13,606 results match your criteria Physics in medicine and biology[Journal]


Fiducial marker based intra-fraction motion assessment on cine-MR for MR-Linac treatment of prostate cancer.

Phys Med Biol 2019 Feb 22. Epub 2019 Feb 22.

Department of Radiotherapy, Universitair Medisch Centrum Utrecht, Utrecht, NETHERLANDS.

Purpose We have developed a method to determine intrafraction motion of the prostate through automatic fiducial marker (FM) tracking on 3D cine-magnetic resonance (MR) images with high spatial and temporal resolution. Methods Twenty-nine patients undergoing prostate stereotactic body radiotherapy (SBRT), with four implanted cylindrical gold FMs, had cine-MR imaging sessions after each of five weekly fractions. Each cine-MR examination consisted of 55 sequentially obtained 3D datasets ('dynamics'), acquired over a 11 second period, covering a total of 10 minutes. Read More

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http://dx.doi.org/10.1088/1361-6560/ab09a6DOI Listing
February 2019

Oblique raster scanning: an ion dose delivery procedure with variable energy layers.

Authors:
Ugo Amaldi

Phys Med Biol 2019 Feb 21. Epub 2019 Feb 21.

EP Division, Fondazione TERA, CERN, CH-1211 Geneva, Geneva, 1211, SWITZERLAND.

In ion Therapy Accelerator Complexes the dose is delivered "actively" by subdividing the target in Equal Energy Layers, which are scanned by a beam spot visiting in sequence the planned spots, previously defined by the Treatment Planning System. Synchrotrons-based complexes have three problems: (i) the switching from the energy needed to scan one Equal Energy Layer to the next takes time, an effect that is more relevant for the very short treatment times now often required; (ii) the unavoidable "ripples" of the quadrupoles and bending magnets currents produce large erratic time variations of the extracted current complicating the dose delivery; (iii) in case of superconducting synchrotrons, it is difficult to rapidly change the magnetic field because of the power dumped in the cold masses. These problems are mitigated in the proposed Qblique Raster Scanning procedure, in which the magnet currents of the beamlines vary in synchrony and a beam spot of continuously varying energy moves at a constant velocity in the beam direction scanning layers that are not perpendicular to it. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0920DOI Listing
February 2019

Integrating DVH criteria into a column generation algorithm for VMAT treatment planning.

Phys Med Biol 2019 Feb 21. Epub 2019 Feb 21.

Mathematics and Industrial Engineering, Ecole Polytechnique de Montreal, Montreal, Quebec, CANADA.

Volumetric-modulated arc therapy (VMAT) treatment planning is an efficient treatment technique with a high degree of flexibility in terms of dose rate, gantry speed, and aperture shapes during rotation around the patient. However, the dynamic nature of VMAT results in a large-scale nonconvex optimization problem. Determining the priority of the tissues and voxels to obtain clinically acceptable treatment plans poses additional challenges for VMAT optimization. Read More

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http://dx.doi.org/10.1088/1361-6560/ab091cDOI Listing
February 2019

Computational modelling of resistance and associated treatment response heterogeneity in metastatic cancers.

Phys Med Biol 2019 Feb 21. Epub 2019 Feb 21.

7033 Wisconsin Institute for Medical Research Department of Medical Physics, University of Wisconsin at Madison, Madison, Wisconsin, UNITED STATES.

Metastatic cancer patients invariably develop treatment resistance. Different levels of resistance lead to observed heterogeneity in treatment response. The main goal was to evaluate treatment response heterogeneity with computation model simulating dynamics of drug-sensitive and drug-resistant cells. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0924DOI Listing
February 2019

Posture-dependent dose coefficients of mesh-type ICRP reference computational phantoms for photon external exposures.

Phys Med Biol 2019 Feb 21. Epub 2019 Feb 21.

Department of Nuclear Engineering, Hanyang University, Seoul, KOREA, REPUBLIC OF.

Recently, the International Commission on Radiological Protection (ICRP) developed new mesh-type reference computational phantoms (MRCPs) that provide high deformability compared with the current voxel-type reference computational phantoms of ICRP Publication 110. Taking advantage of this deformability, in the present study, the MRCPs were deformed to five non-standing postures (i.e. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0917DOI Listing
February 2019

Combining many-objective radiomics and 3-dimensional convolutional neural network through evidential reasoning to predict lymph node metastasis in head and neck cancer.

Phys Med Biol 2019 Feb 19. Epub 2019 Feb 19.

Department of Radiation Oncology, University of Texas Southwestern Medical Centre, 5801 Forest Park Road, Dallas, TX 75390-9183, Dallas, Texas, UNITED STATES.

