Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 12.625
Filtrar
1.
PLoS One ; 15(12): e0234829, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33270667

RESUMO

BACKGROUND: This study investigated the effect of accumulated doses on radio-photoluminescence glass dosimeters (RPLGDs) from measurements involving mega-voltage photons. METHODS: Forty-five commercially available RPLGDs were irradiated to estimate their dose responses. Photon beams of 6, 10, and 15 MV were irradiated onto the RPLGDs inside a phantom, which were divided into five groups with different doses and energies. Groups 1 and 2 were irradiated at 1, 5, 10, 50, and 100 Gy in a sequential manner; Group 3 was irradiated 10 times with a dose of 10 Gy; and Groups 4 and 5 followed the same method as that of Group 3, but with doses of 50 Gy and 100 Gy, respectively. Each device was subjected to a measurement reading procedure each time irradiation. RESULTS: For the annealed Group 1, RPLGD exhibited a linearity response with variance within 5%. For the non-annealed Group 2, readings demonstrated hyperlinearity at 6 MV and 10 MV, and linearity at 15 MV. Following the 100 Gy irradiation, the readings for Group 2 were 118.7 ± 1.9%, 112.2 ± 2.7%, and 101.5 ± 2.3% at 6, 10, and 15 MV, respectively. For Groups 3, 4, and 5, the responsiveness of the RPLGDs gradually decreased as the number of repeated irradiations increased. The percentage readings for the 10th beam irradiation with respect to the readings for the primary beam irradiation were 84.6 ± 1.9%, 87.5 ± 2.4%, and 93.0 ± 3.0% at 6 MV, 10 MV, and 15 MV, respectively. CONCLUSIONS: The non-annealed RPLGD response to dose was hyperlinear for the 6 MV and 10 MV photon beams but not for the 15 MV photon beam. Additionally, the annealed RPLGD exhibited a fading phenomenon when the measurement was repeated several times and demonstrated a relatively large fading effect at low energies than at high energies.


Assuntos
Dosímetros de Radiação , Vidro , Imagens de Fantasmas , Fótons , Doses de Radiação , Dosagem Radioterapêutica , Sensibilidade e Especificidade
2.
PLoS One ; 15(12): e0241550, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33378398

RESUMO

For x- and gamma- irradiations delivering entrance doses from 2- up to 1000 Gy to commercial 1.0 mm thick borosilicate glass microscope slides, study has been made of their thermoluminescence yield. With an effective atomic number of 10.6 (approximating bone equivalence), photon energy dependency is apparent in the low x-ray energy range, with interplay between the photoelectric effect and attenuation. As an example, over the examined dose range, at 120 kVp the photon sensitivity has been found to be some 5× that of 60Co gamma irradiations, also with repeatability to within ~1%. The glow-curves, taking the form of a single prominent broad peak, have been deconvolved yielding at best fit a total of five peaks, the associated activation energies and frequency factors also being obtained. The results indicate borosilicate glass slides to offer promising performance as a low-cost passive radiation dosimeter, with utility for both radiotherapy and industrial applications.


Assuntos
Compostos de Boro/química , Fótons , Dosímetros de Radiação , Silicatos/efeitos da radiação , Dosimetria Termoluminescente/instrumentação , Compostos de Boro/efeitos da radiação , Relação Dose-Resposta à Radiação , Raios gama , Humanos , Doses de Radiação , Silicatos/química , Dosimetria Termoluminescente/métodos , Raios X
3.
Medicine (Baltimore) ; 99(47): e23328, 2020 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-33217871

