bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallel processing of afferent olfactory sensory information
Authors: Vaaga Christopher E. , Westbrook Gary L. 
Published: July 2016

Key points
The functional synaptic connectivity between olfactory receptor neurons and principal cells within the olfactory bulb is not well understood.
One view suggests that mitral cells, the primary output neuron of the olfactory bulb, are solely activated by feedforward excitation.
Using focal, single glomerular stimulation, we demonstrate that mitral cells receive direct, monosynaptic input from olfactory receptor neurons.
Compared to external tufted cells, mitral cells have a prolonged afferent‐evoked EPSC, which serves to amplify the synaptic input.
The properties of presynaptic glutamate release from olfactory receptor neurons are similar between mitral and external tufted cells.
Our data suggest that afferent input enters the olfactory bulb in a parallel fashion.
AbstractPrimary olfactory receptor neurons terminate in anatomically and functionally discrete cortical modules known as olfactory bulb glomeruli. The synaptic connectivity and postsynaptic responses of mitral and external tufted cells within the glomerulus may involve both direct and indirect components. For example, it has been suggested that sensory input to mitral cells is indirect through feedforward excitation from external tufted cells. We also observed feedforward excitation of mitral cells with weak stimulation of the olfactory nerve layer; however, focal stimulation of an axon bundle entering an individual glomerulus revealed that mitral cells receive monosynaptic afferent inputs. Although external tufted cells had a 4.1‐fold larger peak EPSC amplitude, integration of the evoked currents showed that the synaptic charge was 5‐fold larger in mitral cells, reflecting the prolonged response in mitral cells. Presynaptic afferents onto mitral and external tufted cells had similar quantal amplitude and release probability, suggesting that the larger peak EPSC in external tufted cells was the result of more synaptic contacts. The results of the present study indicate that the monosynaptic afferent input to mitral cells depends on the strength of odorant stimulation. The enhanced spiking that we observed in response to brief afferent input provides a mechanism for amplifying sensory information and contrasts with the transient response in external tufted cells. These parallel input paths may have discrete functions in processing olfactory sensory input.
Computational Fluid Dynamics Investigation of Supercritical Water Flow and Heat Transfer in a Rod Bundle With Grid Spacers
Authors: Gradecka Malwina , Thiele Roman , Anglart Henryk 
Published: July 2016

This paper presents a steady-state computational fluid dynamics approach to supercritical water flow and heat transfer in a rod bundle with grid spacers. The current model was developed using the ANSYS Workbench 15.0 software (CFX solver) and was first applied to supercritical water flow and heat transfer in circular tubes. The predicted wall temperature was in good agreement with the measured data. Next, a similar approach was used to investigate three-dimensional (3D) vertical upward flow of water at supercritical pressure of about 25 MPa in a rod bundle with grid spacers. This work aimed at understanding thermo- and hydrodynamic behavior of fluid flow in a complex geometry at specified boundary conditions. The modeled geometry consisted of a 1.5-m heated section in the rod bundle, a 0.2-m nonheated inlet section, and five grid spacers. The computational mesh was prepared using two cell types. The sections of the rods with spacers were meshed using tetrahedral cells due to the complex geometry of the spacer, whereas sections without spacers were meshed with hexahedral cells resulting in a total of 28 million cells. Three different sets of experimental conditions were investigated in this study: a nonheated case and two heated cases. The nonheated case, A1, is calculated to extract the pressure drop across the rod bundle. For cases B1 and B2, a heat flux is applied on the surface of the rods causing a rise in fluid temperature along the bundle. While the temperature of the fluid increases along with the flow, heat deterioration effects can be present near the heated surface. Outputs from both B cases are temperatures at preselected locations on the rods surfaces.
SU‐B‐BRA‐03: A Physician Perspective on the Value of Medical Physics
Authors: Burri S. 
Published: July 2016

In the current rapidly changing Healthcare environment, many groups are competing for limited resources. How can medical physicists position themselves to be a relevant stakeholder in the discussion of how those resources are allocated Our value goes beyond what can be shown in a business plan and is heavily involved with safety and quality.Three areas will be explored:
What is our value?
Who needs to receive that message?
How do we communicate that message?To help frame the discussion in terms of how other stakeholders may view the value of medical physicists, a physician and an administrator will present their perspective.Lastly, a multidisciplinary panel will present real life examples of strategies that can be utilized today to establish the value of medical physicists. The presentation of these examples will lead into an interactive question and answer time.V. Willcut, I work for Elekta. There was no research associated with this talk.
SU‐B‐BRA‐06: Panel Member
Authors: Clements J. 
Published: July 2016

