This document discusses image processing in measurement guided radiotherapy and geometric accuracy. It provides an outline on the history of x-rays and medical imaging, types of radiotherapy including 2D, 3DCRT, IMRT, IGRT and SRS. It describes the key steps involved in radiotherapy including patient positioning, imaging, treatment planning, dosimetry and treatment delivery. It emphasizes the importance of quality assurance for imaging and treatment machines to ensure geometric accuracy and highlights periodic training as important for all staff involved.

1. Image Processing in Measurement
guided Radiotherapy and
Geometric accuracy
Anto Vaz S
Kovai Medical Center and Hospitals

2. Presentation Outline
X-ray a Brief History- (5 slides)
Medical Imaging a Brief History - (11 Slides)
Radiation Oncology Facts and Time stamp- (10 Slides)
2-D, 3-DCRT, IMRT , IGRT ,SRS.. - (12 Slides)
Steps involved Radiotherapy - (12 Slides)
Quality Assurance in Imaging and Radiotherapy - (10
Slides)

3. Radiotherapy- Time Stamp
1895 - X-ray - Wilhelm Roentgen -

4. Time Stamp Continued….
1896 - Radioactivity - Henri Bequerrel

5. Time Stamp Continued ….
1900 - α and β rays - Ernest Rutherford

6. Time Stamp Continued ….
1900 - Radium and Polonium - Marie Sklodowska Curie

7. X-rays in Medical Field
Crookes Tube to produce X-ray
John Hall Edward used clinical in Jan 1896
Surgically used in Feb 1896
Marie Curie had her mobile X-ray Setup in world war
Helped Surgeons at the Warfront to quickly assess bones,
joints, internal haemorrages

9. Medical Imaging
X-ray Machine - 2 D Image
Computed Tomography - 3 D Image
Fluroscopy - 2 D Image mutiple frames / sec

10. 2D Radiograph with X-rays
Why ?
Y- Axis
X- Axis

11. 2D Radiograph with X-rays
Why ?
Y- Axis
Z- Axis

12. 3 D Tomograph with X-rays = C.T.
Y- Axis X- Axis

13. Digital Medical Imaging - Fact Time
● Dicom- Digital Imaging and Communications in Medicine
● Standardised and Formulised in 1980 by NEMA &
ACR
● Common Language to be spoken about Medical Imaging
throughout the World
● First version in 1993 and the latest version in 2011 and
yet to continue
● What is it needed to be common about imaging ?

14. Digital Medical Imaging - contd...
1-bit 2-bit 4-bit
8-bit 24-bit 12-bit

15. So What ?
● Human Eye is Capable of differentiating 32 Shades of
Gray(25)
● Normal DisplayMonitor used in CT can distinguish 256
shades of Gray (28)
● Dicom Images contains information about 4096 shades
of Gray (212)
● This value (4096 shades) is beyond Human Eye’s
Perception
● Window Level narrows the range of shade to be viewed
at one time ?

16. Digital Medical Imaging - Contd...

17. He is the Reason - !
● Sir Godfrey Hounsfield - Father of Computed
Tomography
● Deviced a setup which will take standard X-ray all
around a patient (1971)
● Combine them to form a 3 D information inside the
patient
● Used a Roating X-ray Tube and a fast computer to
process the Image
● Given different shades based on Density of tissue (-
1000 to 0 to 1000 HU)

18. Graphically it means
-500 to 200
-200 to 100
25 to 40
25

19. HU value equates the Electron Density of the Tissue

20. When are we going - !

21. Radiotherapy
Started in 1896, Dr Emil Grubbe used X-ray to Treat Cancer
Early 1920s Radioactive elements radium and polonium were
used to produce cutaneous Burns
Low voltage X-rays were used to treat superficial Tumors
For Deep Seated Tumors X-rays of Million volts are needed
Radioactive isotopes like Co-60 Ir-192 Cs-137 are some of the
widely used sources
Photons, Electrons, Protons, Neutrons and Heavy Ion Particles

22. Machines in Radiotherapy

23. Machines in Radiotherapy

24. Machines in Radiotherapy

25. Machines in Radiotherapy

26. Machines in Radiotherapy

27. Machines in Radiotherapy

28. Radiation Biology
Study of effect of Ionizing Radiation in living organisms
Interaction happen with 10-13 of a second of the Exposure
Free Radicals will be produced in any organic medium
Changes will be produced at the DNA level ex single break,
Double bond break
Normal cells has repairing capacity, cancer cells dont
Effect of Radiation is cummulative

29. Radiation Physics
Gamma and X-ray
They will deposit energy as they
travel through any medium
Level of deposition of energy
depends type of particle,
Electron Density of the
Medium

