Physics Bucharest 2017

6/3/2017

IMRT – Why? The biological argument, dose escalation

Probability of Tumor Control

1.0

Probability of Normal Tissue Damage

Therapeutic Effect (B)

“Increased conformity keeps high dose levels away from OAR”

Therapeutic Effect (A)

Respons

MAX. TOXICITY LEVEL

0

A B

Target Dose (Gy)

3

ESTRO physics course 2017

IMRT – Why? Looking at conformity

“Conformity index” is a measure of how well confined to the target volume: CI= V target / V treated Conventional RT gives a low CI whereas the CI of IMRT approached unity.

Conventional Radiotherapy

Intensity Modulated Radiotherapy

Knoos T, Kristensen I, Nilsson P: Volumetric and dosimetric evaluation of radiation treatment plans: radiation conformity index. Int J Radiat Oncol Biol Phys 1998, 42(5):1169-1176

4