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1.
Br J Radiol ; 93(1107): 20190584, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31977241

RESUMO

OBJECTIVE: We compared the sensitivity of intensity modulated proton therapy (IMPT) and photon volumetric modulated arc therapy (VMAT) plans to setup uncertainties in locally advanced non-small cell lung cancer (NSCLC) using probabilistic scenarios. METHODS: Minimax robust (MM) and planning target volume (PTV) optimised IMPT and VMAT nominal plans were created with physical dose of 70 Gy in 35 fractions in 10 representative patients. Using population data of setup errors, a fractionated treatment course was simulated, summed (Dsum) and compared to the nominal plan. Three treatment-course simulations were done for each plan. Target robustness criteria were: dose deviation of ≤5% to clinical target volume (CTV) D98% and CTV V95% ≥ 99.9%. Voxelwise simulation repeatability was analysed using Bland-Altman plots. Acceptable limits of agreement were 2% of the prescription dose. RESULTS: All Dsum met target robustness criteria. While fraction VMAT and MM-IMPT doses were excellent, simulated fraction doses in PTV-IMPT were suboptimal. Almost all (>99%) of VMAT and MM-IMPT fraction doses met both target robustness criteria. For PTV-IMPT, only 96.9 and 80.3% of fractions met CTVD98% and V95% criteria respectively. Simulation repeatability was excellent (limits of agreement range: 0.41-1.1 Gy) with strong positive correlations. CONCLUSION: When considering the whole treatment course, setup errors do not influence robustness irrespective of planning techniques used. However, on a fraction level, VMAT and MM-IMPT plans are superior compared to PTV-IMPT plans. ADVANCES IN KNOWLEDGE: Probabilistic analysis provides a fast and practical method for evaluating VMAT and IMPT plan sensitivity against setup uncertainty. VMAT and robust-optimised IMPT plans have comparable sensitivity to setup uncertainties in conventionally fractionated treatment for NSCLC.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/radioterapia , Neoplasias Pulmonares/radioterapia , Fótons/uso terapêutico , Terapia com Prótons/métodos , Erros de Configuração em Radioterapia , Radioterapia de Intensidade Modulada/métodos , Incerteza , Carcinoma Pulmonar de Células não Pequenas/diagnóstico por imagem , Carcinoma Pulmonar de Células não Pequenas/patologia , Fracionamento da Dose de Radiação , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/patologia , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
2.
Br J Radiol ; 93(1107): 20190673, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31600082

RESUMO

OBJECTIVE: The Pediatric Proton/Photon Consortium Registry (PPCR) is a comprehensive data registry composed of pediatric patients treated with radiation. It was established to expedite outcomes-based research. The attributes which allow the PPCR to be a successful collaboration are reviewed. METHODS AND MATERIALS: Current eligibility criteria are radiotherapy patients < 22 years treated at one of the 15 US participating institutions. Detailed health and treatment data are collected about the disease presentation and treatment exposures, and annually thereafter, in REDCap (Research Electronic Data Capture). DICOM (Digital Imaging and Communications in Medicine) imaging and radiation plans are collected through MIM/MIMcloud. An optional patient-reported quality-of-life (PedsQL) study is administered at 10 sites. RESULTS: Accrual started October 2012 with 2,775 participants enrolled as of 25 July 2019. Most patients, 62.0%, were treated for central nervous system (CNS) tumors, the most common of which are medulloblastoma (n = 349), ependymoma (n = 309), and glial/astrocytoma tumors (n = 279). The most common non-CNS diagnoses are rhabdomyosarcoma (n = 284), Ewing's sarcoma (n = 153), and neuroblastoma (n = 130). While the majority of participants are US residents, 18.7% come from 36 other countries. Over 685 patients participate in the PedsQL study. CONCLUSIONS: The PPCR is a valuable research platform capable of answering countless research questions that will ultimately improve patient care. Centers outside of the USA are invited to participate directly or may engage with the PPCR to align data collection strategies to facilitate large-scale international research. ADVANCES IN KNOWLEDGE: For investigators looking to carry out research in a large pediatric oncology cohort or interested in registry work, this paper provides an updated overview of the PPCR.


