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ilustraciones, fotografías, graficas En este trabajo se estableció un protocolo para la implementación de la irradiación corporal total con electrones, para el cual se requirió la habilitación del modo especial de alta tasa de dosis en un acelerador VARIAN IX, cumpliendo con los requisitos establecidos por VARIAN, el cual exigen una simetría no mayor al 2 % para el inplane y crossplane de los perfiles de dosis en condiciones de referencia (campo de 36 x 36, SSD 100 cm, colimador a 0° y tasa de dosis de 888 UM/min). Así mismo, se logró la caracterización de un haz de electrones de 6 MeV a través de las especificaciones geométricas de la sala de tratamiento del INC, contando con un SSD extendido de 483 cm al punto central del inmovilizador vertical y un campo efectivo de (241 x 241) cm en las diagonales de un campo cuadrado rotado 45 grados, además de la calibración y uso de películas radiocrómicas obteniendo un porcentaje de error relativo de dosis de ± 2 % respecto al sistema de planeación (TPS) en condiciones de referencia (campo de 10 x 10, SSD 100 cm y energía de 6 MeV). Se determinan perfiles de dosis con un buen comportamiento para un campo de 40 x 40, con rotación de colimador a 45°, SSD extendida de 448,6 cm, alta tasa de dosis 888 UM/min y energía de 6 MeV; así como el cumplimiento en las uniformidades de dosis establecidas por la AAPM con una pequeña variación en el crossplane de ± 5, siendo la recomendada por la AAPM como ± 4. Variaciones de dosis en profundidad fueron halladas, logrando cumplir con los criterios establecidos por la EORTC, en la cual sugieren que las superficies de Isodosis entregadas del 80 % y 50 % se encuentren al menos en 4 mm y 5 mm a 15 mm de profundidad respectivamente. Distribuciones de dosis en el plano de tratamiento son presentadas, encontrando zonas con gradientes máximos del 15 % de la dosis prescrita. Por último, se determinó el número de unidades monitor a dar para una sesión de tratamiento de TSEI, teniendo en cuenta la prescripción de dosis y la geometría de irradiación según la técnica Stanford; se encontró que para una prescripción de 1,8 Gy haciendo uso de un solo campo de irradiación deben darse 2450 UM por posición de tratamiento. Una bandeja personalizada, rotada a 45 grados y un panel de PMMA con espesor de 0,6 cm para la degradación del haz y cámaras de ionización fueron usados. Por otra parte, en la sección 4.2, se definieron cada una de las consideraciones a tener en cuenta al momento de posicionar e inmovilizar un paciente apto para la TSEI, teniendo presente poblaciones de pacientes que posean morbilidades como problemas locomotores o patologías graves, obteniendo una práctica difícil en la ubicación del paciente. Asimismo, se debe considerar aquella población que no presenta características (sean patológicas o psiquiátricas) capaces de dar lugar a problemas en el posicionamiento. Dispositivos de inmovilización y de protección adquiridos por el INC fueron considerados. Se inmoviliza un maniquí antropomórfico con el propósito de reproducir las posiciones definidas en la técnica Stanford, reproduciendo 2 de las 6 posiciones (AP y PA) debido a impedimentos físicos del maniquí. Por último, se ejecuta la verificación dosimétrica en la superficie del maniquí mediante el uso de dosímetros TLD, diodos y películas radiocrómicas, encontrando que regiones que cuentan con protuberancias o se encuentren muy cerca al inmovilizador vertical, tienen gradientes de dosis mayores que otras zonas del maniquí; a su vez se concluye que la determinación de impartir un boost local, deberá ser evaluado por el oncólogo radioterápico y físico médico tratante. (Texto tomado de la fuente) In this work, a protocol was established for the implementation of Total Skin Electron Irradiation (TSEI), which required the enabling of the high dose rate special mode on a VARIAN IX accelerator, meeting the requirements established by VARIAN, which demand a symmetry no greater than 2 % for inplane and crossplane dose profiles under reference conditions (field size of 36 x 36, SSD 100 cm, 0° collimator and dose rate of 888 MU/min). Additionally, a 6 MeV electron beam was characterized using the geometric specifications of the treatment room at INC, with an extended SSD of 483 cm to the central point of the vertical immobilizer, and an effective field size of (241 x 241) cm on the diagonals of a rotated 45-degree square field. Calibration and use of radiographic films were also achieved, obtaining a relative dose error percentage of ± 2 % with respect to the planning system (TPS) under reference conditions (field size of 10 x 10, SSD 100 cm, and energy of 6 MeV). Profiles of dose were determined with good behavior for a field of 40 x 40, with collimator rotation at 45°, extended SSD of 448.6 cm, high dose rate of 888 MU/min and energy of 6 MeV; as well as compliance with the dose uniformities established by the AAPM with a small variation in crossplane of ± 5, which is recommended by the AAPM as ± 4. Variations in dose at depth were found, achieving compliance with the criteria established by the EORTC, which suggest that the 80 % and 50 % isodose surfaces delivered be at least 4 mm and 5 mm at 15 mm depth, respectively. Dose distributions in the treatment plane are presented, finding areas with maximum dose gradients of 15 % of the prescribed dose. Finally, the number of monitor units to be given for a TSEI treatment session was determined, taking into account the dose prescription and irradiation geometry according to the Stanford technique; it was found that for a prescription of 1.8 Gy using a single irradiation field, 2450 MU per treatment position should be given. A customized tray, rotated at 45 degrees, and a PMMA panel with a thickness of 0.6 cm for beam degradation and ionization chambers were used. On the other hand, in section 4.2, each of the considerations to be taken into account when positioning and immobilizing a patient suitable for TSEI were defined, taking into account populations of patients with morbidities such as locomotor problems or serious pathologies, obtaining a difficult practice in patient positioning. Likewise, consideration must be given to those populations that do not present characteristics (whether pathological or psychiatric) capable of giving rise to positioning problems. Immobilization and protection devices acquired by the INC were considered. An anthropomorphic mannequin is immobilized with the purpose of reproducing the positions defined in the Stanford technique, reproducing 2 of the 6 positions (AP and PA) due to physical impediments of the mannequin. Finally, dosimetric verification is carried out on the surface of the mannequin using TLD dosimeters, diodes, and radiocrhomic films, finding that regions with protuberances or that are very close to the vertical immobilizer have higher dose gradients than other areas of the mannequin; in turn, it is concluded that the determination to impart a local boost should be evaluated by the treating radiation oncologist and medical physicist. Maestría Magíster en Física Médica Radioterapia

