الفهرس 
Introduction
Rationale for CRT–IGRTOnly 14 pages are availabe for public view
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Abstract
Treatment of cancer by radiotherapy has a challenging item always present causing limitation in its dosage for treatment, this is that we can not give high dose permitting all cancer cells killing due to fear about damage of nearby normal tissues ,or by other means How can we decrease PTV as can as possible ?.
Image-guided radiotherapy (IGRT) is defined as frequent imaging in the treatment room that allows treatment decisions to be made on the basis of these images. It has enabled knowledge of the exact position of the tumor and control of organ motion to be established during treatment As a result, the PTV margins can be substantially decreased (centimeters to millimeters), leading to a substantial reduction in the volume of radiation.
IGRT can be applied for managing of inter-fraction as well as intra-fraction geometric set-up uncertainties and for adapting treatments to tumor responses.
IGRT serves several purposes:
First, reducing the treatment margins to an optimum level.
Second, providing an exact knowledge of anatomy during dose delivery in real time, which is required for ‘dose painting by numbers’ and hypo fractionated radiotherapy; and
Third, the interactive adaptation of the treatment on the basis of daily assessment of changes in tumor volume and response to the treatment.
It is used in lung cancer, prostate cancer, breast cancer and head and neck cancer giving good results.