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Physics in Medicine and Biology

Shuai Leng, Wei Zhou, Zhicong Yu, Ahmed F Halaweish, Bernhard Krauss, Bernhard Schmidt, Lifeng Yu, Steffen Kappler, Cynthia H McCollough
Photon-counting computed tomography (PCCT) uses a photon counting detector to count individual photons and allocate them to specific energy bins by comparing photon energy to preset thresholds. This enables simultaneous multi-energy CT with a single source and detector. Phantom studies were performed to assess the spectral performance of a research PCCT scanner by assessing the accuracy of derived images sets. Specifically, we assessed the accuracy of iodine quantification in iodine map images and of CT number accuracy in virtual monoenergetic images (VMI)...
July 20, 2017: Physics in Medicine and Biology
Joe R Feldkamp, Stephen Quirk
Alternative coil designs for single coil MIT (magnetic induction tomography) are considered in this work, with the intention of improving upon the standard design used previously. In particular, we note that the blind spot associated with this coil type, a portion of space along its axis where eddy current generation can be very weak, has an important effect on performance. The seven designs tested here vary considerably in the size of their blind spot. To provide the most discerning test possible, we use laboratory phantoms containing feature dimensions similar to blind spot size...
July 18, 2017: Physics in Medicine and Biology
Shengtao Lin, Ge Zhang, Chee Hau Leow, Meng-Xing Tang
The sub-micron phase change contrast agent (PCCA) composed of a perfluorocarbon liquid core can be activated into gaseous state and form stable echogenic microbubbles for contrast-enhanced ultrasound imaging. It has shown great promises in imaging microvasculature, tumour microenvironment, and cancer cells. Although PCCAs have been extensively studied for different diagnostic and therapeutic applications, the effect of biologically geometrical confinement on the acoustic vaporisation of PCCAs is still not clear...
July 18, 2017: Physics in Medicine and Biology
Enrique Muñoz, John Barrio, Ane Etxebeste, Pablo Garcia Ortega, Carlos Lacasta, Josep Francisco Oliver, Carles Solaz, Gabriela Llosa
Compton imaging devices have been proposed and studied for a wide range of applications. We have developed a Compton camera prototype which can be operated with two or three detector layers based on monolithic lanthanum bromide (LaBr3) crystals coupled to silicon photomultipliers (SiPMs), to be used for proton range verification in hadron therapy. In this work, we present the results obtained with our prototype in laboratory tests with radioactive sources and in simulation studies...
July 18, 2017: Physics in Medicine and Biology
Andreas Franz Resch, Hermann Fuchs, Dietmar Georg
Oxygen (<sup>16</sup>O) ions are a potential alternative to carbon ions in ion beam therapy. Their enhanced linear energy transfer indicates a higher relative biological effectiveness and a reduced oxygen enhancement ratio. Due to the limited availability of <sup>16</sup>O ion beams, Monte Carlo (MC) transport codes are important research tools to investigate their potential. The purpose of this study was to validate GATE/Geant4 for <sup>16</sup>O ion beam therapy on experimental data from literature...
July 18, 2017: Physics in Medicine and Biology
Farhad Moradi, Ngie Min Ung, M U Khandaker, Ghafour Amouzad Mahdiraji, Marniza Saad, Rozita Abdul Malik, Anita Zarina Bustam, Zainor Zaili, David A Bradley
The relatively new treatment modality electronic intraoperative radiotherapy (IORT) is gaining popularity, irradiation being obtained within a surgically produced cavity being delivered via a low-energy X-ray source and spherical applicators, primarily for early stage breast cancer. Due to the spatially dramatic dose-rate fall off with radial distance from the source and effects related to changes in the beam quality of the low keV photon spectra, dosimetric account of the Intrabeam system is rather complex...
July 14, 2017: Physics in Medicine and Biology
Simon Bernard, Vadim Monteiller, Dimitri Komatitsch, Philippe L Lasaygues
We introduce an ultrasonic quantitative imaging method for long bones based on full-waveform inversion. The cost function is defined as the difference in the L2-norm sense between observed data and synthetic results at a given iteration of the iterative inversion process. For simplicity, and in order to reduce the computational cost, we use a two-dimensional acoustic approximation. The inverse problem is solved iteratively based on a quasi-Newton technique called the Limited-memory Broyden-Fletcher-Goldfarb-Shanno method...
July 7, 2017: Physics in Medicine and Biology
Nurul Ab Aziz Hashikin, Chai-Hong Yeong, Susanna Guatelli, Basri Johan Jeet Abdullah, Kwan-Hoong Ng, Alessandra Malaroda, Anatoly B Rozenfeld, Alan C Perkins
We aimed to investigate the validity of the partition model (PM) in estimating the absorbed doses to liver tumour (D<sub>T</sub>), normal liver tissue (D<sub>NL</sub>) and lungs (D<sub>L</sub>), when cross-fire irradiations between these compartments are being considered. Methods: MIRD-5 phantom incorporated with various treatment parameters, i.e. tumour involvement (TI), tumour-to-normal liver uptake ratio (T/N) and lung shunting (LS), were simulated using the Geant4 Monte Carlo (MC) toolkit...
July 7, 2017: Physics in Medicine and Biology
Marlies Pasler, Kilian Michel, Livia Marrazzo, Michael Obenland, Stefania Pallotta, Mari Bjoernsgard, Johannes Lutterbach
The purpose of this study was to characterize a new single large-area ionization chamber, the Integral Quality Monitor (IQM) system (iRT, Germany), for online and real-time beam monitoring. Signal stability, monitor unit (MU) linearity and dose rate dependence were investigated for static and arc deliveries and compared to independent ionization chamber measurements. The dose verification capability of the transmission detector system was evaluated by comparing calculated and measured detector signals for 15 volumetric modulated arc therapy (VMAT) plans...
July 5, 2017: Physics in Medicine and Biology
Hui Shan M Chan, Bas H M van der Velden, Claudette E Loo, Kenneth G A Gilhuijs
We present a radiomics model to discriminate between patients at low risk and those at high risk of treatment failure at long-term follow-up based on eigentumors: principal components computed from volumes encompassing tumors in washin and washout images of pre-treatment dynamic contrast-enhanced (DCE-) MR images. Eigentumors were computed from the images of 563 patients from the MARGINS study. Subsequently, a least absolute shrinkage selection operator (LASSO) selected candidates from the components that contained 90% of the variance of the data...
July 5, 2017: Physics in Medicine and Biology
Bin Li, Heui Chang Lee, Xinhui Duan, Chenyang Shen, Linghong Zhou, Xun Jia, Ming Yang
The dual-energy CT-based (DECT) approach holds promise in reducing the overall uncertainty in proton stopping-power-ratio (SPR) estimation as compared to the conventional stoichiometric calibration approach. The objective of this study was to analyze the factors contributing to uncertainty in SPR estimation using the DECT-based approach and to derive a comprehensive estimate of the range uncertainty associated with SPR estimation in treatment planning. Two state-of-the-art DECT-based methods, the Hünemohr-Saito method (2014, 2012) and the Bourque method (2014), were selected and implemented on a Siemens SOMATOM Force DECT scanner...
July 5, 2017: Physics in Medicine and Biology
Tianyuan Wang, Takeaki Ishihara, Atsushi Kono, Naoki Yoshida, Hiroaki Akasaka, Naritoshi Mukumoto, Ryuichi Yada, Yasuo Ejima, Kenji Yoshida, Daisuke Miyawaki, Kenichiro Kakutani, Kotaro Nishida, Noriyuki Negi, Toshiaki Minami, Yuuichi Aoyama, Satoru Takahashi, Ryohei Sasaki
The objective of the present study was the determination of the potential dosimetric benefits of using metal-artefact-suppressed dual-energy computed tomography (DECT) images for cases involving pedicle screw implants in spinal sites. A heterogeneous spinal phantom was designed for the investigation of the dosimetric effect of the pedicle-screw-related artefacts. The dosimetric comparisons were first performed using a conventional two-directional opposed (AP-PA) plan, and then a volumetric modulated arc therapy (VMAT) plan, which are both used for the treatment of spinal metastases in our institution...
July 4, 2017: Physics in Medicine and Biology
Wenzheng Sun, Mingyan Jiang, Lei Ren, Jun Dang, Tao You, Fang-Fang Yin
To improve the prediction accuracy of respiratory signals using adaptive boosting and multi-layer perceptron neural network (ADMLP-NN) for gated treatment of moving target in radiation therapy. The respiratory signals acquired using a Real-time Position Management (RPM) device from 138 previous 4DCT scans were retrospectively used in this study. The ADMLP-NN was composed of several artificial neural networks (ANNs) which were used as weaker predictors to compose a stronger predictor. The respiratory signal was initially smoothed using a Savitzky-Golay finite impulse response smoothing filter (S-G filter)...
June 30, 2017: Physics in Medicine and Biology
Maximillian Westphal, Sara N Lim, Sultana N Nahar, Enam Chowdhury, Anil Kumar Pradhan
With the advent of monochromatic and quasi-monochromatic x-ray sources, we explore their potential with computational and experimental studies on propagation through a combination of low and high-Z (atomic number) media for applications to imaging and detection. The multi-purpose code GEANT4 and a new code PHOTX are employed in numerical simulations, and a variety of x-ray sources are considered: conventional broadband devices with well-known spectra, quasi-monochromatic laser driven sources, and monochromatic synchrotron x-rays...
June 30, 2017: Physics in Medicine and Biology
Alejandro Rodriguez-Ruiz, Greeshma A Agasthya, Ioannis Sechopoulos
To characterize and develop a patient-based 3D model of the compressed breast undergoing mammography and breast tomosynthesis. Methods: During this IRB-approved, HIPAA-compliant study, 50 women were recruited to undergo 3D breast surface imaging with structured light (SL) during breast compression, along with simultaneous acquisition of a tomosynthesis image. A pair of SL systems were used to acquire 3D surface images by projecting 24 different patterns onto the compressed breast and capturing their reflection off the breast surface in approximately 12 - 16 seconds...
June 30, 2017: Physics in Medicine and Biology
Alec Hughes, Kullervo Hynynen
The use of a phased array of ultrasound transducer elements to sonicate through the skull has opened the way for new treatments and the delivery of therapeutics beyond the blood-brain barrier. The limited steering range of current clinical devices, particularly at higher frequencies, limits the regions of the brain that are considered treatable by ultrasound. A new array design is introduced that allows for high levels of beam steering and increased transmission throughout the brain. These improvements are achieved using concave transducers normal to the outer-skull surface in a patient-specific configuration to target within the skull, so that the far-field of each beam is within the brain...
June 30, 2017: Physics in Medicine and Biology
Issam El Naqa, Sarah L Kerns, James Coates, Yi Luo, Corey Speers, Catharine M L West, Barry S Rosenstein, Randall K Ten Haken
Advances in patient-specific information and biotechnology have contributed to a new era of computational medicine. Radiogenomics has emerged as a new field that investigates the role of genetics in treatment response to radiation therapy. Radiation oncology is currently attempting to embrace these recent advances and add to its rich history by maintaining its prominent role as a quantitative leader in oncologic response modeling. Here, we provide an overview of radiogenomics starting with genotyping, data aggregation, and application of different modeling approaches based on modifying traditional radiobiological methods or application of advanced machine learning techniques...
June 28, 2017: Physics in Medicine and Biology
Zhenyu Tang, Yihong Wu, Yong Fan
A novel groupwise image registration framework is developed for registering MR brain images with tumors. Our method iteratively estimates a normal-appearance counterpart for each tumor image to be registered and constructs a directed graph (digraph) of normal-appearance images to guide the groupwise image registration. Particularly, our method maps each tumor image to its normal appearance counterpart by identifying and inpainting brain tumor regions with intensity information estimated using a low-rank plus sparse matrix decomposition based image representation technique...
June 28, 2017: Physics in Medicine and Biology
Charles-Antoine Collins-Fekete, Sébastien Brousmiche, David C Hansen, Luc Beaulieu, Joao Seco
The relative stopping power (RSP) uncertainty is the largest contributor to the range uncertainty in proton therapy. The purpose of this work was to develop a systematic method that yields accurate and patient-specific RSPs by combining 1) pre-treatment X-ray CT and 2) daily proton radiography of the patient. The method was formulated as a penalized least squares optimization problem (<i>argmin</i>(|<b>A</b><b>x</b>-<b>b</b>|<sub>2</sub><sup>2</sup>))...
June 28, 2017: Physics in Medicine and Biology
Thomas Tessonnier, Till Tobias Boehlen, Francesco Cerutti, Alfredo Ferrari, Paola Roberta Sala, Stephan Brons, Thomas Haberer, Juergen Debus, Katia Parodi, Andrea Mairani
The introduction of "new" ion species in particle therapy needs to be supported by a thorough assessment of their dosimetric properties and by treatment planning comparisons with clinically used proton and carbon ion beams. In addition to the latter two ions, helium and oxygen ion beams are foreseen at the Heidelberg Ion beam Therapy (HIT) center as potential assets for improving clinical outcomes in the near future. We present in this study a dosimetric validation of a FLUKA-based Monte Carlo Treatment Planning tool (MCTP) for protons, helium, carbon and oxygen ions for spread-out Bragg peaks...
June 26, 2017: Physics in Medicine and Biology
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