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USG B SCAN OPHTHALMOLOGY
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- 3. TYPES A – SCAN B– SCAN
- 4. Instrumentation • Pulsed-echo system − Transducer − Amplifier − Displaymonitor 3/15/2013 8
- 5. Transducer function ELECTRIC CURRENT TRANDUCER USWAVES SURFACE 3/15/2013 9
- 6. 3/15/2013 10 Artist: Dr.Yousaf Jamal
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- 8. B-scan • Brightness modescan • OPD procedure 3/15/2013 12
- 9. Indications • To examineintraocular structures with no direct visualization of posterior segment Or • To confirm or differentiate between pathologies in clear media 3/15/2013 13
- 10. Ultrasound physics &principles • Parts of Sound wave − Amplitude − Wavelength (crest & trough) − Frequency 3/15/2013 14
- 11. Frequency & itsrelations With resolution Image quality With penetration How much deep 3/15/2013 15
- 12. Medical Ultrasound frequencies •Abdominal US − 1-5 MHz • Ophthalmic US (B-scan) − 8-10 MHz • Ultrasound Biomicroscopy (UBM) − 20-50 MHz
- 13. Ophthalmic US • B-scan − 10MHz − 40 mm − 940 microns • UBM − 50 MHz − 5-10 mm − 40 microns 3/15/2013 21
- 14. Principles of US •Velocity • Reflectivity • Angle of incidence • Absorption 3/15/2013 22
- 15. • Higher gainfor weaker echoes • Low gain for stronger echoes 3/15/2013 25
- 16. Angle of incidence 3/15/201326 Transduc er
- 17. Probe positioning • Trans-ocularapproach − Transverse − Longitudinal − Axial • Para-ocular approach 3/15/2013 28
- 19. Transverse position − Most commonlyused position − Shows about 6 clock hours − Used for basic screening − Detects lateral extent of pathology − Probe is placed opposite to the examined meridian 3/15/2013 29
- 20. Longitudinal positions − Detects axial(AP) extent of pathology − Useful for retinal tears detection − Shows only 1 clock hour scan 3/15/2013 31
- 21. Axial positions • Probedirect over the cornea • Pt looks in primary gaze • US waves pass thru center of lens and hit optic nerve rather than macula • Lens density affects the quality of image 3/15/2013 33
- 22. Basic screening technique •Done for screening purpose in opaque media • Highest gain settings are used so weaker signals shouldn’t be missed • Any pathology found…further scanning is required 3/15/2013 35
- 23. Technique • 05 scansin different positions will detect gross pathology • Transverse position with limbus-to-fornix approach in… − 12, 3, 6 and 9 o'clock • Horizontal axial scan …shows optic nerve & macula in one image • Print out of each position is taken with labels 3/15/2013 36
- 24. Common examples Vitreoretinal disorders •Most common indication for B-scan − Vitreous hemorrhage − Retinal detachment − Intraocular tumors − Intraocular foreign bodies 3/15/2013 43
- 25. Vitreous hemorrhage • Fresh: − Dot-like…Echolucentor low reflectivity • Old: − Membrane-like…varying reflectivity & dense inferiorly 3/15/2013 44
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- 28. Retinal detachment • RhegmatogenousR/D: − Thin, continuous membrane anteriorly separated from globe wall − Echoes are of high amplitue-100% of scleral spike − Retinal cysts, subretinal hemorrhages may be seen 3/15/2013 47
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- 30. • Tractional R/D: − Tractionmembranes are seen − R/D usually doesn’t extend to ora serrata − Lower mobility in contrast to Rheg. R/D 3/15/2013 49
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- 33. • Exudative R/D: − Smoothelevation of retina − Shifting fluid 3/15/2013 52
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- 35. Intraocular tumors • Retinoblastoma: − Singleor multiple mass lesions arising from retina − Highly refractile calcium seeding in vitreous +/- orbital shadowing − R/D may be found 3/15/2013 54
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- 37. Intraocular foreign body •Echodense signals with shadowing • Persistence of signals at low gains • Glass…reverberations • Air bubble…may simulate IOFB 3/15/2013 59
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- 39. Dislocated lens • Signalsdepend on clarity of lens • Clear lens…Echolucent globular structure • Brunescent lens…highly reflective with shadowing 3/15/2013 61
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