MLC-tracking performance on the Elekta unity MRI-linac.
Abstract Recently, multileaf collimator (MLC)-tracking has been technically and clinically demonstrated showing promising improvements of radiotherapy of mobile sites. Furthermore, magnetic resonance imaging ( MRI )-guided treatments have shown to provide superior targetting performance due to on-line soft-tissue imaging. Hitherto, the combination of MLC -tracking and MRI has not been 
 investigated using clinically released hardware. In this note we aim to describe the technical feasibilty of such a combination on a clinically operating MRI -linac.
 
 The MLC -tracking system i...
Source: Physics in Medicine and Biology - June 3, 2019 Category: Physics Authors: Glitzner M, Woodhead PL, Borman PTS, Lagendijk JJW, Raaymakers BW Tags: Phys Med Biol Source Type: research

Potential applications of the quantitative susceptibility mapping (QSM) in MR-guided radiation therapy.
Conclusion: The proposed QSM-based technique relies on the standard MR pulse sequences and visualize the conventional MR-invisible metallic devices with CT-like positive contrast solely through post-processing. Upon in-vivo validation of the technique, QSM may have the potential to replace CT for an MR-only guided radiation therapy. &#13. PMID: 31151120 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 31, 2019 Category: Physics Authors: Nosrati R, Paudel MR, Ravi A, Pejovic-Milic A, Morton G, Stanisz G Tags: Phys Med Biol Source Type: research

Quantification of the dependencies of the Bragg peak degradation due to lung tissue in proton therapy on a CT-based lung tumor phantom.
Abstract The fine, sub-millimeter sized structure of lung tissue causes a degradation of the Bragg peak curve in particle therapy. The Bragg peak is degraded because particles of the same energy traverse lung tissue of different compositions of high and low density materials. Hence, they experience different energy losses resulting in variable ranges and a broadened Bragg peak. 
 Since this fine structure of lung tissue is not resolved in standard treatment-planning CTs, current state-of-the-art dose calculation procedures used in the clinical routine are unable to account for this degradation. Neglect...
Source: Physics in Medicine and Biology - May 31, 2019 Category: Physics Authors: Flatten V, Baumann KS, Weber U, Engenhart-Cabillic R, Zink K Tags: Phys Med Biol Source Type: research

Use of statistical approaches to improve the quality control of the dose delivery in radiotherapy.
In this study a ROC analysis is used to demonstrate the limits of the performance of the global gamma index as a method for detecting dose delivery errors. The performance of a global gamma index is compared with two approaches based on statistical tests for outliers detection. Two statistical approaches are considered: according to the first the distribution of the delivered doses is estimated based on an appropriate calibration procedure. According to the second one the distribution of the delivered doses is estimated based on the detection of relatively homogeneous regions of a plan and analyzing the distributions of pl...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Tulik M, Kabat D, Baran M, Kycia RA, Tabor Z Tags: Phys Med Biol Source Type: research

Range verification of radioactive ion beams of < sup > 11 < /sup > C and < sup > 15 < /sup > O using in-beam PET imaging.
Range verification of radioactive ion beams of 11C and 15O using in-beam PET imaging. Phys Med Biol. 2019 May 30;: Authors: Mohammadi A, Tashima H, Iwao Y, Takyu S, Akamatsu G, Nishikido F, Yoshida E, Kitagawa A, Parodi K, Yamaya T Abstract In advanced ion therapy, the visualization of the range of incident ions in a patient's body is important for exploiting the advantages of this type of therapy. It is ideal to use radioactive ion beams for in-beam positron emission tomography (PET) imaging in particle therapy due to the high quality of PET images caused by the high signal-to-noise ratio. We have sh...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Mohammadi A, Tashima H, Iwao Y, Takyu S, Akamatsu G, Nishikido F, Yoshida E, Kitagawa A, Parodi K, Yamaya T Tags: Phys Med Biol Source Type: research

About the Marty model of blood-brain barrier closure after its disruption using focused ultrasound.
rat B Abstract Many studies have demonstrated that pulsed ultrasound combined with circulating microbubbles can permeate the Blood-Brain Barrier in a reversible manner. In 2012, our group demonstrated that the BBB remains permeable to small MRI contrast agents up to 24 hours after ultrasound application and also that this duration was dependent on nanoparticle size. We exhibited a simple theoretical model explaining these observations (Marty et al. J Cereb Blood Flow Metab. 2012). However, in this original paper the expression of the BBB closure time (t&amp;lt;sub&amp;gt;1/2&amp;lt;/sub&amp;gt;) as...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Conti A, Mériaux S, Larrat B Tags: Phys Med Biol Source Type: research

