The role of multiple ionization of H < sub > 2 < /sub > O in heavy ion collisions.
The role of multiple ionization of H2O in heavy ion collisions. Phys Med Biol. 2019 Sep 05;: Authors: Bachi N, Otranto S, Otero GS, Olson RE Abstract Collisional ionization processes involving H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O molecules and C&amp;lt;sup&amp;gt;6+&amp;lt;/sup&amp;gt;, O&amp;lt;sup&amp;gt;8+&amp;lt;/sup&amp;gt;, Si&amp;lt;sup&amp;gt;13+&amp;lt;/sup&amp;gt; ions are studied by means of the classical trajectory Monte Carlo method using molecular orbital calculations to define the ionization stages of the water molecu...
Source: Physics in Medicine and Biology - September 5, 2019 Category: Physics Authors: Bachi N, Otranto S, Otero GS, Olson RE Tags: Phys Med Biol Source Type: research

Evaluation of a deep learning-based pelvic synthetic CT generation technique for MRI-based prostate proton treatment planning.
Abstract The purpose of this work is to validate the application of a deep learning-based method for pelvic synthetic CT (sCT) generation that can be used for prostate proton beam therapy treatment planning. We propose to integrate dense block minimization into 3D cycle-consistent generative adversarial networks (cycle GAN) framework to effectively learn the nonlinear mapping between MRI and CT pairs. A cohort of 17 patients with co-registered CT and MR pairs were used to test the deep learning-based sCT generation method by leave-one-out cross-validation. Image quality between the sCT and CT images, gamma analysi...
Source: Physics in Medicine and Biology - September 5, 2019 Category: Physics Authors: Liu Y, Lei Y, Wang Y, Shafai-Erfani G, Wang T, Tian S, Patel P, Jani AB, McDonald M, Curran WJ, Liu T, Zhou J, Yang X Tags: Phys Med Biol Source Type: research

Dense motion propagation from sparse samples.
Abstract There are many applications for which sparse, or partial sampling of&amp;#13; dynamic image data can be used for articulating or estimating motion within the&amp;#13; medical imaging area. In this new work, we propose a generalized framework for&amp;#13; dense motion propagation from sparse samples which represents an example of transfer&amp;#13; learning and manifold alignment, allowing the transfer of knowledge across imaging&amp;#13; sources of different domains which exhibit different features. Many such examples&amp;#13; exist in medical imaging, from mapping 2D ultrasound or ...
Source: Physics in Medicine and Biology - September 5, 2019 Category: Physics Authors: Smith RL, Dasari P, Lindsay C, King MA, Wells K Tags: Phys Med Biol Source Type: research

Trimmer sequencing time minimization during dynamically collimated proton therapy using a colony of cooperating agents.
Abstract The dynamic collimation system (DCS) can be combined with pencil beam scanning proton therapy to deliver highly conformal treatment plans with unique collimation at each energy layer. This energy layer-specific collimation is accomplished through the synchronized motion of four trimmer blades that intercept the proton beam near the target boundary in the beam's eye view. However, the corresponding treatment deliveries come at the cost of additional treatment time since the translational speed of the trimmer is slower than the scanning speed of the proton pencil beam. In an attempt to minimize the addition...
Source: Physics in Medicine and Biology - September 4, 2019 Category: Physics Authors: Smith BR, Hyer DE, Flynn RT, Hill PM, Culberson WS Tags: Phys Med Biol Source Type: research

A column generation heuristic for VMAT planning with adaptive CVaR constraints.
In this study we develop an efficient computational procedure that generates medically acceptable treatment plans for volumetric modulated arc therapy with constant gantry speed. Our proposed method is a column generation heuristic based on a mixed integer linear programming model, where the objective function contains minimization of total monitor unit of the treatment plan and dose-volume requirements are included as conditional value-at-risk constraints. Our heuristic generates a full treatment arc for the restricted master problem and calibrates the right hand side parameters of the conditional value-at-risk constraint...
Source: Physics in Medicine and Biology - September 4, 2019 Category: Physics Authors: Dursun P, Taşkın ZC, Altınel IK, Bilge H, Donmez Kesen N, Okutan M, Oral EN Tags: Phys Med Biol Source Type: research

Single patient convolutional neural networks for real-time MR reconstruction: A proof of concept application in lung tumor segmentation for adaptive radiotherapy.
Conclusions: We have shown that 3D CNNs can be used for real-time on-the-fly dynamic image reconstruction utilizing both spatial and temporal data in this proof of concept study. We evaluated the technique using six retrospectively undersampled lung cancer patient data sets, as well as prospectively undersampled data acquired from a volunteer and motion phantom. The reconstruction speed achieved for our current implementation was 65 ms per image. &amp;#13; &amp;#13. PMID: 31476750 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - September 2, 2019 Category: Physics Authors: Dietz B, Yun J, Yip E, Gabos Z, Fallone BG, Wachowicz K Tags: Phys Med Biol Source Type: research

