B scan

B Scan Ultrasonography

1. B SCAN USG Presenter : Dr Samuel Ponraj

2. B-scan or brightness modulation scan provides two dimensional images of a series of dots and lines. B-scan provides the topographic information of shape, location, extension,mobility , and gross estimation of thickness of the tissue.

3. FREQUENCIES 1-2 MHZ : ABDOMINAL ULTRASOUND 8-10 MHZ : OPHTHALMIC ULTRASOUND (B SCAN) BEST FOR POSTERIOR SEGMENT 35- 80 MHZ : ULTRASOUND BIOMICROSCOPY BEST FOR CORNEA & ANTERIOR SEGMENT

4. PULSE ECHO SYSTEM TRANSDUCER AMPLIFIER DISPLAY MONITOR

5. AMPLIFIER MONITOR

6. TRANSDUCER Device which converts Electrical to Sound energy [pulse ] and Sound to Electrical energy [Echo] Basic Components – Piezoelectric plate Backing layer Acoustic Matching layer Acoustic lens

7. Piezoelectric Element : essential part generates ultrasonic waves . Coated on both sides with electrodes to which a Voltage is applied. Oscillation of Element with repeat expanding and contraction generates a sound wave. Most common: Piezoelectric ceramic ( Lead zirconate titanate ).

8. Backing layer : located behind the piezoelectric element which dampens excessive vibrations from probe thereby improves image resolution Acoustic matching layer : located in front of piezoelectric element which reduces the reflections from acoustic impedance between probe and object thereby improves trasmission .

9. Acoustic Lens : gray coloured rubber on tip helps in focussing the ultrasonic waves as a slit beam.

10. Frequency Resolution Penetration Possible Scanning depth High Fine Weak Shallow Low Rough Strong Deep

11. IMMERSION B SCAN CONTACT B SCAN

12. PROBE POSITIONING TRANSOCULAR APPROACH AXIAL TRANSVERSE LONGITUDINAL PARAOCULAR APPROACH

13. Standardized Echography ( Contact B Scan + A Scan) 3 Basic Positions :

14. VOCABULARY

15. Bell : Measurement of Sound Intensity Hertz : Frequency of transducer Acoustic impedence mismatch: - Resistance of tissue to passage of Sound waves. Difference of two tissues at the Interface. - Homogeneous ( Vitreous)- Sound passes through tissue with no returning signal. - Heterogeneous (Orbital Fat) - Different levels of Acousitc impedance mismatch within tissue.

16. Echo – Reflected Sound wave. Anechoic – No Echo. Attenuation : Sound is absorbed ( Tumours ) Shadowing : Sound is strongly reflected , nothing passes through it.( Choroidal Osteoma Drusen of Optic nerve head , Air bubble). Reverberation : Collection of Reflected sounds bouncing back and forth between tissue boundaries especially ( Foreign Body in Eyeball )

17. Ultrasound Velocity Normal Phakic eyes = 1555 m/s Aphakic eyes = 1532 m/s Pseudophakic eyes (PMMA) = 1556 m/s (Acrylic )= 1549 m/s Silicon Oil filled eyes = 980 m/s

18. Normal Ultrasonography Characteristics Lens :Oval highly reflective structure Vitreous : Echolucent Retina , Choroid , Sclera : Each is single highly reflective structure. Optic Nerve :Wedge shaped acoustic void in Retrobulbar region Extraocular muscles : Echolucent low reflective fusiform structure. Orbit : Highly reflective (Orbital fat)

19. Indications Opaque Media (Pathology of Posterior segment) Transparent Media

20. Opaque Media (Anterior) Dense Cataract Miosis Hyphaema Hypopyon Corneal Opacity Plan for Penetrating keratoplasty with Opaque Anterior segment.

21. Opaque Media (Posterior) Vitrous Haemorrhage Vitritis / Endophthalmitis Pupillary or Retrolenticular membrane

22. Transparent Media Acquisition of Axial Length for Highly Myopic surgical Candidates ( Caution for Posterior Staphyloma ) Inaccurate A – Scan data (Determination of dimensions of Eye ball) Proptosis ( Poorly represented Orbital Apex) Orbital tumours Carotico - cavernous fistula(Dilated Ophthalmic vein)

23. Cysticercosis of Extraocular Muscles Suspected Intra Orbital Foreign Body Orbital Cellulitis Iris & Ciliary body anomalies Optic Disc anomaly Retinal Detachment ( Rhegmatogenous / Exudati ve – shifting fluid) Choroidal Detachment.

24. HOW TO APPROACH A DIAGNOSIS ??

25. 1. Examination of each quadrant 2. Look at each quadrant - coronal - sagital 3. Mentally assemble the Cross sections 4.Anticipate how it should look on moving probe.

26. Pathological Ultrasongraphy characteristics

27. Multiple Fine Echo Opacities within the Vitreous Cavity suggestive of Vitreous Haemorrhage .

28. Multiple, densely packed, homogeneously distributed echodense dots of medium to high reflectivity with a Clear Preretinal space suggestive of Asteroid Hyalosis

29. Moderately elevated thin smooth dome-shaped membrane echo (arrow) located in the inferotemporal periphery suggestive of Retinoschisis

30. KISSING CHOROIDALS

31. Smooth, dome shaped , thick, less mobile with double high spike suggestive of Choroidal Detachment

32. PVD RD CD Topographic Smooth, with or without disc insertion Smooth or folded with disc insertion Smooth without disc insertion Quantitative < 100 % spike 100 % spike Double 100 % spike Kinetic Marked Moderate None

33. PVD or RD ? RD attached to the OD RD is high reflective RD is less mobile Rd is 100% amplitude Reflectivity of the periphery can differentiate between the two in difficult situations like trauma and inflammations .

34. Differentiating features of RD Rhegmatogenous RD Tractional RD Exudative RD Convex elevation , Undulating folds, PVR Concave elevation,Fibrous tractional band Convex elevation, Shifting fluid changes Configuration with postural change

35. RD configurations Open Funnel Triangular Closed funnel ( T shape)

36. Long standing RD Closed funnel RD with PVR Retinal cysts

37. Configurations of TRD Tent like ( point adherence ) Tabletop ( broad adherence ) Hammock appearance ( multiple tent)

38. Highly reflective, echo-dense nodule located in Vitreous Cavity suggestive of Cysticercosis .

39. Collar stud pattern ( Mushroom shape ) Regular internal structure , Acoustic shadowing Low to medium reflectivity , Internal vascularity suggestive of Choroidal Melanoma

40. Small globe , Retrolenticular membrane A Moderate Reflective band extending from the optic disc to the posterior lens capsule suggestive of PHPV .

41. Globular/Oval Echoic structure in Posterior Vitreous signifying a Dislocated Lens

42. T sign collection of fluid in subtenon space suggestive of Posterior Scleritis .

43. Posterior Staphyloma in High Myopia