Assuntos
Coleta de Dados/normas , Neoplasias/radioterapia , Fótons/uso terapêutico , Terapia com Prótons/estatística & dados numéricos , Sistema de Registros/estatística & dados numéricos , Adolescente , Astrocitoma/radioterapia , Neoplasias do Sistema Nervoso Central/radioterapia , Neoplasias Cerebelares/radioterapia , Criança , Pré-Escolar , Computação em Nuvem , Ependimoma/radioterapia , Feminino , Glioma/radioterapia , Humanos , Lactente , Cooperação Internacional , Masculino , Meduloblastoma/radioterapia , Medidas de Resultados Relatados pelo Paciente , Qualidade de Vida , Autorrelato , Adulto Jovem
3.
Br J Radiol ; 93(1107): 20190225, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31432694

RESUMO

Recent studies on cancer stem cells revealed they are tumorigenic and able to recapitulate the characteristics of the tumour from which they derive, so that it was suggested that elimination of this population is essential to prevent recurrences after any treatment. However, there is evidence that cancer stem cells are inherently resistant to conventional (photon) radiotherapy. Since the use of proton beam therapy in cancer treatment is growing rapidly worldwide, mainly because of their excellent dosimetric properties, the possibility could be considered that they also have biological advantages through preferential elimination of cancer stem cells.Indeed, a review of preclinical data suggest that protons and photons differ in their biological effects on cancer stem cells, with protons offering potential advantages, although the heterogeneity of cancer stem cells and the different proton irradiation modalities make the comparison of the results not so easy. Further research to understand the mechanisms underlying such effects is important for their possible exploitation in clinics and to perform proton beam therapy optimization.


Assuntos
Células-Tronco Neoplásicas/efeitos da radiação , Fótons/uso terapêutico , Terapia com Prótons/métodos , Humanos , Recidiva Local de Neoplasia/prevenção & controle
4.
Br J Radiol ; 93(1107): 20190582, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31778317

RESUMO

Range uncertainty is a much discussed topic in proton therapy. Although a very real aspect of proton therapy, its magnitude and consequences are sometimes misunderstood or overestimated. In this article, the sources and consequences of range uncertainty are reviewed, a number of myths associated with the effect discussed with the aim of putting range uncertainty into clinical context and attempting to de-bunk some of the more exaggerated claims made as to its consequences.


Assuntos
Terapia com Prótons/métodos , Incerteza , Absorção de Radiação , Humanos , Neoplasias Induzidas por Radiação , Posicionamento do Paciente , Fótons/uso terapêutico , Terapia com Prótons/efeitos adversos , Dosagem Radioterapêutica , Resultado do Tratamento , Água
5.
Br J Radiol ; 93(1107): 20190879, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31804145

RESUMO

OBJECTIVE: Locally recurrent disease is of increasing concern in (non-)small cell lung cancer [(N)SCLC] patients. Local reirradiation with photons or particles may be of benefit to these patients. In this multicentre in silico trial performed within the Radiation Oncology Collaborative Comparison (ROCOCO) consortium, the doses to the target volumes and organs at risk (OARs) were compared when using several photon and proton techniques in patients with recurrent localised lung cancer scheduled to undergo reirradiation. METHODS: 24 consecutive patients with a second primary (N)SCLC or recurrent disease after curative-intent, standard fractionated radio(chemo)therapy were included in this study. The target volumes and OARs were centrally contoured and distributed to the participating ROCOCO sites. Remaining doses to the OARs were calculated on an individual patient's basis. Treatment planning was performed by the participating site using the clinical treatment planning system and associated beam characteristics. RESULTS: Treatment plans for all modalities (five photon and two proton plans per patient) were available for 22 patients (N = 154 plans). 3D-conformal photon therapy and double-scattered proton therapy delivered significantly lower doses to the target volumes. The highly conformal techniques, i.e., intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), CyberKnife, TomoTherapy and intensity-modulated proton therapy (IMPT), reached the highest doses in the target volumes. Of these, IMPT was able to statistically significantly decrease the radiation doses to the OARs. CONCLUSION: Highly conformal photon and proton beam techniques enable high-dose reirradiation of the target volume. They, however, significantly differ in the dose deposited in the OARs. The therapeutic options, i.e., reirradiation or systemic therapy, need to be carefully weighed and discussed with the patients. ADVANCES IN KNOWLEDGE: Highly conformal photon and proton beam techniques enable high-dose reirradiation of the target volume. In light of the abilities of the various highly conformal techniques to spare specific OARs, the therapeutic options need to be carefully weighed and patients included in the decision-making process.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/radioterapia , Neoplasias Pulmonares/radioterapia , Recidiva Local de Neoplasia/radioterapia , Órgãos em Risco/efeitos da radiação , Fótons/uso terapêutico , Terapia com Prótons/métodos , Reirradiação/métodos , Carcinoma Pulmonar de Células não Pequenas/diagnóstico por imagem , Conjuntos de Dados como Assunto , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Recidiva Local de Neoplasia/diagnóstico por imagem , Órgãos em Risco/diagnóstico por imagem , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Radioterapia de Intensidade Modulada/métodos , Resultado do Tratamento
6.
Br J Radiol ; 93(1107): 20190594, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31647313