Lymph node metastasis (LNM) is a significant prognostic factor in patients with head and neck cancer, and the ability to predict it accurately is essential to optimizing treatment. Positron emission tomography (PET) and computed tomography (CT) imaging are routinely used to identify LNM. Although large or highly active lymph nodes (LNs) have a high probability of being positive, identifying small or less reactive LNs is challenging. Read More

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http://dx.doi.org/10.1088/1361-6560/ab083aDOI Listing
February 2019

A cone-shaped gradient coil design for high-resolution MRI head imaging.

Phys Med Biol 2019 Feb 19. Epub 2019 Feb 19.

School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Queensland, AUSTRALIA.

Insertable head gradient coils offer significant advantages such as high gradient strength and fast gradient switching speed owing to close distance to the target region of interest than whole-body cylindrical coils. To produce superior gradient performance, the local head coil is typically designed with an asymmetric configuration to accommodate both the shoulders and head of a patient, leading to tough dimensional constraints and practical limits to the coil implementation. In this paper, we proposed a new cone-shaped model to improve the performance of the asymmetric head coils and also to mitigate patient claustrophobia. Read More

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http://dx.doi.org/10.1088/1361-6560/ab084aDOI Listing
February 2019

McSART: an iterative model-based, motion-compensated SART algorithm for CBCT reconstruction.

Phys Med Biol 2019 Feb 18. Epub 2019 Feb 18.

Radiation Oncology, University of California Los Angeles David Geffen School of Medicine, 200 Medical Plaza, Suite B265, Los Angeles, California, 90095, UNITED STATES.

4D cone beam computed tomography (CBCT) images of the thorax and abdomen can have reduced quality due to the limited number of projections per respiratory bin used in gated image reconstruction. In this work, we present a new algorithm to reconstruct high quality CBCT images by simultaneously reconstructing images and generating an associated respiratory motion model. This is done by updating model parameters to compensate for motion during the iterative image reconstruction process. Read More

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http://dx.doi.org/10.1088/1361-6560/ab07d6DOI Listing
February 2019

A mixed-integer linear programming optimization model framework for capturing expert planning style in low dose rate prostate brachytherapy.

Phys Med Biol 2019 Feb 15. Epub 2019 Feb 15.

Mechanical Engineering, University of Alberta, Edmonton, Alberta, CANADA.

Low dose rate (LDR) brachytherapy is a minimally invasive form of radiation therapy, used to treat prostate cancer, and it involves permanent implantation of radioactive sources (seeds) inside of the prostate gland. Treatment planning in brachytherapy involves a decision making process for the placement of the sources in order to deliver an effective dose of radiation to cancerous tissue in the prostate while sparing the surrounding healthy tissue. Such a decision making process can be modeled as a mixed-integer linear programming (MILP) problem. Read More

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http://dx.doi.org/10.1088/1361-6560/ab075cDOI Listing
February 2019
2 Reads

Real-time respiratory triggered four dimensional cone-beam CT halves imaging dose compared to conventional 4D CBCT.

Phys Med Biol 2019 Feb 12. Epub 2019 Feb 12.

ACRF Image X Institute, Biomedical Building (C81), 1 Central Ave, Australian Technology Park, University of Sydney, Everleigh, New South Wales, AUSTRALIA.

Four dimensional cone-beam computed tomography (4D CBCT) improves patient positioning and the accuracy of radiation therapy for patients with mobile tumours. Generally, 4D CBCT requires many hundreds of x-ray projections to measure target trajectories and the imaging frequency is not adapted to the patient's respiratory signal resulting in over-sampling. In contrast, respiratory triggered 4D CBCT (RT 4D CBCT) is an acquisition technique that has been experimentally implemented and has shown to reduce the number of x-ray projections and thus 4D CBCT dose with minimal impact on image quality. Read More

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http://dx.doi.org/10.1088/1361-6560/ab065dDOI Listing
February 2019
1 Read

Investigation of the refractive index decrement of 3D printing materials for manufacturing breast phantoms for phase contrast imaging.

Phys Med Biol 2019 Feb 12. Epub 2019 Feb 12.

Dipartimento di Fisica "E. Pancini", Universita degli Studi di Napoli Federico II, Napoli, Campania, ITALY.

3D breast modelling for 2D and 3D breast X-ray imaging would benefit from the availability of digital and physical phantoms that reproduce accurately the complexity of the breast anatomy. While a number of groups have produced digital phantoms with increasing level of complexity, physical phantoms reproducing that software approach have been scarcely developed. One possibility is offered by 3D printing technology. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0670DOI Listing
February 2019
1 Read

2019: An Update from the Editor-in-Chief.

Authors:
Simon R Cherry

Phys Med Biol 2019 Feb 12. Epub 2019 Feb 12.

Department of Biomedical Engineering, University of California - Davis, One Shields Avenue, Davis, California, 95616, UNITED STATES.

