Charged particle radiobiology beamline using tandem accelerator-based MeV protons and carbon ions: a pilot study on the track-end radiation quality, variable biological effectiveness and Bayesian beam dosimetry.
Abstract For in vitro cell irradiation using tandem accelerator-based MeV protons and carbon ions, by TOPAS simulation, a polit study of performance evaluation is presented on a collimation beamline for 3 MeV protons and 10 MeV carbon ions from a 2×3 MV tandem accelerator. Based on the elements and source parameters, a collimated beam of 2.8 MeV protons or 2.5 MeV carbon ions, with 5.175 mm or 5.166 mm full width tenth maximum (FWTM)), respectively, can be delivered to target cell dish. TOPAS simulations and/or deterministic algorithms present a Bragg curve of linear energy transfer (LET) (10~70 keV/μm) a...
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Li X, Zhang W, Wang X, Chen X, Pan H, Ruan Y, Khaledi N, Wei T, He X, Zhuo W, Shao C, Pan Y, Shi LQ, Fu S, Wang X Tags: Phys Med Biol Source Type: research

Non-invasive myocardial performance mapping using 3D echocardiographic stress-strain loops.
In conclusion, stress-strain loops were, for the first time, estimated from 3D echocardiography and correlated to the clinical gold standard for local metabolism, showing the future potential of RT3DE for the assessment of local metabolic activity of the heart. PMID: 31096199 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Pedrosa J, Duchenne J, Queirós S, Degtiarova G, Gheysens O, Claus P, Voigt JU, D'hooge J Tags: Phys Med Biol Source Type: research

Integrating computer vision and non-linear optimization for automated deformable registration of three-dimensional medical images.
Abstract Deformable image registration (DIR), the process of estimating and applying non-linear transforms to spatially align sets of two or more images, is a challenging task with many important clinical applications including kinetic analysis, cancer treatment targeting, and evaluation of treatment response. Current techniques use non-linear optimizations only to reach a local minimum and not a globally optimal solution, limiting application to cases with small spatial displacements. Various semi-dense feature-based methods drawing inspiration from mammalian systems as the basis for 2D visual processing have bee...
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Huang K Tags: Phys Med Biol Source Type: research

Seated vs. supine: consideration of the optimum measurement posture for brain-dedicated PET.
In this report, we describe development of a markerless and contactless head motion tracking system and a study of healthy volunteers in several different postures to determine the optimum posture for brain PET. We used Kinect® (Microsoft) and developed software that can measure head motion with about 1-mm (translation) and less than 1-deg (rotation) accuracy. In the volunteer study, we measured the amount of head motion, with and without head fixation, in supine, normal sitting, and reclining postures. The results indicated that the normal sitting posture without head fixation had the largest head movement, and that t...
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Iwao Y, Tashima H, Yoshida E, Nishikido F, Ida T, Yamaya T Tags: Phys Med Biol Source Type: research

Incorporating dosimetric features into the prediction of 3D VMAT dose distributions using deep convolutional neural network.
In this study we propose a method to incorporate the dosimetric features in the construction of a more reliable dose prediction model based on the deep convolutional neural network (CNN). In addition to the contour information, the dose distribution from a PTV-only plan (i.e., the plan with the best PTV coverage by sacrificing the OARs sparing) is also employed as the model input to build a deep learning based dose prediction model. A database of 60 volumetric modulated arc therapy (VMAT) plans for the prostate cancer patients was used for training. The trained prediction model was then tested on a cohort of 10 cases. Dose...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Ma M, Kovalchuk N, Buyyounouski MK, Xing L, Yang Y Tags: Phys Med Biol Source Type: research

Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research.
Abstract Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limit...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Soultanidis G, Subiel A, Renard I, Reinhart AM, Green VL, Oelfke U, Archibald S, Greenman J, Tulk A, Walker A, Schettino G, Cawthorne C Tags: Phys Med Biol Source Type: research

Applying a variable relative biological effectiveness (RBE) might affect the analysis of clinical trials comparing photon and proton therapy for prostate cancer.
Abstract The purpose of this study was the evaluation of the impact of a variable relative biological effectiveness (RBE) compared to a constant RBE value of 1.1 in proton therapy prostate trials due to uncertainties in α/β ratio.
 