RESUMO

It is recognized that the use of a single plan calculated on an image acquired some time before the treatment is generally insufficient to accurately represent the daily dose to the target and to the organs at risk. This is particularly true for protons, due to the physical finite range. Although this characteristic enables the generation of steep dose gradients, which is essential for highly conformal radiotherapy, it also tightens the dependency of the delivered dose to the range accuracy. In particular, the use of an outdated patient anatomy is one of the most significant sources of range inaccuracy, thus affecting the quality of the planned dose distribution. A plan should be ideally adapted as soon as anatomical variations occur, ideally online. In this review, we describe in detail the different steps of the adaptive workflow and discuss the challenges and corresponding state-of-the art developments in particular for an online adaptive strategy.


Assuntos
Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Terapia com Prótons/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Fluxo de Trabalho , Humanos , Órgãos em Risco , Fótons/uso terapêutico , Dosagem Radioterapêutica
7.
Br J Radiol ; 93(1107): 20190572, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31651185

RESUMO

OBJECTIVE: Approximately 70 patients with large and bulky tumors refractory to prior treatments were treated with photon spatially fractionated GRID radiation (SFGRT). We identified 10 additional patients who clinically needed GRID but could not be treated with photons due to adjacent critical organs. We developed a proton SFGRT technique, and we report treatment of these 10 patients. METHODS: Subject data were reviewed for clinical results and dosimetric data. 50% of the patients were metastatic at the time of treatment and five had previous photon radiation to the local site but not via GRID. They were treated with 15-20 cobalt Gray equivalent using a single proton GRID field with an average beamlet count of 22.6 (range 7-51). 80% received an average adjuvant radiation dose to the GRID region of 40.8Gy (range 13.7-63.8Gy). Four received subsequent systemic therapy. RESULTS: The median follow-up time was 5.9 months (1.1-18.9). At last follow-up, seven patients were alive and three had died. Two patients who had died from metastatic disease had local shrinkage of tumor. Of those alive, four had complete or partial response, two had partial response but later progressed, and one had no response. For all patients, the tumor regression/local symptom improvement rate was 80%. 50% had acute side-effects of grade1/2 only and all were well-tolerated. CONCLUSION: In circumstances where patients cannot receive photon GRID, proton SFGRT is clinically feasible and effective, with a similar side-effect profile. ADVANCES IN KNOWLEDGE: Proton GRID should be considered as a treatment option earlier in the disease course for patients who cannot be treated by photon GRID.


Assuntos
Neoplasias/radioterapia , Terapia com Prótons/métodos , Fracionamento da Dose de Radiação , Estudos de Viabilidade , Seguimentos , Humanos , Neoplasias/mortalidade , Neoplasias/patologia , Órgãos em Risco/diagnóstico por imagem , Fótons/uso terapêutico , Resultado do Tratamento
8.
Br J Radiol ; 93(1107): 20190590, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31642709

RESUMO

Pre-treatment CT imaging is a topic of growing importance in particle therapy. Improvements in the accuracy of stopping-power prediction are demanded to allow for a dose conformality that is not inferior to state-of-the-art image-guided photon therapy. Although range uncertainty has been kept practically constant over the last decades, recent technological and methodological developments, like the clinical application of dual-energy CT, have been introduced or arise at least on the horizon to improve the accuracy and precision of range prediction. This review gives an overview of the current status, summarizes the innovations in dual-energy CT and its potential impact on the field as well as potential alternative technologies for stopping-power prediction.


Assuntos
Terapia com Prótons , Radioterapia Guiada por Imagem/métodos , Tomografia Computadorizada por Raios X/métodos , Incerteza , Algoritmos , Humanos , Imagem por Ressonância Magnética , Fótons/uso terapêutico , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/instrumentação , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Radioterapia Guiada por Imagem/instrumentação , Tomografia Computadorizada por Raios X/instrumentação
9.
Br J Radiol ; 93(1107): 20190494, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31687835

RESUMO

Clinical parameters and empirical evidence are the primary determinants for current treatment planning in radiation oncology. Personalized medicine in radiation oncology is only at the very beginning to take the genetic background of a tumor entity into consideration to define an individual treatment regimen, the total dose or the combination with a specific anticancer agent. Likewise, stratification of patients towards proton radiotherapy is linked to its physical advantageous energy deposition at the tumor site with minimal healthy tissue being co-irradiated distal to the target volume. Hence, the fact that photon and proton irradiation also induce different qualities of DNA damages, which require differential DNA damage repair mechanisms has been completely neglected so far. These subtle differences could be efficiently exploited in a personalized treatment approach and could be integrated into personalized treatment planning. A differential requirement of the two major DNA double-strand break repair pathways, homologous recombination and non-homologous end joining, was recently identified in response to proton and photon irradiation, respectively, and subsequently influence the mode of ionizing radiation-induced cell death and susceptibility of tumor cells with defects in DNA repair machineries to either quality of ionizing radiation.This review focuses on the differential DNA-damage responses and subsequent biological processes induced by photon and proton irradiation in dependence of the genetic background and discusses their impact on the unicellular level and in the tumor microenvironment and their implications for combined treatment modalities.


Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA/fisiologia , Fótons/uso terapêutico , Medicina de Precisão , Terapia com Prótons , Eficiência Biológica Relativa , Absorção de Radiação , Animais , Morte Celular/efeitos da radiação , Linhagem Celular Tumoral/efeitos da radiação , Terapia Combinada , Reparo do DNA por Junção de Extremidades , Humanos , Transferência Linear de Energia , Neoplasias/genética , Neoplasias/radioterapia , Órgãos em Risco/efeitos da radiação , Tolerância a Radiação/genética , Radiação Ionizante , Microambiente Tumoral
10.
Br J Radiol ; 93(1107): 20190334, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31738081

RESUMO

Dose in proton radiotherapy is generally prescribed by scaling the physical proton dose by a constant value of 1.1. Relative biological effectiveness (RBE) is defined as the ratio of doses required by two radiation modalities to cause the same level of biological effect. The adoption of an RBE of 1.1. assumes that the biological efficacy of protons is similar to photons, allowing decades of clinical dose prescriptions from photon treatments and protocols to be utilized in proton therapy. There is, however, emerging experimental evidence that indicates that proton RBE varies based on technical, tissue and patient factors. The notion that a single scaling factor may be used to equate the effects of photons and protons across all biological endpoints and doses is too simplistic and raises concern for treatment planning decisions. Here, we review the models that have been developed to better predict RBE variations in tissue based on experimental data as well as using a mechanistic approach.


Assuntos
Modelos Teóricos , Neoplasias/radioterapia , Terapia com Prótons/métodos , Lesões por Radiação , Eficiência Biológica Relativa , Algoritmos , Animais , Linhagem Celular Tumoral , DNA/efeitos da radiação , Reparo do DNA , Humanos , Modelos Biológicos , Método de Monte Carlo , Órgãos em Risco/efeitos da radiação , Fótons/uso terapêutico , Planejamento da Radioterapia Assistida por Computador
11.
Semin Radiat Oncol ; 30(1): 77-86, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31727303

RESUMO

The purpose of this study was to review the limitations of dose calculation formalisms for photon-emitting brachytherapy sources based on the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) report and to provide recommendations to transition to model-based dose calculation algorithms. Additionally, an overview of these algorithms and approaches is presented. The influence of tissue and seed/applicator heterogeneities on brachytherapy dose distributions for breast, gynecologic, head and neck, rectum, and prostate cancers as well as eye plaques and electronic brachytherapy treatments were investigated by comparing dose calculations based on the TG-43 formalism and model-based dose calculation algorithms.


Assuntos
Braquiterapia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Algoritmos , Feminino , Humanos , Masculino , Modelos Teóricos , Neoplasias/radioterapia , Fótons/uso terapêutico , Guias de Prática Clínica como Assunto , Radiometria , Dosagem Radioterapêutica , Sociedades Médicas
12.
Br J Radiol ; 93(1107): 20190412, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31868525

RESUMO

Proton therapy has shown dosimetric advantages over conventional radiation therapy using photons. Although the integral dose for patients treated with proton therapy is low, concerns were raised about late effects like secondary cancer caused by dose depositions far away from the treated area. This is especially true for neutrons and therefore the stray dose contribution from neutrons in proton therapy is still being investigated. The higher biological effectiveness of neutrons compared to photons is the main cause of these concerns. The gold-standard in neutron dosimetry is measurements, but performing neutron measurements is challenging. Different approaches have been taken to overcome these difficulties, for instance with newly developed neutron detectors. Monte Carlo simulations is another common technique to assess the dose from secondary neutrons. Measurements and simulations are used to develop analytical models for fast neutron dose estimations. This article tries to summarize the developments in the different aspects of neutron dose in proton therapy since 2017. In general, low neutron doses have been reported, especially in active proton therapy. Although the published biological effectiveness of neutrons relative to photons regarding cancer induction is higher, it is unlikely that the neutron dose has a large impact on the second cancer risk of proton therapy patients.