MRI-based treatment planning for proton radiotherapy: dosimetric validation of a deep learning-based liver synthetic CT generation method.
This study proposes to integrate dense block into a 3D cycle-consistent generative adversarial networks (cycle GAN) framework in an effort to effectively learn the nonlinear mapping between MRI and CT pairs. A cohort of 21 patients with co-registered CT and MR pairs were used to test the deep learning-based sCT generation method by leave-one-out cross validation. The CT image quality, dosimetric accuracy and the distal range fidelity were rigorously checked, using side-by-side comparison against the corresponding original CT images. The average mean absolute error (MAE) was 72.87±18.16 HU. The relative differences o...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Liu Y, Lei Y, Wang Y, Wang T, Ren L, Lin L, McDonald M, Curran WJ, Liu T, Zhou J, Yang X Tags: Phys Med Biol Source Type: research

Assessment of imaging Cherenkov and scintillation signals in head and neck radiotherapy.
Abstract The goal of this study was to test the utility of time-gated optical imaging of head and neck radiotherapy treatments to measure surface dosimetry in real-time and inform possible interfraction replanning decisions. The benefit of both Cherenkov and scintillator imaging in head and neck treatments is direct daily feedback on dose, with no change to the clinical workflow. Emission from treatment materials was characterized by measuring radioluminescence spectra during irradiation and comparing emission intensities relative to Cherenkov emission produced in phantoms and scintillation from small plastic targ...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Alexander DA, Tendler II, Bruza P, Cao X, Schaner PE, Marshall BS, Jarvis LA, Gladstone DJ, Pogue BW Tags: Phys Med Biol Source Type: research

Basic evaluation of a novel four-dimensional target and human body phantom.
In this study, we investigated the basic performance of a multi-cell 4D phantom. All the CT numbers of the phantom were very close to those of human data. The geometric maximum amplitudes were 4.57 mm in the lateral direction, 4.59 mm in the ventrodorsal direction, and 3.68 mm in the cranio-caudal direction. Geometric errors were 0.84, 0.58, and 0.40 mm, respectively. Movements of the abdominal surface were stable for 60 seconds. Repeated measurements show no actual differences in target movements between multiple measurements and indicated high reproducibility (r &amp;gt; 0.97). End-to-end tests using Gafchromic film ...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Matsumoto Y, Kabuki S, Sugawara A, Kitahara T, Akiba T, Fujita Y, Kawamata I, Yamada K, Amino K, Sasaki Y, Nishida M, Murakami K, Sugahara K, Saito N, Kunieda E Tags: Phys Med Biol Source Type: research

< i > In vitro < /i > assessment of stiffness-dependent histotripsy bubble cloud activity in gel phantoms and blood clots.
In this study, histotripsy pulses were generated in agarose phantoms of Young's moduli ranging from 12.3 to 142 kPa, and &amp;lt;i&amp;gt;in vitro&amp;lt;/i&amp;gt; clot models with mild and strong platelet-activated retraction. Bubble cloud emissions were tracked with passive cavitation imaging, and the threshold acoustic power associated with phantom liquefaction was extracted with receiver operator characteristic analysis. The power of histotripsy-generated emissions and the degree of liquefaction were tabulated for both clot models. For the agarose phantoms, the acoustic power associated with liquefacti...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Hendley S, Bollen V, Anthony GJ, Paul JD, Bader KB Tags: Phys Med Biol Source Type: research

Monte Carlo calculation of monoenergetic and polyenergetic DgN coefficients for mean glandular dose estimates in mammography using a homogeneous breast model.
Abstract We computed normalized glandular dose (DgN) coefficients for mean glandular dose estimates in contemporary 2D mammography units, taking into account a realistic homogeneous model for the breast. We developed a Monte Carlo code based on the simulation toolkit GEANT4 ver. 10.00. The breast was modelled as a cylinder with a semi-cylindrical section with a radius of 10 cm, enveloped in a 1.45-mm thick skin layer, as found out in recent reports from the University of California Davis team in the analysis of breast computed tomography clinical scans. The compressed breast thickness was between 3 cm and 8 cm. Th...
Source: Physics in Medicine and Biology - May 29, 2019 Category: Physics Authors: Sarno A, Tucciariello RM, Mettivier G, di Franco F, Russo P Tags: Phys Med Biol Source Type: research

Classification of benign and malignant lung nodules from CT images based on hybrid features.
Abstract The classification of benign and malignant lung nodules has great significance for the early detection of lung cancer, since early diagnosis of nodules can greatly increase patient survival. In this paper, we propose a novel classification method for lung nodules based on hybrid features from computed tomography (CT) images. The method fused 3D deep dual path network (DPN) features, local binary pattern (LBP)-based texture features and histogram of oriented gradients (HOG)-based shape features to characterize lung nodules. DPN is a convolutional neural network which integrates the advantages of aggregated...
Source: Physics in Medicine and Biology - May 29, 2019 Category: Physics Authors: Zhang G, Yang Z, Gong L, Jiang S, Wang L Tags: Phys Med Biol Source Type: research

