Quantitative myocardial perfusion from static cardiac and dynamic arterial CT.
Abstract Quantitative myocardial blood flow (MBF) estimation by dynamic contrast enhanced cardiac computed tomography (CT) requires multi-frame acquisition of contrast transit through the blood pool and myocardium to inform the arterial input and tissue response functions. Both the input and the tissue response functions for the entire myocardium are sampled with each acquisition. However, the long breath holds and frequent sampling can result in significant motion artifacts and relatively high radiation dose. To address these limitations, we propose and evaluate a new static cardiac and dynamic arterial (SCDA) qu...
Source: Physics in Medicine and Biology - April 27, 2018 Category: Physics Authors: Bindschadler M, Branch KR, Alessio AM Tags: Phys Med Biol Source Type: research

Incorporating drug delivery into an imaging-driven, mechanics-coupled reaction diffusion model for predicting the response of breast cancer to neoadjuvant chemotherapy: theory and preliminary clinical results.
This study demonstrates the plausibility of using DCE-MRI data as a means to estimate drug delivery on a patient-specific basis in predictive models and represents a step toward the goal of achieving individualized prediction of tumor response to therapy. PMID: 29697054 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2018 Category: Physics Authors: Jarrett AM, Hormuth Ii DA, Barnes SL, Feng X, Huang W, Yankeelov TE Tags: Phys Med Biol Source Type: research

Monte Carlo simulation of chemistry following radiolysis with TOPAS-nBio.
In conclusion, radiolysis and subsequent chemistry with Geant4-DNA has been successfully incorporated in TOPAS-nBio. Results are in reasonable agreement with published measured and simulated data. PMID: 29697057 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2018 Category: Physics Authors: Ramos-Mendez JA, Perl J, Schuemann J, McNamara AL, Paganetti H, Faddegon BA Tags: Phys Med Biol Source Type: research

Toward minimizing annotation work: Diagnosis of mammographic masses via active learning.
Conclusions: By taking the particularities of mammographic images, the proposed AL method can indeed reduce the manual annotation work to a great extent without sacrificing performance of prediction system for mammographic diagnosis. . PMID: 29697059 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2018 Category: Physics Authors: Zhao Y, Zhang J, Xie H, Zhang S, Gu L Tags: Phys Med Biol Source Type: research

A combined positron emission tomography (PET)- electron paramagnetic resonance imaging (EPRI) system: initial evaluation of a prototype scanner.
Abstract The advent of hybrid scanners, combining complementary modalities, has revolutionized imaging; enhancing clinical practice and biomedical research. In this project, we investigated the melding of two complementary, functional imaging methods: positron emission tomography (PET) and electron paramagnetic resonance imaging (EPRI). The PET radiotracers can provide important information about cellular parameters, such as glucose metabolism. While EPR probes can provide assessment of tissue microenvironment, measuring parameters such as oxygenation and pH, for example. A combined PET/EPRI scanner has the promis...
Source: Physics in Medicine and Biology - April 20, 2018 Category: Physics Authors: Tseytlin M, Stolin AV, Guggilapu P, Bobko AA, Khramtsov VV, Tseytlin O, Raylman RR Tags: Phys Med Biol Source Type: research

Comparison of fan beam, slit-slat and multi-pinhole collimators for molecular breast tomosynthesis.
Abstract Recently, we proposed and optimized dedicated multi-pinhole molecular breast tomosynthesis (MBT) that images a lightly compressed breast. As MBT may also be performed with other types of collimators, the aim of this paper is to optimize MBT with fan beam and slit-slat collimators and to compare its performance to that of multi-pinhole MBT to arrive at a truly optimized design. Using analytical expressions, we first optimized fan beam and slit-slat collimator parameters to reach maximum sensitivity at a series of given system resolutions. Additionally, we performed full system simulations of a breast phant...
Source: Physics in Medicine and Biology - April 20, 2018 Category: Physics Authors: van Roosmalen J, Beekman FJ, Goorden MC Tags: Phys Med Biol Source Type: research

Automated human skull landmarking with 2D gabor wavelets.
We present a novel method for automatically locating anatomical landmarks on the surface of cone beam CT-based image models of human skulls using 2D Gabor wavelets and ensemble learning. The algorithm is validated via human inter- and intra-rater comparisons on a set of 39 scans and a skull superimposition experiment with an established surgery planning software (Maxilim). Automatic landmarking results in an accuracy of 1-2 mm for a subset of landmarks around the nose area as compared to a gold standard derived from human raters. These landmarks are located in eye sockets and lower jaw, and is competitive with or surpasses...
Source: Physics in Medicine and Biology - April 20, 2018 Category: Physics Authors: de Jong MA, Gül A, de Gijt JP, Koudstaal MJ, Kayser M, Wolvius EB, Böhringer S Tags: Phys Med Biol Source Type: research

