Made available in DSpace on 2014-10-09T12:54:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:45Z (GMT). No. of bitstreams: 0 / A avaliação do desempenho dos detectores termoluminescentes de CaSO4:Dy, produzidos pelo IPEN, tem como objetivo apresentar uma alternativa aos dosímetros de LiF:Mg,Ti comerciais (TLD-100), amplamente empregados em radioterapia, na dosimetria de feixes clínicos de elétrons. Os dois tipos de detectores termoluminescentes foram caracterizados, com a utilização de objetos simuladores de PMMA, água sólida do tipo RMI-457 e água, em campos de radiação de elétrons de 4, 6, 9, 12 e 16 MeV de energias nominais, nos quais as curvas de dose-resposta foram obtidas e as doses superficial e profunda foram determinadas. A dependência da resposta termoluminescente com a energia nominal dos elétrons e com o objeto simulador empregado foram estudadas. O CaSO4:Dy apresentou o mesmo comportamento do LiF:Mg,Ti; de maneira que sua aplicação como uma alternativa às pastilhas TLD-100 na dosimetria de feixes de elétrons em radioterapia é viável e apresenta a sensibilidade à radiação de elétrons significativamente mais alta como principal vantagem. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Despite that most vestibular schwannomas are successfully treated with radiotherapy, current follow-up protocols entail years of serial magnetic resonance imaging (MRI) scans to ensure cessation of growth. This pilot study sought to identify early predictors of radiation treatment response using a non-invasive multi-modality imaging approach. We hypothesized that by combining information acquired from dynamic contrast-enhanced MRI (DCE-MRI), diffusion tensor imaging (DTI), and L-¹¹C-methionine positron emission tomography (MET-PET) treatment response could be identified sooner than the current several year waiting period. This thesis presents the baseline MRI and MET-PET results of the pilot study acquired to-date with follow-up data to be acquired in the next six months. Baseline results suggest that DTI and DCE-MRI yield information that may be useful in identifying the response of vestibular schwannomas to radiotherapy. In particular, vestibular schwannomas display elevated mean diffusion coefficients relative to the contra-lateral cerebellum. Also, the novel use of arterial input functions derived from the anterior inferior cerebellar arteries has led to the successful implementation of DCE-MRI pharmaco-kinetic models which may be used to quantitatively monitor tumor response to radiotherapy. Furthermore, MET-PET has shown promise as a tool for evaluating response as all tumors exhibited enhancement under this modality as compared to the contra-lateral side of the brain. Single-voxel spectroscopy with 3T MRI has proven to be a poor technique with which to examine vestibular schwannomas since only two of eight spectra were acquired successfully. All of the techniques that have shown promise as investigatory tools of tumor response can potentially be implemented clinically in the near future. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In proton therapy systems with pencil-beam scanning, output of Halo effect is not necessarily included in Treatment Planning System (TPS). Halo effect (low-intensity tail) can significantly affect a patient’s dose distribution. The output of this dose depends on the field size being irradiated. Although much research has been made to investigate such relation to the field size, the number of reports on dose calculations including the halo effect is small. In this work we have investigated the Halo effect, including field size factor, target depth factor, and air gaps with a range shifter for a Varian ProBeam. Dose calculations created on the Eclipse Treatment Planning System (vs15.6 TPS) are compared with plane-parallel ionization chambers (PTW Octavius 1500) measurements using PCS and AcurosPT MC model in different isocenters: 5cm, 10cm, and 20cm. We find that in AcurosPT algorithm deviations range between -7.53% (for 2cm field in 25cm air gap with range shifter) up to +7.40% (for 20cm field in 15cm air gap with range shifter). Whereas, in PCS algorithm the deviations are -2.07% (for 20x20cm field in open conditions) to -6.29% (for 20x20cm field in 25cm air gap with range shifter). / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

