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1.
Artigo em Japonês | MEDLINE | ID: mdl-32963134

RESUMO

AIM: The aim of this work was to evaluate the coincidence between light and X-ray field width in air. BACKGROUND: Light fields are often used for confirmation of irradiation position to superficial tumors and final confirmation of the patient's irradiation position. To guarantee collation by the light field, the light and X-ray fields must coincide. Currently, the light field width is determined mainly by visual evaluation using manual methods, such as use of graph paper and rulers. The light field width is difficult to visually recognize a definite position at the edge of the light field. MATERIALS AND METHODS: We quantified the width of light fields emitted from a linear accelerator using a light probe detector and compared the results with those of X-ray fields. In-air measurements were conducted at the same position in the light field with the light probe detector and X-ray field using an ionization chamber installed in an emptied three-dimensional water phantom. RESULTS: The radiation field in air was approximately 2 mm larger than the light field, and we found some influence of transmission and scattered rays on the penumbra region. Before and after exchanging crosshair sheets, the fields also exhibited differences in uniformity. CONCLUSIONS: The proposed method quantifies the light field using a photodetector and can be used to compare the light field with the X-ray field, conforming a useful tool for evaluating the accuracy of treatment devices in an objective and systematic manner.


Assuntos
Aceleradores de Partículas , Radiometria , Humanos , Imagens de Fantasmas , Radiografia , Raios X
2.
Zhongguo Yi Liao Qi Xie Za Zhi ; 44(4): 322-327, 2020 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-32762206

RESUMO

This discussion attempts to organize and analyze the clinical purpose of various technologies developed by medical electron accelerators from the development history and clinical needs of radiotherapy products, so as to avoid the troubles caused by specific technical details and summarize the development of medical accelerators. Directly, the study provides differentiated development ideas for the development of domestic medical accelerators and ways and means to determine the dimensions of differentiated development.


Assuntos
Aceleradores de Partículas , Equipamentos de Proteção
3.
PLoS One ; 15(8): e0236570, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32764748

RESUMO

PURPOSE/OBJECTIVES: Recently a 1.5 Tesla MR Linac has been FDA approved and is commercially available. Clinical series describing treatment methods and outcomes for upper abdominal tumors using a 1.5 Tesla MR Linac are lacking. We present the first clinical series of upper abdominal tumors treated using a 1.5 Tesla MR Linac along with the acquisition of intra-treatment quantitative imaging. MATERIALS/METHODS: 10 patients with abdominal tumors were treated at our institution. Each patient enrolled in an IRB approved advanced imaging protocol. Both daily real-time adaptive and non-adaptive methods were used, and selection criteria are described. Adaptive plans were based on pre-beam motion-averaged or mid-position images derived from respiratory-correlated 4D-MRI. Quantitative intravoxel incoherent motion diffusion-weighted imaging and T2 mapping were acquired during plan adaptation. Real-time motion monitoring using cine MRI was performed during beam-on. RESULTS: Median patient age was 68.2, five patients were female. Tumor types included liver metastatic lesions from melanoma and sarcoma, primary liver hepatocellular carcinoma (HCC), and regional abdominal tumors included pancreatic metastatic lesions from renal cell carcinoma (RCC) along with two cases of recurrent pancreatic cancer. Doses included 30 Gy in 6 fractions, 33 Gy in 5 fractions, 50 Gy in 5 fractions, 45 Gy in 3 fractions, and 60 Gy in 3 fractions, depending on the location and clinical circumstances. Treatments were feasible and were successfully completed in all patients without significant acute toxicity, technical complications, or need for back up CT based treatment plans. CONCLUSIONS: We present a first clinical series of patients treated for pancreatic tumors, primary liver tumors, and secondary liver tumors with a 1.5 Tesla MR Linear accelerator using adapt-to-position and adapt-to-shape strategies. Treatments were well tolerated by all patients. Acquisition of fully quantitative MR imaging was feasible during the course of the treatment delivery workflow without extending overall treatment times.


