Evaluation of monthly variations in electrometer calibration coefficients using a charge generator for radiation therapy.

Electrometers are important devices that are part of the standard dosimetry system. Therefore, we evaluated the variation of electrometer calibration coefficients (kelec) over 1 year in this study. We investigated two types of electrometers: a rate mode and an integrate mode. Each electrometer was connected to a charge generator, a constant charge was applied, and kelec was determined by measuring the current. The current measurements were repeated once a month. For electrometers with multiple ranges, measurements were taken at low and medium ranges. Almost all kelec measurements agreed within 0.2% of the initial measurements. However, the low range of the electrometer with an integrate mode showed seasonal variation, with a variation greater than 0.2%. This study shows that electrometers may exhibit errors that cannot be detected through annual inspections. The importance of quality assurance using a charge generator at one's own institution was demonstrated.

Preclinical photon minibeam radiotherapy using a custom collimator: Dosimetry characterization and preliminary in-vivo results on a glioma model.

PURPOSE: The purpose of this study is to investigate the dosimetric characteristics of a collimator for minibeam radiotherapy (MBRT) with film dosimetry and Monte Carlo (MC) simulations. The outcome of MBRT with respect to conventional RT using a glioma preclinical model was also evaluated. METHODS: A multi-slit collimator was designed to be used with commercial small animal irradiator. The collimator was built by aligning 0.6 mm wide and 5 mm thick parallel lead leaves at 0.4 mm intervals. Dosimetry characteristics were evaluated by Gafchromic (CG) films and TOPAS Monte Carlo (MC) code. An in vivo experiment was performed using a glioma preclinical model by injecting two million GL261cells subcutaneously and treating with 25 Gy, single fraction, with MBRT and conventional RT. Survival curves and acute radiation damage were measured to compare both treatments. RESULTS: A satisfactory agreement between experimental results and MC simulations were obtained, the measured FWHM and distance between the peaks were respectively 0.431 and 1.098 mm. In vivo results show that MBRT can provide local tumor control for three weeks after RT treatment and a similar survival fraction of open beam radiotherapy. No severe acute effects were seen for the MBRT group. CONCLUSIONS: We developed a minibeam collimator and presented its dosimetric features. Satisfactory agreement between MC and GC films was found with differences consistent with uncertainties due to fabrication and set-up errors. The survival curves of MBRT and open field RT are similar while atoxicity is dramatically lower with MBRT, preliminarily confirming the expected effect.

Multi-institutional questionnaire-based survey on online adaptive radiotherapy performed using commercial systems in Japan in 2023.

In this study, we aimed to conduct a survey on the current clinical practice of, staffing for, commissioning of, and staff training for online adaptive radiotherapy (oART) in the institutions that installed commercial oART systems in Japan, and to share the information with institutions that will implement oART systems in future. A web-based questionnaire, containing 107 questions, was distributed to nine institutions in Japan. Data were collected from November to December 2023. Three institutions each with the MRIdian (ViewRay, Oakwood Village, OH, USA), Unity (Elekta AB, Stockholm, Sweden), and Ethos (Varian Medical Systems, Palo Alto, CA, USA) systems completed the questionnaire. One institution (MRIdian) had not performed oART by the response deadline. Each institution had installed only one oART system. Hypofractionation, and moderate hypofractionation or conventional fractionation were employed in the MRIdian/Unity and Ethos systems, respectively. The elapsed time for the oART process was faster with the Ethos than with the other systems. All institutions added additional staff for oART. Commissioning periods differed among the oART systems owing to provision of beam data from the vendors. Chambers used during commissioning measurements differed among the institutions. Institutional training was provided by all nine institutions. To the best of our knowledge, this was the first survey about oART performed using commercial systems in Japan. We believe that this study will provide useful information to institutions that installed, are installing, or are planning to install oART systems.

Dosimetry of microbeam radiotherapy by flexible hydrogenated amorphous silicon detectors.

