Impact of motion compensation and partial volume correction for < sup > 18 < /sup > F-NaF PET/CT imaging of coronary plaque.
In conclusion, we have built and validated a STIR framework incorporating MoCo and PVC for &lt;sup&gt;18&lt;/sup&gt;F-NaF PET imaging of coronary plaques. First results indicate an improved quantification of plaque-type lesions. PMID: 29095701 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - November 2, 2017 Category: Physics Authors: Cal-Gonzalez J, Tsoumpas CH, Lassen ML, Rasul S, Koller L, Hacker M, Schäfers KP, Beyer T Tags: Phys Med Biol Source Type: research

The incidence of the different sources of noise on the uncertainty in radiochromic film dosimetry using single channel and multichannel methods.
A, Ruiz-Morales C Abstract The influence of the various sources of noise on the uncertainty in radiochromic film (RCF) dosimetry using single channel and multichannel methods is investigated in this work. These sources of noise are extracted from pixel value (PV) readings and dose maps. Pieces of an RCF were each irradiated to different uniform doses, ranging from 0 to 1092 cGy. Then, the pieces were read at two resolutions (72 and 150 ppp) with two flatbed scanners: Epson 10000XL and Epson V800, representing two states of technology. Noise was extracted as described in ISO 15739 (2013), separating its distinct co...
Source: Physics in Medicine and Biology - November 1, 2017 Category: Physics Authors: González-López A, Vera-Sánchez JA, Ruiz-Morales C Tags: Phys Med Biol Source Type: research

Towards an in-plane methodology to track breast lesions using mammograms and patient-specific finite-element simulations.
J, Del Palomar AP Abstract In breast cancer screening or diagnosis, it is usual to combine different images in order to locate a lesion as accurately as possible. These images are generated using a single or several imaging techniques. As x-ray-based mammography is widely used, a breast lesion is located in the same plane of the image (mammogram), but tracking it across mammograms corresponding to different views is a challenging task for medical physicians. Accordingly, simulation tools and methodologies that use patient-specific numerical models can facilitate the task of fusing information from different images...
Source: Physics in Medicine and Biology - November 1, 2017 Category: Physics Authors: Lapuebla-Ferri A, Cegoñino-Banzo J, Jiménez-Mocholí AJ, Del Palomar AP Tags: Phys Med Biol Source Type: research

Accelerating volumetric cine MRI (VC-MRI) using undersampling for real-time 3D target localization/tracking in radiation therapy: a feasibility study.
Conclusions: It is feasible to estimate VC-MRI from a single undersampled on-board 2D cine MRI. Phantom and patient studies showed that the temporal resolution of VC-MRI can potentially be improved by 5-10 times using a 2D cine image acquired with 10-20% k-space sampling. . PMID: 29087963 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 31, 2017 Category: Physics Authors: Harris W, Yin FF, Wang C, Zhang Y, Cai J, Ren L Tags: Phys Med Biol Source Type: research

Dosimetric Feasibility of Using Tungsten-Based Functional Paper for Flexible Chest Wall Protectors in Intraoperative Electron Radiotherapy for Breast Cancer.
In this study, the applicability of newly developed tungsten-based functional paper (TFP) was assessed as an alternative to the existing protective disk. The radiation-shielding performance of the TFP was verified through experimental measurements and Monte Carlo simulations. Percentage depth dose curves and lateral dose profiles with and without TFPs were measured and simulated on a dedicated IOERT accelerator. The number of piled-up TFPs was changed from 1 to 40. In the experimental measurements, the relative doses at the exit plane of the TFPs for 9 MeV were 42.7%, 9.2%, 0.2%, and 0.1% with 10, 20, 30, and 40 TFPs, resp...
Source: Physics in Medicine and Biology - October 30, 2017 Category: Physics Authors: Kamomae T, Monzen H, Kawamura M, Okudaira K, Nakaya T, Mukouyama T, Miyake Y, Ishihara Y, Itoh Y, Naganawa S Tags: Phys Med Biol Source Type: research

Electromechanical wave imaging and electromechanical wave velocity estimation in a large animal model of myocardial infarction.
Conclusions: These results indicate that EWI and EW velocity might help with the detection of infarcts and their border zones, which may be useful for characterizing arrhythmogenic substrate. . PMID: 29083316 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 30, 2017 Category: Physics Authors: Costet A, Melki L, Sayseng V, Hamid N, Nakanishi K, Wan E, Hahn R, Homma S, Konofagou EE Tags: Phys Med Biol Source Type: research

