Dissertations / Theses: 'Intensity modulated radiotherapy'

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Cufflin, Rebecca Sian. "Verification of Intensity Modulated Radiotherapy." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/25873/.

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The main aim of this work was to develop accurate and efficient methods for the verification of Intensity Modulated Radiotherapy (IMRT). IMRT is an advanced form of radiotherapy demanding extensive verification procedures to ensure treatments are delivered accurately. This requires comprehensive sampling of the complex dose distributions impacting on the tumour volume and radiationsensitive ‘organs at risk’. This work has focused on the use of electronic portal imaging devices (EPIDs) for verification purposes. Modern EPIDs are composed of a scintillator and an amorphous silicon detector panel with an array of photodiodes and thin film transistors. They are primarily used to verify the patient position during treatment by capturing transmission images, but they also have the potential to be used as efficient dose verification tools of high spatial resolution. Two complementary dose verification methods have been developed. One approach involves the calculation of portal dose using Monte Carlo (MC) methods. A MC model of the linear accelerator, in combination with the EPID, enables the dose to the detector to be predicted accurately and compared directly with acquired images. An alternative approach has also been developed. This utilises a clinical treatment planning system (TPS) to calculate the dose at the detector level, and convert this to predicted EPID intensity by application of a series of derived correction factors. Additionally, there have been numerous publications in the literature detailing problems in dosimetry caused by non-uniform backscatter to the imager from the model of detector support arm used in this work. Two novel methods to correct for this issue have been developed, a MC modelling solution and a matrix-based correction. These developed methods for IMRT dose verification have been applied both prior to and during treatment. When applied to pre-treatment verification, the MC solution is accurate to the 2%, 2 mm level (an average of 96% of points passing gamma criteria of 2%, 2 mm) and the TPS based method is accurate to the 3%, 3 mm level (an average of 98% of points passing gamma criteria of 3%, 3 mm). Both verification methods achieve acceptable verification results during treatment at the 5%, 5 mm level (average gamma pass rates of 97% and 96% being achieved for the MC and TPS based solutions respectively). Furthermore, in initial clinical studies, both techniques have identified dose delivery errors due to changes in patient position or patient anatomy.

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Bär, Werner. "Optimized delivery of intensity modulated radiotherapy." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965610934.

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Khadija, Murshed. "A clinical comparison and analysis between conventional MLC based and solid compensator based IMRT treatment techniques [electronic resource] /." Toledo, Ohio : University of Toledo, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=mco1264434257.

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Thesis (M.S.)--University of Toledo, 2009.
"In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Sciences." Title from title page of PDF document. Bibliography: p. 34-35.

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Seco, Joao Carlos. "Comparison of the efficacy of intensity modulated radiotherapy." Thesis, Institute of Cancer Research (University Of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398937.

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Williams, Matthew John Physics Faculty of Science UNSW. "Investigations into static multileaf collimator based intensity modulated radiotherapy." Awarded by:University of New South Wales. Physics, 2005. http://handle.unsw.edu.au/1959.4/20577.

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Intensity Modulated Radiation Therapy (IMRT) is a modern radiotherapy treatment technique used to obtain highly conformal dose distributions. The delivery of IMRT is commonly achieved through the use of a multileaf collimator (MLC). One of the hindrances at present to the widespread use of IMRT is the increased time required for its planning, delivery and verification. In this thesis one particular method of MLC based IMRT, known as Static Multileaf Collimator based IMRT (SMLC-IMRT), has been studied along with methods for improving it???s delivery efficiency. The properties of an MLC commonly used in SMLC-IMRT have been characterised. The potential ramifications of these properties on the dosimetric accuracy of the delivered IMRT field were also investigated. An Interactive Leaf Sequencing (ILS) program was developed that allowed for the manipulation and processing of intensity maps using a variety of methods. The objective of each method was to improve the delivery efficiency whilst maintaining the dosimetric quality of the IMRT treatment. The different methods investigated were collimator angle optimisation, filtration, and intensity level optimisation. The collimator was optimised by identifying the angle at which the minimum monitor unit???s (MU???s) were required when using a sliding-window delivery method. A Savitzky-Golay filter was applied to random intensity maps and suitable filtration parameters identified for filtering clinical IMRT fields, and the intensity levels were optimised based on a deviation threshold. The deviation threshold identified the acceptable level of difference tolerable between the original and modified intensity map. Several IMRT cases were investigated and the impact of each the methods on MU???s, segments and dose distribution observed. As the complexity of IMRT fields increases the dosimetric impact of the MLC properties increases. Complex SMLC-IMRT fields require longer delivery times due to the increased number of MU???s and segments. Collimator optimisation was shown to be a fast and effective means of improving delivery efficiency with negligible dosimetric change to the optimised plan. Modifying intensity maps by applying a filter and optimising the intensity levels did reduce the complexity and improve the delivery efficiency, but also required a dosimetric compromise of the optimised plan.

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Glendinning, Andrew D. "Studies of the dosimetric verification of intensity modulated radiotherapy." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/29383.