Assuntos
Neoplasias Hepáticas/radioterapia , Metástase Neoplásica/radioterapia , Neoplasias Pancreáticas/radioterapia , Aceleradores de Partículas , Radiocirurgia , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Imagem Cinética por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Planejamento da Radioterapia Assistida por Computador , Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada
4.
PLoS One ; 15(8): e0238106, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32845905

RESUMO

PURPOSE: Real-time monitoring of physiological changes of tumor tissue during radiation therapy (RT) could improve therapeutic efficacy and predict therapeutic outcomes. Cherenkov radiation is a normal byproduct of radiation deposited in tissue. Previous studies in rat tumors have confirmed a correlation between Cherenkov emission spectra and optical measurements of blood-oxygen saturation based on the tissue absorption coefficients. The purpose of this study is to determine if it is feasible to image Cherenkov emissions during radiation therapy in larger human-sized tumors of pet dogs with cancer. We also wished to validate the prior work in rats, to determine if Cherenkov emissions have the potential to act an indicator of blood-oxygen saturation or water-content changes in the tumor tissue-both of which have been correlated with patient prognosis. METHODS: A DoseOptics camera, built to image the low-intensity emission of Cherenkov radiation, was used to measure Cherenkov intensities in a cohort of cancer-bearing pet dogs during clinical irradiation. Tumor type and location varied, as did the radiation fractionation scheme and beam arrangement, each planned according to institutional standard-of-care. Unmodulated radiation was delivered using multiple 6 MV X-ray beams from a clinical linear accelerator. Each dog was treated with a minimum of 16 Gy total, in ≥3 fractions. Each fraction was split into at least three subfractions per gantry angle. During each subfraction, Cherenkov emissions were imaged. RESULTS: We documented significant intra-subfraction differences between the Cherenkov intensities for normal tissue, whole-tumor tissue, tissue at the edge of the tumor and tissue at the center of the tumor (p<0.05). Additionally, intra-subfraction changes suggest that Cherenkov emissions may have captured fluctuating absorption properties within the tumor. CONCLUSION: Here we demonstrate that it is possible to obtain Cherenkov emissions from canine cancers within a fraction of radiotherapy. The entire optical spectrum was obtained which includes the window for imaging changes in water and hemoglobin saturation. This lends credence to the goal of using this method during radiotherapy in human patients and client-owned pets.


Assuntos
Neoplasias/radioterapia , Raios X , Animais , Cães , Processamento de Imagem Assistida por Computador , Neoplasias/diagnóstico por imagem , Aceleradores de Partículas , Projetos Piloto , Estudos Prospectivos , Dosagem Radioterapêutica , Tomografia Computadorizada por Raios X
5.
Br J Radiol ; 93(1114): 20200183, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32795176

RESUMO

The first hospital-based treatment facilities for particle therapy started operation about thirty years ago. Since then, the clinical experience with protons and carbon ions has grown continuously and more than 200,000 patients have been treated to date. The promising clinical results led to a rapidly increasing number of treatment facilities and many new facilities are planned or under construction all over the world. An inverted depth-dose profile combined with potential radiobiological advantages make charged particles a precious tool for the treatment of tumours that are particularly radioresistant or located nearby sensitive structures. A rising number of trials have already confirmed the benefits of particle therapy in selected clinical situations and further improvements in beam delivery, image guidance and treatment planning are expected. This review summarises some physical and biological characteristics of accelerated charged particles and gives some examples of their clinical application. Furthermore, challenges and future perspectives of particle therapy will be discussed.


Assuntos
Medicina de Precisão/tendências , Radioterapia (Especialidade)/tendências , Radioterapia de Alta Energia/tendências , Humanos , Aceleradores de Partículas , Terapia com Prótons , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
6.
Cancer Radiother ; 24(6-7): 730-735, 2020 Oct.
Artigo em Francês | MEDLINE | ID: mdl-32807686

RESUMO

Over the last few years, the radiation therapist profession has undergone major developments. In radiotherapy, the teams, and their organization as well as the techniques have changed, however always with the goal of improving treatment quality for patients. Throughout interviews, this article offers to show three missions that have been assigned to French radiation therapists, such as the initial consultation, the role of the radiation therapist with the linear accelerator with onboard MRI, and paramedical research. The contribution of new technologies, the modification of the types of participants on the patient journey, as well as the thought process about the use of evidence-based practice and radiation therapist research have initiated changes for the job description, the beginning of more advanced practices, and a perspective of evolution within this profession.