Towards continuous-to-continuous 3D imaging in the real world.
Abstract Imaging systems are often modeled as continuous-to-discrete mappings that map the object (i.e., a function of continuous variables such as space, time, energy, wavelength, etc.) to a finite set of measurements. When it comes to reconstruction, some discretized version of the object is almost always assumed, leading to a discrete-to-discrete representation of the imaging system. In this paper, we discuss a method for single photon emission computed tomography (SPECT) imaging that avoids discrete representations of the object or the imaging system, thus allowing reconstruction on an arbitrarily fine set of ...
Source: Physics in Medicine and Biology - August 30, 2019 Category: Physics Authors: Caucci L, Liu Z, Jha AK, Han H, Furenlid LR, Barrett HH Tags: Phys Med Biol Source Type: research

Generative adversarial networks (GAN) for compact beam source modelling in Monte Carlo simulations.
Abstract A method is proposed and evaluated to model large and inconvenient phase space files used in Monte Carlo simulations by a compact Generative Adversarial Network (GAN). The GAN is trained based on a phase space dataset to create a neural network, called Generator (G), allowing G to mimic the multidimensional data distribution of the phase space. At the end of the training process, G is stored with about 0.5 million weights, around 10\,MB, instead of few GB of the initial file. Particles are then generated with G to replace the phase space dataset.&amp;#13; &amp;#13; This concept is applied to beam ...
Source: Physics in Medicine and Biology - August 30, 2019 Category: Physics Authors: Sarrut D, Krah N, Letang JM Tags: Phys Med Biol Source Type: research

Integration of dynamic contrast-enhanced magnetic resonance imaging and T2-weighted imaging radiomic features by a canonical correlation analysis-based feature fusion method to predict histological grade in ductal breast carcinoma.
Abstract Tumour histological grade has prognostic implications in breast cancer. Tumour features in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and T2-weighted (T2W) imaging can provide related and complementary information in the analysis of breast lesions to improve MRI-based histological status prediction in breast cancer. A dataset of 167 patients with invasive ductal carcinoma (IDC) was assembled, consisting of 72 low/intermediate-grade and 95 high-grade cases with preoperative DCE-MRI and T2W images. The data cohort was separated into development (n=111) and validation (n=56) cohorts. Each...
Source: Physics in Medicine and Biology - August 30, 2019 Category: Physics Authors: Fan M, Liu Z, Xie S, Xu M, Wang S, Gao X, Li L Tags: Phys Med Biol Source Type: research

4D Monte Carlo dose calculations for pre-treatment quality assurance of VMAT SBRT: a phantom-based feasibility study.
This study has demonstrated the feasibility of this 4DMC method. PMID: 31470421 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 30, 2019 Category: Physics Authors: Roberts NF, Williams M, Holloway L, Metcalfe P, Oborn BM Tags: Phys Med Biol Source Type: research

Deep-learning assisted automatic digitization of interstitial needles in 3D CT image based high dose-rate brachytherapy of gynecological cancer.
Abstract Digitization of interstitial needles is a complicated and tedious process for the treatment planning of 3D CT image based interstitial high dose-rate brachytherapy (HDRBT) of gynecological cancer. We developed a deep-learning assisted auto-digitization method for interstitial needles. The digitization method consisted of two steps. The first step used a deep neural network with a U-net structure to segment all needles from CT images. The second step simultaneously clustered the segmented voxels into different needle groups and generated the needle central trajectories by solving an optimization problem. W...
Source: Physics in Medicine and Biology - August 30, 2019 Category: Physics Authors: Jung H, Shen C, Gonzalez Y, Albuquerque K, Jia X Tags: Phys Med Biol Source Type: research

Cascaded systems analysis of anatomic noise in digital mammography and dual-energy digital mammography.
Abstract In x-ray based imaging of the breast, contrast between fibroglandular (Fg) tissue and adipose (Ad) tissue is a source of anatomic noise. The goal of this work was to validate by simulation and experiment a mathematical framework for modelling the Fg component of anatomic noise in digital mammograpy (DM) and dual-energy (DE) DM. Our mathematical framework unifies and generalizes existing approaches. We compared mathematical predictions directly with empirical measurements of the anatomic noise power spectrum of the CIRS BR3D structured breast phantom using two clinical mammography systems and four beam qua...
Source: Physics in Medicine and Biology - August 30, 2019 Category: Physics Authors: Tanguay J, Lalonde R, Bjarnason TA, Yang CJ Tags: Phys Med Biol Source Type: research