 Twenty patients receiving passive scattered proton therapy (PSPT) and fifteen patients receiving intensity modulated proton therapy (IMPT) were compared to twenty patients treated with 7-field intensity modulated photon therapy (IMRT). For proton beam therapy (PBT), the RBE was estimated using two different RBE models. Tumor control probabilities (TC...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Marteinsdottir M, Paganetti H Tags: Phys Med Biol Source Type: research

Multifunction bismuth gadolinium oxide nanoparticles as radiosensitizer in radiation therapy and imaging.
Abstract Multifunction bismuth-based nanoparticles with the ability of diagnostic and therapeutic functions have drawn extensive attention as theranostic agent in radiation therapy and imaging due to high atomic number, low toxicity, and low cost. Herein, we tried to introduce multifunction bismuth gadolinium oxide nanoparticles (BiGdO3) as a new theranostic agent for radiation therapy, computed tomography (CT) and magnetic resonance imaging (MRI). After synthesized of BiGdO3 nanoparticles and surface modifications of them with PEG, biocompatibility of the nanoparticle was evaluated by the CCK-8 assay. We investig...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Rajaee A, Zhao L, Wang S, Wang D, Liu Y, Wang J, Ying K Tags: Phys Med Biol Source Type: research

Minimum MU optimization (MMO): an inverse optimization approach for the PBS minimum MU constraint.
Abstract The deliverability of proton pencil beam scanning (PBS) treatment plans is subject to the minimum monitor unit (MU) constraint. This work introduces an inverse optimization approach to enforce the minimum MU constraint on planned spots, for accurate delivery of the planned dose. We formulate the minimum MU problem as an inverse optimization problem that accounts for the minimum MU constraint, i.e., minimum MU optimization (MMO). The MMO minimizes the difference between planned dose and deliverable dose while simultaneously enforcing the minimum MU constraint. Owing to the minimum MU constraint, MMO is non...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Gao H, Clasie BM, Liu T, Lin Y Tags: Phys Med Biol Source Type: research

Acoustic radiation force induced accumulation and dynamics of microbubbles on compliant surfaces.
Abstract Ultrasound stimulated microbubbles have been shown to be capable of breaking up blood clots through micro-scale interactions occurring near the clot surface. However, only a small fraction of bubbles circulating in the bloodstream will be in close proximity to such boundaries, where they must be to elicit therapeutic effects. Here, the accumulation and subsequent behavior of microbubbles displaced from an overlying flow channel to a boundary under radiation forces were examined. Experimental data were acquired using a novel high speed microscopy configuration and simulations were conducted to provide insi...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Acconcia CN, Leung BYC, Winch G, Wang J, Hynynen K, Goertz DE Tags: Phys Med Biol Source Type: research

Design and commissioning of an image-guided small animal radiation platform and quality assurance protocol for integrated proton and x-ray radiobiology research.
Conclusions: An image-guided small animal proton/x-ray research system was developed to enable in vivo investigations of radiobiological effects of proton beams, comparative studies between proton and x-ray beams, and investigations into novel proton treatment methods. PMID: 31075786 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 10, 2019 Category: Physics Authors: Kim M, Irmen P, Shoniyozov K, Verginadis II, Cengel KA, Koumenis C, Metz JM, Dong L, Diffenderfer E Tags: Phys Med Biol Source Type: research

Quantifying the dosimetric impact of organ-at-risk delineation variability in head and neck radiation therapy in the context of patient setup uncertainty.
Conclusion: The dosimetric impact of DV appeared to decrease when random and systematic SV was considered. Sensitivity to DV was affected by OAR objective type (i.e. Dmean vs. Dmax objectives) as well as distance from the target volume. PMID: 31071687 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Aliotta E, Nourzadeh H, Siebers JV Tags: Phys Med Biol Source Type: research

An age-dependent series of eye models for radiation dosimetry.
Abstract Several studies have been appeared, up to now, that indicate the effect of accurate simulation on dose received by different substructures of the eye, irradiated by external beams of short-range radiation such as electron. Different representations of the eye have consequently been introduced. Their accuracies depend on the purpose for which models are described or the degree of accuracy of information that models are based upon. All of developed models have presented the eye of an adult human, while the size, shape, and thickness of the eye substructures change with age. This work offers a series of age-...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Vejdani-Noghreiyan A, Ebrahimi-Khankook A Tags: Phys Med Biol Source Type: research

