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ULTRASONOGRAPHY INOPHTHALMOLOGY
B-SCAN
UBM
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INTRODUCTION
One of the commonest non invasiveimaging investigative procedures
Complementary to CT & MRI
Cheaper, can be done in office setting
Done by Ophthalmologist with a dedicatedophthalmic US
All types of USG useful Wide range of applications
Particularly helpful in opaque media
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HISTORY
Mundt & Hughes (1956): A scan to evaluateintraocular tumour Oksala et al: A scan for diagnosis of intraocular
disorders / Data of sound velocities of variouscomponents of the eye
Baum & Greenwood (1958): B scan for Ophthalmicuse Jansson et al(1960): Used US to measure the
distances between different structures of the eye Coleman et al(1970): 1st commercially available
immersion B Scan Bronson: Contact B scan for Ophthalmic use Ossoinig (1960): Standardization of instrumentation
& technique Standardized Echography /Meticulous examination techniques
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ULTRASOUND
Acoustic wave of frequencies >20kHz
Diagnostic US in Ophth : 8-10 MHz
Higher frequency Better resolution Lower frequency Deeper penetration
Velocity depends on the medium
Longitudinal waves behave like light Refraction & Reflection property makes US
useful for diagnostic purpose
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B - SCAN
Brightness mode 2 Dimensional acoustic section where
echoes are plotted as dots Brightness of dots Strength of received
echo Uses focused beam from an oscillating
transducer that slices through tissue Useful in evaluation of intraocular structures
with opaque media & of orbital lesions Biggest advantage: Dynamic Echography
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Rapidly repeating short bursts ofultrasonic energy are beamed intoocular & orbital tissue.
Multiple short pulses of ultrasoundenergy are produced with a briefinterval between the pulses that
allows for the returning echoes to bedetected, processed & displayed.
Pulse-Echo Technque:
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ECHOES
Echoes are produced by interfaces
created at junction of 2 media ofdifferent acoustic impedances
Ac. Impedance = Velocity x Density
Greater difference in Impedance Stronger reflection (Echo)
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Medium 1 Medium 2
Medium 1 Medium 3
ACOUSTIC IMPENDANCE
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Returning of Echoes
Angle of sound incidence
Size, shape & smoothness of acousticinterfaces
Absorption
Scattering Refraction
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Different Types of Acoustic Interfaces
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Schematic Diagram of Ultrasound System
Transducer
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Probe / Transducer
(10 MHz) The part of US system where the US is
produced & through which the echoes arereceived
When stimulated by electric energy,Piezoelectric crystal located near the face ofthe probe undergoes mechanical vibrationproducing US in pulses.
The vibration of the echo produces anelectric signal that is transmitted to thereceiver, which is then processed.
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B-Scan Transducer
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Signal Processing
Electric Signal produced by returningecho is initially received as a very
weak RF signal which undergoes acomplex processing comprising of :
# Amplification
# Compensation
# Compression
# Demodulation
# Rejection
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DISPLAY MODES:
The processed signal is desplayed oncathode ray tubes in one two modes-
Ascan or Bscan.
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Concept of B-scan
interpretation: Real time- images can be visualised at
approx.32/sec,allowing motion of
globe & vitrious. Gray scale-returning echoes are two
dimensional images.
strong echoes-brightWeak echoes- lighter shades of gray.
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B - SCAN
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B-Scan Exam Techniques
for the Globe
Transverse
Longitudinal
Axial
Ant Segment : Contact
Post Segment : Immersion
SCANS:
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Transverse Scans
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Longitudinal Scans
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Axial Scans
Probe face centered on the cornea withpatient in primary gaze
Sound attenuation & refraction from thelens hinder resolution of the posteriorsegment
Helpful for lesions in relation to the lens &
optic nerve Can be useful for evaluation of macular
region
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Basic B-Scan Screening
Examinations
Transverse scans of 4 major quadrants
Longitudinal scans along 4 majormeridians
Vertical & Horizontal axial scans
Procedures performed both at high &low gain settings
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Special Exam Techniques
TopographicLocation
Extension
Shape
QuantitativeReflectivity
Internal structure
Sound attenuation Kinetic
Mobility : Aftermovement
Vascularity : Blood Flow
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Topographic Evaluation
Transverse scan Lateral extent
Longitudinal scan Radial extent
Axial scan Relationship of the lesionto anatomical landmark of lens & optic
nerve
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Quantitative Echography
Reflectivity : signal brightnessInternal Structure : echodensity
Sound Attenuation : Progressivedecrease in the strength of echoes,either within or posterior to a lesion
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Kinetic Echography
Used to dynamically assess the motionof or within a lesion
Aftermovement : motion of the lesionechoes following cessation of eyemovement
Vascularity : Spontaneous motion ofechoes
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Evaluation of Vitreous
Normal vitreous : In young, no echo.