Motion induced interplay effects for VMAT radiotherapy.
In conclusion, a method to simulate motion induced interplay effects was developed and verified with measurements, which allowed for a large number of treatment scenarios to be investigated. The simulations showed large interplay effects for individual fractions and that the extent of interplay effects varied with the breathing pattern, FFF/FF, dose level, CTV size, collimator angle, and the complexity of the treatment plan. PMID: 29671410 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 19, 2018 Category: Physics Authors: Edvardsson A, Nordström F, Ceberg C, Ceberg S Tags: Phys Med Biol Source Type: research

A random phased-array for MR-guided transcranial ultrasound neuromodulation in non-human primates.
Abstract Transcranial focused ultrasound (FUS) is a non-invasive technique for therapy and study of brain neural activation. Here we report on the design and characterization of a new MR-guided FUS transducer for neuromodulation in non-human primates at 650 kHz. The array is randomized with 128 elements 6.6 mm in diameter, radius of curvature 7.2 cm, opening diameter 10.3 cm (focal ratio 0.7), and 46% coverage. Simulations were used to optimize transducer geometry with respect to focus size, grating lobes, and directivity. Focus size and grating lobes during electronic steering were quantified using hydrophone mea...
Source: Physics in Medicine and Biology - April 18, 2018 Category: Physics Authors: Chaplin V, Phipps MA, Caskey CF Tags: Phys Med Biol Source Type: research

Applying a new computer-aided detection scheme generated imaging marker to predict short-term breast cancer risk.
This study aims to investigate the feasibility of identifying a new quantitative imaging marker based on false-positives generated by computer-aided detection (CAD) scheme to help predict short-term breast cancer risk. An image dataset including four view mammograms acquired from 1,044 women was retrospectively assembled. All mammograms were originally interpreted as negative by radiologists. In the next subsequent mammography screening, 402 women were diagnosed with breast cancer and 642 remained negative. An existing CAD scheme was applied "as is" to process each image. From CAD-generated results, 4 detection f...
Source: Physics in Medicine and Biology - April 18, 2018 Category: Physics Authors: Mirniaharikandehei S, Hollingsworth AB, Patel B, Heidari M, Liu H, Zheng B Tags: Phys Med Biol Source Type: research

A CBCT study of the gravity-induced movement in rotating rabbits.
Abstract Fixed-beam radiotherapy systems with subjects rotating about a longitudinal (horizontal) axis are subject to gravity-induced motion. Limited reports on the degree of this motion, and any deformation, has been reported previously. The purpose of this study is to quantify the degree of anatomical motion caused by rotating a subject around a longitudinal axis, using cone-beam CT (CBCT). In the current study, a purpose-made longitudinal rotating was aligned to a Varian TrueBeam kV imaging system. CBCT images of three live rabbits were acquired at fixed rotational offsets of the cradle. Rigid and d...
Source: Physics in Medicine and Biology - April 18, 2018 Category: Physics Authors: Barber J, Shieh CC, Counter W, Sykes JR, Bennett P, Ahern V, Corde S, Heng SM, White P, Jackson M, Liu P, Keall PJ, Feain I Tags: Phys Med Biol Source Type: research

Time-of-flight PET time calibration using data consistency.
Abstract This paper presents new data driven methods for the time of flight (TOF) calibration of positron emission tomography (PET) scanners. These methods are derived from the consistency condition for TOF PET, they can be applied to data measured with an arbitrary tracer distribution and are numerically efficient because they do not require a preliminary image reconstruction from the non-TOF data. Two-dimensional simulations are presented for one of the methods, which only involves the two first moments of the data with respect to the TOF variable. The numerical results show that this method estimate...
Source: Physics in Medicine and Biology - April 17, 2018 Category: Physics Authors: Defrise M, Rezaei A, Nuyts J Tags: Phys Med Biol Source Type: research

GPU-based Green's function simulations of shear waves generated by an applied acoustic radiation force in elastic and viscoelastic models.
Abstract Shear wave calculations induced by an acoustic radiation force are very time-consuming on desktop computers, and high-performance graphics processing units (GPUs) achieve dramatic reductions in the computation time for these simulations. The acoustic radiation force is calculated using the fast near field method (FNM) and the angular spectrum approach (ASA), and then the shear waves are calculated in parallel with Green's functions on a GPU. This combination enables rapid evaluation of shear waves for push beams with different spatial samplings and for apertures with different f/#. Relative to shear wave ...
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Yang Y, Urban MW, McGough RJ Tags: Phys Med Biol Source Type: research

