157 research outputs found
Use of radiobiological modeling in treatment plan evaluation and optimization of prostate cancer radiotherapy
No full textThere are many tools available that are used to evaluate a radiotherapy treatment plan, such as isodose distribution charts, dose volume histograms (DVH), maximum, minimum and mean doses of the dose distributions as well as DVH point dose constraints. All the already mentioned evaluation tools are dosimetric only without taking into account the radiobiological characteristics of tumors or OARs. It has been demonstrated that although competing treatment plans might have similar mean, maximum or minimum doses they may have significantly different clinical outcomes (Mavroidis et al. 2001). For performing a more complete treatment plan evaluation and comparison the complication-free tumor control probability (P+) and the biologically effective uniform dose (D ) have been proposed (Källman et al. 1992a, Mavroidis et al. 2000). The D concept denotes that any two dose distributions within a target or OAR are equivalent if they produce the same probability for tumor control or normal tissue complication, respectively (Mavroidis et al. 2001)..
Determination and use of radiobiological response parameters in radiation therapy optimization
No full textOptimization of radiation therapy is critically dependent on the use of patient related information. For this reason, radiobiological models describing the dependence of tumour and normal tissue responses on the irradiated volume and the dose-time-fractionation schedule should be introduced. In addition, the heterogeneity of the delivered dose distribution and tumour or normal tissue sensitivity variations have to be taken into account clinically. In the present study, a treatment optimization procedure is used that considers the shape and the structure of the target tissues and healthy organs at risk, their relative position and their dose-response relations for the individual patient.Mathematical models largely based on the Poisson statistics and the linear-quadratic model of cell kill, have been used to quantify the radiobiological response of normal human tissues and tumours to radiation therapy. The presented models predict a decreasing probability of achieving complication free tumour control with increasing tumour size and increasing volume of normal tissues irradiated. The radiobiological parameters D50, gamma, sigma and Vref of the Poisson and relative seriality models have been estimated for certain normal tissues and targets. The process for determining these dose-response relations was based on clinical materials where the treatment information and follow-up results of the individual patient were available. The statistical methods used, estimated and verified the parameters and their uncertainties. The clinical range of variability of the dose-response relations is important for their correct use in the clinical routine.The clinical use of the derived dose-response relations is demonstrated using radiobiological parameters for different tumours and normal tissues that were also calculated based on data clinical trials. A biological evaluation procedure is introduced and applied on clinical cases. This procedure uses the biological models and dose-response data of the involved organs and optimizes the dose level of the treatment technique under study. This is done by evaluating the plan using the P+, objective, which estimates the probability to achieve tumour cure without having severe complications to the healthy tissues. The clinical value of biologically based treatment planning was compared with alternative physical criteria (e.g. tolerance doses) and with the judgment of personnel on particular clinical cases.It is demonstrated that the radiobiological objective functions allow a much higher conformity and a more clinically relevant scoring of the treatment outcome. The probability of achieving tumour control without fatal complications in normal tissues is increased and the dose delivery optimized. Recent developments can reduce or even eliminate the need for intracavitary treatment by delivering more conformal dose distributions using intensity modulated external dose delivery. In these cases the reliability of the patient setup becomes critical for the effectiveness of the treatment. It is realized that accurate information concerning the response of different organs to fractionated intensity modulated radiation therapy is the key to true optimization of the delivered dose distribution.List of scientific papersI. Mavroidis P, Laurell G, Kraepelien T, Fernberg JO, Lind BK, Brahme A (2001). "Dose response parameters for esophageal stricture from head & neck radiotherapy." Int J Radiat Oncol Biol Phys (Submitted)II. Mavroidis P, Theodorou K, Lefkopoulos D, Nataf F, Karlsson B, Lax I, Kappas C, Lind BK, Brahme A (2001). "Prediction of AVM obliteration after stereotactic radiotherapy using radiobiological modelling." Radiother Oncol (Submitted)III. Mavroidis P, Axelsson S, Hyodynmaa S, Rajala MA, Lind BK, Brahme A (2001). "Positioning uncertainty and breathing effects on dose delivery and radiation pneumonitis prediction in breast cancer." Acta Oncol (Submitted)IV. Mavroidis P, Kappas C, Lind BK (1997). "A computer program for evaluating the probability of complication-free tumor control incorporated in a commercial treatment planning system." J Balcan Union Oncol 3: 257-64V. Lind BK, Mavroidis P, Hyodynmaa S, Kappas C (1999). "Optimization of the dose level for a given treatment plan to maximize the complication-free tumor cure" Acta Oncol 38(6): 787-98 https://pubmed.ncbi.nlm.nih.gov/10522770VI. Mavroidis P, Lind BK, Van Dijk J, Koedooder K, De Neve W, De Wagter C, Planskoy B, Rosenwald JC, Proimos B, Kappas C, Claudia D, Benassi M, Chierego G, Brahme A. (2000). "Comparison of conformal radiation therapy techniques within the dynamic radiotherapy project Dynarad. " Phys Med Biol 45(9): 2459-81 https://pubmed.ncbi.nlm.nih.gov/11008949VII. Mavroidis P, Lind BK, Brahme A (2001). "Biologically effective uniform dose (D) for specification, report and comparison of dose response relations and treatment plans. " Phys Med Biol 46(10): 2607-30 https://pubmed.ncbi.nlm.nih.gov/11686278</p
Francis Group, Boca Raton, FL, 2019. Hardcover: 252pp. Price: $224.00. ISBN: 9780367255152.
