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Ethan Phillip M LaRochelle, Jennifer R Shell, Jason R Gunn, Scott C Davis, Brian W Pogue
During external beam radiotherapy (EBRT), in vivo Cherenkov optical emissions can be used as a dosimetry tool or to excite luminescence, termed Cherenkov-excited luminescence (CEL) with microsecond-level time-gated cameras. The goal of this work was to develop a complete theoretical foundation for the detectable signal strength, in order to provide guidance on optimization of the limits of detection and how to optimize near real time imaging. The key parameters affecting photon production, propagation and detection were considered and experimental validation with both tissue phantoms and a murine model are shown...
March 20, 2018: Physics in Medicine and Biology
Patryk Zradziński
PURPOSE: In this work, the inter-person variability of hazards caused by a low frequency magnetic field exposure (of various polarisation and homogeneity near to the magneto therapy applicator) to users of BAHA hearing implants were investigated with respect to various head structures. MATERIAL AND METHODS: The effects of exposure were evaluated by numerical simulations of the electric field (Ein ) induced in head phantoms (regular or with implant model). Phantoms mimic head dimensions and thicknesses of layers of skin, fat, skull bones and brain...
March 20, 2018: International Journal of Radiation Biology
Yoshitaka Inui, Takashi Ichihara, Masaki Uno, Masanobu Ishiguro, Kengo Ito, Katsuhiko Kato, Hajime Sakuma, Hidehiko Okazawa, Hiroshi Toyama
OBJECTIVE: Statistical image analysis of brain SPECT images has improved diagnostic accuracy for brain disorders. However, the results of statistical analysis vary depending on the institution even when they use a common normal database (NDB), due to different intrinsic spatial resolutions or correction methods. The present study aimed to evaluate the correction of spatial resolution differences between equipment and examine the differences in skull bone attenuation to construct a common NDB for use in multicenter settings...
March 19, 2018: Annals of Nuclear Medicine
Ji-Bin Zhang, Li-Rong Zhao, Tian-Xiang Cui, Xie-Wan Chen, Qiao Yang, Yi-Bing Zhou, Zheng-Tang Chen, Shao-Xiang Zhang, Jian-Guo Sun
The aim of the present study was to investigate the optimal strategy and dosimetric measurement of thoracic radiotherapy based on three-dimensional (3D) modeling of mediastinal lymph nodes (MLNs). A 3D model of MLNs was constructed from a Chinese Visible Human female dataset. Image registration and fusion between reconstructed MLNs and original chest computed tomography (CT) images was conducted in the Eclipse™ treatment planning system (TPS). There were three plans, including 3D conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT), which were designed based on 10 cases of simulated lung lesions (SLLs) and MLNs...
April 2018: Oncology Letters
K Mohamathu Rafic, S Amalan, B S Timothy Peace, B Paul Ravindran
Background and aim: The practicability of computing dose calculation on cone beam CT (CBCT) has been widely investigated. In most clinical scenarios, the craniocaudal scanning length of CBCT is found to be inadequate for localization. This study aims to explore extended tomographic localization and adaptive dose calculation strategies using Hounsfield unit (HU) corrected CBCT image sets. Materials and methods: Planning CT (pCT) images of the Rando phantom (T12 -to-midthigh) were acquired with pelvic-protocol using Biograph CT-scanner...
March 2018: Reports of Practical Oncology and Radiotherapy
M Valente, J Vedelago, D Chacón, F Mattea, J Velásquez, P Pérez
International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography...
March 8, 2018: Applied Radiation and Isotopes
Sung Jun Maeng, Jinhwan Kim, Gyuseong Cho
ICRP (2011) revised the dose limit to the eye lens to 20 mSv/y based on a recent epidemiological study of radiation-induced cataracts. Maintenance of steam generators at nuclear power plants is one of the highest radiation-associated tasks within a non-uniform radiation field. This study aims to evaluate eye lens doses in the steam generators of the Korean OPR1000 design. The source term was characterized based on the CRUD-specific activity, and both the eye lens dose and organ dose were simulated using MCNP6 combined with an ICRP voxel phantom and a mesh phantom, respectively...