In the current rapidly changing Healthcare environment, many groups are competing for limited resources. How can medical physicists position themselves to be a relevant stakeholder in the discussion of how those resources are allocated Our value goes beyond what can be shown in a business plan and is heavily involved with safety and quality.Three areas will be explored:
What is our value?
Who needs to receive that message?
How do we communicate that message?To help frame the discussion in terms of how other stakeholders may view the value of medical physicists, a physician and an administrator will present their perspective.Lastly, a multidisciplinary panel will present real life examples of strategies that can be utilized today to establish the value of medical physicists. The presentation of these examples will lead into an interactive question and answer time.V. Willcut, I work for Elekta. There was no research associated with this talk.
SU‐C‐201‐02: Dosimetric Verification of SBRT with FFF‐VMAT Using a 3‐D Radiochromic/Optical‐CT Dosimetry System
Authors: Na Y , Black P , Adamovics J , Wuu C 
Published: July 2016

Purpose:With an increasing use of small field size and high dose rate irradiation in the advances of radiotherapy techniques, such as stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS), an in‐depth quality assurance (QA) system is required. The purpose of this study is to investigate a high resolution optical CT‐based 3D radiochromic dosimetry system for SBRT with intensity modulated radiotherapy (IMRT) and flattening filter free (FFF) volumetric modulated arc therapy (VMAT).Methods:Cylindrical PRESAGE radiochromic dosimeters of 10cm height and 11cm diameter were used to validate SBRT. Four external landmarks were placed on the surface of each dosimeter to define the isocenter of target. SBRT plans were delivered using a Varian TrueBeam™ linear accelerator (LINAC). Three validation plans, SBRT with IMRT (6MV 600MU/min), FFF‐VMAT (10MV 2400MU/min), and mixed FFF‐VMAT (6MV 1400MU/min, 10MV 2400MU/min), were delivered to the PRESAGE dosimeters. Each irradiated PRESAGE dosimeter was scanned using a single laser beam optical CT scanner and reconstructed with a 1mm × 1mm high spatial resolution. The comparison of measured dose distributions of irradiated PRESAGE dosimeters to those calculated by Pinnacle3 treatment planning system (TPS) were performed with a 10% dose threshold, 3% dose difference (DD), and 3mm distance‐to‐agreement (DTA) Gamma criteria.Results:The average pass rates for the gamma comparisons between PRESAGE and Pinnacle3 in the transverse, sagittal, coronal planes were 94.6%, 95.9%, and 96.4% for SBRT with IMRT, FFF‐VMAT, and mixed FFF‐VMAT plans, respectively. A good agreement of the isodose distributions of those comparisons were shown at the isodose lines 50%, 70%, 80%, 90% and 98%.Conclusion:This study demonstrates the feasibility of the high resolution optical CT‐based 3D radiochromic dosimetry system for validation of SBRT with IMRT and FFF‐VMAT. This dosimetry system offers higher precision QA with 3D dose information for small beams compared to what is currently available.
SU‐C‐201‐06: Small Field Correction Factors for the MicroDiamond Detector in the Gamma Knife‐Model C Derived Using Monte Carlo Methods
Authors: Barrett J C , Knill C 
Published: July 2016

