15,394 results match your criteria Medical Physics[Journal]


Three-dimensional Therapy Needle Applicator Segmentation for Ultrasound-guided Focal Liver Ablation.

Med Phys 2019 Apr 17. Epub 2019 Apr 17.

Department of Medical Biophysics.

Purpose: Minimally invasive procedures, such as microwave ablation, are becoming first-line treatment options for early-stage liver cancer due to lower complication rates and shorter recovery times than conventional surgical techniques. Although these procedures are promising, one reason preventing widespread adoption is inadequate local tumour ablation leading to observations of higher local cancer recurrence compared to conventional procedures. Poor ablation coverage has been associated with two-dimensional (2D) ultrasound (US) guidance of the therapy needle applicators and has stimulated investigation into the use of three-dimensional (3D) US imaging for these procedures. Read More

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http://dx.doi.org/10.1002/mp.13548DOI Listing

Comparison of GPU Reconstruction based on Different Symmetries for Dual-head PET.

Med Phys 2019 Apr 17. Epub 2019 Apr 17.

Engineering Research Center of Molecular and Neuro Imaging of Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China.

Purpose: Dual-head positron emission tomography (PET) scanners have increasingly attracted the attention of many researchers. However, with the compact geometry, the depth-of-interaction (DOI) blurring will reduce the image resolution considerably. Monte Carlo (MC) based system response matrix (SRM) is able to describe the physical process of PET imaging accurately and improve reconstruction quality significantly. Read More

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http://dx.doi.org/10.1002/mp.13529DOI Listing

SparseCT: System Concept and Design of Multi-slit Collimators.

Med Phys 2019 Apr 13. Epub 2019 Apr 13.

Department of Radiology, NYU School of Medicine, New York, NY, USA, 10016.

Purpose: SparseCT, an undersampling scheme for compressed sensing CT, has been proposed to reduce radiation dose by acquiring undersampled projection data from clinical CT scanners . SparseCT partially blocks the x-ray beam with a multi-slit collimator (MSC) to perform a multidimensional undersampling along the view and detector row dimensions. SparseCT undersamples the projection data within each view and moves the MSC along the z direction during gantry rotation to change the undersampling pattern. Read More

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http://doi.wiley.com/10.1002/mp.13544
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http://dx.doi.org/10.1002/mp.13544DOI Listing
April 2019
5 Reads

Cherenkov-excited luminescence scanned imaging using scanned beam differencing and iterative deconvolution in dynamic plan radiation delivery in a human breast phantom geometry.

Med Phys 2019 Apr 13. Epub 2019 Apr 13.

Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, 03755, USA.

Purpose: The purpose of this study was to demonstrate high resolution optical luminescence sensing, referred to as Cherenkov excited luminescence scanning imaging (CELSI), could be achieved during a standard dynamic treatment plan for a whole breast radiotherapy geometry.

Methods: The treatment plan beams induce Cherenkov light within tissue, and this excitation projects through the beam trajectory across the medium, inducing luminescence where there can be molecular reporter. Broad beams generally produce higher signal but low spatial resolution, yet for dynamic plans the scanning of the multi-leaf collimator allows for a beam-narrowing strategy by recursively temporal differencing each of the Cherenkov images and associated luminescence images. Read More

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http://dx.doi.org/10.1002/mp.13545DOI Listing

Application of Failure Mode and Effects Analysis to optimization of linac quality controls protocol.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Medical Physics Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, via Venezian 1, 20133, Milan, Italy.

Purpose: To apply Failure Mode and Effects Analysis (FMEA) to optimize linac quality control (QC) protocol in order to ensure patient safety and treatment quality, taking maximum advantage of the available resources.

Material And Methods: Each parameter tested by the QC was considered as a potential failure mode (FM). For each FM, likelihood of occurrence (O), severity of effect (S) and lack of detectability (D) were evaluated and corresponding Risk Priority Number (RPN) was calculated from the product of three indexes. Read More

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http://dx.doi.org/10.1002/mp.13538DOI Listing

Technical Note: Noise models for virtual clinical trials of digital breast tomosynthesis.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Department of Electrical and Computer Engineering, University of São Paulo, São Carlos, SP, 13566-590, Brazil.

Purpose: To investigate the use of an affine-variance noise model, with correlated quantum noise and spatially-dependent quantum gain, for the simulation of noise in virtual clinical trials (VCT) of digital breast tomosynthesis (DBT).

