bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐350: Verification of Gating Performance of a New Elekta Gating Solution: Response Kit and Catalyst System
Authors: Xie X , Cao D , Housley D , Mehta V , Shepard D 
Published: July 2014

Purpose:In this work, we have tested the performance of new respiratory gating solutions for Elekta linacs. These solutions include the Response gating and the C‐RAD Catalyst surface mapping system.Verification measurements have been performed for a series of clinical cases. We also examined the beam on latency of the system and its impact on delivery efficiency.Methods:To verify the benefits of tighter gating windows, a Quasar Respiratory Motion Platform was used. Its vertical‐motion plate acted as a respiration surrogate and was tracked by the Catalyst system to generate gating signals. A MatriXX ion‐chamber array was mounted on its longitudinal‐moving platform. Clinical plans are delivered to a stationary and moving Matrix array at 100%, 50% and 30% gating windows and gamma scores were calculated comparing moving delivery results to the stationary result. It is important to note that as one moves to tighter gating windows, the delivery efficiency will be impacted by the linac's beam‐on latency. Using a specialized software package, we generated beam‐on signals of lengths of 1000ms, 600ms, 450ms, 400ms, 350ms and 300ms. As the gating windows get tighter, one can expect to reach a point where the dose rate will fall to nearly zero, indicating that the gating window is close to beam‐on latency. A clinically useful gating window needs to be significantly longer than the latency for the linac.Results:As expected, the use of tighter gating windows improved delivery accuracy. However, a lower limit of the gating window, largely defined by linac beam‐on latency, exists at around 300ms.Conclusion:The Response gating kit, combined with the C‐RAD Catalyst, provides an effective solution for respiratorygated treatment delivery. Careful patient selection, gating window design, even visual/audio coaching may be necessary to ensure both delivery quality and efficiency.This research project is funded by Elekta.
SU‐E‐T‐490: Clinical Analysis of the Approximate Multi‐Phase Biological Effective Dose (BED) Calculation
Authors: Kauweloa K , Gutierrez A , Bergamo A , Stathakis S , Papanikolaou N , Mavroidis P 
Published: July 2014

Purpose:An approximate, multi‐phase biological effective dose (BED) equation was introduced to simplify 3D‐BED calculations by treatment planning systems. The purpose of this work is to analyze its clinical accuracy within patients receiving two phase treatments (e.g., primary and boost phases).Methods:Twenty prostate and brain cancer patients were studied. MATLAB was used to calculate the true‐BED (BEDT) and approximate‐BED (BEDA), on a voxel‐basis within both phases, using the physical dose matrices that were exported from Pinnacle3 (Philips Medical, Fitchburg, WI). The data was analyzed using the percent error equation of BEDA with respect to BEDT. The Bland‐Altman Analysis and the Pearson's Correlation Coefficient were also used in order to study the impact of the dose distributions on the accuracy of BEDA.Results:It was shown that when the dose‐per‐fractions (DPF) between both phases were equal, the error was zero. Within brain cancer patients, 50 percent of the Optic Chiasms and Brainstems, 60–70 percent of the Left and Right Optic Nerves, and 80 percent of the Normal Brain and Spinal Cord had a BEDA with less than a 1 percent error. For prostate cancer patients, 60–70 percent of the Rectum and Bladder also had a BEDA with less than a 1 percent error. The BA‐Analysis and PCC also revealed the significant impact of the dose distribution and the locations of the OAR and target on the accuracy of BEDA.Conclusion:The results displayed accurate BEDA calculations in certain cases such as the Normal Brain, yet patients with large errors still existed. Due to the imprecision of BEDA on OARs, and the difficulty in predicting when it would be accurate, we recommend using BEDA only for targets due to a greater probability of seeing equivalent DPF values in both phases because of the homogeneous dose distributions delivered to the target volumes.
SU‐E‐T‐491: Importance of Energy Dependent Protons Per MU Calibration Factors in IMPT Dose Calculations Using Monte Carlo Technique
Authors: Randeniya S , Mirkovic D , Titt U , Guan F , Mohan R 
Published: July 2014