In old, scattered echoes of lowreflectivity for opacities & fine thin linefor PVD
Asteroid Hyalosis : Diffuse or focalbright, point like echoes
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Asteroid Hyalosis
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Vitreous Haemorrhage
Fresh & mild : Dots & short lines
Dense : Greater no. of bright dots Organization : Larger interfaces
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PVD
Thin undulating irregular membrane ofirregular echotexture
Kinetic echography: Distinct AftermovementEven in presence of attachment to optic disc
May be focal or extensive
May separate completely from post. pole or
may remain attach to optic disc Challenging to differentiate from RD & CD
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PVD attached to Disc
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PVD with VH
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Endophthalmitis
Very useful for determining the severity &extent of the infection
Irregular low intensity echoes seen as
diffuse fine dots on B-Scan Appreciated only on high gains in early
stage Differentiation from VH :
- Heterogenous (VH : Homogenous)- PVD more extensive in VH- Pseudomembrane more common in VH
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Endophthalmitis
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Retinal Evaluation
Retinal Tears : High reflectivity with slightaftermovement
RD: Bright, Continuous Membrane of
uniform echotexture
: Mobility depends on type of RD &associated findings
: Besides topography, B-Scan is useful indetermination of configuration
: Hole, tear, band should be looked for
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Rheg RD
Membrane of uniform echotexture(even at low gain)
Minimum aftermovement
Flickering movement over themembrane : Diagnostic
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Rheg RD
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Exd RD
Usually Shallow RD
Marked thickening of Chorio-Retinal
Layer Marked Mobility
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Exd RD
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RD vs. PVD
RD PVD
Echotexture Thick, Uniform Thin,Undulating
Aftermovement No or Minimum Free Movement
Attachment toOptic Disc
Smooth Irregular
Reflectivity @low gain
Homogenous Irregular orAbsent
Peripheral
Reflectivity
100% Reduced
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PDR
Demonstrates the nature & extent
Useful in monitoring progression
Helps pre-vitrectomy evaluations
* Timing of surgery
* Planning of Surgery
* Optimal placement of instruments
* Visual prognosis
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PDR
Fibrovascular Membrane
Subhyaloid Hemorrhage
Vitreous Hemorrhage
PVD
TRD
Combined Rheg RD with TRD
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Retinoschisis
B-Scan : Smooth, thin, dome shapedmembrane not inserting to optic disc
Typically located inferotemporally
Differs from RD by its more focal,
smooth & thin character
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Choroidal Evaluation
Choroidal Thickening :
* Edema Highly reflective
* Diffuse inflammatory infiltrationLow to medium reflective
Mildly elevated, diffuse choroidal
tumors can be confused withnonspecific choroidal thickening
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Choroidal Detachment
B-Scan : Smooth, thick, dome shapedmembrane at periphery with little
aftermovement
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Choroidal Detachment
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Evaluation of Sclera
Posterior Scleritis :* Best imaging modality
* Thickened hyperechoeic sclera
* Hypoechoic rim around sclera* T sign : Diagnostic
Staphyloma :Diffuse thinning Coloboma of ON :Defect in post. sclera
Scleral Rupture :Break in sclera, Vitreous Thickened chorioretinal layer incarceration, Hge in Tenons space,
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Intraocular Tumors
The most important noninvasive adjunct toclinical exam even in presence of clearmedia
Standard Echography is valuable inevaluation of intraocular tumors
Provides accurate measurements, thereforevaluable for assessment of tumor growth orregression
Helpful in detecting extrascleral extension
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Detection of Tumors
At least 0.8mm elevation forultrasonographic detection
2-3mm height required for effectivequantitative evaluation