No full textDetermination and use of radiobiological response parameters in radiation therapy optimization (in English)
No full textEstimation of the Delivered Dose in Prostate Cancer Patients Treated with IMRT/VMAT Using Deformable Image Registration: Dosimetric and Clinical Considerations
No full textDevelopment in supporting technologies for external beam radiation therapy such as adoption of 3D-computed tomography (CT) imaging, multileaf collimators, and advanced planning software has allowed for the clinical implementation of intensity-modulated radiotherapy and volumetric-modulated arc therapy for the treatment of prostate cancer. Adaptive radiotherapy utilizes fractional image guidance to improve conformity between the dose delivery projected from the planning CT and the actually delivered dose throughout treatment. Due to the steep fall-off of the dose distribution around the target, which is created to spare the organs-at-risk, a robust verification of dose delivery and quality assurance of the inverse treatment planning process is required. This demand for accurate delineation highlights the need for consideration of inter-fractional changes in organ position, alignment, and deformation. During treatment of prostate cancer, the degree of filling of the bladder and rectum can cause dramatic changes to size and shape of these organs. The greatest challenge in reducing uncertainty in the delivery of radiation in the future remains correction for organ deformation throughout treatment. The potential relationship of deviation in accumulated dose from the planned dose with patient reported outcome and normal tissue complication probability has not been quantified. This dissertation examines the effects of anatomical deformations of the bladder and rectum on the accumulated dose and evaluates potential correlation of dose accumulated in the bladder and rectum throughout treatment with patient reported outcome data. Estimations of accumulated dose incorporated fractional image guidance through one of multiple deformable image registration algorithms, validated against physician delineated contours, for comparison to the planning CT dose. Correlation of the deviations estimated during treatment via accumulated dose with factors associated with disease-specific patient reported outcome informs an understanding of the impact inter-fractional dose variation has on patient reported outcome.Doctor of Philosoph
Derivation of dose-response parameters for xerostomia in head and neck tumour patients treated with radiation therapy
No full textDissertação de Mestrado Integrado em Engenharia Biomédica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.Objetivo: Derivação de parâmetros dose-resposta para efeitos secundário da
radioterapia, xerostomia, em doentes com tumores de cabeça e pescoço tratados no
IPOCFG.
Métodos e Materiais: Um total de 302 pacientes com tumores de cabeça e pescoço,
tratados com Radioterapia de Intensidade Modulada (IMRT), foram incluídos neste
estudo. O efeito secundário estudado foi xerostomia aguda e tardia, avaliadas segundo
as recomendações do Radiation Therapy Oncology Group e da European
Organization for Research and Treatment of Cancer (RTOG/EORTC). Foram
derivadas curvas de dose-resposta para o modelo Relative Seriality para os períodos
de follow-up: 7 semanas, 3, 7, 12, 18 e 24 meses. A incidência de complicações foi
determinada através da divisão dos doentes em: Grau 0 (G0, sem complicações) vs.
Grau 2 (G2, severidade moderada) e G0 vs. G1+G2 (suave+moderada). Para
estabelecer as relações de dose-efeito, foi considerada a dose fornecida na parótida
contra-lateral, parótida ipsilateral, soma das parótidas e glândulas salivares. A
qualidade do ajuste foi avaliada através dos métodos: curvas ROC, Pearson’s X2-test e
Worst-fit.
Resultados: Os valores de D50, γ e s para a xerostomia G2 nos períodos de follow-up
de 12,18 e 24 meses considerando a dose fornecida na parótida contra-lateral foram
38.6, 0.707, 1x10-4; 51.7, 0.444, 1x10-4; e 48.3, 0.685, 1x10-4, respetivamente. Para a
soma das parótidas estes foram 39.2, 0.730, 1x10-4; 54.2, 0.468, 1x10-4; e 51.7, 0.633,
1x10-4, respetivamente. A análise estatística do modelo demonstrou que o modelo
Relative Seriality para xerostomia G2 considerando a dose fornecida nas parótidas
contra-laterais e soma das parótidas tem uma qualidade razoável-boa (intervalo de 0.6
a 0.7) enquanto que o modelo derivado para quantificar a xerostomia G1+G2 só
atingiu uma qualidade razoável (aproximadamente 0.6).