Novel inter-crystal scattering event identification method for PET detectors.
In conclusion, our proposed method showed good ICS identification in both 1-to-1 coupling and light sharing detectors. We experimentally validated that ICS recovery based on the proposed identification method led to improved resolution. . PMID: 29658493 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Lee MS, Kang SK, Lee JS Tags: Phys Med Biol Source Type: research

Multi-resolution simulation of focused ultrasound propagation through ovine skull from a single-element transducer.
Abstract Transcranial focused ultrasound (tFUS) is emerging as a non-invasive brain stimulation modality. Complicated interactions between acoustic pressure waves and osseous tissue introduce many challenges in the accurate targeting of an acoustic focus through the cranium. Image-guidance accompanied by a numerical simulation is desired to predict the intracranial acoustic propagation through the skull; however, such simulations typically demand sophisticated computation, which warrants an expedited processing method to provide on-site feedback for the user in guiding the acoustic focus to a particular brain regi...
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Yoon K, Lee W, Croce P, Cammalleri A, Yoo SS Tags: Phys Med Biol Source Type: research

Cross-correlation analysis of pulse wave propagation in arteries: < i > in vitro < /i > validation and < i > in vivo < /i > feasibility.
Cross-correlation analysis of pulse wave propagation in arteries: in vitro validation and in vivo feasibility. Phys Med Biol. 2018 Apr 16;: Authors: Nauleau P, Apostolakis IZ, McGarry M, Konofagou EE Abstract The stiffness of the arteries is known to be an indicator of the progression of various cardiovascular diseases. Clinically, the pulse wave velocity (PWV) is used as a surrogate for the arterial stiffness. Pulse Wave Imaging (PWI) is a non-invasive, ultrasound-based imaging technique capable of mapping the motion of the vessel walls allowing local assessment of the arterial properties. Convention...
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Nauleau P, Apostolakis IZ, McGarry M, Konofagou EE Tags: Phys Med Biol Source Type: research

Multi-layer imager design for mega-voltage spectral imaging.
Abstract The architecture of multi-layer imagers (MLIs) can be exploited to provide megavoltage spectral imaging (MVSPI) for specific imaging tasks. In the current work, we investigated bone suppression and gold fiducial contrast enhancement as two clinical tasks which could be improved with spectral imaging. A method based on analytical calculations that enables rapid investigation of MLI component materials and thicknesses was developed and validated against Monte Carlo computations. The figure of merit for task-specific imaging performance was the contrast-to-noise ratio (CNR) of the gold fiducial when the CNR ...
Source: Physics in Medicine and Biology - April 13, 2018 Category: Physics Authors: Myronakis ME, Hu YH, Fueglistaller R, Wang A, Baturin P, Huber P, Morf D, Star-Lack JM, Berbeco RI Tags: Phys Med Biol Source Type: research

Design of a QA method to characterize submillimeter-sized PBS beam properties using a two-dimensional ionization chamber array.
Abstract Pencil beam scanning (PBS) periodic quality assurance (QA) programs ensure the beam delivered to patients is within technical specifications. Two critical specifications for PBS delivery are the beam width and position. The aim of this study is to investigate whether a 2-dimensional ionization chamber array, such as the MatriXX detector (IBA Dosimetry, Schwarzenbruck, Germany), can be used to characterize submillimeter-sized PBS beam properties. The motivation is to use standard equipment, which may have pixel spacing coarser than the pencil beam size, and simplify QA workflow. The MatriXX pixels ar...
Source: Physics in Medicine and Biology - April 12, 2018 Category: Physics Authors: Lin Y, Bentefour EH, Flanz JB, Kooy HM, Clasie BM Tags: Phys Med Biol Source Type: research

Markerless motion estimation for motion-compensated clinical brain imaging.
Abstract Motion-compensated brain imaging can dramatically reduce the artifacts and quantitative degradation associated with voluntary and involuntary subject head motion during positron emission tomography (PET), single photon emission computed tomography (SPECT) and computed tomography (CT). However, motion-compensated imaging protocols are not in widespread clinical use for these modalities. A key reason for this seems to be the lack of a practical motion tracking technology allowing for smooth and reliable integration of motion-compensated imaging protocols in the clinical setting. We address this problem by i...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Kyme AZ, Se S, Meikle SR, Fulton RR Tags: Phys Med Biol Source Type: research