Assuntos
Neoplasias Induzidas por Radiação/etiologia , Segunda Neoplasia Primária/etiologia , Nêutrons/efeitos adversos , Terapia com Prótons/métodos , Humanos , Método de Monte Carlo , Fótons/uso terapêutico , Terapia com Prótons/efeitos adversos , Radiometria/instrumentação , Radiometria/métodos , Dosagem Radioterapêutica , Eficiência Biológica Relativa
13.
Phys Med ; 66: 88-96, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31574423

RESUMO

PURPOSE: To perform a systematic and thorough assessment, using the Uncomplicated and Cancer-Free Control Probability (UCFCP) function, of a broad range of photon prostate cancer RT treatments, on the same scenario (a unique pelvic CT set). UCFCP considers, together with the probabilities of local tumour control (TCP) and deterministic (late) sequelae (NTCP), the second primary cancer risk (SPCR) due to photon and neutron peripheral doses. METHODS AND MATERIALS: Thirty-six radiotherapy plans were produced for the same CT. 6, 10, 15 and 18 MV 3DCRT, IMRT and VMAT (77.4 Gy in 43 fractions) and 6 and 10 MV SBRT (36.25 Gy in 5 fractions with flattened and FFF beams) for Elekta, Siemens and Varian Linacs plans were included. DVH and peripheral organ dosimetry were used to compute TCP, NTCP, and SPCR (the competition and LNT models) for further plan ranking. RESULTS: Biological models (and parameters) used predicted an outcome which is in agreement with epidemiological findings. SBRT plans showed the lowest SPCR and a below average NTCPrectal. High energy plans did not rank worse than the low energy ones. Intensity modulated plans were ranked above the 3D conformal techniques. CONCLUSIONS: According to UCFCP, the best plans were the10 MV SBRTs. SPCR rates were low and did not show a substantial impact on plan ranking. High energy intensity-modulated plans did not increase in excess the average of SPCR. Even more, they ranked among the best, provided that MU were efficiently managed.


Assuntos
Fótons/uso terapêutico , Neoplasias da Próstata/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional , Humanos , Masculino , Probabilidade , Neoplasias da Próstata/diagnóstico por imagem , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada , Tomografia Computadorizada por Raios X
14.
Cancer Radiother ; 23(6-7): 625-629, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31447346

RESUMO

Recent technological developments in linear accelerators (linacs) and their imaging systems have made it possible to routinely perform stereotactic radiotherapy (SRT) treatments. To ensure the security and quality of the treatments, national and international recommendations have been written. This review focuses on the recommendations of the report 91 of the International Commission on Radiation Units (ICRU) on stereotactic treatments with small photon beams and proposes to answer the question of the eligibility of the commercially available accelerators for the treatment of extra-cranial SRT (SBRT). The ICRU 91 report outlines important features needed to respect the constraints, which are high intensity photon beam, integrated image-guidance, high mechanical accuracy of the linac, multileaf collimator with reduced leaf width, bundled motion management and bundled 6 Dimensional "robotic" couch tabletop. Most of the contemporary linacs meet these recommendations, in particular, stereotactic dedicated linacs, or modern gantry-based linacs equipped with 3 dimensional cone-beam CT imaging and 2D-stereoscopic planar imaging. Commercially available ring-based linacs have some limitations: they offer only coplanar treatments, and couch movements are limited to translations and, some have limited imaging equipment and no ability to manage intrafraction motion. However, for performing SBRT, non-coplanar irradiations are not mandatory, contrarily to intracranial stereotactic irradiations. Furthermore, patients' rotations can be corrected, thanks to real-time adaptive radiotherapy available on MRI-linacs. Finally, significant improvements are expected in the short term to compensate the weaknesses of the current devices.


Assuntos
Fidelidade a Diretrizes , Agências Internacionais/normas , Neoplasias/radioterapia , Aceleradores de Partículas/normas , Radiocirurgia/instrumentação , Desenho de Equipamento/normas , Humanos , Imobilização/instrumentação , Fótons/uso terapêutico , Garantia da Qualidade dos Cuidados de Saúde , Radiocirurgia/métodos , Radiocirurgia/normas , Radioterapia Guiada por Imagem/normas
15.
Med Phys ; 46(9): 3844-3863, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31276215