Investigating the generalisation of an atlas-based synthetic-CT algorithm to another centre and MR scanner for prostate MR-only radiotherapy.
This study suggests that the atlas-based algorithm can be generalised to MR data acquired using a different field strength at a different centre. PMID: 29076457 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Wyatt J, Dowling JA, Kelly CG, McKenna J, Johnstone E, Speight R, Henry A, Greer PB, McCallum HM Tags: Phys Med Biol Source Type: research

Feasibility of MR-only proton dose calculations for prostate cancer radiotherapy using a commercial pseudo-CT generation method.
Abstract A magnetic resonance (MR)-only radiotherapy workflow can reduce cost, radiation exposure and uncertainties introduced by CT-MRI registration. A crucial prerequisite is generating the so called pseudo-CT (pCT) images for accurate dose calculation and planning. Many pCT generation methods have been proposed in the scope of photon radiotherapy. This work aims at verifying for the first time whether a commercially available photon-oriented pCT generation method can be employed for accurate intensity-modulated proton therapy (IMPT) dose calculation. A retrospective study was conducted on ten prostate canc...
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Maspero M, Van den Berg CAT, Landry G, Belka C, Parodi K, Seevinck PR, Raaymakers BW, Kurz C Tags: Phys Med Biol Source Type: research

Determination of mean ionization potential using magnetic resonance imaging for the reduction of proton beam range uncertainties: theory and application.
We present a novel model to accurately calculate mean ionization potential from measurements acquirable by MRI and show its feasibility in a phantom. PMID: 29077570 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Sudhyadhom A Tags: Phys Med Biol Source Type: research

Shading correction assisted iterative cone-beam CT reconstruction.
Abstract Recent advances in total variation (TV) technology enable accurate CT image reconstruction from highly under-sampled and noisy projection data. The standard iterative reconstruction algorithms, which work well in conventional CT imaging, fail to perform as expected in cone beam CT (CBCT) applications, wherein the non-ideal physics issues, including scatter and beam hardening, are more severe. These physics issues result in large areas of shading artifacts and cause deterioration to the piecewise constant property assumed in reconstructed images. To overcome this obstacle, we incorporate a shading correcti...
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Yang C, Wu P, Gong S, Wang J, Lyu Q, Tang X, Niu T Tags: Phys Med Biol Source Type: research

Monte Carlo simulation of radiation transport and dose deposition from locally released gold nanoparticles labeled with (111)In, (177)Lu or (90)Y incorporated into tissue implantable depots.
We report here the 3D dose distribution resulting from a NPD incorporating AuNP labeled with electron emitters ((90)Y, (177)Lu, (111)In) of different energies using Monte Carlo based voxel level dosimetry. The MCNP5 Monte Carlo radiation transport code was used to assess differences in dose distribution from simulated NPD and conventional brachytherapy sources, positioned in breast tissue simulating material. We further compare these dose distributions in mice bearing subcutaneous human breast cancer xenografts implanted with (177)Lu-AuNP NPD, or injected IT with (177)Lu-AuNP in suspension. The radioactivity distributions ...
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Lai P, Cai Z, Pignol JP, Lechtman E, Mashouf S, Lu Y, Winnik MA, Jaffray DA, Reilly RM Tags: Phys Med Biol Source Type: research

K-edge energy-based calibration method for photon counting detectors.
Abstract In recent years, potential applications of energy-resolved photon counting detectors (PCDs) in the x-ray medical imaging field have been actively investigated. Unlike conventional x-ray energy integration detectors, PCDs count the number of incident x-ray photons within certain energy windows. For PCDs, the interactions between x-ray photons and photoconductor generate electronic voltage pulse signals. The pulse height of each signal is proportional to the energy of the incident photons. By comparing the pulse height with the preset energy threshold values, x-ray photons with specific energies are recorde...
Source: Physics in Medicine and Biology - October 26, 2017 Category: Physics Authors: Ge Y, Ji X, Zhang R, Li K, Chen GH Tags: Phys Med Biol Source Type: research

Evaluation of water-mimicking solid phantom materials for use in HDR and LDR brachytherapy dosimetry.
This study includes the HDR therapy sources Nucletron Flexisource Co-60 HDR (&lt;sup&gt;60&lt;/sup&gt;Co), Eckert und Ziegler BEBIG GmbH CSM-11 (&lt;sup&gt;137&lt;/sup&gt;Cs), Implant Sciences Corporation HDR Yb-169 Source 4140 (&lt;sup&gt;169&lt;/sup&gt;Yb) as well as the LDR therapy sources IsoRay Inc. Proxcelan CS-1 (&lt;sup&gt;131&lt;/sup&gt;Cs), IsoAid Advantage I-125 IAI-125A (&lt;sup&gt;125&lt;/sup&gt;I), and IsoAid Advantage Pd-103 IAPd-103A (&lt;sup&gt;103&lt;/sup&gt;Pd). Thereby our previous comparison between phantom ...
Source: Physics in Medicine and Biology - October 26, 2017 Category: Physics Authors: Schoenfeld AA, Thieben M, Harder D, Poppe B, Chofor N Tags: Phys Med Biol Source Type: research