Objective.Detectors that can provide accurate dosimetry for microbeam radiation therapy (MRT) must possess intrinsic radiation hardness, a high dynamic range, and a micron-scale spatial resolution. In this work we characterize hydrogenated amorphous silicon detectors for MRT dosimetry, presenting a novel combination of flexible, ultra-thin and radiation-hard features.Approach.Two detectors are explored: an n-type/intrinsic/p-type planar diode (NIP) and an NIP with an additional charge selective layer (NIP + CSC).Results.The sensitivity of the NIP + CSC detector was greater than the NIP detector for all measurement conditions. At 1 V and 0 kGy under the 3T Cu-Cu synchrotron broadbeam, the NIP + CSC detector sensitivity of (7.76 ± 0.01) pC cGy-1outperformed the NIP detector sensitivity of (3.55 ± 0.23) pC cGy-1by 219%. The energy dependence of both detectors matches closely to the attenuation coefficient ratio of silicon against water. Radiation damage measurements of both detectors out to 40 kGy revealed a higher radiation tolerance in the NIP detector compared to the NIP + CSC (17.2% and 33.5% degradations, respectively). Percentage depth dose profiles matched the PTW microDiamond detector's performance to within ±6% for all beam filtrations except in 3T Al-Al due to energy dependence. The 3T Cu-Cu microbeam field profile was reconstructed and returned microbeam width and peak-to-peak values of (51 ± 1)µm and (405 ± 5)µm, respectively. The peak-to-valley dose ratio was measured as a function of depth and agrees within error to the values obtained with the PTW microDiamond. X-ray beam induced charge mapping of the detector revealed minimal dose perturbations from extra-cameral materials.Significance.The detectors are comparable to commercially available dosimeters for quality assurance in MRT. With added benefits of being micron-sized and possessing a flexible water-equivalent substrate, these detectors are attractive candidates for quality assurance,in-vivodosimetry and in-line beam monitoring for MRT and FLASH therapy.

Use of a pressure sensor array for multifunctional patient monitoring in radiotherapy: A feasibility study.

BACKGROUND: Modern radiotherapeutic techniques, such as intensity-modulated radiation therapy or stereotactic body radiotherapy, require high-dose delivery precision. However, the precise localization of tumors during patient respiration remains a challenge. Therefore, it is essential to investigate effective methods for monitoring respiration to minimize potential complications. Despite several systems currently in clinical use, there are drawbacks, including the complexity of the setup, the discomfort to the patient, and the high cost. PURPOSE: This study investigated the feasibility of using a novel pressure sensor array (PSA) as a tool to monitor respiration during radiotherapy treatments. The PSA was positioned between the treatment couch and the back of the patient lying on it and was intended to overcome some limitations of current methods. The main objectives included assessing the PSA's capability in monitoring respiratory behavior and to investigate prospective applications that extend beyond respiratory monitoring. METHODS: A PSA with 31 pressure-sensing elements was used in 12 volunteers. The participants were instructed to breathe naturally while lying on a couch without any audio or visual guidance. The performance of the PSA was compared to that of a camera-based respiratory monitoring system (RPM, Varian, USA), which served as a reference. Several metrics, including pressure distribution, weight sensitivity, and correlations between PSA and RPM signals, were analyzed. The PSA's capacity to provide information on potential applications related to patient stability was also investigated. RESULTS: The linear relationship between the weight applied to the PSA and its output was demonstrated in this study, confirming its sensitivity to pressure changes. A comparison of PSA and RPM curves revealed a high correlation coefficient of 0.9391 on average, indicating consistent respiratory cycles. The PSA also effectively measured the weight distribution at the volunteer's back in real-time, which allows for monitoring the patient's movements during the radiotherapy. CONCLUSION: PSA is a promising candidate for effective respiratory monitoring during radiotherapy treatments. Its performance is comparable to the established RPM system, and its additional capabilities suggest its multifaceted utility. This paper shows the potential use of PSA for patient monitoring in radiotherapy and suggests possibilities for further research, including performance comparisons with other existing systems and real-patient applications with respiratory training.

Characterization of selected additive manufacturing materials for synchrotron monochromatic imaging and broad-beam radiotherapy at the Australian synchrotron-imaging and medical beamline.

Objective.This study aims to characterize radiological properties of selected additive manufacturing (AM) materials utilizing both material extrusion and vat photopolymerization technologies. Monochromatic synchrotron x-ray images and synchrotron treatment beam dosimetry were acquired at the hutch 3B and 2B of the Australian Synchrotron-Imaging and Medical Beamline.Approach.Eight energies from 30 keV up to 65 keV were used to acquire the attenuation coefficients of the AM materials. Comparison of theoretical, and experimental attenuation data of AM materials and standard solid water for MV linac was performed. Broad-beam dosimetry experiment through attenuated dose measurement and a Geant4 Monte Carlo simulation were done for the studied materials to investigate its attenuation properties specific for a 4 tesla wiggler field with varying synchrotron radiation beam qualities.Main results.Polylactic acid (PLA) plus matches attenuation coefficients of both soft tissue and brain tissue, while acrylonitrile butadiene styrene, Acrylonitrile styrene acrylate, and Draft resin have close equivalence to adipose tissue. Lastly, PLA, co-polyester plus, thermoplastic polyurethane, and White resins are promising substitute materials for breast tissue. For broad-beam experiment and simulation, many of the studied materials were able to simulate RMI457 Solid Water and bolus within ±10% for the three synchrotron beam qualities. These results are useful in fabricating phantoms for synchrotron and other related medical radiation applications such as orthovoltage treatments.Significance and conclusion.These 3D printing materials were studied as potential substitutes for selected tissues such as breast tissue, adipose tissue, soft-tissue, and brain tissue useful in fabricating 3D printed phantoms for synchrotron imaging, therapy, and orthovoltage applications. Fabricating customizable heterogeneous anthropomorphic phantoms (e.g. breast, head, thorax) and pre-clinical animal phantoms (e.g. rodents, canine) for synchrotron imaging and radiotherapy using AM can be done based on the results of this study.