Quality assurance of gating response times for surface guided motion management treatment delivery using an electronic portal imaging detector.
This study shows a methodology which measured gating response times for AlignRT/Varian Truebeam combination which appears to be applicable to any surface guided monitoring/Linac combination as well as those combinations which incorporate extended lag times (>200ms). Beam on lag time appears to be measurably greater than beam off lag time. Although these gating response times are slower than other gating systems on the market, the advantages surface guided radiotherapy (SGRT) could potentially provide for treatment accuracy is discussed as well as demonstrating the lack of guidance regarding SGRT with respect to ...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Barfield G, Burton EW, Stoddart J, Metwaly M, Cawley MG Tags: Phys Med Biol Source Type: research

Development of a YAP(Ce) camera for the imaging of secondary electron bremsstrahlung X-ray emitted during carbon-ion irradiation toward the use of clinical conditions.
Abstract Low-energy X-ray imaging of the secondary electron bremsstrahlung X-ray emitted during carbon-ion irradiation is a promising method for range estimation. However, it remains unclear whether the method can be used for imaging with the clinical dose levels of carbon-ion and whether the bremsstrahlung X-ray can be detected from the deeper part of the body. To clarify these points, we developed a new high resolution low-energy X-ray camera and conducted imaging of the secondary electron bremsstrahlung X-ray during the irradiation of carbon-ions of different energies and intensities. Imaging was also tried wit...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Yamamoto S, Yamaguchi M, Akagi T, Sasano M, Kawachi N Tags: Phys Med Biol Source Type: research

Nanoparticle-mediated histotripsy (NMH) using perfluorohexane & quot;nanocones & quot.
In this study, we investigate the use of a newly developed NMH nanoparticle synthesized using an inclusion complex of methylated β-cyclodextrin and perfluorohexane (PFH). These "nanocones" (NCs) have advantages compared to previously used ND's due to their smaller size (~50nm), simple synthesis method, higher stability and information of definite PFH amount carried by the NC. To test the hypothesis that NCs can reduce the NMH cavitation threshold similar to ND's, and that the NMH cavitation threshold is dependent upon the total PFH concentration, tissue phantoms containing concentrations of NCs ranging from ...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Khirallah J, Schmieley R, Demirel E, Rehman TU, Howell J, Yuksel Durmaz Y, Vlaisavljevich E Tags: Phys Med Biol Source Type: research

A survey of computational frameworks for solving the acoustic inverse problem in three-dimensional photoacoustic computed tomography.
Abstract Photoacoustic computed tomography (PACT), also known as optoacoustic tomography,
 is an emerging imaging technique that holds great promise for biomedical imaging.
 PACT is a hybrid imaging method that can exploit the strong endogeneous contrast of optical methods
 along with the high spatial resolution of ultrasound methods.
 In its canonical form that is addressed in this article, PACT seeks to estimate the photoacoustically-induced
 intial pressure distribution within the object.
 Image reconstruction methods are employed to solve ...
Source: Physics in Medicine and Biology - May 8, 2019 Category: Physics Authors: Poudel J, Lou Y, Anastasio MA Tags: Phys Med Biol Source Type: research

Inversion of displacement fields to quantify the magnetic particle distribution in homogeneous elastic media from magnetomotive ultrasound.
Abstract Magnetomotive ultrasound (MMUS) contrasts superparamagnetic iron-oxide nanoparticles (SPIOs) that undergo submicrometer-scale displacements in response to a magnetic gradient force applied to an imaging sample. Typically, MMUS signals are defined in a way that is proportional to the SPIO displacements, rendering an indirect measure of the SPIO density distribution. Displacement-based MMUS, however, manifests "halo effects" that extend into regions without SPIOs due to their inherent mechanical coupling with the medium. To reduce such effects and to provide a more accurate representation of the S...
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Thapa D, Levy BE, Marks DL, Oldenburg AL Tags: Phys Med Biol Source Type: research

Structural and practical identifiability of dual-input kinetic modeling in dynamic PET of liver inflammation.
Abstract Dynamic F18-FDG PET with tracer kinetic modeling has the potential to noninvasively evaluate human liver inflammation using the FDG blood-to-tissue transport rate K1. Accurate kinetic modeling of dynamic liver PET data and K1 quantification requires the knowledge of dual-blood input function from the hepatic artery and portal vein. While the arterial input function can be derived from the aortic region on dynamic PET images, it is difficult to extract the portal vein input function accurately from PET images. The optimization-derived dual-input kinetic modeling approach has been proposed to overcome this ...
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Zuo Y, Sarkar S, Corwin MT, Olson KA, Badawi RD, Wang G Tags: Phys Med Biol Source Type: research

