Physics-based spectral compensation algorithm for X-ray CT with primary modulator.
Abstract 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. First, an initial spectrum of the CT...
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Gao H, Zhang L, Grimmer R, Fahrig R Tags: Phys Med Biol Source Type: research

ADMM-based deep reconstruction for limited-angle CT.
Abstract 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. To deal with the limited-angle CT reconstruction problem, the regularization method is commonly used, but it is difficult to fin...
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Wang J, Zeng L, Wang C, Guo Y Tags: Phys Med Biol Source Type: research

The potential of photon-counting CT for quantitative contrast-enhanced imaging in radiotherapy.
This study suggests that in a realistic simulation environment, the overall accuracy of radiotherapy-related parameters can be increased when using PCCT with 4 energy bins instead of DECT. This confirms the potential of PCCT to provide robust and quantitative tissue parameters for contrast-enhanced CT required in radiotherapy applications. PMID: 30999288 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 17, 2019 Category: Physics Authors: Simard M, Lapointe A, Lalonde A, Bahig H, Bouchard H Tags: Phys Med Biol Source Type: research

Localization of liver lesions in abdominal CT imaging: I. Correlation of human observer performance between anatomical and uniform backgrounds.
Conclusion: For the task of localizing low contrast liver lesions, human observer performance was highly correlated between anatomical and uniform backgrounds, suggesting that lesion localization studies emulating a clinical test of liver lesion detection can be performed using a uniform background. PMID: 30995611 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Dilger S, Yu L, Chen B, Favazza CP, Carter RE, Fletcher JG, McCollough CH, Leng S Tags: Phys Med Biol Source Type: research

ADAM phantom to test 4D medical imaging and dose delivery devices.
Abstract 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. ADAM reproduces a male torso containing realistic ribs an...
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Pallotta S, Calusi S, Masi L, Talamonti C, Marrazzo L, Foggi L, Casati M, Livi L, Simontacchi G, Desideri I, Lisci R Tags: Phys Med Biol Source Type: research

Ultrasound multiple scattering with microbubbles can differentiate between tumor and healthy tissue < i > in vivo < /i > .
Ultrasound multiple scattering with microbubbles can differentiate between tumor and healthy tissue in vivo. Phys Med Biol. 2019 Apr 17;: Authors: Mohanty K, Papadopoulou V, Newsome IG, Shelton S, Dayton PA, Muller M Abstract 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. In this work, we examine a non-invasive diffusion-based ultrasound technique to assess neo-vasculariza...
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Mohanty K, Papadopoulou V, Newsome IG, Shelton S, Dayton PA, Muller M Tags: Phys Med Biol Source Type: research

Efficient detrending of uniform images for accurate determination of the noise power spectrum at low frequencies.
Abstract 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. In this work, it is shown that the characteristics of low frequency trends can deviate from the quadratic dependence on spatial coordinates. This re...
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Gonzalez-Lopez A, Campos-Morcillo PA Tags: Phys Med Biol Source Type: research

Microwave thermal ablation using CT-scanner for predicting the variation of ablated region over time: advantages and limitations.
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. The collected image data were processed with a dedicated MATLAB tool, developed to analyse the FO positions and HU m...
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Strigari L, Minosse S, D'Alessio D, Farina L, Cavagnaro M, Cassano B, Pinto R, Vallati G, Lopresto V Tags: Phys Med Biol Source Type: research

Observation and modulation of the dissolution of histotripsy-induced bubble clouds with high-frame rate plane wave imaging.
In this study, plane wave B-mode imaging was employed to monitor bubble cloud motion and grayscale at frame rates up to 11.25 kHz. Minimal changes in the area or position of the bubble clouds were observed 50 ms post excitation. The bubble cloud grayscale was observed to decrease with the square root of time, indicating a diffusion-driven process. These results were qualitatively consistent with an analytic model of gas diffusion during the histotripsy process. Finally, the rate of bubble cloud dissolution was found to be dependent on the output of the imaging pulse, indicating an interaction between the bubble cloud and i...
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Bader KB, Hendley S, Anthony GJ, Bollen V Tags: Phys Med Biol Source Type: research