Pulsed RF knock-out extraction: a potential enabler for FLASH hadrontherapy in the Bragg peak.

One challenge on the path to delivering FLASH-compatible beams with a synchrotron is facilitating an accurate dose control for the required ultra-high dose rates. We propose the use of pulsed RFKO extraction instead of continuous beam delivery as a way to control the dose delivered per Voxel. In a first feasibility test, dose rates in pulses of up to 600 Gy s-1were observed, while the granularity at which the dose was delivered is expected to be well below 0.5 Gy.

Technical note: Visual, rapid, scintillation point dosimetry for in vivo MV photon beam radiotherapy treatments.

BACKGROUND: While careful planning and pre-treatment checks are performed to ensure patient safety during external beam radiation therapy (EBRT), inevitable daily variations mean that in vivo dosimetry (IVD) is the only way to attain the true delivered dose. Several countries outside the US require daily IVD for quality assurance. However, elsewhere, the manual labor and time considerations of traditional in vivo dosimeters may be preventing frequent use of IVD in the clinic. PURPOSE: This study expands upon previous research using plastic scintillator discs for optical dosimetry for electron therapy treatments. We present the characterization of scintillator discs for in vivo x-ray dosimetry and describe additional considerations due to geometric complexities. METHODS: Plastic scintillator discs were coated with reflective white paint on all sides but the front surface. An anti-reflective, matte coating was applied to the transparent face to minimize specular reflection. A time-gated iCMOS camera imaged the discs under various irradiation conditions. In post-processing, background-subtracted images of the scintillators were fit with Gaussian-convolved ellipses to extract several parameters, including integral output, and observation angle. RESULTS: Dose linearity and x-ray energy independence were observed, consistent with ideal characteristics for a dosimeter. Dose measurements exhibited less than 5% variation for incident beam angles between 0° and 75° at the anterior surface and 0-60 ∘ $^\circ $ at the posterior surface for exit beam dosimetry. Varying the angle between the disc surface and the camera lens did not impact the integral output for the same dose up to 55°. Past this point, up to 75°, there is a sharp falloff in response; however, a correction can be used based on the detected width of the disc. The reproducibility of the integral output for a single disc is 2%, and combined with variations from the gantry angle, we report the accuracy of the proposed scintillator disc dosimeters as ±5.4%. CONCLUSIONS: Plastic scintillator discs have characteristics that are well-suited for in vivo optical dosimetry for x-ray radiotherapy treatments. Unlike typical point dosimeters, there is no inherent readout time delay, and an optical recording of the measurement is saved after treatment for future reference. While several factors influence the integral output for the same dose, they have been quantified here and may be corrected in post-processing.

A comprehensive investigation of the performance of a commercial scintillator system for applications in electron FLASH radiotherapy.

BACKGROUND: Dosimetry in ultra-high dose rate (UHDR) beamlines is significantly challenged by limitations in real-time monitoring and accurate measurement of beam output, beam parameters, and delivered doses using conventional radiation detectors, which exhibit dependencies in ultra-high dose-rate (UHDR) and high dose-per-pulse (DPP) beamline conditions. PURPOSE: In this study, we characterized the response of the Exradin W2 plastic scintillator (Standard Imaging, Inc.), a water-equivalent detector that provides measurements with a time resolution of 100 Hz, to determine its feasibility for use in UHDR electron beamlines. METHODS: The W2 scintillator was exposed to an UHDR electron beam with different beam parameters by varying the pulse repetition frequency (PRF), pulse width (PW), and pulse amplitude settings of an electron UHDR linear accelerator system. The response of the W2 scintillator was evaluated as a function of the total integrated dose delivered, DPP, and mean and instantaneous dose rate. To account for detector radiation damage, the signal sensitivity (pC/Gy) of the W2 scintillator was measured and tracked as a function of dose history. RESULTS: The W2 scintillator demonstrated mean dose rate independence and linearity as a function of integrated dose and DPP for DPP ≤ 1.5 Gy (R2 > 0.99) and PRF ≤ 90 Hz. At DPP > 1.5 Gy, nonlinear behavior and signal saturation in the blue and green signals as a function of DPP, PRF, and integrated dose became apparent. In the absence of Cerenkov correction, the W2 scintillator exhibited PW dependence, even at DPP values <1.5 Gy, with a difference of up to 31% and 54% in the measured blue and green signal for PWs ranging from 0.5 to 3.6 µs. The change in signal sensitivity of the W2 scintillator as a function of accumulated dose was approximately 4%/kGy and 0.3%/kGy for the measured blue and green signal responses, respectively, as a function of integrated dose history. CONCLUSION: The Exradin W2 scintillator can provide output measurements that are both dose rate independent and linear in response if the DPP is kept ≤1.5 Gy (corresponding to a mean dose rate up to 290 Gy/s in the used system), as long as proper calibration is performed to account for PW and changes in signal sensitivity as a function of accumulated dose. For DPP > 1.5 Gy, the W2 scintillator's response becomes nonlinear, likely due to limitations in the electrometer related to the high signal intensity.