Assuntos
Pessoal Técnico de Saúde , Aceleradores de Partículas , Radioterapia (Especialidade) , Humanos
7.
PLoS One ; 15(5): e0232315, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32365071

RESUMO

The INTRABEAM Carl Zeiss Surgical system (Oberkochen, Germany) is a miniature accelerator producing low energy photons (50 keV maximum). The published dosimetric characterization of the INTRABEAM was based on detectors (radiochromic films or ionization chambers) not allowing measuring the absorbed dose in the first millimeters of the irradiated medium, where the dose is actually prescribed. This study aims at determining with Magnetic Resonance Imaging (MRI) the sensitivity of a paramagnetic gel in order to measure the dose deposit produced with the INTRABEAM from 0 to 20 mm. Although spherical applicators are mostly used with the INTRABEAM system for breast applications, this study focuses on surface applicators that are of interest for cutaneous carcinomas. The irradiations at 12 different dose levels (between 2 Gy and 50 Gy at the gel surface) were performed with the INTRABEAM and a 4 cm surface applicator. The gel used in this study is a new « sensitive ¼ material. In order to compare gel sensitivity at low energy with high energy, gels were irradiated by an 18 MV photon beam produced by a Varian Clinac 2100 CD. T2 weighted multi echo MRI sequences were performed with 16 echo times. The T2 signal versus echo times was fitted with a mono-exponential function with 95% confidence interval. The calibration curve determined at low energy is a linear function (r2 = 0.9893) with a sensitivity of 0.0381 s-1.Gy-1, a similar linear function was obtained at high energy (0.0372 s-1.Gy-1 with r2 = 0.9662). The calibration curve at low energy was used to draw isodose maps from the MR images. The PDD (Percent Depth Dose) determined in the gel is within 5%-1mm of the ionization chamber PDD except for one point. The dosimetric sensitivity of this new paramagnetic ferrous gel was determined with MRI measurements. It allowed measuring the dose distribution specifically in the first millimeters for an irradiation with the INTRABEAM miniature accelerator equipped with a surface applicator.


Assuntos
Compostos Ferrosos/química , Radiometria/instrumentação , Géis , Fenômenos Magnéticos , Miniaturização , Aceleradores de Partículas , Doses de Radiação , Razão Sinal-Ruído , Raios X
8.
Zhongguo Yi Liao Qi Xie Za Zhi ; 44(2): 145-153, 2020 Feb 08.
Artigo em Chinês | MEDLINE | ID: mdl-32400989

RESUMO

This discussion attempts to organize and analyze the clinical purpose of various technologies developed by medical electron accelerators from the development history and clinical needs of radiotherapy products, so as to avoid the troubles caused by specific technical details and summarize the development of medical accelerators. Directly, the study provides differentiated development ideas for the development of domestic medical accelerators and ways and means to determine the dimensions of differentiated development.


Assuntos
Aceleradores de Partículas , Radioterapia/instrumentação , Desenho de Equipamento
9.
J Clin Neurosci ; 77: 185-190, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32376156

RESUMO

Previous work at our institution treating arteriovenous malformation (AVM) with radiosurgery (RS) demonstrated superior nidus visualization and geometric accuracy with use of 3-dimensional rotational angiography (3DRA) compared to biplanar digital subtraction angiography. We have since adopted a unique radiosurgical protocol that utilizes 3DRA in the planning of linear accelerator (LINAC)-based RS delivered in a frameless manner. This study seeks to compare clinical outcomes between patients treated by this novel approach and those treated by our historic frame-based protocol. Clinical data were queried for all patients treated for AVM by single-fraction RS from 2003 to 2017. RICs were identified and classified as radiologic, symptomatic, or permanent. Excellent outcome was defined as nidus obliteration without intracranial hemorrhage (ICH) or symptomatic RIC. Clinical predictors of study outcomes were identified through univariate and multivariate logistic regression using backwards elimination to optimize a predictive model. 131 AVMs in 124 patients were included with a median follow-up of 88 months. 59 AVMs received frame-based RS and 72 AVMs received frameless RS. Rate of obliteration was 64% for frame-based RS and 61% for frameless RS (p = 0.70). Radiologic, symptomatic, and permanent RICs rates were 68%, 17%, and 8%, respectively, for frame-based cases, versus 40% (p < 0.01), 8% (p = 0.13), and 3% (p = 0.15), respectively, for frameless cases. Excellent outcome was achieved in 49% of frame-based cases and 53% of frameless cases (p = 0.68). These results illustrate the safety and effectiveness of frameless LINAC-based AVM RS utilizing 3DRA.