RESUMO

PURPOSE: Despite the availability of multiple energy photon beams on clinical linear accelerators, volumetric modulated arc therapy (VMAT) optimization is currently limited to a single photon beam. The purpose of this work was to present a proof-of-principle study on an algorithm for simultaneous optimization of mixed photon beams for VMAT (MP - VMAT), utilizing an additional photon energy as an additional degree of freedom. METHODS: The MP - VMAT optimization algorithm is presented as a two-step heuristic approach. First, a convex linear programming problem is solved for simultaneous optimization of nonuniform dual energy intensity maps (DEIMs) for an angular resolution of 36 equi-spaced beam segments. Subsequently, for a given gantry speed schedule, the second step aims to best replicate each DEIM by dispersing MP - VMAT apertures along with their corresponding intensities over their respective beam segment. This constitutes a nonlinear problem, which is linearized using McCormick relaxation. The final large-scale mixed integer linear programming (MILP) dispersion model ensures a contiguous and smooth transition of multileaf collimators (MLCs) from one beam segment to the next. To demonstrate the proof-of-principle, we first compared the quality of dose volume histograms (DVHs) of MP - VMAT to the ones calculated from 36 DEIMs following the step 1 of MP - VMAT model. Additionally, the MLCs motion violations were evaluated for the complete 360° gantry rotation for gantry speeds ranging from 1 to 6° per second. The quality of MP - VMAT plans were also compared to conventional single energy VMAT plans via DVH, homogeneity index (HI), and conformity number (CN) for two prostate cases. RESULTS: The MP - VMAT model resulted in a successful convergence of DVHs relative to the ones from DEIMs with HI and CN of 0.05 and 0.9, respectively, for 1 and 2° per second gantry speed schedules. In replicating the DEIMs, the MILP dispersion model was able to achieve optimality for almost all segments at 1° per second and for majority of segments at 2° per second. Although, DVHs quality was slightly inferior for 3° per second gantry speed, the target conformity of 0.9 and heterogeneity of 0.08 were achievable even for the suboptimal solutions. No violations of the MLC constraints were observed throughout the complete 360 degree arc rotation for any gantry speed schedule, thereby confirming MILP dispersion model. For the two prostate cases, the results showed MP - VMAT's ability to achieve substantial dose reduction in rectum and bladder while yielding similar target coverage compared to single energy VMAT. Bladder volume was mostly spared in low-to-intermediate dose region. Rectal volume sparing (3 % to 12 %) was observed in the intermediate (from 25 to 50 Gy) dose region. CONCLUSION: We demonstrate the first formalism of a large-scale simultaneous optimization of mixed photon energy beams for VMAT. Dosimetric comparison of MP - VMAT to single energy VMAT demonstrated potential advantages of using mixed photon energy beams for prostate plans, thus providing an impetus for further testing on a large clinical cohort.


Assuntos
Fótons/uso terapêutico , Radioterapia de Intensidade Modulada/métodos , Movimento , Radiometria , Planejamento da Radioterapia Assistida por Computador
16.
Cancer Radiother ; 23(8): 922-925, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31257097

RESUMO

The purpose of this work was reducing treatment-related toxicity for Hodgkin lymphomas using practical procedure inspired by the ILROG guidelines. Reporting the first case of localized Hodgkin lymphoma treated with protontherapy in France. A 24-year-old female with mediastinal, bulky, localized, mixed-cellularity, classic Hodgkin lymphoma required an involved-site radiation therapy after complete response following polychemotherapy. Three-dimensional conformal radiation therapy was not acceptable due to high doses to breasts, heart and lungs. We realized a four-dimensional computed tomography (CT) to evaluate target movements and another CT with gating and breath-hold technique. Delineation was performed on both CT using the initial fluorodeoxyglucose positron-emission tomography/CT. One dosimetric plan with rotational intensity-modulated radiation therapy with a helical Tomotherapy© was realized and compared to another one with conformational protontherapy. Ninety-five percent of the planning target volume was covered by 98 and 99% of the prescribed dose with protontherapy and helical Tomotherapy©. Protontherapy provided the best organ at risk protection. Lung and heart protections were better with protontherapy: lung mean dose (3.7Gy vs. 8.4Gy) and median dose (0.002Gy vs. 6.9Gy), heart mean dose (2.6Gy vs. 3.7Gy). Breast sparing was better for both breasts using protontherapy: right breast mean dose (2.4Gy vs. 4.4Gy) and left (1.9Gy vs. 4.6Gy). The biggest difference was seen with low doses, which were better with protontherapy: volume of lung receiving 5Gy was 17.5% vs. 54.2% with Helical Tomotherapy©. In view of these results, we decided to treat our patient with protontherapy using respiratory assessment. We delivered 30Gy (15 fractions) using protontherapy with one direct anterior field using pencil beam scanning and deep inspiration breath-hold technique. We observed only grade 1 skin erythema during treatment and no toxicity during early follow-up.


