13,723 results match your criteria Physics in medicine and biology[Journal]


The potential of photon-counting CT for quantitative contrast-enhanced imaging in radiotherapy.

Phys Med Biol 2019 Apr 18. Epub 2019 Apr 18.

Physique, Université de Montréal, Montréal, Quebec, CANADA.

The aim of this study is to use a simulation environment to evaluate the potential of using photon-counting CT (PCCT) against dual-energy CT (DECT) in the context of quantitative contrast-enhanced CT for radiotherapy. An adaptation of Bayesian eigentissue decomposition by Lalonde (2017 <i>Med. Phys. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab1af1
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http://dx.doi.org/10.1088/1361-6560/ab1af1DOI Listing
April 2019
1 Read

ADMM-based deep reconstruction for limited-angle CT.

Phys Med Biol 2019 Apr 18. Epub 2019 Apr 18.

College of Mathematics and Statistics, Chongqing University, Chongqing, CHINA.

In the real applications of computed tomography (CT) imaging, the projection data of the scanned objects are usually acquired within a limited-angle range because of the limitation of the scanning condition. Under these circumstances, conventional analytical algorithms, such as filtered back-projection (FBP), do not work because the projection data are incomplete. The regularization method has proven to be effective for tomographic reconstruction from under-sampled measurements. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1abaDOI Listing

Physics-based spectral compensation algorithm for X-ray CT with primary modulator.

Phys Med Biol 2019 Apr 18. Epub 2019 Apr 18.

Advanced Therapies, Siemens Healthineers, Forchheim, GERMANY.

X-ray computed tomography (CT) scatter correction using primary modulator has been continuously developed over the past years, with progress in improving the performance of scatter correction. In this work, we further advance the primary modulator technique towards practical applications where the spectral nonuniformity caused by the modulator continues to be a challenging problem. A physics-based spectral compensation algorithm is proposed to adaptively correct for the spectral nonuniformity, and hence to reduce the resultant ring artifacts on reconstructed CT images. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab1ad0
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http://dx.doi.org/10.1088/1361-6560/ab1ad0DOI Listing
April 2019
1 Read

Enhanced reconstruction in magnetic particle imaging by whitening and randomized SVD approximation.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Department of Computer Science, University College London, London, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND.

Magnetic particle imaging (MPI) is a medical imaging modality of recent origin, and it exploits the nonlinear magnetization phenomenon to recover a spatially dependent concentration of nanoparticles. In practice, image reconstruction in MPI is frequently carried out by standard Tikhonov regularization with nonnegativity constraint, which is then minimized by a Kaczmarz type method. In this work, we revisit two issues in the numerical reconstruction in MPI in the lens of inverse theory, i. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1a4fDOI Listing

Localization of liver lesions in abdominal CT imaging: II. Mathematical model observer performance correlates with human observer performance for localization of liver lesions in abdominal CT imaging.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA, Rochester, Minnesota, UNITED STATES.

Purpose: Determination of the effect of protocol modifications on diagnostic performance in CT with human observers is extremely time-consuming, limiting the applicability of such methods in routine clinical practice. In this work, we sought to determine whether a channelized Hotelling observer (CHO) could predict human observer performance for the task of liver lesion localization as background, reconstruction algorithm, dose, and lesion size were varied. Materials and Methods: Liver lesions (5mm, 7mm, and 9mm) were digitally inserted into the CT projection data of patients with normal livers and water phantoms. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1a62DOI Listing

Observation and modulation of the dissolution of histotripsy-induced bubble clouds with high-frame rate plane wave imaging.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Radiology, University of Chicago Medical Center, Chicago, Illinois, UNITED STATES.

Focused ultrasound therapies are a noninvasive means to ablate tissue. Histotripsy utilizes short ultrasound pulses with sufficient tension to nucleate bubble clouds that impart lethal strain to the surrounding tissues. Tracking bubble cloud dissolution between the application of histotripsy pulses is critical to ensure treatment efficacy. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1a64DOI Listing

Microwave thermal ablation using CT-scanner for predicting the variation of ablated region over time: advantages and limitations.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Technical Unit of Radiation Biology and Human Health, ENEA, Casaccia Research Centre, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Rome, Rome, ITALY.

This study aims at investigating in real-time the structural and dynamical changes occurring in an ex-vivo tissue during a microwave thermal ablation (MTA) treatment. The proposed set-up was based on ex vivo liver tissue inserted in a specific box, in which 3 fibre-optic (FO) temperature probes were introduced to measure the temperature increase over time. Computed Tomography (CT) imaging technique was exploited to experimentally study in real-time the Hounsfield Units (HU) modification occurring during MTA. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1a67DOI Listing

Efficient detrending of uniform images for accurate determination of the noise power spectrum at low frequencies.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Hospital Clínico Universitario Virgen de la Arrixaca, El Palmar, Murcia, SPAIN.