RESUMO

To compare the effects of different photon energies on radiation planning by intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and helical tomotherapy (TOMO) for proximal gastric cancer (PGC). Network analysis with microarray procession and gene ontology were used to identify the effect of radiotherapy (RT) on PGC. Then, we retrospectively analyzed 8 PGC patients after receiving irradiation with a prescribed dose of 50.4 Gy. The Pinnacle treatment planning system (TPS, V9.8) was used to generate IMRT and VMAT plans by using 6 or 10 MV. TOMO plans were calculated on the Tomotherapy Planning Station Hi-Art Version 4.2.3 workstation (Tomotherapy Incorporated, Madison, WI, USA). PGC is associated with high DNA repair ability. TOMO plan results in higher tumor coverage and a better conformity index than IMRT and VMAT. 10-MV VMAT yields better dosimetric quality of the gradient index than 6-MV VMAT (P = .012). TOMO was associated with a lower irradiation dose in the mean dose to the right kidney (P = .049), left kidney and heart than 6-MV IMRT and 6-MV VMAT. 6-MV IMRT plan presented a higher dose of lung Dmean (P = .017) than 10-MV IMRT. Additionally, VMAT, using a planning energy of 6 MV, was associated with a significantly higher left kidney Dmean (P = .018) and V10 (P = .036) than a planning energy of 10 MV. TOMO is a better RT plan not only for tumor coverage but also for sparing organs at risk. IMRT and VMAT plans with 10 MV beams are more suitable than 6 MV beams for PGC treatment.


Assuntos
Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada/métodos , Neoplasias Gástricas/radioterapia , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fótons , Radiometria , Dosagem Radioterapêutica , Estudos Retrospectivos
4.
Phys Med Biol ; 65(22): 225029, 2020 11 24.
Artigo em Inglês | MEDLINE | ID: mdl-33231199

RESUMO

We recently developed a dedicated focusing multi-pinhole collimator for a stationary SPECT system that offers down to 120 µm (or 1.7 nL) spatial resolution SPECT images of cryo-cooled tissue samples (EXIRAD-3D). This collimator is suitable for imaging isotopes that are often used in small animal and diagnostic SPECT such as 125I (27 keV), 201Tl (71 keV), 99mTc (140 keV), and 111In (171 and 245 keV). The goal of the present work is to develop high-resolution pinhole imaging of tissue samples containing isotopes with high-energy photon emissions, for example, therapeutic alpha and beta emitters that co-emit high energy gammas (e.g. 213Bi (440 keV) and 131I (364 keV)) or 511 keV annihilation photons from PET isotopes. To this end, we optimise and evaluate a new high energy small-bore multi-pinhole collimator through simulations. The collimator-geometry was first optimised by simulating a Derenzo phantom scan with a biologically realistic activity concentration of 18F at two system sensitivities (0.30% and 0.60%) by varying pinhole placements. Subsequently, the wall thickness was selected based on reconstructions of a Derenzo phantom and a uniform phantom. The obtained collimators were then evaluated for 131I (364 keV), 213Bi (440 keV), 64Cu (511 keV), and 124I (511 + 603 keV) with biologically realistic activity concentrations, and also for some high activity concentrations of 18F, using digital resolution, mouse knee joint, and xenograft phantoms. Our results show that placing pinhole centres at a distance of 8 mm from the collimator inner wall yields good image quality, while a wall thickness of 43 mm resulted in sufficient shielding. The collimators offer resolutions down to 0.35 mm, 0.6 mm, 0.5 mm, 0.6 mm, and 0.5 mm when imaging 131I, 213Bi, 18F, 64Cu, and 124I, respectively, contained in tissue samples at biologically achievable activity concentrations.


Assuntos
Radioisótopos , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Animais , Desenho de Equipamento , Membro Posterior/diagnóstico por imagem , Camundongos , Modelos Teóricos , Imagens de Fantasmas , Fótons , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação
5.
Nat Commun ; 11(1): 5721, 2020 11 12.
Artigo em Inglês | MEDLINE | ID: mdl-33184297

RESUMO

A mouse skull is a barrier for high-resolution optical imaging because its thick and inhomogeneous internal structures induce complex aberrations varying drastically from position to position. Invasive procedures creating either thinned-skull or open-skull windows are often required for the microscopic imaging of brain tissues underneath. Here, we propose a label-free imaging modality termed laser scanning reflection-matrix microscopy for recording the amplitude and phase maps of reflected waves at non-confocal points as well as confocal points. The proposed method enables us to find and computationally correct up to 10,000 angular modes of aberrations varying at every 10 × 10 µm2 patch in the sample plane. We realized reflectance imaging of myelinated axons in vivo underneath an intact mouse skull, with an ideal diffraction-limited spatial resolution of 450 nm. Furthermore, we demonstrated through-skull two-photon fluorescence imaging of neuronal dendrites and their spines by physically correcting the aberrations identified from the reflection matrix.