Aim: The objective of this study was to evaluate skin dose based on retrofit prototype multileaf collimators (MLCs), designed for cobalt-60 teletherapy machine. Since patient's skin is sensitive to radiation, evaluation of skin dose is of utmost importance for investigating the risk of late effects. Materials and Methods: Measurements were performed with a Phoenix cobalt-60 teletherapy machine and the detector used was EBT3 radiochromic film. The experiments were performed in a solid water phantom with two prototype MLCs mounted to the machine. Dose readings were taken by placing the films at source-to-surface distance (SSD) of 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, and 90 cm for various MLC-generated field sizes starting from 2 cm × 2 cm to 14 cm × 14 cm. The films were analyzed using custom made programs. The measured doses were normalized to the dose at dmax for that particular measurement of SSD. Results: The skin dose is expressed as a percentage of dose at dose maximum. In general, the skin dose increases with field size and decreases with SSD. The measurements indicate surface doses within 20%–60% for the investigated SSD range. Furthermore, there is no significant difference between the surface doses of two prototype MLCs studied. Conclusions: From the measurements, it can be concluded that there is good skin sparing even at close distance to the MLCs. The skin dose is 65 cm. A minimum gap of 5 cm is required to produce acceptable skin dose.

This work presents the study of the optical density as function of absorbed dose for radiochromic films (model EBT3 Gafchromic) irradiated with protons of energies below 5 MeV. Once the calibration curves are obtained, the study of the optical density as function of the linear energy transfer (LET) is presented. Such studies are useful in proton dosimetry applied to pre-clinical and in vitro radiobiological research. Measurements were performed at the National Centre of Accelerators (CNA) in Seville with a proton beam produced by a 3 MV Tandem accelerator. The incident energy onto the films was measured with an ion implanted silicon detector, and the particle fluence was monitored using a parallel plate ionization chamber. With this proton beam it is possible to investigate the interaction of high LET protons with EBT3 films with narrow energy spreads, as compared with therapeutic proton beams in the Bragg peak region. The data of the beam energy at the position of the film were used to simulate the energy deposition in the active layer of the film, by means of Monte Carlo codes. The measurements were performed for dose values up to 30 Gy and for five values of incident energy, obtained with a passive degradation of the beam by interposing mylar foils of different thickness upstream the EBT3 film. For each energy and corresponding value of proton LET, curves of the optical density as function of the dose are provided for the three color channels red, green and blue (RGB). The dose has been calculated considering two scenarios: dose to water (considering the film composition made by water) and dose to lucite (assuming the real composition of the film). The first corresponds to the case of clinical interest and the second to the real situation of the measurements. The comparison shows a non-negligible shift of the calculated doses even if density corrections are included. In the plateau region of the Bragg curve the film response can be well described by a simple polynomial function (at low doses up to about 4 MeV the response is almost linear). In regions covering the Bragg maximum the film response suffers a quenching and the optical density values were found to be 20–30 % lower than expected., This work is supported by the following research projects: Spanish Ministerio de Ciencia y Competitividad No. FPA2016-77689-C2-1-R and No. FPA2015-67694-P; by the Andalusian Research Projects No. P12-FQM-1605 and No. FQM-0387; and by the European Regional Fund (ERDF).