The noise power spectrum (NPS) of a digital x-ray imaging device is usually estimated from the average of periodograms of ROIs in images obtained with uniform radiation fields. In order to mitigate low frequency trends, present in the images and not arising from stochastic processes, detrending methods are applied to the images before being Fourier transformed. The most common of these methods subtracts a second-order polynomial fit from the image. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1a68DOI Listing

Ultrasound multiple scattering with microbubbles can differentiate between tumor and healthy tissue in vivo.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, UNITED STATES.

Most solid tumors are characterized by highly dense, isotropic vessel networks. Characterization of such features has shown promise for early cancer diagnosis. Ultrasound diffusion has been used to characterize the micro-architecture of complex media, such as bone and the lungs. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab1a44
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http://dx.doi.org/10.1088/1361-6560/ab1a44DOI Listing
April 2019
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ADAM phantom to test 4D medical imaging and dose delivery devices.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Agricultural, Food and Forestry System, Universita di Firenze, Florence, ITALY.

Radiotherapy treatment of moving lesions is a challenging task in which different strategies can be used. The clinical implementation of the variety of complex technical solutions pursued to treat cancer, while sparing healthy tissues, requires accurate quality assurance tests and adequate phantoms. The aim of this work is to report on the Anthropomorphic Dynamic breAthing Model (ADAM) and on its applications to test image quality and dose delivery for four-dimensional (4D) techniques used to compensate for breathing-induced tumor motion. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab1a49
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http://dx.doi.org/10.1088/1361-6560/ab1a49DOI Listing
April 2019
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Localization of liver lesions in abdominal CT imaging: I. Correlation of human observer performance between anatomical and uniform backgrounds.

Phys Med Biol 2019 Apr 17. Epub 2019 Apr 17.

Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA, Rochester, UNITED STATES.

Purpose: The purpose of this study was to determine the correlation between human observer performance for localization of small low contrast lesions within uniform water background versus an anatomical liver background, under the conditions of varying dose, lesion size, and reconstruction algorithm. Materials and Methods: Liver lesions (5mm, 7mm, and 9mm, contrast: -21HU) were digitally inserted into CT projection data of 10 normal patients in vessel-free liver regions. Noise was inserted into the projection data to create three image sets: full dose and simulated half and quarter doses. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1a45DOI Listing

Backscattered electron emission after proton impact on gold nanoparticles with and without polymer shell coating.

Phys Med Biol 2019 Apr 15. Epub 2019 Apr 15.

Department of Physics, NISM, Narilis, Univesity of Namur, Namur, BELGIUM.

This work aims at measuring experimentally proton induced secondary electron energy spectra after interaction with Gold Nano Particles (GNPs) and polymer-coated GNPs. Backscattered electron energy spectra were collected over a 0 to 1000 eV energy range using a Retarding Field Analyzer. This paper presents the spectra obtained for proton beam energies of 0. Read More

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http://dx.doi.org/10.1088/1361-6560/ab195fDOI Listing

Dynamic-dual-energy spectral CT for improving multi-material decomposition in image-domain.

Phys Med Biol 2019 Apr 15. Epub 2019 Apr 15.

Department of Engineering Physics, Tsinghua University, Beijing, CHINA.

Dual-energy CT, as well as spectral CT, has a great potential in material decomposition. However, dual-energy CT is difficult to apply to multi-material decomposition because the number of energy bins is limited to two. Current spectral CT systems have more energy bins, but the statistical noise in each energy bin is high because of the decreased photon number, which causes errors in the material decomposition results. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab196d
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http://dx.doi.org/10.1088/1361-6560/ab196dDOI Listing
April 2019
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A six-degree-of-freedom robotic motion system for quality assurance of real-time image-guided radiotherapy.

Phys Med Biol 2019 Apr 15. Epub 2019 Apr 15.

ACRF Image X Institute, The University of Sydney Central Clinical School, University of Sydney, Sydney, New South Wales, AUSTRALIA.

In this study we develop and characterise a six degree-of-freedom (6DoF) robotic motion system for quality assurance of real-time image-guided radiotherapy techniques. The system consists of a commercially available robotic arm, an acrylic phantom with embedded Calypso markers, a custom base plate to mount the robot to the treatment couch, and control software implementing the appropriate sequence of transformations to reproduce measured tumour motion traces. The robotic motion system was evaluated in terms of the set-up and motion trace repeatability, static localization accuracy and dynamic localization accuracy. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1935DOI Listing

Deep iterative reconstruction estimation (DIRE): approximate iterative reconstruction estimation for low dose CT imaging.