Conical beam geometry intensity-modulated radiation therapy.
Abstract Most commonly in radiation therapy, treatments are delivered in a co-planar geometry. Numerous advantages have been reported of adding non-coplanar beams to the treatment plan. The aim of this study was to compare current state-of-the-art VMAT and CyberKnife treatment plans to that of a novel linac design developed at Stanford which utilizes a static conical beam arrangement that allows the inclusion of a full ring diagnostic CT with shared isocenter with the treatment beams.&amp;#13; &amp;#13; Four clinical cases, prostate, lung, head/neck, and pediatric brain, were selected and treatment plans w...
Source: Physics in Medicine and Biology - May 24, 2019 Category: Physics Authors: Schueler E, Wang L, Loo B, Maxim PG Tags: Phys Med Biol Source Type: research

Correction of linear system drifts in magnetic particle imaging.
Abstract Magnetic Particle Imaging (MPI) is a tracer-based imaging technique that can be used for imaging vessels and organ perfusion with high temporal resolution. Background signals are a major source for image artifacts and in turn restrict the sensitivity of the method in practice. While static background signals can be removed from the measured signal by taking a dedicated background scan and performing subtraction, this simple procedure is not applicable in case of non-stationary background signals that occur in practice due to e.g. temperature drifts in the electromagnetic coils of the MPI scanner. Within t...
Source: Physics in Medicine and Biology - May 24, 2019 Category: Physics Authors: Knopp T, Gdaniec N, Rehr R, Graeser M, Gerkmann T Tags: Phys Med Biol Source Type: research

Shapes and distributions of soft tissue scatterers.
Abstract What causes scattering of ultrasound from normal soft tissues such as the liver, thyroid, and prostate? Commonly, the answer is formulated around the properties of spherical scatterers, related to cellular shapes and sizes. However an alternative view is that the closely packed cells forming the tissue parenchyma create the &amp;lt;i&amp;gt;reference media&amp;lt;/i&amp;gt;, and the long cylindrical-shaped fluid vessels serve as the &amp;lt;i&amp;gt;scattering sites&amp;lt;/i&amp;gt;. Under a weak scattering or Born approximation for the extracellular fluid in the vessels, ...
Source: Physics in Medicine and Biology - May 24, 2019 Category: Physics Authors: Parker KJ Tags: Phys Med Biol Source Type: research

Prediction of image noise contributions in proton computed tomography and comparison to measurements.
We present a method to accurately predict image noise in proton computed tomography (pCT) using data generated from a Monte Carlo simulation and a patient or object model that may be generated from a prior x-ray CT image. This enables noise prediction for arbitrary beam fluence settings and, therefore, the application of fluence-modulated pCT, which can achieve prescribed noise targets and may significantly reduce the integral patient dose.&amp;#13; &amp;#13; We extended an existing Monte Carlo simulation of a prototype pCT scanner to include effects of quenching in the energy detector scintillators and constructed...
Source: Physics in Medicine and Biology - May 24, 2019 Category: Physics Authors: Dickmann J, Wesp P, Rädler M, Rit S, Pankuch M, Johnson RP, Bashkirov VA, Schulte RW, Parodi K, Landry G, Dedes G Tags: Phys Med Biol Source Type: research

The microdosimetric extension in TOPAS: development and comparison with published data.
Abstract Microdosimetric energy depositions have been suggested as a key variable for the modeling of the relative biological effectiveness (RBE) in proton and ion radiation therapy. However, microdosimetry has been underutilized in radiation therapy. Recent advances in detector technology allow the design of new mico- and nano-dosimeters. At the same time Monte Carlo simulations have become more widely used in radiation therapy. In order to address the growing interest in the field, a microdosimetric extension was developed in TOPAS. The extension provides users with the functionality to simulate microdosimetric ...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Zhu H, Chen Y, Sung W, McNamara AL, Tran LT, Burigo LN, Rozenfeld AB, Li J, Faddegon B, Schuemann J, Paganetti H Tags: Phys Med Biol Source Type: research

Two-crossed-polarizers based optical property modulation method for ionizing radiation detection for positron emission tomography.
Abstract Recent work shows that Pockels effect and optics pump-probe measurement could be utilized as a novel method for 511 keV ionizing radiation photon detection for positron emission tomography which could potentially overcome inherent physical limitation for coincidence time resolution of around 100ps (Tao, Daghighian &amp; Levin 2016). In this paper, we embrace this observation and introduce a two-crossed-polarizers based setup in our work to achieve similar detection concept, which is a simpler and more compact setup with comparable ionizing radiation detection capability as the setup used in the previo...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Wang Y, Li Y, Yi F, Li J, Xie S, Peng Q, Xu J Tags: Phys Med Biol Source Type: research