Dosimetric characteristics of the University of Washington clinical neutron therapy system.
Abstract The University of Washington (UW) Clinical Neutron Therapy System (CNTS), which generates high linear energy transfer (LET) fast neutrons through interactions of 50.5 MeV protons incident on a Be target, has depth-dose characteristics similar to 6 MV x-rays. In contrast to the fixed beam angles and primitive blocking used in early clinical trials of neutron therapy, the CNTS has a gantry with a full 360&lt;sup&gt;○&lt;/sup&gt; of rotation, internal wedges, and a multi-leaf collimator (MLC). Since October of 1984, over 3,178 patients have received conformal neutron therapy treatments usin...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Moffitt GB, Stewart RD, Sandison GA, Goorley JT, Argento DC, Jevremovic T, Emery R, Wootton LS, Parvathaneni U, Laramore GE Tags: Phys Med Biol Source Type: research

Realistic modeling of deep brain stimulation implants for electromagnetic MRI safety studies.
Abstract We propose a framework for electromagnetic (EM) simulation of deep brain stimulation (DBS) patients in radiofrequency (RF) coils. We generated a model of a DBS patient using post-operative head and neck computed tomography (CT) images stitched together into a "virtual CT" image covering the entire length of the implant. The body was modeled as homogeneous. The implant path extracted from the CT data contained self-intersections, which we corrected automatically using an optimization procedure. Using the CT-derived DBS path, we built a model of the implant including electrodes, helicoidal interna...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Guerin B, Serano P, Iacono MI, Herrington TM, Widge AS, Dougherty DD, Bonmassar G, Angelone LM, Wald LL Tags: Phys Med Biol Source Type: research

Lesion detectability in 2D-mammography and digital breast tomosynthesis using different targets and observers.
Abstract This work investigates the detection performance of specialist and non-specialist observers for different targets in 2D-mammography and digital breast tomosynthesis (DBT) using the OPTIMAM Virtual Clinical Trials (VCT) Toolbox and a 4-alternative forced choice (4AFC) assessment paradigm. Using 2D-mammography and DBT images of virtual breast phantoms, we compare the detection limits of simple uniform spherical targets and irregular solid masses. Target diameters of 4mm and 6mm have been chosen to represent target sizes close to the minimum detectable size found in breast screening, across a rang...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Elangovan P, Mackenzie A, Dance DR, Young KC, Wells K Tags: Phys Med Biol Source Type: research

Stable gelatin-based phantom materials with tunable x-ray attenuation properties and 3D printability for x-ray imaging.
We report a novel method for developing gelatin-based phantom materials for transmission x-ray imaging with high stability at room temperature and tunable x-ray attenuation properties. This is achieved by efficiently cross-linking gelatin in a glycerin solution with only 10% water by volume and systematically decreasing their x-ray attenuation coefficients by doping with microbubbles that are originally designed to be used as lightweight additives for paints and crack fillers. For demonstration, we mimic breast glandular and adipose tissues by using such gelatin materials and also study the feasibility of 3D printing ...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Dahal E, Badal A, Zidan A, Alayoubi A, Hagio T, Glick SJ, Badano A, Ghammraoui B Tags: Phys Med Biol Source Type: research

Multi-threading performance of Geant4, MCNP6, and PHITS Monte Carlo codes for tetrahedral-mesh geometry.
Abstract In the present study, the multi-threading performances of the Geant4, MCNP6, and PHITS codes were evaluated as a function of the number of the threads (N) and the complexity of the tetrahedral-mesh phantom. For this, three tetrahedral-mesh phantoms with different complexity (simple, moderately complex, and highly complex) were prepared and implemented in three different Monte Carlo codes, carrying out photon and neutron transport simulations. Subsequently, for each case, the initialization time, calculation time, and memory usage were measured as a function of the number of threads used in the simulation....
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Han MC, Yeom YS, Lee HS, Shin B, Kim CH, Furuta T Tags: Phys Med Biol Source Type: research

Inverse optimization of objective function weights for treatment planning using clinical dose-volume histograms.
Abstract We developed and evaluated a novel inverse optimization (IO) model to estimate objective function weights from clinical dose-volume histograms (DVHs). These weights were used to solve a treatment planning problem to generate "inverse plans" that had similar DVHs to the original clinical DVHs. Our methodology was applied to 217 clinical head and neck cancer treatment plans that were previously delivered at Princess Margaret Cancer Centre in Canada. Inverse plan DVHs were compared to the clinical DVHs using objective function values, dose-volume differences, and frequency of clinical planning crit...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Babier A, Boutilier JJ, Sharpe MB, McNiven AL, Chan TCY Tags: Phys Med Biol Source Type: research

MR-ARFI-based method for quantitative measurement of tissue elasticity: application to monitoring of HIFU therapy.
Abstract Monitoring thermal therapies thanks to medical imaging is essential in order to ensure that they are safe, efficient and reliable. In this paper, we propose a new approach, halfway between MR Acoustic Radiation Force Imaging (MR-ARFI) and MR Elastography (MRE), allowing for quantitative measurement of tissue's elastic modulus in a highly localized manner. It relies on the simulation of the MR-ARFI profile, which depends on tissue biomechanical properties, and on the identification of tissue elasticity through the fitting of the experimental displacement images measured using rapid MR-ARFI. Such method was...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Vappou J, Bour P, Marquet F, Ozenne V, Quesson BAJ Tags: Phys Med Biol Source Type: research

