Fast and accurate pseudo multispectral technique for whole-brain MRI tissue classification.
Abstract Numerous strategies have been proposed to classify brain tissues into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). However, many of them fail when classifying specific regions with low contrast between tissues. In this work, we propose an alternative pseudo multispectral classification (PMC) technique using CIE LAB spaces instead of gray scale T1-weighted MPRAGE images, combined with a new preprocessing technique for contrast enhancement and an optimized iterative K-means clustering. To improve the accuracy of the classification process, gray scale images were converted to multispect...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Fatnassi C, Zaidi H Tags: Phys Med Biol Source Type: research

Miniature fluorescence molecular tomography (FMT) endoscope based on a MEMS scanning mirror and an optical fiberscope.
We present a novel FMT endoscope by using a MEMS scanning mirror and an optical fiberscope. The diameter of this highly miniaturized FMT device is only 5mm. To our knowledge, this is the smallest FMT device we found so far. Several phantom experiments based on indocyanine green (ICG) were conducted to demonstrate the imaging ability of this device. Two tumor-bearing mice were systematically injected with tumor-targeted NIR fluorescent probes (ATF-PEG-IO-830) and were then imaged to further demonstrate the ability of this FMT endoscope for imaging small animals. PMID: 31117059 [PubMed - as supplied by publisher] (Sourc...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Yang H, Wang D, Shan T, Dai X, Xie H, Yang L, Jiang H Tags: Phys Med Biol Source Type: research

Scatter correction of cone-beam CT using a deep residual convolution neural network (DRCNN).
Abstract Scatter correction is an essential technique to improve the image quality of cone-beam CT (CBCT). Although different scatter correction methods have been proposed in the literature, a standard solution is still being studied due to the limitations including accuracy, computation efficiency and generalization. In this paper, we propose a novel scatter correction scheme for CBCT using a deep residual convolution neural network (DRCNN) to overcome the limitations. The proposed method combines the deep convolution neural network (CNN) and the residual learning framework (RLF) to train the mapping function fro...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Jiang Y, Yang C, Yang P, Hu X, Luo C, Xue Y, Xu L, Hu X, Zhang L, Wang J, Sheng K, Niu T Tags: Phys Med Biol Source Type: research

Radiosensitivity of colorectal cancer to < sup > 90 < /sup > Y and the radiobiological implications for radioembolisation therapy.
Conclusion: We derived radiosensitivity parameters for two CRC cell lines exposed to &amp;lt;sup&amp;gt;90&amp;lt;/sup&amp;gt;Y, 6 MV x-rays, and 137Cs γ-rays irradiation. These radiobiological parameters are critical to understanding the dose response of CRC lesions and ultimately informs the efficacy of &amp;lt;sup&amp;gt;90&amp;lt;/sup&amp;gt;Y SIRT relative to other radiation therapy modalities. PMID: 31117062 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Lee BQ, Abbott EM, Able S, Thompson J, Hill MA, Kartsonaki C, Vallis KA, Falzone N Tags: Phys Med Biol Source Type: research

The stability of imaging biomarkers in radiomics: a framework for evaluation.
Abstract This paper studies the sensitivity of a range of image texture parameters used in radiomics to: i) the number of intensity levels, ii) the method of quantisation to select the intensity levels and iii) the use of an intensity threshold. 43 commonly used texture features were studied for the gross target volume outlined on the CT component of PET/CT scans of 50 patients with non-small cell lung carcinoma (NSCLC). All cases were quantised for all values between 4 and 128 intensity levels using four commonly used quantisation methods. All results were analysed with and without a threshold range of -200 HU to...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Wang HYC, Donovan EM, Nisbet A, South CP, Alobaidli S, Ezhil V, Phillips I, Prakash V, Ferreira M, Webster P, Evans PM Tags: Phys Med Biol Source Type: research

Generating synthesized computed tomography (CT) from cone-beam computed tomography (CBCT) using CycleGAN for adaptive radiation therapy.
Abstract Throughout the course of delivering a radiation therapy treatment, which may take several weeks, a patient's anatomy may change drastically, and adaptive radiation therapy (ART) may be needed. Cone-beam computed tomography (CBCT), which is often available during the treatment process, can be used for both patient positioning and ART re-planning. However, due to the prominent amount of noise, artifacts, and inaccurate Hounsfield Unit (HU) values, the dose calculation based on CBCT images could be inaccurate for treatment planning. One way to solve this problem is to convert CBCT images to more accurate syn...
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Liang X, Chen L, Nguyen D, Zhou Z, Gu X, Yang M, Wang J, Jiang SB Tags: Phys Med Biol Source Type: research

MRI < i > B < /i > < sub > 0 < /sub > homogeneity and geometric distortion with continuous linac gantry rotation on an Elekta Unity MR-linac.
Conclusion: MR imaging on the Elekta Unity MR-Linac with the gantry in continuous motion is negligibly different from the static gantry case with current clinical pulse sequences. Real-time tracking and treatment plan adaptation using MR images obtained with the linac gantry in motion is possible. PMID: 31108467 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Jackson SJ, Glitzner M, Tijssen RHN, Raaymakers BW Tags: Phys Med Biol Source Type: research