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The ability to verify absorbed dose distributions produced by intensity modulated radiotherapy (IMRT) using dynamic multileaf collimation is of great concern in the clinical application of this technique. This thesis investigates two approaches using an Elekta SL/ linear accelerator operating in dynamic mode (Elekta Oncology Systems, Crawley, UK). A novel strip ionisation chamber array, located at the beam aperture, was designed and used in conjunction with a specialised electrometer. This also recorded cumulative accelerator monitor units (MU) via an isolated interface to the accelerator. The chamber signal, recorded as a function of MU, proved suitable for collimator position verification for the case of a dynamic wedge, but was found not to be suitable for more general cases in which the leaves moved independently. A tube camera-based electronic portal imaging device (EPID) (Theraview , Cablon Medical, Leusden, The Netherlands) was investigated in a further approach to verification. This EPID has not been previously studied for dosimetry and several unreported effects associated with the video system were identified. The phosphor Gd202S:Tb, which is used as the x-ray detector, was also studied by direct measurements of luminescence using a photomultiplier tube. It was confirmed that the optical signal was independent of accelerator pulse repetition frequency, and that there was no long- lived luminescence (afterglow) following prolonged irradiation, which is of concern in dosimetry of dynamic deliveries. The EPID was applied to the verification of collimator position using a specially constructed camera interface that triggered recording of the cumulative MU. The EPID was also assessed as a method of measuring the integrated dose distribution delivered during a dynamic sequence, and a method proposed to overcome unreliable triggering of image acquisition in such cases. Dark current and persistence of the camera target were found to complicate measurements. Images were also found to exhibit optical scattering, which is an inherent characteristic of camera- based EPIDs. Results of a physical means of reducing the effect using an optical rejection screen were compared to an ionisation chamber for static and dynamic cases, and it was shown that the optical rejection screen is limited in its effectiveness in removing optical scatter. Dose profiles obtained from the EPID agree with ionisation chamber measurements in-air within 6 % for plain fields, and within 15-25 % for static and dynamically produced wedged fields. It was concluded that both approaches studied can be applied to the verification of IMRT but with limitations, and that an ideal system has yet to be found.

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Markovic, Miljenko. "Comparison of IMRT delivery methods a thesis /." San Antonio : UTHSC, 2008. http://learningobjects.library.uthscsa.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=58&CISOBOX=1&REC=13.

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Taylor, Alexandra. "Intensity-modulated radiotherapy for cervical cancer : optimising target volume definition and radiotherapy delivery." Thesis, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510901.

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Bhide, Shreeang Arvind. "Optimization of intensity modulated radiotherapy in head and neck cancer." Thesis, Institute of Cancer Research (University Of London), 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511161.

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Lei, Mary Wei-Ching. "Image guided intensity modulated radiotherapy in head and neck cancer." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600034.

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Image Guided Intensity Modulated Radiotherapy (IG-IMRT) incorporates novel imaging strategies into IMRT planning and delivery. FDG-PET/CT imaging may be used to identify potentially radioresistant tumour cell populations in head and neck cancer (HNC). Dose-painting with IMRT is a novel technique which provides an opportunity to widen the therapeutic window by dose escalation to radioresistant subvolumes. The purpose of this thesis was to evaluate the feasibility of th is technique, to provide methodology for identification of the FDG-avid region and to inform on a reasonable dose level to use in a future phase I clinical study investigating dose-painting to the FDG-avid target volume. This technique requires confidence in the quality of geometric and dosimetric accuracy of delivery and this issue was investigated in this thesis. Pre-clinical work included a comparison of five different FDG segmentation techniques. One of these techniques was used to identify the FOG-avid biological volume selected to receive dose-painting with IMRT in a planning study. Four dose levels were tested. Radiobiological modelling was used to determine an optimal dose level as the basis for a future clinical study and to determine the impact of using different FDG segmentation techniques. A clinical study was performed in patients with HNC to compare in -room volumetric imaging - cone beam computed tomography (CBCT) - with planar kilovoltage (kV) electronic portal imaging (EPI) for aspects of image guidance and to inform on appropriate planning margins. Pre-clinical work suggested that dose-painting with IMRT to the FOG-avid subvolume would be associated with increases in estimated tumour control probability (TCP) and with acceptable increases in normal tissue complication probability (NTCP). Verification using CBCT provided accurate data to guide treatment delivery and appropriate planning margins. The findings reported in this thesis provide valuable information that will inform the design of future clinical studies.

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Wu, Wing-cheung Vincent, and 胡永祥. "Inverse planning in three-dimensional conformal and intensity modulated radiotherapy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31246163.

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Curtin-Savard, Arthur. "Delivery and verification of intensity-modulated x-ray beams in radiotherapy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0023/NQ50138.pdf.

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Sivabalasingham, S. "Biological and clinical evaluation of intensity modulated radiotherapy for brain tumours." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1474887/.

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Intensity modulated radiotherapy has gained attention in recent years as a high precision radiation technique, allowing tumour dose escalation and reductions in high dose to adjacent normal organs. IMRT optimises the therapeutic ratio even further than conventional conformal radiation techniques, providing effective dose for tumour control, whilst minimising side effects. Despite these potential benefits, there is concern regarding long term effects from the associated low dose bath, exposing more normal tissue to lower radiation dose as compared to more conventional radiation techniques. However, the effects of this low dose radiation have yet to be established. In this thesis, y-H2AX was used to assess radiation-induced DNA damage within peripheral blood lymphocytes of patients undergoing fixed gantry or static field IMRT (SF-IMRT). The reproducibility and sensitivity of y-H2AX as a comparison of DNA damage following differing radiation techniques has been documented, with significant differences in y-H2AX foci seen following SF-IMRT in comparison to volumetric arc-IMRT and 3D conformal radiation. Efforts have been made to demonstrate a difference in whole body exposure from these techniques and variations in y-H2AX foci distributions seen following techniques may reflect greater whole body exposure following SF-IMRT, which may have impact on long term toxicity. The benefits of IMRT to treat complex shaped meningiomas, often located close to critical dose limiting structures, have been investigated in a clinical phase I/II study. The feasibility of using IMRT to deliver conformal radiation to meningiomas, whilst respecting normal tissue tolerance has been demonstrated here. The preliminary report from this ongoing clinical study documents effective, safe treatment with acceptable toxicity levels and comparable local control, particularly within grade I meningiomas. Prospective data collection has revealed improvements in neurological symptoms and no significant quality of life deterioration. The findings in this thesis provide further information to guide future work, examining the biological and clinical long term effects of new radiation techniques.