Fast and accurate pseudo multispectral technique for whole-brain MRI tissue classification.
Abstract Numerous strategies have been proposed to classify brain tissues into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). However, many of them fail when classifying specific regions with low contrast between tissues. In this work, we propose an alternative pseudo multispectral classification (PMC) technique using CIE LAB spaces instead of gray scale T1-weighted MPRAGE images, combined with a new preprocessing technique for contrast enhancement and an optimized iterative K-means clustering. To improve the accuracy of the classification process, gray scale images were converted to multispect...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Fatnassi C, Zaidi H Tags: Phys Med Biol Source Type: research

Miniature fluorescence molecular tomography (FMT) endoscope based on a MEMS scanning mirror and an optical fiberscope.
We present a novel FMT endoscope by using a MEMS scanning mirror and an optical fiberscope. The diameter of this highly miniaturized FMT device is only 5mm. To our knowledge, this is the smallest FMT device we found so far. Several phantom experiments based on indocyanine green (ICG) were conducted to demonstrate the imaging ability of this device. Two tumor-bearing mice were systematically injected with tumor-targeted NIR fluorescent probes (ATF-PEG-IO-830) and were then imaged to further demonstrate the ability of this FMT endoscope for imaging small animals. PMID: 31117059 [PubMed - as supplied by publisher] (Sourc...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Yang H, Wang D, Shan T, Dai X, Xie H, Yang L, Jiang H Tags: Phys Med Biol Source Type: research

Scatter correction of cone-beam CT using a deep residual convolution neural network (DRCNN).
Abstract Scatter correction is an essential technique to improve the image quality of cone-beam CT (CBCT). Although different scatter correction methods have been proposed in the literature, a standard solution is still being studied due to the limitations including accuracy, computation efficiency and generalization. In this paper, we propose a novel scatter correction scheme for CBCT using a deep residual convolution neural network (DRCNN) to overcome the limitations. The proposed method combines the deep convolution neural network (CNN) and the residual learning framework (RLF) to train the mapping function fro...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Jiang Y, Yang C, Yang P, Hu X, Luo C, Xue Y, Xu L, Hu X, Zhang L, Wang J, Sheng K, Niu T Tags: Phys Med Biol Source Type: research

Radiosensitivity of colorectal cancer to < sup > 90 < /sup > Y and the radiobiological implications for radioembolisation therapy.
Conclusion: We derived radiosensitivity parameters for two CRC cell lines exposed to &amp;lt;sup&amp;gt;90&amp;lt;/sup&amp;gt;Y, 6 MV x-rays, and 137Cs γ-rays irradiation. These radiobiological parameters are critical to understanding the dose response of CRC lesions and ultimately informs the efficacy of &amp;lt;sup&amp;gt;90&amp;lt;/sup&amp;gt;Y SIRT relative to other radiation therapy modalities. PMID: 31117062 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Lee BQ, Abbott EM, Able S, Thompson J, Hill MA, Kartsonaki C, Vallis KA, Falzone N Tags: Phys Med Biol Source Type: research

The stability of imaging biomarkers in radiomics: a framework for evaluation.
Abstract This paper studies the sensitivity of a range of image texture parameters used in radiomics to: i) the number of intensity levels, ii) the method of quantisation to select the intensity levels and iii) the use of an intensity threshold. 43 commonly used texture features were studied for the gross target volume outlined on the CT component of PET/CT scans of 50 patients with non-small cell lung carcinoma (NSCLC). All cases were quantised for all values between 4 and 128 intensity levels using four commonly used quantisation methods. All results were analysed with and without a threshold range of -200 HU to...
Source: Physics in Medicine and Biology - May 22, 2019 Category: Physics Authors: Wang HYC, Donovan EM, Nisbet A, South CP, Alobaidli S, Ezhil V, Phillips I, Prakash V, Ferreira M, Webster P, Evans PM Tags: Phys Med Biol Source Type: research

Generating synthesized computed tomography (CT) from cone-beam computed tomography (CBCT) using CycleGAN for adaptive radiation therapy.
Abstract Throughout the course of delivering a radiation therapy treatment, which may take several weeks, a patient's anatomy may change drastically, and adaptive radiation therapy (ART) may be needed. Cone-beam computed tomography (CBCT), which is often available during the treatment process, can be used for both patient positioning and ART re-planning. However, due to the prominent amount of noise, artifacts, and inaccurate Hounsfield Unit (HU) values, the dose calculation based on CBCT images could be inaccurate for treatment planning. One way to solve this problem is to convert CBCT images to more accurate syn...
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Liang X, Chen L, Nguyen D, Zhou Z, Gu X, Yang M, Wang J, Jiang SB Tags: Phys Med Biol Source Type: research

