Respiratory gating limits the radiation to a specific part of the breathing cycle and reduces the size of the Planning Target Volume (PTV). This thesis describes a novel quality assurance method for amplitude gating of Stereotactic ABlative Ra- diotherapy (SABR) treatments of liver delivered using Volumetric Modulated Arc Therapy (VMAT) using a 10 MV beam in Flattening Filter Free (FFF) mode. This method takes advantage of the high dose gradient region of SABR treatments to detect any inaccuracies in the performance of the Varian Real-time Position Manage- ment (RPM) gating system. This study involves the design and construction of an interface that connects the translation stage of the Quasar respiratory motion phan- tom to an ion chamber insert. This insert can hold and drive a pinpoint ion chamber inside the ArcCheck diode array based on the breathing pattern imported into the Quasar phantom. The pinpoint ion chamber dose measurements were acquired at the isocentre and along the penumbra using synthetic breathing traces. Our results show that the changes in PTV size and exhale duration do not influence the dose measured by iii the pinpoint ion chamber. Changes in gate width and baseline drift, however, affect the detector residual motion, which results in variation in the level of dose-blurring and interplay effects. A new parameter, Average Residual Detector Displacement (ARDD), is introduced in this thesis and is used to take into account the effect of dose-blurring. For gate widths smaller than 8 mm and baseline drift levels smaller than 4 mm, if the effect of dose-blurring is taken into account, the pinpoint ion chamber dose measurements are mostly within 2σ positional uncertainty from the Eclipse dose profile. As the gate width and baseline drift increases, accounting for the dose-blurring effect is no longer sufficient to explain the discrepancy between measured and calculated doses. This thesis also includes dose measurements for radiation deliveries that are gated using six real breathing traces with gate widths of 2 mm, 2.8 mm, and 4 mm. Once the parameter ARDD is used to account for dose-blurring, the dose measurements are mostly within 2σ positional uncertainty from Eclipse calculated doses. These results demonstrate the reliability and accuracy of the RPM gating system at British Columbia Cancer Agency - Vancouver Island Cancer Centre (BCCA - VICC). Lastly, the overall dose distribution was monitored using the ArcCheck diode array measure- ments under various gating schemes and was compared to the Eclipse calculated dose map using a 2D Gamma analysis. The Gamma pass rates for 2mm/2% criteria show that the beam interruptions during the treatment do not degrade the fidelity of the radiation delivery in a gated treatment. / Graduate

Volumetric modulated arc therapy (VMAT) is a technique for the delivery of intensity modulated radiotherapy (IMRT) whereby the linear accelerator (linac) delivers dose continuously while rotating around the patient. VMAT has gained attention due to its ability to produce complex dose distributions, deliverable in a much shorter treatment time than IMRT. The purpose of this thesis was to investigate the clinical application of VMAT, and to identify any benefits over IMRT in the areas of treatment planning, delivery, and imaging. A VMAT planning strategy was developed which demonstrates that complex dynamic arc deliveries can be sequenced from static, IMRT-based control points. For prostate patients, the VMAT solution demonstrated superior sparing of critical structures compared to IMRT plans. A further comparison of VMAT and IMRT was performed with the development of an automated planning methodology, which aimed to reduce the impact of planner bias. Applied over a series of nasopharynx patients, the technique showed that VMAT achieved an improvement in parotid sparing compared to IMRT.To investigate the limitations on the delivery of VMAT plans, a software emulator was produced to accurately simulate linac motion. The emulator was used to determine 'ideal' linac parameters for a range of VMAT plans. Leaf speed was found to be a limiting factor for the achievable plan complexity, along with the availability of continuous variable dose rate (CVDR). For a commercial CVDR system, experiments confirmed the improved delivery efficiency, and an improvement in dosimetric accuracy compared to the binned dose rate (BDR) system.An independent dose calculation methodology was developed for VMAT, such that accurate pre-treatment plan QC can be performed. It was found that the accuracy of a Monte Carlo simulation was improved when accounting for the effects of realistic linac motion. Finally, the impact of MV scatter on simultaneously-acquired cone beam CT images was investigated, and a scatter correction methodology was developed and validated.This thesis shows that VMAT can offer an alternative to static-field IMRT, provided that knowledge of the limitations of dynamic linac motion are accounted for within planning. Results suggest that modern linac designs (i.e. faster MLC speed, and a higher, continuously-variable dose rate) are required to achieve robust delivery of complex plans. The workflow benefits of VMAT can also be optimised through the use of independent dose calculations incorporating delivery characteristics, and through the use of image guidance from CBCT scans acquired during treatment.

