Ocular scan indications 2014


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Ocular scan indications 2014

  1. 1. B-SCAN aSGuest132561 Download Share Add to Flag Embed Remove advertisement Views: 806 Category: Education License: Some Rights Reserved Presentation Description pls see Comments Presentation Transcript B-SCAN: B-SCAN NEHA RANKA FELLOW OPTOMETRIST RETINA FOUNDATION What is B-SCAN??: B-scan ultrasonography is an important adjuvant for the clinical assessment of various ocular and orbital diseases. With understanding of the indications for ultrasonography and proper examination technique, one can gather a vast amount of information not possible with clinical examination alone. What is B-SCAN ?? Indications: Indications Opaque ocular media Anterior Segment Corneal opacification Hyphema or hypopyon Miosis Cataract Pupillary or retrolenticular membrane Posterior segment Vitreous hemorrhage or inflammation
  2. 2. Indications for Intraocular Examination : Indications for Intraocular Examination Clear ocular media Post segment Tumours Choroidal detachment (serous vs hemorrhagic) Retinal detachment ( rhegmatogenous vs exudative ) Unexplained retinitis or chorioditis Anterior segment Iris lesions Ciliary body leisons Physics and Instrumentation: Physics and I nstrumentation Physics: Ultrasound Longitudinal wave Alternating compressions and rarefactions of molecules >20khz (20,000 oscillations /sec) Ultrasound Similar to sound waves Reflected Refracted Physics Abdominal ultrasound Ophthalmic ultrasound : Abdominal ultrasound Ophthalmic ultrasound Echoes : Produced by acoustic interface created at the junction of two media Greater the density difference at that interface , the stronger the echo , or the higher the reflectivity. Acuostic impedance = sound velocity x density Echoes Sound Wave Velocities : By karl ossoing Sound Wave Velocities Medium Velocity (m/sec) Water 1,480 Aqueous / vitreous 1,532 Soft tissue 1,550 Crystalline lens 1,641 Bone 3,500 ULTRASOUND PRINCIPLES AND PHYSICS: ULTRASOUND PRINCIPLES AND PHYSICS Angle of incidence : Perpendicularity to the area of interest always should be maintained to achieve the strongest echo . PROBE/TRANSDUCER : Pulse –echo system – piezoelectric crystal (face of probe ) PROBE/TRANSDUCER
  3. 3. Gain : Measured in decibels Higher gain – Display weaker echos like vitreous opacities Lower gain Stronger echoes ( retina and sclera) Better resolution Gain Instrumentation : Instrumentation A-Scan: A scan (amplitude) - single dimensional display of spikes through the eye. The spikes on A scan represent amplitude / reflectivity of an echo A-Scan B-Scan : Two dimensional acoustic section Dot Strength Echo Brightness B scan is coalescensce of multiple dots Real time movement of various lesions within the vitreous cavity. B-Scan Standardized Echography: The combined use of A scan and B scan B scan – Topographic nature of intraocular structures and lesions. A scan – Lesions character and size Standardized Echography Examination techniques for the globe : Examination techniques for the globe Positioning of The Patient : Reclinable examination chair of adjustable height Echographer standing to the patients right side Closed or open eyelid technique Positioning of The Patient Characteristics of B scan probes:
  4. 4. Contains a transducer that oscillates back and forth Marker usually a dot, line, logo – represents upper portion Best resolution is in the centre Characteristics of B scan probes B scan Probe Orientations: B scan P robe O rientations B-scan Probe Orientations : Transverse scan (M.C.) Longitudinal (M.C. ) Axial B-scan Probe Orientations Transverse Scan : Transverse scan Movement of transducer is parallel to limbus Produces a circumferential slice through several meridians Lateral extent of a lesion Transverse Scan Horizontal Transverse Scan: Horizontal Transverse Scan B-Scan Probe Orientations : Longitudinal scan Transducer - perpendicular to the limbus Probe marker - towards centre of cornea Antero posterior extent of the lesion Optic disc and posterior aspect of the globe –lower portion of screen Best – demonstrating the insertion of membranes to optic disc B-Scan Probe Orientations Longitudinal Scan of 12: Longitudinal Scan of 12 AXIAL SCAN: Axial scan Probe centered on the cornea Easiest to understand (displays lens & optic nerve) Documenting lesions & membranes in relation to optic disc Evaluates macular region Hinder resolution of posterior portion of globe (Sound attenuation and refraction ) AXIAL SCAN
  5. 5. Lesion Evaluation: Location Echo texture Relation with the optic disc Mobility Lesion Evaluation Location of Lesion: Localise the pathology from the probe position and quadrant scanned. Topographic ultrasonography Location of Lesion Echotexture of Lesion: Dot like lesions – vitreous floaters, vitreous hge , vitreous exudates. Membranous lesions – vitreous membranes, PVD, RD Mass lesions – choroidal or retinal tumors Echotexture of Lesion Relation to Optic Disc: RD – attached to optic disc CD – not attached to disc Relation to Optic Disc Kinetic Echography: Dynamically assess the motion of or within a lesion Three type of motions After movement Vascularity Convection movement Kinetic Echography Mobility of lesion (kinetic echography): Mobility of lesion with relation to eyeball movements After movement RD & CD move with eyeball, but movement stops as soon as the eyeball movement stops. Free after movements PVD Mobility of lesion (kinetic echography ) PowerPoint Presentation: Evaluating The Lesion Topographic evaluation of lesion at 10:30 position. Transverse scan showing lateral extent: Topographic evaluation of lesion at 10:30 position. Transverse scan showing lateral extent
  6. 6. Longitudinal scan showing radial extent.: Longitudinal scan showing radial extent. Axial scan showing relationship of lesion to anatomic landmarks of lens and optic nerve.: Axial scan showing relationship of lesion to anatomic landmarks of lens and optic nerve. Retinal Detachment : Retinal Detachment Bright ,continuous, folded membrane Total or extensive detachment inserts at optic disc or ora serrata A scan 100% height of spike Less than 100% spike height – atrophy , folded, disruption of retina Tethered restricted after movement CHOROIDAL DETACHMENT: CHOROIDAL DETACHMENT Smooth thick, dome shaped membrane in the periphery Little or no after movement, Doesn’t not extent beyond equator as it is limited by the vortex vein exit. Kissing Choroidals : 40 Kissing Ch oroidals IOFB : IOFB Typical Features Echodense signal with shadowing Persistence of the signal at lower gain May be missed if the probe is not perpendicular to the flat side of the foreign body. BUCKLE WITH VH : BUCKLE WITH VH Scleral Buckling Hyperechoic band producing indentation in the globe. Requirements for a good ultrasound assessment: Minimum elevation of approximately 1 mm - Detection . Minimum tumor height of 2 mm – quantification Higher frequency systems(UBM) are needed for better examination of smaller
  7. 7. tumors, especially if they are located anteriorly 43 Requirements for a good ultrasound assessment Microphthalmos: Microphthalmos Summary: Summary Technique PVD Retinal detachment Choroidal detachment Topographic Smooth, open funnel with or without disc or fundus insertion inserts at ora or ciliary body Smooth or folded, open or closed funnel with disc insertion associated cysts inserts at ora Smooth , dome , or flat no disc insertion inserts at ora or ciliary body Quantitative Spikes of variable amplitude < 100% amplitude at superior ora Steeply rising , 100% amplitude including at superior ora Steeply rising , thick , double – peaked spike 100% spike Kinetic Marked to moderate Moderate to none Mild to none thankyou: thankyou