Methods: Two distinct technologies were considered: an amorphous-selenium (a-Se) detector with direct conversion, and a thallium doped cesium iodide (CsI(Tl)) detector with indirect conversion. A VCT framework was used to generate noise-free projections of a uniform 3D simulated phantom, whose geometry and absorption match those of a poly methyl methacrylate (PMMA) uniform physical phantom. Read More

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http://dx.doi.org/10.1002/mp.13534DOI Listing

Technical Note: Assessing the performance of monthly CBCT image quality QA.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Department of Radiation Medicine and Applied Sciences, University of California San Diego, 3855 Health Sciences Dr, La Jolla, CA, USA, 92093.

Purpose: To assess the performance of routine CBCT quality assurance (QA) at predicting and diagnosing clinically recognizable linac CBCT image quality issues.

Methods: Monthly automated linac CBCT image quality QA data were acquired on eight Varian linacs (Varian Medical Systems, Palo Alto, CA) using the CATPHAN 500 series phantom (The Phantom Laboratory, Inc., Greenwich, NY) and Total QA software (Image Owl, Inc. Read More

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http://dx.doi.org/10.1002/mp.13535DOI Listing
April 2019
1 Read

Full convolutional networks based multiple side-output fusion architecture for the segmentation of rectal tumors in magnetic resonance images: a multi-vendor study.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Department of Radiology, The Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, 510655, China.

Purpose: Accurate segmentation of rectal tumors is a basic and crucial task for diagnosis and treatment of rectal cancer. To avoid tedious manual delineation, an automatic rectal tumor segmentation model is proposed.

Methods: A pre-trained Resnet50 model was introduced for feature extraction. Read More

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http://dx.doi.org/10.1002/mp.13541DOI Listing

Technical Note: Characterization of Technology to Detect Residual Injection Site Radioactivity.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Lucerno Dynamics, LLC, 140 Towerview Ct., Cary, NC, 27513, United States of America.

Each year in the United States, approximately 18.5 million nuclear medicine procedures are performed. Various quality control measures are implemented to reduce image errors and improve quantification of radiotracer distribution. Read More

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https://onlinelibrary.wiley.com/doi/abs/10.1002/mp.13536
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http://dx.doi.org/10.1002/mp.13536DOI Listing
April 2019
1 Read

Impact of calibration methods for color medical displays on interpreting brain SPECT images.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

EIZO Corporation, Hakusan, Ishikawa, 924-8566, Japan.

Purpose: Color images are visualized on medical monitors that are adjusted by a grayscale standard display function (GSDF) or γ2.2. Although the GSDF is visually displayed as a linear graded grayscale, it does not specify how color medical images should be presented. Read More

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http://dx.doi.org/10.1002/mp.13532DOI Listing

Quantitative breast elastography from B-mode images.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Instituto de Física, Facultad de Ciencias, Iguá, 4225, 11400, Montevideo, Uruguay.

Purpose: Elastography images provide information about the mechanical properties of soft tissue in a non-invasive way and can be useful to identify abnormalities and ascertain differential diagnoses of suspicious prior findings obtained through mammography ultrasound. In this work we investigate, from a physics point of view, the feasibility of quantifying the Young's modulus of breast tissue from the auto-correlation of a diffuse acoustic field computed from a sequence of B-mode images acquired through conventional ultrasound scanners.

Methods: Inspired in the seismological approach of retrieving the Green's function by cross-correlation of diffuse fields, we obtained a quantitative expression that relates the local shear modulus of soft tissue to the auto-correlation of the displacement field generated by the presence of an acoustic diffuse field in the medium. Read More

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http://dx.doi.org/10.1002/mp.13537DOI Listing

An Extended Dose-Volume Model in High Dose-Rate Brachytherapy - Using Mean-Tail-Dose to Reduce Tumour Underdosage.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

Radiation Physics, Department of Medical and Health Sciences, Linkӧping University, SE-58185, Linkӧping, Sweden.

Purpose: High dose-rate brachytherapy is a method of radiotherapy for cancer treatment in which the radiation source is placed within the body. In addition to give a high enough dose to a tumour, it is also important to spare nearby healthy organs (organs at risk). Dose plans are commonly evaluated using so-called dosimetric indices; for the tumour, the portion of the structure that receives a sufficiently high dose is calculated, while for organs at risk it is instead the portion of the structure that receives a sufficiently low dose that is of interest. Read More

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http://dx.doi.org/10.1002/mp.13533DOI Listing
April 2019
1 Read

The role of radiation induced charge imbalance on the dose response of a commercial synthetic diamond detector in small field dosimetry.

Med Phys 2019 Apr 11. Epub 2019 Apr 11.

University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany.

Purpose: Discrepancy between experimental and Monte-Carlo simulated dose response of the microDiamond (mD) detector (type 60019, PTW Freiburg, Germany) at small field sizes has been reported. In this work, the radiation induced charge imbalance in the structural components of the detector has been investigated as the possible cause of this discrepancy.