Proton therapy has gained interest in recent years due to its excellent clinical outcomes. However, the lack of accurate biological data, especially in the Bragg peak region of clinical beams, makes it difficult to implement biophysically optimized treatment plans in clinical practice. In this context, low energy proton accelerator facilities provide the perfect environment to collect good radiobiological data, as they can produce high LET beams with narrow energy distributions. This study presents the radiobiology beam line that has been designed at the 18 MeV proton cyclotron facility at the National Centre of Accelerators (CNA, Seville, Spain), to perform irradiations of mono-layer cell cultures. To ensure that all the cells receive the same dose with a suitable dose rate, low beam intensities and broad and homogeneous beam profiles are necessary. To do so, at the CNA an unfocused beam has been used, broadened with a 500 μm thick aluminium scattering foil. Homogeneous dose profiles, with deviations lower than 10% have been obtained over a circular surface of 35 mm diameter for an incident average energy of 12.8 MeV. Further, a Monte Carlo simulation of the beam line has been developed with Geant4, and benchmarked towards experimental measurements, with differences generally below 1%. Once validated, the code has been used, together with an ionization chamber, for dosimetry studies, to characterize the beam and monitor the dose. Finally, cultures of Human Bone Osteosarcoma cells (U2OS) have been successfully irradiated at the radiobiology beam line, investigating the effects of radiation in terms of DNA damage induction., This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant No. 675265, OMA–Optimization of Medical Accelerators; from the Spanish Plan for Scientific and Technical Research and Innovation under Grant No. FPA2016-77689-C2-1-R, Grant No. RTI2018-098117-B-C21 and Grant No. SAF2016-74855-P; and from the Council for Innovation, Science and Commerce of the Andalusian Government under Grant No. P12-FQM-1605. CABIMER is supported by the regional Government of Andalucia (Junta de Andalucía).

Aim of Study: The aim of this study is to evaluate some dosimetry parameters such as uniformity, surface dose, and max depth dose with thermoluminescent dosimetry (TLD) and EBT3 film in total skin electron beam therapy (TSEBT). Methods: Stationary and rotary methods were set on Varian linear accelerator, Clinac 2100C. To create a radiation field large enough (168 cm × 60 cm) and uniform, the source skin distance was set 400 cm. Electron beam energy was 6 MeV. The skin dose values were obtained in 21 different points on the phantom surface. Results: The results of dose uniformity in stationary technique were obtained as 10% and 2.6% by TLDs and 6% and 2.3% by films in longitudinal axis and transverse axis, respectively. The measurements at rotational technique by TLDs at the referred conditions showed a homogeneous total field with intensity variation of 10% in the longitudinal axis and 4% at horizontal axis. Conclusion: Based on the results of this study, stationary techniques are preferred for TSEBT. The main advantage of rotational techniques is reducing the time of treatment. The results also demonstrate that TLD should be routinely used in TSEBT treatment. Due to the high sensitivity of radiochromic films, this type of film was suitable for a wide therapeutic field. Comprehensive treatment to Rando phantom showed that the uniformity is better at the trunk than in the mobile parts of the body; the soles of the feet, perineum region, and scalp vertex should be treated in boost.

Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT‐XD films have been designed for optimal performance in the 40–4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose‐response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high‐dose volumetric‐modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0–4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter‐free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose‐rate dependence. For clinical examinations, we compared the dose distribution measured with EBT‐XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT‐XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ∼3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ∼1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ∼1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film‐ measured and treatment planning system (TPS)‐calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%. PACS number(s): 87.56 Fc