Not applicable. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0671DOI Listing
February 2019

Joint correction of attenuation and scatter in image space using deep convolutional neural networks for dedicated brain 18F-FDG PET.

Phys Med Biol 2019 Feb 11. Epub 2019 Feb 11.

Department of Radiology and Biomedical Imaging, University of California San Francisco, Physics Research Laboratory, Suite 350, 185 Berry Street, San Francisco, California, UNITED STATES.

Dedicated brain positron emission tomography (PET) devices can provide higher-resolution images with much lower dose, compared to conventional whole-body PET systems, which is important to support PET neuroimaging particularly useful for the diagnosis of neurodegenerative diseases. However, when a dedicated brain PET scanner does not come with a combined CT or transmission source, there is no direct solution for accurate attenuation and scatter correction, both of which are critical for quantitative PET. To address this problem, we propose joint attenuation and scatter correction (ASC) in image space for non-corrected PET (PET<sub>NC</sub>) using deep convolutional neural networks (DCNN). Read More

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http://dx.doi.org/10.1088/1361-6560/ab0606DOI Listing
February 2019

Semi-automated IGRT QA using a cone-shaped scintillator screen detector for proton pencil beam scanning treatments.

Phys Med Biol 2019 Feb 8. Epub 2019 Feb 8.

Radiation Oncology, Massachusetts General Hospital, 55 Fruit St., Boston, Massachusetts, 02114, UNITED STATES.

To promote accurate image-guided radiotherapy (IGRT) for a proton pencil beam scanning (PBS) system, a new QA procedure employing a cone-shaped scintillator detector has been developed for multiple QA tasks in a semi-automatic manner. The cone-shaped scintillator detector (XRV-124, Logos Systems, CA) is sensitive to both x-ray and proton beams. It records scintillation on the cone surface as a 2D image, from which the geometry of the radiation field that enters and exits the cone can be extracted. Read More

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http://dx.doi.org/10.1088/1361-6560/ab056dDOI Listing
February 2019

Evaluation of materials used for vascular anastomoses using shear wave elastography.

Phys Med Biol 2019 Feb 8. Epub 2019 Feb 8.

Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First St SW, Rochester, Minnesota, 55905, UNITED STATES.

Cardiovascular disease is the leading cause of mortality in the United States. Peripheral artery disease (PAD) affects a substantial portion of the elderly population (> 70 years). PAD can be symptomatic or asymptomatic, and treatment is directed towards improving functional vessel patency and limb salvage. Read More

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http://dx.doi.org/10.1088/1361-6560/ab055cDOI Listing
February 2019

Relationship between power density and surface temperature elevation for human skin exposure to electromagnetic waves with oblique incidence angle from 6 GHz to 1 THz.

Phys Med Biol 2019 Feb 8. Epub 2019 Feb 8.

Faculty of Science and Engineering Graduate School of Science and Engineering, Chuo University, Hachioji, Tokyo, JAPAN.

This study presents an investigation of human skin exposure to obliquely incident electromagnetic waves at frequencies from 6 GHz to 1 THz. We aim to clarify the relationship between the power density and the skin surface temperature elevation under various exposure conditions. A Monte Carlo simulation was conducted to assess the transmittance and surface temperature elevation considering the variation of skin tissue thickness. Read More

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http://dx.doi.org/10.1088/1361-6560/ab057aDOI Listing
February 2019

Impact of high dose volumetric CT on PTV margin reduction in VMAT prostate radiotherapy.

Phys Med Biol 2019 Feb 7. Epub 2019 Feb 7.

Princess Margaret/Techna, University Health Network, 190 Elizabeth St., Rm 1S-411, Toronto, Ontario, M5G 2C4, CANADA.

The aim of the study is to determine PTV margin for inter-observer variability in the volumetric modulated arc therapy (VMAT) prostate radiotherapy with high-dose volumetric CT (HDVCT) and conventional helical CT (CCT) for planning. Secondly to investigate the impact of geometric (PTV expansion) and dosimetric (conformity) imperfection of planning process on the PTV margin analysis. Prostate gland of ten patients were scanned with CCT and HDVCT techniques consecutively on a 320 slice volumetric CT scanner with wide field detector of 16 cm. Read More

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http://dx.doi.org/10.1088/1361-6560/ab050fDOI Listing
February 2019
1 Read

Exploration of different X-ray Talbot-Lau setups for dark-field lung imaging examined in a porcine lung.

Phys Med Biol 2019 Feb 7. Epub 2019 Feb 7.

Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Bayern, GERMANY.

X-ray dark-field imaging is a promising technique for lung diagnosis. Due to the alveolar structure of lung tissue, a higher contrast is obtained by the dark-field image compared to the attenuation image. Animal studies indicate an enhancement regarding the detection of lung diseases in early stages. Read More

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http://dx.doi.org/10.1088/1361-6560/ab051cDOI Listing
February 2019

The effect of magnetic field strength on the response of Gafchromic EBT-3 film.

