this ppt is on basics of B scan

2.  1940 ultrasonic energy was used by Dr. George ludwig
 Ultrasound was first used in ophthalmology in 1956 by
Mundt and Hughes – A-Scan
 Oksala expanded the use of A scan for diagnosis of
intraocular disoredrs

3.  Baum & Greenwood – B-Scan in 1958
 Further pioneering was done by Purnell- immersion B-
Scan
 Coleman developed first commercially available B-
Scan.
 Bronson introduced first contact B-Scan
 Ossoinig emphasized standardization of instruments.

4.  It uses acoustic waves that consists of an oscillation of
particles within a medium.
 Ultrasound have frequency >20Hz.
 Ophthalmic frequency 8-10Mhz.
 Short wavelengths – better resolution.
 The longitudinal wave consists of alternating
compressions and rarefractions of molecules.
 Velocity is dependent on the medium.

8.  Waves behave similarly to that of light rays.
 Acoustic interfaces that are created at the junction of 2
media that have different acoustic impedance.
Wave travels
through tissue
Waves are
reflected back
To the source of
emitted energy
ECHO

9.  Transducer/probe
 Servo (for B-mode systems)
 Pulser
 Receiver
 Scan converter and display

10. Electrica
l energy
Piezo-
electrical
crystal
Quartz or
ceramic crystal
Mechanical
vibration
Longitudinal
wave
Propagates
through
media
Pause occurs millisec
Returning energy creates another
mechanical vibration
Electrical signal that is transmitted to rceiever
and converted to real time image on Display

11.  Ultrasound uses high frequencies of
>20,000cycles/sec.
 They have different velocity in each media.

12.  A signal undergoes a complex processing.
 Amplification, compensation, compression,
demodulation and rejection.

13.  Measured in decibels
 Turning volume up or down.
 It only changes the intensity of the returning echo.
 Higher gain – weaker echoes
 Lower gain – better axial and lateral resolution.

14.  A-mode Amplitude
 B-mode Brightness
 C-mode Similar to B-mode but done using a A-mode
line & moved in 2D plane.
 M-mode Motion mode.
 Doppler mode
 Pulse inversion mode
 Harmonic mode.

15.  Biometry A-Scan.
 Standardized A-Scan.
 Diagnostic B-Scan.
 Doppler Ultrasound.
 3D ultrasound.
 Ultrasound Biomicroscopy.
Standardized
echography

16.  Amplitude.
 One dimensional.
 Echoes are represented as vertical spikes from a
baseline.
 Two types
 Biometry
 Standardized

17.  2 fundamental data
 The distance of echo-source from the probe face –
Biometry.
 The amplitude of echo-signal which partly depends on
the nature of reflecting interface – Qualitative
echography.
 Spike height depends on
 Location and nature of echo-source.
 Energy gain and direction of sound beam.
 Sound impedance and beam scatter.

20.  Eight meridians are scanned postero-anteriorly from
limbus to fornix
 For vitreous opacities a higher gain is set.
 Lower gain for retino-choroidal layer.
 In traumatized and infected eyes it is done on closed
eyelids.
 Labelling is determined by projection of beam not on
the location of probe.

23.  Macular screening
 Axial section – cornea.
 Posterior section – RE9P LE3P
 Peripheral fundus
 Patients gaze is directed maximally towards the
meridian to be scanned.
 Probe is placed at the opposite fornix
 Smooth reinal spike becomes jagged

25.  BRIGHTNESS
 Two-dimensional acoustic section.
 Vertical and Horizontal dimensions of screen to
indicate configuration & location.
 Most of frequency range around 10Mhz.
 Echo is represented as a dot.
 Strength of echo as brightness of the dot.

27.  Eye dedicated scanners – focus both the posterior
globe wall and anterior orbit.
 Marker – beam orientation.
 Coupling jelly is required.
 Closed eyelids for infected & traumatized eyes
 Cling films used for endophthalmitis cases.

28.  Three fundamental objectives
 Lesions must be placed in the centre of the scanning
beam.
 The beam must be directed perpendicularly to the
interfaces at area of interest.
 Lowest possible db gain should be used.
 No T-sensitivity is needed.
 High gain is used for initial screening

29.  Lower the gain better the resolution.
 Routine from high to lower gain settings is
recommended.
 Higher grey scale deploys better diagnostic capability.
 Lesser scale better contrast.
 Anterior shift – the anterior segment is suppressed.

30.  Three basic sections are obtained from B-scanning.
 1 - Axial section.
 2 - Transverse section.
 3 - Longitudinal section.

31.  Easiest to perform and interpret.
 Pt fixates in primary gaze and probe is placed on
cornea and directed axially.
 Postr lens surface and ON – landmark.
 Sections of all clock hours can be performed mostly
performed for ‘upper clock hours’
 Easy orientation and demonstration.
 Lesions of ON head.