Gynaecologic malignancies are one of the important cause of mortality and morbidity among women around the world. According to Foundation of women cancer in 2015 it was estimated that over 98 000 women would be diagnosed with a gynaecologic cancer and over 30 000 will die from it. Gynaecological cancer is described as uncontrolled growth and spread of abnormal cells originating in the female reproductive organs and there are five main sources from where cancer could spread including the cervix, ovaries, uterus, fallopian tubes, vagina and vulva and all of them as a group are referred as gynaecologic cancers. Techniques which are used for the treatment depend on various factors such as treatment method, cancer type, shape, location and others. In this Master thesis treatment method using two treatment fields (main and segment) was applied for the treatment of gynaecologic cancer patients. It was aimed to deliver the planned dose to the target (tumour) and to spare ovaries from high doses since ovaries are characterized as being very sensitive to radiation. The main task implementing this method was assessment of dose delivery accuracy performing in vivo and in vitro investigations using radiochromic films and semiconductor diodes. In vitro measurements revealed that the correct positioning of a segment field has a great influence on treatment accuracy since it is related to the maximum dose which is delivered to the gynaecologic cancer patients. Based on in vitro measurements decision was made to check consistency of in vivo dose delivery according to prepared dose treatment plans for real patients. Dosimetry for 7 gynaecologic cancer patients have been performed taking into account dose delivery using two overlapping fields. The results of in vivo measurements have shown, that the relative dose errors varied within the tolerance limits indicating that patient treatment was performed correctly., Ginekologinis vėžys yra viena iš svarbiausių moterų mirtingumo ir sergamumo priežasčių visame pasaulyje. Pagal Foundation of Women cancer 2015 m. buvo nustatyta, jog daugiau nei 98 000 moterų bus diagnozuotos ginekologinis vėžys, o daugiau nei 30 000 moterų mirs dėl šios vėžio formos. Ginekologinis vėžys yra apibūdinamas kaip nekontroliuojamas vėžinių ląstelių augimas moters reprodukcinėje sistemoje, o pagrindiniai jo atsiradimo šaltiniai aptinkami gimdoje, gimdos kaklelyje, kiaušidėse, makštyje ir kiaušintakiuose. Gydimo metodikos kurios yra naudojamos šio tipo vėžiui gydyti priklauso nuo įvairių faktorių tokiu kaip vėžio tipas, forma, vieta ir kt. Šiame magistro baigiamajame darbe buvo pritaikyta dviejų laukų (pagrindinio ir segmentinio) spindulinės terapijos gydimo metodika, kuri buvo skirta ginekologiniu vėžiu sergantiems pacientams. Buvo siekiama apšvitinti planuojamą naviką ir tuo pačių apsaugoti kiaušides nuo didelių dozių, kadangi jos yra charakterizuojamos kaip labai jautrios jonizuojančiajai spinduliuotei. Pagrindinis šio darbo uždavinys, naudojant šią gydimo metodiką, buvo įvertinti dozės tikslumą atliekant in vivo ir in vitro matavimus naudojant puslaidininkinius diodus ir radiochrominius filmus. Atlikti in vitro matavimai parodė, jog teisinga segmentinio lauko padėtis turi didelės įtakos spindulinio gydymo tikslumui, kadangi jis susijęs su maksimalia doze, kuri yra naudojama ginekologiniu vėžiu sergančių pacientų gydime. Remiantis in vitro matavimais, buvo nuspręsta patikrinti in vivo naudojamos dozės patikimumą pagal gydimo planus suplanuotas dozes tikriems pacientams. Buvo atlikti dozimetriniai matavimai su 7 ginekologiniu vėžiu sergančiais pacientais kurių metu buvo vertinama dozės priklausomybė nuo dviejų laukų persidengimo. buvo atlikta atsižvelgiant į dozės pristatymą naudojant du sutampančius laukus. In vivo matavimų rezultatai parodė, kad santykinės dozės paklaidos kito tolerancijos ribose, o tai rodo, kad pacientų spindulinis gydimas buvo atliktas tinkamai.

BACKGROUND: Dose calculations in intraoperative electron radiation therapy (IOERT) rely on the conventional assumption of water-equivalent tissues at the applicator end, which defines a flat irradiation surface. However, the shape of the irradiation surface modifies the dose distribution. Our study explores, for the first time, the use of surface scanning methods for three-dimensional dose calculation of IOERT. METHODS: Two different three-dimensional scanning technologies were evaluated in a simulated IOERT scenario: a tracked conoscopic holography sensor (ConoProbe) and a structured-light three-dimensional scanner (Artec). Dose distributions obtained from computed tomography studies of the surgical field (gold standard) were compared with those calculated under the conventional assumption or from pseudo-computed tomography studies based on surfaces. RESULTS: In the simulated IOERT scenario, the conventional assumption led to an average gamma pass rate of 39.9% for dose values greater than 10% (two configurations, with and without blood in the surgical field). Results improved when considering surfaces in the dose calculation (88.5% for ConoProbe and 92.9% for Artec). CONCLUSIONS: More accurate three-dimensional dose distributions were obtained when considering surfaces in the dose calculation of the simulated surgical field. The structured-light three-dimensional scanner provided the best results in terms of dose distributions. The findings obtained in this specific experimental setup warrant further research on surface scanning in the IOERT context owing to the clinical interest of improving the documentation of the actual IOERT scenario. This study was supported by Ministerio de Ciencia, Innovación y Universidades [grant number TEC2013–48251-C2–1-R]; by Ministerio de Ciencia, Innovación y Universidades, Instituto de Salud Carlos III and European Regional Development Fund (FEDER) Funds from the European Commission, “A way of making Europe” [grant numbers DTS14/00192, PI15/ 02121]; and by Comunidad de Madrid [grant number TOPUS-CM S2013/MIT3024]. The CNIC is supported by the Ministerio de Ciencia, Innovación y Universidades and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Sí

Several tools are used for the dosimetric verification of intensity-modulated arc therapy (IMAT) treatment delivery. However, limited information is available for composite on-line evaluation of these tools. The purpose of this study was to evaluate the dosimetric verification of IMAT treatment plans using a 2D diode array detector (2D array), radiochromic film (RCF) and radiosensitive polymer gel dosimeter (RPGD). The specific verification plans were created for IMAT for two prostate cancer patients by use of the clinical treatment plans. Accordingly, the IMAT deliveries were performed with the 2D array on a gantry-mounting device, RCF in a cylindrical acrylic phantom, and the RPGD in two cylindrical phantoms. After the irradiation, the planar dose distributions from the 2D array and the RCFs, and the 3D dose distributions from the RPGD measurements were compared with the calculated dose distributions using the gamma analysis method (3% dose difference and 3-mm distance-to-agreement criterion), dose-dependent dose difference diagrams, dose difference histograms, and isodose distributions. The gamma passing rates of 2D array, RCFs and RPGD for one patient were 99.5%, 96.5% and 93.7%, respectively; the corresponding values for the second patient were 97.5%, 92.6% and 92.9%. Mean percentage differences between the RPGD measured and calculated doses in 3D volumes containing PTVs were -0.29 ± 7.1% and 0.97 ± 7.6% for the two patients, respectively. In conclusion, IMAT prostate plans can be delivered with high accuracy, although the 3D measurements indicated less satisfactory agreement with the treatment plans, mainly due to the dosimetric inaccuracy in low-dose regions of the RPGD measurements.

