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PubMed Journal Database | Physics in medicine and biology RSS

03:13 EST 23rd February 2020 | BioPortfolio

The US National Library of Medicine and National Institutes of Health manage PubMed.gov which comprises of more than 29 million records, papers, reports for biomedical literature, including MEDLINE, life science and medical journals, articles, reviews, reports and  books.

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For example view all recent relevant publications on Epigenetics and associated publications and clincial trials.

Showing PubMed Articles 1–25 of 987 from Physics in medicine and biology

Time-of-flight computed tomography - proof of principle.

Computed tomography has greatly improved over the last decade, especially through X-ray dose exposure reduction while maintaining image quality. Herein, a new concept is proposed to improve the contrast-to-noise ratio (CNR) by including the time-of-flight (TOF) information of individual photons to obtain further insight on the photon's trajectory and to reject scatter contribution. The proof of the concept relies on both simulation and experimental measurements in a cone-beam computed tomography arrangement...

Impact of temporal resolution and motion correction for dynamic contrast-enhanced MRI of the liver using an accelerated golden-angle radial sequence.

This paper presents a prospective study evaluating the impact on image quality and quantitative dynamic contrast-enhanced (DCE)-MRI perfusion parameters when varying the number of respiratory motion states when using an eXtra-Dimensional Golden-Angle Radial Sparse Parallel (XD-GRASP) MRI sequence. DCE acquisition was performed using a 3D stack-of-stars gradient-echo golden-angle radial acquisition in free-breathing with 100 spokes per motion state and temporal resolution of 6 seconds/volume, and using a non...

Ionization quenching correction for a 3D scintillator detector exposed to scanning proton beams.

The ionization quenching phenomenon in scintillators must be corrected to obtain accurate dosimetry in particle therapy. The purpose of this study was to develop a methodology for correcting camera projection measurements of a 3D scintillator detector exposed to proton pencil beams. Birks' ionization quenching model and the energy deposition by secondary electrons (EDSE) model were used to correct the light captured by a prototype 3D scintillator detector. The detector was made of a 20 cm  20 cm  20 c...

Improving accuracy and robustness of deep convolutional neural network based thoracic OAR segmentation.

Deep convolutional neural network (DCNN) has shown great success in medical image segmentation. However, most studies involve training and testing on the same dataset. Little work has been done to investigate the generalization errors of DCNN on a different dataset. This work investigated the generalization errors observed when apply a well-trained DCNN model to data from our local institution. It was found that even a subtle shift of organs inside patient body, caused by abdominal compression technique use...

2D directional ramp filter.

Usual tomographic reconstruction methods start by filtering projections before backprojecting the data. In some cases, inverting the filtering and the backprojection steps can be useful to preserve spatial information. In this paper, an intermediate between a filter-backproject and a backproject-filter approach is proposed, based on the extension of the usual ramp filter to two dimensions. To this end, an expression for a band-limited 2D version of the ramp filter is derived. We have tested this filter on s...

Meshless reconstruction technique for digital tomosynthesis.

A novel meshless reconstruction algorithm for Digital Tomosynthesis (DT) is presented and assessed against experimental data. The algorithm does not require a three-dimensional grid or mesh allocation and performs a slice-by-slice reconstruction where each slice position can be chosen at runtime. The methodology is based on the filtered backprojection algorithm adapted to DT. However, in the traditional approach the backprojection comes first and the filtering follows. Because the backprojection requires ra...

Stylized versus voxel phantoms: a juxtaposition of organ depth distributions.

For external irradiation, the variability in organ dose estimation found between computational phantom generations arises particularly from the differences in organ positioning. This work represents the first effort to quantify the differences in organ depth below the body surface between a stylized and voxel phantom series. Herein, the revised Oak Ridge National Laboratory stylized phantom series and the University of Florida/National Cancer Institute voxel phantom series were compared. Both series include...

Infrared navigation system for light dosimetry during pleural photodynamic therapy.

Pleural photodynamic therapy (PDT) is performed intraoperatively for the treatment of microscopic disease in patients with malignant pleural mesothelioma. Accurate delivery of light dose is critical to PDT efficiency. As a standard of care, light fluence is delivered to the prescribed fluence using 8 isotropic detectors in pre-determined discrete locations inside the pleural cavity that is filled with a dilute Intralipid solution. An optical infrared (IR) navigation system was used during light delivery to ...

Time-space Fourier κω' filter for motion artifacts compensation during transcranial fluorescence brain imaging.