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

INSERM, Universite de Rennes I, Rennes, FRANCE.

The image quality in low dose computed tomography (LDCT) can be severely degraded by amplified mottle noise and streak artifacts. Although the iterative reconstruction (IR) algorithms bring sound improvements, their high computation cost remains a major inconvenient. In this work, a deep iterative reconstruction estimation (DIRE) strategy is developed to estimate IR images from LDCT analytic reconstructions images. Read More

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http://dx.doi.org/10.1088/1361-6560/ab18dbDOI Listing
April 2019
2 Reads
2.761 Impact Factor

Towards a metamaterial approach for fast timing in PET: experimental proof-of-concept.

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

PH-CMX-DS, CERN, GENEVA, SWITZERLAND.

Achieving fast timing in positron emission tomography (PET) at the level of few tenth of picoseconds is limited by the photon emission rate of existent materials with standard scintillation mechanisms. This has led to consider quantum confined excitonic sub-1ns emission in semiconductors as a viable solution to enhance the amount of fast-emitted photons produced per gamma event. However the introduction of nanocrystals and nanostructures into the domain of radiation detectors is a challenging problem. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab18b3
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http://dx.doi.org/10.1088/1361-6560/ab18b3DOI Listing
April 2019
9 Reads

Hybrid proton-photon inverse optimization with uniformity-regularized proton and photon target dose.

Authors:
Hao Gao

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

Emory University, Atlanta, UNITED STATES.

The goal of radiation therapy is to deliver tumoricidal dose to clinical target volume (CTV) while sparing organs-at-risk (OAR). We hypothesize that the joint use of proton and photon radiation therapy via appropriate hybrid proton-photon inverse planning method will be more favorable than proton or photon therapy alone, in terms of optimized combination of CTV coverage and OAR sparing. This work develops hybrid proton-photon inverse optimization method that simultaneously optimizes proton and photon variables. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab18c7
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http://dx.doi.org/10.1088/1361-6560/ab18c7DOI Listing
April 2019
2 Reads

Dual-ended readout of bismuth germanate to improve timing resolution in time-of-flight PET.

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

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

The scintillator bismuth germanate (BGO) has attractive properties for positron emission tomography (PET) systems such as high stopping power, high photo-fraction, and relatively low cost. However, its moderate scintillation light yield and slow rise and decay time compared to lutetium (yttrium) oxyorthosilicate (L(Y)SO) results in a degradation of coincidence timing resolution when scintillation photons are used for timing. Recently, it has been reported that the coincidence timing resolution of BGO can be improved by detecting Cerenkov photons, while scintillation photons still provide energy information. Read More

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http://dx.doi.org/10.1088/1361-6560/ab18daDOI Listing

Intelligent inverse treatment planning via deep reinforcement learning, a proof-of-principle study in high dose-rate brachytherapy for cervical cancer.

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

Department of Radiation Oncology, UT Southwestern Medical Center, 6363 Forest Park Rd. BL10.202G, MC9315, Dallas, Texas, 75390-9315, UNITED STATES.

Inverse treatment planning in radiation therapy is formulated as optimization problems. The objective function and constraints consist of multiple terms designed for different clinical and practical considerations. Weighting factors of these terms are needed to define the optimization problem. Read More

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http://dx.doi.org/10.1088/1361-6560/ab18bfDOI Listing
April 2019
2 Reads
2.761 Impact Factor

Repeatability of texture features derived from magnetic resonance and computed tomography imaging and use in predictive models for non-small cell lung cancer outcome.

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

Radiation Oncology, Virginia Commonwealth University Health System, Richmond, Virginia, UNITED STATES.

Purpose: To evaluate the repeatability of MRI and CT derived texture features and to investigate the feasibility of use in predictive single and multi-modality models for radiotherapy of non-small cell lung cancer. Methods: Fifty-nine texture features were extracted from unfiltered and wavelet filtered images. Repeatability of test-retest features from helical 4D CT scans, true fast MRI with steady state precession (TRUFISP), and volumetric interpolation breath-hold examination (VIBE) was determined by the concordance correlation coefficient (CCC). Read More

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http://dx.doi.org/10.1088/1361-6560/ab18d3DOI Listing

Performance evaluation of a whole-body prototype PET scanner with four-layer DOI detectors.

Phys Med Biol 2019 Apr 12. Epub 2019 Apr 12.

National Institute of Radiological Sciences, Chiba, JAPAN.