Materials And Methods: Output ratio (OR) measurements have been performed using standard and modified versions of the mD detector at nominal field sizes from 6 mm x 6 mm to 40 mm x 40 mm. Read More

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http://dx.doi.org/10.1002/mp.13542DOI Listing

Knowledge-Based Planning for Intensity Modulated Radiation Therapy: A Review of Data-Driven Approaches.

Med Phys 2019 Apr 8. Epub 2019 Apr 8.

Department of Radiation Oncology, Duke University Medical Center, Durham, NC, 27710, USA.

Purpose: Intensity Modulated Radiation Therapy (IMRT) including its variations (including IMRT, VMAT, and Tomotherapy) is a widely used and critically important technology for cancer treatment. It is a knowledge intensive technology due not only to its own technical complexity, but also to the inherently conflicting nature of maximizing tumor control while minimizing normal organ damage. As IMRT experience and especially the carefully designed clinical plan data are accumulated during the past two decades, a new set of methods commonly termed knowledge-based planning (KBP) have been developed that aim to improve the quality and efficiency of IMRT planning by learning from the database of past clinical plans. Read More

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http://dx.doi.org/10.1002/mp.13526DOI Listing

Influences of Operator Head Posture and Protective Eyewear on Eye Lens Doses in Interventional Radiology: a Monte Carlo Study.

Med Phys 2019 Apr 7. Epub 2019 Apr 7.

Radiology& Medical Physics, Memorial Sloan Kettering Cancer Center, New York, 10065.

Purpose: To quantify the effects of operator head posture and different types of protective eyewear on the eye lens dose to operators in interventional radiology (IR).

Methods: A deformable computational human phantom, RPI Adult Male, consisting of a high-resolution eye model, was used to simulate a radiologist who is performing an interventional radiology procedure. The radiologist phantom was deformed to a set of different head postures. Read More

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https://onlinelibrary.wiley.com/doi/abs/10.1002/mp.13528
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http://dx.doi.org/10.1002/mp.13528DOI Listing
April 2019
3 Reads
2.635 Impact Factor

Investigation of TLD and EBT3 performance under the presence of 1.5T, 0.35T and 0T magnetic field strengths in MR/CT visible materials.

Med Phys 2019 Apr 4. Epub 2019 Apr 4.

Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, 77030.

Purpose: The aim of this study was to investigate thermoluminescent dosimeters (TLD) and radiochromic EBT3 film inside MR/CT visible geometric head and thorax phantoms in the presence of: 0T, 0.35T and 1.5T magnetic fields. Read More

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http://dx.doi.org/10.1002/mp.13527DOI Listing

A 3D printed modular phantom for quality assurance of image-guided small animal irradiators: Design, imaging experiments, and Monte Carlo simulations.

Med Phys 2019 Apr 4. Epub 2019 Apr 4.

Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada.

Purpose: The goal of this work was to develop and test a cylindrical tissue-equivalent quality assurance (QA) phantom for micro computed tomography (microCT) image-guided small animal irradiators that overcomes deficiencies of existing phantoms due to its mouse-like dimensions and composition.

Methods: The 8.6-cm-long and 2. Read More

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http://dx.doi.org/10.1002/mp.13525DOI Listing

In the future, disruptive innovation in radiation oncology technology will be initiated mostly by entrepreneurs.

Med Phys 2019 Apr 3. Epub 2019 Apr 3.

Hong Kong Polytechnic University, Health Technology and Informatics, Lee Shau Kee Building, Kowloon, 518000, Hong Kong.

Radiation oncology is a technology-driven treatment modality in the management of cancer, and has evolved substantially over the past few decades. Particularly in recent years, there has been a boom in the introduction of innovative, and sometimes even almost disruptive, technologies in radiation oncology, such as Cyberknife, Tomotherapy, Proton therapy, and MRI-linac. Entrepreneurs have played an important role in turning ideas into products in many of these technological innovations. Read More

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http://dx.doi.org/10.1002/mp.13524DOI Listing
April 2019
2.635 Impact Factor

Impacts of respiratory phase shifts on motion-tracking accuracy of the CyberKnife Synchrony Respiratory Tracking System.

Med Phys 2019 Apr 3. Epub 2019 Apr 3.

Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan.

Purpose: The Synchrony Respiratory Tracking System (SRTS) component of the CyberKnife Robotic Radiosurgery System (Accuray, Inc., Sunnyvale CA) enables real-time tracking of moving targets by modeling the correlation between the targets and external surrogate light-emitting diode (LED) markers placed on the patient's chest. Previous studies reported some cases with respiratory phase shifts between lung tumor and chest wall motions. Read More

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http://dx.doi.org/10.1002/mp.13523DOI Listing

Technical Note: Imaging dose resulting from optimized procedures with Limited-angle Intra-fractional Verification (LIVE) system during SBRT lung treatment.