Breast phantoms for 2D digital mammography with realistic anatomical structures and attenuation characteristics based on clinical images using 3D printing.
In conclusion, an approach to produce anthropomorphic breast phantoms for DM offering realistic anatomical structures and attenuation characteristics based on clinical images was successfully developed. As shown, the phantom realistically simulated the original female breast. Therefore, it is to expect that such phantoms are promising to support bridging the gap between physical-technical and diagnostic image quality assessment. In addition, they enable a variety of practical and scientific applications for which present technical phantoms are not suitable. PMID: 31469105 [PubMed - as supplied by publisher] (Source: P...
Source: Physics in Medicine and Biology - August 29, 2019 Category: Physics Authors: Schopphoven S, Cavael P, Bock K, Fiebich M, Mäder U Tags: Phys Med Biol Source Type: research

Personalized kidney dosimetry in 177Lu-octreotate treatment of neuroendocrine tumours: a comparison of kidney dosimetry estimates based on a whole organ and small volume segmentations.
Abstract Peptide receptor radionuclide therapy (PRRT) with 177Lu- radiolabeled octreotate is an effective treatment method for inoperable neuroendocrine tumours (NETs). There is growing evidence that estimates of the organ-at-risks (OARs) doses are necessary for the optimization of personalized PRRT (P-PRRT). Dosimetry, however, requires a complicated and time-consuming procedure, which hinders its implementation in the clinic. The aim of this study is to develop a practical and automatic technique to simplify personalized dosimetry of kidney, the major OAR in 177Lu P-PRRT. The data from 30 NETs patients undergoin...
Source: Physics in Medicine and Biology - August 28, 2019 Category: Physics Authors: Hou X, Zhao W, Beauregard JM, Celler A Tags: Phys Med Biol Source Type: research

Characterization of dynamic collimation mechanisms for helical CT scans with direct measurements.
Conclusion: &amp;#13; With direct measurements of primary x-ray beam coverage, dynamic collimation mechanisms and related dose reduction effects were characterized for four modern wide-beam CT scanners. PMID: 31461411 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 27, 2019 Category: Physics Authors: Yang K, Li Z, Li X, Liu B Tags: Phys Med Biol Source Type: research

ReconSocket: a low-latency raw data streaming interface for real-time MRI-guided radiotherapy.
Abstract With the recent advent of hybrid MRI-guided radiotherapy systems, continuous intra-fraction MR imaging for motion monitoring has become feasible. The ability to perform real-time custom image reconstructions is however often lacking. In this work we present a low-latency streaming solution, ReconSocket, which provides a real-time stream of k-space data from the MRI to custom reconstruction servers. &amp;#13; &amp;#13; We determined the performance of the data streaming by measuring the streaming latency (i.e., non-zero time delay due to data transfer and processing) and jitter (i.e., deviations fr...
Source: Physics in Medicine and Biology - August 27, 2019 Category: Physics Authors: Borman PTS, Raaymakers BW, Glitzner M Tags: Phys Med Biol Source Type: research

Optimal energy selection for proton stopping-power-ratio estimation using dual-energy CT-based monoenergetic imaging.
In this study, we revisited the idea of coupling the stoichiometric calibration method with virtual monoenergetic CT datasets (MonoCT) generated by modern DECT scanners, because of its readiness for implementation with the existing TPS. Our objective was to determine the optimal energy of the MonoCT dataset for stoichiometric calibration and estimate the overall uncertainty in SPR estimation at the optimal energy. We performed stoichiometric calibration for MonoCT datasets across the energy range available on a Siemens Force DECT scanner and a Philips IQon DECT scanner in a 10 keV step. We estimated the uncertainties of di...
Source: Physics in Medicine and Biology - August 22, 2019 Category: Physics Authors: Je E, Lee HH, Duan X, Li B, Jia X, Yang M Tags: Phys Med Biol Source Type: research

On the conversion from dose-to-medium to dose-to-water in heterogeneous phantoms with Acuros XB and Monte Carlo calculations.
Abstract The method implemented in Monte Carlo (MC) algorithm to convert dose-to-medium (Dm) to dose-to-water (Dw) is usually based on the Bragg-Gray cavity theory. Acuros XB (AXB) reports also Dm and Dw but the method to calculate Dw is based on the energy deposition cross sections for water in place of those for the local media. For both algorithms, the calculation of Dw in non-water media is similar to the dose received in a small volume of water, small enough not to disturb the fluence of charged particles. Recently, two new methods revised the Bragg-Gray cavity theory, one proposed by Andreo and the other by ...
Source: Physics in Medicine and Biology - August 22, 2019 Category: Physics Authors: Delbaere A, Younes T, Vieillevigne L Tags: Phys Med Biol Source Type: research