Purpose:To determine small field correction factors for PTW's microDiamond detector in Elekta's Gamma Knife Model‐C unit. These factors allow the microDiamond to be used in QA measurements of output factors in the Gamma Knife Model‐C; additionally, the results also contribute to the discussion on the water equivalence of the relatively‐new microDiamond detector and its overall effectiveness in small field applications.Methods:The small field correction factors were calculated as k correction factors according to the Alfonso formalism. An MC model of the Gamma Knife and microDiamond was built with the EGSnrc code system, using BEAMnrc and DOSRZnrc user codes. Validation of the model was accomplished by simulating field output factors and measurement ratios for an available ABS plastic phantom and then comparing simulated results to film measurements, detector measurements, and treatment planning system (TPS) data. Once validated, the final k factors were determined by applying the model to a more waterlike solid water phantom.Results:During validation, all MC methods agreed with experiment within the stated uncertainties: MC determined field output factors agreed within 0.6% of the TPS and 1.4% of film; and MC simulated measurement ratios matched physically measured ratios within 1%. The final k correction factors for the PTW microDiamond in the solid water phantom approached unity to within 0.4%±1.7% for all the helmet sizes except the 4 mm; the 4 mm helmet size over‐responded by 3.2%±1.7%, resulting in a k factor of 0.969.Conclusion:Similar to what has been found in the Gamma Knife Perfexion, the PTW microDiamond requires little to no corrections except for the smallest 4 mm field. The over‐response can be corrected via the Alfonso formalism using the correction factors determined in this work. Using the MC calculated correction factors, the PTW microDiamond detector is an effective dosimeter in all available helmet sizes.The authors would like to thank PTW (Friedberg, Germany) for providing the PTW microDiamond detector for this research.
SU‐C‐BRC‐06: OpenCL‐Based Cross‐Platform Monte Carlo Simulation Package for Carbon Ion Therapy
Authors: Qin N , Pinto M , Tian Z , Dedes G , Pompos A , Jiang S , Parodi K , Jia X 
Published: July 2016

Purpose:Monte Carlo (MC) simulation is considered to be the most accurate method for calculation of absorbed dose and fundamental physical quantities related to biological effects in carbon ion therapy. Its long computation time impedes clinical and research applications. We have developed an MC package, goCMC, on parallel processing platforms, aiming at achieving accurate and efficient simulations for carbon therapy.Methods:goCMC was developed under OpenCL framework. It supported transport simulation in voxelized geometry with kinetic energy up to 450 MeV/u. Class II condensed history algorithm was employed for charged particle transport with stopping power computed via Bethe‐Bloch equation. Secondary electrons were not transported with their energy locally deposited. Energy straggling and multiple scattering were modeled. Production of secondary charged particles from nuclear interactions was implemented based on cross section and yield data from Geant4. They were transported via the condensed history scheme. goCMC supported scoring various quantities of interest e.g. physical dose, particle fluence, spectrum, linear energy transfer, and positron emitting nuclei.Results:goCMC has been benchmarked against Geant4 with different phantoms and beam energies. For 100 MeV/u, 250 MeV/u and 400 MeV/u beams impinging to a water phantom, range difference was 0.03 mm, 0.20 mm and 0.53 mm, and mean dose difference was 0.47%, 0.72% and 0.79%, respectively. goCMC can run on various computing devices. Depending on the beam energy and voxel size, it took 20∼100 seconds to simulate 107 carbons on an AMD Radeon GPU card. The corresponding CPU time for Geant4 with the same setup was 60∼100 hours.Conclusion:We have developed an OpenCL‐based cross‐platform carbon MC simulation package, goCMC. Its accuracy, efficiency and portability make goCMC attractive for research and clinical applications in carbon therapy.
SU‐C‐BRB‐03: Cross‐Institutional Validation of An Ultrafast Automatic Planning Platform for Breast Irradiation
Authors: Li T , Sheng Y , Lockamy V , Anne P , Simone N , Wu QJ , Yu Y 
Published: July 2016

