Basic of Ultrasound Physics E FAST & Renal Examination. Dr Muhammad Umer Ihsan MBBS,MD, DCH CCPU,DDU1,FACEM

Transcription

1 Basic of Ultrasound Physics E FAST & Renal Examination Dr Muhammad Umer Ihsan MBBS,MD, DCH CCPU,DDU1,FACEM

2 What is Sound? Sound is Mechanical pressure waves

3 What is Ultrasound? Ultrasounds are sound waves with a frequency exceeding the upper limit of human hearing, which is 20 to 20 khz. Medical Ultrasound 2MHz to 12MHz

4 Speed of Sound Density of medium Propagation Speed Air = 330 m/s Bone = 4080 m/s

5 Speed of Sound Speed of sound though soft tissues ranges from 1450 m/s (adipose) to 1580m/s (muscle) Most ultrasound systems assume a default speed of sound of 1540 m/s for "tissue" m/s

6 Ultrasound Physics Wavelength Frequency

7 Acoustic Impedance MegaRayls (Z) Air: Z Bone 7.8 Z Adipose = 1.34 Z

8 Attenuation Reflection Refraction Scattering Absorption

9 Mode of Ultrasound A Mode B Mode (Gray sacle) M Mode (Motion)

10 Doppler Effect Moving object will change the frequency of reflected echoes

11 Colour Doppler BA RT

12 Power Doppler Displays the strength of the Doppler signal in colour, rather than the speed and direction information. 3 times more sensative

13 Spectral Doppler Two Types PW stands for pulsed wave Doppler. CW for continuous wave Doppler. Gate

14 ULTRASOUND How is it produced?

15 Ultrasound Wave Production. Transducer contains piezoelectric crystals which produce the ultrasound pulses (transmit 1% of the time & listen 99%). These elements convert electrical energy into a mechanical ultrasound wave called as Pulses. Returning sound waves from the tissues are converted into electric energy called as Echoes

16 How It Works? The sound waves travel into the body at different speed in different tissues until they hit a boundary between tissues (e.g. between fluid and soft tissue or soft tissue and bone). Some of the sound waves reflect back (Reflected Echoes) to the probe, while some travel on further until they reach another boundary and then reflected back to the probe. The differential between reflected echoes are detected,analyzed and then relayed to the machine.

17 Resolution Quality of the ultrasound image Depends on frequency and type of probe

18 Lateral Resolution

19 Axial Resolution

20 Relationship between Frequency & Resolution The frequency affects the QUALITY of the ultrasound image. The HIGHER the frequency, the BETTER the resolution. The LOWER the frequency, the LESS the resolution.

21 Relationship between Frequency & Penetration The frequency also determines the penetration of the ultrasound wave. A 12 MHz transducer has very good resolution, but cannot penetrate very deep into the body. A 3 MHz transducer can penetrate deep into the body, but the resolution is not as good as the 12MHz.

22 Appearance of Reflected sound waves (Echoes) on the machine. Strong Reflections = White dots Diaphragm, tendons, bone Hyperechoic

23 Reflected Echoes No Reflections = Black dots Fluid within a cyst, urine, blood Hypoechoic or echo free

24 Reflected Echoes Weaker Reflections = Grey dots Most solid organs, thick fluid isoechoic

25 Reflected Echoes

26 Echogenicity

27 Echotexture Smooth Coarse

28 Artifacts Sounds travels in a straight line Sound speed is uniform Single pulse from probe and return Attenuation is uniform Signals only from main beam

29 Shadowing

30 Post Cystic Enhancement

31 Lateral Cystic shadowing

32 Mirror Artifact

33 Reverberation Artifact

34 Transducer Types Many different types of Transducer available

35 Curvilinear

36 Linear

37 Phased Array

38 Endocavity

39 Probe Orientation

40 Body Imaging Planes

41 Organ Orientation Axial ( Long Axis ) Transverse (Short axis)

42 Organ Orientation

43 Organ Orientation

44 FAST& E FAST FAST = Focused Assessment with Sonography in Trauma. Extended FAST include sonography of the anterior thorax to rule out haemo-pneumothorax.

45 FAST is now an extension of physical examination of the trauma patient-(part of Circulation). used to identify intraperitoneal or pericardial fluid. efast identify haemo and pneumothoraces.

46 FAST ACEM Guidelines Following areas of the abdomen are scanned in FAST assessment. Perihepatic (Morrison's Pouch) Perisplenic (Lenorenal Space) Pelvis Pericardium (Subxiphoid view)

47 Equipment

48 Probe (2-5Mhz) Curvilinear low frequency

49 Perihepatic view

50

51 Perisplenic view

52 Perisplenic view

53

54 Subxiphoid view

55

56 Pelvic view

57 Longitudinal View

58 Longitudinal View

59 Transverse View

60 Ant Thorax

61

62

63 Strengths Rapid, bedside test Non invasive Reduced time to diagnosis Can be repeated Sensitivities 69-95% Specificities %

64 Limitations Can not identify cause of fluid Operator dependent Difficult in obese pt or increase bowel gas Cannot evaluate retroperitonium

65 Renal Scanning

66 Approach to Scanning LIVER STOMACH Right kidney scanning approach: anterior, lateral, posterior Liver is the acoustic window K IVC I AORTA S K Left kidney: requires a posterior approach, through the spleen Air-filled bowel impedes anterior scanning

67 Anatomy 9-12 cm long, 4-5 cm wide, 3-4 cm thick Gerota s fascia encloses kidney, capsule, perinephric fat Sinus Hilum: vessels, nerves, lymphatics, ureter Pelvis: major and minor calyces Parenchyma surrounds the sinus Cortex: site of urine formation, contains nephrons Medulla: contains pyramids that pass urine to minor calyces. Columns of Bertin separate pyramids

68 Ultrasound Anatomy

69 Right Kidney Long Axis Anterior Superior Liver Inferio Sinus Cortex Diaphragm Posterior

70 Right Kidney Short Axis Anterior Right GB Liver Left IVC R Kidney Vertebral Body Aorta Renal a. Posterior

71 Left Kidney Long Axis Anterior Super ior Inferior Rib Shadow Kidn Posterior ey Spleen

72 Left Kidney Short Axis Anterior Right Liver Left Spleen L Kidney Posterior

73 Range of Hydronephrosis Normal Mild Moderate Severe

74 Mild Hydronephrosis GB Kidney Liver

75 Moderate - Severe Hydronephrosis GB Kidney Liver Dilated pelvis

76 Renal Cysts Liver Scatter 2 0 Cyst Bowel Kidney

77 Questions?