30. Linear Accelerator based Radiotherapy

31. Video

32. 2-D Radiotherapy

33. Conformal Radiotherapy

34. 3DCRT

35. IMRT
Intensity Modulated Radiotherapy Where we modulate the
intensity of radiation using Multi Leaf Collimator
Multiple Beam (7-9 Beams)
Reduce the Radiation going to the Organ at Risk
(Spine,Brainstem,Parotid,Lung,Heart,Kidney,Rectum &
Bladder)

36. Contd….

37. IGRT
Image Guided Radiotherapy, will use either 2D(Xray) or 3D
imaging (Cone Beam CT)
Linear Accelerators will have capability of doing a Xray and CT
Recent Development is Linac with MRI- !
Ensure the Efficiency of Treatment with the help of Imaging
Change in Anatomy can be found during treatment and corrected

38. IGRT

39. Stereotactic Radio Surgery (SRS)
ste·reo·tac·tic - A technique in which
one can reach a point inside a
frame using rigid Coordinate
System (Cartesian or Polar),
Usually the frame will be attached
to Patient Head
Word coined in late 1940’s

40. SRS
Stereotactic Brain
Surgery
Stereotactic Radio Surgery Stereotactic Breast Biopsy

41. SRS
Originally designed with an intention to be used as surgical tool by Leksell
Later on used extensively for Neuro Oncology
It is based on Polar Coordinates (Angle,Depth Anterio Posterior Position)
Proton was the first choice by Physicist Kurt Liden and Radiobiologist Borje
Larsson
Due to complication in Sychrocyclotron, Leksell made simple and practically
effective Gamma- Knife with the same Centre of Arc Principle (Early
1950’s)
In 1953 Linear Particle accelerator developed parallelly at London with similar
approach(4 MeV Electrons)
Late 1980’s Linear Accelerator based SRS started to take main stage

42. Gamma Knife
First Generation ‘B’ Helmet needs Manual
Positioning of Patient - Prone to Human
Error
‘B’ Helmet fitted with APS Robotic system to
position the Patient

43. Linac based SRS ( X knife)
Cone, Frameless SRSMicro MLC ,Frame Based SRS Cone,Frame Based SRS

44. What Now- ?

45. Steps Involved in Radiotherapy
Positioning of Patient Imaging in CT
Treatment Planning
Image Fusion
Target Delineation
MR, PET, DSA &
4DCT
Plan EvaluationDosimetry
Verification
Image Guidance
Treatment Delivery
Patient

46. Patient Positioning

47. Imaging in CT

48. Supportive Images
Digitally Subtracted Angiograph
M R I
P E T
4D-CT

49. Image Fusion

50. Target Delineation

51. Treatment Planning

52. Plan Evaluation

53. Dosimetry - Verification

54. Image Guidance

55. Treatment Delivery

56. Pit Fall- !
● Radiation Oncologist, Medical Physicist ,
Dosimetrist, Radiotherapy Technologist,Nursing
Staff,RSO,Service Engineers
● Qualified Skill Tank is a Must
● Periodical Training & Skill enhancement
● Periodic Quality Assurance and Control

58. Image Quality and Assurance
● Apart from Periodic QA for CT,
Couch tilt and sag has to be
Quantified (Tolerance=0.5 deg)
● Nominal Image slice Indice has to be
verified, Images has to be taken with
a slice thickness of <=0.7mm (
Normal Voxel size in dicom Voxel =
0.7cm X 0.7cm X 0.7cm)
● Verification of CT number should be
done monthly as dose deposition is
directly correleating to this parameter
● Spatial Resolution(High and Low
Contrast), In Plane Resolution has to
match manufacturer spec

59. Image Quality ….
● Proper Selection of Reconstruction
Kernel will improve spatial
Resoltuion
● FOV impacts greatly on the
reconstruction Clarity . Smaller the
FOV better the clarity
● Timed Automatic Contrast Injector is
must to have a enhanced
visualisation of CT. Delay Time of
contrast should be verified
● Keep CT Gantry at 0’ and pitch
should be less than 1.3

60. Image Quality ….
● Perform MR QA with the suitable phantom periodically if
MRA is a mandatory for visualization
● Check Signal to Noise Ratio,Image Uniformity,Spatial Linearity
● Slice Profile and thickness plays vital role in SRS as the target
volume could be as small as 0.5 cc Recommended <1mm(T1
post Contrast)
● When MPR (Multi Planar Reconstruction ) is being used, do
verify the reconstruction process with a phantom for any
possible distortion along y axis(Superio Inferior Direction)
● For Frameless SRS, doing a Planning MR will remove most of
the uncertainties involved in image registration

61. Image Quality ….
● If DSA is being used to identify
AVM and CCF the following
parameters should be periodically
reviewed
● Orthogonality of the C-
arms,Couch Sag, Docking system
and Regular Fluro parameters also
to be verified
● Needle phantom can be used to
verify orthogonality of the arms as
a alternative method

63. Machines in Radiotherapy