Parallax error caused by the detector crystal thickness degrades spatial resolution at the peripheral regions of the field-of-view (FOV) of a scanner. To resolve this issue, depth-of-interaction (DOI) measurement is a promising solution to improve the spatial resolution and its uniformity over the entire FOV. Even though DOI detectors have been used in dedicated systems with a small ring diameter such as for human brain, breast and small animals, the use of DOI detectors for a large bore whole-body PET system has not been demonstrated yet. Read More

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http://dx.doi.org/10.1088/1361-6560/ab18b2DOI Listing
April 2019
2 Reads

NEMA NU 4-2008 and in-vivo imaging performance of RAYCAN trans-PET/CT X5 small animal imaging system.

Phys Med Biol 2019 Apr 11. Epub 2019 Apr 11.

Turun PET keskus, Turku, FINLAND.

The RAYCAN Trans-PET/CT X5 is a preclinical positron emission tomography and computed tomography (PET/CT) system intended for in-vivo imaging of rats and mice, featuring all-digital readout electronics for PET data acquisition. The National Electrical Manufacturers Association (NEMA) NU 4-2008 performance evaluation was conducted on the RAYCAN Trans-PET/CT X5 in addition to assessing in-vivo imaging performance of the system on live animals. The performance characteristics of the system were evaluated, including system spatial resolution, count rate performance, sensitivity and image quality. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1856DOI Listing
April 2019
3 Reads

Estimation of thyroid volume from scintigraphy through 2D/3D registration of a statistical shape model.

Phys Med Biol 2019 Apr 11. Epub 2019 Apr 11.

Nuclear Medicine Division, Second Affiliated Hospital, Dalian Medical University, Dalian, Liaoning 116023, Dalian, CHINA.

Accurate measurement of thyroid volume is important for thyroid diseases diagnosis and therapy. In nuclear medicine, the thyroid volume is usually estimated from scintigraphy images using empirical equations. However, due to the missing of volumetric information from the scintigraphy image, the accuracy of equation-based estimation is imperfect. Read More

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http://dx.doi.org/10.1088/1361-6560/ab186dDOI Listing
April 2019
1 Read
2.761 Impact Factor

Energy dependence of a scintillating fiber detector for preclinical dosimetry with an image guided micro-irradiator.

Phys Med Biol 2019 Apr 11. Epub 2019 Apr 11.

Grand Accélérateur National d'Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, Caen, FRANCE.

The dosimetry of preclinical micro-irradiators is challenging due to their millimetric beams and medium X-ray energy range. Plastic scintillator dosimeters (PSD) are good candidates for such a purpose as they provide a high spatial resolution although they show an energy dependence below 100 keV. The purpose of this study was to assess the energy dependence of a dedicated PSD (called DosiRat) for micro- irradiators dosimetry. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1854DOI Listing
April 2019
3 Reads

Data acquisition system for MAET with magnetic field measurements.

Phys Med Biol 2019 Apr 10. Epub 2019 Apr 10.

Department of Electrical Engineering, Middle East Technical University, METU EEE Dept., Ankara, 06800, TURKEY.

Magneto-Acousto-Electrical Tomography (MAET) is an imaging modality to image the electrical conductivity of biological tissues. It is based on electrical current induction by using ultrasound under a static magnetic field. The aim of this study is to develop a data acquisition system for MAET based on magnetic field measurements. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1809DOI Listing

A GPU-based multi-criteria optimization algorithm for HDR brachytherapy.

Phys Med Biol 2019 Apr 10. Epub 2019 Apr 10.

Centre de Recherche en Cancérologie de l'Université Lava, Universite Laval, L'Hôtel-Dieu de Québec, 9 rue McMahon, Quebec, QC G1R 2J6, Canada, Quebec, Quebec, G1Y 2S4, CANADA.

Currently in HDR brachytherapy planning, a manual fine-tuning of an objective function is necessary to obtain case-specific valid plans. This study intends to facilitate this process by proposing two patient-specific inverse planning algorithms for HDR prostate brachytherapy: knowledge-based multi-criteria optimization (kMCO) and brute-force multi-criteria optimization (bMCO). Two GPU-based optimization engines including simulated annealing (gSA) and a quasi-Newton optimizer (gL-BFGS) were implemented to compute multiple plans in parallel. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1817DOI Listing

Prediction of positron emitter distributions for range monitoring in carbon ion therapy: an analytical approach.

Phys Med Biol 2019 Apr 10. Epub 2019 Apr 10.

Department for Medical Physics, Ludwig-Maximilians-Universitat Munchen, Munchen, Bayern, GERMANY.

