Ophthalmic ultrasound

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  • 1. OPHTHALMIC ULTRASOUNDDr. Yousaf Jamal 26/05/2012

2. Contents Introduction Instrumentation Indications Ultrasound Principles & physics B-scan, UBM, A-scan & techniques MCQs3/15/2013 2 3. Objectives To create awareness about basics of US To emphasize on the importance of ophthalmic US To create & follow standard operating protocol while performing ophthalmic US3/15/20133 4. Introduction Sound Noise Ultrasound What is Supersonic Hypersonic Transonic3/15/2013 4 5. Just for test of general knowledge Who was the first one to use ultrasound??3/15/2013 5 6. Echolocation types3/15/20136 7. TYPESA SCANB SCAN 8. Instrumentation Pulsed-echo system Transducer Amplifier Display monitor3/15/20138 9. Transducer function ELECTRIC CURRENTTRANDUCERUS WAVES SURFACE3/15/2013 9 10. Artist: Dr. Yousaf Jamal3/15/201310 11. B-Scan3/15/201311 12. B-scan Brightness mode scan OPD procedure3/15/2013 12 13. Indications To examine intraocular structures with no direct visualization of posterior segment Or To confirm or differentiate between pathologies in clear media3/15/201313 14. Ultrasound physics & principles Parts of Sound wave Amplitude Wavelength (crest & trough) Frequency3/15/2013 14 15. Frequency & its relationsWith resolution Image qualityWith penetrationHow much deep3/15/2013 15 16. Frequency versus Resolution3/15/2013 16 17. 3/15/2013 17 18. Frequency versus Penetration3/15/2013 18 19. 3/15/2013 19 20. Medical Ultrasound frequencies Abdominal US 1-5 MHz Ophthalmic US (B-scan) 8-10 MHz Ultrasound Biomicroscopy (UBM) 20-50 MHz3/15/2013 20 21. Ophthalmic US B-scan 10 MHz 40 mm 940 microns UBM 50 MHz 5-10 mm 40 microns3/15/201321 22. Principles of US Velocity Reflectivity Angle of incidence Absorption3/15/2013 22 23. Velocity Depends upon density of medium Distance = speed x time Thru air Thru aqueous & vitreous 330 m/s 1532 m/s Thru water Thru cornea & lens 1500 m/s 1641 m/s Thru metal Thru silicon oil1000 CS 5000 m/s 980 m/s Thru blood Thru silicon oil5000 CS 1570 m/s 1040 m/s 3/15/2013 23 24. Reflectivity (Echo) Follows law of Acoustic impedance A.I. = sound velocity x density of mediumMedium Acoustic impedance (x106) kgm-2 s-1Fat1.38Human tissue 1.63Blood1.61Muscle 1.70Bone 5.6-7.8Vitreous 1.52Aqueous1.50Lens 1.84243/15/2013 25. Higher gain for weaker echoes Low gain for stronger echoes3/15/201325 26. Angle of incidence Transducer3/15/201326 27. Absorption Dependent on density of medium Closed lids should be therefore avoided but in children or open wound Shadowing occurs bcz of it3/15/201327 28. Probe positioning Trans-ocular approach Transverse Longitudinal Axial Para-ocular approach3/15/2013 28 29. Trans-ocular Transverse position Most commonly used position Shows about 6 clock hours Used for basic screening Detects lateral extent of pathology Probe is placed opposite to the examinedmeridian3/15/201329 30. Probe marker is tangential to limbus Mark is at nasal side when scanning 6 and12 oclock For the restmarker is superior Limbus-to-fornix approach is used todetect from posterior pole to peripheryNasal3/15/2013 Bridge30 31. Longitudinal positions Detects axial (AP) extent of pathology Useful for retinal tears detection Shows only 1 clock hour scan3/15/201331 32. Probe mark is perpendicular to limbus Pt looks towards the area of interest Optic nerve shadow is always at bottom ofscan Limbus-to-fornix approach can be used3/15/2013 32 33. Axial positions Probe direct 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 image3/15/201333 34. Positions of axial scan Horizontal Marker always nasal Vertical Marker always superior Oblique Marker always superior Nasal Bridge3/15/2013 34 35. Basic screening technique Done for screening purpose in opaque media Highest gain settings are used so weaker signals shouldnt be missed Any pathology foundfurther scanning is required3/15/2013 35 36. Technique 05 scans in different positions will detect gross pathology Transverse position with limbus-to-fornix approach in 12, 3, 6 and 9 oclock Horizontal axial scanshows optic nerve & macula in one image Print out of each position is taken with labels3/15/201336 37. If pathology found Clock hour noted on transverse scan Patient is asked to look in the direction of pathology Probe should be perpendicular Longitudinal scan, A-scan & change of gainsadds further info of pathology3/15/2013 37 38. Localization of macula 04 positions for macular detection Horizontal axial Vertical axial Transverseprobe placed nasally Longitudinalprobe placed nasally3/15/2013 38 39. Anterior segment evaluationImmersion techniqueHigh resolution technique3/15/2013 39 40. Immersion technique Cornea, anterior chamber & lens create noise bcz of close contact with probe Shell or water bath is used to create space3/15/2013 40 41. High resolution technique Ultrasound biomicroscopy High resolution probes are used Scleral shell technique is used Image quality far superior to immersion technique3/15/201341 42. 