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.
Conclusion: Performance values between human observers and CHO were highly correlated as dose, reconstruction type and object size were varied for the task of localization of patient liver lesions in both uniform and liver backgrounds. PMID: 30995626 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Dilger S, Leng S, Chen B, Carter RE, Favazza CP, Fletcher JG, McCollough CH, Yu L Tags: Phys Med Biol Source Type: research

Enhanced reconstruction in magnetic particle imaging by whitening and randomized SVD approximation.
Abstract 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.e., the choice of fidelity and acceleration, and propose two algorithmic tricks, i.e., a whitening procedure to incorpo...
Source: Physics in Medicine and Biology - April 16, 2019 Category: Physics Authors: Kluth T, Jin B Tags: Phys Med Biol Source Type: research

A six-degree-of-freedom robotic motion system for quality assurance of real-time image-guided radiotherapy.
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. Four pr...
Source: Physics in Medicine and Biology - April 14, 2019 Category: Physics Authors: Alnaghy S, Kyme AZ, Caillet V, Nguyen DT, O'Brien RT, Booth JT, Keall PJ Tags: Phys Med Biol Source Type: research

Dynamic-dual-energy spectral CT for improving multi-material decomposition in image-domain.
In conclusion, our proposed dynamic-dual-energy spectral CT method is highly feasible and has a great potential in high-quality multi-material decomposition. PMID: 30986774 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 14, 2019 Category: Physics Authors: Yao Y, Li L, Chen Z Tags: Phys Med Biol Source Type: research

Backscattered electron emission after proton impact on gold nanoparticles with and without polymer shell coating.
as S Abstract 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 0.5 and 2 MeV and diameter 2.5 and 3.8 nm GNPs. The spectra were also measured for 3.8 nm GNPs after 5 and 10 MeV proton irradiations. GNPs were deposited on a 100 nm carbon film. Each experimental spectrum was compared with dedicated simulations base...
Source: Physics in Medicine and Biology - April 14, 2019 Category: Physics Authors: Hespeels F, Heuskin AC, Tabarrant T, Scifoni E, Kraemer M, Chêne G, Strivay D, Lucas S Tags: Phys Med Biol Source Type: research

Performance evaluation of a whole-body prototype PET scanner with four-layer DOI detectors.
Abstract 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. We have developed a 4-layered DOI detector, and its potential for ...
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Akamatsu G, Tashima H, Iwao Y, Wakizaka H, Maeda T, Mohammadi A, Takyu S, Nitta M, Nishikido F, Rutherford H, Chacon A, Safavi-Naeini M, Yoshida E, Yamaya T Tags: Phys Med Biol Source Type: research

Repeatability of texture features derived from magnetic resonance and computed tomography imaging and use in predictive models for non-small cell lung cancer outcome.
Conclusion: MR derived texture features may add value to predictive models and should be investigated in a larger cohort. Control analysis demonstrated that the medoid representative feature selection method may result in more robust models. . PMID: 30978707 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Mahon RN, Hugo GD, Weiss E Tags: Phys Med Biol Source Type: research

Intelligent inverse treatment planning via deep reinforcement learning, a proof-of-principle study in high dose-rate brachytherapy for cervical cancer.
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. While a treatment planning system can solve the optimization problem with given weights, adjusting the weights for high-quality plans is typically performed by human planners. Such weight-tuning task is labor intensive, time consuming, and it critically affects the final plan quality. An automatic weight-tuning approach is strongly desired. The weight-tuning procedure to improve plan quality is essentially a decision-ma...
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Shen C, Gonzalez Y, Klages P, Qin N, Jung H, Chen L, Nguyen D, Jiang SB, Jia X Tags: Phys Med Biol Source Type: research