Stability analysis of a deterministic dose calculation for MRI-guided radiotherapy.
Abstract Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field...
Source: Physics in Medicine and Biology - October 24, 2017 Category: Physics Authors: Zelyak O, Fallone BG, St Aubin J Tags: Phys Med Biol Source Type: research

Lifetime attributable risk as an alternative to effective dose to describe the risk of cancer for patients in diagnostic and therapeutic nuclear medicine.
Abstract Abstract The aim of this study is to implement lifetime attributable risk (LAR) predictions of cancer for patients of various age and gender, undergoing diagnostic investigations or treatments in nuclear medicine and to compare the outcome with a population risk estimate using effective dose and the International Commission on Radiological Protection risk coefficients. The radiation induced risk of cancer occurrence (incidence) or death from four nuclear medicine procedures are estimated for both male and female between 0 and 120 years. Estimations of cancer risk are performed using recommended admin...
Source: Physics in Medicine and Biology - October 24, 2017 Category: Physics Authors: Andersson M, Eckerman K, Mattsson LJS Tags: Phys Med Biol Source Type: research

Technical characterization of five X-ray detectors for paediatric radiography applications.
Abstract Physical image quality of five x-ray detectors used in the paediatric imaging department is characterized with the aim of establishing the range/scope of imaging performance provided by these detectors for neonatal imaging. Two computed radiography (CR) detectors (MD4.0 powder imaging plate (PIP) and HD5.0 needle imaging plate (NIP), Agfa HealthCare NV, B-2640 Mortsel, Belgium) and three flat panel detectors (FPD) (the Agfa DX-D35C and DX-D45C and the DRX-2530C (Carestream Health Inc., Rochester - NY 14608, USA)) were assessed. Physical image quality was characterized using the detector metrics given by t...
Source: Physics in Medicine and Biology - October 24, 2017 Category: Physics Authors: Marshall NW, Smet MH, Hofmans M, Pauwels H, De Clerq T, Bosmans H Tags: Phys Med Biol Source Type: research

Dosimetry and prescription in liver radioembolization with 90Y microspheres: 3D calculation of tumor-to-liver ratio from global 99mTc-MAA SPECT information.
This study presents a methodology to calculate the T/N ratio using global information from the SPECT. The T/N ratio is estimated by establishing uptake thresholds consistent with previously performed volumetry. This dose calculation method was validated against three-dimensional voxel dosimetry, and was also compared with the standard partition method based on freehand regions of interest (ROI) outlining on SPECT slices. Both comparisons were done on a sample of 20 actual cases of hepatocellular carcinoma treated with resin microspheres. The proposed method and the voxel dosimetry give very similar results. Differences are...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Mañeru F, Abós D, Bragado L, Fuentemilla N, Caudepón F, Pellejero S, Miquelez S, Rubio A, Goñi E, Hernández-Vitoria A Tags: Phys Med Biol Source Type: research

Validation of proton stopping power ratio estimation based on dual energy CT using fresh tissue samples.
This study confirms the advantages of DECT-based SPR estimation although good results were also obtained using SECT for most tissues. PMID: 29057753 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Taasti VT, Michalak GJ, Hansen DC, Deisher A, Kruse JJ, Krauss B, Muren LP, Petersen JBB, McCollough CH Tags: Phys Med Biol Source Type: research

Small composite field correction factors for the CyberKnife radiosurgery system: clinical and PCSR plans.
Abstract A formalism has been proposed for small and non-standard photon fields in which k&lt;sup&gt;fclin, fmsr&lt;/sup&gt; &lt;sub&gt;Qclin, Qmsr&lt;/sub&gt; correction factors are used to correct dosimeter response in small fields (static or composite) relative to that in a larger machine-specific reference (MSR) field. For composite fields, a plan-class specific reference (PCSR) field can also be defined, serving as an intermediate calibration field between the MSR and clinical fields within a certain plan-class. In this work, the formalism was applied in the calculation of k&am...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Christiansen EJ, Muir BR, Belec J, Vandervoort EJ Tags: Phys Med Biol Source Type: research