Med Phys 2019 Apr 2. Epub 2019 Apr 2.

Department of Radiation Oncology, Duke University, Durham, NC.

Purpose: The Limited-angle Intra-fractional Verification (LIVE) system was developed to track tumor movement during SBRT. However, the 4D MV/kV imaging procedure results in additional radiation dose to patients. This study is to quantify imaging radiation dose from optimized MV/kV image acquisition in the LIVE system and to determine if it exceeds the AAPM TG-180 report image dose threshold. Read More

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http://dx.doi.org/10.1002/mp.13511DOI Listing
April 2019
1 Read
2.635 Impact Factor

Probabilistic Framework for Robust Seed-Based Correlation Analysis.

Med Phys 2019 Apr 1. Epub 2019 Apr 1.

Vanderbilt University, Department of Electrical Engineering and Computer Science, 400 24th Avenue South, Featheringill Hall, Room 254, Nashville, TN, USA, 37235.

Purpose: One popular method of assessing brain functional connectivity (FC) is through seed-based correlation (SCA) analysis. One drawback of this method is when the seed location is varied slightly, the FC can vary dramatically. We propose a method superior to SCA, robust to variations in seed location, which confers a probabilistic interpretation. Read More

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http://dx.doi.org/10.1002/mp.13522DOI Listing

Low Dose PET Emulation from Decimated High Statistics: A Clinical Validation Study.

Med Phys 2019 Mar 31. Epub 2019 Mar 31.

Siemens Medical Solutions USA, Inc. Knoxville, TN, USA.

Purpose: The fundamental nature of PET, as an event detection system, provides some flexibility for data handling, including retrospective data manipulation. The reorganization of acquisition data allows the emulation of new scans arising from identical radiotracer spatial distributions, but with different statistical compositions, and is especially useful for evaluating the stability and reproducibility of reconstruction algorithms or when investigating extremely low count conditions. This approach is ubiquitous in the research literature but has only been validated, from the point of view of the noise properties, with numerical simulations and phantom data. Read More

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http://dx.doi.org/10.1002/mp.13517DOI Listing
March 2019
2 Reads

Temporal stability assessment in shear wave elasticity images validated by deep learning neural network for chronic liver disease fibrosis stage assessment.

Med Phys 2019 Mar 31. Epub 2019 Mar 31.

Department of Medical Physics, University of Patras, Rion, GR, 26504, Greece.

Purpose: To automatically detect and isolate areas of low and high stiffness temporal stability in shear wave elastography (SWE) image sequences and define their impact in chronic liver disease (CLD) diagnosis improvement by means of clinical examination study and deep learning algorithm employing convolutional neural networks (CNNs).

Materials And Methods: Two hundred SWE image sequences from 88 healthy individuals (F0 fibrosis stage) and 112 CLD patients (46 with mild fibrosis (F1), 16 with significant fibrosis (F2), 22 with severe fibrosis (F3), and 28 with cirrhosis (F4)) were analyzed to detect temporal stiffness stability between frames. An inverse Red, Green, Blue (RGB) colormap-to-stiffness process was performed for each image sequence, followed by a wavelet transform and fuzzy c-means clustering algorithm. Read More

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http://dx.doi.org/10.1002/mp.13521DOI Listing
March 2019
1 Read
2.635 Impact Factor

A deep learning framework for automatic detection of arbitrarily shaped fiducial markers in intrafraction fluoroscopic images.

Med Phys 2019 Mar 31. Epub 2019 Mar 31.

Faculty of Medicine and Health, ACRF Image X Institute, The University of Sydney, Sydney, NSW, Australia.

Purpose: Real-time image-guided adaptive radiation therapy (IGART) requires accurate marker segmentation to resolve three-dimensional (3D) motion based on two-dimensional (2D) fluoroscopic images. Most common marker segmentation methods require prior knowledge of marker properties to construct a template. If marker properties are not known, an additional learning period is required to build the template which exposes the patient to an additional imaging dose. Read More

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http://dx.doi.org/10.1002/mp.13519DOI Listing
March 2019
1 Read

Dense networks with relative location awareness for thorax disease identification.

Med Phys 2019 Mar 30. Epub 2019 Mar 30.

CAS Key Laboratory of Technology in Geo-spatial Information Processing and Application Systems, University of Science and Technology of China, Hefei, 230027, China.

Purpose: Chest X-ray is one of the most common examinations for diagnosing heart and lung diseases. Due to the existing of a large number of clinical cases, many automated diagnosis algorithms based on chest X-ray images have been proposed. To our knowledge, almost none of the previous auto-diagnosis algorithms consider the effect of relative location information on disease incidence. Read More

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http://dx.doi.org/10.1002/mp.13516DOI Listing
March 2019
2.635 Impact Factor

Characterization of a Bayesian network-based radiotherapy plan verification model.