Gradient regularized convolutional neural networks for low-dose CT image enhancement.
Abstract The potential risks of x-ray to patients have transferred the public's attention from normal dose CT (NDCT) to low-dose CT (LDCT). However, simply lowering the radiation dose of the CT system will significantly degrade the quality of CT images such as noise and artifacts, which compromises the diagnostic performance. Hence, various methods have been proposed to solve this problem over the past decades. Although these methods have achieved impressive results, they also suffer from a drawback of smoothing image details after denoising, which makes it difficult for clinical diagnosis and treatment. To addres...
Source: Physics in Medicine and Biology - August 21, 2019 Category: Physics Authors: Gou S, Liu W, Jiao C, Liu H, Gu Y, Zhang X, Lee J, Jiao L Tags: Phys Med Biol Source Type: research

Polynomial modelling of proton trajectories in homogeneous media for fast most likely path estimation and trajectory simulation.
Abstract Protons undergo many small angle deflections when traversing a medium, such as a patient. This effect, known as multiple Coulomb scattering (MCS), leads to degraded image resolution in proton radiography and computed tomography (CT) and to lateral spreading of the dose distribution in proton therapy. To optimally account for MCS in proton imaging, the most likely path (MLP) of a proton is estimated based on its position and propagation angle measured in front of and behind the object. In this work, we propose a functional which quantifies the likelihood of a proton trajectory and study how it can be used ...
Source: Physics in Medicine and Biology - August 20, 2019 Category: Physics Authors: Krah N, Letang JM, Rit S Tags: Phys Med Biol Source Type: research

Faster PET reconstruction with non-smooth priors by randomization and preconditioning.
CB Abstract Uncompressed clinical data from modern positron emission tomography (PET) scanners are very large, exceeding 350 million data points (projection bins). The last decades have seen tremendous advancements in mathematical imaging tools many of which lead to non-smooth (i.e. non-differentiable) optimization problems which are much harder to solve than smooth optimization problems. Most of these tools have not been translated to clinical PET data, as the state-of-the-art algorithms for non- smooth problems do not scale well to large data. In this work, inspired by big data machine learning applications, we...
Source: Physics in Medicine and Biology - August 20, 2019 Category: Physics Authors: Ehrhardt MJ, Markiewicz PJ, Schönlieb CB Tags: Phys Med Biol Source Type: research

IPEM Topical Report: An evidence and risk assessment based analysis of the efficacy of quality assurance tests on fluoroscopy units - part I; dosimetry and safety.
Abstract This work aims to assess the efficacy of x-ray quality assurance tests undertaken on fluoroscopy units in the UK. Information was gathered on the results of dosimetry and safety tests recommended by the reports of the Institute of Physics and Engineering in Medicine, and those additionally undertaken by medical physics departments. The assessment of efficacy considers the frequency with which a test result breaches the remedial level or other relevant threshold where applicable. The third quartile of those results exceeding the remedial level or threshold is used to estimate the severity of such a breach ...
Source: Physics in Medicine and Biology - August 19, 2019 Category: Physics Authors: Worrall M, Shaw D, Baker C, Charnock P, Fazakerley J, Honey I, Iball GR, Koutalonis M, Price M, Renaud C, Rose A, Wood TJ Tags: Phys Med Biol Source Type: research

A compressed sensing approach to immobilized nanoparticle localization for superparamagnetic relaxometry.
Abstract Superparamagnetic relaxometry (SPMR) exploits the unique magnetic properties of targeted superparamagnetic iron oxide nanoparticles to detect small numbers of cancer cells. Reconstruction of the spatial distribution of cancer-bound nanoparticles requires solving an ill-posed inverse problem. The current method, Multiple Source Analysis (MSA), uses a least-squares fit to determine the strength and location of a pre-determined number of magnetic dipoles. In this proof-of-concept study, we propose the application of a sparsity averaged reweighting algorithm (SARA) for volumetric reconstruction of immobilized...
Source: Physics in Medicine and Biology - August 19, 2019 Category: Physics Authors: Thrower SL, Kandala S, Fuentes D, Stefan W, Sowko NJ, Huang MX, Mathieu KB, Hazle JD Tags: Phys Med Biol Source Type: research