3D-printed boluses for radiotherapy: influence of geometrical and printing parameters on dosimetric characterization and air gap evaluation.

The work investigates the implementation of personalized radiotherapy boluses by means of additive manufacturing technologies. Boluses materials that are currently used need an excessive amount of human intervention which leads to reduced repeatability in terms of dosimetry. Additive manufacturing can solve this problem by eliminating the human factor in the process of fabrication. Planar boluses with fixed geometry and personalized boluses printed starting from a computed tomography scan of a radiotherapy phantom were produced. First, a dosimetric characterization study on planar bolus designs to quantify the effects of print parameters such as infill density and geometry on the radiation beam was made. Secondly, a volumetric quantification of air gap between the bolus and the skin of the patient as well as dosimetric analyses were performed. The optimization process according to the obtained dosimetric and airgap results allowed us to find a combination of parameters to have the 3D-printed bolus performing similarly to that in conventional use. These preliminary results confirm those in the relevant literature, with 3D-printed boluses showing a dosimetric performance similar to conventional boluses with the additional advantage of being perfectly conformed to the patient geometry.

Multi-point calorimeter using distributed fiber Bragg gratings for small field dosimetry in radiotherapy.

BACKGROUND: The interest of using fiber Bragg gratings (FBGs) dosimeters in radiotherapy (RT) lies in their (i) microliter detection volume, (ii) customizable spatial resolution, (iii) multi-point dose measurement, (iv) real-time data acquisition and (v) insensitivity to Cherenkov light. These characteristics could prove very useful for characterizing dose distributions of small and nonstandard fields with high spatial resolution. PURPOSE: We developed a multi-point FBGs dosimeter customized for small field RT dosimetry with a spatial resolution of ∼ $\sim$ 1 mm. METHODS: The 3 cm-long multi-point dosimeter is made by embedding a 80 µ m $\umu{\rm {m}}$ silica fiber containing an array of thirty (30) co-located ∼ $\sim$ 1 mm-long fs-written FBGs inside a plastic cylinder with an UV curing optical adhesive. With its higher thermal expansion coefficient, the plastic cylinder increases the sensitivity of the dosimeter by stretching the fiber containing the FBGs when the temperature rises slightly due to radiation energy deposition. Irradiations (2000 MU at 600 MU/min) were performed with a Varian TrueBeam linear accelerator. RESULTS: The dose profile of a 2  × $ \times$ 2 cm 2 $^{2}$ 6 MV beam was measured with a mean relative difference of 1.8% (excluding the penumbra region). The measured output factors for a 6 MV beam are in general agreement with the expected values within the experimental uncertainty (except for the 2  × $\,\times $ 2 cm 2 $^{2}$ field). The detector response to different energy of photon and electron beams is within 5% of the mean response ( 0.068 ± 0.002 $0.068\pm 0.002$  pm/Gy). The calorimeter's post-irradiation thermal decay is in agreement with the theory. CONCLUSIONS: An energy-independent small field calorimeter that allows dose profile and output factor measurements for RT using FBGs was developed, which, to our knowledge, has never been done before. This type of detector could prove really useful for small field dosimetry, but also potentially for MRI-LINAC since FBGs are insensitive to magnetic fields and for FLASH since FBGs have been used to measure doses up to 100 kGy.

NTCP Calculations of Five Different Irradiation Techniques for the Treatment of Thymoma.

