General introduction- fundamental principles X ray & CT

1. General introduction- fundamental principles X ray & CT Radiology Dept. 1st Hospi. of Peking University 唐光健

2. Questions to think of with the lecture • What is X ray? What kinds of the features of it are useful or harmful? • What are the two steps of X ray imaging? • How is the grey scale of bone, muscle and air in the X ray film? • What is the main difference between the CT imaging and the image of X ray film? • What are same and what are different between the processes of CT imaging and imaging of X ray projection? • Is the meaning of a CT axial imaging and a section of a body specimen in same location identical?

4. Black box?

5. Black box? Wilhelm C Röntgen

6. Wilhelm C Röntgen

7. Generation and features of X ray • High speeding electrons Anode target sudden slow down special X ray – sequence spectrum narrow consecutive X ray – sequence spectrum wide e special X ray – sequence spectrum narrow consecutive X ray – sequence spectrum wide e X ray

8. Generation and features of X ray • electromagnetic waves -ionizing radiation -wave length of medical use: 0.08 ~ 0.71Å -feature of wave; feature of particle • Features-Effects • Physical effect • Chemical effect • Biotic effect

9. Generation and features of X ray • electromagnetic waves -ionizing radiation -wave length of medical use: 0.08 ~ 0.71Å -feature of wave; feature of particle • Features-Effects • Penetrability • Fluorescent effect • Thermal effect • Ionizing effect • interference，diffraction, reflection, refraction • Physical effect • Chemical effect • Biotic effect

10. Generation and features of X ray • Penetrability • Fluorescent effect • Thermal effect • Ionizing effect • interference，diffraction, reflection, refraction • Features-Effects • Physical effect • Chemical effect • Biotic effect -be able to penetrate ma. of dif. density while attenuated I = I0 · e-µl I0 µ I l

11. Generation and features of X ray • Penetrability • Fluorescent effect • Thermal effect • Ionizing effect • interference，diffraction, reflection, refraction • Features-Effects • Physical effect • Chemical effect • Biotic effect -making some compounds fluoresce -Fluoroscopy, image intensifier

12. Generation and features of X ray • Penetrability • Fluorescent effect • Thermal effect • Ionizing effect • interference，diffraction, reflection, refraction • Features-Effects • Physical effect • Chemical effect • Biotic effect -making some compounds fluoresce -Fluoroscopy, image intensifier

13. Generation and features of X ray • Penetrability • Fluorescent effect • Thermal effect • Ionizing effect • interference，diffraction, reflection, refraction • Features-Effects • Physical effect • Chemical effect • Biotic effect -Subject absorb the energy of X ray  ionized  ionized voltage -ionizing cell auto-exposure X ray detector

14. Generation and features of X ray • Penetrability • Fluorescent effect • Thermal effect • Ionizing effect • interference，diffraction, reflection, refraction • Features-Effects • Physical effect • Chemical effect • Biotic effect - penumbra, interferential signal image blued

15. Generation and features of X ray • sensitization effect • coloration effect fundament of X ray filming • Features-Effects • Physical effect • Chemical effect • Biotic effect

16. Generation and features of X ray • Features-Effects • Physical effect • Chemical effect • Biotic effect • radiated tissue cells restrained, damaged, necrosing X ray protection

17. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium

18. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium I0 µ1 µ2 µ3 µ4 I l1 l2 l3 l4 I = I0 · e-µ1l1· e-µ2l2· e-µ3l3· e-µ4l4

19. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium • getting special distribution of different density overlapping of anterio-posterior images

20. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium • film-silver bromide decomposed positive correlation with dosage of X ray negative correlation with degree of attenuation • flu. screen • detectors

21. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium • grey of spots ∽ thickness & density of the mat. in the path way of X ray beam • distribution of the spots ∽ anatomic form in the path way of X ray beam • difference between the sports - contrastimage natural contrast artificial contrast

22. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium • grey of spots ∽ thickness & density of the mat. in the path way of X ray beam • distribution of the spots ∽ anatomic form in the path way of X ray beam • difference between the sports - contrastimage natural contrast artificial contrast