Assuntos
Encéfalo/diagnóstico por imagem , Microscopia Confocal/métodos , Crânio/diagnóstico por imagem , Animais , Axônios , Dendritos , Imageamento Tridimensional/métodos , Camundongos , Microscopia Confocal/instrumentação , Neurônios , Imagem Óptica/instrumentação , Imagem Óptica/métodos , Fótons
6.
Nat Commun ; 11(1): 6011, 2020 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-33243997

RESUMO

The importance of green light for driving natural photosynthesis has long been underappreciated, however, under the presence of strong illumination, green light actually drives photosynthesis more efficiently than red light. This green light is absorbed by mixed vibronic Qy-Qx states, arising from chlorophyll (Chl)-Chl interactions, although almost nothing is known about these states. Here, we employ polarization-dependent two-dimensional electronic-vibrational spectroscopy to study the origin and dynamics of the mixed vibronic Qy-Qx states of light-harvesting complex II. We show the states in this region dominantly arise from Chl b and demonstrate how it is possible to distinguish between the degree of vibronic Qy versus Qx character. We find that the dynamics for states of predominately Chl b Qy versus Chl b Qx character are markedly different, as excitation persists for significantly longer in the Qx states and there is an oscillatory component to the Qx dynamics, which is discussed. Our findings demonstrate the central role of electronic-nuclear mixing in efficient light-harvesting and the different functionalities of Chl a and Chl b.


Assuntos
Transferência de Energia/fisiologia , Complexos de Proteínas Captadores de Luz/metabolismo , Fótons , Tilacoides/metabolismo , Clorofila/metabolismo , Clorofila A/metabolismo , Cor , Transferência de Energia/efeitos da radiação , Complexos de Proteínas Captadores de Luz/efeitos da radiação , Fotossíntese/fisiologia , Fotossíntese/efeitos da radiação , Folhas de Planta/citologia , Análise Espectral/métodos , Tilacoides/efeitos da radiação
7.
Sci Rep ; 10(1): 17546, 2020 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-33067572

RESUMO

The development of innovative immune cell therapies relies on efficient cell tracking strategies. For this, multiscale fluorescence-based analyses of transferred cells into the host with complementary techniques, including flow cytometry for high-throughput cell analysis and two-photon microscopy for deep tissue imaging would be highly beneficial. Ideally, cells should be labelled with a single fluorescent probe combining all the properties required for these different techniques. Due to the intrinsic autofluorescence of most tissues and especially the liver, far-red emission is also an important asset. However, the development of far-red emitting probes suitable for two-photon microscopy and compatible with clearing methods to track labelled immune cells in thick samples, remains challenging. A newly-designed water-soluble far-red emitting polymer probe, 19K-6H, with a large Stokes shift, was thus evaluated for the tracking of primary immune CD8 T cells. These cells, prepared from mouse spleen, were efficiently labelled with the 19K-6H probe, which was internalized via endocytosis and was highly biocompatible at concentrations up to 20 µM. Labelled primary CD8 T cells were detectable in culture by both confocal and two-photon microscopy as well as flow cytometry, even after 3 days of active proliferation. Finally, 19K-6H-labelled primary CD8 T cells were injected to mice in a classical model of immune mediated hepatitis. The efficient tracking of the transferred cells in the liver by flow cytometry (on purified non-parenchymal cells) and by two-photon microscopy on 800 µm thick cleared sections, demonstrated the versatility of the 19K-6H probe.