This study provided normal tissue complication probability (NTCP) calculations from photon radiotherapy techniques in eleven patients with thymoma. Five plans were created for each participant using three-dimensional conformal radiotherapy (3D-CRT), five-field intensity modulated radiotherapy (5F-IMRT), seven-field IMRT (7F-IMRT), and volumetric modulated arc therapy with full arcs (FA-VMAT) and partial arcs (PA-VMAT). The target coverage, homogeneity index and conformation number for the planning target volume (PTV) and dosimetric parameters for the organs-at-risk (OARs) were taken from the fifty-five generated plans. The patient-specific NTCP of the lungs, heart and esophagus was calculated with an in-house software tool using differential dose-volume histograms and the equivalent uniform dose model. The PTV dose metrics from 3D-CRT were inferior to those from IMRT and VMAT plans. The dose constraints for the OARs were met in all treatment plans. The NTCP range of the lungs, heart and esophagus was 0.34-0.49%, 0.03-0.06% and 0.08-0.10%, respectively. The NTCPs of the heart for the incidence of peridarditis from IMRT and VMAT were significantly smaller than those from conformal treatment (p < 0.05). The 7F-IMRT was significantly superior to FA-VMAT in reducing the NTCP of the lungs and the risk of pneumonitis (p = 0.001). Similar superiority of 5F-IMRT over PA-VMAT for lung protection was found (p = 0.009). The presented results may be employed in the selection of the appropriate irradiation technique for restricting the complications in the adjacent OARs.

Radiotherapy Infrastructure Shielding Calculations: software development for shielding calculations in a linear accelerator radiotherapy room.

This work aimed to develop and validate software that calculates the shielding thickness required for a radiotherapy room with a linear accelerator utilising geometric and dosimetric data. The software "Radiotherapy Infrastructure Shielding Calculations" (RISC) was developed using MATLAB programming. It does not require the installation of the MATLAB platform, and the user only needs to download and install the application, which displays a graphical user interface (GUI). The GUI includes empty cells to insert numerical values for several parameters to calculate the proper shielding thickness. The GUI comprises two main interfaces, one for the primary and one for the secondary barrier calculation. The interface of the primary barrier is divided into four tabs: (a) primary radiation, (b) patient scattered and leakage radiation, (c) IMRT techniques and (d) the shielding cost calculations. The interface of the secondary barrier includes three tabs: (a) patient scattered and leakage radiation, (b) IMRT techniques and (c) the shielding cost calculations. Each tab consists of two sections: one for input and one for output of the necessary data. The RISC is based on the methods and formulae of the NCRP 151 and calculates the primary and secondary barrier thickness for ordinary concrete with a density of 2.35 g/cm3 and the cost for a radiotherapy room with a linear accelerator that performs conventional or IMRT techniques. Calculations can be performed for photon energies of 4, 6, 10, 15, 18, 20, 25 and 30 MV of a dual-energy linear accelerator, while instantaneous dose rate (IDR) calculations are also performed. The RISC has been validated using all comparative examples of NCRP 151 and the calculations from shielding reports of the Varian IX linear accelerator at Methodist Hospital of Willowbrook and Elekta Infinity at the University Hospital of Patras. The RISC is accompanied by two text files: (a) "Terminology," extensively describing all parameters, and (b) "User's Manual," providing useful instructions to the user. The RISC is user-friendly, simple, fast and precise, providing accurate shielding calculations and quickly and easily reproducing different shielding scenarios for a radiotherapy room with a linear accelerator. Additionally, it could be used during the educational process of shielding calculations by graduate students or trainee medical physicists. As a future work, the RISC will be updated with new features such as skyshine radiation, door shielding, and other types of machines and shielding materials.

O odontólogo frente aos cuidados paliativos na oncologia / The dental surgeon facing palliative care in oncology: a literature review / El odontólogo ante los cuidados paliativos en oncología

Cuidados paliativos são um conjunto de procedimentos ofertados ao paciente por uma equipe multidisciplinar com objetivo de garantir bem-estar, autonomia,conforto e alívio de sintomas decorrentes de doença ou tratamento quando a cura é impossibilitada. O câncer representa uma das doenças que possuem chances de evoluir o paciente ao estágio terminal, momento em que cuidados paliativos são indicados e necessários. Dentro da equipe responsável, o cirurgião-dentista atua na prevenção, diagnóstico e tratamento de lesões expressas no sistema estomatognático que se manifestam estimuladas pelo câncer ou pelos tratamentos utilizados. O objetivo desta pesquisa é destacar a função do odontólogo dentro da equipe multidisciplinar paliativista para pacientes oncológicos. Trata-se de uma revisão bibliográfica sistemáticada literatura. Foram feitas buscas nas plataformas Biblioteca Virtual em Saúde (BVS) e Scientific Electronic Library Online (SciELO) e após aplicação dos critérios de inclusão e exclusão foram selecionados 14 artigos. A literatura evidencia que alterações orais estão relacionadas com o curso da neoplasia ou seu tratamento; as lesões mais descritas foram: mucosite, xerostomia, candidíase, cárie, periodontite e osteorradionecrose. Isso faz com que o paciente sofra limitações em realizar atividades básicas, alterando negativamente a sua qualidade de vida. A complexidade da manifestação oral pode interromper o tratamento antineoplásico. As medidas de enfrentamento mais empregadas para a saúde bucal do paciente oncológico são a laserterapia, bochechos com clorexidina 0,12%, instrução de higiene oral, uso de anti-inflamatórios, analgésicos e antifúngicos. A atuação do odontólogo na equipe multidisciplinar oncológica paliativista é indispensável para o controle das manifestações orais.

