الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 76 |  |  |
| | | from | 76 | | |
Abstract
Three-dimensional conformal radiotherapy treatment planning is used in treatment of malignant tumors. It delivers a homogeneous dose of radiation to a tumor, while delivers
a dose as low as possible to healthy surrounding tissues.
This study includes fifty patients with different malignant tumors selected from head, chest, abdomen and Pelvis. For each patient different radiotherapy treatment planning techniques were carried out to achieve the optimum plan for the specific target volume. This work was done using 3D treatment planning system, Clinical Oncology and Nuclear Medicine Department, Faculty of Medicine, Alexandria University, Egypt.
The aim of this study was to determine the suitable treatment techniques for each patient. Due to presence of a local area computer network, patient data and CT images were transferred from CT simulator to TPS where radiation techniques were carried out. The target volumes and OAR were delineated in all CT slices.
Planning parameters were adjusted to ensure delivering a homogenous dose of radiation to tumor, while delivering a dose as low as possible to healthy surrounding tissues.
MLC was used in all radiation techniques with computer control for shaping the radiation beams to conform exactly to target volume to ensure protects surrounding normal tissues. Different photons energy (4, 6 and 15MV) was used.
Comparison and evaluation procedures between different techniques for each patient were carried out. PTV coverage by 95% of prescribed dose, the dose conformity to tumor and OAR tolerance doses were compared. DVH for volum
es versus dose, DVH parameters and inspection of isodose distribution were used.
Results demonstrated that for smaller target volume, multiple radiation beams improve dose distribution to PTV and reduced the dose to OAR, on the other hand it is better to use few radiation beams for large target volumes. In some cases, different radiation directions could be used to avoid high exposure to the OAR. According to site of tumor, the change of beam energy could improve dose distribution. According to size
of tumor and lactation of OAR, change in the number of beams and direction could improve dose distribution.
In Conclusions
Three-dimensional conformal radiotherapy plans were evaluated for 50 patients with different malignant tumors, multiple techniques were carried out for each patient.
The treatment planning parameters affect the dose distribution outcome, so the correct selection improves the dose distribution.
Precise and correct selection of beam directions shows better sparing of OAR.
For smaller
target volume, multiple radiation beams improve dose distribution to PTV and reduced the dose to OAR. On the other hand it is better to use few radiation beams for large target volume.
In some cases, different radiation directions could be used to avoid high exposure to the OAR. According to site of tumor, change beam energy could improve dose distribution. According to size of tumor and location of OAR, the change in the number of beams could improve dose distribution.
Non coplanar beams can improve the
dose distribution for some brain lesions.
In designed techniques, acceptable coverage of dose distribution to PTV with low dose to sensitive structures was achieved. On the other hand there were unacceptable dose distributions to PTV with high doses to OAR.
DVH is considered as a faster and excellent evaluator for all plans, so it is used to select optimum plan