Assuntos
Rastreamento de Células/métodos , Fígado/patologia , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Animais , Endocitose/fisiologia , Fluorescência , Corantes Fluorescentes/química , Células HeLa , Humanos , Fígado/diagnóstico por imagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia de Fluorescência/métodos , Fótons
8.
Int J Nanomedicine ; 15: 6813-6825, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33061357

RESUMO

Background: Multidrug-resistant (MDR) bacterial strain is a serious medical problem. Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to many antibiotics and is often associated with several diseases such as arthritis, osteomyelitis, and endocarditis. The development of an alternative treatment for eliminating MDR bacteria such as MRSA has attracted a considerable amount of research attention. Moreover, the development of a material for highly efficient generation of reactive oxygen species (ROS) involving two-photon photodynamic therapy (PDT) is currently desirable. Materials and Methods: We present an example demonstrating that the use of water-soluble C60(OH)30 fullerenol with a 0.89 singlet oxygen quantum yield serving as a photosensitizer in PDT has the superior ability in effectively generating ROS. Results: It has ultra-low energy (228.80 nJ pixel-1) and can perform 900 scans under two-photon excitation (TPE) in the near-infrared region (760 nm) to completely eliminate the MDR species. Furthermore, the favorable two-photon properties are absorption of approximately 760 nm in wavelength, absolute cross-section of approximately 1187.50 Göeppert-Mayer units, lifetime of 6.640 ns, ratio of radiative to nonradiative decay rates of approximately 0.053, and two-photon stability under TPE. Conclusion: This enabled water-soluble C60(OH)30 fullerenol to act as a promising two-photon photosensitizer proceeding with PDT to easily eliminate MDR species.


Assuntos
Antibacterianos/farmacologia , Fulerenos/farmacologia , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Fotoquimioterapia/métodos , Fármacos Fotossensibilizantes/farmacologia , Antibacterianos/química , Farmacorresistência Bacteriana Múltipla , Fulerenos/química , Humanos , Fótons , Fármacos Fotossensibilizantes/química , Espécies Reativas de Oxigênio/química , Oxigênio Singlete/química , Solubilidade , Água/química
9.
Phys Med Biol ; 65(20): 205009, 2020 10 21.
Artigo em Inglês | MEDLINE | ID: mdl-33085649

RESUMO

PURPOSE: Evaluating the time-of-flight (TOF) resolution improvement that could be obtained using an easy crystal block modification which enables depth of interaction (DOI) assessment and simplifies the detector assembling process. METHOD: A fast optical Monte Carlo (MC) code was developed. The code was evaluated versus measurements of the energy resolution, number of detected scintillation photons and TOF resolution (TOFr) reported for different crystal photodetector setups. Then, MC simulations were performed for a modified crystal block section of 8 × 8 mm2 in which two partial saw cuts allow light sharing between four detector pixels with a strong dependence on the DOI. RESULTS: Relative differences between MC simulations and reported measurements were always below 10% for any quantities. The simulations showed that the best TOFr was obtained by leaving the partial saw cuts empty. This feature results from the fact that for a slant angle lower than 56 degrees, the scintillation photons undergo a lossless total reflection at the L[Y]SO → air boundary, which is hardly achievable using a reflector material. According to the simulations, this approach allows a TOFr improvement from 163 ps to 90 ps full width at half-maximum using a 22 mm thick LSO 0.2%Ca:Ce crystal coupled to a FBK-NUV-HD silicon photomultiplier. CONCLUSION: Sub-100 ps TOFr using thick LSO crystal appears achievable using this simple crystal block modification. The method reduces by a factor of 4 the number of crystal pixels to be covered by a reflective material and afterwards joined together. As clinical positron emission tomography contains about 60 000 crystal pixels, this benefit would reduce the assembling cost.


