1. Ultrasound

2. Ultrasound – What is it? Ultrasound
Sound waves beyond the limit of human hearing
Frequency of Diagnostic Ultrasound
Non-invasive diagnostic tool used to compliment other imaging forms

3. Uses and Benefits of Diagnostic Ultrasound
Image the heart in motion and its valves
Image the liver and its internal structure
Image the Urinary bladder and measure its thickness
Look at the kidneys
Intestines in motion
Measure the thickness of the intestines
Do pregnancy checks and check the fetuses
Etc……

4. Uses and Benefits of Diagnostic Ultrasound
Pain free procedure
Generally no anesthetic needed
No harmful side effects
Able to see through the skin and look at organs
See organs in motion
Can measure the size of the chambers and valves of the heart as it beats
Etc…..

5. Sound Waves Wave of energy must be transmitted through a medium
Travel through medium while transferring energy
They travel back to the transducer, are analyzed, and are displayed on the screen

6. Sound waves
Described by their
Frequency
Wavelength
Velocity

7. Physical Properties - How do sound waves work?
Frequency
2-15 MHz in ultrasound

8. Physical Properties - How do sound waves work?
Wavelength

9. Physical Properties - How do sound waves work?
Frequency and Wavelength
Inverse relationship
Affects the choice of frequency used in each patient
High frequency
Low frequency

10. Physical Properties - How do sound waves work?
Velocity
Time required for a wavelength to pass a given point
Independent of the frequency
Changes depending on the medium it is traveling through

11. Physical Properties - How do sound waves work?
Velocity - continued
Eg: velocity of sound is 331 m/sec in air and 4,080 m/sec in bone
Within soft tissue of the body it is steady at 1,540 m/sec
This medium - dependent variation affects the ultrasound image produced
Velocity (m/sec) = Frequency (cycles/sec) x Wavelength (m)

12. Image Production Piezoelectric effect
Explains how ultrasound is generated from ceramic crystals in the transducer
An electric current passes through a cable to a transducer and is applied to the crystals causing them to vibrate
This vibration produces the ultrasound beam
The frequency of the ultrasound waves produced is determined by the crystals in the transducer

13. Image Production Pulse-echo Principle
Explains how the image is generated
Between pulses, the ultrasound beam enters the patient and is bounced back to the transducer
The crystals vibrate and produce an electrical signal that is converted to an image on the monitor

14. Interaction with tissues
Ultrasound produced by the transducer interacts with different tissues in a variety of ways
Attenuation
Refraction

15. Interaction with tissues
Attenuation
Caused by
Reflection
Scattering
Absorption of sound waves
Compensated for by use of specific controls

16. Interaction with tissues
Attenuation
Reflection (echo)
Occurs when ultrasound waves are bounced back to the transducer for image generation
The portion reflected is determined by the difference in acoustic impedance between adjacent structures

17. Acoustic impedance
Describes the ability of sound to penetrate a material
Related to density
Speed of the sound (velocity)
Fraction that is reflected
how different the 2 materials are
More difference in impedance = more sound reflected
Air vs water
Very different impedance
Almost entirely reflected
Only a small amount of sound waves enter the water

18. Interaction with tissues
Attenuation
Scattering
The redirection of ultrasound waves as they interact with small, rough, or uneven structures
Occurs inside the organs, and is responsible for
Increases with higher frequency transducers

19. Interaction with tissues
Attenuation
Absorption
Occurs when the energy of the ultrasound beam is converted to heat
Only process that directly removes energy from the ultrasound waves

20. Interaction with tissues
Refraction
Occurs when the ultrasound beam hits a structure at an oblique angle
The change in tissue density produces a change in velocity causing the beam to bend or refract
Altering the beams direction
This type of tissue interaction causes artifacts
Distinct shadow appears below lateral edges of fluid filled structures

21. Interaction with tissues
Refraction – generates several artifacts
Edge shadowing
Distance enhancement

22. Terminology Echogenicity Anechoic Hyperechoic – more echoes
Hypoechoic – fewer echoes
Isoechoic

23. Least echogenic to most echogenic
Renal medulla
Liver
Renal cortex
Spleen
Prostate
Renal sinus fat

24. Artifacts Reverberation Shadowing Acoustic enhancement
Refraction/edge artifact
Mirror-image artifact

25. Reverberation
Occurs when beam hits a highly reflective tissue interface
Entire beam is reflected back to transducer and it gets reflected back into patient
Hits interface again and repeats
Appears as a set of bright parallel lines

26. Acoustic Shadowing
Occurs because of inadequate penetration by the sound beam
In a highly reflective or sound-absorptive substance
Area of darkness
Occurs deep to dense material

27. Refraction/edge artifact
Hypoechoic band at the margin of a curved structure
Bending of the sound beam due to oblique angle
Edge artifact helpful in ID smooth round structures
Early pregnancy vesicles

28. Distance enhancement
When beam passes through an area with low attenuation

29. Display Modes
Information generated from an ultrasound examination can be displayed in a variety of ways, called modes. The mode used for display depends on the type of ultrasound unit used, the information to be obtained, and the organ being examined.