Assuntos
Malformações Arteriovenosas Intracranianas/cirurgia , Hemorragias Intracranianas/epidemiologia , Complicações Pós-Operatórias/epidemiologia , Radiocirurgia/métodos , Adolescente , Adulto , Angiografia Digital , Criança , Feminino , Humanos , Malformações Arteriovenosas Intracranianas/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Aceleradores de Partículas , Radiocirurgia/efeitos adversos , Radiocirurgia/instrumentação
10.
Cancer Radiother ; 24(2): 128-134, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32224107

RESUMO

PURPOSE: Shielding disks play an important role in intraoperative electron radiation therapy, and different designs are currently used in clinical practice. This paper investigates the dosimetric impact of the shielding disk used during intraoperative electron radiation therapy (IOERT). MATERIALS AND METHODS: This paper focuses on the study of four shielding disks types that have been used in our clinic: Aluminum (Al)/Lead (Pb), PMMA/Copper(Cu)/PMMA, Aluminum (Al)/Copper (Cu) and Aluminum (Al)/Steel with their specific thicknesses. The theoretical study was conducted with the EGSnrc Monte Carlo (MC) code. On the other hand, the measurements were carried out with gafchromic films for the four shielding disks for the same setup inside the water phantom. Finally, a comparison of the simulated and measured PDD curves was performed for the four material combinations. RESULTS: MC simulation and gafchromic measurements illustrated that dose values under the four shielding disks types were close to 0, whereas the backscattering enhancement of the disks were 103% with Al/Pb shielding disk, 102% with Al/Steel shielding disk, 102% with Al/Cu shielding disk, 95% with PMMA/Cu/PMMA shielding disk. The PDDs values of the gafchromic films in front of the disks were: 107%, 105%, 104%, and 94% for the Al/Pb, Al/Steel, Al/Cu, and PMMA/Cu/PMMA disks respectively. CONCLUSIONS: The dose values above and under the shielding disks were acceptable for the four studied shielding types. Demonstrated it is possible to use any of them clinically, while the best shielding disk was the Al/Pb since it has minimum thickness and a small backscatter enhancement.


Assuntos
Elétrons/uso terapêutico , Cuidados Intraoperatórios/instrumentação , Método de Monte Carlo , Órgãos em Risco , Proteção Radiológica/instrumentação , Ligas , Alumínio , Neoplasias da Mama/radioterapia , Cobre , Desenho de Equipamento , Feminino , Coração , Humanos , Cuidados Intraoperatórios/métodos , Pulmão , Aceleradores de Partículas , Imagens de Fantasmas , Dosagem Radioterapêutica , Costelas , Espalhamento de Radiação , Aço
11.
Phys Med Biol ; 65(11): 115006, 2020 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-32235050

RESUMO

Brain stereotactic radiosurgery (SRS) treatments require multiple quality assurance (QA) procedures to ensure accurate and precise treatment delivery. As single-isocenter multitarget SRS treatments become more popular, the quantification of off-axis accuracy of the linear accelerator is crucial. In this study, a novel brain SRS integrated phantom was developed and validated to enable SRS QA with a single phantom to facilitate implementation of a frameless single-isocenter, multitarget SRS program. This phantom combines the independent verification of each positioning system, the Winston-Lutz, off-axis accuracy evaluation (i.e. off-axis Winston-Lutz), and the dosimetric accuracy utilizing both point dose measurements as well as film measurement, without moving the phantom. A novel 3D printed phantom, coined OneIso, was designed with a movable insert which can switch between the Winston-Lutz test target and dose measurement without moving the phantom itself. For dose verification, ten brain SRS clinical treatment plans with 10 MV flattening-filter-free beams were delivered on a Varian TrueBeam with a high-definition multileaf collimator (HD-MLC). Radiochromic film and pinpoint ion chamber comparison measurements were made between the OneIso and solid water (SW) phantom setups. For the off-axis Winston-Lutz measurements, a row of off-axis ball bearings (BBs) was integrated into the OneIso. To quantify the spatial accuracy versus distance from the isocenter, two-dimensional displacements were calculated between the planned and delivered BB locations relative to their respective MLC defined field border. OneIso and the SW phantoms agree within 1%, for both film and point dose measurements. OneIso identified a reduction in spatial accuracy further away from the isocenter. Differences increased as distance from the isocenter increased, exceeding recommended SRS accuracy tolerances at 7 cm away from the isocenter. OneIso provides a streamlined, single-setup workflow for single-isocenter multitarget frameless linac-based SRS QA. Additionally, with the ability to quantify off-axis spatial discrepancies, we can determine limitations on the maximum distance between targets to ensure a single-isocenter multitarget SRS program meets recommended guidelines.