Physical cones equipped on GammaKnife, Cyberknife, and C-arm linacs have been the standard practice in Stereotactic Ablative Radiotherapy (SART) for small intracranial lesions, such as treating trigeminal or glossopharyngeal neuralgia targets. The advancement of high-definition multi-leaf collimators (HDMLC), treatment planning systems, and small field dosimetry now allows for treatment without the need for an auxiliary mounted physical cone. This treatment type uses the “virtual cone”, a permanent high-definition MLC, arrangement to deliver “very small fields” with comparable spherical dose distributions to physical cones. The virtual cone therapy, on a Varian Edge™ linac using multiple non-coplanar arcs with static HDMLCs, is a comparable technique that can be used to treat small intracranial neuralgia or other small lesions. In this investigation, two flattening filter free (FFF) photon beams, 6MV FFF and 10MV FFF, were tested for optimal delivery and safety conditions for treating intracranial lesions. The virtual cone method on a Varian Edge™ Linear accelerator using rapid arc stereotactic radiosurgery was used to treat cranial neuralgia for chronic pain for six patients. Absolute dose, relative dose measurements, and monitor units were the main characteristics that were examined to decide which energy was the best for treatment. Source-to-axis distances (SAD) of 100cm measurements were taken at depths of 10cm and 5cm, respectively. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

The aim of this thesis was to develop and evaluate albumin-based conjugates for their use in radiotherapy and antibody-recruiting therapy which may then be combined to enhance therapeutic efficacy of each monotherapy. The approach taken in order to achieve high tumour uptake of the conjugates and minimize doses to healthy tissues involved the intratumoural administration of therapeutic compounds; a technique which has gained popularity in recent years for the treatment of solid tumours. Despite the promise this method of administration holds, it is often limited by the fast clearance of injected compounds from the tumour. Using albumin-based conjugates allows for the exploitation of the enhanced permeation and retention (EPR) effect which aids in the retention of the compound at the site of interest for longer periods of time, thus allowing the opportunity for enhanced therapeutic efficacy. Bovine serum albumin conjugated with DOTA chelators was first synthesized and found to possess 3.9 ± 0.4 chelates per BSA molecule. Radiolabelling of the compound with lutetium- 177 produced the desired product in radiochemical yields of 74 ±2 % with a radiochemical purity >99%. The stability of the compound was evaluated by monitoring the radiochemical purity over 7 days which was found to be >95% pure over the entirety of the testing period, indicating a stable product. The intratumoural administration of [177Lu]Lu-DOTA-BSA in a triple negative breast cancer (TNBC) tumour model revealed significant tumour retention of 52 ± 12 %ID/g and 35 ± 6 %ID/g at 24 h and 72 h post-injection, respectively, while autoradiography displayed a heterogenous dispersion of the compound throughout the tumour. A multidosing therapy study in which animals received two doses of either 4.44, 5.92, or 7.40 MBq of [177Lu]Lu-DOTA-BSA showed promise, with a strong trend observed between the administration of higher doses and a prolonged lifespan. Histological analysis of tumours excised 7 days post-treatment revealed signs iv of necrosis and apoptosis in tumours treated with 7.40 MBq [177Lu]Lu-DOTA-BSA. These preliminary results prove to be a promising approach for use in combination therapy and may be further optimized to enhance its efficacy as a monotherapy. Next, the in vivo evaluation of DNP-BSA was carried out to assess using an intratumourally administered, albumin-based platform for antibody-recruiting in a triple negative breast cancer model. A preliminary antibody-recruiting study administering 35 nmol DNP-BSA three times per week unfortunately did not induce slowed tumour growth nor did it have an impact on lifespan. Treated mice were also unable to tolerate repeated doses of the antigen which indicated too high of a concentration and/or dosing frequency was used. A tolerability study was then carried out in order to determine a treatment schedule which did not lead to adverse effects. Mice treated once per week with low (9 nmol) to moderate (17 nmol) doses of DNP-BSA did not display toxic effects but unfortunately did not exhibit a therapeutic effect nor any indication that an adaptive immune response was achieved. These results suggest that further optimization is required prior to use in combination therapy and moderate doses (17 nmol) DNP should be used to investigate a treatment schedule which is able to induce antibody recruitment. / Thesis / Master of Science (MSc)

No description available.