Superpixel-based and boundary-sensitive convolutional neural network for automated liver segmentation.
Conclusion: SBBS-CNN provides an accurate and effective tool for automated liver segmentation. It is also envisioned that the proposed framework is directly applicable in other medical image segmentation scenarios. . PMID: 29633960 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Qin W, Wu J, Han F, Yuan Y, Zhao W, Ibragimov B, Gu J, Xing L Tags: Phys Med Biol Source Type: research

Computation of reliable textural indices from multimodal brain MRI: suggestions based on a study of patients with diffuse intrinsic pontine glioma.
Abstract Few methodological studies regarding widely used textural indices robustness in MRI have been reported. In this context, this study aims at proposing some rules to compute reliable textural indices from multimodal 3D brain MRI. Diagnosis and post-biopsy MR scans including T1, post-contrast T1, T2 and FLAIR images from thirty children with diffuse intrinsic pontine glioma (DIPG) were considered. The Hybrid White Stripe method was adapted to standardize MR intensities. Sixty textural indices were then computed for each modality in different regions of interest, including tumor and white matter (WM). Three t...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Goya-Outi J, Orlhac F, Calmon R, Alentorn A, Nioche C, Philippe C, Puget S, Boddaert N, Buvat I, Grill J, Frouin V, Frouin F Tags: Phys Med Biol Source Type: research

Characterization of the exradin W1 plastic scintillation detector for small field applications in proton therapy.
This study examines the dosimetric performance of the W1 in a 74 MeV proton therapy beam with particular focus on detector response characteristics relevant to relative dose measurement in small fields suitable for ocular therapy. Quenching of the scintillation signal is characterized and demonstrated not to impede relative dose measurements at a fixed depth. The background cable-only (Čerenkov and radio-fluorescence) signal is 4 orders of magnitude less than the scintillation signal, greatly simplifying relative dose measurements. Comparison with other detectors and Monte Carlo simulations indicate that the W1 is useful ...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Hoehr C, Lindsay C, Beaudry J, Penner C, Strgar V, Lee R, Duzenli C Tags: Phys Med Biol Source Type: research

Tetrazolium salts-Pluronic F-127 gels for 3D radiotherapy dosimetry.
Abstract This work is a follow-up study for a recently-proposed 3D radiochromic gel dosimeter that contains a tetrazolium salt and a physical gel matrix made of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127). Several tetrazolium salts were examined in this work, including tetrazolium violet (TV), blue tetrazolium chloride (BT), nitro blue tetrazolium chloride (NBT), tetranitro blue tetrazolium chloride (tNBT) and thiazolyl blue tetrazolium bromide (TBTB). The salt-containing gel dosimeters were compared with the first Pluronic gel composition that contained 2,3,5-triph...
Source: Physics in Medicine and Biology - April 5, 2018 Category: Physics Authors: Kwiatos K, Maras P, Kadlubowski S, Stempień Z, Dudek M, Kozicki M Tags: Phys Med Biol Source Type: research

Introduction of a hybrid treatment delivery system used for quality assurance in multi-catheter interstitial brachytherapy.
Abstract Multi-catheter interstitial brachytherapy (iBT) is a treatment option for breast cancer patients after breast conserving surgery. Typically, only a few additional quality interventions after the first irradiation have been introduced to ensure the planned treatment delivery. Therefore, the purpose of this study is to show the possibilities of an electromagnetic tracking (EMT) system integrated into the afterloader for quality assurance (QA) in high-dose rate (HDR) iBT of patients with breast cancer. The hybrid afterloader system equipped with an electromagnetic sensor was used for all phantom and pa...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Kallis K, Kreppner S, Lotter M, Strnad V, Fietkau R, Bert C Tags: Phys Med Biol Source Type: research

Evolutionary pruning of transfer learned deep convolutional neural network for breast cancer diagnosis in digital breast tomosynthesis.
The objective is to prune the number of tunable parameters while preserving the classification accuracy. In the first stage transfer learning, 19,632 augmented regions-of-interest (ROIs) from 2,454 mass lesions on mammograms were used to train a pre-trained DCNN on ImageNet. In the second stage transfer learning, the DCNN was used as a feature extractor followed by feature selection and random forest classification. The pathway evolution was performed using genetic algorithm in an iterative approach with tournament selection driven by count-preserving crossover and mutation. The second stage was trained with 9,120 DBT ROIs...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Samala RK, Chan HP, Hadjiiski LM, Helvie MA, Richter C, Cha K Tags: Phys Med Biol Source Type: research

