B-Scan

Ultrasound ( high frequency) will not travel through air ( Artifacts)

It must be "coupled" into the eye. Use generous amounts of methylcellulose or goniosol on the probe.

B scan provides

It provides information on the geography and geometry of ocular structures.

Asteroid Hyalosis

Looks like (calcium soaps dispersed throughout vitreous - usually doesn't obstruct vision) kinetic movement still present at increased attenuation

B- Scan measured in

MHz ( Megahertz)B-scan - 10 MHz MHz - shallow penetration (i.e., anterior segment); 12 MHz MHz - deeper penetration (i.e., orbital structures); 7 MHz Differential - vit heme vs. asteroid hyalosis (calcium deposits) - will reflect more, so if you turn down the gain, it will still reflect; vit heme will disappear with a decreased gain

Probe orientation

Marker on probe indicates the top of the display screen

Cases for for B-Scan

Vitreous hemorrhage (patient cannot see out, doctor cannot see in) Cataract Staphyloma Abnormally contoured globes prior to retrobulbar 5. Proptosis (screen extraocular muscles and orbit) Foreign bodies Trauma - determine status of globe

B-Scan are used to scan

all parts of the globe and orbit for evidence of pathology

B Scan probe can be used to

apply pressure to the globe during orbital tumor image. This can help determine if a mass is compressible. (Compressibility is another clue in determining diagnosis.

Bright echoes ( real time scanning b)

are strong reflectors and can be describedas coming from strong echo source

Real time Scanning ( b) : images move the same time

as the eye when it moves.

Range of intensities ( real time scanning b)

gives information about tissues

Retinal Detachment ( real time scanning b)

has an undulating restricted movement

Vascularity of lesion ( real time scanning b)

large melanoma - possible to see pulsations of vascular supply within tumor during real time scanning.

B Scan

two dimensional ultrasound images created by lighted dots of varying brightness.

By understanding the direction of the movement in the transducer

we can tell when the "fan" is being aimed vertically, horizontally, or another way.

Gray scale ( real time scanning b)

Gray scale = wide variety of intensities from black to white

Artifacts ( Air in the eye)

. Air in the eye a. Penetrating injury b. Pneumatic retinopexy procedure - gas injected into the eye to help reattach the retina Tough to tell air bubble in eye from foreign body like glass or metal. Air bubbles are strong reflectors. If bubble is large enough, it will cast a shadow behind it because sound cannot travel through it. Be careful not to mistake this for the optic nerve. With retinopexy, may have to move patient's head to different positions to get different scans away from the bubble. Sometimes bubble is too big and scan is not possible.

method of performing B-Scan

1. Closed eye contact 2. Open eye contact

Equipment and supplies

1. Fellow eye fixation target 2. Sterile methylcellulose 2.5% solution 3. Topical anesthetic 4. Alcohol preps 5. Tissues

Three main probe position

1. Longitudinal 2. Horizontal/Vertical transverse 3. Axial

Kinetic aspects of lesions: two types of motion ( a and b scan used together)

1. Mobility (after movement) - suggests that lesion is not solid. This could be a vitreous membrane or RD. Have patient look at fixation target; look away, than back to the target. The examiner watches the movement the entire time and notes in chart. 2. Vascularity (spontaneous motion) - movement while the eye is stationary suggests presence of blood or vascularity. A scan should be done especially if mass has blood flow. Have patient be very still. Put probe so beam goes directly through mass. Initial spike represents front part of the lesion. If the spikes that follow are blurred (because of movement) this suggests active blood flow.

A and B scan used together

After a mass is found, an A-Scan can be used to calculate size of the lesion, type of tissue involved, and/or Kinetic response. Examples: 1. Retinal Detachment: large spike followed by a small flat section along the base line followed by another tall spike. 2. Tumor: A-scan may reveal internal structure of tumor. Large spike at tumor followed by steep decline if structure is all the same. If different inside, sound velocities will cause large initial spike followed by other large spikes.

Artifacts any air bubbles

Any air bubbles will decrease sensitivity. Air in the gel causes a noisy image in the anterior aspect of the globe as well as reduced sound energy to the posterior tissues. Store containers of gel upside down.

ARTIFACTS

Artifact is created by some type of reverberation or distortion of the sound beam.

What are B-Scan

B Scan has curved parts B = Brightness eyeBall is round = curved parts B scan - provides a 2D view of retina when we can't see in the back of the eye.

