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8/22/2019 B SCAN ppp
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B – SCAN ULTRASONOGRAPHY
Dr. Parameshwar RaoDr. HaridevDr. AshokDr. Siva Kumar.W (PG)
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INTRODUCTION
B-scan ultrasonography is an important adjuvant for the clinical assessment of
various ocular and orbital diseases. This presentation is designed to
describe the principles, techniques, and indications for echographic examination,
as well as to provide a general understanding of echographic characteristics of various ocular
pathologies.
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B- SCAN is a two dimensional imaging
system which utilises high freq soundwaves ranging from 8-10 MHz.
B stands for bright echoes.
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B - SCAN
It was first introduced by Baum and
Greenwood in 1958
First commercially available B scan is
developed by Coleman et al in seventies
The importance of the instrument and
technique is emphasised by Karl Ossoinig
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Physics: It is an acoustic wave that consists of particles
within the medium
Frequencies used in diagnostic ophthalmicultrasound are in the range of 8-10 MHz
These high frequencies produce shorter wavelengths which allow good resolution of minute
ocular and orbital structures
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Multiple short pulses are produced with a
brief interval that allows the returning
echos to be detected, processed anddisplayed.
The basis of the echo system is
piezoelectric element which is a quartz or ceramic crystal located near the face of the
probe
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sound waves from
transmitter
Echoes are received
by receiver
Amplification
Oscilloscope screen
Target tissue
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Low frequency: orbital tissue
Medium frequency : ( 7 – 10 mhz )
Retinal , vitreous , optic nerve
High frequency : ( 30 – 50 mhz) :
ant chamber upto 5 mm
Types of frequency
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IMPEDENCE : The difference between
the strength of the returning echoes
from tissues with abrupt changes in
acoustic properties.
GAIN : Increase in gain is associated
with increase in tissue penetration and
sensitivity but decrease in resolution.
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HIGH FREQUENCIES - LOW
PENETRATION BUT GOOD
RESOLUTION.
(abdominal US-1-2MHz )
INCREASE IN GAIN - INCREASE IN
TISSUE PENETRATION AND
SENSITIVITY – DECREASE IN
RESOLUTION.
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INCREASE IN GAIN - INCREASE IN TISSUEPENETRATION AND SENSITIVITY – DECREASE IN
RESOLUTION.
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DISPLAY MODES: A SCAN/ B SCAN /
BOTH
TIME GAIN COMPENSATION: to
enhance echoes from deeper structures.
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AMPLIFICATION
Three types are commonly used.
1. Linear : Can show minor differences in
echos . Limited range .(A SCAN)2. Logarithmic : Wider range. Minor
differences cannot be seen.(B SCAN)
3. S Curve : Combines the benefits of boththe above.(in the standardized A SCAN for
tissue differentiation)
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The probe has ‘ Damaging material’ which
limits the vibrations of the crystal thus
shortening the pulseShape of the crystal is useful in determining
the character of the sound beam
The electrical signal produced by returningechos is of very weak radio frequency signal
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This signal undergoes complex
processing before displayed on the
screen Adjust the amplification of the signal
displayed on the screen, this is referred
as ‘gain’ or ‘sensitivity’ of the instrument The higher the gain level the greater the
sensitivity of the instrument
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It produces Two dimensional section
It uses both horizontal and verticaldimensions of screen to indicate
configuration and location
A section of tissues is examined byan oscillating transducer
Instrumentation:
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An echo is represented by a dot on the
screen
The probe is filled inside with a fluid , a
crystal oscillates sending sound waves
out in a fan like array called Sector
scan
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Image documentation modes :
They are of 2 types
stationary/static
moving/dynamic
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The images may be saved in different
methods
1. Polaroid photographs
2. 35 mm photo
3. Ink prints
4. Thermal prints
5. Videotapes
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Anterior segment:
1. Opaque ocular media (i.e. corneal opacities)
Pupillary membrane
Dislocation / Subluxation lens
Cataract / after cataract
Posterior capsular tear
Pupillary size / reaction2. Clear ocular media
Diagnosis of iris and ciliary body tumors
Indications:
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Posterior segment:
1. Opaque ocular media
Vitreous haemorrhage
Vitreous exudation
Retinal detachment (type / extent)Posterior vitreous detachment (extent)
Intraocular foreign body (size/ site/ type)
2. Clear ocular media
Tumour (size/ site/ post treatment follow up)Retinal detachment (solid / exudative)
Optic disc anomalies
3. ocular trauma
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The patient is
either reclining
on a chair or lying on a
couch. The
probe can beplaced directly
over the
conjunctiva or
the lids.