MRI < i > B < /i > < sub > 0 < /sub > homogeneity and geometric distortion with continuous linac gantry rotation on an Elekta Unity MR-linac.
Conclusion: MR imaging on the Elekta Unity MR-Linac with the gantry in continuous motion is negligibly different from the static gantry case with current clinical pulse sequences. Real-time tracking and treatment plan adaptation using MR images obtained with the linac gantry in motion is possible. PMID: 31108467 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Jackson SJ, Glitzner M, Tijssen RHN, Raaymakers BW Tags: Phys Med Biol Source Type: research

Impact of intensity discretization on textural indices of [18F]FDG-PET tumour heterogeneity in lung cancer patients.
ényi E, Balkay L Abstract Quantifying tumour heterogeneity from [18F]FDG-PET images promises benefits for treatment selection of cancer patients. Here, the calculation of texture parameters mandates an initial discretization step (binning) to reduce the number of intensity levels. Typically, three types of discrimination methods are used: lesion relative resampling (LRR) with fixed bin number, lesion absolute resampling (LAR) and absolute resampling (AR) with fixed bin widths. We investigated the effects of varying bin widths or bin number using 27 commonly cited local and regional texture indices (TIs) app...
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Forgács A, Béresová M, Garai I, Lassen ML, Beyer T, DiFranco MD, Berényi E, Balkay L Tags: Phys Med Biol Source Type: research

Deployable cylindrical phased-array applicator mimicking a concentric-ring configuration for minimally-invasive delivery of therapeutic ultrasound.
Abstract A novel design for a deployable catheter-based ultrasound applicator for endoluminal and laparoscopic intervention is introduced. By combining a 1D cylindrical ring phased array with an expandable paraboloid or conical-shaped balloon-based reflector, the applicator can be controllably collapsed for compact delivery and deployed to mimic a forward-firing larger diameter concentric ring array with tight focusing and electronic steering capabilities in depth. Comprehensive acoustic and biothermal parametric studies were employed to characterize the capabilities of the applicator design as a function of trans...
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Adams M, Diederich C Tags: Phys Med Biol Source Type: research

A fast regularized iterative algorithm for fan-beam CT reconstruction.
Abstract We propose a fast iterative image reconstruction algorithm for normal, short-scan, and super-short-scan fan-beam computed tomography (CT), which aims at iterative reconstruction for low-dose and few-view CT by minimizing a data-fidelity term regularized with a total variation (TV) penalty. The derivation of the algorithm can be outlined as follows. First, the original minimization problem is formulated into a saddle-point (primal-dual) problem by using the Lagrangian duality, to which we apply the alternating projection proximal (APP) algorithm, which belongs to a class of first-order primal-dual methods....
Source: Physics in Medicine and Biology - May 20, 2019 Category: Physics Authors: Wang T, Kudo H, Yamazaki F, Liu H Tags: Phys Med Biol Source Type: research

A Survey Study of Female Radiation Oncology Residents' Experiences to Inform Change.
CONCLUSIONS: In the first study to our knowledge to focus specifically on the experiences of women residents in radiation oncology, a number of areas for potential improvement were highlighted, including isolation and under-representation, mentorship needs, bias and harassment, and numerous other gender-based obstacles, including need for support during pregnancy and motherhood. These findings support the organization of groups such as the Society of Women in Radiation Oncology, which seeks to target these needs in order to promote gender equity. PMID: 31108141 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 17, 2019 Category: Physics Authors: Osborn VW, Doke K, Griffith KA, Jones R, Lee A, Maquilan G, Masters AH, Albert AA, Dover LL, Puckett LL, Hentz C, Kahn JM, Colbert LE, Barry PN, Jagsi R Tags: Int J Radiat Oncol Biol Phys Source Type: research

Charged particle radiobiology beamline using tandem accelerator-based MeV protons and carbon ions: a pilot study on the track-end radiation quality, variable biological effectiveness and Bayesian beam dosimetry.
Abstract For in vitro cell irradiation using tandem accelerator-based MeV protons and carbon ions, by TOPAS simulation, a polit study of performance evaluation is presented on a collimation beamline for 3 MeV protons and 10 MeV carbon ions from a 2×3 MV tandem accelerator. Based on the elements and source parameters, a collimated beam of 2.8 MeV protons or 2.5 MeV carbon ions, with 5.175 mm or 5.166 mm full width tenth maximum (FWTM)), respectively, can be delivered to target cell dish. TOPAS simulations and/or deterministic algorithms present a Bragg curve of linear energy transfer (LET) (10~70 keV/μm) a...
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Li X, Zhang W, Wang X, Chen X, Pan H, Ruan Y, Khaledi N, Wei T, He X, Zhuo W, Shao C, Pan Y, Shi LQ, Fu S, Wang X Tags: Phys Med Biol Source Type: research