March 15, 2018: Radiation Protection Dosimetry
Madeleine S Durkee, Landon D Nash, Fatemeh Nooshabadi, Jeffrey D Cirillo, Duncan J Maitland, Kristen C Maitland
The rapid development of new optical imaging techniques is dependent on the availability of low-cost, customizable, and easily reproducible standards. By replicating the imaging environment, costly animal experiments to validate a technique may be circumvented. Predicting and optimizing the performance of in vivo and ex vivo imaging techniques requires testing on samples that are optically similar to tissues of interest. Tissue-mimicking optical phantoms provide a standard for evaluation, characterization, or calibration of an optical system...
February 12, 2018: Journal of Visualized Experiments: JoVE
Canan Koksal, Ugur Akbas, Nazmiye Donmez Kesen, Murat Okutan, Hatice Bilge, Gonul Kemikler
PURPOSE: The purpose of this study was to perform pretreatment patient-specific quality assurance (QA) for intracranial irradiation using CyberKnife with an ion chamber. METHODS: Twenty-five intracranial plans created using the ray-tracing algorithm were used for this study. Computed tomography (CT) images of the water-equivalent RW3 slab phantom with PinPoint ionization chamber were acquired with 1-mm slice thickness and transferred to the MultiPlan treatment planning system (TPS)...
January 2018: Journal of B.U.ON.: Official Journal of the Balkan Union of Oncology
Vivian Pera, Kavon Karrobi, Syeda Tabassum, Fei Teng, Darren Roblyer
Spatial frequency domain imaging (SFDI) is a wide-field diffuse optical imaging modality that has attracted considerable interest in recent years. Typically, diffuse reflectance measurements of spatially modulated light are used to quantify the optical absorption and reduced scattering coefficients of tissue, and with these, chromophore concentrations are extracted. However, uncertainties in estimated absorption and reduced scattering coefficients are rarely reported, and we know of no method capable of providing these when look-up table (LUT) algorithms are used to recover the optical properties...
February 1, 2018: Biomedical Optics Express
Mikkel Thøgersen, John Hansen, Lars Arendt-Nielsen, Herta Flor, Laura Petrini
The purpose of the present study was to assess changes in body perception when visual feedback was removed from the hand and arm with the purpose of resembling the visual deprivation arising from amputation. The illusion was created by removing the visual feedback from the participants' own left forearm using a mixed reality (MR) and green screen environment. Thirty healthy persons (15 female) participated in the study. Each subject experienced two MR conditions, one with and one without visual feedback from the left hand, and a baseline condition with normal vision of the limb (no MR)...
March 15, 2018: Behavioural Brain Research
Kai Cao, Stephen W G Tait
Apoptotic cell death serves as an important tumor suppressor mechanism at multiple steps during cancer progression. Equally, engagement of apoptosis represents a potent therapeutic effector mechanism. Nevertheless, the role of apoptosis in cancer may be more complex than previously thought. Indeed, various studies have found that apoptosis signaling also has oncogenic potential. In this review, we discuss how apoptosis can promote cancer and how these effects might be targeted to optimize apoptosis-inducing anticancer therapy...
2018: International Review of Cell and Molecular Biology
Sa Xiao, He Deng, Caohui Duan, Junshuai Xie, Huiting Zhang, Xianping Sun, Chaohui Ye, Xin Zhou
Dynamic hyperpolarized (HP)129 Xe MRI is able to visualize the process of lung ventilation, which potentially provides unique information about lung physiology and pathophysiology. However, the longitudinal magnetization of HP129 Xe is nonrenewable, making it difficult to achieve high image quality while maintaining high temporal-spatial resolution in the pulmonary dynamic MRI. In this paper, we propose a new accelerated dynamic HP129 Xe MRI scheme incorporating the low-rank, sparse and gas-inflow effects (L + S + G) constraints...
March 8, 2018: Journal of Magnetic Resonance
Marko Barjaktarović, Milica M Janković, Marija Jeremić, Milovan Matović
Radioiodine therapy in the treatment of differentiated thyroid carcinoma (DTC) is used in clinical practice for the ablation of thyroid residues and/or destruction of tumour tissue. Whole-body scintigraphy for visualization of the spatial 131I distribution performed by a gamma camera (GC) is a standard procedure in DTC patients after application of radioiodine therapy. A common problem is the precise topographic localization of regions where radioiodine is accumulated even in SPECT imaging. SPECT/CT can provide precise topographic localization of regions where radioiodine is accumulated, but it is often unavailable, especially in developing countries because of the high price of the equipment...