Small field correction factors determination for several active detectors using a Monte Carlo method in the Elekta Axesse linac equipped with circular cones.
Abstract A Monte Carlo (MC) method was used to determine small field output correction factors for several active detectors (Exradin A16, Exradin A26, PTW microLion, PTW microDiamond, Exradin W1 and IBA RAZOR) for an Elekta Axesse linac equipped with circular cones. MC model of the linac was built with the GamBet software, using the Penelope code system. The dose-to-water simulation for each cone, ranging from 5 to 30 mm of diameter size, was used to calculate field factors and the results were validated together with Gafchromic EBT3 film. Output factors (OFs) were measured with the active detectors and correction...
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Girardi A, Fiandra C, Giglioli FR, Gallio E, Hammad Ali O, Ragona R Tags: Phys Med Biol Source Type: research

Time-based signal sampling using sawtooth-shaped threshold.
In conclusion, the proposed method can be a cost-effective solution for data collection in future SiPM-based PET systems. PMID: 31051493 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Ko GB, Lee JS Tags: Phys Med Biol Source Type: research

Influence of intravenous contrast agent on dose calculation in proton therapy using dual energy CT.
Abstract The purpose of this study is to evaluate the effect of an intravenous (IV) contrast agent on proton therapy dose calculation using dual-energy computed tomography (DECT). Two DECT methods are considered. The first one, ρ<sub>e</sub>- Z<sub>med</sub>, attempts to accurately predict the proton stopping powers relative to water (SPR) of contrast enhanced (CE) DECT images, while the second generates a virtual non-contrast (VNC) volume that can be processed as a native non-contrast (NC) one. Both methods are compared ag...
Source: Physics in Medicine and Biology - May 2, 2019 Category: Physics Authors: Lalonde A, Xie Y, Burgdorf B, O'Reilly S, Ingram WS, Yin L, Zou W, Dong L, Bouchard H, Teo K Tags: Phys Med Biol Source Type: research

Photoacoustic imaging for guidance of interventions in cardiovascular medicine.
Abstract Imaging guidance is paramount to procedural success in minimally invasive interventions. Catheter-based therapies are the standard of care in the treatment of many cardiac disorders, including coronary artery disease, structural heart disease and electrophysiological conditions. Many of these diseases are caused by, or effect, a change in vasculature or cardiac tissue composition, which can potentially be detected by photoacoustic imaging. This review summarizes the state of the art in photoacoustic imaging approaches that have been proposed for intervention guidance in cardiovascular care. All of these t...
Source: Physics in Medicine and Biology - May 2, 2019 Category: Physics Authors: Iskander-Rizk S, van der Steen AFW, van Soest G Tags: Phys Med Biol Source Type: research

Acoustic radiation force imaging using a single-shot spiral readout.
Abstract The purpose of this study is to develop and validate rapid magnetic resonance acoustic radiation force imaging (MR-ARFI) using a single shot spiral readout for focused ultrasound (FUS) guidance and for local tissue displacement measurements. A magnetic resonance guided FUS system was used to focus a 3 MHz ultrasound beam to a predetermined position. MR-ARFI was performed with a Bruker 7T MRI using a modified single-shot spiral readout, with additional motion encoding gradients that convert local displacement into the phase image. Post processing was then used to analyze the resulting displacement and to e...
Source: Physics in Medicine and Biology - April 30, 2019 Category: Physics Authors: Ilovitsh A, Fite BZ, Ilovitsh T, Ferrara KW Tags: Phys Med Biol Source Type: research

Fast and exact Hessian computation for a class of nonlinear functions used in radiation therapy treatment planning.
We present the approach in the practical application of radiation therapy treatment planning, where this form appears for many common functions. In this case, the data matrices are the dose-influence matrices. The method is compared against automated differentiation. PMID: 31039550 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 30, 2019 Category: Physics Authors: van Haveren R, Breedveld S Tags: Phys Med Biol Source Type: research