Assuntos
Doença de Hodgkin/radioterapia , Neoplasias do Mediastino/radioterapia , Fótons/uso terapêutico , Terapia com Prótons/métodos , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Bleomicina/administração & dosagem , Ciclofosfamida/administração & dosagem , Doxorrubicina/administração & dosagem , Etoposídeo/administração & dosagem , Feminino , Coração/diagnóstico por imagem , Doença de Hodgkin/diagnóstico por imagem , Doença de Hodgkin/tratamento farmacológico , Humanos , Pulmão/diagnóstico por imagem , Neoplasias do Mediastino/diagnóstico por imagem , Neoplasias do Mediastino/tratamento farmacológico , Tratamentos com Preservação do Órgão/métodos , Órgãos em Risco/diagnóstico por imagem , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Guias de Prática Clínica como Assunto , Prednisona/administração & dosagem , Procarbazina/administração & dosagem , Lesões por Radiação/prevenção & controle , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada , Vincristina/administração & dosagem , Adulto Jovem
17.
Med Phys ; 46(10): 4314-4323, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31332792

RESUMO

PURPOSE: We investigated the impact on computed tomography (CT) image quality and photon, electron, and proton head-and-neck (H&N) radiotherapy (RT) dose calculations of three CT metal artifact reduction (MAR) approaches: A CT-based algorithm (oMAR Philips Healthcare), manual water override, and our recently presented, Magnetic Resonance (MR)-based kerMAR algorithm. We considered the following three hypotheses: I: Manual water override improves MAR over the CT- and MR-based alternatives; II: The automatic algorithms (oMAR and kerMAR) improve MAR over the uncorrected CT; III: kerMAR improves MAR over oMAR. METHODS: We included a veal shank phantom with/without six metal inserts and nine H&N RT patients with dental implants. We quantified the MAR capabilities by the reduction of outliers in the CT value distribution in regions of interest, and the change in particle range and photon depth at maximum dose. RESULTS: Water override provided apparent image improvements in the soft tissue region but insignificantly or negatively influenced the dose calculations. We however found significant improvements in image quality and particle range impact, compared to the uncorrected CT, when using oMAR and kerMAR. kerMAR in turn provided superior improvements in terms of high intensity streak suppression compared to oMAR, again with associated impacts on the particle range estimates. CONCLUSION: We found no benefits of the water override compared to the rest, and tentatively reject hypothesis I. We however found improvements in the automatic algorithms, and thus support for hypothesis II, and found the MR-based kerMAR to improve upon oMAR, supporting hypothesis III.


Assuntos
Artefatos , Neoplasias de Cabeça e Pescoço/diagnóstico por imagem , Neoplasias de Cabeça e Pescoço/radioterapia , Imagem por Ressonância Magnética , Metais , Tomografia Computadorizada por Raios X , Elétrons/uso terapêutico , Humanos , Fótons/uso terapêutico , Terapia com Prótons , Estudos Retrospectivos
18.
Phys Med ; 62: 13-19, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31153393

RESUMO

PURPOSE: The present work aimed to evaluate organ doses and related risk for cancer from external beam radiation treatment (EBRT) and high-dose-rate (HDR) brachytherapy (BT) involving Co-60 source for patients with cervical carcinoma in Tanzania based on Monte Carlo methods and to evaluate the secondary cancer risks in their lifetime. METHODS: EBRT and HDR-BR were modelled by using the MCNPX Monte Carlo (MC) code. The MC simulations were performed by using validated models and isocentric irradiation of an adult female computational phantom. The organ doses and cancer risks estimates were obtained. RESULTS: The highest absorbed doses of 6.98 × 10-2 and 5.74 × 10-2 Sv/Gy were recorded in the bladder for BT and EBRT. The higher risk was found for colon at 1.06 × 10-3 in the HDR-BT and 9.75 × 10-5 in the EBRT per 100,000 population at exposure age of 35 years than in the other organs. The risk magnitude decreased with increasing age at exposure. In general, the secondary cancer risks in all sites considered from EBRT and HDR-BR for cervical cancer patient were lower than the baseline risks. CONCLUSIONS: The chances of developing secondary cancer take years following radiation therapy are extremely low, but the results of present study can support to establish a future database on secondary cancer risks involving radiation therapy in patients with cervical cancer by using HDR-BR and EBRT with Co-60 source in Tanzania and other developing countries.