Assuntos
Custos e Análise de Custo , Lutécio , Método de Monte Carlo , Tomografia por Emissão de Pósitrons/economia , Tomografia por Emissão de Pósitrons/métodos , Razão Sinal-Ruído , Silicatos , Humanos , Fótons
11.
Phys Med Biol ; 65(20): 20NT02, 2020 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-33063695

RESUMO

The aim of dose calculation algorithm research is to improve the calculation accuracy while maximizing the calculation efficiency. In this study, the three-dimensional distribution of total energy release per unit mass (TERMA) and the electron density (ED) distribution are considered inputs in a method for calculating the three-dimensional dose distribution based on a convolutional neural network (CNN). Attempts are made to improve the efficiency of the collapsed cone convolution/superposition (CCCS) algorithm while providing an approach to improve the efficiency of other traditional dose calculation algorithms. Twelve sets of computed tomography (CT) images were employed for training. Data sets were generated by the CCCS algorithm with a random beam configuration. For each monoenergetic photon model, 7500 samples were generated for the training set, and 1500 samples were generated for the validation set. Training occurred for 0.5 MeV, 1 MeV, 2 MeV, 3 MeV, 4 MeV, 5 MeV, and 6 MeV monoenergetic photon models. To evaluate the usability under linac conditions, a comparison between CCCS and CNN-Dose was performed for the Mohan 6-MV spectrum for 12 additional new sets of CT images with different anatomies. A total of 1512 test samples were generated. For all anatomies, the mean value, 95% lower confidence limit (LCL) and 95% upper confidence limit (UCL) were 99.56%, 99.51% and 99.61%, respectively, at the 3%/2 mm criteria. The mean value, 95% LCL and 95% UCL were 98.57%, 98.46% and 98.67%, respectively, at the 2%/2 mm criteria. The results meet the relevant clinical requirements. In the proposed methods, the dose distribution of clinical energy can be obtained by TERMA, and the electronic density can be obtained with a CNN. This method can also be used for other traditional dose algorithms and displays potential in treatment planning, adaptive radiation therapy, and in vivo verification.


Assuntos
Algoritmos , Neoplasias de Cabeça e Pescoço/radioterapia , Neoplasias Pulmonares/radioterapia , Redes Neurais de Computação , Fótons/uso terapêutico , Planejamento da Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Neoplasias de Cabeça e Pescoço/diagnóstico por imagem , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Método de Monte Carlo , Dosagem Radioterapêutica
12.
Int J Nanomedicine ; 15: 6961-6973, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33061362

RESUMO

Background: Although graphene quantum dots (GQDs) have received considerable research attention for their applications in various fields, the use of GQDs, such as nitrogen-doped GQDs (N-GQDs) and amino-functionalized N-GQDs (amino-N-GQDs), as photosensitizers to facilitate photodynamic therapy (PDT) has received limited research intention. To address this research gap, this study prepared novel amino-N-GQDs and investigated their properties. Methods: The amino-N-GQDs subjected to two-photon excitation (TPE) exhibited remarkable bactericidal capability in PDT. The bonding compositions of nitrogen and the amino-functionalized group played a critical role in their antimicrobial effects. Results: Compared with amino-group-free N-GQDs and amino-N-free GQDs, the amino-N-GQDs generated a higher amount of reactive oxygen species, demonstrating their superior efficacy for two-photon PDT. Additionally, the intrinsic luminescence properties and high photostability of the amino-N-GQDs demonstrate their suitability as an effective two-photon contrast agent for tracking bacteria during two-photon biomedical imaging. Conclusion: The amino-N-GQD and their remarkable properties may provide an efficient alternative approach for observing and easily eliminating malignant microbes in the future.


Assuntos
Antibacterianos/farmacologia , Meios de Contraste/química , Nitrogênio/farmacologia , Fotoquimioterapia/métodos , Pontos Quânticos/química , Antibacterianos/química , Bacillus subtilis/efeitos dos fármacos , Grafite/química , Luminescência , Nitrogênio/química , Fótons , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia
14.
Anticancer Res ; 40(11): 6123-6135, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33109550

RESUMO

BACKGROUND/AIM: The importance of hadron therapy in the cancer management is growing. We aimed to refine the biological effect detection using a vertebrate model. MATERIALS AND METHODS: Embryos at 24 and 72 h postfertilization were irradiated at the entrance plateau and the mid spread-out Bragg peak of a 150 MeV proton beam and with reference photons. Radiation-induced DNA double-strand breaks (DSB) and histopathological changes of the eye, muscles and brain were evaluated; deterioration of specific organs (eye, yolk sac, body) was measured. RESULTS: More and longer-lasting DSBs occurred in eye and muscle cells due to proton versus photon beams, albeit in different numbers. Edema, necrosis and tissue disorganization, (especially in the eye) were observed. Dose-dependent morphological deteriorations were detected at ≥10 Gy dose levels, with relative biological effectiveness between 0.99±0.07 (length) and 1.12±0.19 (eye). CONCLUSION: Quantitative assessment of radiation induced changes in zebrafish embryos proved to be beneficial for the radiobiological characterization of proton beams.