Non-invasive myocardial performance mapping using 3D echocardiographic stress-strain loops.
In conclusion, stress-strain loops were, for the first time, estimated from 3D echocardiography and correlated to the clinical gold standard for local metabolism, showing the future potential of RT3DE for the assessment of local metabolic activity of the heart. PMID: 31096199 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Pedrosa J, Duchenne J, Queirós S, Degtiarova G, Gheysens O, Claus P, Voigt JU, D'hooge J Tags: Phys Med Biol Source Type: research

Integrating computer vision and non-linear optimization for automated deformable registration of three-dimensional medical images.
Abstract Deformable image registration (DIR), the process of estimating and applying non-linear transforms to spatially align sets of two or more images, is a challenging task with many important clinical applications including kinetic analysis, cancer treatment targeting, and evaluation of treatment response. Current techniques use non-linear optimizations only to reach a local minimum and not a globally optimal solution, limiting application to cases with small spatial displacements. Various semi-dense feature-based methods drawing inspiration from mammalian systems as the basis for 2D visual processing have bee...
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Huang K Tags: Phys Med Biol Source Type: research

Seated vs. supine: consideration of the optimum measurement posture for brain-dedicated PET.
In this report, we describe development of a markerless and contactless head motion tracking system and a study of healthy volunteers in several different postures to determine the optimum posture for brain PET. We used Kinect® (Microsoft) and developed software that can measure head motion with about 1-mm (translation) and less than 1-deg (rotation) accuracy. In the volunteer study, we measured the amount of head motion, with and without head fixation, in supine, normal sitting, and reclining postures. The results indicated that the normal sitting posture without head fixation had the largest head movement, and that t...
Source: Physics in Medicine and Biology - May 16, 2019 Category: Physics Authors: Iwao Y, Tashima H, Yoshida E, Nishikido F, Ida T, Yamaya T Tags: Phys Med Biol Source Type: research

Incorporating dosimetric features into the prediction of 3D VMAT dose distributions using deep convolutional neural network.
In this study we propose a method to incorporate the dosimetric features in the construction of a more reliable dose prediction model based on the deep convolutional neural network (CNN). In addition to the contour information, the dose distribution from a PTV-only plan (i.e., the plan with the best PTV coverage by sacrificing the OARs sparing) is also employed as the model input to build a deep learning based dose prediction model. A database of 60 volumetric modulated arc therapy (VMAT) plans for the prostate cancer patients was used for training. The trained prediction model was then tested on a cohort of 10 cases. Dose...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Ma M, Kovalchuk N, Buyyounouski MK, Xing L, Yang Y Tags: Phys Med Biol Source Type: research

Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research.
Abstract Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limit...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Soultanidis G, Subiel A, Renard I, Reinhart AM, Green VL, Oelfke U, Archibald S, Greenman J, Tulk A, Walker A, Schettino G, Cawthorne C Tags: Phys Med Biol Source Type: research

Applying a variable relative biological effectiveness (RBE) might affect the analysis of clinical trials comparing photon and proton therapy for prostate cancer.
Abstract The purpose of this study was the evaluation of the impact of a variable relative biological effectiveness (RBE) compared to a constant RBE value of 1.1 in proton therapy prostate trials due to uncertainties in α/β ratio.&amp;#13; &amp;#13; Twenty patients receiving passive scattered proton therapy (PSPT) and fifteen patients receiving intensity modulated proton therapy (IMPT) were compared to twenty patients treated with 7-field intensity modulated photon therapy (IMRT). For proton beam therapy (PBT), the RBE was estimated using two different RBE models. Tumor control probabilities (TC...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Marteinsdottir M, Paganetti H Tags: Phys Med Biol Source Type: research

Multifunction bismuth gadolinium oxide nanoparticles as radiosensitizer in radiation therapy and imaging.
Abstract Multifunction bismuth-based nanoparticles with the ability of diagnostic and therapeutic functions have drawn extensive attention as theranostic agent in radiation therapy and imaging due to high atomic number, low toxicity, and low cost. Herein, we tried to introduce multifunction bismuth gadolinium oxide nanoparticles (BiGdO3) as a new theranostic agent for radiation therapy, computed tomography (CT) and magnetic resonance imaging (MRI). After synthesized of BiGdO3 nanoparticles and surface modifications of them with PEG, biocompatibility of the nanoparticle was evaluated by the CCK-8 assay. We investig...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Rajaee A, Zhao L, Wang S, Wang D, Liu Y, Wang J, Ying K Tags: Phys Med Biol Source Type: research