Automated prioritised 3D dose-based MLC segment generation for step-and-shoot IMRT.
Abstract Segmentation can degrade a high-quality dose distribution obtained by fluence map optimisation (FMO). A novel algorithm is proposed for generation of MLC segments to deliver an FMO plan with step-and-shoot IMRT while minimising quality loss. All beams are considered simultaneously while generating MLC segments for reproducing the 3-dimensional FMO dose distribution. Segment generation is only steered by the 3D FMO dose distribution, i.e. underlying FMO fluence profiles are not considered. The algorithm features prioritised generation of segments, focusing on accurate reproduction of clinical objectives wi...
Source: Physics in Medicine and Biology - April 30, 2019 Category: Physics Authors: Schipaanboord BWK, Breedveld S, Rossi L, Keijzer M, Heijmen BJM Tags: Phys Med Biol Source Type: research

Characterization of a non-contact imaging scintillator-based dosimetry system for total skin electron therapy.
Conclusion: Scintillator dosimeters can potentially improve surface dosimetry-associated workflow for TSET in the radiation oncology clinic. Since scintillator data output can be automatically recorded to a patient medical record, the chances of human error in reading out and recording surface dose are minimized. 
 &#13. PMID: 31035267 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 29, 2019 Category: Physics Authors: Tendler II, Bruza P, Jermyn M, Cao X, Williams B, Jarvis LA, Pogue BW, Gladstone DJ Tags: Phys Med Biol Source Type: research

Dosimetric uncertainties as a result of temporal resolution in 4D dose calculations for PBS proton therapy.
Abstract This work investigates the dosimetric impact on 4D dose distribution estimation for pencil beam scanned (PBS) proton therapy as function of the temporal resolution used for the time resolved dose calculation. For three liver patients (CTV volume: 403/122/264cc), 10-phase 4DCT-MRI datasets with ~15mm tumour motion were simulated for seven different motion periods (2-8s). 4D dose distributions were calculated and compared by considering both coarser and finer temporal resolutions (200-800ms and 20ms). Single scanned 4D plans for seven fraction doses (0.7/2/4/6/8/10/12Gy) were investigated, whose dose delive...
Source: Physics in Medicine and Biology - April 29, 2019 Category: Physics Authors: Zhang Y, Huth I, Weber DC, Lomax AJ Tags: Phys Med Biol Source Type: research

Impact of free-breathing CT on quantitative measurements of static and quiescent period-gated PET Images.
Abstract Measurements of standardized uptake values (SUV) can vary due to many causes, including respiratory motion. Various methodologies have been introduced to correct for motion in PET, with quiescent-period-gated (QPG) PET being the most popular approach. QPG has been shown to improve PET image quantification compared to static-whole-body (SWB) PET. However, to achieve this improvement, QPG PET requires CT attenuation correction data that matches the QPG PET data. In this paper we investigated the effect of using free-breathing CT for attenuation correction of QPG PET on SUVmax and SUVpeak and compared the re...
Source: Physics in Medicine and Biology - April 26, 2019 Category: Physics Authors: Meier JG, Einstein SA, Diab RH, Erasmus LJ, Xu G, Mawlawi OR Tags: Phys Med Biol Source Type: research

Development of a deep neural network for generating synthetic dual-energy chest X-ray images with single X-ray exposure.
In conclusion, the proposed method can obtain high-quality bone- and soft tissue-only CR images without the need for additional hardware for double X-ray exposures in clinical practice.&#13. PMID: 31026841 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2019 Category: Physics Authors: Lee D, Kim H, Choi B, Kim HJ Tags: Phys Med Biol Source Type: research

Modeling the primary source intensity distribution: reconstruction and inter-comparison of six Varian TrueBeam sources.
Abstract The primary source size is one of the most important beam model parameters in small photon fields. In this work we apply a recently suggested reconstruction technique to characterize the primary source of 6 Varian TrueBeam (TB) linacs. A series of photon fluence profile measurements were performed on 6 Varian TB linacs in the crossplane and inplane orientation using radiochromic film in air and a 2 mm Pb foil as a build-up layer. An image reconstruction algorithm was then applied, based on the maximum likelihood expectation-maximization (MLEM) algorithm, to estimate the source distribution. The method ite...
Source: Physics in Medicine and Biology - April 26, 2019 Category: Physics Authors: Papaconstadopoulos P, Levesque IR, Aldelaijan SI, O'Grady K, Devic S, Seuntjens J Tags: Phys Med Biol Source Type: research