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Urbano, Maria Teresa Guerrero. "Evaluation of intensity modulated radiotherapy in head and neck and pelvic malignancies." Thesis, Institute of Cancer Research (University Of London), 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510356.

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Ho, Kean Fatt. "Optimising dose escalated intensity modulated radiotherapy (IMRT) in head and neck cancer." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508596.

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Cowley, Ian Richard. "New approaches to improving the accuracy and outcome of intensity modulated radiotherapy." Thesis, Open University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429545.

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Severaa aspects of the IMRT treatment chain are evaluated with a view to improving the accuracy with which the treatment can be delivered and also the radiobiological outcome for the patient. A safe, non-invasive way of evaluating patient repositioning for multi-fraction treatments is developed and presented, with results highlighting the head-and-neck immobilisation system that provides the best results at Addenbrooke's radiotherapy centre. Previously published dose evaluation metrics sre studied in depth, identifying ways in which they differ. A new method of calculating the popular Gamma index is proposed, along with a new Kappa index which can highlight areas of dose mismatch more readily than the Gamma index. Using a specially developed dose calculation system, systematic errors found with the IMRT treatment machines at Addenbrooke's are simulated to determine the dose differences created by these errors, which are then evaluated using the Kappa index with typical tolerances used by previous authors. The concept of equivalent uniform dose( EUD) is then used to assess whether the tolerances for distance and dose are equivalent to each other. They are found not to be equivalent, and better relative values of the two quantities are suggested for use in composite indices. The use of the EUD is extended further into analysing the equivalent dose differences of the treatment delivery errors previously calculated. It is found that the equivalent dose to the target volume is changed by more than the composite indices indicate. The EUD is then used to calculate normal tissue complication probabilities, the probability of uncomplicated control and therapeutic gain. It is found that the dose errors predicted can actually be beneficial to the patient outcome, although not always. It is concluded that dose evaluation for complex treatments such as IMRT should be more radiobiologically-based in order to assess patient outcomes properly.

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Hector, Charlotte Lianne. "The impact of patient movement on the delivery of intensity-modulated radiotherapy." Thesis, Institute of Cancer Research (University Of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268887.

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Coolens, Catherine. "A study of the complexity necessary for delivery of intensity-modulated radiotherapy." Thesis, Institute of Cancer Research (University Of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413746.

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Jena, Rajesh. "Optimisation of radiotherapy for patients with high-grade glioma using diffusion tensor imaging and intensity modulated radiotherapy." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614124.

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Tangboonduangjit, Puangpen. "Intensity-modulated radiation therapy dose maps the matchline effect /." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060724.095712/index.html.

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Chi, Alexander, Nam Nguyen, William Tse, Gill Sobremonte, Patrick Concannon, and Angela Zhu. "Intensity modulated radiotherapy for sinonasal malignancies with a focus on optic pathway preservation." BioMed Central, 2013. http://hdl.handle.net/10150/610183.

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PURPOSE:To assess if intensity-modulated radiotherapy (IMRT) can possibly lead to improved local control and lower incidence of vision impairment/blindness in comparison to non-IMRT techniques when treating sinonasal malignancies
what is the most optimal dose constraints for the optic pathway
and the impact of different IMRT strategies on optic pathway sparing in this setting.METHODS AND MATERIALS:A literature search in the PubMed databases was conducted in July, 2012.RESULTS:Clinical studies on IMRT and 2D/3D (2 dimensional/3 dimensional) RT for sinonasal malignancies suggest improved local control and lower incidence of severe vision impairment with IMRT in comparison to non-IMRT techniques. As observed in the non-IMRT studies, blindness due to disease progression may occur despite a lack of severe toxicity possibly due to the difficulty of controlling locally very advanced disease with a dose less than or equal to] 70Gy. Concurrent chemotherapy's influence on the the risk of severe optic toxicity after radiotherapy is unclear. A maximum dose of less than or equal to] 54Gy with conventional fractionation to the optic pathway may decrease the risk of blindness. Increased magnitude of intensity modulation through increasing the number of segments, beams, and using a combination of coplanar and non-coplanar arrangements may help increase dose conformality and optic pathway sparing when IMRT is used.CONCLUSION:IMRT optimized with appropriate strategies may be the treatment of choice for the most optimal local control and optic pathway sparing when treating sinonasal malignancy.

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Mu, Xiangkui. "Clinical application of intensity and energy modulated radiotherapy with photon and electron beams." Doctoral thesis, Umeå : Strålningsvetenskaper, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-443.

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Webster, Gareth John. "Intensity-Modulated Radiotherapy for the Head and Neck : Improvements in Planning and Delivery." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509060.

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Nguyen, Nam, Siyoung Jang, Jacqueline Vock, Vincent Vinh-Hung, Alexander Chi, Paul Vos, Judith Pugh, et al. "Feasibility of intensity-modulated and image-guided radiotherapy for locally advanced esophageal cancer." BioMed Central, 2014. http://hdl.handle.net/10150/610350.

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BACKGROUND:In this study the feasibility of intensity-modulated radiotherapy (IMRT) and tomotherapy-based image-guided radiotherapy (IGRT) for locally advanced esophageal cancer was assessed.METHODS:A retrospective study of ten patients with locally advanced esophageal cancer who underwent concurrent chemotherapy with IMRT (1) and IGRT (9) was conducted. The gross tumor volume was treated to a median dose of 70Gy (62.4-75Gy).RESULTS:At a median follow-up of 14months (1-39 months), three patients developed local failures, six patients developed distant metastases, and complications occurred in two patients (1 tracheoesophageal fistula, 1 esophageal stricture requiring repeated dilatations). No patients developed grade 3-4 pneumonitis or cardiac complications.CONCLUSIONS:IMRT and IGRT may be effective for the treatment of locally advanced esophageal cancer with acceptable complications.

