Vision :IMC aspires to be a leader in applied medical sciences, health care education and research.

Dr. Mohammed EMAMPh.D., Paris-Sud 11 University

RAD 481

Radiotherapy Physics and Equipment

Lecture’s Title: Beam Directed Radiotherapy: Principles and practice

Radiological Sciences Department

DEFINITION

Beam directed

radiotherapy

Advance Planning

Beam Directing

devices

Exact

Calculations

2

NEED FOR BEAM DIRECTION

Homogenous Tumor Dose Low normal tissue dose

Best therapeutic ratio

3

STEPSPositioning

Immobilization

Localization

Field SelectionDose distribution

Calculations

Verification

Execution

4

POSITIONING

Patient positioning is the most vital and often the most NEGLECTED part of beam direction:

Good patient position is ALWAYS: Stable.

Comfortable.

Minimizes movements.

Reproducible.

5

EXAMPLES

6

STANDARD POSITIONS

most comfortable.

Best and quickest for setup.

Minimizes errors due to miscommunication.

Best for treating posterior structures like spine

In some obese patients setup improved as the back is flat and less mobile.

Supine

Prone

7

POSITIONING AIDSHelp to maintain patients in non standard positions.

These positions necessary to maximize therapeutic ratio.

Accessories allow manipulation of the non rigid human body to allow a comfortable, reproducible and stable position.

8

POSITIONING AIDS…

Pituitary

Board

Prone

Support3 way

support

9

BREAST BOARDS…

Modern Breast

Board

Indexed Arm

supports

Indexed wrist

support

Head rest

Carbon fiber

tilt board

Wedge to prevent

sliding

10

ARM SUPPORT

Also known as the T bar.

Allows the arm to be positioned laterally when treating the thorax using lateral beams.

BELLY BOARDS & LEG IMMOBILIZER

12

MOULD MAKING

13

MOULD MAKING : CONTD..

14

MOULD MAKING : CONTD..

15

THERMOPLASTICS

Thermoplastics are long polymers with few cross links.

They also possess a “plastic memory” - tendency to revert to normal flat shape when reheated

THERMOPLASTICS : PRINCIPLE

FOAM SYSTEMS

Made of polyurethane

Advantages: Ability to cut treatment portals into foam.

Mark treatment fields on the foam.

Rigid and holds shape.

Disadvantages: Chance of spillage

Environmental hazard during disposal

VACUUM BAGS

Consist of polystyrene beads that are locked in position with vacuum.

Can be reused.

BITE BLOCKS

A simple yet elegant design to immobilize the head.

A dental impression mouthpiece used.

The impression is attached to the base plate and is indexed.

Head position recorded with 3numbers.

20

SRS DEVICESStereotactic frames.

Gill Thomas Cosman System.

TALON® Systems – NOMOS corp.

21

LOCALIZATION

The target volume and critical normal tissues are delineated with respect to patient’s external surface contour.

What to localize? Tumor

Organ

Methods? Clinical examination

Imaging

22

Thank you

Floor is open for Questions and Discussion