Study for online range monitoring with the Interaction Vertex Imaging method.
Abstract Ion beam therapy enables a highly accurate dose conformation delivery to the tumor due to the finite range of charged ions in matter (i.e., Bragg Peak (BP)). Consequently, the dose profile is very sensitive to patients anatomical changes as well as minor mispositioning, and so it requires improved dose control techniques. Proton Interaction Vertex Imaging (IVI) could offer an online range control in carbon ion therapy. In this paper, a statistical method was used to study the sensitivity of the IVI technique on experimental data obtained from the Heidelberg Ion-Beam Therapy Center. The vertices of se...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Finck C, Karakaya Y, Reithinger V, Rescigno R, Baudot J, Constanzo J, Juliani D, Krimmer J, Rinaldi I, Rousseau M, Testa E, Vanstalle M, Ray C Tags: Phys Med Biol Source Type: research

Planning, guidance, and quality assurance of pelvic screw placement using deformable image registration.
Abstract Percutaneous pelvic screw placement is challenging due to narrow bone corridors surrounded by vulnerable structures and difficult visual interpretation of complex anatomical shapes in 2D x-ray projection images. To address these challenges, a system for planning, guidance, and quality assurance (QA) is presented, providing functionality analogous to surgical navigation, but based on robust 3D-2D image registration techniques using fluoroscopy images already acquired in routine workflow. Two novel aspects of the system are investigated: automatic planning of pelvic screw trajectories and the ability to acc...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Goerres J, Uneri A, Jacobson MW, Ramsay B, De Silva T, Ketcha MD, Han R, Manbachi A, Vogt S, Kleinszig G, Wolinsky JP, Osgood GM, Siewerdsen JH Tags: Phys Med Biol Source Type: research

Extension of the Fermi-Eyges most likely path in heterogeneous medium with prior knowledge information.
In conclusion, the introduction of prior-knowledge in the MLP formalism decreases the RMS uncertainty to the MC path, but no further than the use of a simpler Hull contour algorithm. The use of this Hull algorithm is suggested for future particle imaging applications. PMID: 29059051 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Collins-Fekete CA, Bär E, Volz L, Bouchard H, Beaulieu L, Seco J Tags: Phys Med Biol Source Type: research

Correspondence model-based 4D VMAT dose simulation for analysis of local metastasis recurrence after extracranial SBRT.
Abstract The purpose of this study is to introduce a novel approach to incorporate patient-specific breathing variability information into 4D dose simulation of volumetric arc therapy (VMAT)-based stereotactic body radiotherapy (SBRT) of extracranial metastases. Feasibility of the approach is illustrated by application to treatment planning and motion data of lung and liver metastasis patients. The novel 4D dose simulation approach makes use of a regression-based correspondence model that allows representing patient motion variability by breathing signal-steered interpolation and extrapolation of defor...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Sothmann T, Gauer T, Wilms M, Werner R Tags: Phys Med Biol Source Type: research

Determination of absorbed dose to water from a miniature kilovoltage X-ray source using a parallel-plate ionization chamber.
This article presents a formalism for calculating and independently verifying the absorbed dose to water from a kV x-ray source (The INTRABEAM System) measured in a water phantom with an ionization chamber calibrated in terms of air-kerma. This formalism uses a Monte Carlo (MC) calculated chamber conversion factor, &lt;i&gt;C&lt;sub&gt;Q&lt;/sub&gt;&lt;/i&gt;, to convert from air-kerma in a reference beam to absorbed dose to water in the measurement beam. In this work &lt;i&gt;C&lt;sub&gt;Q&lt;/sub&gt;&lt;/i&gt; was determined for a PTW 34013 parallel-plate io...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Watson PGF, Popovic M, Seuntjens J Tags: Phys Med Biol Source Type: research

Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry.
This study highlights the need for chamber-dependent response maps when using LAICs for absolute and relative dosimetry with proton pencil beams or small photon beams. PMID: 29059057 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Kuess P, Böhlen TT, Lechner W, Elia A, Georg D, Palmans H Tags: Phys Med Biol Source Type: research

Ultrasound functional imaging in an < i > ex vivo < /i > beating porcine heart platform.
In this study, an isolated beating pig heart setup was adapted and used for performance assessment of UFI techniques such as volume assessment and ultrasound strain imaging. The potential of performing verification and reproducibility studies was demonstrated. For proof-of-principle, validation of UFI in pathological hearts was examined. Ex vivo porcine hearts (n = 6, slaughterhouse waste) were resuscitated and attached to a mock circulatory system. Radio frequencyt ultrasound data of the left ventricle were acquired in five short axis views and one long axis view. Based on these slices, the cardiac outputCO was measu...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Petterson NJ, Fixsen LS, Rutten MCM, Pijls NHJ, van de Vosse FN, Lopata RGP Tags: Phys Med Biol Source Type: research