Shell feature: a new radiomics descriptor for predicting distant failure after radiotherapy in non-small cell lung cancer and cervix cancer.
Abstract Distant failure is the main cause for human cancer-related mortalities. To develop a model for predicting distant failure in non-small cell lung cancer (NSCLC) and cervix caner (CC) patients, a shell feature, consisting of outer voxels around the tumor boundary, was constructed using pre-treatment positron emission tomography (PET) images from 48 NSCLC patients received stereotactic body radiation therapy (SBRT) and 52 CC patients underwent external beam radiation therapy and concurrent chemotherapy followed with high-dose-rate intracavitary brachytherapy. The hypothesis behind this feature is that non-in...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Hao H, Zhou Z, Li S, Maquilan G, Folkert MR, Iyengar P, Westover KD, Albuquerque K, Liu F, Choy H, Timmerman RD, Yang L, Wang J Tags: Phys Med Biol Source Type: research

Monte Carlo proton dose calculations using a radiotherapy specific dual-energy CT scanner for tissue segmentation and range assessment.
Abstract Proton beam ranges derived from dual-energy computed tomography (DECT) images from a dual-spiral radiotherapy (RT)-specific CT scanner were assessed using Monte Carlo (MC) dose calculations. Images from a dual-source and a twin-beam DECT scanner were also used to establish a comparison to the RT-specific scanner. Proton ranges extracted from conventional single-energy CT (SECT) were additionally performed to benchmark against literature values. Using two phantoms, a DECT methodology was tested as input for Geant4 MC proton dose calculations. Proton ranges were calculated for different mono-energetic proto...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Almeida IP, Schyns LEJR, Vaniqui A, van der Heyden B, Dedes G, Resch AF, Kamp F, Zindler JD, Parodi K, Landry G, Verhaegen F Tags: Phys Med Biol Source Type: research

4D-PET reconstruction using a spline-residue model with spatial and temporal roughness penalties.
Abstract 4D reconstruction of dynamic positron emission tomography (dPET) data can improve the signal-to-noise ratio in reconstructed image sequences by fitting smooth temporal functions to the voxel time-activity-curves (TACs) during the reconstruction, though the optimal choice of function remains an open question. We propose a spline-residue model, which describes TACs as weighted sums of convolutions of the arterial input function with cubic B-spline basis functions. Convolution with the input function constrains the spline-residue model at early time-points, potentially enhancing noise suppression in early ti...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Ralli GP, Chappell MA, McGowan DR, Sharma RA, Higgins GS, Fenwick JD Tags: Phys Med Biol Source Type: research

Effectiveness of different rescanning techniques for scanned proton radiotherapy in lung cancer patients.
In this study we investigate four mitigating rescanning techniques: (1) volumetric rescanning, (2) layered rescanning, (3) breath-sampled (BS) layered rescanning, and (4) continuous breath-sampled (CBS) layered rescanning. The breath-sampled methods will spread the layer rescans over a full breathing cycle, resulting in an improved averaging effect at the expense of longer treatment times. In CBS, we aim at further improving the averaging by delivering as many rescans as possible within one breathing cycle. The interplay effect was evaluated for 4D robustly optimized treatment plans (with and without rescanning...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Engwall E, Glimelius L, Hynning E Tags: Phys Med Biol Source Type: research

Feasibility of online IMPT adaptation using fast, automatic and robust dose restoration.
Abstract Intensity-modulated proton therapy (IMPT) offers excellent dose conformity and healthy tissue sparing, but it can be substantially compromised in the presence of anatomical changes. A major dosimetric effect is caused by density changes, which alter the planned proton range in the patient. Three different methods, which automatically restore an IMPT plan dose on a daily CT image were implemented and compared: (1) simple dose restoration (DR) using optimization objectives of the initial plan, (2) voxel-wise dose restoration (vDR), and (3) isodose volume dose restoration (iDR). Dose restorations were calcul...
Source: Physics in Medicine and Biology - March 29, 2018 Category: Physics Authors: Bernatowicz K, Geets X, Barragan A, Janssens G, Souris K, Sterpin E Tags: Phys Med Biol Source Type: research