Impact of intensity discretization on textural indices of [18F]FDG-PET tumour heterogeneity in lung cancer patients.
ényi E, Balkay L Abstract Quantifying tumour heterogeneity from [18F]FDG-PET images promises benefits for treatment selection of cancer patients. Here, the calculation of texture parameters mandates an initial discretization step (binning) to reduce the number of intensity levels. Typically, three types of discrimination methods are used: lesion relative resampling (LRR) with fixed bin number, lesion absolute resampling (LAR) and absolute resampling (AR) with fixed bin widths. We investigated the effects of varying bin widths or bin number using 27 commonly cited local and regional texture indices (TIs) app...
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Forgács A, Béresová M, Garai I, Lassen ML, Beyer T, DiFranco MD, Berényi E, Balkay L Tags: Phys Med Biol Source Type: research

Deployable cylindrical phased-array applicator mimicking a concentric-ring configuration for minimally-invasive delivery of therapeutic ultrasound.
Abstract A novel design for a deployable catheter-based ultrasound applicator for endoluminal and laparoscopic intervention is introduced. By combining a 1D cylindrical ring phased array with an expandable paraboloid or conical-shaped balloon-based reflector, the applicator can be controllably collapsed for compact delivery and deployed to mimic a forward-firing larger diameter concentric ring array with tight focusing and electronic steering capabilities in depth. Comprehensive acoustic and biothermal parametric studies were employed to characterize the capabilities of the applicator design as a function of trans...
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Adams M, Diederich C Tags: Phys Med Biol Source Type: research

A fast regularized iterative algorithm for fan-beam CT reconstruction.
Abstract We propose a fast iterative image reconstruction algorithm for normal, short-scan, and super-short-scan fan-beam computed tomography (CT), which aims at iterative reconstruction for low-dose and few-view CT by minimizing a data-fidelity term regularized with a total variation (TV) penalty. The derivation of the algorithm can be outlined as follows. First, the original minimization problem is formulated into a saddle-point (primal-dual) problem by using the Lagrangian duality, to which we apply the alternating projection proximal (APP) algorithm, which belongs to a class of first-order primal-dual methods....
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Wang T, Kudo H, Yamazaki F, Liu H Tags: Phys Med Biol Source Type: research

A Survey Study of Female Radiation Oncology Residents' Experiences to Inform Change.
CONCLUSIONS: In the first study to our knowledge to focus specifically on the experiences of women residents in radiation oncology, a number of areas for potential improvement were highlighted, including isolation and under-representation, mentorship needs, bias and harassment, and numerous other gender-based obstacles, including need for support during pregnancy and motherhood. These findings support the organization of groups such as the Society of Women in Radiation Oncology, which seeks to target these needs in order to promote gender equity. PMID: 31108141 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 17, 2019 Category: Physics Authors: Osborn VW, Doke K, Griffith KA, Jones R, Lee A, Maquilan G, Masters AH, Albert AA, Dover LL, Puckett LL, Hentz C, Kahn JM, Colbert LE, Barry PN, Jagsi R Tags: Int J Radiat Oncol Biol Phys Source Type: research

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.&amp;#13; &amp;#13; 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 (&amp;gt;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,&amp;#13; is an emerging imaging technique that holds great promise for biomedical imaging.&amp;#13; PACT is a hybrid imaging method that can exploit the strong endogeneous contrast of optical methods&amp;#13; along with the high spatial resolution of ultrasound methods.&amp;#13; In its canonical form that is addressed in this article, PACT seeks to estimate the photoacoustically-induced&amp;#13; intial pressure distribution within the object.&amp;#13; 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&amp;lt;sub&amp;gt;e&amp;lt;/sub&amp;gt;- Z&amp;lt;sub&amp;gt;med&amp;lt;/sub&amp;gt;, 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. &amp;#13; &amp;#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.&amp;#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&amp;#13; cancer is presented. Instead of generating a tomographic image of the breast, the&amp;#13; proposed technique aims to reconstruct a map of malignant tumours inside the&amp;#13; breast by adopting an extended form of factorization method. The implementation&amp;#13; of factorization method requires (i) two multi-static scattered field measurements&amp;#13; around the breast, which correspond to two different states of the breast, and (ii) the&amp;#13; 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&amp;#13; in Proton Therapy, and is encapsulated in a scalar quantity known as Relative&amp;#13; Biological Eective (RBE). It is currently recognized that a constant RBE of 1.1 is&amp;#13; not consistent with radiobiological experiment and will lead to sub-optimal clinical&amp;#13; outcome during treatment planning. To overcome this problem, several RBE models&amp;#13; have been developed, and in most of these models, there is a dependence of RBE on&amp;#13; 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