Assuntos
Imagens de Fantasmas/normas , Garantia da Qualidade dos Cuidados de Saúde/métodos , Radiocirurgia/normas , Algoritmos , Humanos , Aceleradores de Partículas , Impressão Tridimensional , Radiocirurgia/instrumentação , Radiocirurgia/métodos , Dosagem Radioterapêutica
12.
Phys Med Biol ; 65(11): 115002, 2020 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-32235075

RESUMO

Respiratory-gated radiotherapy treatments of lung tumors reduce the irradiated normal tissue volume and potentially lower the risk of side effects. However, in clinical routine, the gating signal is usually derived from external markers or other surrogate signals and may not always correlate well with the actual tumor position. This study uses the kV-imaging system of a LINAC in combination with a multiple template matching algorithm for markerless real-time detection of the tumor position in a dynamic anthropomorphic porcine lung phantom. The tumor was realized by a small container filled with polymer dosimetry gel, the so-called gel tumor. A full end-to-end test for a gated treatment was performed and the geometric and dosimetric accuracy was validated. The accuracy of the tumor detection algorithm in SI- direction was found to be [Formula: see text] mm and the gel tumor was automatically detected in 98 out of 100 images. The measured 3D dose distribution showed a uniform coverage of the gel tumor and comparison with the treatment plan revealed a high 3D [Formula: see text]-passing rate of [Formula: see text] ([Formula: see text]). The simulated treatment confirmed the employed margin sizes for residual motion within the gating window and serves as an end-to-end test for a gated treatment based on a markerless fluoroscopic real-time tumor detection.


Assuntos
Fluoroscopia/métodos , Neoplasias Pulmonares/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Estudos de Viabilidade , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Movimento (Física) , Aceleradores de Partículas , Imagens de Fantasmas , Radiometria/métodos
13.
Igaku Butsuri ; 40(1): 3-7, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32238681

RESUMO

Advances in medical devices have allowed the use of CT, MRI, and PET-CT for the diagnosis of tumors and the detailed evaluation of the extent of lesions. For several decades, CT has been established as the gold standard modality for the treatment planning of radiotherapy, while MRI has emerged as a tool to evaluate the functional characteristics of tumors without radiation exposure. To further optimize precision radiation therapy, we should consider how functional images can be used in the workflow for radiation therapy. In this regard, MRI, as a modality without the need for a contrast agent, may allow more frequent scans and more detailed dose painting, such as increasing the dose to viable lesion parts while reducing the dose to less aggressive parts. Thus, a more personalized treatment based on precision radiation medicine might be realized. In recent years, MR-Linac systems (MRI integrated linear accelerator radiation therapy systems) have been applied in clinical settings by fusing MRI with Linac planning, and further development of radiation therapy utilizing MRI-derived functional images is expected. The use of MR-Linac techniques allows the characteristics of the tumor to be evaluated in more detail before treatment, and the treatment planning can be modified according to the position and characteristics of the tumor (which may change daily during irradiation) to avoid harming normal tissue. Compared with conventional cone beam CT, MR-Linac can offer MR images with much better contrast of soft tissue for image-guided radiation therapy, even when acquired at 0.35 T. A multicenter study of liver tumors using MR-Linac was recently reported. In current tumor imaging, various MRI sequences can be used to evaluate tumor functional information such as tumor heterogeneity, cell density, microenvironment, angiogenesis, necrosis, hypoxic status, and microstructure. In this article, we introduce state-of-the-art acquisition methods for MRI imaging, and discuss how the functional information obtained from these imaging methods can be useful for radiation therapy.


Assuntos
Imagem por Ressonância Magnética , Neoplasias , Radioterapia Guiada por Imagem , Humanos , Neoplasias Hepáticas/diagnóstico por imagem , Aceleradores de Partículas , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons , Planejamento da Radioterapia Assistida por Computador , Microambiente Tumoral
14.
Cancer Radiother ; 24(5): 437-443, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32247689

