B Scan Ultrasonography01

B- Scan Ul tras onogr aph y Guide:

Dr. S. S. Kubre Presented by:

Dr. Samreen Arif

RSO- Ophthalmology Gandhi Medical College.

Introduction : 

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Ultrasonography of the eye is an indespensible tool in the diagnosis and management of various ocular and orbital abnormalities It was first used in ophthalmology in 1956 by Mundt and Hughes as A scan Baum and Greenwood introduced first Bscan in 1958 and first commercially available B-scan was developed Coulmn et al in the seventies

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Physics : 

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Ultrasound is an acoustic wave that consists of oscillations of particles within a medium, the waves have frequency greater than 20khz(20,000 oscillations/sec) Diagnostic ophthalmology utilizes frequency of 8-10Mhz (1Mhz=1,000,000cycles/sec)

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Basic elements of ultrasound 

Pulser

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Transducer

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Receiver

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Display

Modes of display 

A scan or amplitude modulation scan

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B scan or brightness modulation scan

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Vector A scan

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Three dimensional ultrasound tomography 4

Ele ct ri c Curren t

Multip le Sho rt Puls e w ith brief in ter val be twe en th em

Lead Zirco nate ti tanate C rystal

Lo ngitu din al Ultras ound W av e Propogated through medium

Elec tri cal Si gn als

Re ceiv er

Transd uce r

Echoes Produced

Display ed on Sc ree n

Tiss ue Ultra soun d Inter action •

Reflection

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Refraction

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Scattering

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Absorption 5

Modes of display A-Sca n /Amp litu de Modu lati on Sca n 

It is a one dimensional acoustic display

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B-Sca n / Bri gh tn ess Mod ul at ion Sca n 

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It provides a real time, two dimensional, grey scale display of the eye and the orbit, where different echodensities are depicted in gradations of brightness Echoes are represented as dots and there strength as brightness of dots on the screen

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Vector A Scan: 

It is the combination of both A Scan and B Scan

Thr ee di mens ion al ul tras ou nd tomog ra phy: 

It utilizes ultrasound technique and digital computer technology where ocular pathology can be viewed in three dimension

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Modes of B-scan 

Low frequency:

Useful in detecting orbital pathology 

Moderate frequency:(7-10MHZ)

Useful in globe examination 

High frequency:(30-50MHZ)

Useful for imaging anterior segment Penetration depth of 5 -10mm 

Immersion technique:10MHZ

Useful for evaluation of anterior chamber Uses sceleral shell filled with methyl cellulose 9

Screening technique 

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It is best to begin with maximum gain on B scan Eye is anesthesized with topical paracaine if transducer is kept on sclera Alternatively eye need not to be anesthesized if probe is kept on close eyelid Probe is placed on the globe opposite to the area examined Marker on the probe act as the orientation point 10

Techniques used for Evaluation Transverse technique  Horizontal transverse:Evaluate superior and inferior fundus and marker is kept towards nose  Vertical transverse:Evaluate the nasal and temporal fundus and marker is kept towards 12 o’clock  Oblique transverse:Evaluate the pathology not located at major meridians (3,6,9,12 o’clock)

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Techniques used for Evaluation Axial technique 

Horizontal: marker towards the nose

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Vertical: marker towards 12o’clock position

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Techniques used for Evaluation Longitudinal technique 

Evaluate single meridian from its most posterior aspect to far periphery

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Once the cross sectional examination is completed area of interest is scanned by longitudinal scan

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INDICATIONS Anterior Segment a. Opaque ocu lar me dia •

Pupillary membrane

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Dislocation/subluxation of lens

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Cataract/after cataract

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Posterior capsular tear in traumatic cataract

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Pupillary size/reaction

b. Clea r ocu lar med ia •

In diagnosis of suspected iris and ciliary body tumours 14

Posterior Segment a. Opaque ocu lar me dia • • • • •

Viterous haemorrhage Viterous exudation Retinal detachment (type/extent) Posterior viterous detachment (extent) IOFB (size/site/type)

b. Clea r ocu lar med ia •

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Tumour (size/site/post treatment follow up) Retinal detachment (solid/exudative) Optic disc anomalies 15

Biometry 

Preoperative scanning and calculation of IOL power

Orbital Examination 

Exophthalmos

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Motility disturbances/diplopia

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Palpable orbital mass

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Optic disc oedema and atrophy

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Syndromes (superior orbital fissure/orbital apex)

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NORMAL EYE ON B-SCAN

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NORMAL EYE ON 

B-scan

It reveals two ecographic areas seperated by an echo free area

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Echographic area at the beginning represent reverberation at the tip of probe and has no clinical significance

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On high resolution scan posterior convex surface of lens can be seen

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Large echo free area represent viterous cavity Vitero retinal interface forms a smooth curved curvature. Echoes from retina, choroid and scelera merge Scleral fat boundry is well seen acoustically Orbital fat is seen as highly refractile mass with the extra ocular muscles forming outline of the fat

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Viterous haemorrhage Bscan: seen as small white echoes    

Fresh and diffuse heamorrhage:little echo response Location:within PVD,pre and post hyaloid Extent Associated fibrous changes

Ascan: low amplitude spikes

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Endophthalmitis 

B-scan: Multiple small echogenic opacities with distinct after movements,in severe cases membrane formation . Associated findings:choroidal thickening,choroidal detachment,retinal detachment,retained IOFB