A dissertation submitted in accordance with the requirements for the degree of Master of Science in the Faculty of Science at theUniversity of Witwatersrand, Johannesburg, 2012. / AIM: This studied aimed at analysing the set-up error (margin) of head and neck cases, treated in a vacuum formed acrylic shell with an in-house immobilisation system. METHODS AND MATERIALS: Two population groups were studied, namely virtual simulated and intensity modulated radiotherapy (IMRT) cases. All cases were treated with the in-house immobilization system, which located centrally, but not longitudinally, to the treatment couch. Verification of the couch position, other than the isocentric angle, was not activated. The virtual simulated cases consisted of two lateral fields with a matched anterior neck field. The borders of these fields were chosen by the radiation oncologist. The IMRT cases were planned by a medical physicist and consisted of 6-9 fields of 3-4 intensity levels each. Digitally reconstructed radiographs (DRRs) of the 2 lateral fields and the anterior neck field for the virtual simulated cases, and the 2 lateral and anterior composite fields at the same isocentre for the IMRT cases, were printed and represented the ideal patient position. On the first day of treatment, megavoltage verification films were taken of the treated or positioning fields respectively. These verification films were compared to the DRRs and approved by a radiation oncologist. The absolute bed position in the vertical (Y), lateral (X) and longitudinal (Z) directions at the time of film approval, was used as the reference or ideal position. The absolute readings of the couch position that were captured daily over the course of treatment were then compared to the initial couch position to give an indication of the systematic and random errors. One linear accelerator was used in this study and weekly mechanical quality control (QC) was performed on it. RESULTS: The total number of daily fractions (F) studied in this thesis was 5644 and 600 for virtual simulated and IMRT cases respectively. The systematic error of this population was 4.7 and 4.4 mm for the virtual simulated and IMRT cases respectively. This compares well with published results using a similar immobilisation system. The random error of this population was 7 mm and 6.1 mm for the virtual simulated and IMRT cases respectively. This is three times larger than the results reported in the literature (using a similar immobilization device). CONCLUSION: Offline monitoring of couch position provides insight into setup margins and this can contribute to realistic institutional planning target volumes. Better results were obtained in the IMRT cases and this could be due to the requirement for weekly verification imaging. Lack of radiation therapist vigilance and insufficient training were most likely responsible for the individual cases with systematic variations of larger than 3 cm. The data confirm that the immobilisation system can be located to a fixed position on the tabletop; this will allow online verification of absolute bed position for treatment and further decrease the chance of incorrect setup.

Multi-ion radiotherapy has been suggested as a new way to treat cancer, combining the radiological advantages of lighter and heavier ions in a single treatment to improve plan robustness and increase LETd in the target. To succeed, multi-ion radiotherapy requires a treatment planning system capable of computing dose for and optimising multi-ion treatment plans. In this project, prototypical multi-ion radiotherapy treatment planning support has been implemented in the RayStation treatment planning system. The existing dose engine for helium and carbon ion beams has been extended to support protons, oxygen and neon ions, and support has been added for dose computation and plan optimisation for any combination of these ion species. The implemented functionality has been evaluated in two phantom cases and a patient case. Multi-ion treatment plans have been shown to outperform carbon ion treatment plans in terms of simultaneously providing plan robustness, uniform RBE-weighted dose and high LETd. In the patient case, the multi-ion plan displayed significant improvements in the ability to "paint" high LETd in the target. Clinical studies are required to determine to what extent this new modality increases treatment quality in practice.

published_or_final_version / Public Health / Master / Master of Public Health

No description available.