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Hussien, Mohammad. "Evaluation of detector array technology for the verification of advanced intensity-modulated radiotherapy." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/808445/.

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Purpose: Quality assurance (QA) for intensity modulated radiotherapy (IMRT) has evolved substantially. In recent years, various ionization chamber or diode detector arrays have become commercially available, allowing pre-treatment absolute dose verification with near real-time results. This has led to a wide uptake of this technology to replace point dose and film dosimetry and to facilitate QA streamlining. However, arrays are limited by their spatial resolution giving rise to concerns about their response to clinically relevant deviations. The common factor in all commercial array systems is the reliance on the gamma index (γ) method to provide the quantitative evaluation of the measured dose distribution against the Treatment Planning System (TPS) calculated dose distribution. The mathematical definition of the gamma index presents computational challenges that can cause a variation in the calculation in different systems. The purpose of this thesis was to evaluate the suitability of detector array systems, combined with their implementation of the gamma index, in the verification and dosimetry audit of advanced IMRT. Method: The response of various commercial detector array systems (Delta4®, ArcCHECK®, and the PTW 2D-Array seven29™ and OCTAVIUS II™ phantom combination, Gafchromic® EBT2 and composite EPID measurements) to simulated deliberate changes in clinical IMRT and VMAT plans was evaluated. The variability of the gamma index calculation in the different systems was also evaluated by comparing against a bespoke Matlab-based gamma index analysis software. A novel methodology for using a commercial detector array in a dosimetry audit of rotational radiotherapy was then developed. Comparison was made between measurements using the detector array and those performed using ionization chambers, alanine and radiochromic film. The methodology was developed as part of the development of a national audit of rotational radiotherapy. Ten cancer centres were asked to create a rotational radiotherapy treatment plan for a three-dimensional treatment-planning-system (3DTPS) test and audited. Phantom measurements using a commercial 2D ionization chamber (IC) array were compared with measurements using 0.125cm3 ion chamber, Gafchromic film and alanine pellets in the same plane. Relative and absolute gamma index (γ) comparisons were made for Gafchromic film and 2D-Array planes respectively. A methodology for prospectively deriving appropriate gamma index acceptance criteria for detector array systems, via simulation of deliberate changes and receiver operator characteristic (ROC) analysis, has been developed. Results: In the event of clinically relevant delivery introduced changes, the detector array systems evaluated are able to detect some of these changes if suitable gamma index passing criteria, such as 2%/2mm, are used. Different computational approaches can produce variability in the calculation of the gamma index between different software implementations. For the same passing criteria, different devices and software combinations exhibit varying levels of agreement with the Matlab predicted gamma index analysis. This work has found that it is suitable to use a detector array in a dosimetry audit of rotational radiotherapy in place of standard systems of dosimetry such as ion chambers, alanine and film. Comparisons between individual detectors within the 2D-Array against the corresponding ion chamber and alanine measurement showed a statistically significant concordance correlation coefficient (ρc>0.998, p<0.001) with mean difference of -1.1%±1.1% and -0.8%±1.1%, respectively, in a high dose PTV. In the γ comparison between the 2D-Array and film it was found that the 2D-Array was more likely to fail in planes where there was a dose discrepancy due to the absolute analysis performed. A follow-up analysis of the library of measured data during the audit found that additional metrics such as the mean gamma index or dose differences over regions of interest can be gleaned from the measured dose distributions. Conclusions: It is important to understand the response and limitations of the gamma index analysis combined with the equipment and software in use. For the same pass-rate criteria, different devices and software combinations exhibit varying levels of agreement with the predicted γ analysis. It has been found that using a commercial detector array for a dosimetry audit of rotational radiotherapy is suitable in place of standard systems of dosimetry. A methodology for being able to prospectively ascertain appropriate gamma index acceptance criteria for the detector array system in use, via simulation of deliberate changes and ROC analysis, has been developed. It has been shown that setting appropriate tolerances can be achieved and should be performed as the methodology takes into account the configuration of the commercial system as well as the software implementation of the gamma index.

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Meyer, Jurgen. "Accommodating practical constraints for intensity-modulated radiation therapy by means of compensators." Thesis, Coventry University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369972.

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Hack, Joshua. "Development and implementation of quality-assurance standards for external beam intensity modulated radiation therapy." Toledo, Ohio : University of Toledo, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=mco1265034762.

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suh, yelin. "DEVELOPMENT AND INVESTIGATION OF INTENSITY-MODULATED RADIATION THERAPY TREATMENT PLANNING FOR FOUR-DIMENSIONAL ANATOMY." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1827.

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Lung cancer is the leading cause of cancer-related deaths worldwide. Radiotherapy is one of the main treatment modalities of lung cancer. However, the achievable accuracy of radiotherapy treatment is limited for lung-based tumors due to respiratory motion. Four-dimensional radiotherapy explicitly accounts for anatomic motion by characterizing the motion, creating a treatment plan that accounts for this motion, and delivering this plan to the moving anatomy. This thesis focuses on the current problems and solutions throughout the course of four-dimensional radiotherapy. For characterization of respiratory-induced motion, patient tumor motion data were analyzed. It is shown that tumor motion can be significant during radiotherapy treatment, and its extent, direction, and linearity vary considerably between patients, between treatment fractions, and between respiratory cycles. After this, approaches to four-dimensional intensity-modulated radiation therapy treatment planning were developed and investigated. Among the techniques to manage respiratory motion, tumor tracking using a dynamic multileaf collimator delivery technique was chosen as a promising method. A formalism to solve a general four-dimensional intensity-modulated radiation therapy treatment-planning problem was developed. Specific solutions to this problem accounting for tumor motion initially in one dimension and extending this to three dimensions were developed and investigated using four-dimensional computed tomography planning scans of lung cancer patients. For four-dimensional radiotherapy treatment delivery, accuracy of two-dimensional projection imaging methods was investigated. Geometric uncertainty due to the limitation of two-dimensional imaging in monitoring three-dimensional tumor motion during treatment delivery was quantified. This geometric uncertainty can be used to estimate proper margins when a single two-dimensional projection imager is used for four-dimensional treatment delivery. Lastly, tumor-tracking delivery using a moving average algorithm was investigated as an alternative delivery technique that reduces mechanical motion constraints of a multileaf collimator. Moving average tracking provides an approximate solution that can be immediately implemented for delivery of four-dimensional intensity-modulated radiation therapy treatment. The clinical implementation of four-dimensional guidance, intensity-modulated radiation therapy treatment planning, and dynamic multileaf collimator tracking delivery may have a positive impact on the treatment of lung cancer.