Automatic image-domain Moir é artifact reduction method in grating-based x-ray interferometry imaging.
In this study, we propose to automatically remove Moiré image artifact induced by system instabilities in grating-based x-ray interferometry imaging using convolutional neural network (CNN) technique. This method reduces Moiré image artifact in image-domain via a learned image post-processing procedure, rather than developing signal retrieval optimization algorithms to minimize the inconsistencies between acquired phase stepping data and assumed signal model. To achieve this aim, we train the CNN network using numerical dataset synthesized from both natural images and experimentally acquired Moiré arti...
Source: Physics in Medicine and Biology - August 19, 2019 Category: Physics Authors: Chen J, Zhu J, Li Z, Shi W, Zhang Q, Hu Z, Zheng H, Liang D, Ge Y Tags: Phys Med Biol Source Type: research

Optimizing robot motion for robotic ultrasound-guided radiation therapy.
aefer A Abstract An important aspect of robotic radiation therapy is active compensation of target motion. Recently, ultrasound has been proposed to obtain real-time volumetric images of abdominal organ motion. One approach to realize flexible probe placement throughout the treatment fraction is based on a robotic arm holding the ultrasound probe. However, the probe and the robot holding it may obstruct some of the beams with a potentially adverse effect on the plan quality. This can be mitigated by using a kinematically redundant robot, which allows maintaining a steady pose of the ultrasound probe while moving i...
Source: Physics in Medicine and Biology - August 19, 2019 Category: Physics Authors: Schlüter M, Fürweger C, Schlaefer A Tags: Phys Med Biol Source Type: research

Ensemble of neural networks for 3D position estimation in monolithic PET detectors.
Visvikis D Abstract We propose an ensemble of multilayer feedforward neural networks to estimate the 3D position of photon interactions in monolithic detectors. The ensemble is trained with data generated from optical Monte Carlo simulations only. The originality of our approach is to exploit simulations to obtain reference data, in combination with a variability reduction that the network ensembles offer, thus, removing the need of extensive per-detector calibration measurements. This procedure delivers an ensemble valid for any detector of the same design. We show the capability of the ensemble to solve the 3D ...
Source: Physics in Medicine and Biology - August 15, 2019 Category: Physics Authors: Iborra A, González Martínez AJ, Gonzalez-Montoro A, Bousse A, Visvikis D Tags: Phys Med Biol Source Type: research

Monte Carlo calculation of beam quality correction factors in proton beams using PENH.
pin E Abstract This work calculates beam quality correction factors (&amp;lt;i&amp;gt;k&amp;lt;sub&amp;gt;Q&amp;lt;/sub&amp;gt;&amp;lt;/i&amp;gt;) in both modulated and unmodulated proton beams using the Monte Carlo code PENH. The latest ICRU 90 recommendations on key data for ionizing-radiation dosimetry were adopted to calculate the electronic stopping powers and to select the mean energy to create an ion pair in dry air (&amp;lt;i&amp;gt;W&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;air&amp;lt;/sub&amp;gt;). For modulated proton beams, &amp;lt;i&am...
Source: Physics in Medicine and Biology - August 15, 2019 Category: Physics Authors: Gomà C, Sterpin E Tags: Phys Med Biol Source Type: research

Optical simulation study on the spatial resolution of a thick monolithic PET detector.
This study demonstrates the ultimate spatial resolution that can be obtained with this detector without being constrained by practical limitations of experimental setups. In the future these optical simulations may be used as a more precise and fast method to obtain calibration data for real monolithic detectors. PMID: 31416055 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 15, 2019 Category: Physics Authors: Stockhoff M, Van Holen R, Vandenberghe S Tags: Phys Med Biol Source Type: research

An injectable dosimeter for small animal irradiations.
Abstract Accuracy and precision in dosimetry is crucial in studies involving animal models. Small animal dosimetry, in particular for protracted exposures to non uniform radiation fields is particularly challanging. We have developed a novel in-vivo dosimeter based on glass encapsulated TLD rods. These encapsulated rods can be injected into mice and used for validating doses to an individual mouse in a protracted irradiation scenario where the mouse is free to move in an inhomogenous radiation field. Data from 30 irradiated mice shows a reliable dose reconstruction within 10% of the nominal delivered dose. PM...
Source: Physics in Medicine and Biology - August 15, 2019 Category: Physics Authors: Garty G, Pujol-Canadell M, Brenner DJ Tags: Phys Med Biol Source Type: research

