Dosimetric impact of dual-energy CT tissue segmentation for low-energy prostate brachytherapy: a Monte Carlo study.
ard H Abstract {\color{red}The purpose of this study is} to evaluate the impact of a novel tissue characterization method using dual-energy over single-energy computed tomography (DECT and SECT) on Monte Carlo (MC) dose calculations for low-dose rate (LDR) prostate brachytherapy performed in a patient like geometry. A virtual patient geometry is created using contours from a real patient pelvis CT scan, where known elemental compositions and varying densities are overwritten in each voxel. A second phantom is made with additional calcifications. \textcolor{red}{Both phantoms are the ground truth with which al...
Source: Physics in Medicine and Biology - December 20, 2017 Category: Physics Authors: Remy C, Lalonde A, Béliveau-Nadeau D, Carrier JF, Bouchard H Tags: Phys Med Biol Source Type: research

Characterization of the first RF coil dedicated to 1.5 T MR guided radiotherapy.
In conclusion, the investigated MR-coil can be utilized for treatments with the 1.5T-linac system. However, there is still significant room for improvement when considering both the dosimetric and imaging performance of the coil. PMID: 29260729 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 20, 2017 Category: Physics Authors: Hoogcarspel SJ, Zijlema SE, Tijssen RHN, Kerkmeijer LGW, Juergenliemk-Schulz IM, Lagendijk JJW, Raaymakers BW Tags: Phys Med Biol Source Type: research

Measurement of effective detective quantum efficiency for a photon counting scanning mammography system and comparison with two flat panel full-field digital mammography systems.
Abstract Effective Detective Quantum Efficiency (eDQE) describes the resolution and noise properties of an imaging system along with scatter and primary transmission, all measured under clinically appropriate conditions. Effective dose efficiency (eDE) is the eDQE normalised to mean glandular dose and has been proposed as a useful metric for the optimisation of clinical imaging systems. The aim of this study was to develop a methodology for measuring eDQE and eDE on a Philips MicroDose Mammography (MDM) L30 photon counting scanning system, and to compare performance with two conventional flat panel systems. A...
Source: Physics in Medicine and Biology - December 20, 2017 Category: Physics Authors: Wood TJ, Moore CS, Saunderson JR, Beavis AW Tags: Phys Med Biol Source Type: research

Focused ultrasound-facilitated brain drug delivery using optimized nanodroplets: vaporization efficiency dictates large molecular delivery.
In conclusion, the vaporization efficiency of nanodroplets positively impacted the amount of molecules delivered to the brain. The OFP droplets due to the higher vaporization efficiency served as better acoustic agents to deliver large molecules safely and efficiently to the brain compared with the DFB droplets. PMID: 29260735 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 20, 2017 Category: Physics Authors: Wu SY, Fix SM, Arena CB, Chen CC, Zheng W, Olumolade OO, Papadopoulou V, Novell A, Dayton PA, Konofagou EE Tags: Phys Med Biol Source Type: research

Comparison of myocardial blood flow estimates from dynamic contrast-enhanced magnetic resonance imaging obtained with three quantitative analysis methods.
one I Abstract Dynamic Contrast-Enhanced Cardiovascular Magnetic Resonance Imaging may quantitatively assess the Myocardial Blood Flow (MBF), recovering the tissue impulse-response function to transit of gadolinium bolus through myocardium. Several deconvolution techniques are available, using various models for the impulse-response. The method choice may influence the results, producing differences that have not been deeply investigated yet. Three methods for quantifying myocardial perfusion were compared: Fermi Function Modeling (FFM), Tofts Model (TM), and Gamma Function model (GF), the latter traditionally use...
Source: Physics in Medicine and Biology - December 19, 2017 Category: Physics Authors: Borrazzo C, Galea N, Pacilio M, Altabella L, Preziosi E, Carnì M, Ciolina F, Vullo F, Francone M, Catalano C, Carbone I Tags: Phys Med Biol Source Type: research

A comprehensive study of lateral fall-off (penumbra) optimisation for pencil beam scanning (PBS) proton therapy.
In conclusion, collimated edge-enhancement combined with the variable pre-absorber is the recommended setting to minimize the lateral penumbra for PBS. Without collimator, it would be favourable to use a variable pre-absorber for large air gaps and an automatic pre-absorber for small air gaps. PMID: 29256441 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 19, 2017 Category: Physics Authors: Winterhalter C, Lomax AJ, Oxley D, Weber DC, Safai S Tags: Phys Med Biol Source Type: research