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Olofsson, Lennart. "Energy and intensity modulated radiation therapy with electrons." Doctoral thesis, Umeå : Department of Radiation Sciences, Radiation Physics, Umeå University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-491.

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Wake, Giulia M. G. H. "Exact minimisation of treatment time for the delivery of intensity modulated radiation therapy." University of Western Australia. School of Mathematics and Statistics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0195.

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This thesis investigates the exact minimisation of treatment delivery time for Intensity Modulated Radiation Therapy (IMRT) for the treatment of cancer using Multileaf Collimators (MLC). Although patients are required to remain stationary during the delivery of IMRT, inevitably some patient movement will occur, particularly if treatment times are longer than necessary. Therefore minimising the treatment delivery time of IMRT may result in less patient movement, less inaccuracy in the dosage received and a potentially improved outcome for the patient. When IMRT is delivered using multileaf collimators in 'step and shoot' mode, it consists of a sequence of multileaf collimator configurations, or shape matrices; for each, time is needed to set up the configuration, and in addition the patient is exposed to radiation for a specified time, or beam-on time. The 'step and shoot leaf sequencing' problems for minimising treatment time considered in this thesis are the constant set-up time Total Treatment Time (TTT) problem and the Beam-on Time Constrained Minimum Cardinality (BTCMC) problem. The TTT problem minimises a weighted sum of total beam-on time and total number of shape matrices used, whereas the BTCMC problem lexicographically minimises the total beam-on time then the number of shape matrices used in a solution. The vast majority of approaches to these strongly NP-hard problems are heuristics; of the few exact approaches, the formulations either have excessive computation times or their solution methods do not easily incorporate multileaf collimator mechanical constraints (which are present in most currently used MLC systems). In this thesis, new exact mixed integer and integer programming formulations for solving the TTT and BTCMC problems are developed. The models and solution methods considered can be applied to the unconstrained and constrained versions of the problems, where 'constrained' refers to the modelling of additional MLC mechanical constraints. Within the context of integer programming formulations, new and existing methods for improving the computational efficiency of the models presented are investigated. Numerical results for all variations considered are provided. This thesis demonstrates that significant computational improvement can be achieved for the exact mixed integer and integer programming models investigated, via solution approaches based on an idea of systematically 'stepping-up' through the number of shape matrices used in a formulation, via additional constraints (particularly symmetry breaking constraints) and via the application of improved bounds on variables. This thesis also makes a contribution to the wider field of integer programming through the examination of an interesting substructure of an exact integer programming model. In summary, this thesis presents a thorough analysis of possible integer programming models for the strongly NP-hard 'step and shoot' leaf sequencing problems and investigates and applies methods for improving the computational efficiency of such formulations. In this way, this thesis contributes to the field of leaf sequencing for the application of Intensity Modulated Radiation Therapy using Multileaf Collimators.

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Naik, Mehul S. "Dose calculation of megavoltage IMRT using convolution kernels extracted from GafChromic EBT film-measured pencil beam profiles : a dissertation /." San Antonio : UTHSC, 2006. http://proquest.umi.com/pqdweb?did=1251893631&sid=1&Fmt=2&clientId=70986&RQT=309&VName=PQD.

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Pow, Ho-nang Edmond. "Oral health and quality of life after intensity-modulated head and neck radiotherapy for nasopharyngeal carcinoma /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36749333.

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Pow, Ho-nang Edmond, and 鮑浩能. "Oral health and quality of life after intensity-modulated head and neck radiotherapy for nasopharyngeal carcinoma." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B4501565X.

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Sakanaka, Katsuyuki. "Dosimetric advantage of intensity-modulated radiotherapy for whole ventricles in the treatment of localized intracranial germinoma." Kyoto University, 2012. http://hdl.handle.net/2433/157445.

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Ishida, Yuichi. "Intensity-modulated radiotherapy for cervical esophageal squamous cell carcinoma without hypopharyngeal invasion: dose distribution and clinical outcome." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/245831.

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京都大学
0048
新制・課程博士
博士(医学)
甲第22146号
医博第4537号
新制||医||1039(附属図書館)
京都大学大学院医学研究科医学専攻
(主査)教授大森孝一, 教授富樫かおり, 教授武田俊一
学位規則第4条第1項該当
Doctor of Medical Science
Kyoto University
DFAM

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36

Andræ, Nils. "Commissioning and validation of small subfields in Step-and-shoot IMRT." Thesis, Stockholm University, Medical Radiation Physics (together with KI), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8316.

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One of the most used irradiation techniques in modern radiation therapy is step-and-shoot IMRT. The accuracy of this technique when delivering complex dose distributions strongly depends on the size of the subfields. The aims of this study is to determine the minimum size of subfields that can be used efficiently in Step-and-Shoot IMRT, to investigate the validation process for beam delivery and treatment planning dose calculations, and to find recommendations for practical clinical implementations.