Phys Med Biol 2019 Feb 7. Epub 2019 Feb 7.

Chemical, Medical & Environmental Science , National Physical Laboratory, Teddington, Middlesex, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND.

With the advent of MRI-guided radiotherapy, the suitability of commercially available radiation dose detectors needs to be assessed. The aim of this study was to investigate the effect of the magnetic field (B-field) on the response of the Gafchromic EBT-3 films. Moreover, as an independent study, we contribute to clarifying the inconsistency of the results of recent published studies, on the effect of B-field on the sensitivity of Gafchromic films. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0503DOI Listing
February 2019

Experimental measurements validate the use of the binary encounter approximation model to accurately compute proton induced dose and radiolysis enhancement from gold nanoparticles.

Phys Med Biol 2019 Feb 7. Epub 2019 Feb 7.

Department of Physics, Narilis, Universite de Namur, Namur, BELGIUM.

In protontherapy, it has been suggested that nanoparticles of high-Z material like gold (GNP) be used as radiosensitizers. The origin of this enhancement phenomenon for proton radiation is not yet well understood and additional mechanistic insights are required. Previous works have highlighted the good capabilities of TRAX to reproduce secondary electron emission from gold material. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0516DOI Listing
February 2019

A stochastic frontier analysis for enhanced treatment quality of high-dose-rate brachytherapy plans.

Phys Med Biol 2019 Feb 7. Epub 2019 Feb 7.

Département de Radio-Oncologie et CR CHU de Québec, Université Laval, 11 Côte du Palais, Québec (QC), G1R 2J6, CANADA.

The purpose of the present study is to develop patient specific unbiased quality control (QC) models for high dose rate (HDR) brachytherapy plans. The proposed models are based on the stochastic frontier analysis formalism, a method of economic modeling. They act as a QC tool by predicting before the treatment planning process starts, the dosimetric coverage achievable for a HDR brachytherapy prostate plan. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0522DOI Listing
February 2019

Recent advances in cardiac SPECT instrumentation and imaging methods.

Authors:
Jing Wu Chi Liu

Phys Med Biol 2019 Feb 6. Epub 2019 Feb 6.

Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, Connecticut, UNITED STATES.

Cardiac SPECT continues to play a critical role in detecting and managing cardiovascular disease, in particularly coronary artery disease (CAD) (Jaarsma et al., 2012; Agostini et al., 2016). Read More

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http://dx.doi.org/10.1088/1361-6560/ab04deDOI Listing
February 2019
3 Reads
2.761 Impact Factor

Quantification of myocardial uptake rate constants in dynamic small-animal SPECT using a cardiac phantom.

Phys Med Biol 2019 Feb 5. Epub 2019 Feb 5.

Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, UNITED STATES.

Myocardial blood flow and myocardial blood flow reserve (MBFR) measurements are often used clinically to quantify coronary microvascular function. Developing imaging-based methods to measure MBFR for research in mice would be advantageous for evaluating new treatment methods for coronary microvascular disease, yet this is more challenging in mice than in humans. This work investigates microSPECT's quantitative capabilities of cardiac imaging by utilizing a multi-part cardiac phantom and applying a known kinetic model to synthesize kinetic data from static data, allowing for assessment of kinetic modeling accuracy. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0472DOI Listing
February 2019
2 Reads

Fast shading correction for cone-beam CT via partitioned tissue classification.

Phys Med Biol 2019 Feb 5. Epub 2019 Feb 5.

University of Science and Technology of China, Hefei, 230026, CHINA.

The quantitative use of cone beam computed tomography (CBCT) in radiation therapy is limited by severe shading artifacts, even with system embedded correction. We recently proposed effective shading correction methods, using planning CT (pCT) as prior information to estimate low-frequency errors in either the projection domain or the image domain. In this work, we further improve the clinical practicality of our previous methods by removing the requirement of prior pCT images. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0475DOI Listing
February 2019
1 Read

Brain SAR of average male Korean child to adult models for mobile phone exposure assessment.

Phys Med Biol 2019 Feb 5;64(4):045004. Epub 2019 Feb 5.

Radio Technology Research Department, Electronics and Telecommunications Research Institute (ETRI), Daejeon, 305-700, Republic of Korea. Author to whom any correspondence should be addressed.