A novel upwind stabilized discontinuous finite element angular framework for deterministic dose calculations in magnetic fields.
Abstract Angular discretization impacts nearly every aspect of a deterministic solution to the linear Boltzmann transport equation (LBTE), especially in the presence of magnetic fields, as modeled by a streaming operator in angle. In this work a novel stabilization treatment of the magnetic field term is developed for an angular finite element discretization on the unit sphere, specifically involving piecewise partitioning of path integrals along curved element edges into uninterrupted segments of incoming and outgoing flux, with outgoing components updated iteratively. Correct order-of-accuracy for this angular f...
Source: Physics in Medicine and Biology - December 19, 2017 Category: Physics Authors: Yang R, Zelyak O, Fallone BG, St-Aubin J Tags: Phys Med Biol Source Type: research

Independent Monte-Carlo dose calculation for MLC based CyberKnife radiotherapy.
Abstract This work aims to develop, implement and validate a Monte Carlo (MC)-based independent dose calculation (IDC) framework to perform patient-specific quality assurance (QA) for multi-leaf collimator (MLC)-based CyberKnife® (Accuray Inc., Sunnyvale, CA) treatment plans. The IDC framework uses an XML-format treatment plan as exported from the treatment planning system (TPS) and DICOM format patient CT data, an MC beam model using phase spaces, CyberKnife MLC beam modifier transport using the EGS++ class library, a beam sampling and coordinate transformation engine and dose scoring using DOSXYZnrc. The fra...
Source: Physics in Medicine and Biology - December 19, 2017 Category: Physics Authors: Mackeprang PH, Vuong D, Volken W, Henzen D, Schmidhalter D, Malthaner M, Mueller S, Frei D, Stampanoni MFM, Dal Pra A, Aebersold DM, Fix MK, Manser P Tags: Phys Med Biol Source Type: research

CPU time optimization and precise adjustment of the Geant4 physics parameters for a VARIAN 2100 C/D gamma radiotherapy linear accelerator simulation using GAMOS.
Abstract We have verified the GAMOS/Geant4 simulation model of a 6 MV VARIAN 2100 linear accelerator by the procedure of adjusting the initial beam parameters to fit the Percentage Depth Dose and Cross Profile Dose experimental data at different depths in a water phantom. Thanks to the use of a wide range of field sizes, from 2x2 cm2 to 40x40 cm2, a small phantom voxel size and high statistics, a fine precision in the determination of the beam parameters have been achieved. This precision has allowed us to make a thorough study of the different physics models and parameters that Geant4 offers. The three Geant4 ele...
Source: Physics in Medicine and Biology - December 19, 2017 Category: Physics Authors: Arce P, Lagares JI Tags: Phys Med Biol Source Type: research

Characterization of Compton-scatter imaging with an analytical simulation method.
Abstract By collimating the photons scattered when a megavoltage therapy beam interacts with the patient, a Compton-scatter image may be formed without the delivery of extra dose. To characterize and assess the potential of the technique, an analytical model for simulating scatter images was developed and validated against Monte Carlo (MC). For three phantoms, the scatter images collected during irradiation with a 6 MV flattening-filter-free therapy beam were simulated. Images, profiles, and spectra were compared for different phantoms and different irradiation angles. The proposed analytical method simulates accu...
Source: Physics in Medicine and Biology - December 15, 2017 Category: Physics Authors: Jones KC, Redler G, Templeton A, Bernard D, Turian JV, Chu JCH Tags: Phys Med Biol Source Type: research

Anthropomorphic thorax phantom for cardio-respiratory motion simulation in tomographic imaging.
KP Abstract Patient motion during medical imaging using techniques such as computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), or single emission computed tomography (SPECT) is well known to degrade images leading to blurring effects or severe artifacts. Motion correction methods try to overcome this degrading effects. However, they need to be validated under realistic conditions. In the present work, a sophisticated anthropomorphic thorax phantom is presented that combines several aspects of a simulator for cardio-respiratory motion. The phantom allows to simulate vari...
Source: Physics in Medicine and Biology - December 15, 2017 Category: Physics Authors: Bolwin K, Czekalla B, Frohwein LJ, Buther F, Schäfers KP Tags: Phys Med Biol Source Type: research

Simultaneous tumor and surrogate motion tracking with dynamic MRI for radiation therapy planning.
In this study, we propose a method to simultaneously track the lung tumor and external surrogates to evaluate their spatial correlation in a quantitative way using dynamic MRI, which allows real-time acquisition without ionizing radiation exposure. To capture the lung and whole tumor, four MRI-compatible fiducials are placed on the patient's chest and upper abdomen. Two different types of acquisitions are performed in the sagittal orientation including multi-slice 2D cine MRIs to reconstruct 4D-MRI and two-slice 2D cine MRIs to simultaneously track the tumor and fiducials. A phase-binned 4D-MRI is first reconstructed from ...
Source: Physics in Medicine and Biology - December 15, 2017 Category: Physics Authors: Park S, Farah R, Shea SM, Tryggestad EJ, Hales R, Lee J Tags: Phys Med Biol Source Type: research