Purpose:Recently an ultrafast automatic planning system for breast irradiation using tangential beams was developed by modeling relationships between patient anatomy and achieved dose distribution. This study evaluates the performance of this system when applied to a different patient population and dose calculation algorithm.Methods:The system and its anatomy‐to‐dose models was developed at institution A based on 20 cases, which were planned using manual fluence painting technique and calculated WITH heterogeneity correction. Institution B uses field‐in‐field planning technique and dose calculation WITHOUT heterogeneity correction. 11 breast cases treated at Institution B were randomly selected for retrospective study, including left and right sides, and different breast size (irradiated volumes defined by Jaw/MLC opening range from 875cc to 3516cc). Comparisons between plans generated automatically (Auto‐Plans) and those used for treatment (Clinical‐Plans) included: energy choice (single/mixed), volumes receiving 95%/100%/105%/110% Rx dose (V95%/V100%/V105%/V100%) relative to irradiated volume, D1cc, and LungV20Gy.Results:In 9 out of 11 cases single/mixed energy choice made by the software agreed with Clinical‐Plans. For the remaining 2 cases software recommended using mixed energy and dosimetric improvements were observed. V100% were similar (p=0.223, Wilcoxon Signed‐Rank test) between Auto‐Plans and Clinical‐Plans (57.6±8.9% vs. 54.8±9.5%). V95% is 2.3±3.0% higher for Auto‐Plans (p=0.027), indicating reduced cold areas. Hot spot volume V105% were significantly reduced in Auto‐Plan by 14.4±7.2% (p=0.004). Absolute V105% was reduced from 395.6±359.9cc for Clinical‐Plans to 108.7±163cc for Auto‐Plans. D1cc was 107.4±2.8% for Auto‐Plans, and 109.2±2.4% for Clinical‐Plans (p=0.056). LungV20Gy were 13.6±4.0% for Auto‐Plan vs. 14.0±4.1% for Clinical‐Plans (p=0.043). All optimizations were finished within 1.5min.Conclusion:The performance of this breast auto‐planning system remained stable and satisfactory when applied to a different patient population and dose calculation algorithm. The auto‐planning system was able to produce clinically similar Rx dose coverage with significantly improved homogeneity inside breast tissue, in less than 1.5min.
SU‐C‐BRA‐03: An Automated and Quick Contour Errordetection for Auto Segmentation in Online Adaptive Radiotherapy
Authors: Zhang J , Ates O , Li X 
Published: July 2016

Purpose:To develop a tool that can quickly and automatically assess contour quality generated from auto segmentation during online adaptive replanning.Methods:Due to the strict time requirement of online replanning and lack of ‘ground truth’ contours in daily images, our method starts with assessing image registration accuracy focusing on the surface of the organ in question. Several metrics tightly related to registration accuracy including Jacobian maps, contours shell deformation, and voxel‐based root mean square (RMS) analysis were computed. To identify correct contours, additional metrics and an adaptive decision tree are introduced. To approve in principle, tests were performed with CT sets, planned and daily CTs acquired using a CT‐on‐rails during routine CT‐guided RT delivery for 20 prostate cancer patients. The contours generated on daily CTs using an auto‐segmentation tool (ADMIRE, Elekta, MIM) based on deformable image registration of the planning CT and daily CT were tested.Results:The deformed contours of 20 patients with total of 60 structures were manually checked as baselines. The incorrect rate of total contours is 49%. To evaluate the quality of local deformation, the Jacobian determinant (1.047±0.045) on contours has been analyzed. In an analysis of rectum contour shell deformed, the higher rate (0.41) of error contours detection was obtained compared to 0.32 with manual check. All automated detections took less than 5 seconds.Conclusion:The proposed method can effectively detect contour errors in micro and macro scope by evaluating multiple deformable registration metrics in a parallel computing process. Future work will focus on improving practicability and optimizing calculation algorithms and metric selection.
SU‐C‐BRA‐04: Automated Segmentation of Head‐And‐Neck CT Images for Radiotherapy Treatment Planning Via Multi‐Atlas Machine Learning (MAML)
Authors: Ren X , Sharp G , Gao H 
Published: July 2016

Purpose:Accurate image segmentation is a crucial step during image guided radiation therapy. This work proposes multi‐atlas machine learning (MAML) algorithm for automated segmentation of head‐and‐neck CT images.Methods:As the first step, the algorithm utilizes normalized mutual information as similarity metric, affine registration combined with multiresolution B‐Spline registration, and then fuses together using the label fusion strategy via Plastimatch. As the second step, the following feature selection strategy is proposed to extract five feature components from reference or atlas images: intensity (I), distance map (D), box (B), center of gravity (C) and stable point (S). The box feature B is novel. It describes a relative position from each point to minimum inscribed rectangle of ROI. The center‐of‐gravity feature C is the 3D Euclidean distance from a sample point to the ROI center of gravity, and then S is the distance of the sample point to the landmarks. Then, we adopt random forest (RF) in Scikit‐learn, a Python module integrating a wide range of state‐of‐the‐art machine learning algorithms as classifier. Different feature and atlas strategies are used for different ROIs for improved performance, such as multi‐atlas strategy with reference box for brainstem, and single‐atlas strategy with reference landmark for optic chiasm.Results:The algorithm was validated on a set of 33 CT images with manual contours using a leave‐one‐out cross‐validation strategy. Dice similarity coefficients between manual contours and automated contours were calculated: the proposed MAML method had an improvement from 0.79 to 0.83 for brainstem and 0.11 to 0.52 for optic chiasm with respect to multi‐atlas segmentation method (MA).Conclusion:A MAML method has been proposed for automated segmentation of head‐and‐neck CT images with improved performance. It provides the comparable result in brainstem and the improved result in optic chiasm compared with MA.Xuhua Ren and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000), and the Shanghai Pujiang Talent Program (#14PJ1404500).
SU‐C‐202‐01: Incorporating Time‐Dependent Hypoxia in IMRT Planning
Authors: Roy A , Nohadani O 
Published: July 2016