Radiation therapy has been shown to increase local and regional control as well as overall survival with breast cancer, but the vast majority of patients develop acute skin reactions, which are in part related to microvascular changes. These reactions vary between different skin sites. The aim of this work is to determine the absorbed dose to the skin by measurements and investigate if there is a correlation between the absorbed dose at different areas of the breast and the local changes in microcirculation in the skin after breast cancer radiotherapy. The study includes characterisation of the Gafchromic EBT3 film and Epson Perfection V600 Photo scanner which are used for absorbed dose determination. The measurements were done both on an anthropomorphic female phantom and on a patient undergoing breastcancer radiotherapy. Twenty-one pieces of film (2x1 cm2) were placed on the surface ofthe breast (both for the phantom and patient) and irradiated with a prescribed dose to the target of 2.66 Gy with two opposed fields using 6 MV beam. It was observed that mainly 45-64 % of the prescribed dose was deposited at the surface, both for the phantom and patient. Using laser speckle contrast imaging and polarised light spectroscopy, the regional changes in mean blood perfusion and in mean red blood cell concentration (RBCC) at the end of the treatment with a total prescribed dose of 42.6 Gy, compared to baseline, were measured in both the treated and untreated breast of the same patient. Although marked increases in perfusion were seen in different areas of the treated breast, there was no signicant correlation between the changes in perfusion and the absorbed dose at these areas. However, a statistical correlation was found between the changes in RBCC and the absorbed skin dose at the same areas. To further elucidate the relation between the changes in skin microcirculation and the absorbed radiation dose during breast cancer radiotherapy, future studies using a larger number of patients are needed.

No description available.

Skin collimation in electron therapy ensures sharper penumbra and maximal protection to adjacent critical structures. It also provides a better clinical dose to the target and avoids recurrences at the periphery. The thickness of the electron skin collimation must be adequate for shielding purposes, not too thick to cause discomfort to the patient and be conformal to the skin. This study assessed the clinical potential of machined brass skin collimation with variable thickness. Brass transmission factors for 6, 9, and 12 MeV electron beams were measured and used to determine the skin collimation clinically acceptable thickness. Dosimetric performance of the variable thickness skin collimation was evaluated for 9 MeV electrons within a rectilinear water-equivalent phantom and a water-filled head phantom. Results showed the variable thickness skin collimation is dosimetrically equivalent to the uniform thickness collimation. Favorable dosimetric advantages for brass skin collimation for small electron fields were achieved. / Includes bibliography. / Thesis (PMS)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

No abstract available. / Dissertation (MSc)--University of Pretoria, 2010. / Medical Oncology / unrestricted

Indiana University-Purdue University Indianapolis (IUPUI) / Radiation Therapy has been one of the most common techniques to treat various types of cancers, in particular is Head and Neck Cancer (HNC) which accounts for three percent of all cancers in the United States. During the treatment procedure, the patient is immobilized using immobilization devices such as the full head face mask, bite blocks, stereotactic frame, etc. to get accurate location of tumor. The disadvantage of these devices is that they are very uncomfortable to the patient especially people suffering from Post-Traumatic Stress Disorder (PTSD) and claustrophobia who cannot wear any confined masked system such as the full head mask or bite block during the treatment procedure. To mitigate this problem, there has been a lot of research in modifying such immobilizing devices without neglecting the accurate location of tumor. To this end, the research presented in this thesis focuses on developing a mask less system with accurately locating the position of tumor using the technique of coordinate transformation at the same time fulfilling the three important characteristics: • Comfort • Accuracy • Low price Such a system is comfortable to the patient because no confining mask system is used and we choose minimal contact points on the patient for fixing the patient. Traditionally, such type of cancer treatment is carried out in two stages: Diagnosis stage, which identifies the location of the tumor and the external markers and the Treatment stage where the tumor is treated with immobilization device being common in both the stages. In the new system, the immobilization devices vary at the two stages. The head position is monitored by using pressure sensor assembly where spring and pressure sensor setup detects the amount and direction of head deviation. We also prepare a customized 3D printed nose bridge part for extra referencing in the treatment room. Also, it is important that we use material for our immobilization devices which does not contain any metal and MRI compatible. Once the patient lies down on the treatment couch and is immobilized using the immobilization devices, then tumor location is calculated using the theory of coordinate transformation and transformation matrix in the Diagnosis and Treatment Stage. To validate the system, simulation of immobilization devices used in the new design was carried out using ANSYS Workbench 15.0 and LS-Dyna software’s Explicit Dynamics method. The simulation for the head-fixing device showed a deflection of ±0.1974 mm with respect to machine isocenter with a load of 60 N, which is lower than the customer requirement of ±3 mm with respect to machine isocenter of head deviation. The material used for the external markers for patient positioning was selected to be polyetheretherketone (PEEK) which is a radiolucent and widely used MRI compatible material. The system also takes into consideration the effect of weight loss, which is one of the drawbacks of the current systems. Although still in the development stage, this mask less system holds to be the next new variety of immobilization devices that are comfortable to the patient and less expensive to be implemented in future cancer treatment practices.