Qualitative microwave imaging of breast cancer with contrast agents.
M, Gose E Abstract A microwave imaging (MWI) methodology for early diagnosis of breast
 cancer is presented. Instead of generating a tomographic image of the breast, the
 proposed technique aims to reconstruct a map of malignant tumours inside the
 breast by adopting an extended form of factorization method. The implementation
 of factorization method requires (i) two multi-static scattered field measurements
 around the breast, which correspond to two different states of the breast, and (ii) the
 inhomogeneous Green's function associated to...
Source: Physics in Medicine and Biology - April 26, 2019 Category: Physics Authors: Akinci MN, Çayören M, Gose E Tags: Phys Med Biol Source Type: research

Optical imaging for the characterization of radioactive carbon and oxygen ion beams.
In conclusion, optical imaging using luminescence and Cerenkov light could be used for the precise range estimation of radioactive ion beams. PMID: 31026851 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2019 Category: Physics Authors: Kang HG, Yamamoto S, Takyu S, Nishikido F, Mohammadi A, Horita R, Sato S, Yamaya T Tags: Phys Med Biol Source Type: research

Optimizing the response, precision, and cost of a DNA double-strand break dosimeter.
Abstract We developed a dosimeter that measures biological damage following delivery of therapeutic beams in the form of double-strand breaks to DNA. The dosimeter contains DNA strands that are labeled on one end with biotin and on the other with fluorescein and attached to magnetic microbeads. Following irradiation, a magnet is used to separate broken from unbroken DNA strands. Then, fluorescence is utilized to measure the relative amount of broken DNA and determine the probability for double-strand break. The long-term goal for this research is to evaluate whether this type of biologically based dosimeter holds ...
Source: Physics in Medicine and Biology - April 26, 2019 Category: Physics Authors: Obeidat M, McConnell K, Bui B, Stathakis S, Rasmussen K, Papanikolaou N, Shim EY, Kirby N Tags: Phys Med Biol Source Type: research

Dependence of LET on material and its impact on current RBE model.
Abstract Biological uncertainty remains one of the main sources of uncertainties
 in Proton Therapy, and is encapsulated in a scalar quantity known as Relative
 Biological Eective (RBE). It is currently recognized that a constant RBE of 1.1 is
 not consistent with radiobiological experiment and will lead to sub-optimal clinical
 outcome during treatment planning. To overcome this problem, several RBE models
 have been developed, and in most of these models, there is a dependence of RBE on
 dose-averaged Linear Energy Transfer (LET), LETd. In t...
Source: Physics in Medicine and Biology - April 25, 2019 Category: Physics Authors: Tan HQ, Koh WYC, Tan LKR, Phua JH, Ang KW, Park SY, Lew WS, Lee JCL Tags: Phys Med Biol Source Type: research

Bio-compatible patient-specific elastic bolus for clinical implementation.
Abstract We investigated two types of materials with very low Shore hardness, silicon rubber (Dragon Skin) and urethane liquid rubber (Clear Flex 30), for use in 3D printing patient-specific boluses. Boluses were 3D printed with these materials using two methods of casting and direct printing. These patient-specific boluses were designed for 3D-printed elaborate human phantoms and their biological, physical, and dosimetric properties were comprehensively assessed. The results of cytotoxicity, skin irritation, and skin sensitization tests showed that Dragon Skin was the most biologically stable material. Furthermor...
Source: Physics in Medicine and Biology - April 25, 2019 Category: Physics Authors: Park JM, Son J, An HJ, Kim JH, Wu HG, Kim JI Tags: Phys Med Biol Source Type: research

Performance comparison of depth-encoding detectors based on dual-ended readout and different SiPMs for high-resolution PET applications.
Abstract Silicon photomultipliers (SiPMs) are widely used in positron emission tomography (PET), however, SiPMs from different vendors vary in their performance characteristics. In addition, the specifications provided by the manufacturers are measured under different operating conditions and using different test setups, making it difficult to choose the optimal device for a specific application using the published specifications. In this work, we evaluated four state-of-the-art 8 × 8 arrays of ~ 3 mm × 3 mm SiPMs from SensL, KETEK, and Hamamatsu for high-resolution dual-ended readout detectors using t...
Source: Physics in Medicine and Biology - April 24, 2019 Category: Physics Authors: Du J, Bai X, Cherry SR Tags: Phys Med Biol Source Type: research