This paper aims to implement average head models of Korean males and investigate age-related differences in the brain for exposure from radiation from mobile phones. Four male head models composed of a total of 69 structures were developed through a statistical investigation of the anatomical morphology for the age groups of 6, 9, 15 and 20-24 years in age, which are named KR-6, KR-9, KR-15, and KR-22 herein. Three numerical bar phone models with a dual-band built-in antenna were applied to calculate the specific absorption rate (SAR) in the brain; the body lengths of models M and M have the mean value and upper 5th percentile value of commercial bar phone models, respectively, with an antenna at the bottom, whereas M has an antenna on top of the phone body, which is the same as in M but rotated 180°. Read More

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http://dx.doi.org/10.1088/1361-6560/aafcdcDOI Listing
February 2019
1 Read

Effects of posture on electric fields of non-invasive brain stimulation.

Phys Med Biol 2019 Feb 1. Epub 2019 Feb 1.

Dept. of Electrical Engineering and Automation, Aalto-yliopisto, Espoo, FINLAND.

The brain moves when the orientation of the head changes. This inter-postural motion has been shown to affect the distribution of cerebrospinal fluid (CSF). As CSF layer thickness affects the distribution of electric fields (EF) in non-invasive brain stimulation methods such as transcranial direct current (TDCS) and magnetic (TMS) stimulation, possible differences in body position between sessions could affect the stimulation efficacy. Read More

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http://dx.doi.org/10.1088/1361-6560/ab03f5DOI Listing
February 2019

Regularised patient-specific stopping power calibration for proton therapy planning based on proton radiographic images.

Phys Med Biol 2019 Feb 1. Epub 2019 Feb 1.

Lyon 1 University and CNRS/IN2P3, UMR 5822, Villeurbanne, 69622, FRANCE.

Proton transmission imaging has been proposed and investigated as imaging modality complementary to X-ray based techniques in proton beam therapy. In particular, it addresses the issue of range uncertainties due to the conversion of an X-ray patient computed tomography (CT) image expressed in Hounsfield Units (HU) to relative stopping power (RSP) needed as input to the treatment planning system. One approach to exploit a single proton radiographic projection is to perform a patient-specific calibration of the CT to RSP conversion curve by optimising the match between a measured and a numerically integrated proton radiography. Read More

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http://dx.doi.org/10.1088/1361-6560/ab03dbDOI Listing
February 2019

Microvascular imaging of the skin.

Phys Med Biol 2019 Feb 1. Epub 2019 Feb 1.

Bioengineering, University of Washington, 5306 24th Ave NE #202, Foege Building, Rm #N410E, Seattle, Washington, 98195, UNITED STATES.

Despite our understanding that the microvasculature plays a multifaceted role in the development and progression of various conditions, we know little about the extent of this involvement. A need exists for non-invasive, clinically meaningful imaging modalities capable of elucidating microvascular information to aid in our understanding of disease, and to aid in the diagnosis/monitoring of disease for more patient-specific care. In this review article, a number of imaging techniques are summarized that have been utilized to investigate the microvasculature of skin, along with their advantages, disadvantages and future perspectives in preclinical and clinical settings. Read More

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http://dx.doi.org/10.1088/1361-6560/ab03f1DOI Listing
February 2019

Functional imaging of tumor vasculature using iodine and gadolinium-based nanoparticle contrast agents: a comparison of spectral micro-CT using energy integrating and photon counting detectors.

Phys Med Biol 2019 Feb 1. Epub 2019 Feb 1.

Singleton Department of Pediatric Radiology, Texas Children's Hospital, Houston, Texas, UNITED STATES.

Advances in computed tomography (CT) hardware have propelled the development of novel CT contrast agents. In particular, the spectral capabilities of X-ray CT can facilitate simultaneous imaging of multiple contrast agents. This approach is particularly useful for functional imaging of solid tumors by simultaneous visualization of multiple targets or architectural features that govern cancer development and progression. Read More

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http://dx.doi.org/10.1088/1361-6560/ab03e2DOI Listing
February 2019
1 Read

Towards patient connected imaging with ACROBEAT: Adaptive CaRdiac cOne BEAm computed Tomography.

Phys Med Biol 2019 Feb 1. Epub 2019 Feb 1.

ACRF Image X Institute, Faculty of Medicine and Health , University of Sydney, Sydney, New South Wales, AUSTRALIA.

Robotic C-arm Cone Beam Computed Tomography (CBCT) systems are playing an increasingly pivotal role in interventional cardiac procedures and high precision radiotherapy treatments. One of the main challenges in any form of cardiac imaging is mitigating the intrinsic motion of the heart, which causes blurring and artefacts in the 3D reconstructed image. Most conventional 3D cardiac CBCT acquisition techniques attempt to combat heart motion through retrospective gating techniques, whereby acquired projections are sorted into the desired cardiac phase after the completion of the scan. Read More

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http://dx.doi.org/10.1088/1361-6560/ab03f4DOI Listing
February 2019

Fast optimized Monte Carlo phase-space generation and dose prediction for low energy X-ray intra-operative radiation therapy.