OBJETIVO: Verificar a viabilidade de filmes radiocrômicos como um dosímetro alternativo para estimativa da dose média em cortes múltiplos a partir dos perfis de kerma. MATERIAIS E MÉTODOS: Os filmes foram distribuídos em cilindros posicionados no centro e nas regiões periféricas de um objeto simulador padrão de abdome utilizado para dosimetria em tomografia computadorizada. RESULTADOS: Os valores de dose média em cortes múltiplos calculados foram 13,6 ± 0,7, 13,5 ± 0,7 e 18,7 ± 1,0 mGy para os valores de passo (pitch) de 0,75, 1,00 e 1,50, respectivamente. CONCLUSÃO: Apesar de os resultados mostrarem valores menores que o nível de referência de radiodiagnóstico de 25 mGy estabelecido pela legislação brasileira para exames de abdome, eles sugerem que há espaço para otimização dos procedimentos e uma revisão do valor para o nível de referência de radiodiagnóstico brasileiro.OBJECTIVE: To evaluate the feasibility of using radiochromic films as an alternative dosimeter to estimate the multiple scan average dose on the basis on kerma profiles. MATERIALS AND METHODS: The radiochromic films were distributed in cylinders positioned in the center and in four peripheral bores of a standard abdominal phantom utilized for computed tomography dosimetry. RESULTS: Values for multiple scan average dose values corresponded to 13.6 ± 0.7, 13.5 ± 0.7 and 18.7 ± 1.0 mGy for pitch of 0.75, 1.00 and 1.50, respectively. CONCLUSION: In spite of results showing lower values than the reference level for radiodiagnosis (25 mGy) established by the Brazilian regulations for abdominal studies, it is suggested that there is room to optimize procedures and review the reference level for radiodiagnosis in Brazil.

AimThe purpose of the study was to examine the energy dependence of Gafchromic EBT radiochromic dosimetry films, in order to assess their potential use in intensity-modulated radiotherapy (IMRT) verifications.Materials and methodsThe film samples were irradiated with doses from 0.1 to 12Gy using photon beams from the energy range 1.25MeV to 25MV and the film response was measured using a flat-bed scanner. The samples were scanned and the film responses for different beam energies were compared.ResultsA high uncertainty in readout of the film response was observed for samples irradiated with doses lower than 1Gy. The relative difference exceeds 20% for doses lower than 1Gy while for doses over 1Gy the measured film response differs by less than 5% for the whole examined energy range. The achieved uncertainty of the experimental procedure does not reveal any energy dependence of Gafchromic EBT film response in the investigated energy range.ConclusionsGafchromic EBT film does not show any energy dependence in the conditions typical for IMRT but the doses measured for pre-treatment plan verifications should exceed 1Gy.

We present an evaluation of the precision and accuracy of image-based radiochromic film dosimetry. A stack of radiochromic film FWT-60 was used to map a radiation field produced by an electron pulse from a Febetron 707 accelerator (dose rate around 5?1011Gy/s; maximum dose around 160 kGy). The three-dimensional dose distribution was obtained by a He-Nescanning-laser microdensitometer and using image segmentation and correction for non-linear response of films. Calorimetry and electron paramagnetic resonance dosimetry were used to verify the results obtained with a FWT-60 film.

The objective of this study was to investigate the dose enhancement to soft tissue due to backscatter radiation near metal interfaces during head and neck radiotherapy. The influence of titanium-mandibular plate with the screws on radiation dose was tested on four real bones from mandible with the metal and screws fixed. Radiochromic films were used for dosimetry. The bone and metal were inserted through the film at the center symmetrically. This was then placed in a small jig (7 cm × 7 cm × 10 cm) to hold the film vertically straight. The polymer granules (tissue-equivalent) were placed around the film for homogeneous scatter medium. The film was irradiated with 6 MV X-rays for 200 monitor units in Trilogy linear accelerator for 10 cm × 10 cm field size with source to axis distance of 100 cm at 5 cm. A single film was also irradiated without any bone and metal interface for reference data. The absolute dose and the vertical dose profile were measured from the film. There was 10% dose enhancement due to the backscatter radiation just adjacent to the metal-bone interface for all the materials. The extent of the backscatter effect was up to 4 mm. There is significant higher dose enhancement in the soft tissue/skin due to the backscatter radiation from the metallic components in the treatment region.