Averaged head phantoms from magnetic resonance images of Korean children and young adults.
In this study, we devised a method to build averaged phantom heads by constructing surface and voxel models. The surface model could be used for phantom manipulation, whereas the voxel model could be used for compliance test of specific absorption rate (SAR) for users of mobile phones or other electronic devices. PMID: 29239853 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Han M, Lee AK, Choi HD, Jung YW, Park JS Tags: Phys Med Biol Source Type: research

Experimental verification of stopping-power prediction from single- and dual-energy computed tomography in biological tissues.
h S Abstract An experimental setup for consecutive measurement of ion and x-ray absorption in tissue or other materials is introduced. With this setup using a 3D-printed sample container, the reference stopping-power ratio (SPR) of materials can be measured with an uncertainty of below 0.1%. A total of 65 porcine and bovine tissue samples were prepared for measurement, comprising five samples each of 13 tissue types representing about 80% of the total body mass (three different muscle and fatty tissues, liver, kidney, brain, heart, blood, lung and bone). Using a standard stoichiometric calibration for single-energ...
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Möhler C, Russ T, Wohlfahrt P, Elter A, Runz A, Richter C, Greilich S Tags: Phys Med Biol Source Type: research

Performance of a PTW 60019 microDiamond detector in a 1.5 T MRI-linac.
Abstract Accurate small-field dosimetry is critical for a magnetic resonance linac (MRI-linac). The PTW 60019 microDiamond is close to an ideal detector for small field dosimetry due to its small physical size, high signal-to-noise ratio and approximate water equivalence. It is important to fully characterise the performance of the detector in a 1.5 T magnetic field prior to its use for MRI-linac commissioning and quality assurance. Standard techniques of detector testing have been implemented, or adapted where necessary to suit the capabilities of the MRI-linac. Detector warmup, constancy, dose lineari...
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Woodings SJ, Wolthaus JWH, van Asselen B, de Vries JHW, Kok JGM, Lagendijk JJW, Raaymakers BW Tags: Phys Med Biol Source Type: research

Prediction of breast cancer risk using a machine learning approach embedded with a locality preserving projection algorithm.
This study demonstrated that applying LPP algorithm effectively reduced feature dimensionality, and yielded higher and potentially more robust performance in predicting short-term breast cancer risk. PMID: 29239858 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Heidari M, Zargari Khuzani A, Hollingsworth AB, Danala G, Mirniaharikandehei S, Qiu Y, Liu H, Zheng B Tags: Phys Med Biol Source Type: research

Impact of motion compensation and partial volume correction for 18F-NaF PET/CT imaging of coronary plaque.
In conclusion, we have built and validated a STIR framework incorporating MoCo and PVC for 18F-NaF PET imaging of coronary plaques. First results indicate an improved quantification of plaque-type lesions. PMID: 29240557 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Cal-González J, Tsoumpas C, Lassen ML, Rasul S, Koller L, Hacker M, Schäfers K, Beyer T Tags: Phys Med Biol Source Type: research

A modified microdosimetric kinetic model for relative biological effectiveness calculation.
In this study, a modified MKM was developed, named MMKM. Based on the experimental DSB yield of mammalian cells under the irradiation of ions with different LETs, a RBEDSB (RBE for the induction of DSB)-LET curve was fitted as the correction factor to modify the primary lesion yield in the MKM, and the variation of the primary lesion yield with LET is considered in the MMKM. Compared with the present the MKM, not only the α parameter of the MMKM for mono-energetic ions agree with the experimental data, but also the β parameter varies with LET and the variation trend of the experimental result can be reproduced o...
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Chen Y, Li J, Li C, Qiu R, Wu Z Tags: Phys Med Biol Source Type: research

Fluorescence detection, enumeration and characterization of single circulating cells in vivo: technology, applications and future prospects.
Abstract There are many diseases and biological processes that involve circulating cells in the bloodstream, such as cancer metastasis, immunology, reproductive medicine, and stem cell therapies. This has driven significant interest in new technologies for the study of circulating cells in small animal research models and clinically. Most currently used methods require drawing and enriching blood samples from the body, but these suffer from a number of limitations. In contrast, 'in vivo flow cytometry' (IVFC) refers to set of technologies that allow study of cells directly in the bloodstream of the organism in viv...
Source: Physics in Medicine and Biology - December 14, 2017 Category: Physics Authors: Hartmann C, Patil R, Lin CP, Niedre M Tags: Phys Med Biol Source Type: research