RESUMO

Radiation therapy has undergone significant advances these last decades, particularly thanks to technical improvements, computer science and a better ability to define the target volumes via morphological and functional imaging breakthroughs. Imaging contributes to all three stages of patient care in radiation oncology: before, during and after treatment. Before the treatment, the choice of optimal imaging type and, if necessary, the adequate functional tracer will allow a better definition of the volume target. During radiation therapy, image-guidance aims at locating the tumour target and tailoring the volume target to anatomical and tumoral variations. Imaging systems are now integrated with conventional accelerators, and newer accelerators have techniques allowing tumour tracking during the irradiation. More recently, MRI-guided systems have been developed, and are already active in a few French centres. Finally, after radiotherapy, imaging plays a major role in most patients' monitoring, and must take into account post-radiation tissue modification specificities. In this review, we will focus on the ongoing projects of nuclear imaging in oncology, and how they can help the radiation oncologist to better treat patients. To this end, a literature review including the terms "Radiotherapy", "Radiation Oncology" and "PET-CT" was performed in August 2019 on Medline and ClinicalTrials.gov. We chose to review successively these novelties organ-by-organ, focusing on the most promising advances. As a conclusion, the help of modern functional imaging thanks to a better definition and new specific radiopharmaceuticals tracers could allow even more precise treatments and enhanced surveillance. Finally, it could provide determinant information to artificial intelligence algorithms in "-omics" models.


Assuntos
Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons/métodos , Radioterapia Guiada por Imagem/métodos , Anticorpos Monoclonais/uso terapêutico , Anticorpos Monoclonais Humanizados/uso terapêutico , Antígenos de Superfície , Antineoplásicos Imunológicos/uso terapêutico , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/radioterapia , Neoplasias Esofágicas/diagnóstico por imagem , Neoplasias Esofágicas/radioterapia , Previsões , Glutamato Carboxipeptidase II , Neoplasias de Cabeça e Pescoço/diagnóstico por imagem , Neoplasias de Cabeça e Pescoço/radioterapia , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/radioterapia , Linfoma/diagnóstico por imagem , Linfoma/radioterapia , Imagem por Ressonância Magnética , Masculino , Aceleradores de Partículas , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Compostos Radiofarmacêuticos , Neoplasias Retais/diagnóstico por imagem , Neoplasias Retais/radioterapia , Sarcoma/diagnóstico por imagem , Sarcoma/radioterapia
15.
Artigo em Japonês | MEDLINE | ID: mdl-32307361

RESUMO

PURPOSE: Novel linac improvements in speed of gantry, collimator, leaf and dose rate may increase the time-efficiency of volumetric modulated arc therapy (VMAT) delivery, however remains to be investigated. In this study, a fast-rotating O-ring linac (Halcyon) with fast moving leaves is compared with a general linac (TrueBeam: TB) in terms of plan quality for VMAT of C-shape, prostate, multi target and, head and neck (H&N) cases from AAPM TG-119. MATERIALS AND METHODS: For the four test cases, VMAT planning was performed using single to four-arc VMAT on a Halcyon and using single to three-arc VMAT on a TrueBeam. Same conditions for optimization were used in each test case. Target coverage metrics and organ at risks (OAR) dose were compared. Monitor unit (MU) and irradiation time in each plan were also compared. RESULTS: In all cases, single-arc plans of Halcyon were inferior to TB plans on dose objectives. Conformity index (CI) to outer target of C-shape case was better for Halcyon (1-arc: 1.242, 2-arc: 1.202, 3-arc: 1.198, 4-arc: 1.181) than for TB (1-arc: 1.247, 2-arc: 1.211, 3-arc: 1.211) except to single arc. D5 (Gy) of core for C-shape case was better for halcyon (1-arc: 23.29, 2-arc: 21.01, 3-arc: 20.64, 4-arc: 20.47) than for TB (1-arc: 24.04, 2-arc: 22.94, 3-arc: 23.04). Calculated MU was smaller for Halcyon than for TB. In addition, Halcyon is more faster than TB because mechanical movements were improved. CONCLUSION: For VMAT plan in each case, Halcyon as well or better at the plan quality of two or three arcs on TB while reducing the delivery time.