Biomechanically driven intraoperative spine registration during navigated anterior vertebral body tethering.
Abstract The integration of pre-operative biomechanical planning with intra-operative imaging for navigated corrective spine surgery may improve surgical outcome, as well as the accuracy and safety of manoeuvres such as pedicle screw insertion and cable tethering, as these steps are performed empirically by the surgeon. However, registration of finite element models (FEM) of the spine remains challenging due to changes in patient positioning and imaging modalities. The purpose of this study was to develop and validate a new method registering a preoperatively constructed patient-specific finite element model (FEM)...
Source: Physics in Medicine and Biology - April 24, 2019 Category: Physics Authors: Jobidon-Lavergne H, Kadoury S, Knez D, Aubin CE Tags: Phys Med Biol Source Type: research

Dosimetric impact of esophagus motion in single fraction spine stereotactic body radiotherapy.
Abstract Nine patients with single fraction spinal stereotactic body radiation therapy (SBRT) treatment were identified to assess both the intra fraction and daily esophageal motion and associated dosimetric deviation in spinal SBRT. We performed a chained deformable registration of 4-D CT phase images to estimate the intra fraction motion magnitude of the esophagus in a breathing cycle. The intra fraction esophageal motion mostly exhibited in the superior-inferior direction with the total motion magnitude increased from the T1 (0.7 mm) to the T11 vertebra level (6.5 mm). The actual dose received by a moving esoph...
Source: Physics in Medicine and Biology - April 24, 2019 Category: Physics Authors: Wang X, Yang J, Zhao Z, Luo D, Court LE, Zhang Y, Weksberg D, Brown PD, Li J, Ghia AJ Tags: Phys Med Biol Source Type: research

First clinical retrospective investigation of limited projection CBCT for lung tumor localization in patients receiving SBRT treatment.
Conclusion: The pilot clinical study shows that LP-CBCT localization offers comparable accuracy to CBCT localization for daily tumor positioning while reducing the projection number to 1/10 for patients receiving breath hold lung radiation treatment. The cluster projection sampling in this study also shows the feasibility of reconstructing fast 4D-CBCT from 1 min 3D-CBCT scan. PMID: 31018195 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 24, 2019 Category: Physics Authors: Zhang Y, Yin FF, Ren L Tags: Phys Med Biol Source Type: research

Dual-source photon counting detector CT with a tin filter: a phantom study on iodine quantification performance.
Conclusion: DS-PCD-CT with a Sn filter improved iodine quantification as compared to both SS-PCD-CT and DS-EID-CT. PMID: 31018197 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 24, 2019 Category: Physics Authors: Tao A, Huang R, Tao S, Michalak GJ, McCollough CH, Leng S Tags: Phys Med Biol Source Type: research

Compton PET: a layered structure PET detector with high performance.
Abstract In most high-resolution PET detector designs, there is an inherent trade-off between spatial resolution and detector efficiency. We have developed and tested a new geometry for the detector module which avoids this trade-off. The module uses a layered structure, in which four crystal slabs are stacked in the depth direction and optically separated by enhanced specular reflector (ESR) film. The scintillation light within each layer is measured by 16 SiPMs located on the four sides of the crystal. Analog signals from all SiPMs (4x16) on the four sides of the crystal are digitized individually using a 64-cha...
Source: Physics in Medicine and Biology - April 23, 2019 Category: Physics Authors: Peng P, Judenhofer MS, Cherry SR Tags: Phys Med Biol Source Type: research

A scalable database of organ doses for common diagnostic fluoroscopy examinations of children: procedures of current practice at the University of Florida.
In this study, we created procedural outlines which document all radiation exposure information required for organ dose assessment, akin to a reference RDSR, for six common diagnostic fluoroscopy procedures performed at the University of Florida (UF) Shands Pediatric Hospital. These procedures include the voiding cystourethrogram, the gastrostomy-tube placement, the lower gastrointestinal study, the rehabilitation swallow, the upper gastrointestinal study, and the upper gastrointestinal study with follow through. These procedural outlines were used to develop an extensive database of organ doses for the 162-member UF/NCI (...
Source: Physics in Medicine and Biology - April 23, 2019 Category: Physics Authors: Marshall EL, Rajderkar D, Brown JL, Stepusin EJ, Borrego D, Bolch WE Tags: Phys Med Biol Source Type: research

Physics-based spectral compensation algorithm for X-ray CT with primary modulator.
Abstract X-ray computed tomography (CT) scatter correction using primary modulator has been continuously developed over the past years, with progress in improving the performance of scatter correction. In this work, we further advance the primary modulator technique towards practical applications where the spectral nonuniformity caused by the modulator continues to be a challenging problem. A physics-based spectral compensation algorithm is proposed to adaptively correct for the spectral nonuniformity, and hence to reduce the resultant ring artifacts on reconstructed CT images. First, an initial spectrum of the CT...
Source: Physics in Medicine and Biology - April 18, 2019 Category: Physics Authors: Gao H, Zhang L, Grimmer R, Fahrig R Tags: Phys Med Biol Source Type: research