23. X ray Imaging • X ray penetrate the subject（body) while attenuated • attenuate signal recorded by the accepting medium • grey of spots ∽ thickness & density of the mat. in the path way of X ray beam • distribution of the spots ∽ anatomic form in the path way of X ray beam • difference between the sports - contrastimage natural contrast artificial contrast

24. X ray Imaging

25. X ray equipment • X ray source • X ray tube High voltage generator • X ray imaging devices • X ray film / image intensifier / plate detector • X ray mechanical device • exam table frame……

26. X ray equipment • X ray tube • filament - cathode • anode target • tube shell

27. X ray equipment • X ray tube • filament - cathode • anode target • tube shell

28. Protection from X ray • X ray protection • Cancel X ray exam unnecessary • Reduce radiation dosage • Distance from X ray source • Protective device

29. Principles of imaging diagnosis • familiar with imaging methods and body position • familiar with the normal imaging anatomy and variations • sequential observation • imaging manifestations and relationship with neighboring structures of the lesion • clinical and laboratory materials • understanding the meaning and limitations of the imaging methods

30. fundamental principlesof CT

31. fundamental principles of CT • CT-Computerized Tomography • real tomography，without any overlapping

32. fundamental principles of CT I0 I0 µ1 µ1 µ2 µ3 µ3 µ4 I I µ2 µ4 l1 l1 l2 l2 l3 l3 l4 l4 l1 = l1 = l1 = l1 = 1 I = I0 · e-µ1l1· e-µ2l2· e-µ3l3· e-µ4l4 I = I0 · e-µ1l1· e-µ2l2· e-µ3l3· e-µ4l4 I = I0 · e- (µ1+ µ2 + µ3 + µ 4) ·1

33. fundamental princ. of CT First laboratory CT scanner 1968 Godfrey Hounsfield

34. fundamental princ. of CT First clinical head CT scannerAtkinson Morley‘hosp.，London

35. fundamental principles of CT

36. fundamental principles of CT • measurement

37. fundamental principles of CT DAS－data acquisition system -detector -bumper -integrator -amplifier -A/D converter • measurement detector

38. fundamental principles of CT • Reconstruction

39. fundamental principles of CT • Reconstruction • backprojective method • Iterative method • Factorial method • Fourier method • Filt. backprojective method

40. fundamental principles of CT • Reconstruction • Filt. function(Kernol) • High filt.(bone algorithm)low filt.(soft tissue algorithm)

41. fundamental principles of CT • Reconstruction • Filt. function(Kernol) • High filt.(bone algorithm)low filt.(soft tissue algorithm)

42. fundamental principles of CT CT value - relative magnitude to water may be used qualitatively but not quantitively • Reconstruction [(μobj.- μwater)/μwater]×1000

43. fundamental principles of CT • image display

44. fundamental principles of CT • image display 200/30=7HU muscle 50HU- fat -50HU=100 ~13 grey scale 1000/30=33HU muscle 50HU- fat -50HU=100 ~3 gray scale • ability of identify grey scale • eyes：24~30 • CT：2000

45. fundamental principles of CT • image display • Voxel and pixel • voxel – 3D, pixel – 2D • CT value of a voxel represent all messages of the elements in the voxel

46. fundamental principles of CT • image display partial volume effect

47. fundamental principles of CT • enhancement CThigh density contrast agent injected into veinintro-vascular/-tissue（extracellular space)  CT scan  density contrast • hypersensitiveness nephrotoxitity

48. fundamental principles of CT • enhancement CThigh density contrast agent injected into veinintro-vascular/-tissue（extracellular space)  CT scan  density contrast • hypersensitiveness nephrotoxitity

49. fundamental principles of CT • enhancement CThigh density contrast agent injected into veinintro-vascular/-tissue（extracellular space)  CT scan  density contrast • hypersensitiveness nephrotoxitity

50. fundamental principles of CT • Indications • No absolute contraindication, suitable for emergency and serious cases exam • Single imaging factor，image interpretation easily，anatomy clear and detailed • deformation、infection、trauma、neoplasm… • Limitations • Low soft tissue resolution ，difficult to detect lesion with small density difference from neighbor structure • Low sensitivity for the lesion with slight gross change • Contrast agent using