Radiological Sciences Department Ph.D., Paris-Sud 11 University Radiotherapy Physics and Equipment RAD 481 Lecture’s Title: Beam Directed Radiotherapy: Principles and practice Dr. Mohammed EMAM Ph.D., Paris-Sud 11 University Vision :IMC aspires to be a leader in applied medical sciences, health care education and research.

Beam directed radiotherapy Beam Directing devices Definition Beam directed radiotherapy Advance Planning Beam Directing devices Exact Calculations

Need for Beam direction Homogenous Tumor Dose Low normal tissue dose Best therapeutic ratio

Steps Positioning Verification Immobilization Execution Calculations Localization Calculations Field Selection Dose distribution

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.

Examples

Standard Positions Best for treating posterior structures like spine In some obese patients setup improved as the back is flat and less mobile. Supine most comfortable. Best and quickest for setup. Minimizes errors due to miscommunication. Prone

Positioning aids Help 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.

Positioning aids… Prone Support Pituitary Board 3 way support

Breast boards… Indexed wrist support Indexed Arm supports Head rest Carbon fiber tilt board Modern Breast Board Wedge to prevent sliding

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

Mould making

Mould making : Contd..

Mould making : Contd..

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: Disadvantages: 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 3 numbers. 20

SRS devices Stereotactic frames. Gill Thomas Cosman System. TALON® Systems – NOMOS corp.

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

Floor is open for Questions and Discussion Thank you