This thesis describes a general platform for the synthesis of radiolabelled antibody recruiting small molecules (R-ARMs) for combination radio and immune recruitment therapies. The novel trifunctional ARM was synthesized and radiolabelled with beta (lutetium-177) and alpha (actinium-225) emitting radionuclides in high yield. Biodistribution of the lutetium-ARM revealed rapid renal clearance and minimal uptake in non-target tissues with all organs and tissues containing less than 0.3 %ID/g by 24 hours post-injection. Having determined the pharmacokinetic properties of the ligand, a biodistribution study was performed to determine the targeting potential of the platform. Through the use of a validated bone targeted bisphosphonate, uptake in the arm and leg bones was achieved. Flow cytometry studies successfully demonstrated ARM and antibody dependent immune cell recruitment. Based on the promising results of the ARM in vitro and in vivo, the next step was to perform therapy studies. In order to validate the novel R-ARM, an intratumoral (i.t.) strategy was developed through the preparation of a TCO-bovine serum albumin (BSA) derivative. This new chemical entity was used in both an aggregated and non-aggregated form to retain the R-ARM in the tumour after i.t. administration. Biodistribution showed high retention of the aggregated and non-aggregated BSA out to 120 hours with 167 ± 94 and 81 ± 32 %ID/g respectively remaining in the tumour. An autoradiography study revealed the after i.t. administration the aggregated material was localized in specific regions within the tumour compared to the non-aggregated material which diffused throughout. The aggregated material was used in a single and multi-dosing radiotherapy study in which the latter induced a statistically significant survival advantage compared to the control. One additional multi-dosing study was performed with the non- aggregated material which resulted in the largest survival advantage to date. Intratumoral administration of TCO-BSA linked to the trifunctional tetrazine showed promising radiotherapy results and future work on dose optimization with lutetium and actinium is required prior to the combination R-ARM therapy. In parallel, the efficacy of the unlabelled ARM linked to TCO-BSA was interrogated in preclinical models. The compound was administered i.t. three times per week in a breast cancer tumour model, and response to therapy monitored. The immunized group showed no survival advantage compared to the control group comprised of naïve animals. Biodistribution studies were performed to determine if TCO-BSA was accessible to the bloodstream following i.t. administration in both the aggregated and non-aggregated forms. Saline, aggregated or non-aggregated TCO-BSA were administered i.t. followed by the R-ARM. The results showed very low uptake in the tumour for all three groups, with minimal change in distribution from that of the native R-ARM. This suggests that after i.t. administration, the TCO-BSA was not available to molecules in the bloodstream or the concentration was insufficient to promote in vivo coupling. Further work on this component of the platform is needed before further ARM studies are performed. / Thesis / Doctor of Science (PhD)

A simple method to verify the total treatment time generated by the treatment planning system (TPS) when the CONTURA MLB or the SAVI applicator are used for APBI treatments has been developed. The method compares the time generated by the TPS to a predicted time, calculated by inserting parameters obtained from the TPS in equations generated in this Thesis. The equations were generated by linearly fitting data from clinical cases that had been treated using the Contura MLB or the SAVI applicator at the Lynn Cancer Institute of the Boca Raton Regional Hospital. The parameters used were the PTV coverage, Air Kerma Strength, Balloon Volume (Contura data fit) and Evaluation PTV (SAVI data fit). As an outcome of this research, it is recommended that the plan should be reevaluated when the percent difference between the generated and the predicted times exceeds 5% for the Contura MLB, or 10% for the SAVI. / by Andreas Kyriacou. / Thesis (M.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