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A-scan: chain of low amplitude spikes

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Retinal tear 

B-scan:

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A-scan:

appear as breach of tissue

highly refractile tissue seperated from other fundus spikes

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Retinal detachment B-s ca n : 

Recent : bright continuos,somewhat folded appearance,mobile retina and translucent subretinal space

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Retinal detachment B-s ca n : 

Proliferative viteroretinopathy: limited viterous space,decreased mobility of retina,funnel shaped(open or close) configuration of detached retina. In triangular RD the sides of triangle represent highly detached stiff retina and base is the proliferating viterous membrane

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Retinal detachment 

Longstanding RD may develop retinal cyst and become partially calcified and subretinal space filled with cholestrol debris

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Retinal detachment Tra ct ion ret in al det ach men t:  

Viteroretinal traction bands: focal/broad Concave configuration of detached retina

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Retinal detachment Exu dati ve re ti nal de ta ch ment: 

Configuration of the detachment is convex and bullous

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Retinoschisis 

Bscan :smooth thin dome shaped membrane that does not insert on optic disc

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Ascan : 100% high spike is produced

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Posterior viterous detachment 

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Bscan:

undulating membrane in front of retina showing movement with movement of eye and brightness is reduced with reduction of gain Ascan: tall spikes

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Choroidal detachment B-scan : 

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Smooth, dome shaped membranous structure that does not insert on optic nerve May be localised or involve entire fundus(kissing choroidal detachment)

A-scan : 

100% reflective ,double peaked spikes(retina and choroid)

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Intraocular foreign body 

Metallic foreign body: very bright signals that persist on lowering gain, shadowing artefact can be seen on adjacent orbit

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Non metallic foreign body: more challenging, produce bright signals

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Dislocated lens 

Round or oval globular structure in posterior viterous and strand of viterous may be attached to dislocated lens

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Posterior globe rupture 

Breach of sceleral and choroidal tissue with associated choroidal thickeninig

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Optic nerve avulsion 

Acute injury: actual peripapillary sceleral break , viterous haemorrhage may be present

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Longstanding cases: proliferative tissue at optic disc

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Retinoblastoma 

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Bscan: large irregular ecogenic mass involving viterous, retina or the subretinal space with area of calcification seen as area of high ecogenicity Axial length is either normal or increased Ascan: high internal reflectivity due to areas of calcification

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Choroidal naevus 

Localized flat or slightly elevated lesion with high internal acoustic reflectivity; a low internal reflectivity on A scan is suggestive of malignancy

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Osseous choriostoma 

Highly reflective anterior surface with orbital shadowing

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Choroidal melanoma 

Acoustic hollowness, choroidal excavation and orbital shadowing

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Collar stud configuration is almost pathogonomic (when tumour breakthrough the bruchs membrane)

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Choroidal haemangioma 

Acoustically solid lesion with the sharp anterior surface and high internal reflectivity but without choroidal excavation and orbital shadowing

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Metastatic choroidal carcinoma 

Appear diffuse, typical bumpy and irregular contour with central elevation

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A scan: irregular spikes of medium to high amplitude

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Asteroid hyalosis 

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B-scan:bright round signals showing movement with movement of eye with eco free space just in front of retina Ascan:medium amplitude spikes

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Cysticercosis B-scan : 

Sharply outlined oval cyst within viterous cavity or in the subretinal space

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Scolex seen as highly reflective ecodense nodule located adjacent to inner wall of cyst

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Posterior sceleritis 

Sceleral thickening, sceleral nodules, fluid in the tenon space give rise to “T sign”

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Phthisis bulbi 

Smaller globe with multiple ecogenic viterous opacities,choroidal thickening, calcification of ocular coats with resultant absence of high reflective orbital ecospikes due to shadowing

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Atrophic bulbi 

Normal globe contour with normal axial length and calcification of ocular coats

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Choroidal coloboma 

Excavation of posterior pole with sharp edges

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Associated features: microphthalmos and retinal detachment

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Posterior staphyloma 

Shallow excavation of posterior pole with smooth edges in highly myopic eyes

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Optic nerve drusen 

Calcified nodules that produces echoes of high reflectivity at or within optic nervr head

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Best seen by transverse and longitudinal approach that bypass lens

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Immersion technique Iris melanoma

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High resolution B scan Ciliary body detachment 

Large cleft seen in subciliary space

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High resolution B scan Iri s me lanoma

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Shortcomings of B-scan  

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Artefacts: Insufficient fluid coupling causes entrapment of fluid between probe and eye leading to bright echoes IOL may act as foreign body Tumours: Mass <0.75mm may be missed Viteroretinal disease: In retinal detachment usually the actual tears may be missed

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Shortcomings of B-scan   

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Intraocular foreign body IOFB <0.5mm can be missed Reflectivity of wooden foreign body can be decreased with time Orbit Orbital mass cannot be differntiated or detected if <3mm in size in anterior and <5mm in size in posterior orbit Biometery Wrong axial length may be obtained if probe does not aligned with optical axis,indentation of cornea,fluid meniscus in front of cornea 52

Contraindications of B-scan 

Recent surgery

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Open globe injury

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Active infection of ocular surface

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HIV infection

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