Spiraling contaminant electrons increase doses to surfaces outside the photon beam of an MRI-linac with a perpendicular magnetic field.
This study investigated doses from SCE for an MRI-linac comprising a 7MV linac and a 1.5T MRI scanner. Surface doses to films perpendicular to the magnetic field and 5cm from the radiation beam edge showed increased dose within the projection of the primary beam, whereas films parallel to the magnetic field and 5cm from the beam edge showed no region of increased dose. However, the dose from contaminant electrons is absorbed within a few millimeters. For large fields, the SCE dose is within the same order of magnitude as doses from scattered and leakage photons. Doses for both SCE and scattered photons decrease rapidly wit...
Source: Physics in Medicine and Biology - March 29, 2018 Category: Physics Authors: Hackett SL, van Asselen B, Wolthaus JWH, Bluemink JJ, Ishakoglu K, Kok JGM, Lagendijk JJW, Raaymakers BW Tags: Phys Med Biol Source Type: research

Time-gated scintillator imaging for real-time optical surface dosimetry in total skin electron therapy.
Conclusions: The results from this proof-of-concept study documented the first use of small scintillator targets for remote surface dosimetry in ambient room lighting. The measured dose accuracy renders our method to be comparable to thermo-luminescent detector dosimetry, with the ultimate realization of accuracy likely to be better than shown here. Once optimized, this approach to remote dosimetry may substantially reduce time and effort required for surface dosimetry. PMID: 29588437 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - March 28, 2018 Category: Physics Authors: Bruza P, Gollub SL, Andreozzi JM, Tendler II, Williams BB, Jarvis LA, Gladstone DJ, Pogue BW Tags: Phys Med Biol Source Type: research

MR-compatibility assessment of MADPET4: a study of interferences between an SiPM-based PET insert and a 7 T MRI system.
Abstract Compromises in the design of a positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system should minimize the deterioration of image quality in both modalities, particularly when simultaneous demanding acquisitions are performed. In this work, the advantages of using individually read-out crystals with high-gain silicon photomultipliers (SiPMs) were studied with a small animal PET insert for a 7 T MRI system, in which the SiPM charge was transferred to outside the MRI scanner using coaxial cables. The interferences between the two systems were studied with three radio-frequenc...
Source: Physics in Medicine and Biology - March 27, 2018 Category: Physics Authors: Omidvari N, Topping G, Cabello J, Paul S, Schwaiger M, Ziegler SI Tags: Phys Med Biol Source Type: research

Impact of anti-charge sharing on the zero-frequency detective quantum efficiency of CdTe-based photon counting detector system: cascaded systems analysis and experimental validation.
Abstract Inter-pixel communication and anti-charge sharing (ACS) technologies have been introduced to photon counting detector (PCD) systems to address the undesirable charge sharing problem. In addition to improving the energy resolution of PCD, ACS may also influence other aspects of PCD performance such as detector multiplicity (i.e., the number of pixels triggered by each interacted photon) and detective quantum efficiency (DQE). In this work, a theoretical model was developed to address how ACS impacts the multiplicity and zero-frequency DQE [DQE(0)] of PCD systems. The work focused on cadmium telluride (CdTe...
Source: Physics in Medicine and Biology - March 27, 2018 Category: Physics Authors: Ji X, Zhang R, Chen GH, Li K Tags: Phys Med Biol Source Type: research

Super-resolution reconstruction of MR image with a novel residual learning network algorithm.
Abstract Spatial resolution is one of the key parameters of magnetic resonance imaging (MRI). The image super-resolution (SR) technique offers an alternative approach to improve the spatial resolution of MRI due to its simplicity. The convolutional neural networks (CNN)-based SR algorithms have achieved state-of-the-art performance, in which the global residual learning (GRL) strategy is now commonly used due to its effectiveness for learning image details for SR. However, the partial loss of image details usually happens in a very deep network due to the degradation problem. In this work, we propose a novel resid...
Source: Physics in Medicine and Biology - March 27, 2018 Category: Physics Authors: Shi J, Liu Q, Wang C, Zhang Q, Ying S, Xu H Tags: Phys Med Biol Source Type: research

Passive magnetic shielding in MRI-Linac systems.
Abstract Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resul...
Source: Physics in Medicine and Biology - March 26, 2018 Category: Physics Authors: Whelan B, Kolling S, Oborn BM, Keall P Tags: Phys Med Biol Source Type: research

Computer-aided diagnosis of prostate cancer on multi-parametric MRI: comparison between PUN and Tofts models.
In conclusion, the CAD software based on PUN parameters is feasible to detect PCa, without affecting segmentation quality, hence, it could be successfully applied in clinical settings, improving the automated diagnosis process, and reducing computational complexity. PMID: 29570456 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - March 23, 2018 Category: Physics Authors: Mazzetti S, Giannini V, Russo F, Regge D Tags: Phys Med Biol Source Type: research