Dual-ended readout of bismuth germanate to improve timing resolution in time-of-flight PET.
In this study, both ends of a 3 × 3 × 20 mm&lt;sup&gt;3&lt;/sup&gt; BGO crystal were coupled to NUV-HD SiPMs. Trigger time differences from the dual-ended readout of BGO were widely distributed due to detecting a mixture of prompt Cerenkov and scintillation photons on both SiPMs. When using trigger times from only a single SiPM, the estimated coincidence timing resolution between two identical BGO detectors was 463 ps FWHM and 1463 ps FWTM. In contrast, when using trigger times from both SiPMs, the estimated coincidence timing resolution was 399 ps FWHM and 936 ps FWTM with no loss of events. Ba...
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Kwon SI, Roncali E, Gola A, Paternoster G, Piemonte C, Cherry SR Tags: Phys Med Biol Source Type: research

Hybrid proton-photon inverse optimization with uniformity-regularized proton and photon target dose.
Abstract 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. To account for delivery uncertainty, proton dose is targeted at CTV using robust optimization, ...
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Gao H Tags: Phys Med Biol Source Type: research

Towards a metamaterial approach for fast timing in PET: experimental proof-of-concept.
Abstract 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. In order to move forward along this line, the standard bulk detector geometry and readout should be updat...
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Martinez Turtos R, Gundacker S, Auffray E, Lecoq P Tags: Phys Med Biol Source Type: research

Deep iterative reconstruction estimation (DIRE): approximate iterative reconstruction estimation for low dose CT imaging.
Abstract 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. Within this DIRE strategy, a 3D residual convolutional network (3D ResNet) architecture is proposed. Experiments on several simulated and real datasets as well as comparisons with state-of-the-...
Source: Physics in Medicine and Biology - April 11, 2019 Category: Physics Authors: Liu J, Zhang Y, Zhao Q, Lv T, Wu W, Cai N, Quan G, Yang W, Chen Y, Luo L, Shu H, Coatrieux JL Tags: Phys Med Biol Source Type: research

Energy dependence of a scintillating fiber detector for preclinical dosimetry with an image guided micro-irradiator.
Abstract 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. The response of the PSD relative to air kerma was measured for different beam qualities (40 to 225 kV) with the X-RAD 225Cx irradiator. The corresponding energy spectra, determi...
Source: Physics in Medicine and Biology - April 10, 2019 Category: Physics Authors: Le Deroff C, Frelin AM, Ledoux X Tags: Phys Med Biol Source Type: research

Estimation of thyroid volume from scintigraphy through 2D/3D registration of a statistical shape model.
Abstract 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. To solve this problem, this paper proposes a method which registers a 3D thyroid statistical shape model (SSM) to a single-view scintigraphy image to achieve more accurate volume estimation. The SSM was constructed based on a training set of segmented 3D CT images...
Source: Physics in Medicine and Biology - April 10, 2019 Category: Physics Authors: Wang H, Yu D, Tan Z, Hu R, Zhang B, Yu J Tags: Phys Med Biol Source Type: research

NEMA NU 4-2008 and in-vivo imaging performance of RAYCAN trans-PET/CT X5 small animal imaging system.
In conclusion, the RAYCAN Trans-PET/CT X5 system can be considered a suitable option for basic imaging needs in preclinical imaging. . PMID: 30974425 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 10, 2019 Category: Physics Authors: Teuho J, Han C, Riehakainen L, Honkaniemi A, Tirri M, Liljenbäck H, Virta J, Gu S, Liu S, Wan L, Teras M, Roivainen A, Xie Q, Knuuti J Tags: Phys Med Biol Source Type: research

Single-view cone-beam x-ray luminescence optical tomography based on Group_YALL1 method.
Abstract 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. But, when the imaging conditions become complicated (e.g., multiple adjacent nanophosphors (NPs) contained in imaged object), it is difficult to resolve each NP by the previous method. To solve the problem, we hereby pres...
Source: Physics in Medicine and Biology - April 9, 2019 Category: Physics Authors: Liu X, Tang X, Shu Y, Zhao L, Liu Y, Zhou T Tags: Phys Med Biol Source Type: research