Range verification is one of the most relevant tasks in ion beam therapy. In the case of carbon ion therapy, positron emission tomography (PET) is the most widely used method for this purpose, which images the β<sup>+</sup>-activation following nuclear interactions of the ions with the tissue nuclei. Since the positron emitter activity profile is not directly proportional to the dose distribution, until today only its comparison to a prediction of the PET profile allows for treatment verification. Read More

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http://dx.doi.org/10.1088/1361-6560/ab17f9DOI Listing
April 2019
2 Reads

Improving iodine contrast to noise ratio using virtual monoenergetic imaging and prior-knowledge-aware iterative denoising (mono-PKAID).

Phys Med Biol 2019 Apr 10. Epub 2019 Apr 10.

Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA, Rochester, UNITED STATES.

Multi-energy CT acquires simultaneous multiple x-ray attenuation measurements from different energy spectra which facilitates the computation of virtual monoenergetic images (VMI) at a specific photon energy (keV). Since the contrast between iodine attenuation and the attenuation of surrounding soft tissues increases at lower x-ray energies, VMIs in the range of 40-70 keV can be used to improve iodine visualization. However, at lower energy levels, image noise in VMIs is substantially increased, which counteracts the benefits from the increased iodine contrast, resulting in a decreased iodine contrast-to-noise ratio (CNR). Read More

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http://dx.doi.org/10.1088/1361-6560/ab17faDOI Listing

Single-view cone-beam x-ray luminescence optical tomography based on Group_YALL1 method.

Phys Med Biol 2019 Apr 10. Epub 2019 Apr 10.

School of Communication and Information Engineering, Shanghai University, Shanghai, Shanghai, CHINA.

Single-view cone beam x-ray luminescence optical tomography (CB-XLOT) has the merit of short data acquisition time, which is important for resolving fast biological processes in vivo. However, challenges remain in the reconstruction of single-view CB-XLOT. In our previous work, by using the sparsity-based reconstruction method, we have demonstrated the feasibility of single-view CB-XLOT. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1819DOI Listing
April 2019
1 Read

Sentinel lymph node fingerprinting.

Phys Med Biol 2019 Apr 9. Epub 2019 Apr 9.

Department of Biomedical Engineering, University of Basel, Basel, SWITZERLAND.

Background - When locating the Sentinel Lymph Node (SLN), surgeons use state-of-the-art imaging devices, such as a 1-dimensional gamma probe or less widely spread a 2-dimensional gamma camera. These devices project the 3D subspace onto a 1D respectively 2D space, hence loosing accuracy and the depth of the SLN which is very important, especially in the head and neck area with many critical structures in close vicinity. Recent methods which use a multi-pinhole collimator and a single gamma detector image try to gain a depth estimation of the SLN. Read More

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http://dx.doi.org/10.1088/1361-6560/ab177dDOI Listing
April 2019
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Processing of prompt gamma-ray timing data for proton range measurements at a clinical beam delivery.

Phys Med Biol 2019 Apr 9. Epub 2019 Apr 9.

Oncoray, National Center for Radiation Research in Oncology, University of Technology, Dresden, Dresden, GERMANY.

In proton therapy, patients benefit from the precise deposition of the dose in the tumor volume due to the interaction of charged particles with matter. Currently, the determination of the beam range in the patient's body during the treatment is not a clinical standard. This lack causes broad safety margins, which limits the potential of proton therapy. Read More

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http://dx.doi.org/10.1088/1361-6560/ab176dDOI Listing
April 2019
1 Read

Modeling the DQE(f) of photon-counting detectors: impact of the pixel sensitivity profile.

Phys Med Biol 2019 Apr 9. Epub 2019 Apr 9.

Siemens Healthcare GmbH, Erlangen, Bayern, GERMANY.

Purpose: To find comprehensive equations for the frequency-dependent MTF and DQE of photon counting detectors including the effect that the combination of crosstalk with an energy threshold is changing the pixel sensitivity profile and to compare the results with measurements. Methods: The framework of probability-generating functions (PGF) is used to find a simple method to derive the MTF and the DQE directly from a Monte-Carlo model of the detection process. Results: In combination with realistic model parameters for the detector, the method is used to predict the MTF and the DQE for different pixel sizes and thresholds. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab1766
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http://dx.doi.org/10.1088/1361-6560/ab1766DOI Listing
April 2019
4 Reads

Principal component analysis for fast and model-free denoising of multi b-value diffusion-weighted MR images.

Phys Med Biol 2019 Apr 9. Epub 2019 Apr 9.

Cancer Research UK Cancer Imaging Centre, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND.