A scalable and deformable stylized model of the adult human eye for radiation dose assessment.
In this study, we present a geometric eye model that is both scalable (allowing for changes in eye size) and deformable (allowing for changes in eye shape), and that is suitable for use in radiation transport studies of ocular exposures and radiation treatments of eye disease. The model allows continuous and variable changes in eye size (axial lengths from 20 to 26 mm) and eye shape (diopters from -12 to +6). As an explanatory example of its use, five models (emmetropic eyes of small, average, and large size, as well as average size eyes of -12D and +6D) were constructed and subjected to normally incident beams of monoener...
Source: Physics in Medicine and Biology - March 23, 2018 Category: Physics Authors: El Basha D, Furuta T, Iyer SSR, Bolch WE Tags: Phys Med Biol Source Type: research

High resolution propagation-based imaging system for < i > in vivo < /i > dynamic computed tomography of lungs in small animals.
High resolution propagation-based imaging system for in vivo dynamic computed tomography of lungs in small animals. Phys Med Biol. 2018 Mar 22;: Authors: Preissner M, Murrie RP, Pinar I, Werdiger F, Carnibella RP, Zosky GR, Fouras A, Dubsky S Abstract We have developed an X-ray imaging system for &lt;i&gt;in vivo&lt;/i&gt; four-dimensional computed tomography (4DCT) of small animals for pre-clinical lung investigations. Our customized laboratory facility is capable of high resolution &lt;i&gt;in vivo&lt;/i&gt; imaging at high frame rates. Characterization using phantoms...
Source: Physics in Medicine and Biology - March 22, 2018 Category: Physics Authors: Preissner M, Murrie RP, Pinar I, Werdiger F, Carnibella RP, Zosky GR, Fouras A, Dubsky S Tags: Phys Med Biol Source Type: research

Signal intensity analysis and optimization for < i > in vivo < /i > imaging of Cherenkov and excited luminescence.
Signal intensity analysis and optimization for in vivo imaging of Cherenkov and excited luminescence. Phys Med Biol. 2018 Mar 20;: Authors: LaRochelle EPM, Shell JR, Gunn JR, Davis SC, Pogue BW Abstract During external beam radiotherapy (EBRT), in vivo Cherenkov optical emissions can be used as a dosimetry tool or to excite luminescence, termed Cherenkov-excited luminescence (CEL) with microsecond-level time-gated cameras. The goal of this work was to develop a complete theoretical foundation for the detectable signal strength, in order to provide guidance on optimization of the limits of detection an...
Source: Physics in Medicine and Biology - March 20, 2018 Category: Physics Authors: LaRochelle EPM, Shell JR, Gunn JR, Davis SC, Pogue BW Tags: Phys Med Biol Source Type: research

Collimated proton pencil-beam scanning for superficial targets: impact of the order of range shifter and aperture.
CONCLUSIONS: Although experiments and calculations indicate a ranking of the three delivery options regarding lateral dose fall-off, there seems to be a limited impact on a multi-field treatment plan. . PMID: 29553047 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - March 19, 2018 Category: Physics Authors: Baeumer C, Janson M, Timmermann B, Wulff J Tags: Phys Med Biol Source Type: research

Optimization of the reconstruction parameters in [ < sup > 123 < /sup > I]FP-CIT SPECT.
Optimization of the reconstruction parameters in [123I]FP-CIT SPECT. Phys Med Biol. 2018 Mar 19;: Authors: Niñerola-Baizán A, Gallego J, Cot A, Aguiar P, Lomeña F, Pavía J, Ros D Abstract The aim of this work was to obtain a set of parameters to be applied in [123I]FP-CIT SPECT reconstruction in order to minimize the error between standardized and true values of the Specific Uptake Ratio (SUR) in dopaminergic neurotransmission SPECT studies. To this end, Monte Carlo simulation was used to generate a database of 1,380 projection data-sets from 23 subjects, including normal c...
Source: Physics in Medicine and Biology - March 19, 2018 Category: Physics Authors: Niñerola-Baizán A, Gallego J, Cot A, Aguiar P, Lomeña F, Pavía J, Ros D Tags: Phys Med Biol Source Type: research

The influence of medium elasticity on the prediction of histotripsy-induced bubble expansion and erythrocyte viability.
In this study, an analytic model to predict histotripsy-induced bubble expansion in a fluid was extended to include the effects of medium elasticity. Good agreement was observed between the predictions of the analytic model and numerical computations utilizing highly nonlinear excitations (shock-scattering histotripsy) and purely tensile pulses (microtripsy). No bubble expansion was computed for either form of histotripsy when the elastic modulus was greater than 20 MPa and the peak negative pressure was less than 50 MPa. Strain in the medium due to the expansion of a single bubble was also tabulated. The viability of red ...
Source: Physics in Medicine and Biology - March 19, 2018 Category: Physics Authors: Bader KB Tags: Phys Med Biol Source Type: research