Med Phys 2019 Mar 29. Epub 2019 Mar 29.

Department of Radiation Oncology, University of Washington Medical Center, Seattle, WA, 98195-6043, USA.

Purpose: The current process for radiotherapy treatment plan quality assurance relies on human inspection of treatment plans, which is time-consuming, error prone and oft reliant on inconsistently applied professional judgments. A previous proof-of-principle paper describes the use of a Bayesian network (BN) to aid in this process. This work studied how such a BN could be expanded and trained to better represent clinical practice. Read More

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http://dx.doi.org/10.1002/mp.13515DOI Listing

Dosimetry and characterization of a 25-MeV proton beam line for preclinical radiobiology research.

Med Phys 2019 Mar 29. Epub 2019 Mar 29.

Université de Strasbourg, CNRS, IPHC, UMR 7178, F-67000, Strasbourg, France.

Purpose: With the increase in proton therapy centers, there is a growing need to make progress in preclinical proton radiation biology to give accessible data to medical physicists and practicing radiation oncologists.

Methods: A cyclotron usually producing radioisotopes with a proton beam at an energy of about 25 MeV after acceleration, was used for radiobiology studies. Depleted silicon surface barrier detectors were used for the beam energy measurement. Read More

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http://dx.doi.org/10.1002/mp.13512DOI Listing

Radiofrequency transmit calibration: A multi-center evaluation of vendor-provided radiofrequency transmit mapping methods.

Med Phys 2019 Mar 29. Epub 2019 Mar 29.

Ming Hsieh Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA.

Purpose: To determine the accuracy and test-retest repeatability of fast radiofrequency (RF) transmit measurement approaches used in Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI). Spatial variation in the transmitted RF field introduces bias and increased variance in quantitative DCE-MRI metrics including tracer kinetic parameter maps. If unaccounted for, these errors can dominate all other sources of bias and variance. Read More

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http://dx.doi.org/10.1002/mp.13518DOI Listing

Impact of SBRT fractionation in hypoxia dose painting - Accounting for heterogeneous and dynamic tumor oxygenation.

Med Phys 2019 Mar 29. Epub 2019 Mar 29.

Medical Radiation Physics, Department of Physics, Stockholm University, Stockholm, S-17176, Sweden.

Purpose: Tumor hypoxia, often found in nonsmall cell lung cancer (NSCLC), implies an increased resistance to radiotherapy. Pretreatment assessment of tumor oxygenation is, therefore, warranted in these patients, as functional imaging of hypoxia could be used as a basis for dose painting. This study aimed at investigating the feasibility of using a method for calculating the dose required in hypoxic subvolumes segmented on F-HX4 positron emission tomography (PET) imaging of NSCLC. Read More

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http://dx.doi.org/10.1002/mp.13514DOI Listing
March 2019
2 Reads

Interpolated CT for Attenuation Correction on Respiratory Gating Cardiac SPECT/CT - a Simulation Study.

Med Phys 2019 Mar 29. Epub 2019 Mar 29.

Biomedical Imaging Laboratory (BIG), Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau SAR, China.

Purpose: Respiratory gated 4D SPECT with phase-matched CT reduces respiratory blurring and attenuation correction (AC) artifacts in cardiac SPECT. This study aims to develop and investigate the effectiveness of an interpolated CT (ICT) method for improved cardiac SPECT AC using simulations.

Methods: We used the 4D XCAT phantom to simulate a population of 10 patients, varied in gender, anatomy, Tc-sestamibi distribution, respiratory patterns and disease states. Read More

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http://dx.doi.org/10.1002/mp.13513DOI Listing

A novel deformable lung phantom with programably variable external and internal correlation.

Med Phys 2019 Mar 28. Epub 2019 Mar 28.

Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.

Purpose: Lung motion phantoms used to validate radiotherapy motion management strategies have fairly simplistic designs that do not adequately capture complex phenomena observed in human respiration such as external and internal deformation, variable hysteresis and variable correlation between different parts of the thoracic anatomy. These limitations make reliable evaluation of sophisticated motion management techniques quite challenging. In this work, we present the design and implementation of a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers. Read More

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http://dx.doi.org/10.1002/mp.13507DOI Listing
March 2019
1 Read

Anti-phase microwave illumination-based thermoacoustic tomography of in vivo human finger joints.

Med Phys 2019 Mar 28. Epub 2019 Mar 28.

School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, China.