Conclusões: Usando os parâmetros derivados para o modelo Reltive Seriality, pode
ser feita uma melhor previsão da probabilidade de xerostomia G2, do que para
xerostomia G1+G2. Os melhores parâmetros rádio-biológicos foram obtidos através
viii
da utilização da dose que irradiou as parótidas contra-laterais e soma das parótidas
para os períodos de follow-up de 12, 18 e 24 meses. De forma a minimizar a
probabilidade de xerostomia, a dose administrada às parótidas deve ser inferior a
28Gy.
Xerostomia, Glândulas salivares, Curvas dose-resposta, Modelo Relative
Seriality, Tumores de cabeça e pescoço
Clinical implementation of radiobiological measures in treatment planning. Why has it taken so long?
No full textThis article is an editorial, and it doesn't include an abstract. Full text of this article is available in HTML and PDF.Cite this article as:Mavroidis P. Clinical implementation of radiobiological measures in treatment planning. Why has it taken so long? Int J Cancer Ther Oncol 2013;1(1):01019.DOI: 10.14319/ijcto.0101.9-------------------------------
Case study of physiotherapy treatment of a patient with the diagnosis Ankle Distortion
No full textTitle: Physiotherapeutic treatment of a patient with ankle distortion Nazev: Fyzioterapeutická léčba pacienta s zkreslení kotníku Author: Vryonides Panayiotis Location of clinical practice: C.L.P.A (Centrum léčby pohybového aparátu) Aim The purpose of my bachelor thesis is to understand the structure and function of the ankle joint as well to discuss the most common injuries concerning the ankle. Moreover a day-to-day rehabilitation program will be presented concerning ankle distortion. Summary The bachelor thesis consists of two major parts, the general part where an extensive analysis concerning the diagnosis (ankle distortion), the anatomy, biomechanics and common injuries takes place. Moreover it follows the practical part, which also is the main part of the thesis. It consist the anamnesis, all the initial and final examinations and the day after day rehabilitation procedures and progress. Regarding the therapeutic session, they were composed with stability exercises, sensomotoric stimulation, strengthening and also from physical therapy laser. Results Subsequently of the eight rehabilitation sessions that I had with my patient, he fully recovers. The pain and the limitation on the ankle joint that he had wasn't enormous as a result to succeed great results in that limited time that we had. A..
Simulation of TIOA
No full textThesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 73-74).This Master of Engineering Thesis describes the design, implementation, and usage of the TIOA Simulator. The TIOA Simulator, along with the other components of the TIOA Toolset aims to provide a framework for developing dependable distributed systems. The project is based on the Timed Input/Output Automaton framework, and supports TIOA, a formal language for specifying timed I/O automata. Simulation of TIOA programs is useful in the process of testing the proposed system over a specific set of executions. During the execution the Simulator is able to test proposed invariants and validate a proposed simulation relation between the system's implementation and its specification. A step correspondence between the steps of the implementation and the specification drives the validation of the simulation relation. The identification and validation of the invariants and the simulation relation constitutes the first step towards a formal verification of the system's correctness. The proposed step correspondence can be used in a formal proof to show that the proposed relation is indeed a simulation relation.by Panayiotis P. Mavrommatis.M.Eng
Improving temporal interpolation of head and body pose using Gaussian process regression in a matrix completion setting
No full textThis paper presents a model for head and body pose estimation (HBPE) when labelled samples are highly sparse. The current state-of-the-art multimodal approach to HBPE utilizes the matrix completion method in a transductive setting to predict pose labels for unobserved samples. Based on this approach, the proposed method tackles HBPE when manually annotated ground truth labels are temporally sparse. We posit that the current state of the art approach oversimplifies the temporal sparsity assumption by using Laplacian smoothing. Our final solution uses: i) Gaussian process regression in place of Laplacian smoothing, ii) head and body coupling, and iii) nuclear norm minimization in the matrix completion setting. The model is applied to the challenging SALSA dataset for benchmark against the state-of-the-art method. Our presented formulation outperforms the state-of-the-art significantly in this particular setting, e.g. at 5% ground truth labels as training data, head pose accuracy and body pose accuracy is approximately 62% and 70%, respectively. As well as fitting a more flexible model to missing labels in time, we posit that our approach also loosens the head and body coupling constraint, allowing for a more expressive model of the head and body pose typically seen during conversational interaction in groups. This provides a new baseline to improve upon for future integration of multimodal sensor data for the purpose of HBPE.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pattern Recognition and Bioinformatic
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