32.  Higher gain setting is required at the cost of image
resolution.
 Pseudophakic eyes hamper adequate visualization.

34.  The beam traverses many meridians.
 Lens is avoided.
 Probe is placed on limbus and directed posteriorly.
 In a arc movement it is shifted & rotated from limbus
to fornix.
 Postero-anteriorly.


35.  It is conventional to orient marker nasally or
superiorly.

37.  Antero-postero slice along 1 meridian only.
 ON to ciliary body.
 Probe is located on the sclera and directed nasally.
 Periphery and ciliary body are brought in view.
 Helps in demarcating antero-postero limits of lesions
and ON.

40.  Scans are performed 1st with high gain and then with
low gain..
 Then longitudinal and axial sections are performed.
 This helps in creating multi dimensional impressions.

41.  Macular screening
 Horizontal axial with marker nasally.
 Vertical macula – vertical axial is first produced and
tilted temporally.
 Transverse – RE-9 and LE-3 probe is placed on
corresponding limbus. It helps in vertical extent.
 Longitudinal – similar to tranverse. Gaze fixed
temporally and probe placed nasally. It helps in lateral
extension.

43.  Peripheral fundus
 Pt gaze is fixed maximally towards the meridian to be
examined.
 Transverse and longitudinal sections are taken by
scanning from opposite fornix.
 Probe can be directly placed over the lesion and initial
signal read.

46.  Topographic echography
 Shape
 Location
 Extension
 Quantitative echography
 Reflectivity
 Internal structure
 Sound attenuation
 Kinetic echography
 Mobility
 vascularity

47.  Topographic B-scan
Lesion is detected
Transverse B-scan
approach
Probe is shifted from
limbus to fornix in
sweeping fashion
Longitudinal
approach is applied
Beam is
perpendicular to
transverse section
Axial section is
preferred for ON
lesions

48.  Transverse section helps
 Gross shape
 Dimension
 Lateral extent of lesion
 Longitudinal section
 Antero-postero extent
 Along with shape and dimension
 Axial section
 Relationship to anatomical landmark

49.  Quatitative echography
 Reflectivity
A-scan is the
preferred
Gain setting is
done
Reflectivity is
determined
Estimating
height of spike
In relation to
baseline
Hence has
importance

50. Assessment of b-scan in determining reflectivity is
based on the signal brightness of the lesion
Lesions which are extremely echo-dense or
echolucent are best examined for reflectivity by B-
sacn
Hence A-scan is preferred over B-scan for reflectivity

51.  Internal structure
It refers to the histo-logic architecture of
lesion
On A-scan it is noted on the difference
b/n height and length of the spike
On B-scan based on the echo-density of
the lesion. B-scan is preferred.

52.  Sound attenuation
Occurs when sound energy gets scatterred
reflected or absorbed by a medium
A-scan the spike decreases called angle of
kappa
B-scan this is indicated by the brightness
of the echoes. The brightness decreases.

53.  Kinetic echography
 Mobility
 Aftermovement
 Vascularity
 Can be assessed by both B-scan and A-scan.
 A-scan preferred for spontaneous motion.
 The strength of A-scan is it can detect subtle motion.

55.  Refer to use of frequencies of >25 MHz.
 Pavlin and Foster 1990
 3-D acquisition of radiofrequency data and
 Wide angle scanning incorporating the entire anterior
segment
 Attenuation cannot be used for imaging of the
posterior segment
 Immersion technique

56.  Fivefold improvement in resolution compared to that
of 10-MHz images
 Anterior segment anatomy and
 Pathology such as corneal scars
 Tumors and cysts of the iris and ciliary body, ciliary
body detachment, glaucoma syndromes

57.  Detection of frequency shifts associated with tissue
motion
 Continuous wave
 Separate transducer is used to receive echoes
 Simultaneous display of a B-mode image with
superimposed color information indicating areas of
flow

58.  Immersion scanning and its use has regained its spot
with the use of VHFU.
 Earlier done for both A and B-scan.
 Scleral shells are used 16-24mm
 Coupling gel is needed.

59.  Graphic representation of flow by converting the
Doppler signals into positive and negative velocity
values
 Colored pixels representing flow are superimposed
onto the B-mode image.
 It is used for conditions which are associated with
 Central retinal artery
 Ophthalmic artery

60.  Intraocular details obscured from visualization by the
ocular media opacities.
 Retinochoroidal lesions especially tumors even with
clear media.
 Differentiation of solid from cystic and homogenous
from heterogeneous masses.
 Retrobulbar soft tissue masses and normally present
orbital structures

61.  Identification, localization and measurement of non
radioopaque/radio-opaque foreign bodies. Assessment
of collateral damage in trauma cases.
 Biometry and pachmetry.
 Follow up evaluations.