Assuntos
Fótons , Prótons , Peixe-Zebra/fisiologia , Animais , Encéfalo/efeitos da radiação , Dano ao DNA , Modelos Animais de Doenças , Relação Dose-Resposta à Radiação , Embrião não Mamífero/efeitos da radiação , Olho/patologia , Olho/efeitos da radiação , Cinética , Tamanho do Órgão/efeitos da radiação , Eficiência Biológica Relativa , Saco Vitelino/patologia , Saco Vitelino/efeitos da radiação , Peixe-Zebra/embriologia
15.
Nat Commun ; 11(1): 5252, 2020 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-33067438

RESUMO

Simultaneous and efficient ultrafast recording of multiple photon tags contributes to high-dimensional optical imaging and characterization in numerous fields. Existing high-dimensional optical imaging techniques that record space and polarization cannot detect the photon's time of arrival owing to the limited speeds of the state-of-the-art electronic sensors. Here, we overcome this long-standing limitation by implementing stereo-polarimetric compressed ultrafast photography (SP-CUP) to record light-speed high-dimensional events in a single exposure. Synergizing compressed sensing and streak imaging with stereoscopy and polarimetry, SP-CUP enables video-recording of five photon tags (x, y, z: space; t: time of arrival; and ψ: angle of linear polarization) at 100 billion frames per second with a picosecond temporal resolution. We applied SP-CUP to the spatiotemporal characterization of linear polarization dynamics in early-stage plasma emission from laser-induced breakdown. This system also allowed three-dimensional ultrafast imaging of the linear polarization properties of a single ultrashort laser pulse propagating in a scattering medium.


Assuntos
Imagem Óptica/instrumentação , Fotografação/instrumentação , Gravação em Vídeo/instrumentação , Lasers , Imagem Óptica/métodos , Fotografação/métodos , Fótons , Gravação em Vídeo/métodos
16.
Radiat Res ; 194(5): 544-556, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33045066

RESUMO

Animal models of total-body irradiation (TBI) are used to elucidate normal tissue damage and evaluate the efficacy of medical countermeasures (MCM). The accuracy of these TBI models depends on the reproducibility of the radiation dose-response relationship for lethality, which in turn is highly dependent on robust radiation physics and dosimetry. However, the precise levels of radiation each organ absorbs can change dramatically when different photon beam qualities are used, due to the interplay between their penetration and the natural variation of animal sizes and geometries. In this study, we evaluate the effect of varying the radiation energy, namely cobalt-60 (Co-60); of similar penetration to a 4-MV polyenergetic beam), 6 MV and 15 MV, in the absorbed dose delivered by TBI to individual organs of eight Göttingen minipigs of varying weights (10.3-24.1 kg) and dimensions (17.5-25 cm width). The main organs, i.e. heart, lungs, esophagus, stomach, bowels, liver, kidneys and bladder, were contoured by an experienced radiation oncologist, and the volumetric radiation dose distribution was calculated using a commercial treatment planning system commissioned and validated for Co-60, 6-MV and 15-MV teletherapy units. The dose is normalized to the intended prescription at midline in the abdomen. For each animal and each energy, the body and organ dose volume histograms (DVHs) were computed. The results show that more penetrating photon energies produce dose distributions that are systematically and consistently more homogeneous and more uniform, both within individual organs and between different organs, across all animals. Thoracic organs (lungs, heart) received higher dose than prescribed while pelvic organs (bowel, bladder) received less dose than prescribed, due to smaller and wider separations, respectively. While these trends were slightly more pronounced in the smallest animals (10.3 kg, 19 cm abdominal width) and largest animals (>20 kg, ∼25 cm abdominal width), they were observed in all animals, including those in the 9-15 kg range typically used in MCM models. Some organs received an average absorbed dose representing <80% of prescribed dose when Co-60 was used, whereas all organs received average doses of >87% and >93% when 6 and 15 MV were used, respectively. Similarly, average dose to the thoracic organs reached as high as 125% of the intended dose with Co-60, compared to 115% for 15 MV. These results indicate that Co-60 consistently produces less uniform dose distributions in the Göttingen minipig compared to 6 and 15 MV. Moreover, heterogeneity of dose distributions for Co-60 is accentuated by anatomical and geometrical variations across various animals, leading to different absorbed dose delivered to organs for different animals. This difference in absorbed radiation organ doses, likely caused by the lower penetration of Co-60 and 6 MV compared to 15 MV, could potentially lead to different biological outcomes. While the link between the dose distribution and variation of biological outcome in the Göttingen minipig has never been explicitly studied, more pronounced dose heterogeneity within and between organs treated with Co-60 teletherapy units represents an additional confounding factor which can be easily mitigated by using a more penetrating energy.