Improving iodine contrast to noise ratio using virtual monoenergetic imaging and prior-knowledge-aware iterative denoising (mono-PKAID).
Abstract 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-...
Source: Physics in Medicine and Biology - April 9, 2019 Category: Physics Authors: Tao S, Rajendran K, Zhou W, Fletcher JG, McCollough CH, Leng S Tags: Phys Med Biol Source Type: research

Prediction of positron emitter distributions for range monitoring in carbon ion therapy: an analytical approach.
Abstract 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&lt;sup&gt;+&lt;/sup&gt;-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. Usually, this prediction is obtained from time-consuming Monte Carlo simulat...
Source: Physics in Medicine and Biology - April 9, 2019 Category: Physics Authors: Hofmann T, Fochi A, Parodi K, Pinto M Tags: Phys Med Biol Source Type: research

A GPU-based multi-criteria optimization algorithm for HDR brachytherapy.
In conclusion, two ultra-fast and robust multi-criteria optimization algorithms were implemented for HDR prostate brachytherapy. A large-scale comparison against physician approved clinical plans showed that treatment plan quality could be improved and plan generation time could be significantly reduced with the proposed GPU-based MCO algorithms. PMID: 30970341 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 9, 2019 Category: Physics Authors: Bélanger C, Cui S, Ma Y, Després P, Cunha A, Beaulieu L Tags: Phys Med Biol Source Type: research

Data acquisition system for MAET with magnetic field measurements.
ncer NG Abstract 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. The static magnetic field is generated by six permanent neodymium magnets. A 16-element linear phased array (LPA) transducer is utilized to generate acoustic pressure waves inside the phantom. To measure the magnetic field intensity generated by the induced currents, cont...
Source: Physics in Medicine and Biology - April 9, 2019 Category: Physics Authors: Kaboutari K, Onder Tetik A, Ghalichi E, Gözü MS, Zengin R, Gencer NG Tags: Phys Med Biol Source Type: research

Characterization of a novel 3D printed patient specific phantom for quality assurance in cranial stereotactic radiosurgery applications.
Abstract 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. The resulting head phantom was fille...
Source: Physics in Medicine and Biology - April 8, 2019 Category: Physics Authors: Makris DN, Pappas EP, Zoros E, Papanikolaou N, Saenz DL, Kalaitzakis G, Zourari K, Efstathopoulos EP, Maris TG, Pappas E Tags: Phys Med Biol Source Type: research

Principal component analysis for fast and model-free denoising of multi b-value diffusion-weighted MR images.
Conclusions: Multi-b-value MRI can be denoised model-free with our PCA-denoising strategy that reduces noise to a level similar to synthetic MRI, but without introducing systematic errors associated with the synthetic MRI method. PMID: 30965296 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 8, 2019 Category: Physics Authors: Gurney-Champion OJ, Collins DJ, Wetscherek A, Rata M, Klaassen R, van Laarhoven HWM, Harrington KJ, Oelfke U, Orton MR Tags: Phys Med Biol Source Type: research

Modeling the DQE(f) of photon-counting detectors: impact of the pixel sensitivity profile.
Conclusion: The phenomenon of the pixel sensitivity profile, i.e. the fact that the choice of the threshold is affecting the detector sharpness, may play a substantial role in exploiting the full potential of photon counting detectors. The model compares well with measurements: with only two model parameters, the model can predict the MTF(f) and the DQE(f) for a wide range of thresholds. . PMID: 30965298 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 8, 2019 Category: Physics Authors: Stierstorfer K, Hupfer M, Koester N Tags: Phys Med Biol Source Type: research

Processing of prompt gamma-ray timing data for proton range measurements at a clinical beam delivery.
Pausch G Abstract 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. To overcome this obstacle, different methods are under investigation aiming at the verification of the proton range in real time. One approach is the Prompt Gamma-ray Timing (PGT) method, where the range of the primary protons is derived from the...
Source: Physics in Medicine and Biology - April 8, 2019 Category: Physics Authors: Werner T, Berthold J, Hueso-González F, Kögler T, Petzoldt J, Roemer KE, Richter C, Rinscheid A, Straessner A, Enghardt W, Pausch G Tags: Phys Med Biol Source Type: research