March 9, 2018: Computers in Biology and Medicine
Shu-Hsien Chu, Keshab K Parhi, Christophe Lenglet
A joint structural-functional brain network model is presented, which enables the discovery of function-specific brain circuits, and recovers structural connections that are under-estimated by diffusion MRI (dMRI). Incorporating information from functional MRI (fMRI) into diffusion MRI to estimate brain circuits is a challenging task. Usually, seed regions for tractography are selected from fMRI activation maps to extract the white matter pathways of interest. The proposed method jointly analyzes whole brain dMRI and fMRI data, allowing the estimation of complete function-specific structural networks instead of interactively investigating the connectivity of individual cortical/sub-cortical areas...
March 16, 2018: Scientific Reports
Lorenzo Placidi, Michele Togno, Damien C Weber, Antony J Lomax, Jan Hrbacek
PURPOSE: Wedge phantoms coupled with a CCD camera are suggested as a simple means to improve the efficiency of quality assurance for pencil beam scanning (PBS) proton therapy, in particular to verify energy/range consistency on a daily basis. The method is based on the analysis of an integral image created by a pencil beam (PB) pattern delivered through a wedge. We have investigated the reproducibility of this method and its dependence on setup and positional beam errors for a commercially available phantom (Sphinx® , IBA Dosimetry) and CCD camera (Lynx® , IBA Dosimetry) system...
March 13, 2018: Zeitschrift Für Medizinische Physik
Shelley HuaLei Zhang, Stephan E Maier, Lawrence P Panych
PURPOSE: Magnetic resonance spectroscopic imaging (MRSI), under low-spatial resolution settings, often suffers signal contamination from neighboring voxels due to ringing artifacts. Spatial localization can be improved by constraining the point-spread-function (PSF). Here the effectiveness of the two-dimensional PSF-Choice technique in providing improved spatial localization for MRSI is demonstrated. THEORY AND METHODS: The PSF-Choice technique constrains the PSF to a desired shape by manipulating the weighting of RF excitation pulse throughout phase-encode steps...
March 3, 2018: Journal of Magnetic Resonance
David Hasler, Dominik Obrist
The flow field past a prosthetic aortic valve comprises many details that indicate whether the prosthesis is functioning well or not. It is, however, not yet fully understood how an optimal flow scenario would look, i.e. which subtleties of the fluid dynamics in place are essential regarding the durability and compatibility of a prosthetic valve. In this study, we measured and analyzed the 3D flow field in the vicinity of a bio-prosthetic heart valve in function of the aortic root size. The measurements were conducted within aortic root phantoms of different size, mounted in a custom-built hydraulic setup, which mimicked physiological flow conditions in the aorta...
2018: PloS One
Radosław Mrówczyński, Artur Jędrzak, Kosma Szutkowski, Bartosz F Grześkowiak, Emerson Coy, Roksana Markiewicz, Teofil Jesionowski, Stefan Jurga
Polydopamine (PDA)-coated magnetic nanoparticles functionalized with mono-6-thio-β-cyclodextrin (SH-βCD) were obtained and characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Nuclear and Magnetic Resonance Imaging (NMR and MRI), and doxorubicin (DOXO)-loading experiments. The liver cancer cellular internalization of DOXO-loaded nanoparticles was investigated by confocal imaging microscopy. Synthesized nanomaterials bearing a chemotherapeutic drug and a layer of polydopamine capable of absorbing near-infrared light show high performance in the combined chemo- and photothermal therapy (CT-PTT) of liver cancer due to the synergistic effect of both modalities as demonstrated in vitro...
March 16, 2018: Nanomaterials
Idan Steinberg, Gil Tamir, Israel Gannot
Solid malignant tumors are one of the leading causes of death worldwide. Many times complete removal is not possible and alternative methods such as focused hyperthermia are used. Precise control of the hyperthermia process is imperative for the successful application of such treatment. To that end, this research presents a fast method that enables the estimation of deep tissue heat distribution by capturing and processing the transient temperature at the boundary based on a bio-heat transfer model. The theoretical model is rigorously developed and thoroughly validated by a series of experiments...
March 16, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
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