Assuntos
Relação Dose-Resposta à Radiação , Porco Miniatura , Irradiação Corporal Total , Abdome/anatomia & histologia , Abdome/efeitos da radiação , Absorção de Radiação , Animais , Tamanho Corporal , Peso Corporal , Radioisótopos de Cobalto , Raios gama , Masculino , Modelos Animais , Especificidade de Órgãos , Aceleradores de Partículas , Pelve/anatomia & histologia , Pelve/efeitos da radiação , Fótons , Decúbito Ventral , Doses de Radiação , Tolerância a Radiação , Teleterapia por Radioisótopo/instrumentação , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Alta Energia/instrumentação , Ombro/anatomia & histologia , Ombro/efeitos da radiação , Suínos , Porco Miniatura/anatomia & histologia , Tomografia Computadorizada por Raios X
17.
Radiat Res ; 194(5): 465-475, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33045073

RESUMO

Carbon- (12C-) ion radiotherapy exhibits enhanced biological effectiveness compared to photon radiotherapy, however, the contribution of its interaction with the vasculature remains debatable. The effect of high-dose 12C-ion and photon irradiation on vascular permeability in moderately differentiated rat prostate tumors was compared using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Syngeneic R3327-HI rat prostate tumors were irradiated with a single dose of either 18 or 37 Gy 12C ions, or 37 or 75 Gy 6-MV photons (sub-curative and curative dose levels, respectively). DCE-MRI was performed one day prior to and 3, 7, 14 and 21 days postirradiation. Voxel-based tumor concentration-time curves were clustered based on their curve shape and treatment response was assessed as the longitudinal changes in the relative abundance per cluster. Radiation-induced vascular damage and increased permeability occurred at day 7 postirradiation for all treatment groups except for the 75 Gy photon-irradiated group, where the onset of vascular damage was delayed until day 14. No differences between irradiation modalities were found. Therefore, early vascular damage cannot explain the higher effectiveness of 12C ions relative to photons in terms of local tumor control for this moderately differentiated prostate tumor and the applied single high doses.


Assuntos
Adenocarcinoma/radioterapia , Permeabilidade Capilar/efeitos da radiação , Carbono/uso terapêutico , Radioterapia com Íons Pesados , Imagem por Ressonância Magnética/métodos , Fótons/uso terapêutico , Neoplasias da Próstata/radioterapia , Adenocarcinoma/sangue , Adenocarcinoma/diagnóstico por imagem , Animais , Linhagem Celular Tumoral , Relação Dose-Resposta à Radiação , Masculino , Transplante de Neoplasias , Análise de Componente Principal , Neoplasias da Próstata/irrigação sanguínea , Neoplasias da Próstata/diagnóstico por imagem , Distribuição Aleatória , Ratos , Transplante Heterotópico
18.
Radiat Res ; 194(4): 390-402, 2020 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-33045092