Purpose: Despite the utility of tumour characterisation using quantitative parameter maps from multi-b-value diffusion-weighted MRI (DWI), clinicians often prefer the use of the image with highest diffusion-weighting (b-value), for instance for defining regions of interest. However, these images are typically degraded by noise, as they do not utilize the information from the full acquisition. We present a principal component analysis (PCA) approach for model-free denoising of DWI data. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1786DOI Listing

Characterization of a novel 3D printed patient specific phantom for quality assurance in cranial stereotactic radiosurgery applications.

Phys Med Biol 2019 Apr 9. Epub 2019 Apr 9.

Biomedical Sciences, University of West Attica, University Campus 1, Aegaleo, Athens, Athens, Attica, 12243, GREECE.

In single-isocenter stereotactic radiosurgery/radiotherapy (SRS/SRT) intracranial applications, multiple targets are being treated concurrently, often involving non-coplanar arcs, small photon beams and steep dose gradients. In search for more rigorous quality assurance protocols, this work presents and evaluates a novel methodology for patient-specific pre-treatment plan verification, utilizing 3D printing technology. In a patient's planning CT scan, the external contour and bone structures were segmented and 3D-printed using high-density bone-mimicking material. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1758DOI Listing

Normalized glandular dose (DgN) coefficients from experimental mammographic x-ray spectra.

Phys Med Biol 2019 Apr 8. Epub 2019 Apr 8.

Instituto de Física, Universidade de Sao Paulo, São Paulo, BRAZIL.

Mean glandular dose is the quantity used for dosimetry in mammography and depends on breast-related characteristics, such as thickness and density, and on the x-ray spectrum used for breast imaging. This work aims to present an experimentally-based method to derive polyenergetic normalized glandular dose coefficients (DgNp) from the spectral difference between x-ray spectra incident and transmitted through breast phantoms with glandular/adipose proportions of 30/70 and 50/50 and thicknesses up to 4.5 cm. Read More

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http://dx.doi.org/10.1088/1361-6560/ab171aDOI Listing

A detector's eye view (DEV)-based OSEM algorithm for benchtop x-ray fluorescence computed tomography (XFCT) image reconstruction.

Phys Med Biol 2019 Apr 8;64(8):08NT02. Epub 2019 Apr 8.

Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America. Key Laboratory of Optoelectronics Technology and System, Chongqing University, Ministry of Education, Chongqing 400044, People's Republic of China.

In this study, we developed a detector's eye view (DEV)-based ordered subsets expectation maximization (OSEM) algorithm for more accurate reconstruction of benchtop x-ray fluorescence computed tomography (XFCT) images. The proposed approach was tested using two sets of benchtop XFCT imaging data derived from a newly performed gold nanoparticle (GNP)-containing phantom imaging study and a previously published postmortem benchtop XFCT imaging study of a tumor-bearing mouse injected with GNPs. DEV-based OSEM resulted in higher spatial resolution (up to ~20% decrease in the full width at half maximum values of the regions of interest), compared with filtered back-projection (FBP) and traditional OSEM. Read More

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http://dx.doi.org/10.1088/1361-6560/ab0e9dDOI Listing

Temperature dependence of thermal properties of ex-vivo liver tissue up to ablative temperatures.

Phys Med Biol 2019 Apr 5. Epub 2019 Apr 5.

Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome, Roma, Lazio, ITALY.

Thermal properties of ex-vivo bovine liver were measured as a function of the temperature, by heating tissue samples in a temperature-controlled oil bath over a temperature range from about 21°C to about 113°C. Results evidenced temperature-dependent non-linear changes of the thermal properties, with the temperature of 100°C representing a break point: the thermal properties increased with temperature up to 99°C and then decreased above 100°C. The rate of increase appeared dramatic between 90°C and 99°C, owing to the onset of vaporisation of water contained into the tissue. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1663DOI Listing
April 2019
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MRI artifact simulation for clinically relevant MRI sequences for guidance of prostate HDR brachytherapy.

Phys Med Biol 2019 Apr 4. Epub 2019 Apr 4.

Image Sciences Institute, University Medical Center Utrecht, P.O. Box 85500, 3508 GA, Room Q0S.459 , Utrecht , The Netherlands, Utrecht, NETHERLANDS.