AimTo present the results obtained using radiochromic films EBT and RTQA 1010P for the reconstruction the dose distributions for targets irradiated by proton beam and modified by wax boluses.BackgroundIn Medico-Technical Complex at the Joint Institute for Nuclear Research in Dubna implemented technology of wax boluses.Materials and methodsWax boluses are easier to make and they give better dose distributions than boluses made from modeling clay previously used at our center. We irradiated two imaginary targets, one shaped as a cylinder and the other one as two cuboids. The evaluated calibration curve was used for calculation of the dose distributions measured by the EBT and RTQA radiochromic film. In both cases, the measured dose distributions were compared to the dose distributions calculated by the treatment planning system (TPS). We also compared dose distributions using three different conformity indices at a 95% isodose.ResultsBetter target coverage and better compliance of measurements (semiconductor detectors and radiochromic films) with calculated doses was obtained for cylindrical target than for cuboidal target. The 95% isodose covered well the tumor for both target shapes, while for cuboidal target larger volume around the target received therapeutic dose, due to the complicated target shape. The use wax boluses provided to be effective tool in modifying proton beam to achieve appropriate shape of isodose distribution.ConclusionEBT film yielded the best visual matching. Both EBT and RTQA films confirmed good conformity between calculated and measured doses, thus confirming that wax boluses used to modify the proton beam resulted in good dose distributions.

OBJETIVO: Verificar a viabilidade de filmes radiocrômicos como um dosímetro alternativo para estimativa da dose média em cortes múltiplos a partir dos perfis de kerma. MATERIAIS E MÉTODOS: Os filmes foram distribuídos em cilindros posicionados no centro e nas regiões periféricas de um objeto simulador padrão de abdome utilizado para dosimetria em tomografia computadorizada. RESULTADOS: Os valores de dose média em cortes múltiplos calculados foram 13,6 ± 0,7, 13,5 ± 0,7 e 18,7 ± 1,0 mGy para os valores de passo (pitch) de 0,75, 1,00 e 1,50, respectivamente. CONCLUSÃO: Apesar de os resultados mostrarem valores menores que o nível de referência de radiodiagnóstico de 25 mGy estabelecido pela legislação brasileira para exames de abdome, eles sugerem que há espaço para otimização dos procedimentos e uma revisão do valor para o nível de referência de radiodiagnóstico brasileiro. OBJECTIVE: To evaluate the feasibility of using radiochromic films as an alternative dosimeter to estimate the multiple scan average dose on the basis on kerma profiles. MATERIALS AND METHODS: The radiochromic films were distributed in cylinders positioned in the center and in four peripheral bores of a standard abdominal phantom utilized for computed tomography dosimetry. RESULTS: Values for multiple scan average dose values corresponded to 13.6 ± 0.7, 13.5 ± 0.7 and 18.7 ± 1.0 mGy for pitch of 0.75, 1.00 and 1.50, respectively. CONCLUSION: In spite of results showing lower values than the reference level for radiodiagnosis (25 mGy) established by the Brazilian regulations for abdominal studies, it is suggested that there is room to optimize procedures and review the reference level for radiodiagnosis in Brazil.

[EN] A gynaecological applicator consisting of a metallic intra-uterine tube with a plastic vaginal applicator and an HDR Ir-192 source have been simulated with MCNP5 (Monte Carlo code). A solid phantom has been designed to perform measurements around the applicator with radiochromic films. The isodose curves obtained are compared with curves calculated with the F4MESH tally of MCNP5 with a good agreement. A pinpoint ionization chamber has been used to evaluate dose at some reference points. (c) 2009 Elsevier Ltd. All rights reserved.