Minimum MU optimization (MMO): an inverse optimization approach for the PBS minimum MU constraint.
Abstract The deliverability of proton pencil beam scanning (PBS) treatment plans is subject to the minimum monitor unit (MU) constraint. This work introduces an inverse optimization approach to enforce the minimum MU constraint on planned spots, for accurate delivery of the planned dose. We formulate the minimum MU problem as an inverse optimization problem that accounts for the minimum MU constraint, i.e., minimum MU optimization (MMO). The MMO minimizes the difference between planned dose and deliverable dose while simultaneously enforcing the minimum MU constraint. Owing to the minimum MU constraint, MMO is non...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Gao H, Clasie BM, Liu T, Lin Y Tags: Phys Med Biol Source Type: research

Acoustic radiation force induced accumulation and dynamics of microbubbles on compliant surfaces.
Abstract Ultrasound stimulated microbubbles have been shown to be capable of breaking up blood clots through micro-scale interactions occurring near the clot surface. However, only a small fraction of bubbles circulating in the bloodstream will be in close proximity to such boundaries, where they must be to elicit therapeutic effects. Here, the accumulation and subsequent behavior of microbubbles displaced from an overlying flow channel to a boundary under radiation forces were examined. Experimental data were acquired using a novel high speed microscopy configuration and simulations were conducted to provide insi...
Source: Physics in Medicine and Biology - May 13, 2019 Category: Physics Authors: Acconcia CN, Leung BYC, Winch G, Wang J, Hynynen K, Goertz DE Tags: Phys Med Biol Source Type: research

Design and commissioning of an image-guided small animal radiation platform and quality assurance protocol for integrated proton and x-ray radiobiology research.
Conclusions: An image-guided small animal proton/x-ray research system was developed to enable in vivo investigations of radiobiological effects of proton beams, comparative studies between proton and x-ray beams, and investigations into novel proton treatment methods. PMID: 31075786 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 10, 2019 Category: Physics Authors: Kim M, Irmen P, Shoniyozov K, Verginadis II, Cengel KA, Koumenis C, Metz JM, Dong L, Diffenderfer E Tags: Phys Med Biol Source Type: research

Quantifying the dosimetric impact of organ-at-risk delineation variability in head and neck radiation therapy in the context of patient setup uncertainty.
Conclusion: The dosimetric impact of DV appeared to decrease when random and systematic SV was considered. Sensitivity to DV was affected by OAR objective type (i.e. Dmean vs. Dmax objectives) as well as distance from the target volume. PMID: 31071687 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Aliotta E, Nourzadeh H, Siebers JV Tags: Phys Med Biol Source Type: research

An age-dependent series of eye models for radiation dosimetry.
Abstract Several studies have been appeared, up to now, that indicate the effect of accurate simulation on dose received by different substructures of the eye, irradiated by external beams of short-range radiation such as electron. Different representations of the eye have consequently been introduced. Their accuracies depend on the purpose for which models are described or the degree of accuracy of information that models are based upon. All of developed models have presented the eye of an adult human, while the size, shape, and thickness of the eye substructures change with age. This work offers a series of age-...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Vejdani-Noghreiyan A, Ebrahimi-Khankook A Tags: Phys Med Biol Source Type: research

Quality assurance of gating response times for surface guided motion management treatment delivery using an electronic portal imaging detector.
This study shows a methodology which measured gating response times for AlignRT/Varian Truebeam combination which appears to be applicable to any surface guided monitoring/Linac combination as well as those combinations which incorporate extended lag times (&amp;gt;200ms). Beam on lag time appears to be measurably greater than beam off lag time. Although these gating response times are slower than other gating systems on the market, the advantages surface guided radiotherapy (SGRT) could potentially provide for treatment accuracy is discussed as well as demonstrating the lack of guidance regarding SGRT with respect to ...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Barfield G, Burton EW, Stoddart J, Metwaly M, Cawley MG Tags: Phys Med Biol Source Type: research

Development of a YAP(Ce) camera for the imaging of secondary electron bremsstrahlung X-ray emitted during carbon-ion irradiation toward the use of clinical conditions.
Abstract Low-energy X-ray imaging of the secondary electron bremsstrahlung X-ray emitted during carbon-ion irradiation is a promising method for range estimation. However, it remains unclear whether the method can be used for imaging with the clinical dose levels of carbon-ion and whether the bremsstrahlung X-ray can be detected from the deeper part of the body. To clarify these points, we developed a new high resolution low-energy X-ray camera and conducted imaging of the secondary electron bremsstrahlung X-ray during the irradiation of carbon-ions of different energies and intensities. Imaging was also tried wit...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Yamamoto S, Yamaguchi M, Akagi T, Sasano M, Kawachi N Tags: Phys Med Biol Source Type: research