Reply to Comment on 'Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry'.
Abstract Shen (2019) commented on our paper 'Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry' regarding the impact of the low dose tail of the collimated x-ray beam we used to acquire individual response maps of large area ionization chambers. The behavior of this low dose tail was measured and compared to the simulations performed by Shen (2019). It was shown that the model of the tail by Shen (2019) is simplistic and overestimates its effect. PMID: 31416058 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 15, 2019 Category: Physics Authors: Kuess P, Boehlen T, Lechner W, Elia A, Georg D, Palmans H Tags: Phys Med Biol Source Type: research

Comment on 'Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry'.
Abstract This comment demonstrated that the low dose tails were not negligible for determining lateral response heterogeneity of Bragg peak ionization chambers. PMID: 31416061 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 15, 2019 Category: Physics Authors: Shen J Tags: Phys Med Biol Source Type: research

Automated 3-D ultrasound image analysis for first trimester assessment of fetal health.
We present a deep learning and image processing solution i) to perform semantic segmentation of the whole fetus, ii) to estimate plane orientation for standard biometry views, iii) to localize and automatically estimate biometry, and iv) to detect fetal limbs from a 3-D first trimester volume. Computational analysis methods were built using a real-world dataset (n=44 volumes). An evaluation on a further independent clinical dataset (n=21 volumes) showed that the automated methods approached human expert assessment of a 3D volume.&amp;#13. PMID: 31408850 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 13, 2019 Category: Physics Authors: Ryou H, Yaqub MK, Cavallaro A, Papageorghiou AT, Noble A Tags: Phys Med Biol Source Type: research

Bayesian pharmacokinetic modeling of dynamic contrast-enhanced magnetic resonance imaging: validation and application.
In conclusion, the Bayesian modeling approach provides an elegant means to determine uncertainty via posterior distributions within a single step and provides honest information about changes in parameter estimates. PMID: 31404913 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 12, 2019 Category: Physics Authors: Mittermeier A, Ertl-Wagner B, Ricke J, Dietrich O, Ingrisch M Tags: Phys Med Biol Source Type: research

Integration of high velocity test object motion into a channelized Hotelling observer for the assessment of x-ray angiography systems.
Abstract Assessment of x-ray angiography systems is typically performed using stationary task objects with simple geometries such as a disk on a uniform background. However, these methods do not represent realistic imaging conditions in interventional cardiology as anatomy and devices are inherently non-stationary due to cardiac motion. In this work, a novel method using the channelized Hotelling observer (CHO) was used to assess the influence of motion blur on object detectability. A standard CHO model assumes image system stationarity whereby the detectability index d' of a task object is independent of location...
Source: Physics in Medicine and Biology - August 8, 2019 Category: Physics Authors: Tao A, Fetterly KA Tags: Phys Med Biol Source Type: research

MR-based cardiac and respiratory motion correction of PET: application to static and dynamic cardiac < sup > 18 < /sup > F-FDG imaging.
This study shows that MR-based motion correction of cardiac PET results in improved image quality that can benefit both static and dynamic studies. PMID: 31394518 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 8, 2019 Category: Physics Authors: Petibon Y, Sun T, Han PK, Ma C, El Fakhri G, Ouyang J Tags: Phys Med Biol Source Type: research

Depth-of-interaction study of a dual-readout detector based on TOFPET2 application-specific integrated circuit.
Abstract Depth-of-interaction (DOI) capability is important for achieving high spatial resolution and sensitivity in dedicated organ and small animal positron emission tomography (PET) scanners. The dual-ended readout is one of the common methods that can achieve good DOI resolution. The aim of this study is to evaluate a dual-ended readout detector based on silicon photomultiplier (SiPM) and TOFPET2 application- specific integrated circuit (ASIC). The detector is based on 4×4 lutetium-yttrium oxyorthosilicate (LYSO) units, each unit contained 6×6 LYSO pixels, and the pixel size was 1×1×20 ...
Source: Physics in Medicine and Biology - August 5, 2019 Category: Physics Authors: Li M, Abbaszadeh S Tags: Phys Med Biol Source Type: research

A Monte Carlo based radiation response modelling framework to assess variability of clinical RBE in proton therapy.
In this study, a radiation response modelling framework for assessing clinical RBE variability is established. It was applied to four selected glioma patients (grade III) treated with adjuvant radio(chemo)therapy and who developed late morphological image changes on T1-weighted contrast-enhanced (T1w-CE) magnetic resonance (MR) images within approximately two years of recurrence-free follow-up. The image changes were correlated voxelwise with dose and linear energy transfer (LET) values using univariable and multivariable logistic reression analysis. The regression models were evaluated by the area-under-the-curve (AUC) pe...
Source: Physics in Medicine and Biology - August 2, 2019 Category: Physics Authors: Eulitz J, Lutz B, Wohlfahrt P, Dutz A, Enghardt W, Karpowitz C, Krause M, Troost EGC, Lühr A Tags: Phys Med Biol Source Type: research