Because of the increase in dose at the end of the range of ions, dose delivery during patient treatment with hadrontherapy should be controlled with high precision. Monte Carlo codes are now considered mandatory for validation of clinical treatment planing and as a new tool for dosimetry of ion beams. In this work, we aimed to calculate the absorbed dose using Monte Carlo simulation Geant4/Gate. The ejffect on the dose calculation accuracy of dierent Geant4 parameters has been studied for mono-energetic carbon ion beams of 300 MeV/u in water. The parameters are : the production threshold of secandary particules and the maximum step limiter of the particle track. Tolerated criterion were choosen to meet the precision required in radiotherapy (2%, 2mm) and to obtain the best compromise on dose distribution and computational time.We propose here the values of parameters in order to satisfy the precision required. In the second part of this work, we will study the response of radiochromic lms MD-v2-55 for quality control in proton and carbon ion beams. We have particularly observed and studie the quenching effect of dosimetric lms for high LET (20 KeV/m) irradiations in homogeneous and heterogeneous medium. This eject is due to the high ionization density around the track of the particule. We have developped a method to predict the response of radiochromic lms taking into account the saturation effect. This model is called the RADIS model forRAdiochromic films. Dosimetry for Ions using Simulations". It is based on the response of lms under photon irradiations and the saturation of lms due to high linear energy deposit calculated by Monte Carlo. Four beams were used in this study and aimed to validate the model for hadrontherapy applications : carbon ions, protons and photons at different energies. Experiments were performed at Grand Accélérateur National d'Ions Lourds (GANIL), Proton therpay center of Orsay (CPO), A. Lacassagne proton center (CAL) and Leon Berard cancer center (CLB). The model showed very good agreement between the measured and calculated optical density with an error less than 2%., En raison des forts gradients de dose générés par les interactions des particules avec la matière, les traitements par hadronthérapie nécessitent un contrôle très précis de la dose délivrée au patient. Les codes Monte Carlo représentent des outils indispensables dans la validation des systèmes de planification de traitement utilisé en clinique. Nous nous intéressons dans cette thèse au calcul de la dose physique à l'aide des simulations Monte Carlo Geant4/Gate. Nous étudions l'ajustement de plusieurs paramètres qui peuvent influencer la précision du calcul de dose requise en clinique (2%, 2mm) pour un faisceau d'ions carbone de 300 MeV/u dans l'eau. Ces paramètres sont : le seuil de production des particules secondaires et la taille maximale d'un segment de la trace de particule. Les critères de tolérance sur la valeur et la localisation de la dose sont fixés de manière à avoir le meilleur compromis en termes de distribution spatiale et de temps de calcul. Nous proposons ici des paramètres permettant d'atteindre ces critères de précision. Dans la deuxième partie du travail, nous étudions la réponse des films radiochromiques MDv2-55 pour le contrôle qualité des faisceaux d'ions carbone et protons. Nous avons en particulier observé et étudié l'effet de saturation de ces films dosimétriques pour les irradiations à TEL élevés (≥ 20 KeV/µm) dans des milieux homogènes et hétérogènes. Cet effet est dû à la forte densité d'ionisation autour de la trace de particule. Nous avons proposé et développé un modèle appelé « RADIS RAdiochromic films Dosimetry for Ions using Simulations » qui permet de prédire la réponse de ces films avec la prise en compte de cet effet de saturation. Ce modèle est basé sur la réponse des films en photons et la saturation des films à des dépôts d'énergies linéïques élevés calculée par Monte Carlo. Plusieurs types de faisceaux ont été étudiés : ions carbone, protons et photons à différentes énergies. Ces expérimentations ont été menées au Grand Accélérateur National d'Ions Lourds (GANIL), au Centre de protonthérapie d'Orsay (CPO), au Centre A. Lacassagne (CAL) et au Centre Léon Bérard (CLB). A l'aide du modèle, nous pouvons ainsi reproduire la densité optique des films le long du profil de Bragg pour tous les faisceaux avec une précision meilleure que 2%.

In radiotherapy one of the biggest problems that arises is the uncertainty in the measurement of the dose absorbed by the tumorous and healthy tissue a dosimeter appropriated for dosimetry measurement are the radiochromic films. This work there as objective dose adsorbed evaluate with radiochromic films GafChromic MD-55-2, which were characterized and calibrated. There was designed the geometry of the ocular implant for then to measure the dose for different positions relative to the axial axis of the applicator. The results will be confirmed with values obtained by the technology TLD and by values given by the System of Planning Prowess 3000 version 3.06. Dosimetry for radiochromic films they reproduce the values of dose obtained by the methods of planning in Prowess and dosimetría TLD with relative minor differences to the 1 % and 6 %, respectively. For it, the radiochromic films turn into a very valuable tool to be able to realize with enough precision and accuracy the dosimetry of ocular brachyterapy. En radioterapia uno de los más grandes problemas que surge es la precisión en la medición de la dosis absorbida por el tejido tumoroso y en el tejido sano, un dosímetro apropiado para la medida de esta dosis es la película radiocrómica. En este trabajo tiene como objetivo evaluar la dosis adsorbida con películas radiocrómicas GafChromic® MD-55-2, las cuales fueron caracterizadas y calibradas. Se diseñó la geometría del implante ocular para luego medir la dosis para diferentes posiciones relativas al eje axial del aplicador. Los resultados son contrastados con valores obtenidos por la técnica TLD y por valores dados por el Sistema de Planificación Prowess 3000 versión 3.06. La dosimetría por películas radiocrómicas reproducen los valores de dosis obtenidos por los métodos de Planificación en Prowess y dosimetría TLD con diferencias menores entre 1 al 6%. Por ello, las películas radiocrómicas se convierten en una herramienta

En radioterapia uno de los más grandes problemas que surge es la precisión en la medición de la dosis absorbida por el tejido tumoroso y en el tejido sano, un dosímetro apropiado para la medida de esta dosis es la película radiocrómica. En este trabajo tiene como objetivo evaluar la dosis adsorbida con películas radiocrómicas GafChromic® MD-55-2, las cuales fueron caracterizadas y calibradas. Se diseñó la geometría del implante ocular para luego medir la dosis para diferentes posiciones relativas al eje axial del aplicador. Los resultados son contrastados con valores obtenidos por la técnica TLD y por valores dados por el Sistema de Planificación Prowess 3000 versión 3.06. La dosimetría por películas radiocrómicas reproducen los valores de dosis obtenidos por los métodos de Planificación en Prowess y dosimetría TLD con diferencias menores entre 1 al 6%. Por ello, las películas radiocrómicas se convierten en una herramienta, In radiotherapy one of the biggest problems that arises is the uncertainty in the measurement of the dose absorbed by the tumorous and healthy tissue a dosimeter appropriated for dosimetry measurement are the radiochromic films. This work there as objective dose adsorbed evaluate with radiochromic films GafChromic MD-55-2, which were characterized and calibrated. There was designed the geometry of the ocular implant for then to measure the dose for different positions relative to the axial axis of the applicator. The results will be confirmed with values obtained by the technology TLD and by values given by the System of Planning Prowess 3000 version 3.06. Dosimetry for radiochromic films they reproduce the values of dose obtained by the methods of planning in Prowess and dosimetría TLD with relative minor differences to the 1 % and 6 %, respectively. For it, the radiochromic films turn into a very valuable tool to be able to realize with enough precision and accuracy the dosimetry of ocular brachyterapy.