Solid Tumors :
No aftermovement of surface
Presence of internal echoes
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Choroidal Melanoma
B-Scan
Dome or Collarbutton shaped
Uniform iso orhypoechoic texture
Highly vascular :
Fast flickeringmovement
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Choroidal Melanoma
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Retinoblastoma
Irregular dome shaped mass lesionwith broad base over the retina
Calcification when present : Diagnostic Mixed Echotexture
Normal Axial Length
High Irregular Reflectivity
Distal Shadowing
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USG in Traumatized Globe
Great value, specially in trauma by missiledFB
Lid swelling : Exam through closed lids Any open wound should be repaired prior to
examination
Very high gain settings when examined
through closed lids Knowledge of various post traumatic ocular
changes is necessary
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IOFB
Dense short linear echo
Distal shadowing
Spherical FB : Dense echogenic distalshadow
Freely floating FB : No distal shadow
May get masked by associated VH
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Freely Floating IOFB
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USG in Post Op.
Dropped Nucleus / Lens / IOL
Scleral Buckle
Intraocular Gas
Silicon Oil
Suprachoroidal Hemorrhage
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USG Orbit
Orbital Soft Tissue Assessment
Extraocular Muscle Evaluation
Retrobulbar Optic Nerve
Examination
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Orbital MassDifferentiation
Topographic : Location, Shape,
Borders, Contour abnormalities Quantitative : Internal reflectivity,
Internal structure, Sound attenuation
Kinetic : Consistency, Vascularity,Mobility
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Evaluation of EOM
Effective in subtle & early muscle sizechange
Useful to differentiate various causesof muscle enlargement
Less echo-dense than orbital soft
tissue on B-Scan
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Evaluation of Rectii
Medial Rectus : Primary gaze, Probeon temporal equator
Lateral Rectus : 10Temporally,Probe placed medially
Inferior Rectus : 10Inferiorly, Probeplaced superiorly on the upper lid
SR & LPS : Primary gaze / Slightlysuperiorly, Probe inferiorly
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Evaluation of Obliques
SO Tendon : Horizontal transverse scanthrough the superior orbit
SO Belly : Oblique transverse scan throughthe superonasal orbit
IO Tendon : Oblique transverse scanthrough inferotemporal orbit
IO Belly : Difficult to display. Whenthickened : Horizontal transverse scanthrough most ant. aspect of inf. orbit
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Optic N Evaluation
B-Scan can evaluate topography &relationship of ON
Usually performed in medium gainAxial, Longitudinal & Transverse scan
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Optic Disc Evaluation
B-Scan can demonstrate excavation,elevation & drusen of Optic Disc
Axial, Longitudinal & VerticalTransverse approaches are useful
A-Scan useful in assessing reflectivity
& height of certain lesions of OD
UBM
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UBM High frequency US : 35-100 MHz
Provides near microscopictwodimensional gray scale images of
anterior segment Extensive use in Glaucoma
Also useful in ant. segment disorders
including cysts & tumors with cloudy /opaque cornea, blunt trauma,canalicular imaging etc.
P i i l
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Principle:
There are wide range of frequenciesranging from10- 20000Hzto>10/12Hz.
Resolution is related to full widthof US beam at half max amplitude(FWHM)=cf/vd=wavelengthC-speed of sound.
F- focal length of transducer.V-frequency.D-diam of transducer.Incresed resolution is accompanied by
loss of penetration.
D i f UBM
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Design of UBM
Scanner detected signals aredigitalised.
Transducermade up of pizoelectricpolymer PVDF & copolymer PVDF.Itachieves highest resolution & good
depth of focus.
I t t ti
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Instrumentation:
Front panel consists of large highresolution LCD screen.
Rear panel which plugs for connectionto probe,monitor & power connector.
HF Probe which are light weight accept35-50 MHz transducer & scan at 38 or20 degree scan angles at 15 mm maxscan depth.