Purpose: Thermoacoustic tomography (TAT) has been studied to image joints. While several joint tissues could be thermoacoustically imaged, tendons and bone could not be recovered completely or clearly. The purpose of this study was to overcome this limitation. Read More

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http://dx.doi.org/10.1002/mp.13506DOI Listing

Technical Note: Identification of an optimal electromagnetic sensor for in vivo electromagnetic-tracked scintillation dosimeter for HDR brachytherapy.

Med Phys 2019 Mar 27. Epub 2019 Mar 27.

Département de radio-oncologie et Centre de recherche du CHU de Québec, CHU de Québec, Québec, Canada.

Purpose: Brachytherapy is a treatment modality which delivers large doses of radiation in a reduced number of visits. Since a small number of large dose-per-fraction is administered in high dose rate brachytherapy, ensuring the right dose is delivered is highly critical. In this work, a scintillation detector is coupled to an electromagnetic (EM) sensor (NDI, Waterloo, ON, Canada) having submillimeter positional accuracy for real-time tracking of the dosimeter position. Read More

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http://dx.doi.org/10.1002/mp.13508DOI Listing

Validation of three-dimensional echocardiographic principal strain analysis for assessing left ventricular contractility: An animal study.

Med Phys 2019 Mar 26. Epub 2019 Mar 26.

Division of Cardiology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.

Purpose: The three-dimensional (3D) principal strain represents the major direction and magnitude of the deformation by its definition and can be measured using 3D echocardiography. We aimed to validate 3D echocardiographic left ventricular (LV) global principal strains as an assessment of LV contractility by comparison with gold standard invasive measurements.

Methods: In 14 beagles, the LV pressure-volume loop was recorded to invasively measure the end-systolic pressure-volume relationship (ESPVR) and dP/dt as reference indicators representing LV contractility. Read More

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http://dx.doi.org/10.1002/mp.13509DOI Listing
March 2019
3 Reads

Attention-aware Fully Convolutional Neural Network with Convolutional Long Short-Term Memory Network for Ultrasound-Based Motion Tracking.

Med Phys 2019 Mar 26. Epub 2019 Mar 26.

Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, Jinan, Shandong, 250358, China.

Purpose: One of the promising options for motion management in radiation therapy (RT) is the use of Linac-compatible robotic-arm-mounted ultrasound imaging system due to its high soft tissue contrast, real-time capability, absence of ionizing radiation and low cost. The purpose of this work is to develop a novel deep learning-based real-time motion tracking strategy for ultrasound image-guided RT.

Methods: The proposed tracker combined the attention-aware Fully Convolutional Neural Network (FCNN) and the Convolutional Long Short-Term Memory network (CLSTM) that is end-to-end trainable. Read More

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http://dx.doi.org/10.1002/mp.13510DOI Listing

Characterization of the plastic scintillation detector Exradin W2 for small field dosimetry.

Med Phys 2019 Mar 21. Epub 2019 Mar 21.

Department of Radiation Oncology, New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center, New York, NY, 10016, USA.

Purpose: Small field dosimetry has been an active area of research for over a decade. It is now known that large dosimetric errors can be introduced if proper detectors or correction factors are not used. The International Atomic Energy Agency (IAEA) through the technical report series No. Read More

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http://dx.doi.org/10.1002/mp.13501DOI Listing
March 2019
11 Reads

Technical Note: Density correction to improve CT number mapping in thoracic deformable image registration.

Med Phys 2019 Mar 21. Epub 2019 Mar 21.

Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.

Purpose: To improve the accuracy of computed tomography (CT) number mapping inside the lung in deformable image registration with large differences in lung volume for applications in vertical CT imaging and adaptive radiotherapy.

Methods: The deep inspiration breath hold (DIBH) CT image and the end of exhalation (EE) phase image in four-dimensional CT of 14 thoracic cancer patients were used in this study. Lung volumes were manually delineated. Read More

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http://dx.doi.org/10.1002/mp.13502DOI Listing

Estimating Fetal Dose from Tube Current Modulated (TCM) and Fixed Tube Current (FTC) Abdominal/Pelvis CT Examinations.

Med Phys 2019 Mar 20. Epub 2019 Mar 20.

Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, 90024.

Purpose: The purpose of this work was to estimate scanner independent CTDI -to-fetal-dose coefficients for tube current modulated (TCM) and fixed tube current (FTC) CT examinations of pregnant patients of various gestational ages undergoing abdominal/pelvic CT examinations.

Methods: For 24 pregnant patients of gestational age from less than 5 to 36 weeks who underwent clinically-indicated CT examinations, voxelized models of maternal and fetal (or embryo) anatomy were created from abdominal/pelvic image data. Absolute fetal dose (D ) was estimated using Monte Carlo (MC) simulations of helical scans covering the abdomen and pelvis for TCM and FTC scans. Read More

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https://onlinelibrary.wiley.com/doi/abs/10.1002/mp.13499
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http://dx.doi.org/10.1002/mp.13499DOI Listing
March 2019
3 Reads

Quantitative Assessment of Breast Density Using Transmission Ultrasound Tomography.

