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Title: Validation of Dose Distribution in Three Dimensional Conformal Radiation Therapy
Authors: Akram, Muhammad
Keywords: Physical Sciences
Issue Date: 2020
Publisher: Islamia University, Bahawalpur.
Abstract: Three dimensional conformal radiation therapy treatment systems have encouraged the accomplishment of EB radiation therapy modalities. Regions of high radiation dose in patients can be conformed efficiently and accurately by employing these techniques. This thesis is shifted into three main investigations, focusing on validation of 3D dose distribution in conformal radiotherapy. Firstly, development of powerful but relatively inexpensive computer systems which contains spatial registration (fusion) of 3D images from different modalities, most commonly CT, MRI, is a major area of research for radiology and radiation oncology. This part of thesis examines the utility of integrating images from Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) and compare Gross tumor volume (GTV) delineated in CT and CT-MRI fused image data sets separately. Delineation of GTV defined by fusing the two imaging modalities is an important step and could provide significant difference using CT and CT-MRI fused image data sets. In this study twenty two patients suffering from Brain Gliomas were evaluated using CT and CT/MRI images. Match points Registration method is used for. The GTV of CT-MRI fused images was large as compared to CT images with mean volume of (Mean±SD: 112.67±74.73 cc) and 102.15±64.88 cc respectively. Difference observed for GTV is 10.52±10.05 cc (p= 0.004). After taking CT-MRI fused image as reference, calculated mean percentage difference in volumes was about 12%. It was found that GTV was larger on CT-MRI image for brain Gliomas than CT image. Therefore, the fusion of two imaging modalities is recommended for accurate delineation of GTV in radiation therapy treatment planning of brain tumor. Secondly, this thesis contains dose distribution in the phantoms as current practices in radiation therapy required high doses of radiation to be delivered with increased accuracy. Treatment planning task is exercised till an optimum conformal dose distribution is achieved. The present reported work was performed to compare the various aspects of the cobalt-60 radiation beam therapy with fixed source-surface distance 70cm incident normally. This study was conducted at the department of radiation Physics of MD Anderson Cancer Centre, University of Texas, Houston, United States. Radiation doses were P a g e | vii calculated in a solid phantom as well as in water phantom at different square field sizes and depths. It was noted that the rate of absorbed dose increased with the increase in the field size and decreased with the increase in depths. The rate of absorbed dose was found to be directly proportional to the increase in the square field size and inversely proportional to the increase in depth. Moreover, the solid phantom demonstrated more absorbed doses as compared to the water phantom. Third part of the thesis contains TPS which have capabilities for the betterment of patient health. The expected radiotherapy exposed to contra-lateral breast during delivery to primary diseased site is of major findings. It was planned to examine the consequences of physical wedge (PW) and enhanced dynamic wedges (EDW) on contra-lateral breast dose employing high energy photon energies. The Varian's Clinac model 2100 C/D and Siemen's Primus accelerators were used with 6 MV and 15 MV energies. Sixty five patients with cancerous breast as well as chest wall were considered and their contra-lateral doses were calculated at a point 5 cm across, at 2 cm depth from medial field end. The contra-lateral breast dose mean difference was 0.25 cGy and 0.24 cGy in comparison of physical and enhanced dynamic wedge on Varian's Clinac and 0.19 cGy and 0.18 cGy were establish for medial enhanced dynamic wedge (EDW) and without medial enhanced dynamic wedge for the same device in breast cases and chest wall cases respectively as per entire prescribed radiation dose. The mean difference for physical wedge (Clinac) and physical wedge (Primus) was examined as 0.08 cGy and 0.31 cGy and during the evaluation of medial physical wedge and without medial physical wedge on primus machine, this mean difference was found as 0.25 cGy and 0.51 cGy in breast cases and chest wall cases respectively as per whole prescribed dose. Conclusion: The investigation shows the importance that the enhanced dynamic wedge gives less radiation dose, which leads to second breast malignancy, compared to physical wedge. In addition to these findings, the medial wedge can produce second breast malignancy also and should not be dealt in future planning. So this project offers a number of key results that enhance the validation of 3D radiations dose distributions in conformal radiation therapy.
Gov't Doc #: 21469
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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