Nanoparticle-mediated histotripsy (NMH) using perfluorohexane & quot;nanocones & quot.
In this study, we investigate the use of a newly developed NMH nanoparticle synthesized using an inclusion complex of methylated β-cyclodextrin and perfluorohexane (PFH). These "nanocones" (NCs) have advantages compared to previously used ND's due to their smaller size (~50nm), simple synthesis method, higher stability and information of definite PFH amount carried by the NC. To test the hypothesis that NCs can reduce the NMH cavitation threshold similar to ND's, and that the NMH cavitation threshold is dependent upon the total PFH concentration, tissue phantoms containing concentrations of NCs ranging from ...
Source: Physics in Medicine and Biology - May 9, 2019 Category: Physics Authors: Khirallah J, Schmieley R, Demirel E, Rehman TU, Howell J, Yuksel Durmaz Y, Vlaisavljevich E Tags: Phys Med Biol Source Type: research

A survey of computational frameworks for solving the acoustic inverse problem in three-dimensional photoacoustic computed tomography.
Abstract Photoacoustic computed tomography (PACT), also known as optoacoustic tomography,&amp;#13; is an emerging imaging technique that holds great promise for biomedical imaging.&amp;#13; PACT is a hybrid imaging method that can exploit the strong endogeneous contrast of optical methods&amp;#13; along with the high spatial resolution of ultrasound methods.&amp;#13; In its canonical form that is addressed in this article, PACT seeks to estimate the photoacoustically-induced&amp;#13; intial pressure distribution within the object.&amp;#13; Image reconstruction methods are employed to solve ...
Source: Physics in Medicine and Biology - May 8, 2019 Category: Physics Authors: Poudel J, Lou Y, Anastasio MA Tags: Phys Med Biol Source Type: research

Inversion of displacement fields to quantify the magnetic particle distribution in homogeneous elastic media from magnetomotive ultrasound.
Abstract Magnetomotive ultrasound (MMUS) contrasts superparamagnetic iron-oxide nanoparticles (SPIOs) that undergo submicrometer-scale displacements in response to a magnetic gradient force applied to an imaging sample. Typically, MMUS signals are defined in a way that is proportional to the SPIO displacements, rendering an indirect measure of the SPIO density distribution. Displacement-based MMUS, however, manifests "halo effects" that extend into regions without SPIOs due to their inherent mechanical coupling with the medium. To reduce such effects and to provide a more accurate representation of the S...
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Thapa D, Levy BE, Marks DL, Oldenburg AL Tags: Phys Med Biol Source Type: research

Structural and practical identifiability of dual-input kinetic modeling in dynamic PET of liver inflammation.
Abstract Dynamic F18-FDG PET with tracer kinetic modeling has the potential to noninvasively evaluate human liver inflammation using the FDG blood-to-tissue transport rate K1. Accurate kinetic modeling of dynamic liver PET data and K1 quantification requires the knowledge of dual-blood input function from the hepatic artery and portal vein. While the arterial input function can be derived from the aortic region on dynamic PET images, it is difficult to extract the portal vein input function accurately from PET images. The optimization-derived dual-input kinetic modeling approach has been proposed to overcome this ...
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Zuo Y, Sarkar S, Corwin MT, Olson KA, Badawi RD, Wang G Tags: Phys Med Biol Source Type: research

Small field correction factors determination for several active detectors using a Monte Carlo method in the Elekta Axesse linac equipped with circular cones.
Abstract A Monte Carlo (MC) method was used to determine small field output correction factors for several active detectors (Exradin A16, Exradin A26, PTW microLion, PTW microDiamond, Exradin W1 and IBA RAZOR) for an Elekta Axesse linac equipped with circular cones. MC model of the linac was built with the GamBet software, using the Penelope code system. The dose-to-water simulation for each cone, ranging from 5 to 30 mm of diameter size, was used to calculate field factors and the results were validated together with Gafchromic EBT3 film. Output factors (OFs) were measured with the active detectors and correction...
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Girardi A, Fiandra C, Giglioli FR, Gallio E, Hammad Ali O, Ragona R Tags: Phys Med Biol Source Type: research

Time-based signal sampling using sawtooth-shaped threshold.
In conclusion, the proposed method can be a cost-effective solution for data collection in future SiPM-based PET systems. PMID: 31051493 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 3, 2019 Category: Physics Authors: Ko GB, Lee JS Tags: Phys Med Biol Source Type: research