Purpose:In intensity modulated proton therapy (IMPT), energy dependent, protons per monitor unit (MU) calibration factors are important parameters that determine absolute dose values from energy deposition data obtained from Monte Carlo (MC) simulations. Purpose of this study was to assess the sensitivity of MC‐computed absolute dose distributions to the protons/MU calibration factors in IMPT.Methods:A “verification plan” (i.e., treatment beams applied individually to water phantom) of a head and neck patient plan was calculated using MC technique. The patient plan had three beams; one posterior‐anterior (PA); two anterior oblique. Dose prescription was 66 Gy in 30 fractions. Of the total MUs, 58% was delivered in PA beam, 25% and 17% in other two. Energy deposition data obtained from the MC simulation were converted to Gy using energy dependent protons/MU calibrations factors obtained from two methods. First method is based on experimental measurements and MC simulations. Second is based on hand calculations, based on how many ion pairs were produced per proton in the dose monitor and how many ion pairs is equal to 1 MU (vendor recommended method). Dose distributions obtained from method one was compared with those from method two.Results:Average difference of 8% in protons/MU calibration factors between method one and two converted into 27 % difference in absolute dose values for PA beam; although dose distributions preserved the shape of 3D dose distribution qualitatively, they were different quantitatively. For two oblique beams, significant difference in absolute dose was not observed.Conclusion:Results demonstrate that protons/MU calibration factors can have a significant impact on absolute dose values in IMPT depending on the fraction of MUs delivered. When number of MUs increases the effect due to the calibration factors amplify. In determining protons/MU calibration factors, experimental method should be preferred in MC dose calculations.Research supported by National Cancer Institute grant P01CA021239
SU‐E‐T‐492: Implementing a Method for Brain Irradiation in Rats Utilizing a Commercially Available Radiosurgery Irradiator
Authors: Cates J , Drzymala R 
Published: July 2014

Purpose:The purpose of the study was to implement a method for accurate rat brain irradiation using the Gamma Knife Perfexion unit. The system needed to be repeatable, efficient, and dosimetrically and spatially accurate.Methods:A platform (“rat holder”) was made such that it is attachable to the Leskell Gamma Knife G Frame. The rat holder utilizes two ear bars contacting bony anatomy and a front tooth bar to secure the rat. The rat holder fits inside of the Leskell localizer box, which utilizes fiducial markers to register with the GammaPlan planning system. This method allows for accurate, repeatable setup.A cylindrical phantom was made so that film can be placed axially in the phantom. We then acquired CT image sets of the rat holder and localizer box with both a rat and the phantom. Three treatment plans were created: a plan on the rat CT dataset, a phantom plan with the same prescription dose as the rat plan, and a phantom plan with the same delivery time as the rat plan.Results:Film analysis from the phantom showed that our setup is spatially accurate and repeatable. It is also dosimetrically accurate, with an difference between predicted and measured dose of 2.9%. Film analysis with prescription dose equal between rat and phantom plans showed a difference of 3.8%, showing that our phantom is a good representation of the rat for dosimetry purposes, allowing for +/‐ 3mm diameter variation. Film analysis with treatment time equal showed an error of 2.6%, which means we can deliver a prescription dose within 3% accuracy.Conclusion:Our method for irradiation of rat brain has been shown to be repeatable, efficient, and accurate, both dosimetrically and spatially. We can treat a large number of rats efficiently while delivering prescription doses within 3% at millimeter level accuracy.
SU‐E‐T‐495: Neutron Induced Electronics Failure Rate Analysis for a Single Room Proton Accelerator
Authors: Knutson N , DeWees T , Klein E 
Published: July 2014

Purpose:To determine the failure rate as a function of neutron dose of the range modulator's servo motor controller system (SMCS) while shielded with Borated Polyethylene (BPE) and unshielded in a single room proton accelerator.Methods:Two experimental setups were constructed using two servo motor controllers and two motors. Each SMCS was then placed 30 cm from the end of the plugged proton accelerator applicator. The motor was then turned on and observed from outside of the vault while being irradiated to known neutron doses determined from bubble detector measurements. Anytime the motor deviated from the programmed motion a failure was recorded along with the delivered dose. The experiment was repeated using 9 cm of BPE shielding surrounding the SMCS.Results:Ten SMCS failures were recorded in each experiment. The dose per monitor unit for the unshielded SMCS was 0.0211 mSv/MU and 0.0144 mSv/MU for the shielded SMCS. The mean dose to produce a failure for the unshielded SMCS was 63.5 ± 58.3 mSv versus 17.0 ±12.2 mSv for the shielded. The mean number of MUs between failures were 2297 ± 1891 MU for the unshielded SMCS and 2122 ± 1523 MU for the shielded. A Wilcoxon Signed Ranked test showed the dose between failures were significantly different (P value = 0.044) while the number of MUs between failures were not (P value = 1.000). Statistical analysis determined a SMCS neutron dose of 5.3 mSv produces a 5% chance of failure. Depending on the workload and location of the SMCS, this failure rate could impede clinical workflow.Conclusion:BPE shielding was shown to not reduce the average failure of the SMCS and relocation of the system outside of the accelerator vault was required to lower the failure rate enough to avoid impeding clinical work flow.
SU‐E‐T‐496: A Study of Two Commercial Dose Calculation Algorithms in Low Density Phantom
Authors: Lim S , Lovelock D , Yorke E , Kuo L , LoSasso T 
Published: July 2014