Theoretically exact backprojection filtration algorithm for multi-segment linear trajectory.
Abstract A theoretically exact backprojection filtration algorithm is proved and implemented for image reconstruction from a multi-segment linear trajectory assuming fan-beam geometry. The reconstruction formula is based on a concept of linear PI-line (L-PI) proposed in our previous work. The proof is completed in two consecutive steps. In the first step, it is proved that theoretically exact image reconstruction can be obtained on an arbitrary L-PI line from an infinite straight line trajectory. In the second step, it is shown that accurate image reconstruction can be achieved from a multi-segment line trajectory...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Wu W, Yu H, Cong W, Liu F Tags: Phys Med Biol Source Type: research

Biological and dosimetric characterisation of spatially fractionated proton minibeams.
Abstract The biological effectiveness of proton beams varies with depth, spot size and lateral distance from the beam central axis. The aim of this work is to incorporate proton relative biological effectiveness (RBE) and equivalent uniform dose (EUD) considerations into comparisons of broad beam and highly modulated proton minibeams. A Monte Carlo model of a small animal proton beamline is presented. Dose and variable RBE is calculated on a per-voxel basis for a range of energies (30-109 MeV). For an open beam, the RBE values at the beam entrance ranged from 1.02-1.04, at the Bragg peak (BP) from 1.3 to 1.6, and ...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Meyer J, Stewart RD, Smith D, Eagle J, Lee E, Cao N, Ford E, Hashemian R, Schuemann J, Saini J, Marsh S, Emery R, Dorman E, Schwartz JL, Sandison GA Tags: Phys Med Biol Source Type: research

Issues in quantification of registered respiratory gated PET/CT in the lung.
Abstract PET/CT quantification of lung tissue is limited by several difficulties: the lung density and local volume changes during respiration, the anatomical mismatch between PET and CT and the relative contributions of tissue, air and blood to the PET signal (the tissue fraction effect). Air Fraction Correction (AFC) has been shown to improve PET image quantification in the lungs. Methods to correct for the movement and anatomical mismatch involve respiratory gating and image registration techniques. While conventional registration methods only account for spatial mismatch, the Jacobian determinant of the deform...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Cuplov V, Holman BF, McClelland JR, Modat M, Hutton BF, Thielemans K Tags: Phys Med Biol Source Type: research

Spectral imaging using clinical megavoltage beams and a novel multi-layer imager.
Abstract We assess the feasibility of clinical megavoltage (MV) spectral imaging for material and bone separation with a novel multi-layer imager (MLI) prototype. The MLI provides higher detective quantum efficiency and lower noise than conventional electronic portal imagers. Simulated experiments were performed using a validated Monte Carlo model of the MLI to estimate energy absorption and energy separation between the MLI components. Material separation was evaluated experimentally using solid water and aluminum (Al), copper (Cu) and gold (Au) for 2.5 MV, 6 MV and 6 MV flattening filter free (FFF) clinical phot...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Myronakis ME, Fueglistaller R, Rottmann J, Hu YH, Wang A, Baturin P, Huber P, Morf D, Star-Lack JM, Berbeco RI Tags: Phys Med Biol Source Type: research

Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot.
Abstract Post-thrombotic syndrome, a frequent complication of deep venous thrombosis can be reduced with early vein recanalization. Pulsed cavitational therapy (PCT) using ultrasound is a recent non-invasive approach. We propose to test the efficacy and safety of high-frequency focused PCT for a drug-free thrombolysis (thrombotripsy) in a realistic in vitro model of venous thrombosis. To reproduce venous thrombosis conditions, human whole blood was allowed to clot by stasis in silicone tubes (6 mm internal diameter) at a 30 cmH20 pressure, maintained during the whole experiment. We engineered an ultrasound de...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Goudot G, Mirault T, Arnal B, Boisson-Vidal C, Le Bonniec B, Gaussem P, Galloula A, Tanter M, Messas E, Pernot M Tags: Phys Med Biol Source Type: research

