Abstract
Introduction: Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. So, if there was any structure along the treatment beam path not delineated, it would not be taken into account during that calculation process. During IMRT routine practical work, it is noticed that there are some non-delineated normal tissue volumes that received un-aimed dose. Aim: The purpose of this study was to study the effect of unusually delineated normal volumes in IMRT treatment for left sided breast cancer. Method: Ten left sided breast cancer patients were planned with IMRT inverse planning system. The unusually delineated normal volumes were delineated and taken into account in IMRT dose constraints as an Organ at Risk. Doses received by that volume were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that doses received by the unusually delineated volume when they were delineated and taken into account in IMRT dose constraints were significantly higher than when they were not. Conclusions: The results showed that for IMRT planning technique used for treating left-sided breast cancer, all of the normal tissues/structures that are closed to the treatment targets must be delineated and taken into account in the IMRT planning dose constraints.
Highlights
Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints
Tumor volumes such as gross target volume (GTV), clinical target volume (CTV), and planning target volume (PTV) [9] as well as Organs at Risk (OARs) had been delineated by the physician on each axial slice, Computed Tomography (CT) slices were transferred to the treatment planning system (TPS)
XiO employs a conjugate gradient algorithm to search for the minimum value of the cost function, which was a member of the gradient descent family of optimization methods, where variables were changed systematically, as opposed to stochastic methods where variables were changed randomly
Summary
Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. The unusually delineated normal volumes were delineated and taken into account in IMRT dose constraints as an Organ at Risk. Results: The results showed that doses received by the unusually delineated volume when they were delineated and taken into account in IMRT dose constraints were significantly higher than when they were not. Conclusions: The results showed that for IMRT planning technique used for treating left-sided breast cancer, all of the normal tissues/structures that are closed to the treatment targets must be delineated and taken into account in the IMRT planning dose constraints. The changing of beam intensity is computer controlled Delineation of both clinical target volumes and organs at risk is very important when in IMRT in order to achieve its required results [4]-[6]
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