Med Phys 2019 Mar 20. Epub 2019 Mar 20.

Chief Technology Officer, QT Ultrasound, LLC, 3 Hamilton Landing, Suite 160, Novato, CA, 94949.

Purpose: Breast density is important in the evaluation of breast cancer risk. At present, breast density is evaluated using two-dimensional projections from mammography with or without tomosynthesis using either (1) subjective assessment, or (2) a computer-aided approach. The purpose of this work is two-fold: (1) to establish an algorithm for quantitative assessment of breast density using quantitative three-dimensional transmission ultrasound imaging; and (2) to determine how these quantitative assessments compare with both subjective and objective mammographic assessments of breast density. Read More

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https://onlinelibrary.wiley.com/doi/abs/10.1002/mp.13503
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http://dx.doi.org/10.1002/mp.13503DOI Listing
March 2019
3 Reads

Optimization of a multipoint plastic scintillator dosimeter for high dose rate brachytherapy.

Med Phys 2019 Mar 20. Epub 2019 Mar 20.

Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec City, QC, Canada.

Purpose: This study is devoted to optimizing and characterizing the response of a multipoint plastic scintillator detector (mPSD) for application to in vivo dosimetry in high dose rate (HDR) brachytherapy.

Methods: An exhaustive analysis was carried out in order to obtain an optimized mPSD design that maximizes the scintillation light collection produced by the interaction of ionizing photons. More than 20 prototypes of mPSD were built and tested in order to determine the appropriate order of scintillators relative to the photodetector (distal, center, or proximal) as well as their length as a function of the scintillation light emitted. Read More

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http://dx.doi.org/10.1002/mp.13498DOI Listing
March 2019
2 Reads

Combining handcrafted features with latent variables in machine learning for prediction of radiation-induced lung damage.

Med Phys 2019 Mar 19. Epub 2019 Mar 19.

Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.

Purpose: There has been burgeoning interest in applying machine learning methods for predicting radiotherapy outcomes. However, the imbalanced ratio of a large number of variables to a limited sample size in radiation oncology constitutes a major challenge. Therefore, dimensionality reduction methods can be a key to success. Read More

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http://dx.doi.org/10.1002/mp.13497DOI Listing
March 2019
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A deep learning- and partial least square regression-based model observer for a low-contrast lesion detection task in CT.

Med Phys 2019 Mar 19. Epub 2019 Mar 19.

Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA.

Purpose: This work aims to develop a new framework of image quality assessment using deep learning-based model observer (DL-MO) and to validate it in a low-contrast lesion detection task that involves CT images with patient anatomical background.

Methods: The DL-MO was developed using the transfer learning strategy to incorporate a pretrained deep convolutional neural network (CNN), a partial least square regression discriminant analysis (PLS-DA) model and an internal noise component. The CNN was previously trained to achieve the state-of-the-art classification accuracy over a natural image database. Read More

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http://dx.doi.org/10.1002/mp.13500DOI Listing
March 2019
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Accuracy of registration algorithms in subtraction CT of the lungs: A digital phantom study.

Med Phys 2019 Mar 19. Epub 2019 Mar 19.

Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein 10, 6525 GA, Nijmegen, The Netherlands.

Purpose: The purpose of this study was to assess, using an anthropomorphic digital phantom, the accuracy of algorithms in registering precontrast and contrast-enhanced computed tomography (CT) chest images for generation of iodine maps of the pulmonary parenchyma via temporal subtraction.

Materials And Methods: The XCAT phantom, with enhanced airway and pulmonary vessel structures, was used to simulate precontrast and contrast-enhanced chest images at various inspiration levels and added CT simulation for realistic system noise. Differences in diaphragm position were varied between 0 and 20 mm, with the maximum chosen to exceed the 95th percentile found in a dataset of 100 clinical subtraction CTs. Read More

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http://dx.doi.org/10.1002/mp.13496DOI Listing

Similarity clustering based atlas selection for pelvic CT image segmentation.

Med Phys 2019 Mar 18. Epub 2019 Mar 18.

Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia.

Purpose: To demonstrate selection of a small representative subset of images from a pool of images comprising a potential atlas pelvic CT set to be used for autosegmentation of a separate target image set. The aim is to balance the need for the atlas set to represent anatomical diversity with the need to minimise resources required to create a high quality atlas set (such as multi-observer delineation), whilst retaining access to additional information available for the potential atlas image set.

