1. بسم الله الرحمن الرحيم
﴿و قل رب زدنى علماً﴾
صدق الله العظيم

2. Introduction to Radiotherapy
Dr. Ahmed Al Far, M.D.
Professor of Radiation Oncology

3. Planning (1)

4. Patient Positioning
&
Immobilization

5. Patient Positioning: General Rules
EBRT Planning
Patient Positioning: General Rules
1. Comfortable position
2. Easily and accurately reproducible (day to day)
3. All fields should be treated in the same position
4. No obstruction in the beam pathway
5. The simulator couch: similar to that of treatment
6. Laser beam systems: increasing accuracy

6. Immobilization Methods
EBRT Planning
Immobilization Methods
◘ Simple methods:
Head & neck rest
Bite block
◘ Plaster of Paris cast:
Limited volume: joint, limb, head &neck
Whole body: wide field (e.g. medulloblastoma)
◘ Mask for head and neck:
Plastic
Thermoplastic
◘ Mattresses and cushions:
Plastic sac (small polystyrene beads, vacuum pump)
Different shapes and sizes

7. Supine Head Support

8. Construction of Head & Neck plastic mask-1
Positioning of patient ► ▲
Lifting off the negative ▲
Taking of impressions

9. Construction of Head & Neck plastic mask-2
► Negative
Mould ►
Filling with plaster ►
► Positive
Mould►

10. Construction of Head & Neck plastic mask-3
The positive on vacuum former

11. Construction of Head & Neck plastic mask-4
The positive with molded mask ►
The mask ▼ ▲
The completed mask with treatment markings

12. Construction of Head & Neck plastic mask-5
Patient lying on linear accelerator machine couch with treatment plastic mask

13. Immobilization methods-1►
Thermoplastic
head & neck mask ►
Thermoplastic
face mask

14. Immobilization methods-2
Total body plaster cast ►
◄ Alpha Cradle used for body

15. Contouring

16. Contouring ◘ Definition:
The outer circumference of the patient
In the transverse plane in central axis of the field
Indicate anatomical relationships:
- Target volume and normal tissues
- Fixed landmark or position of tattoos
- Isodose curve (s)
◘ Importance: reference during daily treatment
◘ Methods:
Lead solder
Plaster of Paris strip
Laser beam

17. ►
A cross section of the body and positioning of beams on the tumor ◄
A cross section of the body and the levels of radiation caused by the beam placement in the above image

18. Fields Arrangement

19. Fields Arrangement Central axes: same plane & meet at the isocentre
Planning
Fields Arrangement
► Single field:
► Two fields:
Parallel opposing
Non-parallel
Tangential
► Three fields:
Anterior + two lateral opposing
Anterior + two posterior oblique
► Four fields:
► Rotation & arc:
Central axes: same plane & meet at the isocentre

20. The Choice of Field Arrangement
Planning
The Choice of Field Arrangement
Factor affecting:
1. Position of the target volume
2. Size of the target volume
3. Position of the structures to be avoided.
4. Beam energy available / required
5. Beam modality available / required
6. Technical feasibility of equipment
7. Patient positioning.

21. Fields Arrangements -1 Two parallel opposing fields ►
e.g. palliative treatment ▲
Single field
e.g. Skin cancer
◄ Two tangential fields,
e.g. breast or chest wall irradiation

22. Fields Arrangements -2 ▲ ▲ Four fields Three fields
e.g. Prostate cancer ▲
Three fields
e.g. Bladder cancer

23. Thank You