Phys Med Biol 2019 Feb 1. Epub 2019 Feb 1.

Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Madrid, SPAIN.

Low energy X-ray Intra-Operative Radiation Therapy (IORT) is used mostly for breast cancer treatment with spherical applicators. X-ray IORT treatment delivered during surgery (ex: INTRABEAM®, Carl Zeiss) can benefit from accurate and fast dose prediction in a patient 3D volume. However, full Monte Carlo (MC) simulations are time-consuming and no commercial treatment planning system was available for this treatment delivery technique. Read More

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http://dx.doi.org/10.1088/1361-6560/ab03e7DOI Listing
February 2019
1 Read

Three-dimensional radiotherapy dose prediction on head and neck cancer patients with a hierarchically densely connected U-net deep learning architecture.

Phys Med Biol 2019 Jan 31. Epub 2019 Jan 31.

Radiation Oncology, University of Texas Southwestern Medical Center, 5801 Forest Park Rd., NE3.200, Dallas, Texas, 753090, UNITED STATES.

The treatment planning process for patients with head and neck (H&N) cancer is regarded as one of the most complicated due to large target volume, multiple prescription dose levels, and many radiation-sensitive critical structures near the target. Treatment planning for this site requires a high level of human expertise and a tremendous amount of effort to produce personalized high quality plans, taking as long as a week, which deteriorates the chances of tumor control and patient survival. To solve this problem, we propose to investigate a deep learning-based dose prediction model, Hierarchically Densely Connected U-net, based on two highly popular network architectures: U-net and DenseNet. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab039b
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http://dx.doi.org/10.1088/1361-6560/ab039bDOI Listing
January 2019

Analytical model of DOI-induced time bias in ultra-fast scintillation detectors for TOF-PET.

Phys Med Biol 2019 Jan 31. Epub 2019 Jan 31.

Department of Nuclear Medicine and Radiobiology, Universite de Sherbrooke, CRCHUS/CIMS#1977, 3001, 12th Avenue North, Sherbrooke, Quebec, J1H 5N4, CANADA.

In Positron Emission Tomography (PET), long crystals (≥20 mm) are used to enhance detection efficiency and increase scanner sensitivity. However, for fast time-of-flight (TOF) scanners, this may affect the achievable coincidence time resolution (CTR) due to depth-of-interaction (DOI) induced blur on timing. Currently, the effect of DOI on CTR evaluation with analytical modeling is incorporated using the probability density function (PDF) for attenuation of the annihilation photons with the PDFs of the other scintillation processes. Read More

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http://dx.doi.org/10.1088/1361-6560/ab038bDOI Listing
January 2019

Malignant-benign classification of pulmonary nodules based on random forest aided by clustering analysis.

Phys Med Biol 2019 Jan 31;64(3):035017. Epub 2019 Jan 31.

School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China. These authors contributed equally to this work and should be considered co-first authors.

To help the radiologists better differentiate the benign from malignant pulmonary nodules on CT images, a novel classification scheme was proposed to improve the performance of benign and malignant classifier of pulmonary nodules. First, the pulmonary nodules were segmented with the references to the results from four radiologists. Then, some basic features of the segmented nodules such as the shape, gray and texture are given by calculation. Read More

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http://dx.doi.org/10.1088/1361-6560/aafab0DOI Listing
January 2019

Geometric discrepancy of image-guided radiation therapy in patients with prostate cancer without implanted fiducial markers using a commercial pseudo-CT generation method.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

Radiology, Nagoya City University Hospital, Nagoya, JAPAN.

MR-only simulations provide pseudo-CT images which are segmented into 5 kinds of tissues from DIXON-based images. However, it is difficult to register pseudo-CT images to cone-beam CT (CBCT) images collected for image-guided radiation therapy (IGRT), because of the lack of contrasts among tissues. We validated gaps of IGRT between pseudo-CT or planning CT and CBCT for patients without implanted markers. Read More

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http://dx.doi.org/10.1088/1361-6560/ab02ccDOI Listing
January 2019
1 Read

Studying the effects of metallic components of PET-insert on PET and MRI performance due to gradient switching.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

Interdisciplinary Institute for Technological Innovation (3IT), Sherbrooke, Quebec, CANADA.

Inserting Positron Emission Tomography (PET) detection modules inside an MRI bore imposes extra challenges owing to the behavior of metallic materials in a strong magnetic field. The metallic parts even when placed outside an MRI field of view may not only disturb MRI performance, but could also increase temperature and vibrations, leading to premature failure of PET electronics. To investigate the compatibility of detection modules inside 3 T, 7 T and 9. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0291DOI Listing
January 2019

Data-driven voluntary body motion detection and non-rigid event-by-event correction for static and dynamic PET.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, Connecticut, UNITED STATES.

