Imaging Methods in Monitoring and Diagnosis

1. Imaging Methods in Monitoring and Diagnosis Dr Lizzie Peachey

2. Imaging Modalities • X Rays • Ultrasound • Magnetic Resonance Imaging • Nuclear Medicine

3. X-Rays

4. X-Rays • Discovered by Roentgen in 1895 • Ionising radiation • Higher frequency / short wavelength

5. X-Rays • X-rays produced by the x-ray tube pass through the body leaving a ‘shadow’ on the film

6. X-Ray Production

11. Contrast

12. Plain Digital Radiography

13. Computerised Tomography (CT)

14. CT X-Ray Beam

15. Helical CT

16. Computerised Tomography

17. Computerised Tomography

18. X-Rays • Non-invasive • Well established technology • Still evolving • Flexible • Readily available and therefore relatively cheap • Ionising radiation • Not good at imaging soft tissue on its own Pros Cons

19. Medical Ultrasound (MU) • Utilises sound waves at ultrasonic frequency • Above 20KHz is ultrasound but usually 3–10 MHz for medical imaging purposes • Transducer sends and receives ultrasonic waves • Echoes from tissue can be detected and data interpreted digitally to produce image • Position and depth of the echoes builds up a complete picture • Gel is used to improve imaging

20. MU Imaging

21. MU Imaging

22. Image Manipulation

23. MU Imaging

24. Doppler Imaging

25. Medical Ultrasound • Non-invasive • No ionising radiation • Dynamic technique • Portable • Can image soft tissue effectively • Flexible equipment • Relatively cheap • Limited in what can be imaged • VERY user dependent Pros Cons

26. Magnetic Resonance Imaging • Greatest detail of all the imaging modalities • Uses a powerful magnetic field to align the magnetization of atoms in the body • Data detected can be digitally converted into an image • Utilises tomographic techniques of CT but no radiation

27. MR Imaging Principle • Human body = 70% water – H2O • MRI uses the spin of hydrogen atoms • Single positively charged proton • Spin causes tiny magnetic field • All in different directions – PRECESSION • Spin frequency depends on the type of atom or molecule – LARMOR FREQUENCY • Hydrogen atoms in different tissues have different Larmor Frequencies

28. Alignment of Atoms

29. MR Imaging

30. MR Imaging

31. Image Manipulation

32. MR Imaging • Non-invasive • Does not use ionising radiation • Excellent for imaging soft tissues • Can image function • Good spatial resolution • Good at cancer diagnosis • Very expensive • Has health and safety issues • Has ‘acceptability’ issues with some patients Pros Cons

33. Nuclear Medicine • Use of radioisotopes • Attached to pharmaceuticals • Drugs absorbed preferentially by target organ(s) • Gamma emitter so can be detected • Images produced digitally from data gathered

34. Nuclear Medicine Images

35. Nuclear Medicine Images

36. PET-CT

37. Nuclear Medicine • Can image wide variety of tissue types • Easy to target specific tissue • Can image function • Utilises by-products of other processes so cost effective • Uses ionising radiation • Could be described as invasive • Has many radiation protection issues associated with it • Better applications are expensive Pros Cons

38. Which should be used? • What information is required? • Does structure or function need to be seen? • What can the patient tolerate? • What would the clinician prefer? • What is available for use? • Is there a safer/cheaper alternative? • Can potential risks be justified?