Sentinel lymph node fingerprinting.
Conclusions - These promising results under short exposure time are very encouraging for SLN biopsy. Although, this device has not been tested on patients yet, we believe: that this approach will give the surgeon accurate 3D positions of the SLN and hence, can potentially reduce the trauma for the patient. PMID: 30965313 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 8, 2019 Category: Physics Authors: Nahum U, Seppi C, von Niederhäusern PA, Pezold S, Haerle SK, Cattin PC Tags: Phys Med Biol Source Type: research

A detector's eye view (DEV)-based OSEM algorithm for benchtop x-ray fluorescence computed tomography (XFCT) image reconstruction.
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 i...
Source: Physics in Medicine and Biology - April 7, 2019 Category: Physics Authors: Deng L, Ahmed MF, Jayarathna S, Feng P, Wei B, Cho SH Tags: Phys Med Biol Source Type: research

Normalized glandular dose (DgN) coefficients from experimental mammographic x-ray spectra.
In conclusion, polyenergetic x-ray spectrometry proved to be an applicable tool for research in dosimetry in mammography allowing spectral characterization. This approach can also be useful for investigation of the influence of x-ray spectra on glandular dose. PMID: 30959490 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 7, 2019 Category: Physics Authors: Santos JC, Tomal A, de Barros N, Costa PR Tags: Phys Med Biol Source Type: research

Stereotactic Body Radiotherapy for Localized Prostate Cancer: A Systematic Review and Meta-Analysis of Over 6,000 Patients Treated On Prospective Studies.
CONCLUSIONS: Prostate SBRT has substantial prospective evidence supporting its use, with favorable tumor control, patient-reported QOL, and toxicity demonstrated. SBRT has sufficient evidence to be supported as a standard treatment option for localized prostate cancer, while ongoing trials assess its potential superiority. PMID: 30959121 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 4, 2019 Category: Physics Authors: Jackson WC, Silva J, Hartman HE, Dess RT, Kishan AU, Beeler WH, Gharzai LA, Jaworski EM, Mehra R, Hearn JWD, Morgan TM, Salami SS, Cooperberg MR, Mahal BA, Soni PD, Kaffenberger S, Nguyen PL, Desai N, Feng FY, Zumsteg ZS, Spratt DE Tags: Int J Radiat Oncol Biol Phys Source Type: research

Temperature dependence of thermal properties of < i > ex-vivo < /i > liver tissue up to ablative temperatures.
Temperature dependence of thermal properties of ex-vivo liver tissue up to ablative temperatures. Phys Med Biol. 2019 Apr 05;: Authors: Lopresto V, Argentieri A, Pinto R, Cavagnaro M Abstract 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...
Source: Physics in Medicine and Biology - April 4, 2019 Category: Physics Authors: Lopresto V, Argentieri A, Pinto R, Cavagnaro M Tags: Phys Med Biol Source Type: research

Guaranteed [Formula: see text]-optimal solutions with the linear optimizer ART3+O.
Abstract 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. Its major weakness is that it cannot guarantee [Formula: see text]-optimality of the final solution due to an arbitrary stopping criterion. We propose an improvement to ART3+O where the stopping criterion is based on Farkas' lemma. The same theory can be used to detect inconsistency in other projection methods as well. The proposed algorithm guarantees to find an [Formula: see text]-optimal solut...
Source: Physics in Medicine and Biology - April 3, 2019 Category: Physics Authors: Gorissen BL Tags: Phys Med Biol Source Type: research