For the purpose of magnetic resonance imaging (MRI) guidance of prostate high-dose-rate (HDR) brachytherapy, this paper presents a study on the potential of clinically relevant MRI sequences to facilitate tracking or localization of brachytherapy devices (HDR source/titanium needle), and which could simultaneously be used to visualize the anatomy. The tracking or localization involves simulation of the MRI artifact in combination with a template matching algorithm. Simulations of the MRI artifacts induced by an HDR brachytherapy source and a titanium needle were implemented for four types of sequences: spoiled gradient echo, spin echo, balanced steady-state free precession (bSSFP) and bSSFP with spectral attenuated inversion recovery (SPAIR) fat suppression. Read More

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http://dx.doi.org/10.1088/1361-6560/ab15edDOI Listing
April 2019
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Evaluation of pinhole collimator materials for micron-resolution ex-vivo SPECT.

Phys Med Biol 2019 Apr 4. Epub 2019 Apr 4.

Radiation Detection and Matter, Technische Universiteit Delft, Department of Applied Sciences, Mekelweg 15, 2629 JB, Delft, Delft, NETHERLANDS.

Pinhole collimation is widely recognized for offering superior resolution-sensitivity trade-off in SPECT imaging of small subjects. The newly developed EXIRAD-3D autoradiography technique (MILabs B.V. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1618DOI Listing

NEMA NU-4 performance evaluation of a non-human primate animal PET.

Phys Med Biol 2019 Apr 4. Epub 2019 Apr 4.

Institute of High Energy Physics Chinese Academy of Sciences, Beijing, Beijing, CHINA.

The Eplus-260 primate PET is an animal PET imaging system developed by the Institute of High Energy Physics, Chinese Academy of Sciences, which is designed to image non-human primates, especially the brain of large non-human primates. The system consists of 48 block detectors arranged in two 24-sided rings with a ring diameter of 263 mm and an axial extent of 64 mm. Each block detector is composed of a 16 × 16 cerium-doped lutetium-yttrium orthosilicate crystal array with a pixel size of 1. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1614DOI Listing

A hybrid proton and hyperpolarized gas tagging MRI technique for lung respiratory motion imaging: the feasibility study.

Phys Med Biol 2019 Apr 4. Epub 2019 Apr 4.

Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hongkong, CHINA.

Purpose: To develop a novel hybrid 3D hyperpolarized (HP) gas tagging MRI technique and to evaluate it for lung respiratory motion measurement with comparison to deformable image registrations (DIR) methods. Method: Three healthy subjects underwent a hybrid MRI which combines 3D HP gas tagging MRI (t-MRI) with a low resolution (Low-R, 4.5mm isotropic voxels) 3D proton MRI (p-MRI), plus a high resolution (High-R, 2. Read More

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http://dx.doi.org/10.1088/1361-6560/ab160cDOI Listing
April 2019
2.761 Impact Factor

Performance of a dual-layer scanner for hybrid SPECT/CBCT.

Phys Med Biol 2019 Apr 4. Epub 2019 Apr 4.

Image Sciences Institute / Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, NETHERLANDS.

Purpose Fluoroscopic procedures involving radionuclides would benefit from interventional nuclear imaging by obtaining real-time feedback on the activity distribution. We have previously proposed a dual-layer detector that offers such procedural guidance by simultaneous fluoroscopic and nuclear planar imaging. Acquisition of single photon computed tomography (SPECT) and cone beam computed tomography (CBCT) could provide additional information on the activity distribution. Read More

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http://iopscience.iop.org/article/10.1088/1361-6560/ab15f6
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http://dx.doi.org/10.1088/1361-6560/ab15f6DOI Listing
April 2019
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Guaranteed [Formula: see text]-optimal solutions with the linear optimizer ART3+O.

Authors:
Bram L Gorissen

Phys Med Biol 2019 Apr 4;64(7):075017. Epub 2019 Apr 4.

Massachusetts General Hospital & Harvard Medical School, Boston, MA, United States of America.

The linear optimization algorithm ART3+O introduced by Chen et al (2010 Med. Phys. 37 4938-45) can efficiently solve large scale inverse planning problems encountered in radiation therapy by iterative projection. Read More

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http://stacks.iop.org/0031-9155/64/i=7/a=075017?key=crossref
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http://dx.doi.org/10.1088/1361-6560/ab0a2eDOI Listing
April 2019
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Dynamic fluence field modulation in computed tomography using multiple aperture devices.

Phys Med Biol 2019 Apr 2. Epub 2019 Apr 2.

Department of Biomedical Engineering, Johns Hopkins University, 720 Rutland Avenue, Baltimore, Maryland, MD 21205, USA, Baltimore, 21205, UNITED STATES.

A novel beam filter consisting of multiple aperture devices (MADs) has been developed for dynamic fluence field modulation (FFM) in CT. Each MAD achieves spatial modulation of x-ray through fine-scale, highly attenuating tungsten bars of varying widths and spacings. Moir\'e patterns produced by relative motions between two MADs provide versatile classes of modulation profiles. Read More

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http://dx.doi.org/10.1088/1361-6560/ab155eDOI Listing

Direct measurement of ion chamber correction factors, kQ and kB, in a 7 MV MRI-linac.