Purpose:Some lung cancer patients have very low lung density due to comorbidities. We investigate calculation accuracy of Eclipse AAA and Acuros(AXB) using a phantom that simulates this situation.Methods:A 2.5 x 5.0 x 5 cm (long) solid water inhomogeneity positioned 10 cm deep in a Balsa lung phantom (density 0.099 gm/cc) was irradiated with an off‐center field such that the central axis was parallel to one side of the inhomogeneity. Radiochromic films were placed at 2.5cm(S1) and 5cm(S2) depths. After CT scanning, Hounsfield Units(HU) were converted to electron(ρe) and mass(ρm) density using in‐house(IH) and vendor‐supplied(V) calibration curves. IH electron densities were generated using a commercial electron density phantom. The phantom was exposed to 6 MV 3×3 and 20×20 fields. Dose distributions were calculated using the AAA and AXB algorithms.Results:The HU of BW is ‐910±40 which translates to ρe of 0.088±0.050(IH) and 0.090±0.050(V), and ρm of 0.101±0.045(IH) and 0.103±0.039(V). Both ρe(V) and ρm(V) are higher than ρe(IH) and ρm(IH) respectively by 1.4‐5.3% and 0.5‐12.3%. The average calculated dose inside the solid water ‘tumor’ are within 3.7% and 2.4% of measurements for both calibrations and field sizes using AAA and AXB. Within 10mm outside the ‘tumor’, AAA on average underestimates by 18.3% and 17.0% respectively for 3×3 using IH and V. AXB underestimates by 5.9%(S1)‐6.6%(S2) and 13.1%(S1)‐16.0%(S2) respectively using IH and V. For 20×20, AAA and AXB underestimate by 2.8%(S1)‐4.4%(S2) and 0.3%(S1)‐1.4%(S2) respectively with either calibration.Conclusion:The difference in the HU calibration between V and IH is not of clinical significance in normal field sizes. In the low density region of small fields, the calculations from both algorithms differ significantly from measurements. This may be attributed to the insufficient lateral electron transport modeled by two algorithms resulting in the over‐estimation in penumbra expansion.
SU‐E‐T‐497: Semi‐Automated in Vivo Radiochromic Film Dosimetry Using a Novel Image Processing Algorithm
Authors: Reyhan M , Yue N 
Published: July 2014

Purpose:To validate an automated image processing algorithm designed to detect the center of radiochromic film used for in vivo film dosimetry against the current gold standard of manual selection.Methods:An image processing algorithm was developed to automatically select the region of interest (ROI) in *.tiff images that contain multiple pieces of radiochromic film (0.5×1.3cm2). After a user has linked a calibration file to the processing algorithm and selected a *.tiff file for processing, an ROI is automatically detected for all films by a combination of thresholding and erosion, which removes edges and any additional markings for orientation. Calibration is applied to the mean pixel values from the ROIs and a *.tiff image is output displaying the original image with an overlay of the ROIs and the measured doses. Validation of the algorithm was determined by comparing in vivo dose determined using the current gold standard (manually drawn ROIs) versus automated ROIs for n=420 scanned films. Bland‐Altman analysis, paired t‐test, and linear regression were performed to demonstrate agreement between the processes.Results:The measured doses ranged from 0.2‐886.6cGy. Bland‐Altman analysis of the two techniques (automatic minus manual) revealed a bias of ‐0.28cGy and a 95% confidence interval of (5.5cGy,‐6.1cGy). These values demonstrate excellent agreement between the two techniques. Paired t‐test results showed no statistical differences between the two techniques, p=0.98. Linear regression with a forced zero intercept demonstrated that Automatic=0.997*Manual, with a Pearson correlation coefficient of 0.999. The minimal differences between the two techniques may be explained by the fact that the hand drawn ROIs were not identical to the automatically selected ones. The average processing time was 6.7seconds in Matlab on an IntelCore2Duo processor.Conclusion:An automated image processing algorithm has been developed and validated, which will help minimize user interaction and processing time of radiochromic film used for in vivo dosimetry.
SU‐E‐T‐509: Validation of the Use of OSLD for Carbon Beam Remote Dosimetry
Authors: Summers P , Lowenstein J , Jakel O , Prokesch H , Alvarez P , Followill D 
Published: July 2014