Theoretical analysis of angular distribution of scattering in nozzle components using a response-function method for proton spot-scanning therapy.
Abstract In spot-scanning proton therapy, highly precise beam control is required in the treatment nozzle such that the proton beam does not spread out during transportation by restraining the divergence of the beam angle and spot size, simultaneously. In order to evaluate the beam-broadening behaviour induced by passing through the various nozzle components, we have developed a new method to calculate the angular divergence profile of a proton beam in the nozzle. The angular divergence of the proton beam for each nozzle component is calculated by the Monte Carlo simulation code, Geant4, assuming that the initial ...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Ueda H, Furusaka M, Matsuura T, Hirayama S, Umegaki K Tags: Phys Med Biol Source Type: research

Leveraging multi-layer imager detector design to improve low-dose performance for megavoltage cone-beam computed tomography.
Abstract While megavoltage (MV) cone-beam computed tomography (CBCT) using an electronic portal imaging device (EPID) provides many advantages over kilovoltage (kV) CBCT, clinical adoption is limited by its high doses. Multi-layer imager (MLI) EPIDs increase DQE(0) while maintaining high resolution. However, even well-designed, high-performance MLIs suffer from increased electronic noise from each readout, degrading low-dose image quality. To improve low-dose performance, shift-and-bin addition (ShiBA) imaging is proposed, leveraging the unique architecture of the MLI. ShiBA combines hardware readout-binning and s...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Hu YH, Rottmann J, Fueglistaller R, Myronakis ME, Wang A, Huber P, Shedlock D, Morf D, Baturin P, Star-Lack JM, Berbeco RI Tags: Phys Med Biol Source Type: research

Potential impact of thermal effects during ultrasonic neurostimulation : retrospective numerical estimation of temperature elevation in seven rodent setups.
Abstract In the past decade, a handful but growing number of groups have reported worldwide successful low intensity focused ultrasound induced neurostimulation trials on rodents with effects ranging from movement elicitations to reduction of anesthesia time or reduction of the duration of drug induced seizures. The mechanisms underlying ultrasonic neuromodulation are still not fully understood. Given the low intensities used in most of the studies, a mechanical effect is more likely to be responsible for the neuromodulation effect, but a clear description of the thermal and mechanical effects is necessary to opti...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Constans C, Mateo P, Tanter M, Aubry JF Tags: Phys Med Biol Source Type: research

Optimal transformations leading to normal distributions of positron emission tomography standardized uptake values.
Conclusion: Optimization of the Box-Cox transformation, offers a solution for identifying normal SUV transformations for when the log transformation is insufficient. The log transformation is not always the appropriate transformation for producing normally distributed PET SUVs. PMID: 29235988 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Scarpelli M, Eickhoff J, Cuna E, Perlman S, Jeraj R Tags: Phys Med Biol Source Type: research

Motion vector field phase-to-amplitude resampling for 4D motion-compensated cone-beam CT.
Abstract We propose a phase-to-amplitude resampling (PTAR) method to reduce motion blurring in motion-compensated (MoCo) 4D cone-beam CT (CBCT) image reconstruction, without increasing the computational complexity of the motion vector field (MVF) estimation approach. PTAR is able to improve the image quality in reconstructed 4D volumes including both regular and irregular respiration patterns. The PTAR approach starts with a robust phase gating procedure for the initial MVF estimation and then switches to a phase-adapted amplitude gating method. The switch implies a MVF-resampling, which makes them ampl...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Sauppe S, Kuhm J, Brehm M, Paysan P, Seghers D, Kachelriess M Tags: Phys Med Biol Source Type: research

The fokker-planck equation for coupled brown-neel-rotation.
This article shows how a coupled Fokker--Planck equation can be derived on the basis of coupled Langevin equations. Two physically equivalent Fokker--Planck equations are derived and transformed by means of an appropriate series expansion into a system of ordinary differential equations, which can be solved numerically. Finally, this system is also used to specify a system of differential equations for various limiting cases (Neel, Brown, uniaxial symmetry). Generally, the system exhibits a sparsely populated matrix and can therefore be handled well numerically. . PMID: 29235990 [PubMed - as supplied by publi...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Weizenecker J Tags: Phys Med Biol Source Type: research

Imaging of monochromatic beams by measuring secondary electron bremsstrahlung for carbon-ion therapy using a pinhole X-ray camera.
In conclusion, for both the simulations and experiments, we found that the 25-mm shifts in the Bragg-peak positions can be observed by this method. PMID: 29235991 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Yamaguchi M, Nagao Y, Ando K, Yamamoto S, Sakai M, Parajuli RK, Arakawa K, Kawachi N Tags: Phys Med Biol Source Type: research