PET has the potential to perform absolute in vivo radiotracer quantitation. This potential can be compromised by voluntary body motion, which degrades image resolution, alters apparent tracer uptakes, introduces CT-based attenuation correction mismatch artifacts and causes inaccurate parameter estimates in dynamic studies. Existing body motion correction methods include frame-based image-registration (FIR) approaches and real-time motion tracking using external measurement devices. Read More

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http://dx.doi.org/10.1088/1361-6560/ab02c2DOI Listing
January 2019
1 Read
2.761 Impact Factor

FLUKA particle therapy tool for Monte Carlo independent calculation of scanned proton and carbon ion beam therapy.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

EN-STI-BMI, European Organization for Nuclear Research, Geneve, Genève, SWITZERLAND.

While Monte Carlo (MC) codes are considered as the gold standard for dosimetric calculations, the availability of user friendly MC codes suited for particle therapy is limited. Based on the FLUKA MC code and its graphical user interface (GUI) Flair, we developed an easy-to-use tool which enables simple and reliable simulations for particle therapy. In this paper we provide an overview of functionalities of the tool and with the presented clinical, proton and carbon ion therapy examples we demonstrate its reliability and the usability in the clinical environment and show its flexibility for research purposes. Read More

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http://dx.doi.org/10.1088/1361-6560/ab02cbDOI Listing
January 2019
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Unsupervised respiratory signal extraction from ungated cardiac magnetic resonance imaging at rest and during exercise.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

KU Leuven, Leuven, 3000, BELGIUM.

We propose and evaluate a method to estimate a respiratory signal from ungated cardiac magnetic resonance (CMR) images. Ungated CMR images were acquired in 5 subjects who performed exercise at different intensity levels under different physiological conditions while breathing freely. The respiratory motion was estimated by applying principal components analysis (PCA). Read More

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http://dx.doi.org/10.1088/1361-6560/ab02cdDOI Listing
January 2019

A dual-purpose MRI acquisition to combine 4D-MRI and dynamic contrast-enhanced imaging for abdominal radiotherapy planning.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

Department of Radiotherapy, University Medical Center Utrecht, Utrecht, NETHERLANDS.

For successful abdominal radiotherapy it is crucial to have a clear tumor definition and an accurate characterization of the motion. While dynamic contrast-enhanced (DCE) MRI aids tumor visualization, it is often hampered by motion artifacts. 4D-MRI characterizes this motion, but often lacks the contrast to clearly visualize the tumor. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0295DOI Listing
January 2019
2 Reads

Phantom evaluations of low frequency MR elastography.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, UNITED STATES.

Intrinsic activation MR elastography (IA-MRE) is a novel technique which seeks to estimate brain mechanical properties non-invasively and without external mechanical drivers. The method eliminates actuation hardware and patient discomfort while capitalizing on the brain's intrinsic low frequency motion. This study explores low frequency actuation (1 Hz) MR elastography in phantoms and analyzes performance of non-linear inversion (NLI) of viscoelastic and poroelastic mechanical models as a framework for assessing clinical results from IA-MRE. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0290DOI Listing
January 2019

Effects of transverse heterogeneities on the most likely path of protons.

Phys Med Biol 2019 Jan 29. Epub 2019 Jan 29.

Radiotherapy, CREATIS CLB, 28 rue Laennec, Lyon, 69008, FRANCE.

The use of a most likely path (MLP) formalism for protons to account for the effects of multiple Coulomb scattering has improved the spatial resolution in proton computed tomography (pCT). However, this formalism assumes a homogeneous medium and a continuous scattering of protons. In this paper, we quantify the path prediction error induced by transverse heterogeneities to assess whether correcting for such errors might improve the spatial resolution of pCT. Read More

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http://dx.doi.org/10.1088/1361-6560/ab02a8DOI Listing
January 2019

A linear relationship for the LET-dependence of Gafchromic EBT3 film in spot-scanning proton therapy.

Phys Med Biol 2019 Jan 23. Epub 2019 Jan 23.

Radiation Oncology, Mayo Clinic, Rochester, Minnesota, UNITED STATES.

Radiochromic film is a valuable dosimetric tool, primarily due to its sub-millimeter spatial resolution. For accurate proton dosimetry, the dependence of film response on linear energy transfer must be characterized and calibrated. In this work, we characterized film under-response, or "quenching," as a function of dose-weighted linear energy transfer (LETd) in several proton fields and established a simple, linear relationship with LETd. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0114DOI Listing
January 2019
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First prototyping of a dedicated PET system with the hemisphere detector arrangement.

Phys Med Biol 2019 Jan 23. Epub 2019 Jan 23.

QST, National Institute of Radiological Sciences, Chiba, JAPAN.