Intravital imaging of brain vasculature through the intact cranium in vivo is based on the evolution of the fluorescence intensity and provides an ability to characterize various physiological processes in the natural context of cellular resolution. The involuntary motions of the examined subjects often limit in vivo non-invasive functional optical imaging. Conventional imaging diagnostic modalities encounter serious difficulties in correction of artificial motions, associated with the rapid structural vari...

DeepDose: towards a fast dose calculation engine for radiation therapy using deep learning.

We present DeepDose, a deep learning framework for fast dose calculations in radiation therapy. Given a patient anatomy and linear-accelerator IMRT multi-leaf-collimator shape or segment, a novel set of physics-based inputs is calculated that encode the linac machine parameters into the underlying anatomy. These inputs are then used to train a deep convolutional network to derive the dose distribution of individual MLC shapes on a given patient anatomy. In this work we demonstrate the proof-of-concept appli...

MR to CT synthesis with multicenter data in the pelvic era using a conditional generative adversarial network.

The establishment of an MRI-only workflow in radiotherapy depends on the ability to generate an accurate synthetic-CT (sCT) for dose calculation. Previously proposed methods have used a Generative Adversarial Network (GAN) for fast sCT generation in order to simplify the clinical workflow and reduces uncertainties. In the current paper we use a conditional Generative Adversarial Network (cGAN) framework called pix2pixHD to create a robust model prone to multicenter data. This study included T2-weighted MR a...

Fluence perturbation from fiducial markers due to edge-scattering measured with pixel sensors for 12C ion beams.

Fiducial markers are nowadays a common tool for patient positioning verification before radiotherapy treatment. These markers should be visible on X-ray projection imaging, produce low streak artifacts on CTs and induce small dose perturbations due to edge-scattering effects during the ion-beam therapy treatment. In this study, the latter effect was investigated and the perturbations created by the markers were evaluated with a new measurement method using a tracker system composed of six CMOS pixel sensors...

Image domain multi-material decomposition using single energy CT.

Multi-material decomposition (MMD) technique decomposes the CT images into basis material images and has been promising in clinical practice for material composition quantification within the human body. MMD could be implemented using the image data acquired from spectral CT or its special case, dual-energy CT (DECT) while the spectral CT data acquisition usually requires a hardware modification. In this paper, we propose an image domain MMD method using single energy CT (SECT). The proposed objective funct...

Physics-guided machine learning for 3-D quantitative quasi-static elasticity imaging.

We present a 3-D extension of the Autoprogressive Method (AutoP) for quantitative quasi-static ultrasonic elastography (QUSE) based on sparse sampling of force-displacement measurements. Compared to current model-based inverse methods, our approach requires neither geometric nor constitutive model assumptions. We build upon our previous report for 2-D QUSE [1] and demonstrate the feasibility of recovering the 3-D linear-elastic material property distribution of gelatin phantoms under compressive loads. Meas...

Systematic quantification of nanoscopic dose enhancement of gold nanoparticles in ion beams.

High-Z material nanoparticles are being studied as localized dose enhancers in radiotherapeutic applications. Here, the nano-scale physical dose en\-hance\-ment of proton, carbon and oxygen ion beam radiation by gold nanoparticles was studied by means of Monte Carlo track structure simulation with the TRAX code. We present 2D distributions and radial profiles of the additional dose and the dose enhancement factor for two geometries which consider an isolated and a water-em\-bedded nanoparticle, respectively...

Towards automated in vivo tracheal mucociliary transport measurement: detecting and tracking particle movement in synchrotron phase-contrast X-ray images.

Accurate in vivo quantification of airway mucociliary transport (MCT) in animal models is important for understanding diseases such as cystic fibrosis, as well as for developing therapies. A non-invasive method of measuring MCT behaviour, based on tracking the position of micron sized particles using Synchrotron X-ray imaging, has previously been described. In previous studies, the location (and path) of each particle was tracked manually, which is a time consuming and subjective process. Here we describe p...

Novel test field diversity method for demonstrating magnetic resonance imaging safety of active implantable medical devices.

Electromagnetic (EM) radiofrequency (RF) safety testing of elongated active implantable medical devices (AIMD) during magnetic resonance imaging (MRI) requires an RF response model of the implant to assess a wide range of exposure conditions. The model must be validated using a sufficiently large set of incident tangential electric field () conditions that provide diversified exposure. Until now, this procedure was very time consuming and often resulted in poorly definedconditions. In this paper, we propose...