Assuntos
Radioisótopos de Cobalto/efeitos adversos , Método de Monte Carlo , Neoplasias Induzidas por Radiação/etiologia , Fótons/efeitos adversos , Doses de Radiação , Espalhamento de Radiação , Neoplasias do Colo do Útero/radioterapia , Braquiterapia/efeitos adversos , Radioisótopos de Cobalto/uso terapêutico , Feminino , Humanos , Pessoa de Meia-Idade , Segunda Neoplasia Primária/etiologia , Órgãos em Risco/efeitos da radiação , Fótons/uso terapêutico , Dosagem Radioterapêutica , Risco , Tanzânia
19.
Nucl Med Commun ; 40(6): 618-625, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31095527

RESUMO

INTRODUCTION: Radiation pneumonitis is a major dose-limiting complication in thoracic radiation therapy (RT) and presents clinically in the first few months after RT. We evaluated the feasibility of quantifying pulmonary parenchymal glycolysis (PG) as a surrogate of global lung inflammation and radiation-induced pulmonary toxicity using a novel semiautomatic lung segmentation technique in non-small-cell lung cancer (NSCLC) patients and compared PG in patients treated with photon or proton RT. PATIENTS AND METHODS: We evaluated 18 consecutive locally advanced NSCLC patients who underwent pretreatment and post-treatment F-FDG PET/CT treated with definitive (median: 66.6 Gy; 1.8 Gy fractions) photon or proton RT between 2010 and 2014. Lung volume segmentation was conducted using 3D Slicer by performing simple thresholding. Pulmonary PG was calculated by summing F-FDG uptake in the whole lung. RESULTS: In nine patients treated with photon RT, significant increases in PG in both ipsilateral (mean difference: 1400±510; P=0.02) and contralateral (mean difference: 1200±450; P=0.03) lungs were noted. In nine patients treated with proton therapy, no increase in pulmonary PG was observed in either the ipsilateral (P=0.30) or contralateral lung (P=0.98). CONCLUSION: We observed a significant increase in global lung inflammation bilaterally as measured by quantification of PG. However, no significant change in global lung inflammation was noted after proton therapy. Future larger studies are needed to determine whether this difference correlates with lower risks of radiation pneumonitis in NSCLC patients treated with proton therapy.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/terapia , Fluordesoxiglucose F18 , Neoplasias Pulmonares/terapia , Fótons/efeitos adversos , Pneumonia/diagnóstico por imagem , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Terapia com Prótons/efeitos adversos , Idoso , Carcinoma Pulmonar de Células não Pequenas/patologia , Quimiorradioterapia/efeitos adversos , Feminino , Humanos , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Fótons/uso terapêutico , Pneumonia/etiologia , Lesões por Radiação/diagnóstico por imagem , Lesões por Radiação/etiologia , Estudos Retrospectivos
20.
J Appl Clin Med Phys ; 20(6): 45-52, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31081175

RESUMO

Computed tomography (CT) data are required to calculate the dose distribution in a patient's body. Generally, there are two CT number calibration methods for commercial radiotherapy treatment planning system (RTPS), namely CT number-relative electron density calibration (CT-RED calibration) and CT number-mass density calibration (CT-MD calibration). In a previous study, the tolerance levels of CT-RED calibration were established for each tissue type. The tolerance levels were established when the relative dose error to local dose reached 2%. However, the tolerance levels of CT-MD calibration are not established yet. We established the tolerance levels of CT-MD calibration based on the tolerance levels of CT-RED calibration. In order to convert mass density (MD) to relative electron density (RED), the conversion factors were determined with adult reference computational phantom data available in the International Commission on Radiological Protection publication 110 (ICRP-110). In order to validate the practicability of the conversion factor, the relative dose error and the dose linearity were validated with multiple RTPSes and dose calculation algorithms for two groups, namely, CT-RED calibration and CT-MD calibration. The tolerance levels of CT-MD calibration were determined from the tolerance levels of CT-RED calibration with conversion factors. The converted RED from MD was compared with actual RED calculated from ICRP-110. The conversion error was within ±0.01 for most standard organs. It was assumed that the conversion error was sufficiently small. The relative dose error difference for two groups was less than 0.3% for each tissue type. Therefore, the tolerance levels for CT-MD calibration were determined from the tolerance levels of CT-RED calibration with the conversion factors. The MD tolerance levels for lung, adipose/muscle, and cartilage/spongy-bone corresponded to ±0.044, ±0.022, and ±0.045 g/cm3 , respectively. The tolerance levels were useful in terms of approving the CT-MD calibration table for clinical use.


Assuntos
Algoritmos , Imagens de Fantasmas , Fótons/uso terapêutico , Proteção Radiológica , Planejamento da Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Calibragem , Humanos , Processamento de Imagem Assistida por Computador/métodos , Órgãos em Risco/efeitos da radiação , Dosagem Radioterapêutica
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