Examination technique:
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Probe positions
Transverse : most common
Lateral extent, 6 clock hours
Longitudinal : radial ,1 clock hrs, AP
diameter in Retinal tumors and tears
Axial : lesion in relation to lens and
optic nerve .
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Transverse scan
EYE anaesthetised.
EYE – looking in the direction of observer’s
interest PROBE –parallel to limbus and placed on
the opposite conjunctival surface
PROBE MARKER – superior (if examiningnasal or temporal) or nasal(if examining
superior and inferior).
6 clock hrs examined at a time.
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The clock hour which the marker faces
is always at the top of the scan.
The area of interest in a properly donetransverse scan is always at the centre
of the right side of scan.
If examining nasal area -12 –
6 clock hrstemporal - 6- 12 clock hrs
superior - 9 -3 clock hrs
inferior - 3- 9 clock hrs
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NASAL AREA TEMPORAL AREA
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SUPERIOR AREA INFERIOR AREA
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Longitudinal scan EYE Anaesthetised.
EYE - looking in the direction of observer’s
interest.
PROBE – perpendicular to the limbus and
placed on the opposite conjunctival surface. PROBE MARKER- directed towards the limbus
or towards the area of interest regardless of the
clock hour to be examined.
Optic nerve shadow always at the bottom on
the right side.
1 clock hour .
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Axial scan
EYE anaesthetised.
EYE – in primary gaze
PROBE – centered on the cornea .
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LENS: Oval highly reflective structure
with intralesional echoes with none to
highly reflective echoes.
VITREOUS is echolucent.
RETINA, CHOROID AND SCLERA:
Are seen as a single reflective high
structure.
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OPTIC NERVE : Wedge shaped acousticvoid in the retrobulbar region.
EXTRA OCULAR MUSCLES : Echolucentto low reflective fusiform structures. The
SR- LPS complex is the thickest. IR is the
thinnest. IO is generally not seen except inpathological conditions.
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ORBIT -highly reflective due to orbital
fat.
Always examine the other eye before
coming to a conclusion regarding the
lesion .
Opacities produce dots or short lines
Membranous lesions produce an
echogenic line
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Anterior segment evaluaton
Immersion technique
High resolution technique
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ULTRASONOGRAPHIC
CHARACTERISTICS
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VITREOUS HAEMORRHAGE
To detect extent,
density, location and
cause
Fresh haemorrhage
shows dots or lines
Old haemorrhage
the dots gets
brighter
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POSTERIOR VITREOUS DETACHMENT
Posterior vitreous
detachment:
The detachedposterior vitreous
is seen as
membranouslesion with
no/some
attachments to the
o tic disc
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POSTERIOR VITREOUS DETACHMENT
Mobility of PVD is
more than RD.
The spike of RD is
more than PVD.
PVD becomes more
prominent in higher
gain settings
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RETINAL DETACHMENT
The detachmentproduces a brightcontinuous, folded
appearance withinsertion into the discand ora serrata.
It is to determine theconfiguration of thedetachment asshallow, flat or bullous
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EXUDATIVE RETINAL DETACHMENT
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RHEGMATOGENOUS RD
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RHEGMATOGENOUS RETINAL DETACHMENT
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CLOSED FUNNEL RD WITHRETINAL CYST
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CLOSED FUNNEL RD WITHRETINAL CYST
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APPEARS AS RD BUT IT IS A PVD.
CLUES: NON UNIFORM THICKNESS OF MEMBRANE
VERY THIN ATTACHMENT TO THE DISC.
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RETINAL TEAR
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RETINAL TEAR WITH FREE SUPERIOR END .
THE MEMBRANE IS CONVOLUTED ON ITSELF.POSTERIOR VITREOUS IS ATTACHED AT THE
SUPERIOR END OF THE TEAR.
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ASTEROID HYALOSIS
Asteroid hyalosis:
Calcium soaps
produce bright
point like echos
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Differentiation, extrascleral extension,
size, assessing tumour growth or
regression.
Measurement of tumour dimensions
such as elevation and base.
Help in distinguishing solid from cystic
lesions.