Palliative care comprises a set of procedures offered by a multidisciplinary team to patients who cannot be cured, aiming to restore and ensure well-being, autonomy, independence, comfort and relief from symptoms resulting from illness or treatments. Cancer commonly leads the patient to the terminal stage, and at this stage palliative care is indicated and necessary. Composing the multidisciplinary team, the dentist works in the prevention, diagnosis and treatment of injuries that arise in the stomatognathic system, which manifest themselves due to cancer or its treatments. The objective of this research was to highlight the work of the dentist in the multidisciplinary team of palliative care for cancer patients. This is a systematic bibliographic review of the literature, with an integrative character. Study searches were performed in the Virtual Health Library (VHL) and Scientific Electronic Library Online (SciELO). After applying the inclusion and exclusion criteria, 14 articles were selected. Results showed that oral alterations are completely related to the development of the neoplasm or its treatment; the most described lesions were: mucositis, xerostomia, candidiasis, osteoradionecrosis, radiation caries and periodontitis. These injuries make the patient suffer limitations to perform basic activities, such as eating or communicating, negatively altering their quality of life. The complexity of the oral manifestation can determine the interruption of the anticancer treatment. The most used coping measures for the oral healthof cancer patients are: low- potency laser therapy, mouthwash with 0.12% chlorhexidine, instructionin oral hygiene and use of anti-inflammatory, analgesic and antifungal drugs. The role of dentists in the multidisciplinary palliative oncology team is essential for the control of oral lesions.

Los cuidados paliativos son un conjunto de procedimientos ofrecidos al paciente por un equipo multidisciplinar con el objetivo de garantizar el bienestar, la autonomía, el confort y el alivio de los síntomas derivados de la enfermedad o del tratamiento cuando la curación es imposible. El cáncer representa una de las enfermedades que tienen posibilidades de evolucionar al paciente hasta la fase terminal, momento en el que los cuidados paliativos son indicados y necesarios. Dentro del equipo responsable, el cirujano dentista actúa en la prevención, diagnóstico y tratamiento de las lesiones expresadas en el sistema estomatognático que se manifiestan estimuladas por el cáncer o por los tratamientos utilizados. El objetivo de esta investigación es destacar la función del odontólogo dentro del equipo paliativo multidisciplinar para pacientes oncológicos. Se trata de una revisión bibliográfica sistemática. Se realizaron búsquedas en las plataformas Virtual Health Library (BVS) y Scientific Electronic Library Online (SciELO) y tras aplicar los criterios de inclusión y exclusión, se seleccionaron 14 artículos. La literatura muestra que las alteraciones orales están relacionadas con el curso del cáncer o su tratamiento; las lesiones más comúnmente descritas fueron: mucositis, xerostomía, candidiasis, caries, periodontitis y osteorradionecrosis. Esto hace que el paciente sufra limitaciones para realizar actividades básicas, alterando negativamente su calidad de vida. La complejidad de la manifestación oral puede interrumpir el tratamiento antineoplásico. Las medidas de afrontamiento más utilizadas para la salud bucodental de los pacientes con cáncer son la terapia láser, los enjuagues bucales con clorhexidina al 0,12%, las instrucciones de higiene bucodental y el uso de fármacos antiinflamatorios, analgésicos y antifúngicos. La actuación del odontólogo en el equipo multidisciplinar de oncología paliativa es fundamental para el control de las manifestaciones orales.

Modelling a new approach for radio-ablation after resection of breast ductal carcinoma in-situ based on the BAT-90 medical device.