Avoiding neuromuscular stimulation in liver irreversible electroporation using radiofrequency electric fields.
rra A Abstract Electroporation based treatments typically consist in applying high voltage dc pulses. As an undesired side effect, these dc pulses cause electrical stimulation of excitable tissues such as motor nerves. In the present in vivo study, it was explored the use of bursts of sinusoidal voltage in the frequency range from 50 kHz to 2 MHz to induce irreversible electroporation (IRE) whilst avoiding neuromuscular stimulation. Series of 100 dc pulses or sinusoidal bursts, both with an individual duration of 100 µs, were delivered to rabbit liver through thin needles in a monopolar electrode configurati...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Castellví Q, Mercadal B, Moll X, Fondevila D, Andaluz A, Ivorra A Tags: Phys Med Biol Source Type: research

Raman micro-spectroscopy analysis of human lens epithelial cells exposed to a low-dose-range of ionizing radiation.
In this study, Raman micro-spectroscopy was used to investigate the effects of varying doses of radiation, ranging from 0.01 Gy to 5 Gy, on human lens epithelial (HLE) cells which were chemically fixed 24 hrs post-irradiation. Raman spectra were acquired from the nucleus and cytoplasm of the HLE cells. Spectra were collected from points in a 3 x 3 grid pattern and then averaged. The raw spectra were preprocessed and principal component analysis followed by linear discriminant analysis (PCA-LDA) was used to discriminate between dose and control for 0.25, 0.5, 2, and 5 Gy. Using leave-one-out cross-validation (LOOCV) accurac...
Source: Physics in Medicine and Biology - December 13, 2017 Category: Physics Authors: Allen CH, Kumar A, Qutob S, Nyiri BJ, Chauhan V, Murugkar S Tags: Phys Med Biol Source Type: research

Assessment of global and local region-based bilateral mammographic feature asymmetry to predict short-term breast cancer risk.
This study aims to develop and test a new imaging marker-based short-term breast cancer risk prediction model. An age-matched dataset of 566 screening mammography cases was used. All "prior" images acquired in the two screening series were negative, while in the "current" screening images, 283 cases were positive for cancer and 283 cases remained negative. For each case, two bilateral cranio-caudal view mammograms acquired from the "prior" negative screenings were selected and processed by a computer-aided image processing scheme, which segmented the entire breast area into 9 strip-based local...
Source: Physics in Medicine and Biology - December 11, 2017 Category: Physics Authors: Li Y, Fan M, Cheng H, Zhang P, Zheng B, Li L Tags: Phys Med Biol Source Type: research

Prediction of radiation necrosis in a rodent model using magnetic resonance imaging apparent transverse relaxation (R < sub > 2 < /sub > < sup > * < /sup > ).
Conclusions: The ability to predict areas of RN and increases of R2* within the hippocampus provides a method for long-term monitoring and prediction of RN. PMID: 29219117 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 8, 2017 Category: Physics Authors: Belliveau JG, Jensen MD, Stewart JMP, Solovey I, Klassen ML, Bauman GS, Menon RS Tags: Phys Med Biol Source Type: research

Density overwrites of internal tumor volumes in intensity modulated proton therapy plans for mobile lung tumors.
Abstract The purpose of this study was to investigate Internal Tumor Volume (ITV) density overwrite strategies to minimize Intensity Modulated Proton Therapy (IMPT) plan degradation of mobile lung tumors. Four planning paradigms were compared for nine lung cancer patients. IGTV and ICTV structures were defined encompassing their respective volumes in every 4DCT phase. The paradigms use different planning CT (pCT) created from the Average Intensity Projection (AIP) of the 4DCT, overwriting the density within the IGTV to account for movement. The density overwrites were: a) constant filling with 100 HU (C100) o...
Source: Physics in Medicine and Biology - December 8, 2017 Category: Physics Authors: Botas P, Grassberger C, Sharp G, Paganetti H Tags: Phys Med Biol Source Type: research

3D-printed adaptive acoustic lens as a disruptive technology for transcranial ultrasound therapy using single-element transducers.
Abstract The development of multi-element arrays for better control of the shape of ultrasonic beams has opened the way for focusing through highly aberrating media, such as the human skull. As a result, the use of brain therapy with transcranial-focused ultrasound has rapidly grown. Although effective, such technology is expensive. We propose a disruptive, low-cost approach that consists of focusing a 1-MHz ultrasound beam through a human skull with a single-element transducer coupled with a tailored silicone acoustic lens cast in a 3D-printed mold and designed using computed tomography-based numerical acoustic s...
Source: Physics in Medicine and Biology - December 8, 2017 Category: Physics Authors: Maimbourg G, Houdouin A, Deffieux T, Tanter M, Aubry JF Tags: Phys Med Biol Source Type: research