Purpose:To describe the commissioning of Aluminum Oxide Optically Stimulated Luminescent Dosimeters (OSLD) for the use in Carbon beam remote dosimetry for centers participating in NCI‐funded cooperative group clinical trials.Methods:As Carbon therapy centers express interest in participating in cooperative group clinical trials, the Imaging and Radiation Oncology Core Group (IROC) Houston QA Center (formerly RPC) is developing a way to remotely monitor the machine output of these Carbon facilities. OSLD have been commissioned for photon, electron and proton dosimetry, so an experiment was designed to commission the same dosimeters for Carbon. OSLD were irradiated in a Carbon therapy beam produced by the Siemens synchrotron at the Heidelberg Ion Therapy facility in Heidelberg, Germany. The OSLD were placed in acrylic phantoms, imaged with a CT scanner, and plans were developed using the Siemens treatment planning system. The OSLD were irradiated in uniform fields with maximum energies of 216, 301, and 402 MeV and at dose levels of 50, 100, 200 and 300 cGy.Results:The response of the OSLD in the Carbon beam, as compared to the Cobalt‐60 reference condition, required an energy correction of 1.85 to account for the particle correction. OSLD dose calculations typically have a linearity correction to account for the change in response relative to the change in dose delivered. However, the response of the OSLD in the Carbon beam was found to be independent of the dose level; thus the linearity correction is 1.00.Conclusion:IROC Houston has commissioned OSLD for the use of remote output checks for Carbon therapy facilities to help ensure consistency across clinical trial participants.Work supported by grant CA10953 (NCI, DHHS).
SU‐E‐T‐510: Mathematical Analysis of Approximate Biological Effective Dose (BED) Calculation for Multi‐Phase Radiotherapy Treatment Plans
Authors: Kauweloa K , Gutierrez A , Bergamo A , Stathakis S , Papanikolaou N , Mavroidis P 
Published: July 2014

Purpose:There is growing interest about biological effective dose (BED) and its application in treatment plan evaluation due to its stronger correlation with treatment outcome. An approximate biological effective dose (BEDA) equation was introduced to simplify BED calculations by treatment planning systems in multi‐phase treatments. The purpose of this work is to reveal its mathematical properties relative to the true, multi‐phase BED (BEDT) equation.Methods:The BEDT equation was derived and used to reveal the mathematical properties of BEDA. MATLAB (MathWorks, Natick, MA) was used to simulate and analyze common and extreme clinical multi‐phase cases. In those cases, percent error (Perror) and Bland‐Altman analysis were used to study the significance of the inaccuracies of BEDA for different combinations of total doses, numbers of fractions, doses per fractions and α over β values. All the calculations were performed on a voxel‐basis in order to study how dose distributions would affect the accuracy of BEDA.Results:When the voxel dose‐per‐fractions (DPF) delivered by both phases are equal, BEDA and BEDT are equal. In heterogeneous dose distributions, which significantly vary between the phases, there are fewer occurrences of equal DPFs and hence the imprecision of BEDA is greater. It was shown that as the α over β ratio increased the accuracy of BEDA would improve. Examining twenty‐four cases, it was shown that the range of DPF ratios for a 3 Perror varied from 0.32 to 7.50Gy, whereas for Perror of 1 the range varied from 0.50 to 2.96Gy.Conclusion:The DPF between the different phases should be equal in order to render BEDA accurate. OARs typically receive heterogeneous dose distributions hence the probability of equal DPFs is low. Consequently, the BEDA equation should only be used for targets or OARs that receive uniform or very similar dose distributions by the different treatment phases.
SU‐E‐T‐520: Four‐Dimensional Dose Calculation Algorithm Considering Variations in Dose Distribution Induced by Sinusoidal One‐Dimensional Motion Patterns
Authors: Taguenang J , Algan O , Ahmad S , Ali I 
Published: July 2014