by Ho Wai-chun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Abstract also in Chinese. / Title / Dedication / Abstract --- p.i / Table of Contents --- p.iv / Glossary of abbreviation used in the thesis --- p.vi / List of figures --- p.viii / List of tables --- p.xvii / Acknowledgement --- p.xix / Statement of Originality --- p.xx / Chapter Chapter 1 ...... --- Introduction --- p.14 / Chapter Chapter 2...... --- Basic Principle / Chapter 2.1 --- The liver - a vital organ --- p.2-1 / Chapter 2.2 --- Blood supply to the liver --- p.2-7 / Chapter 2.3 --- Normal arterial anatomy of the coeliac axis --- p.2-11 / Chapter 2.4 --- Common anomalies of the coeliac axis --- p.2-17 / Chapter 2.5 --- Previous classification of coeliac anomaies --- p.2-24 / Chapter 2.6 --- Knowledge of arterial anomaly in relation to surgery --- p.2-31 / Chapter 2.7 --- Trans-catheter treatment of hepatocellular carcinoma --- p.2-33 / Chapter 2.8 --- Prevalence of hepatocellular carcinoma in H.K Chinese --- p.2-42 / Chapter 2.9 --- Management of hepatocellular carcinoma in Hong Kong --- p.2-43 / Chapter Chapter 3...... --- Definitions --- p.3-1 / Chapter Chapter 4...... --- Objectives of the study --- p.4-1 / Chapter Chapter 5...... --- "Materials, methods and subjects" / Chapter 5.1 --- Materials --- p.5-1 / Chapter 5.2 --- Methods --- p.5-3 / Chapter 5.3 --- Subjects --- p.5-10 / Chapter Chapter 6...... --- Results / Chapter 6.1 --- Coeliac axis --- p.6-5 / Chapter 6.2 --- Common hepatic artery --- p.6-9 / Chapter 6.3 --- Proper hepatic artery --- p.6-11 / Chapter 6.4 --- Right hepatic artery --- p.6-12 / Chapter 6.5 --- Middle hepatic artery --- p.6-20 / Chapter 6.6 --- Left hepatic artery --- p.6-28 / Chapter 6.7 --- Gastroduodenal artery --- p.6-33 / Chapter 6.8 --- Right gastric artery --- p.6-37 / Chapter 6.9 --- Left gastric artery --- p.5-45 / Chapter 6.10 --- Splenic artery --- p.6-49 / Chapter 6.11 --- Summary of results --- p.6-51 / Chapter Chapter 7...... --- Discussion / Chapter 7.1 --- Introduction --- p.74 / Chapter 7.2 --- Selective Internal Radiation --- p.7-3 / Chapter 7.3 --- Coeliac axis --- p.7-10 / Chapter 7.4 --- Common hepatic & proper hepatic artery --- p.7-7 / Chapter 7.5 --- Right hepatic artery --- p.7-14 / Chapter 7.6 --- Middle hepatic artery --- p.7-18 / Chapter 7.7 --- Left hepatic artery --- p.7-25 / Chapter 7.8 --- Gastroduodenal artery --- p.7-30 / Chapter 7.9 --- Right gastric artery --- p.7-35 / Chapter 7.10 --- Left gastric artery --- p.7-43 / Chapter 7.11 --- Splenic artery --- p.7-45 / Chapter 7.12 --- Comparison with the golden classics --- p.7-47 / Chapter 7.13 --- Comparison of subjects with HCC & without HCC --- p.7-50 / Chapter 7.14 --- Comparison of the male group and the female group --- p.7-51 / Chapter Chapter 8...... --- Conclusions / References --- p.B-1 / Bibliography --- p.B-1 / Appendix I Schematic diagram of histological anatomy of the liver --- p.A-l / Appendix II Embryology --- p.A-2 / "Appendix III Percentages of occurrence of the different types of coeliac axis, by Michels' study" --- p.A-3 / "Appendix IV Percentages of occurrence of the different types of the hepatic arterial blood supply, by Michels' study" --- p.A-4 / Appendix V No. of deaths from malignant liver cancer in Hong Kong froml984 to1993 --- p.A-5 / Appendix VI Flow chart for HCC management in PWH of Hong Kong --- p.A-6 / Appendix VII Comparison with Michels' study --- p.A-7 / Appendix VIII Comparison of the group with HCC and the group without HCC --- p.A-8 / Appendix IX Comparison of the male and female group --- p.A-9