TUMOURS
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RETINOBLASTOMA
Size of the tumour
Shows irregular
configuration
Calcification
shows high
internal reflectivity
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MELANOMA
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Collar button or mushroom shape.Large tumours shows
acoustic hallowing
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TUMOURS - OSTEOMA
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CHOROIDAL DETACHMENTKISSING CHOROIDS
Smooth, thick, dome
shaped membrane in the
periphery with very littleafter movement
360 degree detachmentshows a pathognomonic
“scalloped appearance
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CHOROIDAL DETACHMENTKISSING CHOROIDS
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CHOROIDAL DETACHMENT
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Intraocular foreign bodies:
Localisation and extent of intraocular damage
Metallic foreign bodies produce very highbright signal
Shadow present posterior to the foreign body
Wood, glass and organic material producespecific echographic finding
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INTRA OCULAR FOREIGN BODY
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CUPPED DISC
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MACULAR EDEMA
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PERSISTENT HYALOIDAL VESSEL
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POSTERIOR STAPHYLOMA
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LACRIMAL GLAND TUMOUR
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NANOPHTHALMOS
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RETINOSCHSIS
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Retinoschisis:
Smooth, thin dome shaped membrane thatdoesn’t insert on optic disc
Diabetic retinopathy:
Nature and extent of the disease
To monitor progress of the disease Aids in pre – vitrectomy evaluation
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ENDOPHTHLMITIS
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CYSTICERCOSIS WITH RETINAL
TEAR
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COLOBOMA OF THE CHOROID
AND DISC
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PERSISTENT FETAL VASCULATURE
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RETINOPATHY OF PREMATUIRITY
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POSTERIORLY DISLOCATED LENS
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INTRA OCULAR AIR / GAS
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SILICON OIL FILLED VITREOUS
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Sclera:
Thickening in hyperopic and
nanopthalmic eyes
Infolding in severe hypotony or aruptured globe
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SCLERITIS
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Normal muscles show less echo dense thansurrounding orbital soft tissue
Documenting the gross size and contour of amuscle
’
Evaluation of extraocular muscles:
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Nodular posterior scleritis with fluid in the
Tenon capsule.Positive T-sign at the insertion of the optic nerve.
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Evaluation of optic nerve
General topography, relationship tostructures, optic disc anomalies andalteration in contour of the globe
The subarachnoid space surrounding
optic nerve appears as echolucentcresentric or circle around the nervecalled ‘Doughnut sign’
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Non invasive
Performed in an office settingDoes not expose to radiation
High resolution echography provides reliable
and accurate assessment Ideal for follow up of lesion
Advantages:
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Disadvantages
High frequency sounds waves have
limited penetration
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Useful in the following conditions:
Abnormal size of eye
Abnormal shape of eyeCongenital abnormalities
Vitreous alterations
Retinal detachments (type/ location)Ocular and orbital tumours
Trauma
ULTRASONOGRAPHY IN PAEDIATRIC PATIENTS:
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Artefacts:
Insufficient fluid coupling ( i.e., lack of methyl cellulose) cause entrapment of air between the probe and eye leadingto display of bright echos which
represent multiple signals
PITFALLS
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REVERBERATION ARTEFACTS
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ANGLE OF INCIDENCE ARTEFACT
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PITFALLS
Tumours:
Mass may be missed is less than 0.75
mm False –ve results in case of small
lesion and fibrotic tissue
False + ve in subretinal haemorrhageand metastatic tumour with massiveinfiltration
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Vitroretinal disease:
In RD unable to detect actual tear
In vitrectomsed eyes vitreous
haemorrhage is diffuse leading to
echolucency
Silicon oil decrease in sound velocity
PITFALLS
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PITFALLS
Intraocular foreign body:
Small Intraocular foreign body of < 1mm
may be missed.
Orbit:
An orbital mass can be detected or differentiated if > 3 mm in size if anterior and
> 5 mm in posterior orbits.
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B- SCAN REPORTING
Describe the features and correlate
with clinical findings.
Dont jump to diagnosis.
Always examine both in sitting and
erect postures in case of RD.
Examine other eye also.
Try to take the best picture possible.
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FOUR TRANSVERSE SCANS
ONE HORIZONTAL AXIAL SCAN TOEVALUATE THE POSTERIOR POLE ARE
SUFFICIENT.
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THANK YOU