Immersion cup
35 MHz transducer offer 70 of axial
resolution & 50 MHz offer 50.
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Examnation Technique:
Patients:supine with eye fixated at ceiling. Topical anaesthesia-immersion cup is placed
with lips of cup under the lids.
Fluid coupling medium instilled. Transducer have no membrane cover&
moves at the rate of 8passes/sec.It isplaced opposite the area of intrest.
Pt. is asked to look away from site ofpathology to bring pathological area into ex.Position.
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Probe orientation
Transverse Scan
Longitudinal scan
Axial Scan.
M t f l
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Measurment of ocularstrucure:
Depends on speed of a sound instructure.
It consists of time required for soundto traverse the tissue & return totransducer.
Mainly 1550m/sec speed of sound isused which increases accuracy tomeasure AC depth,iris thickness,C.B.
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Mesurment modes:
Vector 1550-linear measurement
Callipers-pairs of linear cursor for
linear measurment.Angle Measure
Biometry -accurate dist. Measurement
in ant .seg. Along optical axis.
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Normal ocular structure:
Cornea: layers appreciated
epi.-smooth surface line.
Stroma-reveals internalreflectivity.
B.M.s-highly reflective line.
AC-Its easy if internal corneal surface&ant surface of lens is clearlyapreceatd.
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Angle region: probe is oriented in radialfashion above the limbus.
Scleral spur is reffering pt. for measuringangle.
TrabecularIris angle:bet. Apex of irisrecess & arms passing through the
meshwork 500 m from scleral spur & thept. of iris perpendicularly ,opposite ismeasured.N-30 +/- .
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ZONULES & LENS:Ant zonules Iris:Thickness& curvature of iris is measured
highly reflective layer on post. Surface helpsin differnciating intra-iris lesion from thelesion behind iris.
Cilliary body: shows configurations of cilliaryprocesses & vallies bet. them
dist. Bet. Ant. Trabecular meshwork & cilliaryprocesses is measured & ant lens surface canbe seen.
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Quantitative Measurments:
AOD: bet. TM & IRIS at 500m ant toscleral spur.
TIA:ang of iris recess. ID1:iris thickness at 500m ant to s. spur.
ID2: iris thickness at 2 mm from iris route
ID3: Max iris thickness near pupillary edge
TCPD;bet TM& C.P. at 500m ant to s.spur.
ICPD; bet iris & CP. Along the line of TCPD.
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IZD:Bet iris & zonules Along the line ofTCPD.
ILCD: Contact dist. Bet iris & lens Iris lens ang: ang . Near pupillary
edge.
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CLINICAL USES:
Cornea: conj. Mass lesion
pre PK evaluation of ant seg
corneal thickness
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Glaucoma: evaluate post op shallow AC
malignant glaucoma
plateau iris
PDSiridozonular contact
bleb evaluation
cyclodylasis cleft
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Lens: zonular inttegrityPC integrityHaptic position
Uvea:Parsplanitis in media opacityscleritis
Vitrioretinal diseases:sclerotomy sitepars plana FB
Peripheral VR disMas lesions: iris & CB cyst, umors& lid lesions
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The sclera is imaged as a highlyreflective structure compared to thecornea. One can generally differentiatethe sclera from overlying episclera and
underlying ciliary body and retina
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Scleral thinning can be imaged and thethickness of residual sclera quantified
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Scleritis shows relatively low reflectiveregions within the sclera likely representingedema and inflammatory infiltrates.
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The anterior zonule can normally be clearlyimaged. Disruption will result in absentzonules, increased lens sphericity, andincreased distance of the lens margin from
the ciliary body.
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Cyclodialysis shows completedisinsertion of the ciliary body fromthe scleral spur accompanied by a 360
degree supraciliary effusion
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Anterior segment foreign bodies can belocalized. They generally present as areflective lesion with shadowing of
structures behind the foreign body.
IRIDOCILLIARY
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IRIDOCILLIARYCYST
Ciliary Body or
Iris Tumor
Accommodation and Iris
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Accommodation and IrisConfiguration
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