Physics Safety & Infection Control Setting Up The Machine

1. PhysicsSafety & Infection ControlSetting Up The Machine H. Gee MD, FRCOG (teaching materials provided by David Cole, Lecturer at City University, Birmingham)

2. Sound WAVELENGTH  + LOW PRESSURE REGION HIGH PRESSURE REGION = ONE CYCLE

3. A sound wave wavelength Excess pressure amplitude

4. Amplitude & Frequency • Frequency • Pitch • Amplitude • Loudness • the strength of the sound. • The maximum change in pressure due to the soundwave

5. Ultrasound

6. Ultrasound • High Frequency Sound • > 20 KHz (above the audible range) • Short Wavelength • Resolution  Wavelength • 3.5 MHz - Wavelength = .44 mm • Frequency  Penetration 

7. Spatial Resolution • The ability to display two small structures situated close together as separate images objects Image resolved Image unresolved

8. Piezo-electric effect • Sound  Electricity Piezo-electric crystal

9. Inverse piezo-electric effect • Electricity  Sound Piezo-electric crystal

10. Ultrasound transducer PULSE CONVERTS ELECTRICITY INTO SOUND PIEZO ELECTRIC CRYSTAL ECHO CONVERTS SOUND INTO ELECTRICITY

11. Pulse echo techniquemultiple reflectors

12. Imaging Principles

13. Imaging Principles

14. How the image is produced

15. Summary • Sound • Ultrasound • Piezo-electric effect • Pulse-echo technique • Imaging principles • Resolution

16. Infection Control

17. Setting up the Machine • Two Parts • Monitor (may be done automatically) • Contrast • Brightness • Grey Scale on Screen – ALL GRADATIONS • Imaging System

19. Equipment Controls • Probe selection • Mode selection 2D, Doppler, Colour • Gain, TGC, Power • Depth and Zoom Scan angle (field size) • Focus • Measurement, freeze • (Examination selection post processing)

20. Probe selection • This control is used to select from the probes available • For example • Curvilinear general • Transvaginal • Linear array for small parts

21. Mode selection 2D, Doppler, Colour • 2D is normally selected automatically for all examinations and the other modalities are selected when required during the examination.

22. Making the image darker or brighter • Power • Gain, • Time Gain Compensation

23. Cavitation Heating Frequency Duration Intensity Power Safety

24. Power (Output) increased Safety implications Set power to 35% Use gain to control brightness BRIGHTER IMAGE

25. Power reduced DARKER IMAGE

26. Gain • Controls image brightness by amplifying echo signals • Completely safe • Increased image noise

27. Gain INCREASE IN GAIN MORE NOISE

28. Time gain compensation (TGC)

29. Time gain compensation (TGC)

30. Time gain compensation (TGC) TGC correct

31. Changing the field size • The following controls change the size of the field of view • Depth • Zoom • (Scan angle)

32. Freeze • Measurement • Image recording

33. Measurement • Electronic callipers • Linear • Circumference / area • Ellipse / trace • Volume measurement • Organ specific • Embedded charts = + +

34. Summary • Probe selection • Mode selection 2D, Doppler, Colour • Depth and Zoom Scan angle (field size) • Gain, TGC, Power • Focus • Measurement, freeze (& cine loop) • (Examination selection post processing)

35. Important Controls • Power (output, acoustic) • Gain • Time gain compensation (TGC) • Freeze • Electronic calipers