Assuntos
Radioterapia de Intensidade Modulada , Masculino , Aceleradores de Partículas , Próstata , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
16.
Artigo em Japonês | MEDLINE | ID: mdl-32307368

RESUMO

Multi-leaf collimator (MLC) parameters, which are registered with radiation treatment planning systems, are very important for intensity modulated radiation therapy (IMRT). In this study, we investigated MLC parameters of respective institutions for efficient commissioning of IMRT. Data of linac models, MLC types, nominal energy, irradiation technique, calculation algorithm, dosimetric leaf gap (DLG) values, and MLC transmission values were collected from each institution in which Varian linac and Eclipse were owned, and analyzed. The numbers of responses from institutions to questionnaire were 15, and the total number of linac was 22. In most institutions, volumetric modulated arc therapy (VMAT) technique was used, and the most used nominal energy was 10 MV. The higher nominal energy was, the higher values of MLC parameters (DLG and MLC transmission) were. In addition, values of MLC parameters of flattening filter free (FFF) beams were smaller than those of flattening filter (FF) beams, even when nominal energy was same. Values of DLG of VMAT tended to be greater than those of multi-field IMRT. These results are expected to be useful for institutions, in which IMRT is implemented.


Assuntos
Radioterapia de Intensidade Modulada , Aceleradores de Partículas , Radiometria , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
17.
Phys Med Biol ; 65(12): 12NT01, 2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32330921

RESUMO

Motion is problematic during radiotherapy as it could lead to potential underdosage of the tumor, and/or overdosage in organs-at-risk. A solution is adaptive radiotherapy guided by magnetic resonance imaging (MRI). MRI allows for imaging of target volumes and organs-at-risk before and during treatment delivery with superb soft tissue contrast in any desired orientation, enabling motion management by means of (real-time) adaptive radiotherapy. The noise navigator, which is independent of the MR signal, could serve as a secondary motion detection method in synergy with MR imaging. The feasibility of respiratory motion detection by means of the noise navigator was demonstrated previously. Furthermore, from electromagnetic simulations we know that the noise navigator is sensitive to tissue displacement and thus could in principle be used for the detection of various types of motion. In this study we demonstrate the detection of various types of motion for three anatomical use cases of MRI-guided radiotherapy, i.e. torso (bulk movement and variable breathing), head-and-neck (swallowing) and cardiac. Furthermore, it is shown that the noise navigator can detect bulk movement, variable breathing and swallowing on a hybrid 1.5 T MRI-linac system. Cardiac activity detection through the noise navigator seems feasible in an MRI-guided radiotherapy setting, but needs further optimization. The noise navigator is a versatile and fast (millisecond temporal resolution) motion detection method independent of MR signal that could serve as an independent verification method to detect the occurrence of motion in synergy with real-time MRI-guided radiotherapy.


Assuntos
Imagem por Ressonância Magnética , Movimentos dos Órgãos , Radioterapia Guiada por Imagem/métodos , Humanos , Órgãos em Risco/efeitos da radiação , Aceleradores de Partículas , Radioterapia Guiada por Imagem/efeitos adversos , Razão Sinal-Ruído
18.
Phys Med Biol ; 65(11): 115001, 2020 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-32191920

RESUMO

Reference dosimetry in the presence of a strong magnetic field is challenging. Ionisation chambers have shown to be strongly affected by magnetic fields. There is a need for robust and stable detectors in MRI-guided radiotherapy (MRIgRT). This study investigates the behaviour of the alanine dosimeter in magnetic fields and assesses its suitability to act as a reference detector in MRIgRT. Alanine pellets were loaded in a waterproof holder, placed in an electromagnet and irradiated by 60Co and 6 MV and 8 MV linac beams over a range of magnetic flux densities. Monte Carlo simulations were performed to calculate the absorbed dose, to water and to alanine, with and without magnetic fields. Combining measurements with simulations, the effect of magnetic fields on alanine response was quantified and a correction factor for the presence of magnetic fields on alanine was determined. This study finds that the response of alanine to ionising radiation is modified when the irradiation is in the presence of a magnetic field. The effect is energy independent and may increase the alanine/electron paramagnetic resonance (EPR) signal by 0.2% at 0.35 T and 0.7% at 1.5 T. In alanine dosimetry for MRIgRT, this effect, if left uncorrected, would lead to an overestimate of dose. Accordingly, a correction factor, [Formula: see text], is defined. Values are obtained for this correction as a function of magnetic flux density, with a standard uncertainty which depends on the magnetic field and is 0.6% or less. The strong magnetic field has a measurable effect on alanine dosimetry. For alanine which is used to measure absorbed dose to water in a strong magnetic field, but which has been calibrated in the absence of a magnetic field, a small correction to the reported dose is required. With the inclusion of this correction, alanine/EPR is a suitable reference dosimeter for measurements in MRIgRT.