The majority of local recurrences, after conservative surgery of breast cancer, occurs in the same anatomical area where the tumour was originally located. For the treatment of ductal carcinoma in situ (DCIS), a new medical device, named BAT-90, (BetaGlue Technologies SpA) has been proposed. BAT-90 is based on the administration of 90Y ß-emitting microspheres, embedded in a bio-compatible matrix. In this work, the Geant4 simulation toolkit is used to simulate BAT-90 as a homogenous cylindrical 90Y layer placed in the middle of a bulk material. The activity needed to deliver a 20 Gy isodose at a given distance z from the BAT-90 layer is calculated for different device thicknesses, tumour bed sizes and for water and adipose bulk materials. A radiobiological analysis has been performed using both the Poisson and logistic Tumour Control Probability (TCP) models. A range of radiobiological parameters (α and ß), target sizes, and densities of tumour cells were considered. Increasing α values, TCP increases too, while, for a fixed α value, TCP decreases as a function of clonogenic cell density. The models predict very solid results in case of limited tumour burden while the activity/dose ratio could be further optimized in case of larger tumour beds.

Estimativa da necessidade de radioterapia externa no Brasil baseada em critérios epidemiológicos / Optimal utilization of radiotherapy in Brazil according to local epidemiological data

Esta tese teve como objetivo estimar a necessidade de radioterapia no Brasil a partir de dados epidemiológicos locais. O estudo foi desenvolvido em duas etapas que consistiram na estimativa de casos incidentes e, posteriormente, na classificação dos casos registrados nos Registros Hospitalares de Câncer (RHC) para integrar as árvores de decisão para o emprego do tratamento radioterápico conforme evidências e diretrizes clínicas de tratamento. As estimativas de casos incidentes em 2018 foram calculadas a partir de dados de Registros de Câncer de Base Populacional (RCBP) selecionados de acordo com critérios internacionais de qualidade e de dados corrigidos para causas mal definidas e não específicas na causa básica dos óbitos registrados no Sistema de Informação de Mortalidade (SIM) no período de 2007 a 2016. Foram calculadas razões de incidência/mortalidade (I/M) anuais para cada topografia, estratificadas por sexo e faixa etária nos RCBP selecionados. As razões I/M para 2018 foram estimadas para as regiões brasileiras a partir de modelos multiníveis de Poisson a partir de uma abordagem longitudinal com efeito aleatório no RCBP. As razões estimadas foram aplicadas ao número de óbitos ocorridos em 2018 por tipo de câncer, também corrigido para causas mal definidas e não específicas na causa básica, registrados no SIM. As distribuições dos dados por estadiamento obtidas a partir do RHC foram combinadas às frequências relativas por tipo de câncer incidente e aos dados das árvores de decisão do projeto Collaboration for Cancer Outcomes Research and Evaluation (CCORE) para uso da radioterapia. As estimativas de necessidade foram calculadas por tipo de câncer e para o conjunto das neoplasias, exceto pele não melanoma. Foram realizadas análises de sensibilidade para avaliar a relevância dos dados locais na estimativa de necessidade. O número necessário de equipamentos de radioterapia para atender os casos que se beneficiariam do tratamento em algum momento no curso da doença foi calculado e a análise da cobertura da oferta foi realizada. Para o Brasil, em 2018, foram estimados 506.462 casos novos de câncer, exceto pele não melanoma. Diferenças regionais nas razões I/M e no padrão de casos incidentes foram identificadas, podendo estar relacionadas a fatores socioeconômicos. Foi estimado que 53,55% dos casos novos no Brasil teriam necessidade de tratamento radioterápico. A maior necessidade de radioterapia foi identificada para o Norte: 55,32%, com um peso expressivo do câncer do colo do útero, tanto pela incidência como pelo número de casos em estágios avançados, para os quais a radioterapia é considerada tratamento de escolha. Para atender aos casos com necessidade de radioterapia no Brasil, foram estimados 497 equipamentos de radioterapia externa, sendo o déficit estimado em 114 para 2018 no país. Os maiores déficits foram observados para o Norte e para a rede assistencial do SUS. Em conclusão, o emprego de parâmetros internacionais não se mostrou adequado para a realidade brasileira. O planejamento de recursos para a assistência oncológica no Brasil demanda estimativas confiáveis baseadas nas necessidades locais para que as inequidades não sejam ainda mais agravadas.