A strong demand is expected for high-sensitivity, high-resolution, and low-cost brain positron emission tomography (PET) imaging for early diagnosis of dementia as well as for general neuroscience studies. Therefore, we have proposed novel geometries of a hemisphere detector arrangement for high-sensitivity brain imaging, in which an add-on detector at the chin position or neck position helps in sensitivity uniformity improvement. In this study, we developed the first prototype system for proof-of-concept using 4-layer depth-of-interaction detectors, each of which consisted of 16×16×4 Zr-doped GSO crystals with dimensions of 2. Read More

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http://dx.doi.org/10.1088/1361-6560/ab012cDOI Listing
January 2019
2 Reads

Optical elastography: tracking surface waves with digital image correlation.

Phys Med Biol 2019 Jan 23. Epub 2019 Jan 23.

LaMCos, INSA-Lyon, Villeurbanne , FRANCE.

Elastography consists in evaluating the propagation speed of waves into a tissue to estimate its stiffness. Usually this method is based on Ultrasounds, Magnetic Resonance Imaging or Optical coherent tomography. This paper proposes a simple optic method using ultrafast cameras. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0141DOI Listing
January 2019
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Development and application of a simple method for calculating breast dose from radio-guided occult lesion localisation using iodine-125 seeds (ROLLIS).

Phys Med Biol 2019 Jan 23. Epub 2019 Jan 23.

Medical Engineering and Physics, Royal Perth Hospital, Perth, Western Australia, AUSTRALIA.

Radio-guided occult lesion localisation using iodine-125 seeds (ROLLIS) for surgical removal of impalpable breast lesions has been increasingly used as an alternative to hook-wire localisation. This technique involves implanting a low-level radioactive seed into the lesion, followed by excision of the lesion guided using a hand-held gamma probe. Although the level of radiation exposure from this procedure is low, there has not been an appropriate method to quantify the organ dose. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0149DOI Listing
January 2019
5 Reads

A comparison of hyperelastic constitutive models applicable to shear wave elastography (SWE) data in tissue-mimicking materials.

Phys Med Biol 2019 Jan 23. Epub 2019 Jan 23.

Biomedical Engineering, Michigan Technological University, Houghton, Michigan, 49931-1295, UNITED STATES.

Shear wave elastography (SWE) techniques have received substantial attention in recent years. Strong experimental data in SWE suggest that shear wave speed changes significantly due to the known acoustoelastic effect (AE). This presents both challenges and opportunities toward in vivo characterization of biological soft tissues. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0137DOI Listing
January 2019
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Impact of backscatter material thickness on the depth dose of orthovoltage irradiators for radiobiology research.

Phys Med Biol 2019 Feb 20;64(5):055001. Epub 2019 Feb 20.

Department of Radiation Medicine, The University of Kentucky, Lexington, KY 40536, United States of America. Author to whom any correspondence should be addressed. Radiation Medicine, University of Kentucky, Markey Cancer Center, Rm CC063, 800 Rose St., Lexington, KY 40536-0293, United States of America.

The orthovoltage x-ray energy frequently used in radiation research is prone to dosimetry errors due to insufficient backscatter conditions. In many radiobiology studies, especially for cell irradiations, precise dose calculation algorithms such as Convolution-Superposition or Monte Carlo are impractical and as such, less accurate hand calculation methods are used for dose estimation. These dose estimation methods typically assume full backscatter conditions. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0120DOI Listing
February 2019
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Comparison of CT ventilation imaging and hyperpolarised gas MRI: effects of breathing manoeuvre.

Phys Med Biol 2019 Jan 23. Epub 2019 Jan 23.

Polaris, Academic Unit of Radiology, University of Sheffield, Sheffield, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND.

Image registration of lung CT images acquired at different inflation levels has been proposed as a surrogate method to map lung 'ventilation'. Prior to clinical use, it is important to understand how this technique compares with direct ventilation imaging modalities such as hyperpolarised gas MRI. However, variations in lung inflation level have been shown to affect regional ventilation distributions. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0145DOI Listing
January 2019
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Feasibility of MRI-only photon and proton dose calculations for pediatric patients with abdominal tumors.

Phys Med Biol 2019 Jan 22. Epub 2019 Jan 22.

Department of Radiotherapy, University Medical Center Utrecht, Utrecht, NETHERLANDS.

The purpose of this study was to develop a method enabling synthetic computed tomography (sCT) generation of the whole abdomen using magnetic resonance imaging (MRI) images of pediatric patients with abdominal tumors. The proposed method relies on an automatic atlas-based segmentation of bone and lungs followed by an MRI intensity to synthetic Hounsfield unit conversion. Separate conversion algorithms were used for bone, lungs and soft-tissue. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0095DOI Listing
January 2019
5 Reads