Phys Med Biol 2019 Apr 1. Epub 2019 Apr 1.

Department of Radiotherapy, Universitair Medisch Centrum Utrecht, HP Q.00.118, Heidelberglaan 100, 3584 CX Utrecht, THE NETHERLANDS, Utrecht, NETHERLANDS.

The output of MRI-integrated photon therapy (MRgXT) devices is measured in terms of absorbed dose to water, <i>D</i><sub>w</sub>. Traditionally this is done with reference type ion chambers calibrated in a beam quality Q<sub>0</sub> without magnetic field. To correct the ion chamber response for the application in the magnetic field, a factor needs to be applied that corrects for both beam quality Q and the presence of the magnetic field <i>B</i>, <i>k</i><sub>Q,<i>B</i></sub>. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1511DOI Listing

A study of inter-crystal scatter in dual-layer offset scintillator arrays for brain-dedicated PET scanners.

Phys Med Biol 2019 Apr 1. Epub 2019 Apr 1.

Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, CANADA.

A dual-layer offset (DLO) detector enables depth-of-interaction (DOI) through light sharing between two layers of scintillation arrays with a single-ended readout (SER) scheme. However, the SER scheme in DLO detectors may lead to a layer misassignment when inter-crystal scattering occurs. The aim of this work is to study inter-crystal scattering and evaluate the effects of layer misidentifications in DLO detectors on the performance of scanners suitable for a brain-dedicated PET insert. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1503DOI Listing
April 2019
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Predicting VMAT patient-specific QA results using a support vector classifier trained on treatment plan characteristics and linac QC metrics.

Phys Med Biol 2019 Mar 28. Epub 2019 Mar 28.

Medical Physics, Ottawa Hospital, Ottawa, Ontario, CANADA.

The use of treatment plan characteristics to predict patient-specific quality assurance (QA) measurement results has recently been reported as a strategy to help facilitate automated pre-treatment verification workflows or to provide a virtual assessment of delivery quality. The goal of this work is to investigate the potential of using treatment plan characteristics and linac performance metrics (i.e. Read More

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http://dx.doi.org/10.1088/1361-6560/ab142eDOI Listing
March 2019
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Atlas-based automatic planning and 3D-2D fluoroscopic guidance in pelvic trauma surgery.

Phys Med Biol 2019 Mar 28. Epub 2019 Mar 28.

Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, UNITED STATES.

Purpose: Percutaneous screw fixation in pelvic trauma surgery is a challenging procedure that often requires long fluoroscopic exposure times and trial-and-error attempts. We report a method to automatically plan surgical trajectories using preoperative CT and assist device placement by augmenting the fluoroscopic scene with planned trajectories. Method. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1456DOI Listing

Quantifying T2 relaxation time changes within lesions defined by apparent diffusion coefficient in grey and white matter in acute stroke patients.

Phys Med Biol 2019 Mar 28. Epub 2019 Mar 28.

Department of Neuroscience, University of Bristol, Bristol, Bristol, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND.

Apparent diffusion coefficient (ADC) of cerebral water, as measured by diffusion MRI, rapidly decreases in ischaemia highlighting a lesion in acute stroke patients. The MRI T2 relaxation time changes in ischaemic brain such that T2 in ADC lesions may be informative of the extent of tissue damage, potentially aiding in stratification for treatment. We have developed a novel user-unbiased method of determining the changes in T2 in ADC lesions as a function of clinical symptom duration based on voxel-wise referencing to a contralateral brain volume. Read More

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http://dx.doi.org/10.1088/1361-6560/ab1442DOI Listing

Assessment of histotripsy-induced liquefaction with diagnostic ultrasound and magnetic resonance imaging in vitro and ex vivo.

Phys Med Biol 2019 Mar 28. Epub 2019 Mar 28.

Radiology, University of Chicago Pritzker School of Medicine, 5841 South Maryland Avenue, Chicago, Illinois, 60637-1470, UNITED STATES.

Histotripsy is a therapeutic ultrasound modality under development to liquefy tissue mechanically via bubble clouds. Image guidance of histotripsy requires both quantification of the bubble cloud activity and accurate delineation of the treatment zone. In this study, magnetic resonance (MR) and diagnostic ultrasound imaging were combined to assess histotripsy treatment in vitro and ex vivo. Read More

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http://dx.doi.org/10.1088/1361-6560/ab143fDOI Listing
March 2019
2.761 Impact Factor