1. ULTRASOUND – THE BASICS
Dr. S. Parthasarathy
MD, DA, DNB, Dip Diab.MD ,DCA, Dip software based statistics,
PhD (physiology) FICA

2. Echo
IF WE GO TO A BAD HALL , THE SPEAKER ‘S VOICE WILL COME BACK TO YOU
WE CANT HEAR ANY THING
WHAT DO WE CALL THIS ?
Echo

3. In ultrasound The same thing The machine sends waves ,
it echoes from our tissues
Comes back to the machine
Converted to digital display for us to see
But it is ultrasound waves – not sound

4. Pulse echo principle

5. Frequency 20 KHz – man Just above range – cats , dolphins hear ??
frequencies used clinically lie largely between 3 MHz and 15 MHz.
There are no naturally occurring sources or detectors of such waves

6. Two main uses
Regional anesthesia
Vascular access
Safety
Efficacy

7. To generate the ultrasound
an electrical current is applied to the crystal (piezo electric) component within the transducer face.
current is then converted to mechanical (ultrasound) energy and transmitted to the tissues at very high (megahertz) frequencies.
The ultrasound energy produced then travels through the tissues as pulsed, longitudinal, mechanical waves

8. In echo Mouth speaks and ears hear the reflected waves
One machine part does it
Transducer
One reflector and one receiver – not enough
So waves are continuously sent from many transducers !! – ARRAY

10. Phased - Linear –curvilinear- arrays

11. Phased
Phased arrays are ideally suited to applications with small access windows, e.g., scanning the heart while avoiding the lung field.

12. linear, curvilinear, and phased
Linear arrays - rectangular field of view
suited to applications with reasonable access and a need to cover a lot of tissue close to the surface.
Curvilinear arrays rely on being able to apply some pressure to the skin surface in order to make it deform to their shape.
Once done , a very wide field of view can be obtained.

13. A single probe from 3 – 13 Mhz
Patient mode
Vascular
Nerves
Small parts

14. 3 - 10 MHz 8- 10 – superficial structures 5- 8 – medium distance
3 – 5 – deeper structures

15. Sound travels –speed m/s 1540 for all scanners

16. Higher frequency energy is ‘lost’ to the tissues to a greater extent than lower frequency energy with progressive tissue penetration.
Irrespective of frequency, lateral and axial resolution always decrease with increasing tissue depth
Lateral – perpendicular to the USG beam
Axial – parallel to USG beam

17. Selecting transducer Probes
Frequency
Array
Foot print or the diameter of the transducer
Attenuation ?

19. Hyperechoic - solids – liver – stones Hypoechoic – vessels
Continuous echoes
20 frames /second

20. Hypo and hyper echoic

21. Anechoic and iso echoic

22. Artifacts Something is there but not seen
Some thing is not there but seen
Acoustic
Enhancement
Reverberation
Three types

23. Acoustic Shadowing occurs when structures that are highly attenuating of ultrasound
energy (such as bone)

24. Nerves !! Near subclavian or enhancement artifact
Passes through structures of different attenuation
The deeper one may show more reflections and enhanced image
Nerves !! Near subclavian or enhancement artifact

25. Reverberation artifact
Each successive ultrasound pulse emitted from the transducer produces a temporal ‘echo’ resulting in a series of parallel lines both above and below the actual object.
commonly seen with highly attenuating wide-bore needles

26. Beyond the transducer From the transducer – we have to get the image
Which is meaningful !!
Put the probe – assess the image – assess which is marker side
Use gain and depth !!

28. Low gain

29. Brightens everything to compensate resolution
Medium and high gain
Brightens everything to compensate resolution

30. Time gain compensation

31. Depth Interscalene – 2 cm Femoral 4 cm
The resolution will decrease as soon as the depth goes

32. B and M modes A and B are static C and D are moving B = brightness
M = motion (cardiac)

34. Why use gel ?? Coupling Agent Ultrasound does not travel through air
Gel provides medium for sound wave into the body by removing air gap
Povidone-iodine, surgical spirit

36. Colour doppler
Select doppler and select site

37. In Colour Doppler mode,
blood flow towards the transducer will be red on screen,
flow away from the transducer will be blue on screen.
It must be emphasized that colour does not necessarily characterize arterial or venous flow.

38. Anechoic lumen, non-pulsatile, compressible
Anechoic lumen, non-pulsatile, compressible. Valsalva effect, doppler - continuous flow
Short axis

39. Anechoic lumen , pulsatile, non-compressible. Doppler - pulsatile flow
Long axis

40. Tendon
Hyperechoic with bright lines longitudinally or bright dots at right angles -fibrillary pattern

41. Hypoechoic with multiple hyperechoic lines muscle

42. Nerve

43. Liver normal and cirrhosis

44. Normal kidney and kidney stone

45. Save clip , record , patient ,type
Name
Age sex
Type of scan
---- done
Save clip , photo ,
Review , list

46. Caliper This is used to measure a distance (eg kidney length).
It is used by selecting a starting spot by pressing a kidney key and using the trackball to measure to a second mark.
The distance between the two marks will then be displayed on screen measured in cm. This can be used with other functions such as Res/Freeze.
Freeze – caliper – mouse fix point – mouse another point – distance will be shown.

47. Knobology Trackball ( mouse with select buttons)

49. Zoom magnification of areas of the ultrasound picture.
Looking at Res/Zoomed areas of interest has the advantage of a more detailed view
drawback of less anatomy visible

50. Movements of the transducer
sliding,
tilting,
rotating,
angling.
To create an image

51. orient the transducer such that the left and right sides are consistent with the left and right sides of the ultrasound screen,
position the plane of the screen similar to the plane of the transducer
Sample survey of the area

52. Tilting, rotating and angling

53. Slightly give tilting motion to the transducer – get the target to 90*
Anisotropy

54. Rotation from short axis to long axis

55. Angling
Gentle pressure may be applied to one side of the transducer to maintain full contact along the skin surface in concave or confined fields, or when attempting to direct the beam under a superficial highly attenuating structure such as bone.

56. Focus Lateral resolution better
Different echoic structures – better seen
Some machines if we adjust depth focus is automatically changed
Beam width decreased

57. Future developments

58. Two probes in one

59. Three-dimensional probes
. Needle tips which emit an ultrasound signal that is detected by the probe and visualized as a pulsating spot

60. Summary Ultrasound –echo , array , types frequency , speed, focus
Depth
Movements of the transducer
Artifacts
gain and TGC– B and M modes
freeze , caliper , trackball
Future developments