Electron beam collimation with the photon MLC for standard electron treatments.
In conclusion, treatment plans using cut-out collimation can be replaced by plans of similar treatment plan quality using pMLC collimation with accurately calculated dose distributions. PMID: 29214984 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 7, 2017 Category: Physics Authors: Mueller S, Fix MK, Henzen D, Frei D, Frauchiger D, Loessl K, Stampanoni MFM, Manser P Tags: Phys Med Biol Source Type: research

Non-invasive peripheral nerve stimulation via focused ultrasound < i > in vivo < /i > .
Non-invasive peripheral nerve stimulation via focused ultrasound in vivo. Phys Med Biol. 2017 Dec 07;: Authors: Downs ME, Lee SA, Yang G, Kim S, Wang Q, Konofagou EE Abstract Focused ultrasound (FUS) has been employed on a wide range of clinical applications to safely and non-invasively achieve desired effects that have previously required invasive and lengthy procedures with conventional methods. Conventional electrical neuromodulation therapies that are applied to the peripheral nervous system (PNS) are invasive and/or non-specific. Recently, focused ultrasound has demonstrated the ability to modula...
Source: Physics in Medicine and Biology - December 7, 2017 Category: Physics Authors: Downs ME, Lee SA, Yang G, Kim S, Wang Q, Konofagou EE Tags: Phys Med Biol Source Type: research

Computer-aided assessment of breast density: Comparison of supervised deep learning and feature based statistical learning.
In this study, our purpose was to develop a supervised deep learning approach for automated estimation of percentage density (PD) on digital mammograms (DM). The input "for processing" DM was first log-transformed, enhanced by a multi-resolution preprocessing scheme, and subsampled to a pixel size of 800µm×800µm from 100µm×100µm. A deep convolutional neural network (DCNN) was trained to estimate a probability map of breast density (PMD) by using a domain adaptation resampling method. The PD was estimated as the ratio of the dense area to the breast area based on the PMD. The DC...
Source: Physics in Medicine and Biology - December 6, 2017 Category: Physics Authors: Li S, Wei J, Chan HP, Helvie MA, Roubidoux MA, Lu Y, Zhou C, Hadjiiski LM, Samala RK Tags: Phys Med Biol Source Type: research

Effect of static scatterers in laser speckle contrast imaging: an experimental study on correlation and contrast.
Abstract Laser speckle contrast imaging (LSCI) is a non-invasive microvascular blood flow assessment technique with good temporal and spatial resolutions. Most LSCI systems, including commercials devices, can only perform qualitative blood flow evaluation which is a major limitation of this technique. There are several factors that prevent LSCI to be a quantitative technique. Among these factors we can highlight the effect of static scatterers. The goal of this work was to study the influence of different static and dynamic scatterers concentrations on laser speckle correlation and contrast. In order to achieve th...
Source: Physics in Medicine and Biology - December 5, 2017 Category: Physics Authors: Vaz PG, Humeau-Heurtier A, Figueiras E, Correia C, Cardoso JMR Tags: Phys Med Biol Source Type: research

Numerical implementation of magneto-acousto-electric tomography (MAET) using a linear phased array transducer.
In this study, the performance and implementation of magneto-acousto-electric tomography (MAET) is investigated using a linear phased array (LPA) transducer. The goal of MAET is to image the conductivity distribution in biological bodies. It uses the interaction between ultrasound and a static magnetic field to generate velocity current density distribution inside the body. The resultant voltage due to velocity current density is sensed by surface electrodes attached on the body. In this study, the theory of MAET is reviewed. A 16-element LPA transducer is used to provide beam directivity and steerability of acoustic waves...
Source: Physics in Medicine and Biology - December 5, 2017 Category: Physics Authors: Gözü MS, Zengin R, Gencer NG Tags: Phys Med Biol Source Type: research

Evaluation of latent variances in Monte Carlo dose calculations with varian TrueBeam photon phase-spaces used as a particle source.
Conclusions:&lt;/b&gt; In order to achieve sub-percent latent variance in open 10x10 cm&lt;sup&gt;2&lt;/sup&gt; field MC simulations single PSF can be used, whereas for small SRS fields more PSFs would have to be summed. PMID: 29205177 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 5, 2017 Category: Physics Authors: Alhakeem EA, Zavgorodni SF Tags: Phys Med Biol Source Type: research

Interval-based reconstruction for uncertainty quantification in PET.
Abstract A new directed interval-based tomographic reconstruction algorithm, called Non-additive Interval Based Expectation Maximization (NIBEM) is presented. It uses non-additive modeling of the forward operator that provides intervals instead of single-valued projections. The detailed approach is an extension of the Maximum Likelihood - Expectation Maximization (ML-EM) algorithm based on intervals. The main motivation for this extension is that the resulting intervals have appealing properties for estimating the statistical uncertainty associated with the reconstructed activity values. After reviewing previously...
Source: Physics in Medicine and Biology - December 1, 2017 Category: Physics Authors: Kucharczak F, Loquin K, Buvat I, Strauss O, Mariano-Goulart D Tags: Phys Med Biol Source Type: research