Purpose:To incorporate uncertainties in oxygenation of tumor cells into radiation therapy planning via robust optimization. The model is demonstrated using a clinical prostate cancer case.Methods:The tumor oxygenation levels are determined based on pre‐ and mid‐treatment PET scans. To account for oxygenation changes, we use a radio‐sensitivity factor for the effective dose necessary to treat hypoxic cells. Due to the unpredictable nature of re‐oxygenation of hypoxic cells, the radio‐sensitivity factor and its change is modeled to reside in a time‐dependent uncertainty set. This uncertainty can adapt to both pre‐ and mid‐treatment scans, resulting in a two‐stage robust treatment planning model. We develop a robust counterpart reformulation that transforms the original NP‐hard problem into a linear program consisting of finitely many linear constraints, which can be solved efficiently.Results:The robust plan is compared to both the corresponding fractionated plan which ignores hypoxia, and to the commonly practiced dose‐escalated plan that uniformly increases dose based on initial oxygen concentrations. For PTV, the robust plan improves D50, D95, and EUD by 4% on average compared to fractionated, and by 11% compared to the optimal escalated plan. Moreover, the robust plan spared organs at risk similar to the fractionated plan, while the escalated plan led to over 170% increase of Bladder D30.Conclusion:The proposed robust adaptive model can improve tumor coverage by increasing dose to hypoxic tumor voxels that is overlooked by common fractionated treatments. In addition, the robust model anticipates the re‐oxygenation process, thus reducing the excess dose at later fractions in comparison to uniform dose‐escalation methods.
SU‐C‐209‐03: Anti‐Scatter Grid‐Line Artifact Minimization for Removing the Grid Lines for Three Different Grids Used with a High Resolution CMOS Detector
Authors: Rana R , Bednarek D , Rudin S 
Published: July 2016

Purpose:Demonstrate the effectiveness of an anti‐scatter grid artifact minimization method by removing the grid‐line artifacts for three different grids when used with a high resolution CMOS detector.Method:Three different stationary x‐ray grids were used with a high resolution CMOS x‐ray detector (Dexela 1207, 75 µm pixels, sensitivity area 11.5cm × 6.5cm) to image a simulated artery block phantom (Nuclear Associates, Stenosis/Aneurysm Artery Block 76–705) combined with a frontal head phantom used as the scattering source. The x‐ray parameters were 98kVp, 200mA, and 16ms for all grids. With all the three grids, two images were acquired: the first for a scatter‐less flat field including the grid and the second of the object with the grid which may still have some scatter transmission. Because scatter has a low spatial frequency distribution, it was represented by an estimated constant value as an initial approximation and subtracted from the image of the object with grid before dividing by an average frame of the grid flat‐field with no scatter. The constant value was iteratively changed to minimize residual grid‐line artifact. This artifact minimization process was used for all the three grids.Results:Anti‐scatter grid lines artifacts were successfully eliminated in all the three final images taken with the three different grids. The image contrast and CNR were also compared before and after the correction, and also compared with those from the image of the object when no grid was used. The corrected images showed an increase in CNR of approximately 28%, 33% and 25% for the three grids, as compared to the images when no grid at all was used.Conclusion:Anti‐scatter grid‐artifact minimization works effectively irrespective of the specifications of the grid when it is used with a high spatial resolution detector.Partial support from NIH Grant R01‐EB002873 and Toshiba Medical Systems Corp.