Design and feasibility of a flexible, on-body, high impedance coil receive array for a 1.5 T MR-linac.
Conclusions:&amp;lt;/b&amp;gt; The use of HICs allowed for the design of our flexible, on-body receive array for MRIgRT. The design was shown to be dosimetrically feasible and improved the SNR. Future research with a full array will have to show the gain in parallel imaging performance and thus acceleration. PMID: 31370043 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 1, 2019 Category: Physics Authors: Zijlema SE, Tijssen RHN, Malkov VN, van Dijk L, Hackett SL, Kok JGM, Lagendijk JJW, Van den Berg CAT Tags: Phys Med Biol Source Type: research

Intra-fraction motion prediction in MRI-guided radiation therapy using Markov processes.
Abstract Internal organ motion during radiation delivery may lead to underdosing of cancer cells or overdosing of normal tissue, potentially causing treatment failure or normal-tissue toxicity. Organ motion is of particular concern in the treatment of lung and abdominal cancers, where breathing induces large tumor displacement and organ deformation. A new generation of radiotherapy devices is equipped with on-board MRI scanners to acquire a real-time movie of the patient's anatomy during radiation delivery. The goal of this research is to develop, calibrate, and test motion predictive models that employ real-time ...
Source: Physics in Medicine and Biology - August 1, 2019 Category: Physics Authors: Mirzapour SA, Mazur TR, Sharp GC, Salari E Tags: Phys Med Biol Source Type: research

Partial Prostate Cancer Treatment for Aggressive Disease-Common Practice.
PMID: 31327412 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 23, 2019 Category: Physics Authors: Moon DH, Chen RC Tags: Int J Radiat Oncol Biol Phys Source Type: research

Time-resolved volumetric MRI in MRI-guided radiotherapy: an in-silico comparative analysis.
Abstract MRI-treatment units enable 2D cine-MRI centred in the tumour for motion detection in radiotherapy, but they lack 3D information due to spatio-temporal limits. To derive time-resolved 3D information, different approaches have been proposed in the literature, but a rigorous comparison among these strategies has not yet been performed. The goal of this study is to quantitatively investigate five published strategies that derive time-resolved volumetric MRI in MRI-guided radiotherapy: Propagation, out-of-plane motion compensation, Fayad model, ROI-based model and Stemkens model. Comparisons were performed usi...
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Paganelli C, Portoso S, Garau N, Meschini G, Via R, Buizza G, Keall PJ, Riboldi M, Baroni G Tags: Phys Med Biol Source Type: research

Imaging of < sup > 99m < /sup > Tc-DMSA and < sup > 18 < /sup > F-FDG in humans using a Si/CdTe Compton camera.
Conclusions: To the best of our knowledge, for the first time, the current study demonstrates first time that the Si/CdTe Compton camera is capable of simultaneously imaging the distributions of two radiopharmaceuticals, 99mTc-DMSA and 18F-FDG, in a human body. These results suggest that the Si/CdTe Compton camera has the potential to become a novel modality for nuclear medical diagnoses enabling multi-probe simultaneous tracking.&amp;#13; &amp;#13. PMID: 31323647 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Nakano T, Sakai M, Torikai K, Suzuki Y, Noda SE, Yamaguchi M, Takeda S, Nagao Y, Kikuchi M, Odaka H, Kamiya T, Kawachi N, Watanabe S, Arakawa K, Takahashi T Tags: Phys Med Biol Source Type: research

2D ultrasound imaging based intra-fraction respiratory motion tracking for abdominal radiation therapy using machine learning.
Abstract We have previously developed a robotic ultrasound imaging system for motion monitoring in abdominal radiation therapy. Owing to the slow speed of ultrasound image processing, our previous system could only track abdominal motions under breath-hold. To overcome this limitation, a novel 2D-based image processing method for tracking intra-fraction respiratory motion is proposed. Fifty-seven different anatomical features acquired from 27 sets of 2D ultrasound sequences were used in this study. Three 2D ultrasound sequences were acquired with the robotic ultrasound system from three healthy volunteers. The rem...
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Huang P, Su L, Chen S, Cao K, Song Q, Kazanzides P, Iordachita I, Lediju Bell MA, Wong JW, Li D, Ding K Tags: Phys Med Biol Source Type: research