This thesis aimed to estimate the need for radiotherapy in Brazil based on local epidemiological data. The study was developed in two stages which consisted of estimating incident cases and, later, classifying the cases registered in the Hospital Cancer Registries (RHC) to integrate decision trees for the use of radiotherapy according to evidence and clinical treatment guidelines. The estimates of incident cases in 2018 were calculated based on data from Population-Based Cancer Registries (RCBP) selected according to international quality criteria and from data corrected for ill-defined and non-specific causes in the underlying cause of deaths recorded in the System of Mortality Information (SIM) from 2007 to 2016. Annual incidence/mortality ratios (I/M) were calculated for each topography, stratified by sex and age group in the selected RCBP. The I/M ratios for 2018 were estimated for Brazilian regions using multilevel Poisson models from a longitudinal approach with random effect on the RCBP. The estimated reasons were applied to the number of deaths that occurred in 2018 by type of cancer, also corrected for ill-defined and non-specific causes in the underlying cause, recorded in the SIM. The staging data distributions obtained from the RHC were combined with the relative frequencies by type of incident cancer and data from the Collaboration for Cancer Outcomes Research and Evaluation (CCORE) project decision trees for radiotherapy use. Optimal utilization rates were estimated by type of cancer and for the set of tumors, except for non-melanoma skin. Sensitivity analyzes were performed to assess the relevance of local data in estimating the need. The number of radiotherapy equipment needed to attend to cases that would benefit from treatment at some point in the course of the disease was calculated and the analysis of the offer coverage was performed. For Brazil, in 2018, 506,462 new cases of cancer were estimated, except for non-melanoma skin. Regional differences in I/M ratios and in the pattern of incident cases were identified, which may be related to socioeconomic factors. It was estimated that 53.55% of new cases in Brazil would need radiotherapy. The greatest need for radiotherapy was identified for the North: 55.32%, with an expressive weight of cervical cancer, both in terms of incidence and the number of cases in advanced stages, for which radiotherapy is considered the treatment of choice. To meet the need for radiotherapy in Brazil, 497 external radiotherapy equipment were estimated, with an estimated deficit of 114 for 2018 in the country. The greatest deficits were observed for the North and for the SUS care network. In conclusion, the use of international parameters was not adequate for the Brazilian reality. The planning of resources for cancer care in Brazil requires reliable estimates based on local needs so that inequities are not further aggravated.

Theranostic near-infrared-IIb emitting nanoprobes for promoting immunogenic radiotherapy and abscopal effects against cancer metastasis.

Radiotherapy is an important therapeutic strategy for cancer treatment through direct damage to cancer cells and augmentation of antitumor immune responses. However, the efficacy of radiotherapy is limited by hypoxia-mediated radioresistance and immunosuppression in tumor microenvironment. Here, we construct a stabilized theranostic nanoprobe based on quantum dots emitting in the near-infrared IIb (NIR-IIb, 1,500-1,700 nm) window modified by catalase, arginine-glycine-aspartate peptides and poly(ethylene glycol). We demonstrate that the nanoprobes effectively aggregate in the tumor site to locate the tumor region, thereby realizing precision radiotherapy with few side-effects. In addition, nanoprobes relieve intratumoral hypoxia and reduce the tumor infiltration of immunosuppressive cells. Moreover, the nanoprobes promote the immunogenic cell death of cancer cells to trigger the activation of dendritic cells and enhance T cell-mediated antitumor immunity to inhibit tumor metastasis. Collectively, the nanoprobe-mediated immunogenic radiotherapy can boost the abscopal effect to inhibit tumor metastasis and prolong survival.

Development of a new poly-ε-caprolactone with low melting point for creating a thermoset mask used in radiation therapy.

This study aimed to develop a poly-ε-caprolactone (PCL) material that has a low melting point while maintaining the deformation ability. The new PCL (abbreviated as 4b45/2b20) was fabricated by mixing two types of PCL with different molecular weights, numbers of branches, and physical properties. To investigate the melting point, crystallization temperature, elastic modulus, and elongation at break for 4b45/2b20 and three commercially available masks, differential scanning calorimetry and tensile tests were performed. The melting point of 4b45/2b20 was 46.0 °C, and that of the commercially available masks was approximately 56.0 °C (55.7 °C-56.5 °C). The elastic modulus at 60 °C of 4b45/2b20 was significantly lower than the commercially available masks (1.1 ± 0.3 MPa and 46.3 ± 5.4 MPa, p = 0.0357). In addition, the elongation at break of 4b45/2b20 were significantly larger than the commercially available masks (275.2 ± 25.0% and 216.0 ± 15.2%, p = 0.0347). The crystallization temperature of 4b45/2b20 (22.1 °C) was clinically acceptable and no significant difference was found in the elastic modulus at 23 °C (253.7 ± 24.3 MPa and 282.0 ± 44.3 MPa, p = 0.4). As a shape memory-based thermoset material, 4b45/2b20 has a low melting point and large deformation ability. In addition, the crystallization temperature and strength are within the clinically acceptable standards. Because masks made using the new PCL material are formed with less pressure on the face than commercially available masks, it is a promising material for making a radiotherapy mask that can reduce the burden on patients.