الفهرس 
Introduction and Literature reviewOnly 14 pages are availabe for public view
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Abstract
The purpose of this thesis was to look into the major differences and advantages of Intensity Modulated Radiation Therapy (IMRT) versus 3D Conformal Radiotherapy (3DCRT) for head and neck (H and N) cancer patients. In this study, treatment plans for 50 H and N patients were planned for both IMRT and conformal techniques (MONACO program for IMRT and Xio with conformal technique) and statistically compared. According to the taken doses and the specified area planning target volume (PTV), radiation oncologists classified target volumes as PTV66 and PTV54. Maximum dose values and D95% delivered to the target volumes were determined as a percentage for each specific definition and the dose values of organs at risk (OAR) were also evaluated.
Additionally, the factor of Homogeneity index (Homogeneity index, HI) was used to determine the extent to which the high dose region was compatible with PTV. The radiotherapy Conformity index is a practical method for determining the efficiency of radiotherapy treatment plans experimentally and demonstrating the relationship between tumor mass and isodose distribution. Dosimetric parameters derived from the two techniques as obtained from the Treatment Planning System (TPS) were tabulated for comparisons using Student’s t-test when data showed normal distribution. Also, Wilcoxon test was used with the nonparametric distribution in addition to reporting the median, maximum, minimum values and interquartile range.
In terms of tumor coverage, the IMRT plans showed superior performance in comparison to 3DCRT for coverage of the PTV66Gy and PTV54Gy. When compared to the reference 3DCRT, the IMRT dose plans provided better target coverage with high statistical significance. With a dosage of more than 95 percent of the recommended dose, there was also a significant increase in tumor volume coverage. Also, the conformity index was better with the IMRT technique, as in most cases the IMRT was able to reach the optimal value whereas in 3DCRT the conformity index was higher than the optimal value implying that the irradiated volume is larger than the tumor volume. Even for the homogeneity index (considers the homogeneity of the dose distribution within the tumor), the result of the 50 head and neck patients with the IMRT technique showed better homogeneity than 3DCRT, where in most cases the IMRT was able to approach the optimal value whereas 3DCRT provided less homogeneity measurements than the optimal values that could cause cold areas within the tumor volume.
As for the sensitive organs since they are so close to the tumor, most normal organs receive doses that are higher than the tolerance values in 3DCRT plans. where the statistical analyses showed a significant deferent between the two techniques in protecting each of the spinal cord, parotid gland, Rt and Lt lens, pituitary gland and the brain stem. As for the Rt and Lt eye, Rt and Lt optic nerve and optic chiasm the statistical analyses showed that there was no significant deferent between the two techniques.
IMRT has proven its ability to produce reasonable balance in protecting the organs at risk and delivering a high dose to the tumor volume. Therefore, IMRT technique was able to improve the quality of the treatment plan to a significant extent. The study highly recommends the use of IMRT in the radiotherapy treatment planning in head and neck cancer patients.