ADMM-based deep reconstruction for limited-angle CT.
Abstract In the real applications of computed tomography (CT) imaging, the projection data of the scanned objects are usually acquired within a limited-angle range because of the limitation of the scanning condition. Under these circumstances, conventional analytical algorithms, such as filtered back-projection (FBP), do not work because the projection data are incomplete. The regularization method has proven to be effective for tomographic reconstruction from under-sampled measurements. To deal with the limited-angle CT reconstruction problem, the regularization method is commonly used, but it is difficult to fin...
Source: Physics in Medicine and Biology - April 18, 2019 Category: Physics Authors: Wang J, Zeng L, Wang C, Guo Y Tags: Phys Med Biol Source Type: research

The potential of photon-counting CT for quantitative contrast-enhanced imaging in radiotherapy.
This study suggests that in a realistic simulation environment, the overall accuracy of radiotherapy-related parameters can be increased when using PCCT with 4 energy bins instead of DECT. This confirms the potential of PCCT to provide robust and quantitative tissue parameters for contrast-enhanced CT required in radiotherapy applications. PMID: 30999288 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 18, 2019 Category: Physics Authors: Simard M, Lapointe A, Lalonde A, Bahig H, Bouchard H Tags: Phys Med Biol Source Type: research

Localization of liver lesions in abdominal CT imaging: I. Correlation of human observer performance between anatomical and uniform backgrounds.
Conclusion: For the task of localizing low contrast liver lesions, human observer performance was highly correlated between anatomical and uniform backgrounds, suggesting that lesion localization studies emulating a clinical test of liver lesion detection can be performed using a uniform background. PMID: 30995611 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Dilger S, Yu L, Chen B, Favazza CP, Carter RE, Fletcher JG, McCollough CH, Leng S Tags: Phys Med Biol Source Type: research

ADAM phantom to test 4D medical imaging and dose delivery devices.
Abstract Radiotherapy treatment of moving lesions is a challenging task in which different strategies can be used. The clinical implementation of the variety of complex technical solutions pursued to treat cancer, while sparing healthy tissues, requires accurate quality assurance tests and adequate phantoms. The aim of this work is to report on the Anthropomorphic Dynamic breAthing Model (ADAM) and on its applications to test image quality and dose delivery for four-dimensional (4D) techniques used to compensate for breathing-induced tumor motion. ADAM reproduces a male torso containing realistic ribs an...
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Pallotta S, Calusi S, Masi L, Talamonti C, Marrazzo L, Foggi L, Casati M, Livi L, Simontacchi G, Desideri I, Lisci R Tags: Phys Med Biol Source Type: research

Ultrasound multiple scattering with microbubbles can differentiate between tumor and healthy tissue < i > in vivo < /i > .
Ultrasound multiple scattering with microbubbles can differentiate between tumor and healthy tissue in vivo. Phys Med Biol. 2019 Apr 17;: Authors: Mohanty K, Papadopoulou V, Newsome IG, Shelton S, Dayton PA, Muller M Abstract Most solid tumors are characterized by highly dense, isotropic vessel networks. Characterization of such features has shown promise for early cancer diagnosis. Ultrasound diffusion has been used to characterize the micro-architecture of complex media, such as bone and the lungs. In this work, we examine a non-invasive diffusion-based ultrasound technique to assess neo-vasculariza...
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Mohanty K, Papadopoulou V, Newsome IG, Shelton S, Dayton PA, Muller M Tags: Phys Med Biol Source Type: research

Efficient detrending of uniform images for accurate determination of the noise power spectrum at low frequencies.
Abstract The noise power spectrum (NPS) of a digital x-ray imaging device is usually estimated from the average of periodograms of ROIs in images obtained with uniform radiation fields. In order to mitigate low frequency trends, present in the images and not arising from stochastic processes, detrending methods are applied to the images before being Fourier transformed. The most common of these methods subtracts a second-order polynomial fit from the image. In this work, it is shown that the characteristics of low frequency trends can deviate from the quadratic dependence on spatial coordinates. This re...
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Gonzalez-Lopez A, Campos-Morcillo PA Tags: Phys Med Biol Source Type: research