17 research outputs found

    IGRT and motion management during lung SBRT delivery.

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    Patient motion can cause misalignment of the tumour and toxicities to the healthy lung tissue during lung stereotactic body radiation therapy (SBRT). Any deviations from the reference setup can miss the target and have acute toxic effects on the patient with consequences onto its quality of life and survival outcomes. Correction for motion, either immediately prior to treatment or intra-treatment, can be realized with image-guided radiation therapy (IGRT) and motion management devices. The use of these techniques has demonstrated the feasibility of integrating complex technology with clinical linear accelerator to provide a higher standard of care for the patients and increase their quality of life

    Real-time intrafraction motion monitoring in external beam radiotherapy

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    © 2019 Institute of Physics and Engineering in Medicine. Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to 'see what we treat, as we treat' and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-time treatment adaptation. Additional equipment, such as stereoscopic kilovoltage (kV) imaging, ultrasound transducers and electromagnetic transponders, has been developed for intrafraction motion monitoring on conventional linacs. Magnetic resonance imaging (MRI) has been integrated with cobalt treatment units and more recently with linacs. In addition to hardware innovation, software development has played a substantial role in the development of motion monitoring methods based on respiratory motion surrogates and planar kV or Megavoltage (MV) imaging that is available on standard equipped linacs. In this paper, we review and compare the different intrafraction motion monitoring methods proposed in the literature and demonstrated in real-time on clinical data as well as their possible future developments. We then discuss general considerations on validation and quality assurance for clinical implementation. Besides photon RT, particle therapy is increasingly used to treat moving targets. However, transferring motion monitoring technologies from linacs to particle beam lines presents substantial challenges. Lessons learned from the implementation of real-time intrafraction monitoring for photon RT will be used as a basis to discuss the implementation of these methods for particle RT

    Non-invasive lung tumor motion estimation and mitigation in real-time during radiation therapy

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    Die interfraktionelle Bewegung von Lungentumoren während der Applikation von externer Strahlentherapie kann ein limitierender Faktor für den ehandlungserfolg sein. Tumorbewegung kann sowohl eine Unterdosierung des Zielvolumens als auch eine schwerwiegende Überdosierung des umliegenden gesunden Gewebes zur Folge haben. Die vorliegende Arbeit besteht aus drei Teilen. Im ersten Teil wird eine Methode zur bildgestützten Bewegungsabschätzung von Lungentumoren in Echtzeit vorgestellt. Vorteile des Verfahrens sind die Unabhängigkeit von implantierten Markern (Pneumothorax Risiko) und die Vermeidung von zusätzlicher Bildgebungsstahlendosis, da das Verfahren mit dem Therapiestrahl akquirierte fluoroskopische Bildsequenzen nutzt. Die Validierung erfolgte sowohl anhand von Bildern, die mit einem beweglichen Thoraxphantom aufgenommen wurden, als auch anhand von Bildern, die während einer Reihe von Lungenstereotaxiebehandlungen aufgenommen wurden. Der Fehler (rmse) wurde für den Phantomdatensatz zu < 1mm und für den klinischen Datensatz zu (2.1 ± 1.7)mm bestimmt. Der zweite Teil dieser Arbeit befasst sich mit der Implementierung und Charakterisierung eines dynamischen, adaptiven Bestralungsystems, das durch das Nachführen des Therapiestrahls in Echtzeit Bewegungen des Zielvolumens kompensieren kann. Das System nutzt eine computergestützte, dynamisch ansteuerbare Strahlungsapertur (MLC), welche mit der Position des Zielvolumens aus dem ersten Teil in Echtzeit angesteuert wird. Die Latenzzeit wurde gemessen ( 250 ms) und durch einen linearen Vorhersagealgorithmus kompensiert. Das System wurde mit einem mit Lungentumortrajektorien programmierten dynamischen Thoraxphantom getestet. Der Fehler konnte von 2.4mm bis 3.5mm auf unter 1mm reduziert werden. Im dritten Teil dieser Arbeit wird der Algorithmus vom ersten Teil eingesetzt, um nach jeder Fraktion einer Lungenstereotaxiebehandlung die applizierte Dosis zu berechnen. Das Konzept wurde mit einem dynamischen Thoraxphantom validiert. Mit der retrospektiven Bildanalyse einer Lungenstereotaxiebehandlung konnte gezeigt werden, daß sich fraktionelle Unterdosierungen des Zielvolumens, etwa durch nicht optimale Patientenpositionierung, mit dieser Methode in Form eines Dosis-Volumen Histogramms (DVH) quantifizieren lassen