A method for acquiring random range uncertainty probability distributions in proton therapy.
Abstract In treatment planning we depend upon accurate knowledge of geometric and range uncertainties. If the uncertainty model is inaccurate then the plan will produce under-dosing of the target and/or overdosing of OAR. We aim to provide a method for which centre and site-specific population range uncertainty due to inter-fraction motion can be quantified to improve the uncertainty model in proton treatment planning. Daily volumetric MVCT data from previously treated radiotherapy patients has been used to investigate inter-fraction changes to water equivalent path-length (WEPL). Daily image-guidance s...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Holloway SM, Holloway MD, Thomas SJ Tags: Phys Med Biol Source Type: research

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout.
t H Abstract A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the laser induced optical barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mech...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Bläckberg L, El Fakhri G, Sabet H Tags: Phys Med Biol Source Type: research

Analysis of dose heterogeneity using a subvolume-DVH.
Abstract The dose-volume histogram (DVH) is universally used in radiation therapy for its highly efficient way of summarizing three-dimensional dose distributions. An apparent limitation that is inherent to standard histograms is the loss of spatial information, e.g. it is no longer possible to tell where low- and high-dose regions are, and whether they are connected or disjoint. Two methods for overcoming the spatial fragmentation of low- and high-dose regions are presented, both based on the gray-level size zone matrix, which is a two-dimensional histogram describing the frequencies of connected regions of simil...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Said M, Nilsson P, Ceberg C Tags: Phys Med Biol Source Type: research

A Monte-Carlo study to assess the effect of 1.5 T magnetic fields on the overall robustness of pencil-beam scanning proton radiotherapy plans for prostate cancer.
Abstract Combining magnetic-resonance imaging (MRI) and proton therapy (PT) using pencil-beam scanning (PBS) may improve image-guided radiotherapy. We aimed at assessing the impact of a magnetic field on PBS-PT plan quality and robustness. Specifically, the robustness against anatomical changes and positioning errors in an MRI-guided scenario with a 30 cm radius 1.5 T magnetic field was studied for prostate PT. Five prostate cancer patients with three consecutive CT images (CT1-3) were considered. Single-field uniform dose PBS-PT plans were generated on the segmented CT1 with Monte-Carlo-based treatment pla...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Kurz C, Landry G, Resch AF, Dedes G, Kamp F, Ganswindt U, Belka C, Raaymakers BW, Parodi K Tags: Phys Med Biol Source Type: research

A reusable OSL-film for 2D radiotherapy dosimetry.
Abstract Optical stimulated luminescence (OSL) combines reusability, sub-mm resolution, and a linear dose response in a single radiation detection technology. Such a combination is currently lacking in radiotherapy dosimetry. But OSL-films have a strong energy dependent response to keV photons due to a relative high effective atomic number (Z eff). The current work studied the applicability of a 2D OSL-film with a reduced Z eff as (IMRT/VMAT) dosimeter. Based on their commercial OSL-film experience, Agfa Healthcare N.V. produced a new experimental OSL-film for RT dosimetry. This film had a lower effective atomic n...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Wouter C, Dirk V, Paul L, Tom D Tags: Phys Med Biol Source Type: research

Measurement and modeling of out-of-field doses from various advanced post-mastectomy radiotherapy techniques.
Abstract More and more advanced radiotherapy techniques have been adopted for post-mastectomy radiotherapies (PMRT). Patient dose reconstruction is challenging for these advanced techniques because they increase the low out-of-field dose area while the accuracy of out-of-field dose calculations by current commercial treatment planning systems (TPSs) is poor. We aim to measure and model the out-of-field radiation doses from various advanced PMRT techniques. PMRT treatment plans for an anthropomorphic phantom were generated, including volumetric modulated arc therapy (VMAT) with standard and flattening-filter-free (...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Yoon J, Heins D, Zhao X, Sanders M, Zhang R Tags: Phys Med Biol Source Type: research

Calibration and analysis of a multimodal micro-CT and structured light imaging system for the evaluation of excised breast tissue.
Abstract A multimodal micro-computed tomography (CT) and multi-spectral structured light imaging (SLI) system is introduced and systematically analyzed to test its feasibility to aid in margin delineation during breast conserving surgery (BCS). Phantom analysis of the micro-CT yielded a signal-to-noise ratio (SNR) of 34, a contrast of 1.64, and a minimum detectable resolution of 240 m for a 1.2 min scan. The SLI system, spanning wavelengths 490 nm to 800 nm and spatial frequencies up to 1.37 mm-1, was evaluated with aqueous tissue simulating phantoms having variations in particle size distribution, scatter density...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: McClatchy Iii DM, Rizzo EJ, Meganck J, Kempner J, Vicory J, Wells WA, Paulsen KD, Pogue BW Tags: Phys Med Biol Source Type: research