Assuntos
Alanina , Campos Magnéticos , Imagem por Ressonância Magnética/métodos , Dosímetros de Radiação/normas , Radioterapia/métodos , Calibragem , Radioisótopos de Cobalto , Método de Monte Carlo , Aceleradores de Partículas , Radiometria/métodos , Radioterapia/instrumentação
19.
Cancer Radiother ; 24(3): 199-205, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32165115

RESUMO

PURPOSE: A high level of accuracy while positioning the patient is mandatory for frameless stereotactic radiotherapy (SRT), as large doses in multiple fractions can be delivered near organs at risk. The objective of this study is to propose an end-to-end quality assurance method to verify that submillimetre alignment can be achieved with stereotactic conventional linacs. METHODS: We used a TrueBeam® linear accelerator equipped with a 6DOF robotic couch. The "ISO Cube" phantom was used with a homemade stand designed to generate known translational and rotational offsets. A reference CT scan was performed with straight alignment of the phantom. The procedure introduced 1.6° angular offset for the couch pitch and roll, at various gantry angles. The couch base was also moved between 0° and 270°. We compared the results with the daily machine performance check tests (MPC, Varian). RESULTS: The mean isocentre size, MV and kV imager offsets were found to agree to within 0.1mm, 0.1mm and 0.3mm respectively, and were in close agreement between the methods. For a total four months data collection period, the mean deviation between requested and measured 6DOF couch shifts was 0.6mm and 0.2°. Errors on field size were smaller than 1mm for 97.7% of the 324 data points. CONCLUSION: Results demonstrate that the linac equipped with a 6DOF robotic positioner and CBCT imaging satisfies requirements for SRT. Our methodology, based on a modified Winston-Lutz quality control, allowed us to quantitatively assess end-to-end accuracy of a linac in order to safely deliver SRT.


Assuntos
Aceleradores de Partículas , Posicionamento do Paciente/métodos , Imagens de Fantasmas , Garantia da Qualidade dos Cuidados de Saúde , Radiocirurgia/métodos , Tomografia Computadorizada de Feixe Cônico/métodos , Desenho de Equipamento , Humanos , Órgãos em Risco , Posicionamento do Paciente/normas , Lesões por Radiação/prevenção & controle , Radiocirurgia/instrumentação , Radiocirurgia/normas , Erros de Configuração em Radioterapia/prevenção & controle , Robótica/instrumentação
20.
Phys Med Biol ; 65(9): 095003, 2020 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-32143198

RESUMO

Previous work has shown that PRESAGE® can be used successfully to perform 3D dosimetric measurements of complex radiotherapy treatments. However, measurements near the sample edges are known to be difficult to achieve. This is an issue when the doses at air-material interfaces are of interest, for example when investigating the electron return effect (ERE) present in treatments delivered by magnetic resonance (MR)-linac systems. To study this effect, a set of 3.5 cm-diameter cylindrical PRESAGE® samples was uniformly irradiated with multiple dose fractions, using either a conventional linac or an MR-linac. The samples were imaged between fractions using an optical-CT, to read out the corresponding accumulated doses. A calibration between TPS-predicted dose and optical-CT pixel value was determined for individual dosimeters as a function of radial distance from the axis of rotation. This data was used to develop a correction that was applied to four additional samples of PRESAGE® of the same formulation, irradiated with 3D-CRT and IMRT treatment plans, to recover significantly improved 3D measurements of dose. An alternative strategy was also tested, in which the outer surface of the sample was physically removed prior to irradiation. Results show that for the formulation studied here, PRESAGE® samples have a central region that responds uniformly and an edge region of 6-7 mm where there is gradual increase in dosimeter response, rising to an over-response of 24%-36% at the outer boundary. This non-uniform dose response increases in both extent and magnitude over time. Both mitigation strategies investigated were successful. In our four exemplar studies, we show how discrepancies at edges are reduced from 13%-37% of the maximum dose to between 2 and 8%. Quantitative analysis shows that the 3D gamma passing rates rise from 90.4, 69.3, 63.7 and 43.6% to 97.3, 99.9, 96.7 and 98.9% respectively.


Assuntos
Imageamento Tridimensional/instrumentação , Neoplasias Pulmonares/radioterapia , Aceleradores de Partículas/instrumentação , Imagens de Fantasmas , Radiometria/instrumentação , Planejamento da Radioterapia Assistida por Computador/métodos , Calibragem , Raios gama , Humanos , Imageamento Tridimensional/métodos , Radiometria/métodos , Dosagem Radioterapêutica , Radioterapia Conformacional/métodos
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