Purpose:To investigate quantitatively the variations in dose‐distributions induced by motion by measurements and modeling. A four‐dimensional (4D) motion model of dose distributions that accounts for different motion parameters was developed.Methods:Variations in dose distributions induced by sinusoidal phantom motion were measured using a multiple‐diode‐array‐detector (MapCheck2). MapCheck2 was mounted on a mobile platform that moves with adjustable calibrated motion patterns in the superior‐inferior direction. Various plans including open and intensity‐modulated fields were used to irradiate MapCheck2. A motion model was developed to predict spatial and temporal variations in the dose‐distributions and dependence on the motion parameters using pencil‐beam spread‐out superposition function. This model used the superposition of pencil‐beams weighted with a probability function extracted from the motion trajectory. The model was verified with measured dose‐distributions obtained from MapCheck2.Results:Dose‐distribution varied considerably with motion where in the regions between isocenter and 50% isodose‐line, dose decreased with increase of the motion amplitude. Dose levels increased with increase in the motion amplitude in the region beyond 50% isodose‐line. When the range of motion (ROM=twice amplitude) was smaller than the field length both central axis dose and the 50% isodose‐line did not change with variation of motion amplitude and remained equal to the dose of stationary phantom. As ROM became larger than the field length, the dose level decreased at central axis dose and 50% isodose‐line. Motion frequency and phase did not affect the dose distributions which were delivered over an extended time longer than few motion cycles, however, they played an important role for doses delivered with high‐dose‐rates within one motion cycle .Conclusion:A 4D‐dose motion model was developed to predict and correct variations in dose distributions induced by one‐dimensional sinusoidal motion. This model was verified with measured dose‐distributions and can be expanded to consider complicated patient motion patterns.
SU‐E‐T‐529: Study of Second Cancer Risk in the Treatment of Multiple Lung Lesion by SBRT Using Rapid Arc: Comparison Between Different Treatment Planning Parameters
Authors: Sakthivel V , Ganesh K , Mani S , Boopathy R 
Published: July 2014

Purpose:To compare the secondary cancer risk (SCR) between different plan settings (Collimator angle, number of Arcs and manual jaw opening) for Rapid Arc plan in the treatment of multiple lung lesion.Methods:Patient with multiple lung lesion was planned with single isocenter (i) single arc (CW:200‐160deg) and (ii) dual complementary arc. The plans were optimized to yield similar plan evaluation/acceptance criteria. The concept of equivalent OED (linear‐exponential, plateau, and the linear dose– response model) was used to evaluate the Second Cancer Risk (SCR). Then, the single arc plan was generated using five different collimator setting (0,30,45,90,120 deg) and the OED was analyzed. Also, plans were generated with automatic jaw setting and compared against the manual jaw setting.Results:The SCR values were normalized to the single arc plan. For dual complementary arc, the relative SCR for Rt.lung were (linear, plateau, linear‐exponential) (1.02,1.05,1.04), (0.99,1.02,1.02) for Lt.lung, (1.01,1.07,1.06) for Spinal cord, (1.18,1.1,1.09) for Esophagus, (1.3,1.19,1.16) for Heart, (1,1.01,1.02) for Lt.Breast and (1.05,1.05,1.05) for Rt.Breast. Since the single arc plan was superior in terms of SCR further analysis was carried out for various collimator angles. The low dose bath volumes 5Gy in cc for single and dual arc plans were 5468 and 5886 cc respectively. The computed OED values (linear‐exponential) for Rt.Lung were (1,0.94,0.96,1.06,0.97), (1,0.89,0.97,1.11,0.9) for Lt.Lung, (1,0.86,0.98,1.2,0.92) for Spinal cord, (1,0.87,0.99,1.15,0.91) for esophagus, (1,0.88,1.01,1.11,0.94) for heart, (1,0.83,0.97,1.20,0.86) for lt.breast and (1,0.94,0.95,1.03,1.11) for Rt.breast for collimator setting (0,30,45,90,120 deg) respectively.Conclusion:The Second cancer risk is considerably high for dual arc plan compared with single arc. In single arc plan the 30 degree collimator angle plan showed the least OED values for all critical structures, with the 90 degree collimator angle being the most. No significant difference between the manual and the automatic jaw setting plans were found.
A Weak Convergence to Hermite Process by Martingale Differences
Authors: Sun Xichao , Cheng Ronglong 
Published: July 2014

We consider the weak convergence to general Hermite processZH,kof orderkwith indexH. By applying martingale differences we construct a sequence{ZH,kn ,  n=1,2,…}of multiple Wiener-Itô stochastic integrals such that it converges in distribution to the Hermite processZH,k.