The dielectric properties of skin and their influence on the delivery of tumor treating fields to the torso: a study combining < i > in vivo < /i > measurements with numerical simulations.
This study provides a new insight into the role of skin in determining the distribution of TTFields within the body. PMID: 31323651 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Hershkovich HS, Urman N, Yesharim O, Naveh A, Bomzon Z Tags: Phys Med Biol Source Type: research

Impacts of photon counting CT to maximum intensity projection (MIP) images of cerebral CT angiography: theoretical and experimental studies.
Abstract While CTA is an established clinical gold standard for imaging large cerebral arteries and veins, an important challenge that currently remains for CTA is its limited performance in imaging small perforating arteries with diameters below 0.5 mm. The purpose of this work was to theoretically and experimentally study the potential benefits of using photon counting detector (PCD)-based CT (PCCT) to improve the performance of CTA in imaging these small arteries. In particular, the study focused on an important component of the CTA image package known as the maximum intensity projection (MIP) image. To help un...
Source: Physics in Medicine and Biology - July 17, 2019 Category: Physics Authors: Harvey E, Feng M, Ji X, Zhang R, Li Y, Chen GH, Li K Tags: Phys Med Biol Source Type: research

Dynamic beam current control for improved dose accuracy in PBS proton therapy.
Abstract The step-and-shoot method of pencil beam scanning delivers the dose on a three-dimensional grid in the target volume, with one dimension defined by the proton energy. While the dose per pencil beam may vary substantially within an iso-energy layer, the beam current typically remains constant. In this static operation mode, the inherent latency of the beam switch-off mechanism results in a lower limit for the deliverable spot dose, which may prevent the application of some of the low-weighted spots prescribed by the treatment planning system. To overcome this limitation, we introduced dynamic beam current ...
Source: Physics in Medicine and Biology - July 17, 2019 Category: Physics Authors: Bula C, Belosi MF, Eichin M, Hrbacek J, Meer D Tags: Phys Med Biol Source Type: research

Non-invasive determination of blood input function to compute rate of myocardial glucose uptake from dynamic FDG PET images of rat heart in vivo: comparative study between the inferior vena cava and the left ventricular blood pool with spill over and partial volume corrections.
Abstract The purpose of this work was to compute blood input function from the inferior vena cava (IVC) with partial volume (PV) corrections and compare to that obtained from the left ventricular blood pool (LVBP) with spill-over (SP) and partial volume (PV) corrections. These were then used to compute and validate rates of myocardial 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake (Ki) from dynamic positron emission tomography (PET) images of rat hearts in vivo in comparison to that obtained from invasive arterial blood sampling. Whole body 60 minute dynamic FDG PET/CT imaging of n=8 control Wistar Kyoto (WKY) rats ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Huang Q, Massey JC, Minczuk K, Li J, Kundu BK Tags: Phys Med Biol Source Type: research

Predicting lung nodule malignancies by combining deep convolutional neural network and handcrafted features.
Abstract To predict lung nodule malignancy with a high sensitivity and specificity, we propose a fusion algorithm that combines handcrafted features (HF) into the features learned at the output layer of a 3D deep convolutional neural network (CNN). First, we extracted twenty-nine handcrafted features, including nine intensity features, eight geometric features, and twelve texture features based on grey-level co-occurrence matrix (GLCM) averaged from five grey levels, four distances and thirteen directions. We then trained 3D CNNs modified from three 2D CNN architectures (AlexNet, VGG-16 Net and Multi-crop Net) to ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Li S, Xu P, Li B, Chen L, Zhou Z, Hao H, Duan Y, Folkert MR, Ma J, Huang S, Jiang SB, Wang J Tags: Phys Med Biol Source Type: research

EPR-imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities.
r M Abstract New hybrid radiotherapy treatment systems combining an MRI-scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging. &amp;#13; In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Höfel S, Fix MK, Zwicker F, Sterpin E, Drescher M Tags: Phys Med Biol Source Type: research

An investigation of quantitative accuracy for deep learning based denoising in oncological PET.
Abstract Reducing radiation dose is important for PET imaging. However, reducing injection doses causes increased image noise and low signal-to-noise ratio (SNR), subsequently affecting diagnostic and quantitative accuracies. Deep learning methods have shown a great potential to reduce the noise and improve the SNR in low dose PET data. &amp;#13; In this work, we comprehensively investigated the quantitative accuracy of small lung nodules, in addition to visual image quality, using deep learning based denoising methods for oncological PET imaging. We applied and optimized an advanced deep learning method based...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Lu W, Onofrey JA, Lu Y, Shi L, Ma T, Liu Y, Liu C Tags: Phys Med Biol Source Type: research