1. CT “Computer tomography”

2. Contrast mechanisms in X-ray imaging: X-ray absorption X-ray absorption mechanisms: 1. Photoelectric effect 2. Compton scatter 3. Pair formation Problem: X-ray image is a summation image

3. CT History 1972 Godfrey Hounsfield „Siretom” head scanner (1974) 128x128 image recorded using the Siretom scanner (1975) Allan Cormack 1979 Nobel Prize in Medicine

4. CT Foundations I source detector

5. CT Foundations II µ x : linear attenuation coefficient

6. Scanning I I. generation Single moving source Single moving detector II. generation Single moving source Narrow fan-beam Multiple moving detectors

7. Scanning II III-IV. generation Single moving source Wide fan-beam Multiple detectors or detector ring closed gantry open gantry

8. CT Image Reconstruction 1. Algebraic reconstruction techniques 2. Direct Fourier reconstruction 3. „Filtered Back Projection” CT-image: 4000 detectors 1000 projections 512x512 matrix 16 bit depth

9. CT Image: Density matrix Density (“CT Number”): Hounsfield units µ: attenuation coefficient of voxel µ w : attenuation coefficient of water

10. Contrast Manipulation of CT Image: „windowing”

11. Spiral CT New CT Developments, Trends Virtual endoscopy Angiography 3D reconstruction

12. MRI “Magnetic Resonance Imaging”

13. Nuclei with nuclear spin: elementary magnets Magnetic moment:  =magnetogyric ratio L=angular momentum

14. In absence of magnetic field: Random orientation of elementary magnets In magnetic field: elementary magnetsenergy levels orientsplit B0B0 parallel antiparallel EE B0B0 E B

15. Precession Precession or Larmor frequency:

16. B0B0 M Low energy state parallel in case of proton High energy state antiparallel in case of proton Net magnetization (M) due to spin excess in different energy states

17. Excitation using radio frequency (RF) radiation Resonance condition: Larmor frequency M Net magnetization

18. Spin-lattice relaxation T1 or longitudinal relaxation t MzMz T1 relaxation time: depends on interaction between elementary magnet (proton) and its environment

19. Spin-spin relaxation T2 or transverse relaxation M xy t “free induction decay” (FID) T2 relaxation time: depends on interaction between elementary magnets (protons)

20. 1970: detection of lengthened relaxation times in cancerous tissues 1972: theoretical development of human in vivo 3D NMR 1977: first human MRI image Inventor of MRI: Raymond V. Damadian (1936-)

21. MRI: Net magnetization of the human body takes place “indomitable”

22. Paul C. Lauterbur (1929-) 1971: development of spatially resolved NMR

23. voxel: volume element pixel: picture element Image MRI imaging I: Spatial resolution

24. Definition and addressing of elementary 3D image points (voxels): by using gradient magnetic fields MRI imaging I: Spatial resolution ByBy BxBx BzBz

25. MRI imaging II: Color (grayscale) resolution (contrast) Based on relaxation times

26. MRI imaging II: Color (grayscale) resolution (contrast) Based on spin density and relaxation times T1-weighing T2-weighing Proton density- weighing

27. MRI technology Magnet: superconducting (liquid He) Resolution enhancement: with surface RF coils Excitation with pulse sequences 90˚ Detection and analysis: Fourier transform of temporal signal t

28. MRI: Image manipulation I Reslicing in perpendicular plane

29. MRI: Image manipulation II Spatial projection („volume rendering”)

30. Blood flow Image slice Saturated spins Unsaturated spins MRI: Non-invasive angiography

31. MRI: Non-invasive angiography arteria carotis Circulus arteriosus Willisii

32. MRI movie Based on high time resolution images Opening and closing of aorta valve

33. Functional MRI fMRI High time resolution image sequences recorded synchronously with physiological processes Effect of light pulses on visual cortex

34. MRI információ szuperponálása egyéb információval (PET)

35. Superposed MRI and PET image sequence PET activity: during eye movement Volume rendering