Two different detectors, a CC04 ion chamber and a SFD stereotactic diode, have been used for measuring head scatter factors in air (Sc), total output factors (Scp) and dose profiles in water for a wide range of field sizes. The measurements were compared to calculations done with a pre-release version of the Nucletron MasterPlanTM v 3.1 treatment planning system that employs a novel, high resolution fluence modelling for both its pencil beam and collapsed cone dose calculation algorithms. Collimator settings were explicitly checked using FWHM film measurements with a build-up sheet of tungsten placed close to the treatment head to reduce the influence from lateral electron transport and geometrical penumbra. An analysis of the influence and sensitivity of Scp for small fields with respect to the linear accelerator source size and shape was also made.

The measurements with the ionization chamber and the stereotactic diode showed good agreements with each other and with the treatment planning system calculations for field sizes larger than 2×2 cm2. For small field sizes, measurements with different detectors yielded different results. Calculations showed agreements with measurements with the smallest detector, provided careful field size calibration and commissioning of calculation parameters. Uncertainties in collimator settings and source characteristics were shown to yield large uncertainties in Scp for fields smaller than 2×2 cm2.

The treatment planning system was found to properly handle small subfields but results were very sensitive to uncertainties in source size, as well as calibration and reproducibility of the collimator settings. Therefore if subfields smaller than 2×2 cm2 are to be used in IMRT extra care should be taken to determine the source characteristics and to calibrate the collimators. The volume of the detectors used for validation of such small fields and the loss of charged particle equilibrium conditions also have to be taken into consideration.

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37

Champion, Heather. "Beam angle and fluence map optimization for PARETO multi-objective intensity modulated radiation therapy treatment planning." Medical Physics, 2011. http://hdl.handle.net/1993/8910.

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In this work we introduce PARETO, a multiobjective optimization tool that simultaneously optimizes beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning using a powerful genetic algorithm. We also investigate various objective functions and compare several parameterizations for modeling beam fluence in terms of fluence map complexity, solution quality, and run efficiency. We have found that the combination of a conformity-based Planning Target Volume (PTV) objective function and a dose-volume histogram or equivalent uniform dose -based objective function for Organs-At-Risk (OARs) produced relatively uniform and conformal PTV doses, with well-spaced beams. For two patient data sets, the linear gradient and beam group fluence parameterizations produced superior solution quality using a moderate and high degree of modulation, respectively, and had comparable run times. PARETO promises to improve the accuracy and efficiency of treatment planning by fully automating the optimization and producing a database of non-dominated solutions for each patient.

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38

Shin, Naomi. "Modeling secondary cancer risk following paediatric radiotherapy: a comparison of intensity modulated proton therapy and photon therapy." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106431.

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Proton radiotherapy is known to reduce the radiation dose delivered to normal healthy tissue compared to photon techniques. The increase in normal tissue sparing could result in fewer acute and late effects from radiation therapy. In this work proton therapy plans were created for patients previously treated using photon therapy. Intensity modulated proton therapy (IMPT) plans were planned using inverse planning in Varian's Eclipse treatment planning system with a scanning proton beam model to the same relative biological effectiveness (RBE)-weighted prescription dose as the photon plan. Proton and photon plans were compared for target dose conformity and homogeneity, body volumes receiving 2 Gy and 5 Gy, integral dose, dose to normal tissues and second cancer risk. Secondary cancer risk was determined using two methods. The relative risk of secondary cancer was found using the method described by Nguyen et al. by applying a linear relationship between integral dose and relative risk of secondary cancer. The second approach used Schneider et al.'s organ equivalent dose concept to describe the dose in the body and then calculate the excess absolute risk and cumulative risk for solid cancers in the body.IMPT and photon plans had similar target conformity and homogeneity. However IMPT plans had reduced integral dose and volumes of the body receiving low dose. Overall the risk of radiation induced secondary cancer was lower for IMPT plans compared to the corresponding photon plans with a reduction of ~36% using the integral dose model and ~50% using the organ equivalent dose model.
Un avantage connu de la radiothérapie par protons est la réduction de la dose reçue par les tissus normaux et sains par rapport aux traitements en photons. Cette réduction de dose peut résulter en une diminution des effets aigus et tardifs de la radiothérapie. Dans cet ouvrage, les plans de protonthérapie ont été créés pour des patients ayant été traités par radiothérapie en photons. Les plans de protonthérapie conformationnelle avec modulation d'intensité (PCMI) ont été conçus par planification inverse dans le système de planification de traitement Eclipse de Varian de façon à ce que le faisceau de protons en balayage produise la même dose de prescription que plan en photons, tout en tenant compte des efficacités biologiques relatives des deux types de radiation. Les plans en photons et en protons ont ensuite été comparés en termes de conformité de la dose, d'homogénéité de la dose, de volumes recevant 2 et 5 Gy, de dose intégrale, de dose aux tissus normaux et de risque de cancer secondaire. Le risque relatif de cancer secondaire a été determiné par la méthode décrite par Nguyen et al. en applicant une relation linéaire entre la dose intégrale et le risque relatif de cancer secondaire. Une deuxième approche employée dans cet ouvrage utilise le concept de dose équivalente à un organe de Schneider et al. pour décrire la dose dans le corps et par la suite calculer l'excès de risque absolu et le risque cumulatif de cancers solides dans le corps. Les traitements comparés, soit en photons et en protons, ont démontré une conformité et une homogénéité de la dose similaires dans le volume cible. Toutefois, les plans de PCMI réduisent la dose intégrale et diminuent les volumes du corps recevant une faible dose. Globalement, le risque d'induction d'un cancer secondaire est plus faible pour les plans de PCMI que pour les plans équivalents en photons avec une réduction de ~36% en utilisant le modèle de dose intégrale et ~50% en utilisant le modèle de dose équivalente à un organe.