Atlas ranking and selection for automatic segmentation of the esophagus from CT scans.
Abstract In radiation treatment planning, the esophagus is an important organ-at-risk that should be spared in patients with head and neck cancer or thoracic cancer who undergo intensity-modulated radiation therapy. However, automatic segmentation of the esophagus from CT scans is extremely challenging because of the structure's inconsistent intensity, low contrast against the surrounding tissues, complex and variable shape and location, and random air bubbles. The goal of this study is to develop an online atlas selection approach to choose a subset of optimal atlases for multi-atlas segmentation to delineate eso...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Yang J, Haas B, Fang R, Beadle BB, Garden AS, Liao Z, Zhang L, Balter PA, Court LE Tags: Phys Med Biol Source Type: research

Complex-based OCT angiography algorithm recovers microvascular information superior to amplitude or phase-based algorithm in phase-stable systems.
Abstract Optical coherence tomography angiography (OCTA) is increasingly becoming a popular inspection tool for biomedical imaging applications. By exploring amplitude, phase and complex information available in the OCT signals, numerous algorithms are proposed to contrast functional vessel networks with microcirculation tissue beds. However, it is not clear which algorithm delivers optimal imaging performance. Here, we investigate systematically how the amplitude and phase information would have an impact on the OCTA imaging performance, upon which to establish the relationship of amplitude and phase stability wi...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Xu J, Song S, Li Y, Wang RK Tags: Phys Med Biol Source Type: research

A microvascular compartment model validated using < sup > 11 < /sup > C-methylglucose liver PET in pigs.
A microvascular compartment model validated using 11C-methylglucose liver PET in pigs. Phys Med Biol. 2017 Oct 18;: Authors: Munk OL, Keiding S, Baker C, Bass L Abstract The standard compartment model (CM) is widely used to analyze dynamic PET data. The CM is fitted to time-activity curves to estimate rate constants that describe the transport of tracer between well-mixed compartments. The aim of this study was to develop and validate a more realistic microvascular compartment model (MCM) that includes capillary tracer concentration gradients, backflux from cells into the perfused capillaries, and mul...
Source: Physics in Medicine and Biology - October 18, 2017 Category: Physics Authors: Munk OL, Keiding S, Baker C, Bass L Tags: Phys Med Biol Source Type: research

Monoplane 3D-2D registration of cerebral angiograms based on multi-objective stratified optimization.
The objective for matching was gradient magnitude correlation coefficient, which is invariant to in-plane translation. The in-plane translations are then found by locating the maximum of gradient phase correlation between the best matching pair of rotation and depth templates. On twenty pairs of 3D and 2D images of ten patients undergoing cerebral endovascular image-guided intervention the 3D to monoplane 2D registration experiments were setup with rather high range of initial mean target registration error from 0 to 100 mm. The proposed method effectively reduced the registration error to below 2 mm, which was further ref...
Source: Physics in Medicine and Biology - October 18, 2017 Category: Physics Authors: Aksoy T, Spiclin Z, Pernus F, Unal G Tags: Phys Med Biol Source Type: research

Contour propagation for lung tumor delineation in 4D-CT using tensor-product surface of uniform and non-uniform closed cubic B-splines.
Abstract A robust contour propagation method is proposed to help physicians delineate lung tumors on all phase images of four-dimensional computer tomography (4D-CT) by only manually delineating the contours on a reference phase. The proposed method models the trajectory surface swept by a contour in a respiratory cycle as a tensor-product surface of two closed cubic B-spline curves: a non-uniform B-spline curve which models the contour and a uniform B-spline curve which models the trajectory of a point on the contour. The surface is treated as a deformable entity, and is optimized from an initial surface by movin...
Source: Physics in Medicine and Biology - October 18, 2017 Category: Physics Authors: Jin R, Liu Y, Chen M, Zhang S, Song E Tags: Phys Med Biol Source Type: research

Multi-task transfer learning deep convolutional neural network: application to computer-aided diagnosis of breast cancer on mammograms.
This study demonstrates that multi-task transfer learning may be an effective approach for training DCNN in medical imaging applications when training samples from a single modality are limited. PMID: 29035873 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 16, 2017 Category: Physics Authors: Samala RK, Chan HP, Hadjiiski LM, Helvie MA, Cha K, Richter C Tags: Phys Med Biol Source Type: research