30. Display Modes A (Amplitude) Mode Used in ophthalmology
Not used much anymore

31. Display Modes B (Brightness) Mode
Echoes are represented as dots on a line that form the basis for a two-dimensional image
The returning echo’s location on the axis is based on the amount of time it takes for the ultrasound wave to be transmitted and reflected
Echoes in the near field (close to the transducer) take less time than those far away

32. Display Modes Real-time B (Brightness)Mode
Allows a complete, two-dimensional, cross-sectional image to be generated by using multiple B-mode lines
The transducer sweeps many times a second producing a new complete image
Several sweeps are performed each second producing a “real time” image

33. Display Modes M (Motion) Mode Used in echocardiography
Allows the sonographer to measure the heart to assess cardiac function and chamber size
Uses a single B-mode line

34. Doppler Echocardiography
Assesses turbulence and velocity of red blood cells within a vessel by measuring the doppler shift
Color is added to better detect subtle abnormalities
Evaluates pulmonic, aortic, mitral, and tricuspid valvular insufficiencies
Evaluates stenosis and congenital heart defects such as VSD and PDA

35. Image optimization
Transducers – classified according to the arrangement (array) of the crystals and the shape of the imaging field produced on the monitor
Linear
Sector

36. Image optimization Linear transducer
Provide superior resolution of near-field structures
Commonly used in equine reproduction and tendon examinations
Limited use in cardiac and abdominal studies

37. Image optimization Sector transducer Curvilinear array
Produces a fan-shaped image
Narrow near-field, broad far-field
Helpful in imaging deeper structures
Useful in small animals and cardiac exams

38. Image optimization Convex/microconvex
Compromise between linear and sector
Good resolution, pie shaped field

39. Image optimization
To obtain the best resolution, it is recommended to use the highest-frequency transducer that will penetrate to the desired depth. In general, a 3.5-MHz probe will be needed in large dogs, a 5.0-MHz probe in medium dogs, and a 7.5- to 10-MHz probe in small dogs and cats, depending on the type of study being conducted.

40. Image optimization Care of transducer
If using in large animal use protective covering

41. Unit Controls Power control
Alters the intensity of the ultrasound beam
Alters the amount of voltage that is delivered to the crystals

42. Unit Controls Gain Control
Alters the brightness of all the echoes on the monitor
Ultrasound waves are attenuated
If didn’t have this control there would be a light to dark gradient from near to far field
Gain Compensation Control
Allows the sonographer to adjust the amplification at various depths

43. Unit Controls Depth Control Controls the depth of the image display
Scale on 1 side of screen that measure depth in cm

44. Abdominal ultrasound Patient prep NPO both food and water
Ingesta causes more gas

45. Abdominal Ultrasound Patient Prep
Full urinary bladder is ideal for scanning bladder and prostate
Clip hair coat – costal arch, flank, caudally to the bladder
Apply coupling gel
Ventrodorsal or lateral recumbancy

46. Abdominal Ultrasound Liver and Biliary Tract
Survey radiographs are superior to ultrasound for assessing liver volume
Indications for liver scanning – hepatomegaly or a mass seen on survey, elevations in liver enzymes, ascites, suspected hepatic mets
Ultrasound guided biopsy often performed

47. Abdominal Ultrasound Spleen
Indications for scanning – mass, diffuse enlargement, abnormal position identified on survey radiographs, also abdominal trauma with hemorrhage, acute abdominal pain, signs of anemia and collapse

48. Abdominal Ultrasound Pancreas
Pancreatitis is the most common reason for scanning
Neoplasm, cysts and abscesses are rare

49. Abdominal Ultrasound Gastrointestinal Tract
Difficult due to gas and feces
Used to identify GI mural masses, foreign bodies, to confirm intussusception
String in intestine

50. Abdominal Ultrasound Kidneys and adrenal glands
Used to identify kidneys not seen on survey
Characterize a mass seen on survey
Assess enlarged kidneys
Determine location of mineralizations
Confirm fluid accumulations in the kidneys
Adrenals – determine enlargement

51. Abdominal Ultrasound Prostate Indicated in Prostatomegaly
Signs of urinary tract disease
Constipation
Caudal abdominal pain
U/S guided biopsy to determine BPH from neoplasia/infection
Full bladder helps to visualize

52. Abdominal Ultrasound
Urinary Bladder
Tumors
Calculi
Blood clots

53. Abdominal Ultrasound Reproductive tract Pregnant uterus
Optimal time for detection of pregnancy is days after last breeding
Equine days
Non-pregnant uterus
Pyometra
Stump granuloma
Ovarian neoplasia

54. Ultrasound of the Eye
After application of topical anesthetic directly on the cornea
Evaluates
Cornea
Anterior chamber
Ciliary body and lens
Vitreous chamber
Optic disc
Optic nerve
Extraocular muscle
Retrobulbar fat

55. Echocardiography Allows rapid assessment of functional compromise
Detection of chamber size abnormalities
Pleural and pericardial effusion
Cardiac masses
Congenital abnormalities
Valvular motion (M-mode)

56. Extremities Most useful in the equine limb Traumatic injury Infection
Inflammation