RESUMO

Owing to recent advances in computational dosimetry tools, an update is warranted for the dosimetry system for atomic bomb survivors that was established by the Joint U.S.Japan Working Group on the Reassessment of Atomic Bomb Dosimetry in 2002 (DS02). The DS02 system, and its predecessor, DS86, at the Radiation Effects Research Foundation (RERF), are based on adjoint Monte Carlo particle transport simulations coupled with stylized computational human phantoms. In our previous studies, we developed the J45 series of computational voxel phantoms representative of 1945 Japanese adults, children and pregnant females. The dosimetric impact of replacing the DS02/DS86 stylized phantoms by the J45 phantom series was also discussed through computation of organ doses for several idealized exposure scenarios. In the current study, we investigated the possible impact of introducing not only the J45 phantom series but also various methodological upgrades to the DS02 dosimetry system. For this purpose, we calculated organ doses in adults for 12 representative exposure scenarios having realistic particle energy and angular fluence, using different combinations of phantoms and dose calculation methods. Those doses were compared with survivor organ doses given by the DS02 system. It was found that the anatomical improvement in the J45 phantom series is the most important factor leading to potential changes in survivor organ doses. However, methodological upgrades, such as replacement of the adjoint Monte Carlo simulation with kerma approximation by the forward Monte Carlo simulation with secondary electron transport, can also improve the accuracy of organ doses by up to several percent.In addition, this study established a series of response functions, which allows for the rapid conversion of the unidirectional quasi-monoenergetic photon and neutron fluences from the existing DS02 system to organ doses within the J45 adult phantoms. The overall impact of introducing the response functions in the dosimetry system is not so significant, less than 10% in most cases, except for organs in which the calculation method or definition was changed, e.g., colon and bone marrow. This system of response functions can be implemented within a revision to the DS02 dosimetry system and used for future updates to organ doses within the Life Span Study of the atomic bomb survivors.


Assuntos
Sobreviventes de Bombas Atômicas , Simulação por Computador , Relação Dose-Resposta à Radiação , Modelos Biológicos , Órgãos em Risco/efeitos da radiação , Imagens de Fantasmas , Absorção de Radiação , Adulto , Feminino , Seguimentos , Humanos , Japão , Masculino , Método de Monte Carlo , Nêutrons , Especificidade de Órgãos , Fótons , Exposição à Radiação , Lesões por Radiação , Proteção Radiológica , Radiometria/instrumentação , Radiometria/métodos
20.
Nat Protoc ; 15(10): 3499-3526, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32968251

RESUMO

Formaldehyde (FA) is the simplest active carbonyl species that can be spontaneously produced in the body and plays important roles in human cognitive ability and spatial memory. However, excessive intake of FA may cause a series of diseases, including cancer, diabetes, heart and liver diseases and various neuropathies. Hence, the exploration of sensitive and fast detection methods for FA is crucial to understand and diagnose these diseases. Recently, fluorescent probes have been increasingly employed as powerful tools for detecting a broad range of different small molecules due to their high selectivity, rapid response, convenient operation and relatively non-invasive nature. Thus, we have developed two naphthalimide-based fluorescent probes for detecting FA in cells and in lysosomes. Compared with other FA fluorescent probes, these two probes have several advantages, including high sensitivity and selectivity, excellent two-photon properties and high signal-to-noise ratio. In this protocol, we provide detailed procedures for the synthesis of the two probes; characterization of their sensitivity, selectivity and stability in solution; and representative application procedures for detecting FA in living cells and mouse liver tissue slices. The protocol requires ~88 h to synthesize the probes, ~24 h to characterize the probes in solution and ~25 h to carry out the biological fluorescence imaging experiments in cells and liver tissue slices.


Assuntos
Corantes Fluorescentes/química , Corantes Fluorescentes/síntese química , Formaldeído/análise , Animais , Feminino , Células HeLa , Humanos , Fígado , Camundongos , Camundongos Endogâmicos BALB C , Imagem Óptica , Fótons
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA