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Reference dosimetry of modulated and dynamic photon beams Phys. Med. Biol. (IF 2.883) Pub Date : 2021-01-13 Hugo Bouchard
In the late 1980s, a new technique was proposed that would revolutionize radiotherapy. Now referred to as intensity-modulated radiotherapy, it is at the core of state-of-the-art photon beam delivery techniques, such as helical tomotherapy and volumetric modulated arc therapy. Despite over two decades of clinical application, there are still no established guidelines on the calibration of dynamic modulated
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DaNet: dose-aware network embedded with dose-level estimation for low-dose CT imaging Phys. Med. Biol. (IF 2.883) Pub Date : 2021-01-13 Zhenxing Huang, Zixiang Chen, Jincai Chen, Ping Lu, Guotao Quan, Yanfeng Du, Chenwei Li, Zheng Gu, Yongfeng Yang, Xin Liu, Hairong Zheng, Dong Liang and Zhanli Hu
Many deep learning (DL)-based image restoration methods for low-dose CT (LDCT) problems directly employ the end-to-end networks on low-dose training data without considering dose differences. However, the radiation dose difference has a great impact on the ultimate results, and lower doses increase the difficulty of restoration. Moreover, there is increasing demand to design and estimate acceptable
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Automatic detection and segmentation of multiple brain metastases on magnetic resonance image using asymmetric UNet architecture Phys. Med. Biol. (IF 2.883) Pub Date : 2021-01-13 Yufeng Cao, April Vassantachart, Jason C Ye, Cheng Yu, Dan Ruan, Ke Sheng, Yi Lao, Zhilei Liu Shen, Salim Balik, Shelly Bian, Gabriel Zada, Almon Shiu, Eric L Chang and Wensha Yang
Detection of brain metastases is a paramount task in cancer management due both to the number of high-risk patients and the difficulty of achieving consistent detection. In this study, we aim to improve the accuracy of automated brain metastasis (BM) detection methods using a novel asymmetric UNet (asym-UNet) architecture. An end-to-end asymmetric 3D-UNet architecture, with two down-sampling arms and
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Probabilistic definition of the clinical target volume—implications for tumor control probability modeling and optimization Phys. Med. Biol. (IF 2.883) Pub Date : 2021-01-13 Thomas Bortfeld, Nadya Shusharina and David Craft
Evidence has been presented that moving beyond the binary definition of clinical target volume (CTV) towards a probabilistic CTV can result in better treatment plans. The probabilistic CTV takes the likelihood of disease spread outside of the gross tumor into account. An open question is: how to optimize tumor control probability (TCP) based on the probabilistic CTV. We derive expressions for TCP under
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Magnetic separation of iron oxide nanoparticles to improve their application for magnetic particle imaging Phys. Med. Biol. (IF 2.883) Pub Date : 2021-01-08 Soudabeh Arsalani, Norbert Löwa, Olaf Kosch, Patricia Radon, Oswaldo Baffa and Frank Wiekhorst
Magnetic particle imaging (MPI) is a promising medical imaging technique for visualizing the three-dimensional distribution of tracer materials, specifically iron oxide nanoparticles (IONP). The optimization of magnetic nanoparticles (MNP) plays an essential role to improve the image resolution and sensitivity of imaging techniques. Objective. In this work, the optimization of commercial IONP (EMG
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Reconstruction of dose distributions for fine carbon-ion beams using iterative approximation toward carbon-knife Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-23 Mutsumi Tashiro, Hikaru Souda, Takuya Yoshida and Hiroshi Sakurai
For the practical application of carbon-knife with fine carbon-ion beams, the quantification of the dose distribution is essential and requires a high spatial resolution. We propose a novel method to quantify dose distributions with a spatial resolution smaller than the dosimeter size. The proposed method innovates the iterative reconstruction technique. Using a diode dosimeter with a sensitive area
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Computational modelling of modern cancer immunotherapy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-23 Damijan Valentinuzzi and Robert Jeraj
Modern cancer immunotherapy has revolutionised oncology and carries the potential to radically change the approach to cancer treatment. However, numerous questions remain to be answered to understand immunotherapy response better and further improve the benefit for future cancer patients. Computational models are promising tools that can contribute to accelerated immunotherapy research by providing
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Comparison of deep learning synthesis of synthetic CTs using clinical MRI inputs Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-23 Haley A Massa, Jacob M Johnson and Alan B McMillan
There has been substantial interest in developing techniques for synthesizing CT-like images from MRI inputs, with important applications in simultaneous PET/MR and radiotherapy planning. Deep learning has recently shown great potential for solving this problem. The goal of this research was to investigate the capability of four common clinical MRI sequences (T1-weighted gradient-echo [T1], T2-weighted
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Evaluating attenuation correction strategies in a dedicated, single-gantry breast PET-tomosynthesis scanner Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-23 Srilalan Krishnamoorthy, Trevor Vent, Bruno Barufaldi, Andrew D A Maidment, Joel S Karp and Suleman Surti
We are developing a dedicated, combined breast positron emission tomography (PET)-tomosynthesis scanner. Both the PET and digital breast tomosynthesis (DBT) scanners are integrated in a single gantry to provide spatially co-registered 3D PET-tomosynthesis images. The DBT image will be used to identify the breast boundary and breast density to improve the quantitative accuracy of the PET image. This
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Practical joint reconstruction of activity and attenuation with autonomous scaling for time-of-flight PET Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-23 Yusheng Li, Samuel Matej and Joel S Karp
Recent research has showed that attenuation images can be determined from emission data, jointly with activity images, up to a scaling constant when utilizing the time-of-flight (TOF) information. We aim to develop practical CT-less joint reconstruction for clinical TOF PET scanners to obtain quantitatively accurate activity and attenuation images. In this work, we present a joint reconstruction of
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Design of a head coil for high resolution mouse brain perfusion imaging using magnetic particle imaging Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-23 Matthias Graeser, Peter Ludewig, Patryk Szwargulski, Fynn Foerger, Tom Liebing, Nils D Forkert, Florian Thieben, Tim Magnus and Tobias Knopp
Magnetic particle imaging (MPI) is a novel and versatile imaging modality developing toward human application. When up-scaling to human size, the sensitivity of the systems naturally drops as the coil sensitivity depends on the bore diameter. Thus, new methods to push the sensitivity limit further have to be investigated to cope for this loss. In this paper a dedicated surface coil for mice is developed
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Liver-ultrasound based motion modelling to estimate 4D dose distributions for lung tumours in scanned proton therapy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Giger Alina, Miriam Krieger, Christoph Jud, Alisha Duetschler, Rares Salomir, Oliver Bieri, Grzegorz Bauman, Damien Nguyen, Damien C Weber, Antony J Lomax, Ye Zhang and Philippe C Cattin
Motion mitigation strategies are crucial for scanned particle therapy of mobile tumours in order to prevent geometrical target miss and interplay effects. We developed a patient-specific respiratory motion model based on simultaneously acquired time-resolved volumetric MRI and 2D abdominal ultrasound images. We present its effects on 4D pencil beam scanned treatment planning and simulated dose distributions
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Monte Carlo calculation of quality correction factors based on air kerma and absorbed dose to water in medium energy x-ray beams Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Damian Czarnecki, Klemens Zink, Maria Pimpinella, Jorge Borbinha, Pedro Teles and Massimo Pinto
Clinical dosimetry is typically performed using ion chambers calibrated in terms of absorbed dose to water. As primary measurement standards for this quantity for low and medium energy x-rays are available only since a few years, most dosimetry protocols for this photon energy range are still based on air kerma calibration. For that reason, data for beam quality correction factors ##IMG## [http://ej
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Optimal treatment plan adaptation using mid-treatment imaging biomarkers Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 S C M ten Eikelder, P Ferjančič, A Ajdari, T Bortfeld, D den Hertog and R Jeraj
Previous studies on personalized radiotherapy (RT) have mostly focused on baseline patient stratification, adapting the treatment plan according to mid-treatment anatomical changes, or dose boosting to selected tumor subregions using mid-treatment radiological findings. However, the question of how to find the optimal adapted plan has not been properly tackled. Moreover, the effect of information uncertainty
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Dense feature-based motion estimation in MV fluoroscopy during dynamic tumor tracking treatment: preliminary study on reduced aperture and partial occlusion handling Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Marco Serpa and Christoph Bert
Quality assurance solutions to complement available motion compensation technologies are central for their safe routine implementation and success of treatment. This work presents a dense feature-based method for soft-tissue tumor motion estimation in megavoltage (MV) beam’s-eye-view (BEV) projections for potential intra-treatment monitoring during dynamic tumor tracking (DTT). Dense sampling and matching
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Experimental determination of magnetic field correction factors for ionization chambers in parallel and perpendicular orientations Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Stefan Pojtinger, Marcel Nachbar, Sarah Ghandour, Olivier Pisaturo, Marc Pachoud, Ralf-Peter Kapsch and Daniela Thorwarth
Magnetic field correction factors are needed for absolute dosimetry in magnetic resonance (MR)-linacs. Currently experimental data for magnetic field correction factors, especially for small volume ionization chambers, are largely lacking. The purpose of this work is to establish, independent methods for the experimental determination of magnetic field correction factors ##IMG## [http://ej.iop.org
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A novel method for calibrating head models to account for variability in conductivity and its evaluation in a sphere model Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 S Schrader, M Antonakakis, S Rampp, C Engwer and C H Wolters
The accuracy in electroencephalography (EEG) and combined EEG and magnetoencephalography (MEG) source reconstructions as well as in optimized transcranial electric stimulation (TES) depends on the conductive properties assigned to the head model, and most importantly on individual skull conductivity. In this study, we present an automatic pipeline to calibrate head models with respect to skull conductivity
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Model-based dual-energy tomographic image reconstruction of objects containing known metal components Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Stephen Z Liu, Qian Cao, Matthew Tivnan, Steven Tilley II, Jeffrey H Siewerdsen, J Webster Stayman and Wojciech Zbijewski
Dual-energy (DE) decomposition has been adopted in orthopedic imaging to measure bone composition and visualize intraarticular contrast enhancement. One of the potential applications involves monitoring of callus mineralization for longitudinal assessment of fracture healing. However, fracture repair usually involves internal fixation hardware that can generate significant artifacts in reconstructed
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Microdosimetry of a therapeutic proton beam with a mini-TEPC and a MicroPlus-Bridge detector for RBE assessment Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 V Conte, S Agosteo, A Bianchi, D Bolst, D Bortot, R Catalano, G A P Cirrone, P Colautti, G Cuttone, S Guatelli, B James, D Mazzucconi, A B Rosenfeld, A Selva, L Tran and G Petringa
Proton beams are widely used worldwide to treat localized tumours, the lower entrance dose and no exit dose, thus sparing surrounding normal tissues, being the main advantage of this treatment modality compared to conventional photon techniques. Clinical proton beam therapy treatment planning is based on the use of a general relative biological effectiveness (RBE) of 1.1 along the whole beam penetration
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Patient-specific CT calibration based on ion radiography for different detector configurations in 1 H, 4 He and 12 C ion pencil beam scanning Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Chiara Gianoli, Maximilian Göppel, Sebastian Meyer, Prasannakumar Palaniappan, Martin Rädler, Florian Kamp, Claus Belka, Marco Riboldi and Katia Parodi
The empirical conversion of the treatment planning x-ray computed tomography (CT) image to ion stopping power relative to water causes dose calculation inaccuracies in ion beam therapy. A patient-specific calibration of the CT image is enabled by the combination of an ion radiography (iRad) with the forward-projection of the empirically converted CT image along the estimated ion trajectories. This
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MACACO II test-beam with high energy photons Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 A Ros García, J Barrio, A Etxebeste, J García López, M C Jiménez-Ramos, C Lacasta, E Muñoz, J F Oliver, J Roser and G Llosá
The IRIS group at IFIC Valencia is developing a three-layer Compton camera for treatment monitoring in proton therapy. The system is composed of three detector planes, each made of a ##IMG## [http://ej.iop.org/images/0031-9155/65/24/245027/pmbabc5cdieqn1.gif] {$\mathrm{LaBr_3}$} monolithic crystal coupled to a SiPM array. Having obtained successful results with the first prototype (MACACO) that demonstrated
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Monte Carlo calculation of the relative TG-43 dosimetry parameters for the INTRABEAM electronic brachytherapy source Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 David Santiago Ayala Alvarez, Peter G F Watson, Marija Popovic, Veng Jean Heng, Michael D C Evans and Jan Seuntjens
The INTRABEAM system (Carl Zeiss Meditec AG, Jena, Germany) is an electronic brachytherapy (eBT) device designed for intraoperative radiotherapy applications. To date, the INTRABEAM x-ray source has not been characterized according to the AAPM TG-43 specifications for brachytherapy sources. This restricts its modelling in commercial treatment planning systems (TPSs), with the consequence that the doses
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Data-driven dose calculation algorithm based on deep U-Net Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Jiawei Fan, Lei Xing, Peng Dong, Jiazhou Wang, Weigang Hu and Yong Yang
Accurate and efficient dose calculation is an important prerequisite to ensure the success of radiation therapy. However, all the dose calculation algorithms commonly used in current clinical practice have to compromise between calculation accuracy and efficiency, which may result in unsatisfactory dose accuracy or highly intensive computation time in many clinical situations. The purpose of this work
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IPEM topical report: current molecular radiotherapy service provision and guidance on the implications of setting up a dosimetry service Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Allison J Craig, Bruno Rojas, Jill L Wevrett, Elaine Hamer, Andrew Fenwick and Rebecca Gregory
Despite a growth in molecular radiotherapy treatment (MRT) and an increase in interest, centres still rarely perform MRT dosimetry. The aims of this report were to assess the main reasons why centres are not performing MRT dosimetry and provide advice on the resources required to set-up such a service. A survey based in the United Kingdom was developed to establish how many centres provide an MRT dosimetry
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Segmentation and classification of thyroid follicular neoplasm using cascaded convolutional neural network Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Bailin Yang, Meiying Yan, Zaoming Yan, Changrui Zhu, Dong Xu and Fangfang Dong
In this paper, we present a segmentation and classification method for thyroid follicular neoplasms based on a combination of the prior-based level set method and deep convolutional neural network. The proposed method aims to discriminate thyroid follicular adenoma (TFA) and follicular thyroid carcinoma (FTC) in ultrasound images. In their appearance, these two kinds of tumours have similar shapes
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Noncontact optical imaging of brain hemodynamics in preterm infants: a preliminary study Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Elie G Abu Jawdeh, Chong Huang, Siavash Mazdeyasna, Lei Chen, Li Chen, Henrietta S Bada and Guoqiang Yu
Extremely preterm infants’ hemodynamic instability places them at high risk of brain injury. Currently there is no reliable bedside method to continuously monitor cerebral hemodynamics in the neonatal intensive care unit (NICU). This paper reports a feasibility study to adapt and test an innovative speckle contrast diffuse correlation tomography (scDCT) device for noncontact, high-density, 3D imaging
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On the robustness of deep learning-based lung-nodule classification for CT images with respect to image noise Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 Chenyang Shen, Min-Yu Tsai, Liyuan Chen, Shulong Li, Dan Nguyen, Jing Wang, Steve B Jiang and Xun Jia
Robustness is an important aspect when evaluating a method of medical image analysis. In this study, we investigated the robustness of a deep learning (DL)-based lung-nodule classification model for CT images with respect to noise perturbations. A deep neural network (DNN) was established to classify 3D CT images of lung nodules into malignant or benign groups. The established DNN was able to predict
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Beam characterization and feasibility study for a small animal irradiation platform at clinical proton therapy facilities Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-22 S Gerlach, M Pinto, N Kurichiyanil, C Grau, J Hérault, M Hillbrand, P R Poulsen, S Safai, J M Schippers, M Schwarz, C S Søndergaard, F Tommasino, E Verroi, M Vidal, I Yohannes, J Schreiber and K Parodi
A deeper understanding of biological mechanisms to promote more efficient treatment strategies in proton therapy demands advances in preclinical radiation research. However this is often limited by insufficient availability of adequate infrastructures for precision image guided small animal proton irradiation. The project SIRMIO aims at filling this gap by developing a portable image-guided research
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A digital phoswich detector using time-over-threshold for depth of interaction in PET Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-15 David L Prout, Zheng Gu, Max Shustef and Arion F Chatziioannou
We present the performance of a digital phoswich positron emission tomography (PET) detector, composed by layers of pixilated scintillator arrays, read out by solid state light detectors and an application specific integrated circuit (ASIC). We investigated the use of integrated charge from the scintillation pulses along with time-over-threshold (ToT) to determine the layer of interaction (DOI) in
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Fast and automatic periacetabular osteotomy fragment pose estimation using intraoperatively implanted fiducials and single-view fluoroscopy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-12 R B Grupp, R J Murphy, R A Hegeman, C P Alexander, M Unberath, Y Otake, B A McArthur, M Armand and R H Taylor
Accurate and consistent mental interpretation of fluoroscopy to determine the position and orientation of acetabular bone fragments in 3D space is difficult. We propose a computer assisted approach that uses a single fluoroscopic view and quickly reports the pose of an acetabular fragment without any user input or initialization. Intraoperatively, but prior to any osteotomies, two constellations of
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Surrogate-free machine learning-based organ dose reconstruction for pediatric abdominal radiotherapy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-12 M Virgolin, Z Wang, B V Balgobind, I W E M van Dijk, J Wiersma, P S Kroon, G O Janssens, M van Herk, D C Hodgson, L Zadravec Zaletel, C R N Rasch, A Bel, P A N Bosman and T Alderliesten
To study radiotherapy-related adverse effects, detailed dose information (3D distribution) is needed for accurate dose-effect modeling. For childhood cancer survivors who underwent radiotherapy in the pre-CT era, only 2D radiographs were acquired, thus 3D dose distributions must be reconstructed from limited information. State-of-the-art methods achieve this by using 3D surrogate anatomies. These can
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Feasibility of quasi-prompt PET-based range verification in proton therapy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-11 Ikechi Ozoemelam, Emiel van der Graaf, Marc-Jan van Goethem, Maciej Kapusta, Nan Zhang, Sytze Brandenburg and Peter Dendooven
Compared to photon therapy, proton therapy allows a better conformation of the dose to the tumor volume with reduced radiation dose to co-irradiated tissues. In vivo verification techniques including positron emission tomography (PET) have been proposed as quality assurance tools to mitigate proton range uncertainties. Detection of differences between planned and actual dose delivery on a short timescale
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Motion-flow-guided recurrent network for respiratory signal estimation of x-ray angiographic image sequences Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-11 Huihui Fang, Heng Li, Shuang Song, Kun Pang, Danni Ai, Jingfan Fan, Hong Song, Yang Yu and Jian Yang
Motion compensation can eliminate inconsistencies of respiratory movement during image acquisitions for precise vascular reconstruction in the clinical diagnosis of vascular disease from x-ray angiographic image sequences. In x-ray-based vascular interventional therapy, motion modeling can simulate the process of organ deformation driven by motion signals to display a dynamic organ on angiograms without
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A dual-domain deep learning-based reconstruction method for fully 3D sparse data helical CT Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-11 Ao Zheng, Hewei Gao, Li Zhang and Yuxiang Xing
Helical CT has been widely used in clinical diagnosis. In this work, we focus on a new prototype of helical CT, equipped with sparsely spaced multidetector and multi-slit collimator (MSC) in the axis direction. This type of system can not only lower radiation dose, and suppress scattering by MSC, but also cuts down the manufacturing cost of the detector. The major problem to overcome with such a system
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Assessing the advantages of CFR-PEEK over titanium spinal stabilization implants in proton therapy—a phantom study Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-11 R Poel, F Belosi, F Albertini, M Walser, A Gisep, A J Lomax and D C Weber
High-density materials, such as titanium, used for spinal stabilization, introduces several critical issues in proton therapy (PT). Artefacts affect both contouring and dose calculation. Subsequently, artefacts need to be corrected which is a time-consuming process. Besides, titanium causes proton interactions that are unaccounted for in dose calculation. The result is a suboptimal treatment plan,
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Self-channel-and-spatial-attention neural network for automated multi-organ segmentation on head and neck CT images. Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-11 Shuiping Gou,Nuo Tong,Sharon X Qi,Shuyuan Yang,Robert K Chin,Ke Sheng
Accurate segmentation of organs at risk (OARs) is necessary for adaptive head and neck (H&N) cancer treatment planning, but manual delineation is tedious, slow, and inconsistent. A self-channel-and-spatial-attention neural network (SCSA-Net) is developed for H&N OAR segmentation on CT images. To simultaneously ease the training and improve the segmentation performance, the proposed SCSA-Net utilizes
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Direct determination of ##IMG## [http://ej.iop.org/images/0031-9155/65/23/235049/toc_pmbabab56ieqn1.gif] {${k_{\vec B,Q,{Q_0}}}$} for cylindrical ionization chambers in a 6 MV 0.35 T MR-linac Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-10 A Krauss, C K Spindeldreier and S Klüter
To ensure accurate reference dosimetry with ionization chambers in magnetic resonance linear accelerators (MR-linacs), the influence of the magnetic field on the response of the ionization chambers must be considered. The most direct method considering the influence of magnetic fields in dosimetry is to apply an appropriate absorbed-dose-to-water primary standard. At PTB, a new water calorimeter has
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A kinetic model of continuous radiation damage to populations of cells: comparison to the LQ model and application to molecular radiotherapy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-10 Sara Neira, Araceli Gago-Arias, Jacobo Guiu-Souto and Juan Pardo-Montero
The linear-quadratic (LQ) model to describe the survival of irradiated cells may be the most frequently used biomathematical model in radiotherapy. There has been an intense debate on the mechanistic origin of the LQ model. An interesting approach is that of obtaining LQ-like behavior from kinetic models, systems of differential equations that model the induction and repair of damage. Development of
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Characterization of a preclinical PET insert in a 7 tesla MRI scanner: beyond NEMA testing Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-10 Willy Gsell, Cesar Molinos, Carlos Correcher, Sarah Belderbos, Jens Wouters, Sven Junge, Michael Heidenreich, Greetje Vande Velde, Ahmadreza Rezaei, Johan Nuyts, Christopher Cawthorne, Frederik Cleeren, Lise Nannan, Christophe M Deroose, Uwe Himmelreich and Antonio J Gonzalez
This study evaluates the performance of the Bruker positron emission tomograph (PET) insert combined with a BioSpec 70/30 USR magnetic resonance imaging (MRI) scanner using the manufacturer acceptance protocol and the NEMA NU 4–2008 for small animal PET. The PET insert is made of 3 rings of 8 monolithic LYSO crystals (50 × 50 × 10 mm 3 ) coupled to silicon photomultipliers (SiPM) arrays, conferring
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Fast mixed integer optimization (FMIO) for high dose rate brachytherapy Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-07 Majd Antaki, Christopher L Deufel and Shirin A Enger
The purpose of this work was to develop an efficient quadratic mixed integer programming algorithm for high dose rate (HDR) brachytherapy treatment planning problems and integrate the algorithm into an open-source Monte Carlo based treatment planning software, RapidBrachyMCTPS. The mixed-integer algorithm yields a globally optimum solution to the dose volume histogram (DVH) based problem and, unlike
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Impact of scanner harmonization on PET-based treatment response assessment in metastatic melanoma Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-07 Amy J Weisman, Tyler J Bradshaw, Mauro Namias and Robert Jeraj
Patients with metastatic melanoma often receive 18 F-FDG PET/CT scans on different scanners throughout their monitoring period. In this study, we quantified the impact of scanner harmonization on longitudinal changes in PET standardized uptake values using various harmonization and normalization methods, including an anthropomorphic PET phantom. Twenty metastatic melanoma patients received at least
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Clinical translation of a new flat-panel detector for beam’s-eye-view imaging Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-07 TC Harris, J Seco, D Ferguson, M Lehmann, P Huber, M Shi, M Jacobson, I Valencia Lozano, M Myronakis, P Baturin, R Fueglistaller, D Morf and R Berbeco
Electronic portal imaging devices (EPIDs) lend themselves to beams-eye view clinical applications, such as tumor tracking, but are limited by low contrast and detective quantum efficiency (DQE). We characterize a novel EPID prototype consisting of multiple layers and investigate its suitability for use under clinical conditions. A prototype multi-layer imager (MLI) was constructed utilizing four conventional
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IPEM Topical Report: An evidence and risk assessment based analysis of the efficacy of quality assurance tests on fluoroscopy units—part II; image quality Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Dan Shaw, Mark Worrall, Chris Baker, Paul Charnock, Jason Fazakerley, Ian Honey, Gareth Iball, Manthos Koutalonis, Mandy Price, Caroline Renaud, Amy Rose and Tim Wood
This work aims to assess the efficacy of x-ray quality assurance tests undertaken on fluoroscopy units in the UK. Information was gathered on the results of image quality tests recommended by the reports of the Institute of Physics and Engineering in Medicine, and those additionally undertaken by medical physics departments. The assessment of efficacy considers the frequency with which a test result
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Comparison of the suitability of CBCT- and MR-based synthetic CTs for daily adaptive proton therapy in head and neck patients Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Adrian Thummerer, Bas A de Jong, Paolo Zaffino, Arturs Meijers, Gabriel Guterres Marmitt, Joao Seco, Roel J H M Steenbakkers, Johannes A Langendijk, Stefan Both, Maria F Spadea and Antje C Knopf
Cone-beam computed tomography (CBCT)- and magnetic resonance (MR)-images allow a daily observation of patient anatomy but are not directly suited for accurate proton dose calculations. This can be overcome by creating synthetic CTs (sCT) using deep convolutional neural networks. In this study, we compared sCTs based on CBCTs and MRs for head and neck (H&N) cancer patients in terms of image quality
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MD-NDNet: a multi-dimensional convolutional neural network for false-positive reduction in pulmonary nodule detection Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Zhan Wu, Rongjun Ge, Gonglei Shi, Lu Zhang, Yang Chen, Limin Luo, Yu Cao and Hengyong Yu
Pulmonary nodule false-positive reduction is of great significance for automated nodule detection in clinical diagnosis of low-dose computed tomography (LDCT) lung cancer screening. Due to individual intra-nodule variations and visual similarities between true nodules and false positives as soft tissues in LDCT images, the current clinical practices remain subject to shortcomings of potential high-risk
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Dose quantification in carbon ion therapy using in-beam positron emission tomography Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Harley Rutherford, Andrew Chacon, Akram Mohammadi, Sodai Takyu, Hideaki Tashima, Eiji Yoshida, Fumihiko Nishikido, Theresa Hofmann, Marco Pinto, Daniel R Franklin, Taiga Yamaya, Katia Parodi, Anatoly B Rosenfeld, Susanna Guatelli and Mitra Safavi-Naeini
This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three
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Low-dose spectral CT reconstruction based on image-gradient L 0 -norm and adaptive spectral PICCS Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Shaoyu Wang, Weiwen Wu, Jian Feng, Fenglin Liu and Hengyong Yu
The photon-counting detector based spectral computed tomography (CT) is promising for lesion detection, tissue characterization, and material decomposition. However, the lower signal-to-noise ratio within multi-energy projection dataset can result in poorly reconstructed image quality. Recently, as prior information, a high-quality spectral mean image was introduced into the prior image constrained
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Dictionary learning based image-domain material decomposition for spectral CT Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Weiwen Wu, Haijun Yu, Peijun Chen, Fulin Luo, Fenglin Liu, Qian Wang, Yining Zhu, Yanbo Zhang, Jian Feng and Hengyong Yu
The potential huge advantage of spectral computed tomography (CT) is that it can provide accurate material identification and quantitative tissue information by material decomposition. However, material decomposition is a typical inverse problem, where the noise can be magnified. To address this issue, we develop a dictionary learning based image-domain material decomposition (DLIMD) method for spectral
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Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Francis Loignon-Houle, Maxime Toussaint, Min Sun Lee, Joshua W. Cates and Roger Lecomte
Depth-of-interaction (DOI) variability of annihilation photons is known to be a source of coincidence time resolution (CTR) degradation for fast time-of-flight–positron emission tomography detectors. An analytical model was recently proposed to explicitly include the DOI time bias separately from variance-related statistical factors, such as scintillation photon emission and photosensor jitter, in
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A dedicated phantom design for positron emission mammography performance evaluation Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-05 Luis Fernando Torres-Urzúa, Héctor Alva-Sánchez, Arnulfo Martínez-Dávalos, Francisco Osvaldo García-Pérez, Rocío Marlene Peruyero-Rivas and Mercedes Rodríguez-Villafuerte
A standard protocol for performance evaluation of positron emission mammography (PEM) systems has not yet been established. In this work we propose a methodology based on the design of specific phantoms for this imaging modality with component dimensions in accordance with typical breast lesion sizes together with the adaptation of current international protocols designed for clinical and preclinical
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Polaroid-PET: a PET scanner with detectors fitted with Polaroid for filtering unpolarized optical photons—a Monte Carlo simulation study Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Amirhossein Sanaat, Aydin Ashrafi-Belgabad and Habib Zaidi
We propose and evaluate the performance of an improved preclinical positron emission tomography (PET) scanner design, referred to as Polaroid-PET, consisting of a detector equipped with a layer of horizontal Polaroid to filter scintillation photons with vertical polarization. This makes it possible to improve the spatial resolution of PET scanners based on monolithic crystals. First, a detector module
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Monte Carlo implementation of new algorithms for the evaluation of averaged-dose and -track linear energy transfers in 62 MeV clinical proton beams Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 G Petringa, L Pandola, S Agosteo, R Catalano, P Colautti, V Conte, G Cuttone, K Fan, Z Mei, A Rosenfeld, A Selva and GAP Cirrone
We exploited the power of the Geant4 Monte Carlo toolkit to study and validate new approaches for the averaged linear energy transfer (LET) calculation in 62 MeV clinical proton beams. The definitions of the averaged LET dose and LET track were extended, so as to fully account for the contribution of secondary particles generated by target fragmentation, thereby leading to a more general formulation
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Geometric uncertainty analysis of MLC tracking for lung SABR Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Vincent Caillet, Benjamin Zwan, Adam Briggs, Nicholas Hardcastle, Kathryn Szymura, Alexander Prodreka, Ricky O’Brien, Ben E Harris, Peter Greer, Carol Haddad, Dasantha Jayamanne, Thomas Eade, Jeremy Booth and Paul Keall
Purpose. The purpose of this work was to report on the geometric uncertainty for patients treated with multi-leaf collimator (MLC) tracking for lung SABR to verify the accuracy of the system. Methods. Seventeen patients were treated as part of the MLC tracking for lung SABR clinical trial using electromagnetic beacons implanted around the tumor acting as a surrogate for target motion. Sources of uncertainties
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Attenuation correction for human PET/MRI studies Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Ciprian Catana
Attenuation correction has been one of the main methodological challenges in the integrated positron emission tomography and magnetic resonance imaging (PET/MRI) field. As standard transmission or computed tomography approaches are not available in integrated PET/MRI scanners, MR-based attenuation correction approaches had to be developed. Aspects that have to be considered for implementing accurate
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Specific absorbed fractions and radionuclide S-values for tumors of varying size and composition Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Edmond Olguin, Bonnie President, Michael Ghaly, Eric Frey, George Sgouros and Wesley E Bolch
Accurate estimates of tumor absorbed dose are essential for the evaluation of treatment efficacy in radiopharmaceutical cancer therapy. Although tumor dosimetry via the MIRD schema has been previously investigated, prior studies have been limited to the consideration of soft-tissue tumors. In the present study, specific absorbed fractions (SAFs) for monoenergetic photons, electrons, and alpha particles
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Dosimetric considerations of 99m Tc-MDP uptake within the epiphyseal plates of the long bones of pediatric patients Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Justin L Brown, Briana Sexton-Stallone, Ye Li, Eric C Frey, S Ted Treves, Frederic H Fahey, Donika Plyku, Xinhua Cao, Chansoo Choi, Chan Hyeong Kim, George Sgouros, John P Aris and Wesley E Bolch
Skeletal scintigraphy is most performed in pediatric patients using the radiopharmaceutical 99m Tc labelled methylene diphosphonate ( 99m Tc-MDP). Reference biokinetic models for 99m Tc-MDP indicate 50% of the administered activity is uniformly localized to the interior bone surfaces (trabecular and cortical regions), yet imaging data clearly show some preferential uptake to the epiphyseal growth plates
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A wavelet transform-based photon starvation artifacts suppression algorithm in CT imaging Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Shilei Hao, Jin Liu, Yang Chen, Baodong Liu, Cunfeng Wei, Jian Zhu and Baosheng Li
In computed tomography, high attenuation occurs when x-rays pass through a dense region or a long path in the scanning object. In this case, only limited photons reach the detector, which causes photon starvation artifacts. The artifacts usually appear as streaks along the directions with high attenuation. It might lower the discrimination of minor structures and lead to misdiagnosis. Applying a local
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GPU-accelerated Monte Carlo simulation of MV-CBCT Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Mengying Shi, Marios Myronakis, Matthew Jacobson, Dianne Ferguson, Christopher Williams, Mathias Lehmann, Paul Baturin, Pascal Huber, Rony Fueglistaller, Ingrid Valencia Lozano, Thomas Harris, Daniel Morf and Ross I Berbeco
Monte Carlo simulation (MCS) is one of the most accurate computation methods for dose calculation and image formation in radiation therapy. However, the high computational complexity and long execution time of MCS limits its broad use. In this paper, we present a novel strategy to accelerate MCS using a graphic processing unit (GPU), and we demonstrate the application in mega-voltage (MV) cone-beam
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An unsupervised deep learning method for multi-coil cine MRI Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Ziwen Ke, Jing Cheng, Leslie Ying, Hairong Zheng, Yanjie Zhu and Dong Liang
Deep learning has achieved good success in cardiac magnetic resonance imaging (MRI) reconstruction, in which convolutional neural networks (CNNs) learn a mapping from the undersampled k-space to the fully sampled images. Although these deep learning methods can improve the reconstruction quality compared with iterative methods without requiring complex parameter selection or lengthy reconstruction
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Motion correction for PET data using subspace-based real-time MR imaging in simultaneous PET/MR Phys. Med. Biol. (IF 2.883) Pub Date : 2020-12-02 Thibault Marin, Yanis Djebra, Paul K Han, Yanis Chemli, Isabelle Bloch, Georges El Fakhri, Jinsong Ouyang, Yoann Petibon and Chao Ma
Image quality of positron emission tomography (PET) reconstructions is degraded by subject motion occurring during the acquisition. Magnetic resonance (MR)-based motion correction approaches have been studied for PET/MR scanners and have been successful at capturing regular motion patterns, when used in conjunction with surrogate signals (e.g. navigators) to detect motion. However, handling irregular
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