Reply to Comment on 'egs_brachy: a versatile and fast Monte Carlo code for brachytherapy'.
Abstract We respond to the comments by Dr. Yegin by identifying the source of an error in a fit in our original paper but arguing that the lack of a fit does not affect the conclusion based on the raw data that egs_brachy is an accurate code and we provide further benchmarking data to demonstrate this point. PMID: 29192606 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - December 1, 2017 Category: Physics Authors: Thomson RM, Taylor REP, Chamberland MJP, Rogers DWO Tags: Phys Med Biol Source Type: research

Comment on 'egs_brachy: a versatile and fast Monte Carlo code for brachytherapy'.
Abstract In a recent paper (Chamberland et al, 2016) develop a new Monte Carlo code called egs_brachy for brachytherapy treatments. It is based on EGSnrc and written in C++ programming language. In order to benchmark the egs_brachy code, the authors use it in various test case scenarios in which complex geometry conditions are exist. Another EGSnrc based brachytherapy dose calculation engine BrachyDose is used for dose comparisons. The authors fail to prove that egs_brachy can produce reasonable dose values for brachytherapy sources in a given medium. The dose comparisons in the paper are erroneous and ...
Source: Physics in Medicine and Biology - December 1, 2017 Category: Physics Authors: Yegin G Tags: Phys Med Biol Source Type: research

Quantifying the radiant exposure and effective dose in patients treated for actinic keratoses with topical photodynamic therapy using daylight and LED white light.
Abstract Daylight photodynamic therapy (dl-PDT) is as effective as conventional PDT (c-PDT) for treating actinic keratoses but has the advantage of reducing patient discomfort significantly. Topical dl-PDT and white light-PDT (wl-PDT) differ from c-PDT by way of light sources and methodology. We measured the variables associated with light dose delivery to skin surface and influence of geometry using a radiometer, a spectral radiometer and an illuminance meter. The associated errors of the measurement methods were assessed. The spectral and spatial distribution of the radiant energy from the LED white light source...
Source: Physics in Medicine and Biology - December 1, 2017 Category: Physics Authors: Manley M, Collins P, Gray L, O'Gorman S, McCavana J Tags: Phys Med Biol Source Type: research

Recent Time Trends and Predictors of Heart Dose From Breast Radiation Therapy in a Large Quality Consortium of Radiation Oncology Practices.
Abstract PURPOSE: Limited data exist regarding the range of heart doses received in routine practice with radiation therapy (RT) for breast cancer in the United States today and the potential effect of the continual assessment of the cardiac dose on practice patterns. METHODS AND MATERIALS: From 2012 to 2015, 4688 patients with breast cancer treated with whole breast RT at 20 sites participating in a state-wide consortium were enrolled into a registry. The importance of limiting the cardiac dose has been emphasized in the consortium since 2012, and the mean heart dose (MHD) has been reported by each instituti...
Source: Physics in Medicine and Biology - December 1, 2017 Category: Physics Authors: Pierce LJ, Feng M, Griffith KA, Jagsi R, Boike T, Dryden D, Gustafson GS, Benedetti L, Matuszak MM, Nurushev TS, Haywood J, Radawski JD, Speers C, Walker EM, Hayman JA, Moran JM, Michigan Radiation Oncology Quality Consortium Tags: Int J Radiat Oncol Biol Phys Source Type: research

Block matching sparsity regularization-based image reconstruction for incomplete projection data in computed tomography.
Abstract In medical imaging fields, many of the conventional regularization meth-ods, such as total variation or total generalized variation, impose strong prior assumptions on images which can only account for very limited classes of im-ages. A more reasonable sparse representation frame for images is still in strong need. Visually understandable images contain meaningful patterns and the combinations or collections of these patterns can be utilized to form some sparse and redundant representations which can promisingly facilitate image reconstructions. In this work, we propose and study the block matching spar-s...
Source: Physics in Medicine and Biology - November 30, 2017 Category: Physics Authors: Cai A, Li L, Zheng Z, Zhang H, Wang L, Hu G, Yan B Tags: Phys Med Biol Source Type: research