This experimental study concerns the characterization of the beams of electrons and protons with energies above a few MeV produced in the interaction of an ultra-intense (~10^19 W.cm-2) laser beam with a 10 µm thick solid target.This work was issued in the framework to use these beams in nuclear physics experiments. It was hence necessary to know quantitatively the characteristics of these particle beams.Laser accelerated particle beams have very different characteristics from conventional accelerators' ones, especially on account of their transience and intensity as well as their continuous energy distribution. These properties make their characterization complex and led us to develop methods combining measurements with diodes spectrometers, radiochromic films, nuclear activation of chosen materials and Monte-Carlo simulations.These methods have been employed on two different facilities (LOA Salle Jaune in Palaiseau and JETI at the IOQ in Jena) but with similar characteristics for the study of the electron beams as a function of the target material. An experiment was also carried out to characterize at each shot the proton beam produced with the LULI 100 TW laser facility (Palaiseau). This experiment also proved the possibility to induce nuclear reactions in plasma and to measure quantitatively the reaction rate in order to scale an experiment on the perturbation of the nucleus electronic-shells coupling via a strong electromagnetic field due to the laser., Cette étude expérimentale concerne la caractérisation des faisceaux d'électrons et de protons d'énergie supérieure à quelques MeV produits lors de l'interaction d'un laser ultra-intense (~10^19 W.cm-2) avec une cible solide de faible épaisseur (10 µm). Ce travail se place dans la perspective de l'utilisation de ces faisceaux pour des expériences de physique nucléaire. Pour cet usage, il est nécessaire de connaître quantitativement les caractéristiques des faisceaux de particules : distribution en énergie, distribution angulaire.Les faisceaux obtenus par accélération laser ont des caractéristiques très différentes des faisceaux d'accélérateurs conventionnels entre autres de par leur brièveté et leur intensité mais aussi par leur distribution en énergie continue. Ces propriétés rendent complexes leur caractérisation et nous ont amenés à développer des méthodes combinant spectromètres à diodes, films radiochromiques, activation nucléaire de matériaux choisis et simulations Monte-Carlo.Ces méthodes ont été utilisées sur deux installations lasers différentes (Salle Jaune au LOA de Palaiseau et JETI à l'IOQ de Jena) mais de caractéristiques proches pour l'étude des faisceaux d'électrons en fonction du matériau-cible. Une expérience a également été menée pour caractériser tir à tir le faisceau de protons produits par le laser 100 TW du LULI (Palaiseau). Cette dernière expérience a, de plus, permis de démontrer la possibilité d'induire des réactions nucléaires dans un plasma et de mesurer quantitativement le taux de réaction en vue d'une expérience de perturbation du couplage noyau-cortège électronique par un champ électromagnétique fort dû au laser.

Despite individual quality assurance (QA) being recommended for complex techniques in radiotherapy (RT) treatment, the possibility of errors in dose delivery during therapeutic application has been verified. Therefore, it is fundamentally important to conduct in vivo QA during treatment. This work presents an in vivo transmission quality control methodology, using radiochromic film (RCF) coupled to the linear accelerator (linac) accessory holder. This QA methodology compares the dose distribution measured by the film in the linac accessory holder with the dose distribution expected by the treatment planning software. The calculated dose distribution is obtained in the coronal and central plane of a phantom with the same dimensions of the acrylic support used for positioning the film but in a source‐to‐detector distance (SDD) of 100 cm, as a result of transferring the IMRT plan in question with all the fields positioned with the gantry vertically, that is, perpendicular to the phantom. To validate this procedure, first of all a Monte Carlo simulation using PENELOPE code was done to evaluate the differences between the dose distributions measured by the film in a SDD of 56.8 cm and 100 cm. After that, several simple dose distribution tests were evaluated using the proposed methodology, and finally a study using IMRT treatments was done. In the Monte Carlo simulation, the mean percentage of points approved in the gamma function comparing the dose distribution acquired in the two SDDs were 99.92%±0.14%. In the simple dose distribution tests, the mean percentage of points approved in the gamma function were 99.85%±0.26% and the mean percentage differences in the normalization point doses were −1.41%. The transmission methodology was approved in 24 of 25 IMRT test irradiations. Based on these results, it can be concluded that the proposed methodology using RCFs can be applied for in vivo QA in RT treatments. PACS number: 87.55.Qr, 87.55.km, 87.55.N‐