Performance of a dual-layer scanner for hybrid SPECT/CBCT.
Conclusion A dual-layer detector is able to simultaneously acquire SPECT and CBCT. Both CNR and T/N ratio are worse than that of a clinical system, but the phantom experiments showed that extrahepatic depositions with volumes and activities close to the median values encountered in hepatic radioembolization could be distinguished. PMID: 30947146 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 3, 2019 Category: Physics Authors: Dietze MMA, Kunnen B, van der Velden S, Steenbergen LJH, Koppert WJC, Viergever MA, de Jong HWAM Tags: Phys Med Biol Source Type: research

A hybrid proton and hyperpolarized gas tagging MRI technique for lung respiratory motion imaging: the feasibility study.
Conclusion: These preliminary results showed that the hybrid HP gas tagging MRI technique revealed different lung motion patterns as compared to the DIR methods. It may provide unique perspectives in developing and evaluating DIR of the lungs. PMID: 30947154 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 3, 2019 Category: Physics Authors: Hu L, Huang Q, Cui T, Duarte I, Miller W, Mugler JP, Cates GD, Mata JF, de Lange EE, Altes TA, Yin FF, Cai J Tags: Phys Med Biol Source Type: research

NEMA NU-4 performance evaluation of a non-human primate animal PET.
This article presents a performance evaluation of the PET scanner according to the National Electrical Manufacturers Association NU-4 2008 standards. All measurements were made for an energy window of 360~660 keV and a coincidence timing window of 2 ns. In terms of the FWHM, the FBP reconstructed spatial resolution results in all three directions at the radial position of 5 mm were better than or approached to 2 mm, and remained below 3.0 mm within the central 5 cm diameter of the FOV. The peak absolute sensitivity of the scanner was measured 1.80%. For a monkey-sized phantom, the scatter fraction was 34.2% and the peak no...
Source: Physics in Medicine and Biology - April 3, 2019 Category: Physics Authors: Chai P, Feng B, Zhang Z, Tang H, Liu S, Sun X, Wang P, Wang X, Zhao X, Wei L Tags: Phys Med Biol Source Type: research

Evaluation of pinhole collimator materials for micron-resolution < i > ex-vivo < /i > SPECT.
Evaluation of pinhole collimator materials for micron-resolution ex-vivo SPECT. Phys Med Biol. 2019 Apr 04;: Authors: Nguyen MP, Goorden MC, Kamphuis C, Beekman FJ Abstract 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.) based on a highly focusing multi-pinhole collimator achieves micron-resolution SPECT for cryo-cooled tissue samples. For such high resolutions, the choice of pinhole material may have a significant impact on images. Therefore, this p...
Source: Physics in Medicine and Biology - April 3, 2019 Category: Physics Authors: Nguyen MP, Goorden MC, Kamphuis C, Beekman FJ Tags: Phys Med Biol Source Type: research

MRI artifact simulation for clinically relevant MRI sequences for guidance of prostate HDR brachytherapy.
This study demonstrated that the MRI artifact induced by an HDR source or a titanium needle could be simulated for the four investigated types of MRI sequences (spoiled gradient echo, spin echo, bSSFP and bSSFP-SPAIR), valuable for real-time object localization in clinical practice. This leads to more flexibility in the choice of MRI sequences for guidance of HDR brachytherapy, as they are suitable for both object localization and anatomy visualization. PMID: 30947159 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 3, 2019 Category: Physics Authors: Beld E, Moerland MA, van der Voort van Zyp JRN, Viergever MA, Lagendijk JJW, Seevinck PR Tags: Phys Med Biol Source Type: research

Dynamic fluence field modulation in computed tomography using multiple aperture devices.
Abstract 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. The dual-MAD filter can be designed to achieve specific classes of target profiles. The designed filter was manufactured through a laser-sintering process and integrated to an experimental imaging system that enables linear actuatio...
Source: Physics in Medicine and Biology - April 1, 2019 Category: Physics Authors: Gang GJ, Mao A, Wang W, Siewerdsen JH, Mathews A, Kawamoto S, Levinson R, Stayman JW Tags: Phys Med Biol Source Type: research