Parameter selection in limited data cone-beam CT reconstruction using edge-preserving total variation algorithms.
Abstract There are a number of powerful total variation (TV) regularization methods with great promises in limited data cone-beam CT reconstruction with an enhancement of image quality. These promising TV methods require careful selection of image reconstruction parameters for which there is no well established criteria. This pa- per presents a comprehensive valuation of parameter selection in a number of major TV-based reconstruction algorithms. The appropriate way of selecting the values for each individual parameter has been suggested. Finally, the new adaptive-weighted projec...
Source: Physics in Medicine and Biology - October 16, 2017 Category: Physics Authors: Lohvithee M, Biguri A, Soleimani M Tags: Phys Med Biol Source Type: research

A 20-channel magnetoencephalography system based on optically pumped magnetometers.
We describe a multichannel magnetoencephalography (MEG) system that uses optically pumped magnetometers (OPMs) to sense the magnetic fields of the human brain. The system consists of an array of 20 OPM channels conforming to the human subject's head, a person-sized magnetic shield containing the array and the human subject, a laser system to drive the OPM array, and various control and data acquisitions systems. We conducted two MEG experiments: auditory evoked magnetic field (AEF) and somatosensory evoked magnetic field (SEF), on three healthy male subjects, using both our OPM array and a 306-channel Elekta-Neuromag super...
Source: Physics in Medicine and Biology - October 16, 2017 Category: Physics Authors: Borna A, Carter TR, Goldberg JD, Colombo AP, Jau YY, Berry C, McKay J, Stephen J, Weisend M, Schwindt PDD Tags: Phys Med Biol Source Type: research

End-to-end workflow for finite element analysis of tumor treating fields in glioblastomas.
Abstract Tumor Treating Fields (TTFields) therapy is an approved modality of treatment for glioblastoma. Patient anatomy-based finite element analysis (FEA) has the potential to reveal not only how these fields affect tumor control but also how to improve efficacy. While the automated tools for segmentation speed up the generation of FEA models, multi-step manual corrections are required, including removal of disconnected voxels, incorporation of unsegmented structures and the addition of 36 electrodes plus gel layers matching the TTFields transducers. Existing approaches are also not scalable for the high through...
Source: Physics in Medicine and Biology - October 12, 2017 Category: Physics Authors: Timmons JJ, Lok E, San P, Bui K, Wong ET Tags: Phys Med Biol Source Type: research

The dosimetric impact of including the patient table in CT dose estimates.
Abstract The purpose of this study was to evaluate the dosimetric impact of including the patient table in Monte Carlo CT dose estimates for both spiral scans and scan projection radiographs (SPR). CT scan acquisitions were simulated for a Siemens SOMATOM Force scanner (Siemens Healthineers, Forchheim, Germany) with and without a patient table present. An adult male, an adult female and a pediatric female voxelized phantom were simulated. The simulated scans included tube voltages of 80 and 120 kVp. Spiral scans simulated without a patient table resulted in effective doses that were overestimated by approximately ...
Source: Physics in Medicine and Biology - October 10, 2017 Category: Physics Authors: Nowik P, Bujila R, Kull L, Andersson J, Poludniowski G Tags: Phys Med Biol Source Type: research

System geometry optimization for molecular breast tomosynthesis with focusing multi-pinhole collimators.
Abstract Imaging of Tc-99m labelled tracers is gaining popularity for detecting breast tumours. Recently, we proposed a novel design for molecular breast tomosynthesis (MBT) based on two sliding focusing multi-pinhole collimators that scan a modestly compressed breast. Simulation studies indicate that MBT has the potential to improve the tumour-to-background contrast-to-noise ratio significantly over state-of-the-art planar molecular breast imaging. The aim of the present paper is to optimize the collimator-detector geometry of MBT. Using analytical models, we first optimized sensitivity at different fixed system ...
Source: Physics in Medicine and Biology - October 10, 2017 Category: Physics Authors: van Roosmalen J, Beekman FJ, Goorden MC Tags: Phys Med Biol Source Type: research

Compton camera study for high efficiency SPECT and benchmark with Anger system.
In this study we compare a commercial SPECT-Anger device, the General Electrics Healthcare Innia system with a High Energy General Purpose (HEGP) collimator, and the Compton camera prototype under development by the French collaboration CLaRyS, through Monte Carlo simulations (GATE - GEANT4 Application for Tomographic Emission - version 7.1 and GEANT4 version 9.6, respectively). Given the possible introduction of new radio-emitters at higher energies intrinsically allowed by the Compton camera detection principle, the two detectors are exposed to point- like sources at increasing primary ...
Source: Physics in Medicine and Biology - October 10, 2017 Category: Physics Authors: Fontana M, Dauvergne D, Letang JM, Ley JL, Testa E Tags: Phys Med Biol Source Type: research