B SCAN ppp

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B – SCAN ULTRASONOGRAPHY

Dr. Parameshwar RaoDr. HaridevDr. AshokDr. Siva Kumar.W (PG)

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.

B- SCAN is a two dimensional imaging

system which utilises high freq soundwaves ranging from 8-10 MHz.

B stands for bright echoes.

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

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

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

sound waves from

transmitter

Echoes are received

by receiver

Amplification

Oscilloscope screen

Target tissue

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

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.

HIGH FREQUENCIES - LOW

PENETRATION BUT GOOD

RESOLUTION.

(abdominal US-1-2MHz )

INCREASE IN GAIN - INCREASE IN

TISSUE PENETRATION AND

SENSITIVITY – DECREASE IN

RESOLUTION.

INCREASE IN GAIN - INCREASE IN TISSUEPENETRATION AND SENSITIVITY – DECREASE IN

RESOLUTION.

DISPLAY MODES: A SCAN/ B SCAN /

TIME GAIN COMPENSATION: to

enhance echoes from deeper structures.

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)

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

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

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:

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

Image documentation modes :

They are of 2 types

stationary/static

moving/dynamic

The images may be saved in different

methods

1. Polaroid photographs

2. 35 mm photo

3. Ink prints

4. Thermal prints

5. Videotapes

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:

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

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:

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 .

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.

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

NASAL AREA TEMPORAL AREA

SUPERIOR AREA INFERIOR AREA

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 .

Axial scan

EYE anaesthetised.

EYE – in primary gaze

PROBE – centered on the cornea .

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.

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.

ORBIT -highly reflective due to orbital

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

Anterior segment evaluaton

Immersion technique

High resolution technique

ULTRASONOGRAPHIC

CHARACTERISTICS

VITREOUS HAEMORRHAGE

To detect extent,

density, location and

Fresh haemorrhage

shows dots or lines

Old haemorrhage

the dots gets

brighter

POSTERIOR VITREOUS DETACHMENT

Posterior vitreous

detachment:

The detachedposterior vitreous

is seen as

membranouslesion with

no/some

attachments to the

o tic disc

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

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

EXUDATIVE RETINAL DETACHMENT

RHEGMATOGENOUS RD

RHEGMATOGENOUS RETINAL DETACHMENT

CLOSED FUNNEL RD WITHRETINAL CYST

APPEARS AS RD BUT IT IS A PVD.

CLUES: NON UNIFORM THICKNESS OF MEMBRANE

VERY THIN ATTACHMENT TO THE DISC.

RETINAL TEAR

RETINAL TEAR WITH FREE SUPERIOR END .

THE MEMBRANE IS CONVOLUTED ON ITSELF.POSTERIOR VITREOUS IS ATTACHED AT THE

SUPERIOR END OF THE TEAR.

ASTEROID HYALOSIS

Asteroid hyalosis:

Calcium soaps

produce bright

point like echos

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

RETINOBLASTOMA

Size of the tumour

Shows irregular

configuration

Calcification

shows high

internal reflectivity

MELANOMA

Collar button or mushroom shape.Large tumours shows

acoustic hallowing

TUMOURS - OSTEOMA

CHOROIDAL DETACHMENTKISSING CHOROIDS

Smooth, thick, dome

shaped membrane in the

periphery with very littleafter movement

360 degree detachmentshows a pathognomonic

“scalloped appearance

CHOROIDAL DETACHMENTKISSING CHOROIDS

CHOROIDAL DETACHMENT

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

INTRA OCULAR FOREIGN BODY

CUPPED DISC

MACULAR EDEMA

PERSISTENT HYALOIDAL VESSEL

POSTERIOR STAPHYLOMA

LACRIMAL GLAND TUMOUR

NANOPHTHALMOS

RETINOSCHSIS

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

ENDOPHTHLMITIS

CYSTICERCOSIS WITH RETINAL

COLOBOMA OF THE CHOROID

AND DISC

PERSISTENT FETAL VASCULATURE

RETINOPATHY OF PREMATUIRITY

POSTERIORLY DISLOCATED LENS

INTRA OCULAR AIR / GAS

SILICON OIL FILLED VITREOUS

Sclera:

Thickening in hyperopic and

nanopthalmic eyes

Infolding in severe hypotony or aruptured globe

SCLERITIS

Normal muscles show less echo dense thansurrounding orbital soft tissue

Documenting the gross size and contour of amuscle

Evaluation of extraocular muscles:

Nodular posterior scleritis with fluid in the

Tenon capsule.Positive T-sign at the insertion of the optic nerve.

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’

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:

Disadvantages

High frequency sounds waves have

limited penetration

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:

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

REVERBERATION ARTEFACTS

ANGLE OF INCIDENCE ARTEFACT

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

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

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.

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.

FOUR TRANSVERSE SCANS

ONE HORIZONTAL AXIAL SCAN TOEVALUATE THE POSTERIOR POLE ARE

SUFFICIENT.

THANK YOU

B SCAN ppp

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