Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Biophysics

Purposes of the study: to compare the dosimetry for breast cancer treatment plans using different radiotherapy treatment planning techniques. Materials and methods: twenty breast cancer patients were treated using three different radiotherapy techniques, including: 1) conventional tangential wedge-based fields (TW) carried out by 3D conformal radiotherapy (3DCRT), 2) two tangential inverse planning intensity-modulated radiotherapy (T-IMRT), and 3) multi-field IMRT (M-IMRT) carried out with seven beams. The planning target volume (PTV) and organs at risk (OARs), including heart, contralateral breast, contralateral lung and ipsilateral lung were delineated. The same dose constraints was used for all three plans with a prescribed PTV dose of 50 Gy. The volumetric doses of PTV and OARs were compared and analyzed using a dose volume histogram (DVH). The conformation number and homogeneity index were compared as well. Results: IMRT techniques found improved homogeneity and conformity of the dose to the target when compared to the TW. The M-IMRT found to significantly reduce the volume of the ipsilateral lung that receives 20 Gy when compared to the tangential techniques. For patients treated for the left breast, the M-IMRT and then T-IMRT, respectively, significantly reduced the percentage volume of the heart that received 30 Gy when compared to the TW. Conclusion: IMRT techniques achieve better results for PTV parameters and generally less dose to the OAR, although it increases the volume of the normal tissue that received a low dose.

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