Methods: Pre-processing was performed for image standardisation, followed by image registration. Read More

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http://dx.doi.org/10.1002/mp.13494DOI Listing

A convolutional neural network algorithm for automatic segmentation of head and neck organs at risk using deep lifelong learning.

Med Phys 2019 Mar 18. Epub 2019 Mar 18.

Department of Radiation Oncology, University of California, San Francisco, CA, 94115, USA.

Purpose: This study suggests a lifelong learning-based convolutional neural network (LL-CNN) algorithm as a superior alternative to single-task learning approaches for automatic segmentation of head and neck (OARs) organs at risk.

Methods And Materials: Lifelong learning-based convolutional neural network was trained on twelve head and neck OARs simultaneously using a multitask learning framework. Once the weights of the shared network were established, the final multitask convolutional layer was replaced by a single-task convolutional layer. Read More

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http://dx.doi.org/10.1002/mp.13495DOI Listing
March 2019
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2.635 Impact Factor

Systematic analysis of the impact of imaging noise on dual-energy CT-based proton stopping power ratio estimation.

Med Phys 2019 Mar 18. Epub 2019 Mar 18.

Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.

Purpose: Dual-energy CT (DECT) has been shown to have a great potential in reducing the uncertainty in proton stopping power ratio (SPR) estimation, when compared to current standard method - the stoichiometric method based on single-energy CT (SECT). However, a few recent studies indicated that imaging noise may have a substantial impact on the performance of the DECT-based approach, especially at a high noise level. The goal of this study is to quantify the uncertainty in SPR and range estimation caused by noise in the DECT-based approach under various conditions. Read More

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http://dx.doi.org/10.1002/mp.13493DOI Listing

Image domain dual material decomposition for dual-energy CT using butterfly network.

Med Phys 2019 Mar 18. Epub 2019 Mar 18.

National Digital Switching System Engineering and Technological Research Center, Zhengzhou, Henan, 450002, China.

Purpose: Dual-energy CT (DECT) has been increasingly used in imaging applications because of its capability for material differentiation. However, material decomposition suffers from magnified noise from two CT images of independent scans, leading to severe degradation of image quality. Existing algorithms exhibit suboptimal decomposition performance because they fail to fully depict the mapping relationship between DECT images and basis materials under noisy conditions. Read More

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http://dx.doi.org/10.1002/mp.13489DOI Listing
March 2019
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2.635 Impact Factor

A convex windowless extrapolation chamber to measure surface dose rate from Ru/ Rh episcleral plaques.

Med Phys 2019 Mar 15. Epub 2019 Mar 15.

Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53705, USA.

Purpose: A convex windowless extrapolation chamber was developed as a primary measurement device to determine surface dose rate from curved Ru/ Rh episcleral plaques.

Methods: A convex extrapolation chamber without an entrance window was constructed for this work, and surface dose rate measurements were performed with two curved CCB-type Ru/ Rh plaques (S/N 2545 and 2596) manufactured by Eckert & Ziegler BEBIG. FARO Gage measurements were performed to verify the radius of curvature for the convex electrode and the concave plaque surface. Read More

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http://dx.doi.org/10.1002/mp.13488DOI Listing

A deep learning method for prediction of three-dimensional dose distribution of helical tomotherapy.

Med Phys 2019 Mar 14. Epub 2019 Mar 14.

National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuannanli, Chaoyang District, Beijing, 100021, China.

Purpose: To develop a deep learning method for prediction of three-dimensional (3D) voxel-by-voxel dose distributions of helical tomotherapy (HT).

Methods: Using previously treated HT plans as training data, a deep learning model named U-ResNet-D was trained to predict a 3D dose distribution. First, the contoured structures and dose volumes were converted from plan database to 3D matrix with a program based on a developed visualization toolkit (VTK), then transferred to U-ResNet-D for correlating anatomical features and dose distributions at voxel-level. Read More

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http://dx.doi.org/10.1002/mp.13490DOI Listing
March 2019
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Evaluation of electromagnetic and nuclear scattering models in GATE/Geant4 for proton therapy.

Med Phys 2019 Mar 14. Epub 2019 Mar 14.

MedAustron Ion Therapy Centre/EBG MedAustron, Marie-Curie-Straße 5, 2700, Wiener Neustadt, Austria.

Purpose: The dose core of a proton pencil beam (PB) is enveloped by a low dose area reaching several centimeters off the central axis and containing a considerable amount of the dose. Adequate modeling of the different components of the PB profile is, therefore, required for accurate dose calculation. In this study, we experimentally validated one electromagnetic and two nuclear scattering models in GATE/Geant4 for dose calculation of proton beams in the therapeutic energy window (62-252 MeV) with and without range shifter (RaShi). Read More

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http://dx.doi.org/10.1002/mp.13472DOI Listing
March 2019
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