A study of inter-crystal scatter in dual-layer offset scintillator arrays for brain-dedicated PET scanners.
Abstract 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. The influence of layer misidentification on the coincidence response functions (CRFs) of 3 different DLO detectors with ...
Source: Physics in Medicine and Biology - March 31, 2019 Category: Physics Authors: Teimoorisichani M, Goertzen AL Tags: Phys Med Biol Source Type: research

Direct measurement of ion chamber correction factors, < i > k < /i > < sub > Q < /sub > and < i > k < sub > B < /sub > < /i > , in a 7 MV MRI-linac.
In this study, for the first time, both &lt;i&gt;k&lt;/i&gt;&lt;sub&gt;Q&lt;/sub&gt; and &lt;i&gt;k&lt;sub&gt;B&lt;/i&gt;&lt;/sub&gt; were measured directly for 6 waterproof ion chambers (3 × PTW 30013 and 3 × IBA FC65-G) in a pre-clinical 7 MV MRI-linac at 0 T and at 1.5 T. Measurements were done with the only available primary standard build for this purpose, a water calorimeter. Resulting &lt;i&gt;k&lt;/i&gt;&lt;sub&gt;Q&lt;/sub&gt; factors for PTW and IBA chambers were respectively 0.985(5) and 0.990(4). &lt;...
Source: Physics in Medicine and Biology - March 31, 2019 Category: Physics Authors: de Prez LA, Woodings SJ, de Pooter JA, van Asselen B, Wolthaus JWH, Jansen BJ, Raaymakers BW Tags: Phys Med Biol Source Type: research

Correlations between the shifts in prompt gamma emission profiles and the changes in daily target coverage during simulated pencil beam scanning proton therapy.
Abstract The aim of this study was to investigate the feasibility of using prompt gamma (PG) ray emission profiles to monitor changes in dose to the planning target volume (PTV) during pencil beam scanning (PBS) proton therapy as a result of day-to-day variation in patient anatomy. For 11 prostate patients, we simulated treatment plan delivery using the patients' daily anatomy as observed in the planning CT and 7-9 control CT scans, including the detected PG profiles resulting from the 5%, 10%, and 20% most intense proton pencil beams. For each patient, we determined the changes in dosimetric parameters for t...
Source: Physics in Medicine and Biology - March 27, 2019 Category: Physics Authors: Lens E, Jagt TZ, Hoogeman MS, Schaart DR Tags: Phys Med Biol Source Type: research

Impact of setup and range uncertainties on TCP and NTCP following VMAT or IMPT of oropharyngeal cancer patients.
Conclusion: The estimated population impact of setup and range uncertainties on TCP/NTCP following VMAT or IMPT of oropharyngeal cancer patients was small for both treatment modalities. The use of TCP/NTCP models allows for clinical interpretation of the population effect and could be considered for incorporation in robust evaluation methods. . PMID: 30921775 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - March 27, 2019 Category: Physics Authors: Hamming-Vrieze O, Depauw N, Craft DL, Chan AW, Rasch CRN, Verheij M, Sonke JJ, Kooy HM Tags: Phys Med Biol Source Type: research

Characterization of GE discovery IGS 740 angiography system by means of channelized hotelling observer (CHO).
Abstract The aim of the study is to use the well-known Channelized Hotelling Observer model (CHO) to characterize a recently installed angiography system (GE Discovery IGS 740) using sets of images of a contrast-detail phantom acquired with clinical protocols. A Leeds TO10 phantom was used. The phantom has 108 details: 12 diameters (size range: 0.25 mm - 11 mm), each with 9 contrasts (declared range: 0.012 - 0.930 at 70 kVp 1.00 with 1 mm Cu filtration). TO10 has been imaged between two 10 cm thick homogeneous solid water slabs. Two FOVs (32 cm and 20 cm) were used. Fluoroscopy images were taken using an abdominal...
Source: Physics in Medicine and Biology - March 27, 2019 Category: Physics Authors: Bertolini M, Trojani V, Nitrosi A, Iori M, Sassatelli R, Ortenzia O, Ghetti C Tags: Phys Med Biol Source Type: research