PSF reconstruction for Compton-based prompt gamma imaging.
In this study, we investigate the performance of the list-mode ordered subset expectation maximization algorithm with a shift-variant point spread function model (LM-OSEM-SV-PSF). We also evaluate how well the PG images reconstructed using a SV-PSF model reproduce the distal falloff of the proton beam. SV-PSF parameters were estimated by simulation data of point sources at various positions. Simulated PGs were produced in a water phantom irradiated with a proton beam. Compared to the LM-OSEM algorithm, the LM-OSEM-SV-PSF algorithm improved the quality of the reconstructed PG images and the estimation of PG falloff position...
Source: Physics in Medicine and Biology - November 30, 2017 Category: Physics Authors: Jan ML, Lee MW, Huang HM Tags: Phys Med Biol Source Type: research

Terahertz spectral unmixing based method for identifying gastric cancer.
In this study, based on a modified hard modeling factor analysis (HMFA) method, terahertz spectral unmixing was applied to investigate the relationships between the absorption spectra in terahertz time-domain spectroscopy (THz-TDS) and certain biomarkers of gastric cancer in order to systematically identify gastric cancer. A probability distribution and box plot were used to extract the distinctive peaks that indicate carcinogenesis, and the corresponding weight distributions were used to discriminate the tissue types. The results of this work indicate that terahertz techniques have the potential to detect different levels...
Source: Physics in Medicine and Biology - November 29, 2017 Category: Physics Authors: Cao Y, Huang P, Li X, Ge W, Hou D, Zhang G Tags: Phys Med Biol Source Type: research

Objective image characterization of a spectral CT scanner with dual-layer detector.
Abstract This work evaluated the performance of a detector-based spectral CT system by obtaining objective reference data, evaluating attenuation response of iodine and accuracy of iodine quantification, and comparing conventional CT and virtual monoenergetic images in three common phantoms. Scanning was performed using the hospital's clinical adult body protocol. Modulation transfer function (MTF) was calculated for a tungsten wire and visual line pair targets were evaluated. Image noise power spectrum (NPS) and pixel standard deviation were calculated. MTF for monoenergetic images agreed with conventio...
Source: Physics in Medicine and Biology - November 29, 2017 Category: Physics Authors: Ozguner O, Dhanantwari A, Halliburton S, Wen G, Utrup S, Jordan DW Tags: Phys Med Biol Source Type: research

Fixed forced detection for fast SPECT Monte-Carlo simulation.
Abstract Monte-Carlo simulations of SPECT images are notoriously slow to converge due to the large ratio between the number of photons emitted and detected in the collimator. This work proposes a method to accelerate the simulations based on Fixed Forced Detection (FFD) combined with an analytical response of the detector. FFD is based on a Monte-Carlo simulation but forces the detection of a photon in each detector pixel weighted by the probability of emission (or scattering) and transmission to this pixel. The method was evaluated with numerical phantoms and on patient images. ...
Source: Physics in Medicine and Biology - November 29, 2017 Category: Physics Authors: Cajgfinger T, Rit S, Letang JM, Halty A, Sarrut D Tags: Phys Med Biol Source Type: research

Anatomically realistic ultrasound phantoms using gel wax with 3D printed moulds.
Abstract Here we describe methods for creating tissue-mimicking ultrasound phantoms based on patient anatomy using a soft material called gel wax. To recreate acoustically realistic tissue properties, two additives to gel wax were considered: paraffin wax to increase acoustic attenuation, and solid glass spheres to increase backscattering. The frequency dependence of ultrasound attenuation was well described with a power law over the measured range of 3 to 10 MHz. With the addition of paraffin wax in concentrations of 0 to 8 w/w%, attenuation varied from 0.72 to 2.91 dB/cm at 3 MHz and from 6.84 to 26.63 dB/cm at ...
Source: Physics in Medicine and Biology - November 29, 2017 Category: Physics Authors: Maneas E, Xia W, Nikitichev DI, Daher B, Manimaran M, Wong RYJ, Chang CW, Rahmani B, Capelli C, Schievano S, Burriesci G, Ourselin S, David AL, Finlay M, West SJ, Vercauteren T, Desjardins AE Tags: Phys Med Biol Source Type: research

PET attenuation correction for flexible MRI surface coils in hybrid PET/MRI using a 3D depth camera.
fers KP Abstract PET attenuation correction for flexible MRI radio frequency surface coils in hybrid PET/MRI is still a challenging task, as position and shape of these coils conform to large inter-patient variabilities. The purpose of this feasibility study is to develop a novel method for the incorporation of attenuation information about flexible surface coils in PET reconstruction using the Microsoft Kinect V2 depth camera. The depth information is used to determine a dense point cloud of the coil's surface representing the shape of the coil. From a CT template - acquired once in advance - surface i...
Source: Physics in Medicine and Biology - November 29, 2017 Category: Physics Authors: Frohwein LJ, Hess M, Schlicher D, Bolwin K, Büther F, Jiang X, Schäfers KP Tags: Phys Med Biol Source Type: research