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39

Ahmad, Khalil Dalia Abdel-Moaty [Verfasser]. "Accelerated Intensity Modulated Radiotherapy using Simultaneous Integrated Boost (SIB-IMRT) versus Intensity Modulated Hyperfractionated Accelerated Radiotherapy using Sequential Field (HART-SEQ-IMRT) for primary treatment in patients with locally advanced head and neck Squamous Cell Carcinoma / Dalia Abdel-Moaty Ahmad Khalil." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2012. http://d-nb.info/1027275826/34.

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40

Moreno, Miriam Zarza. "Monte Carlo simulations for dosimetric verification in photon and electron beam radiotherapy." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/7835.

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Dissertação para obtenção do Grau de Doutor em Engenharia Biomédica
One of the primary requirements for successful radiotherapy treatments is the accurate calculation of dose distributions in the treatment planning process. Monte Carlo (MC) dose calculation algorithms are currently recognized as the most accurate method to meet this requirement and to increase even further dose accuracy. The improvements in computer processor technology and the development of variance reduction techniques for calculations have led to the recent implementation and use of MC algorithms for radiotherapy treatment planning at many clinical departments. The work conducting to the present thesis consists of several dosimetric studies which demonstrate the potential use of MC dose calculations as a robust tool of dose verification in two different fields of external radiotherapy: electron and photon beam radiotherapy. The first purpose of these studies is to evaluate dose distributions in challenging situations where conventional dose calculation algorithms have shown some limitations and it is very difficult to measure using typical clinical dosimetric procedures, namely in regions containing tissue inhomogeneities, such as air cavities and bones, and in superficial regions. A second goal of the present work is to use MC simulations to provide a detailed characterization of photon beams collimated by a multileaf collimator (MLC) in order to assess the dosimetric influences of these devices for the MC modeling of Intensity Modulated Radiotherapy (IMRT) plans. Detailed MC model of a Varian 2100 C/D linear accelerator and the Millenium MLC incorporated in the treatment head is accurately verified against measurements performed with ionization chambers and radiographic films. Finally, it is also an aim of this thesis to make a contribution for solving one of the current problems associated with the implementation and use of the MC method for radiotherapy treatment planning, namely the clinical impact of converting dose-to-medium to dose-to-water in treatment planning and dosimetric evaluation. For this purpose, prostate IMRT plans previously generated by a conventional dose algorithm are validated with the MC method using an alternative method, which involves the use of non-standard CT conversion ramps to create CT-based simulation phantoms.
Fundação para a Ciência e Tecnologia; Centro de Física Nuclear da Universidade de Lisboa

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41

Helal, Azza Mahmoud. "The effect of patient anatomy on optimised intensity modulated radiotherapy dose distributions for head and neck and prostate cancer." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438639.

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42

Gomarteli, Kaga [Verfasser], and Frederik [Akademischer Betreuer] Wenz. "Second cancer risk after intensity-modulated and conventional radiotherapy in a small animal model / Kaga Gomarteli ; Betreuer: Frederik Wenz." Heidelberg : Universitätsbibliothek Heidelberg, 2021. http://d-nb.info/1227585578/34.

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43

Kawamura, Mitsue. "A scoring system predicting acute radiation dermatitis in patients with head and neck cancer treated with intensity-modulated radiotherapy." Kyoto University, 2019. http://hdl.handle.net/2433/244519.

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44

Chiu, Siu-hau, and 招兆厚. "A search for optimal radiation therapy technique for lung tumours stereotactic body radiation therapy (SBRT) : dosimetric comparison of 3D conformal radiotherapy, static gantry intensity modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) with flattening filter (FF) or flattening filter-free (FFF) beams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196549.

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Materials/Methods: Ten patients who underwent thoracic SBRT with primary stage I (T1/2N0) lung cancer or oligometastatic lung lesion, with PTV diameter ≤ 5cm were selected and were immobilized with Easyfoam or Vac-Lock. Planned/treated with inspiratory breath-hold (25 seconds, 70 to 80% of vital capacity) assisted with Active Breathing Control (ABC). Four treatment plans: non-coplanar 3DCRT, coplanar static gantry IMRT, coplanar VMAT (FF) and VMAT (FFF) were generated. Field arrangements, either static fields or partial arcs (duration=20 sec) were used to avoid direct beam entry to contralateral lung. All plans were compared in terms of dosimetric performance included dose to PTV or organs at risk (OAR), high/low dose spillage, integral dose (body and lungs), dose delivery efficiency (MU/Gy) and estimated beam-on time (BOT) with reference to the RTOG 0813 protocol. Results: All plans complied with RTOG 0813 protocol. VMAT (FF/ FFF) techniques improved target coverage and dose conformity, with the highest conformity number (CN > 0.91), compared to IMRT (0.88) and 3DCRT (0.85). The control of high dose spillage (NT>105% and CI) for IMRT (3.04% and 1.08) and VMAT (FF/ FFF) (1.08/ 1.06% and 1.03/ 1.04) techniques were comparable (p > 0.05) and significantly better than 3DCRT (4.22% and 1.11, p < 0.005) technique. In addition, VMAT (FF/ FFF) techniques performed the best in controlling low dose spillage (D2cm and R50%) compared with IMRT (reduction: 4.7%, p=0.036 and >5.9%, p = 0.009) and 3DCRT (reduction: > 16.3%, p < 0.001 and > 10%, p = 0.002). Benefits of rapid and isotropic dose fall-off were shown from superior tissue sparing (reduction ranges from 3.2% up to 67%) of ipsilateral brachial plexus, skin (0-5mm), great vessels and ribs. Also lung V10, V12.5, esophagus and heart tend to receive lower dose with VMAT technique. The relatively lower integral dose to whole body (> 3Gy∙L reduction, p < 0.013) and ipsilateral lung (0.65Gy∙L reduction, p = 0.025) compared with 3DCRT, were associated with lower risk of radiation induced cancers. The MU/Gy and BOT were substantial lower for VMAT (FF) (22.4% and 32.4%) compared with IMRT. Apart from higher (7%) maximum skin dose, dosimetric performance for VMAT (FFF) was comparable with VMAT (FF), with advantages of further reduction of MU/Gy (1.8% lesser), partial arc numbers (from 12-14 arcs down to 8 arcs) and BOT (35% shortened), owing to the increased dose output with flattening filter removal. Conclusions: VMAT (FF and FFF) plans maintained IMRT equivalent plan qualities, simultaneously enhanced the delivery efficiency with shortened BOT. VMAT (FFF) further reduced the required arcs number and BOT, significantly minimized the intra-fraction motions and more tolerable to patient with long SBRT treatment duration.
published_or_final_version
Medicine
Master
Master of Medical Sciences