Topographic ( B-Scan)

B-scan - insertion, growth, localization, shape)

Foreign Body

B-scan shows reflective "trailing echo" seen behind spherical FB can also shows damage to eye from FB often shows path of injury

Baums Bumps ( artifacts)

Decreased gel or incomplete contact will produce "Baum's Bumps" or rib-like echoes. (ex: most of gel is in the center of the lid, and when sound travels to the periphery, it is now at a different speed due to lack of gel)

Dim echoes ( real time scanning b)

Dim echoes come from weak echo sources

Foreign Bodies - present different artifact echos. You can tell the material by the artifact in many cases.  Two categories for artifacts created by foreign bodies:

Extra echoes generated: glass or metal produced extra echoes just behind it. Process is called "reduplication". B. Lack of echoes posteriorly - called a "shadowing artifact".

examination

Place probe directly on eyelid. Have pt open other eye for fixation. Make sure WHITE DOT on probe is held NASALLY or SUPERIORLY. This will ensure that whatever the white dot points to will be seen superiorly on the screen (i.e., the macula will always be below the optic nerve - for orientation). Hold probe perpendicularly for max spike height. 4. Trying to see and understand 3D from 2D view. Remember perspective, screen shows tissue opposite probe. Depending on probe position, think how you could be "sectioning" tissue (cutting through lesion - ex: funnel-shaped lesion

LESIONSTopographic lesion

Point-like - vitreous floater, foreign body A-scan - single spike, decrease sound below tissue sensitivity, any reflection is from foreign body (ex. Asteroid hyalosis) Spherical FB - reverberation of wave - 1st signal is anterior surface vitreous floater - small low reflective with movement

How does a B-scan work

The B-scan is made up of multiple A-scans. Inside the B-scan probe there is an A-scan that rotates up and down in an arc. The A-scans are "stacked" to form a two-dimensional display. The strength of the reflected signal is represented by a bright dot instead of a spike along the baseline. The stronger the signal, the brighter the dot. The "B" in B-scan stands for "brightness display".

Longitudinal Probe Position

The probe is placed on the bulbar conjunctiva on the opposite side of the globe from the area of interest (left image above). The sweep of the probe is perpendicular to the limbus. The mark is always oriented toward the limbus. The top of the screen is the far periphery, and the bottom of the screen is the posterior pole. The probe can be shifted toward the limbus or toward the fornix to center pathology in the center of the screen.

Transverse Probe Position

The probe is placed on the bulbar conjunctiva on the opposite side of the globe from the area of interest. The sweep of the probe is parallel to the limbus. The mark is oriented either superiorly or nasally, depending upon the area of the retina being scanned. The transverse position is always a 90 degree rotation from the longitudinal position for the particular area being viewed. The photo below/left is of a right eye, so the correct label is T900.

Axial Probe Position

The probe is placed on the corneal apex, pointed toward the posterior pole, in any clock hour position. OD A300 or OS A900 will give an image of the posterior pole with the optic nerve at the top of the screen and macula in the center of the screen. . **Clinical evaluations of the retina are never made when scanning through the lens. They are made using transverse and longitudinal scan angles**.

How does a B-scan work (cont)

Transducer - piezoelectric material (converts electrical energy into mechanical energy and vice versa) Oscillations allow for transmitting and receiving data wavelength - unit = mm distance between crest to crest in ocular tissues, the wavelength = 0.2

Acoustic Section

Transducer inside oscillates and forth, toward and away from this mark. Generates a "fan of sound waves"(like the slit lamp beam).

ULTRASONOGRAPHY - "echography

detect and locate lesions localize and measure differentiate lesions follow progression decide approach for biopsy detect re-growth

Kinetic ( B-Scan)

looking for moving things in eye, i.e., floating membranes, etc - like looking at vitreous hemorrhages or images seen fundus photos

Generally examination

membranous structures still present at high system attenuation point-like lesions disappear at fairly low attenuation high mobility (usually) of point-like structures moderate mobility (usually) membranous structures (vit mem - highly mobile, but could disappear at increased attenuation) The levels of brightness coincide with various tissues.

Internal reflectivity ( real time scanning b)

reflection inside lesion (gain can also cause this)

Vitreous Hemorrhage

sheet-like echo, similar to RD, seen with partially or complete RD weak reflectivity and disappears with increased attenuation (decreased sensitivity) no attachment to optic nerve head (usually) kinetic movement (after- movements) gravity dense vitreous hemorrhage and may have sheet-like attach, may look like RD, but have slightly high reflectivity, NOT high like RD