Anthropomorphic phantom for deformable lung and liver CT and MR imaging for radiotherapy.

In this study, a functioning and ventilated anthropomorphic phantom was further enhanced for the purpose of CT and MR imaging of the lung and liver. A deformable lung, including respiratory tract was 3D printed. Within the lung's inner structures is a solid region shaped from a patient's lung tumour and six nitro-glycerine capsules as reference landmarks. The full internal mesh was coated, and the tumour filled, with polyorganosiloxane based gel. A moulded liver was created with an external casing of silico...

Cerenkov luminescence and PET imaging of 90Y: capabilities and limitations in small animal applications.

The in vivo sensitivity limits and quantification performance of Cerenkov luminescence imaging have been studied using a tissue-like mouse phantom and 90Y. For a small, 9 mm deep target in the phantom, with no background activity present, the Cerenkov luminescence 90Y detection limit determined from contrast-to-noise ratios is 10 nCi for a 2 min exposure with a sensitive CCD camera and no filters. For quantitative performance, the values extracted from regions of interest on the images are linear within 5% ...

Proton range verification with ultrasound imaging using injectable radiation sensitive nanodroplets: a feasibility study.

Technologies enabling in vivo range verification during proton therapy are actively sought as a means to reduce the clinical safety margins currently adopted to avoid tumor underdosage. In this contribution, we applied the semi-empirical theory of radiation-induced vaporization of superheated liquids to coated nanodroplets. Nanodroplets are injectable phase-change contrast agents that can vaporize into highly echogenic microbubbles to provide contrast in ultrasound images. We exposed nanodroplet dispersions...

Automatic bi-objective parameter tuning for inverse planning of high-dose-rate prostate brachytherapy.

We present an automatic bi-objective parameter-tuning approach for inverse planning methods for high-dose-rate prostate brachytherapy, which aims to overcome the difficult and time-consuming manual parameter tuning that is currently required to obtain patient-specific high-quality treatment plans. We modelled treatment planning as a bi-objective optimization problem, in which dose-volume-based planning criteria related to target coverage are explicitly separated from organ-sparing criteria. When this model ...

Locally optimized correlation-guided Bayesian adaptive regularization for ultrasound strain imaging.

Ultrasound strain imaging utilizes radio-frequency (RF) ultrasound echo signals to estimate the relative elasticity of tissue under deformation. Due to the diagnostic value inherent in tissue elasticity, ultrasound strain imaging has found widespread clinical and preclinical applications. Accurate displacement estimation using pre and post-deformation RF signals is a crucial first step to derive high quality strain tensor images. Incorporating regularization into the displacement estimation framework is a c...

Pre-clinical evaluation of dual-layer spectral computed tomography-based stopping power prediction for particle therapy planning at the Heidelberg Ion Beam Therapy Center.

Accurate beam range prediction during clinical treatment planning is key to improve targeted dose delivery in proton and heavy ion therapy. A substantial source of beam range uncertainty is the prediction of ion stopping power ratio relative to water (SPR) from an empirical calibration based on conventional X-ray computed tomography (CT) used in clinical practice today. The aim of this study was to investigate the potential of a novel spectral CT imaging technique based on a dual-layer detector-based approa...

A practical method for quantifying dose in bone and lung using TLDs when using 6 and 15 MV photon beams.

This paper presents a practical method for converting dose measured with thermoluminescent dosimeters (TLD) to dose in lung and bone for 6 MV and 15 MV photon beams. Monte Carlo (MC) simulations and Burlin cavity theory calculations were performed to calculate f, the dose-to-TLD to dose-to-medium conversion factor. A practical method was proposed for converting TLD-measured-dose to dose-in-medium using the TLD dose calibration in water and f, dose-to-medium to dose-to-water conversion factor. Theoretical ca...

Chemical radiation dosimetry in magnetic fields: characterization of a Fricke-type chemical detector in 6 MV photon beams and magnetic fields up to 1.42 T.

In magnetic resonance guided radiotherapy (MRgRT) radiation dose measurements needs to be performed in the presence of a magnetic field. In this study, the influence of magnetic fields on the readings of a Fricke detector, a chemical dosimeter, have been investigated in 6 MV photon beams. This type of detector has been chosen, as the Federal Office of Metrology (METAS, Switzerland) has great experience with Fricke dosimetry and since it is not expected that this detector is greatly affected by the presence ...


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