    マーカーレス腫瘍位置決めを目的とした深層学習に基づく患者固有標的輪郭予測モデルの開発

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    京都大学新制・課程博士博士(人間健康科学)甲第24542号人健博第113号新制||人健||8(附属図書館)京都大学大学院医学研究科人間健康科学系専攻(主査)教授 中尾 恵, 教授 杉本 直三, 教授 黒田 知宏学位規則第4条第1項該当Doctor of Human Health SciencesKyoto UniversityDFA

    The impact of technology on the changing practice of lung SBRT

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    Stereotactic body radiotherapy (SBRT) for lung tumours has been gaining wide acceptance in lung cancer. Here, we review the technological evolution of SBRT delivery in lung cancer, from the first treatments using the stereotactic body frame in the 1990's to modern developments in image guidance and motion management. Finally, we discuss the impact of current technological approaches on the requirements for quality assurance as well as future technological developments

    The optimization of image guided radiotherapy in lung cancer

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    The hypothesis of this work was whether IGRT could be safely implemented for clinical use in a busy oncology centre. I aimed to study a number of questions that remain unresolved in the current literature regarding safe and optimised implementation of IGRT techniques. The first study undertaken was the calculation of a local set up margin using two widely recognised margin recipes. This involved the assessment and analysis of multiple images belonging to 100 patients. This allowed progression onto the next project which was assessment of the optimal safe method of delineation of 4DCT. The most efficient method was compared to gold standard. At this point a different aspect of the radiation process was assessed, namely verification. A feasibility study of a simple, efficient form of imaging for use in review of a particular error was performed. This also involved the use of a novel tool which required independent assessment. This progressed into a further study of a larger number of patients using this tool and the images assessed previously to verify a novel form of radiation delivery. Lastly a planning study was performed to quantify the clinical benefit of another delivery system. This involved the delineation and planning of a large number of radical lung patients with standard radiation treatment and the novel radiation treatment and an assessment of the potential clinical benefits. The work presented in this thesis has answered some specific questions in IGRT in lung cancer, and contributed both locally and in the wider lung cancer community to increasing the use of IGRT in lung cancer

    New Methods for Motion Management During Radiation Therapy

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    In this thesis, a number of new image-based techniques for the management of intrafractional motion during radiation therapy are presented. Intra-fractional motion describes all kinds of anatomy changes - most prominently respiration - that occur during a single treatment session. Spatially confining the radiation dose to the tumour tissue and thus sparing surrounding healthy tissue is assumed to be crucial for a successful treatment with limited side effects. Unfortunately, the delivery of dose distributions that are sharply confined to the tumour is greatly complicated by patient motion. If not accounted for, this motion will lead to a smearing out of the original dose distribution and will facilitate the redistribution of dose from tumour to healthy tissue. Possible technical solutions for this issue include the interruption of the radiation delivery if the tumour leaves a predefined spatial ‘window’, and the reshaping of the treatment field ‘on-the-fly’ to follow the tumour. Regardless of which delivery techniques is selected, the patient motion needs to be reliably detected in real-time to allow for an adaptation of the treatment delivery. First, we present experimental results for a novel x-ray imaging system that is attached to the treatment delivery device and enables us to continuously monitor the tumour motion during treatment delivery with sub-mm accuracy, a latency better than 90 ms, and a 7 Hz update rate. Second, we present a Monte Carlo simulation for an improved amorphous-silicon flat-panel detector that reduced treatment beam filtration by 60% and long-range MV-scatter by 80%. We conclude this thesis by presenting results of an experimental demonstration of a novel dose-saving actively-triggered 4d cone-beam computed tomography device