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45

Javedan, Khosrow. "Investigation of Buildup Dose for Therapeutic Intensity Modulated Photon Beams in Radiation Therapy." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3449.

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Buildup dose of Mega Voltage (MV) photon beams can be a limiting factor in intensitymodulated radiation therapy (IMRT) treatments. Excessive doses can cause patient discomfort and treatment interruptions, while underdosing may lead to local failure. Many factors which contribute to buildup dose, including the photon beam energy spectrum, scattered or contaminant radiation and their angular distribution, are not modeled well in commercial treatment planning systems. The accurate Monte Carlo method was employed in the studies to estimate the doses. Buildup dose of 6MV photon beams was investigated for three fundamentally different IMRT modalities: between Helical TomoTherapy and traditional opposed tangential beams, solid IMRT and multileaf collimator (MLC)-based IMRT techniques. Solid IMRT, as an alternative to MLC, achieves prescription dose distribution objectives, according to our study. Measurements and Monte Carlo calculations of buildup dose in chest wall treatment were compared between TomoTherapy IMRT and traditional tangential-beam technique. The effect of bolus in helical delivery was also investigated in this study. In addition, measurements and Monte Carlo calculations of buildup dose in solid IMRT and MLC based IMRT treatment modalities were compared. A brass step compensator was designed and built for the solid IMRT. Matching MLC step sequences were used for the MLC IMRT. This dissertation also presents the commissioning of a Monte Carlo code system, BEAMnrc, for a Varian Trilogy linear accelerator (LINAC) and the application in buildup dose calculation. Scattered dose components, MLC component dose and mean spectral energy for the IMRT treatment techniques were analyzed. The agreement between measured 6MV and calculated depth dose and beam profiles was (± 1% or ±1 mm) for 10x10 and 40x40 cm2 fields. The optimum electron beam energy and its radial distribution incident on tungsten target were found to be 6 MeV and 1 mm respectively. The helical delivery study concluded that buildup dose is higher with TomoTherapy compared to the opposed tangential technique in chest wall treatment. The solid and MLC IMRT comparison concluded that buildup dose was up to 7% lower for solid IMRT compared to MLC IMRT due to beam hardening of brass.

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Nutting, Christopher. "Can intensity-modulated radiotherapy (IMRT) be used to reduce toxicity and improve tumour control in patients with head and neck cancer?" Thesis, City University London, 2012. http://openaccess.city.ac.uk/1128/.

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Radiotherapy is commonly used in the treatment of head and neck cancer. For early stage tumours, conventional radiotherapy techniques have a high cure rate and low levels of long-term complications. Patients with more advanced cancers have much lower cure rates and high levels of treatment-related complications. Intensity modulated radiotherapy (IMRT) is a new form of focussed radiation therapy. It has been used to reduce the radiation dose to normal tissue structures and increase the dose delivered to tumour bearing tissues. This potentially allows reduced side effects and increased tumour control compared to conventional radiotherapy. The rationale of this thesis was to test whether these twin goals could be achieved in head and neck cancer patients. The first part of the thesis describes improvements in patient immobilisation, optimisation of techniques for neck irradiation, and evaluation of the technique in a busy radiotherapy department. It includes pre-clinical evaluation of IMRT for different tumour sites, the development of quality assurance programs and the conduct of a national randomised controlled trial of parotid-sparing IMRT. This trial concluded that IMRT significantly reduced patient-reported xerostomia, allowed recovery of saliva production and improved quality of life. The second part of the thesis describes pre-clinical evaluation of techniques to escalate radiation dose in patients with larynx and hypopharynx tumours. A phase I/II clinical trial showed that higher doses of radiation can be delivered at the expense of an increase in acute radiation toxicity but without a measurable increase in late radiation side effects. In the larynx and hypopharynx groups, a possible increase in local control was observed. This thesis describes the process of evaluation of a new radiotherapy technology and could be used as a template for testing other new technologies in the future.

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Inokuchi, Haruo. "Clinical effect of multileaf collimator width on the incidence of late rectal bleeding after high-dose intensity-modulated radiotherapy for localized prostate carcinoma." Kyoto University, 2016. http://hdl.handle.net/2433/215942.

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Johansson, Jonas. "Comparative Treatment Planning in Radiotherapy and Clinical Impact of Proton Relative Biological Effectiveness." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6593.

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McKenna, Frederick W. "Studies of cell survival curve fitting, effective doses for radiobiological evaluation in SBRT treatment techniques and the dependence of optical density growth in Gafchromic EBT film used in IMRT." Oklahoma City : [s.n.], 2009.

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50

Ikeda, Itaru. "Assessment of interfractional prostate motion in patients immobilized in the prone position using a thermoplastic shell." Kyoto University, 2014. http://hdl.handle.net/2433/188682.

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Dissertations / Theses on the topic 'Intensity modulated radiotherapy'

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