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Assessment of developed IMRT and 3D-CRT planning protocols for treating nasopharyngeal cancer patients based on the target and organs at risks common volumes
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Gh. Sharbo   , B. Hashemi , M. Bakhshandeh , A. Rakhsha |
| Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran , bhashemi@modares.ac.ir |
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Abstract: (1726 Views) |
Background: Various developed intensity modulated radiation therapy (IMRT) and a three dimensional conformal radiation therapy (3D-CRT) protocols were assessed for treating nasopharyngeal cancer (NPC) based on radiobiological parameters. Materials and Methods: Treatment plans were made for 30 NPC patients using 15 developed IMRT and 3D-CRT protocols. The IMRT protocols comprised of three 7-fields with various collimator (0°, 5°, and 10°) and couch (0°, 4°, 8°, 12°) angles. The 3D-CRT technique included two phases. In the 1st phase a dose of 60 Gy was prescribed to the total PTV, but in the 2nd phase a dose of 10 Gy was prescribed to the PTV-70. The tumour control probability (TCP), normal tissues complication probability (NTCP), and complication-free tumor control probability (P+) parameters were estimated for assessing the IMRT protocols. Then, the ideal protocol (s) were proposed through comparing the IMRT protocols with each other and 3D-CRT protocol based on TCP, NTCP, and P+ values. Results: The IMRT protocol with 10° collimator and 8° couch angles had the lowest NTCP mean values. Significant differences were observed among the mean NTCP values for the brainstem and parotid glands, and P+ of the developed IMRT and 3D-CRT protocols. However, no significant differences were observed among the mean NTCP values for the spinal cord, optic chiasm and optic nerves among the protocols. Conclusions: The 3D-CRT protocol had a good outcome for the NPC patients having a lower common volume between their total planning target volume and OARs, while the results of the IMRT showed the opposite.
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| Keywords: Nasopharyngeal carcinoma, intensity modulated radiation therapy, 3D radiation therapy, treatment planning, radiobiological models. |
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Full-Text [PDF 1817 kb]
(954 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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