    Optimizing Respiratory Gated Intensity Modulated Radiation Therapy Planning and Delivery of Early-Stage Non-Small Cell Lung Cancer

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    Stereotactic ablative body radiotherapy (SABR) is the standard of care for inoperable early-stage non-small cell lung cancer (NSCLC) patients. However, thoracic tumours are susceptible to respiratory motion and, if unaccounted for, can potentially lead to dosimetric uncertainties. Respiratory gating is one method that limits treatment delivery to portions of the respiratory cycle, but when combined with intensity-modulated radiotherapy (IMRT), requires rigorous verification. The goal of this thesis is to optimize respiratory gated IMRT treatment planning and develop image-guided strategies to verify the dose delivery for future early-stage NSCLC patients. Retrospective treatment plans were generated for various IMRT delivery techniques, including fixed-beam, volumetric modulated arc therapy (VMAT), and helical tomotherapy. VMAT was determined the best technique for optimizing dose conformity and efficiency. A second treatment planning study that considered patients exhibiting significant tumour motion was conducted. Respiratory ungated and gated VMAT plans were compared. Significant decreases in V20Gy and V50%, predictors for radiation pneumonitis and irreversible fibrosis, respectively, were observed. The predominant uncertainty of respiratory gating lies in the ability of an external surrogate marker to accurately predict internal target motion. Intrafraction triggered kV imaging was validated in a programmable motion phantom study as a method to determine how correlated the internal and external motion are during ungated and gated VMAT deliveries and to identify potential phase shifts between the motions. KV projections acquired during gated VMAT delivery were used to reconstruct gated cone-beam CT (CBCT), providing 3D tumour position verification. Image quality and target detectability, in the presence of MV scatter from the treatment beam to the kV detector, was evaluated with various imaging parameters and under real-patient breathing motion conditions. No significant difference in image quality was observed for the CBCT acquisitions with or without the presence of MV scatter. This thesis explores the benefits of combining respiratory gating with IMRT/VMAT for the treatment of early stage NSCLC with SABR, and evaluates advanced on-board imaging capabilities to develop dose delivery verification protocols. The results of this thesis will provide the tools necessary to confidently implement a respiratory gated radiotherapy program aimed at improving the therapeutic ratio for early-stage NSCLC

    On the investigation of a novel x-ray imaging techniques in radiation oncology

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    Radiation therapy is indicated for nearly 50% of cancer patients in Australia. Radiation therapy requires accurate delivery of ionising radiation to the neoplastic tissue and pre-treatment in situ x-ray imaging plays an important role in meeting treatment accuracy requirements. Four dimensional cone-beam computed tomography (4D CBCT) is one such pre-treatment imaging technique that can help to visualise tumour target motion due to breathing at the time of radiation treatment delivery. Measuring and characterising the target motion can help to ensure highly accurate therapeutic x-ray beam delivery. In this thesis, a novel pre-treatment x-ray imaging technique, called Respiratory Triggered 4D cone-beam Computed Tomography (RT 4D CBCT), is conceived and investigated. Specifically, the aim of this work is to progress the 4D CBCT imaging technology by investigating the use of a patient’s breathing signal to improve and optimise the use of imaging radiation in 4D CBCT to facilitate the accurate delivery of radiation therapy. These investigations are presented in three main studies: 1. Introduction to the concept of respiratory triggered four dimensional conebeam computed tomography. 2. A simulation study exploring the behaviour of RT 4D CBCT using patientmeasured respiratory data. 3. The experimental realisation of RT 4D CBCT working in a real-time acquisitions setting. The major finding from this work is that RT 4D CBCT can provide target motion information with a 50% reduction in the x-ray imaging dose applied to the patient
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