3/15/2013 42 43. Common examples Vitreoretinal disorders Most common indication for B-scan Vitreous hemorrhage Retinal detachment Intraocular tumors Intraocular foreign bodies3/15/201343 44. Vitreous hemorrhage Fresh: Dot-likeEcholucent or low reflectivity Old: Membrane-likevarying reflectivity &dense inferiorly3/15/2013 44 45. Fresh VH Old VH3/15/2013 45 46. 3/15/2013 46 47. Retinal detachment Rhegmatogenous R/D: Thin, continuous membrane anteriorlyseparated from globe wall Echoes are of high amplitue-100% ofscleral spike Retinal cysts, subretinal hemorrhages maybe seen3/15/2013 47 48. 3/15/2013 48 49. Tractional R/D: Traction membranes are seen R/D usually doesnt extend to ora serrata Lower mobility in contrast to Rheg. R/D3/15/2013 49 50. 3/15/2013 50 51. 3/15/2013 51 52. Exudative R/D: Smooth elevation of retina Shifting fluid3/15/201352 53. Supine position Erect position3/15/2013 53 54. Intraocular tumors Retinoblastoma: Single or multiple mass lesions arisingfrom retina Highly refractile calcium seeding invitreous +/- orbital shadowing R/D may be found3/15/2013 54 55. 3/15/2013 55 56. Choroidal melanoma: Solid Dome shaped or mushroom shape High surface reflectivity with low tomedium internal reflectivity A scan flickering spikesinternal bloodflow Choroidal excavation Exudative R/D may be present3/15/2013 56 57. 3/15/2013 Dome shape 57 58. Collar stud shape Arrowhead in A scan shows bruchs membrane3/15/2013 58 59. Intraocular foreign body Echodense signals with shadowing Persistence of signals at low gains Glassreverberations Air bubblemay simulate IOFB3/15/201359 60. 3/15/2013 60 61. Dislocated lens Signals depend on clarity of lens Clear lensEcholucent globular structure Brunescent lenshighly reflective with shadowing3/15/2013 61 62. 3/15/2013 62 63. 3/15/2013 63 64. A-Scan3/15/201364 65. A - scan Amplitude scan 10 MHz probe Measures axial length of eye and used for diagnostic purposes when combined with B-scan Follows law of acoustic impedance3/15/201365 66. X-axistime Y-axisamplitude Method Applanation technique Immersion technique3/15/2013 66 67. A-scan by Applanation Cornea is anesthetized Patients should look directly at the redfixation light Probe placed directly on cornea This causes a slight indentation (0.14 -0.28 mm) 68. Measurements vary slightly from each other due to inconsistent corneal compression Also, will have a shallower AC depth than immersion Takes (20) readings3/15/201368 69. At least (4) of these should be within 0.02mm of each other, and should look likethe previous slide This way the measurements will be madeto the center of the macula, giving therefractive axial length, rather thananatomical axial length 70. 3/15/2013 70 71. 3/15/2013 71 72. 3/15/2013 72 73. A- Scan facts Average length of the eye: 23.5mm Average A/C depth: 3.24mm (but canvary greatly) Average lens thickness: 4.63mm ( but canvary with cataractous changes up to asthick as 7.0mm in density) Average Ks : 43.00 44.00D 74. Summary Ophthalmic UShigh frequency A & B scans mostly used Different pathologies can be diagnosed easily when both scans are used simultaneously3/15/2013 74 75. Take home message Understanding of basic physics Proper standardized technique should be applied in each case Eyes do not see what mind does not know So background knowledge of pathologies and experience count the yield of US3/15/201375 76. 3/15/2013 76 77. MCQs / Cases3/15/2013 77 78. MCQs / Cases 1. A patient presents with bilateral granulomatous panuveitis with hazy fundus view due to cataract. No Hx of trauma. B scan picture is given below:3/15/2013 78 79. A. What is the probe position? Axial B. What do the arrow head and arrow show? Retinal detachment Choroidal thickening C. Probable diagnosis? V-K-H3/15/201379 80. 2. A young patient with blunt ocular trauma comes to your opd, complaining of floaters with normal visual acuity. You order B scan which is given below3/15/2013 80 81. Describe the picture What is your probable diagnosis? How you differentiate it from retinal detachment?3/15/201381 82. 3. An old patient complains of decreased vision after trabeculectomy. There is large bleb but hypotonic eye. B scan shows3/15/201382 83. Describe the picture Your probable diagnosis?3/15/2013 83 84. 4. Describe the following A-scan Ans Immersion technique A-scan3/15/2013 84 85. 5. What you say about these A-scans? Ans Artifacts By IOL (Reverberations)3/15/2013 85 86. 6. Diagnosis?AnsHypotonic eye with choroidal thickening 3/15/201386 87. NEXT Lecture Dr. Bilal corneal topography Journal club Dr. Maooz3/15/201387