Radiotherapy

Question 1

What is the planning procedure before radiotherapy

Answer 1

CT conformal planning:
1. GTV (Gross Tumour Volume) = the gross palpable, visible or demonstratable extent of the tumour
2. CTV (Clinical tumour volume) = GTV and/or microscopic spread of disease
3. PTV (Planning Target Volume) = a geometric concept used for treatment planning

Question 2

What are the different CT volumes in treatment

Answer 2

TV (treated volume) = volume of tissue in the high dose region (typically enclosed by the 95% isodose)
IV (irradiated volume) = volume of tissue that is receiving any radiation at all including entrance and exit beams

Question 3

Side effects of radiotherapy

Answer 3

Skin problems
Fatigue
Head and neck: Dry mouth, mouth and gum sores, difficulty swallowing, stiffness in the jaw, nausea
Chest: difficulty swallowing, breast or nipple soreness, cough, fever, fullness of chest
Stomach and abdomen: nausea and vomiting, diarrhoea
Pelvis: diarrhoea, rectal bleeding, incontinence, bladder irritation
Men: erectile dysfunction
Women: Changes in menstruation

Question 4

How is the dose for radiotherapy expressed

Answer 4

Gray (Gy) = energy absorbed per unit mass
1 gray = 1 joule/kg