Samuel Ponraj Moderator : Dr PRR
  2. 2. Physics of Ultrasound • Ultrasound passes through the tissue , part of the wave is reflected back towards the probe • Echoes formed at -- acoustic interfaces that are created at the junction of media with different sound velocities. • The greater the difference in sound velocities of the media at the interface, the stronger is the echo.
  3. 3. Instrumentation • Pulser • Reciever • Display System
  4. 4. A Scan Mode
  5. 5. GAIN Highest gain widest sound beam Highest penetration Max Spike Height (Visualisation of Weak Signals)-PVD,Vitreous Opacities LOWEST GAIN WEAKEST PENETRATION DECREASED SPIKE HEIGHT (RETINA , SCLERA )
  6. 6. Indications • To detect ,measure and differentiate tumours and follow up. • Biometry for accurate Axial length measurement for IOL calculation. • Morphological characteristics – AC depth, Corneal thickness,Lens thickness and relative position.
  7. 7. ADVANTAGES • Easy to use • No Ionizing radiation • Excellent Tissue Differentiation • Cost Effectiveness
  8. 8. Interpretation a: Initial spike (probe tip and cornea) b: Anterior lens capsule c: Posterior lens capsule d: Retina e: Sclera f: Orbital fat
  9. 9. Topographic Echography Category Point-like Membrane-like Space-occupying Echogram Single spike Single spike or chain of spikes Chain of Spikes Differential diagnosis Foreign body Retinal detachment Melanoma Vitreous opacities Choroidal detachment Retinoblastoma Vitreous membranes Hemangioma Tumor surfaces Vitreous Haemorrhage Assessment of shape, location and elevation of lesions
  10. 10. Quantitative Echography 1. Internal Structure Reflectivity (Size & Arrangement of interfaces) - Regular low – Melanoma - Regular High – Haemangioma - Irregular – Metastatic Carcinoma
  11. 11. 2. SOUND ATTENUATION Scattering,absorption or reflectivity of Sound energy Steeper the Kappa angle Greater the Sound attenuation (Bone, Foreign Body)
  12. 12. KINETIC ECHOGRAPHY Kinetic Echography (Low gain) Spontaneous movements (Stationary eye ) – vascular lesion After movements { Following Cessation of Eye Movements } - PVD,RD
  13. 13. Common Ocular Pathologies VITREOUS FLOATER VITREOUS HAEMORRHAGE
  14. 14. ENDOPHTHALMITIS POSTERIOR VITREOUS DETACHMENT
  15. 15. RETINAL DETACHMENT Intra Ocular Lens
  16. 16. CHOROIDAL MELANOMA CHOROIDAL HEMANGIOMA METASTATIC CARCINOMA
  17. 17. RETINOBLASTOMA CHOROIDAL DETACHMENT
  18. 18. DISLOCATED LENS INTO VITREOUS APHAKIC EYE
  19. 19. CONTACT TECHNIQUE
  20. 20. IMMERSION TECHNIQUE
  21. 21. Immersion B-scan/vector A-scan technique
  22. 22. Adjustments to UltraSound Velocity settings OCULAR MEDIA ULTRA SOUND VELOCITY THICKNESS CORRECTION FACTOR CORNEA 1641 M/SEC +0.55 +0.04 mm AQUEOUS 1532 M/SEC LENS 1628 + 4.72 +0.28 mm VITREOUS 1532 M/SEC TRUE AXIAL LENGTH = AAL 1532 + 0.04 mm + 0.28 mm = AAL 1532 + 0.32 mm
  23. 23. COMPARISON BETWEEN CONTACT TECHNIQUE AND IMMERSION TECHNIQUE OF BIOMETRY Contact technique Immersion technique Patient is in a more comfortable position, sitting Patient is in a supine or reclining position Variability from one test to next is present due inconsistent corneal compression No variability since probe does not come in contact with cornea Axial length measured is shorter by an average of 0.24 mm Axial length measured is closer to the true value
  24. 24. Limitations and Pitfalls • Multiple Artifacts • Attenuation Artifacts • Low reflective Spike • Small tumours with False Negatives • Intraocular foreign body • Contact technique problem • Misalignment
  25. 25. MISALIGNMENT SILICON OIL GLOBE

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