bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐G‐TeP3‐14: Three‐Dimensional Cluster Model in Inhomogeneous Dose Distribution
Authors: Wei J , Penagaricano J , Narayanasamy G , Chao M 
Published: July 2016

Purpose:We aim to investigate 3D cluster formation in inhomogeneous dose distribution to search for new models predicting radiation tissue damage and further leading to new optimization paradigm for radiotherapy planning.Methods:The aggregation of higher dose in the organ at risk (OAR) than a preset threshold was chosen as the cluster whose connectivity dictates the cluster structure. Upon the selection of the dose threshold, the fractional density defined as the fraction of voxels in the organ eligible to be part of the cluster was determined according to the dose volume histogram (DVH). A Monte Carlo method was implemented to establish a case pertinent to the corresponding DVH. Ones and zeros were randomly assigned to each OAR voxel with the sampling probability equal to the fractional density. Ten thousand samples were randomly generated to ensure a sufficient number of cluster sets. A recursive cluster searching algorithm was developed to analyze the cluster with various connectivity choices like 1‐, 2‐, and 3‐connectivity. The mean size of the largest cluster (MSLC) from the Monte Carlo samples was taken to be a function of the fractional density. Various OARs from clinical plans were included in the study.Results:Intensive Monte Carlo study demonstrates the inverse relationship between the MSLC and the cluster connectivity as anticipated and the cluster size does not change with fractional density linearly regardless of the connectivity types. An initially‐slow‐increase to exponential growth transition of the MSLC from low to high density was observed. The cluster sizes were found to vary within a large range and are relatively independent of the OARs.Conclusion:The Monte Carlo study revealed that the cluster size could serve as a suitable index of the tissue damage (percolation cluster) and the clinical outcome of the same DVH might be potentially different.
SU‐G‐IeP4‐02: Application of Changs Attenuation Correction Technique for SPECT Partial Angle Acquisition of Jaszczak Phantom
Authors: Saha K , Barbarits J , Humenik R , Johnson J , Murray B , Hoyt S 
Published: July 2016

Purpose:Chang's mathematical formulation is a common method of attenuation correction applied on reconstructed Jaszczak phantom images. Though Chang's attenuation correction method has been used for 360° angle acquisition, its applicability for 180° angle acquisition remains a question with one vendor's camera software producing artifacts. The objective of this work is to ensure that Chang's attenuation correction technique can be applied for reconstructed Jaszczak phantom images acquired in both 360° and 180° mode.Methods:The Jaszczak phantom filled with 20 mCi of diluted Tc‐99m was placed on the patient table of Siemens e.cam™ (n = 2) and Siemens Symbia™ (n = 1) dual head gamma cameras centered both in lateral and axial directions. A total of 3 scans were done at 180° and 2 scans at 360° orbit acquisition modes. Thirty two million counts were acquired for both modes. Reconstruction of the projection data was performed using filtered back projection smoothed with pre reconstruction Butterworth filter (order: 6, cutoff: 0.55). Reconstructed transaxial slices were attenuation corrected by Chang's attenuation correction technique as implemented in the camera software. Corrections were also done using a modified technique where photon path lengths for all possible attenuation paths through a pixel in the image space were added to estimate the corresponding attenuation factor. The inverse of the attenuation factor was utilized to correct the attenuated pixel counts.Results:Comparable uniformity and noise were observed for 360° acquired phantom images attenuation corrected by the vendor technique (28.3% and 7.9%) and the proposed technique (26.8% and 8.4%). The difference in uniformity for 180° acquisition between the proposed technique (22.6% and 6.8%) and the vendor technique (57.6% and 30.1%) was more substantial.Conclusion:Assessment of attenuation correction performance by phantom uniformity analysis illustrated improved uniformity with the proposed algorithm compared to the camera software.
SU‐G‐IeP4‐03: Cone Beam X‐Ray Luminescence Computed Tomography Based On Generalized Gaussian Markov Random Field
Authors: Zhang G , Xing L 
Published: July 2016

Purpose:Cone beam X‐ray luminescence computed tomography (CB‐XLCT), which aims to achieve molecular and functional imaging by X‐rays, has recently been proposed as a new imaging modality. However, the inverse problem of CB‐XLCT is seriously ill‐conditioned, hindering us to achieve good image quality. In this work, a novel reconstruction method based on Bayesian theory is proposed to tackle this problemMethods:Bayesian theory provides a natural framework for utilizing various kinds of available prior information to improve the reconstruction image quality. A generalized Gaussian Markov random field (GGMRF) model is proposed here to construct the prior model of the Bayesian theory. The most important feature of GGMRF model is the adjustable shape parameter p, which can be continuously adjusted from 1 to 2. The reconstruction image tends to have more edge‐preserving property when p is slide to 1, while having more noise tolerance property when p is slide to 2, just like the behavior of L1 and L2 regularization methods, respectively. The proposed method provides a flexible regularization framework to adapt to a wide range of applications.Results:Numerical simulations were implemented to test the performance of the proposed method. The Digimouse atlas were employed to construct a three‐dimensional mouse model, and two small cylinders were placed inside to serve as the targets. Reconstruction results show that the proposed method tends to obtain better spatial resolution with a smaller shape parameter, while better signal‐to‐noise image with a larger shape parameter. Quantitative indexes, contrast‐to‐noise ratio (CNR) and full‐width at half‐maximum (FWHM), were used to assess the performance of the proposed method, and confirmed its effectiveness in CB‐XLCT reconstruction.Conclusion:A novel reconstruction method for CB‐XLCT is proposed based on GGMRF model, which enables an adjustable performance tradeoff between L1 and L2 regularization methods. Numerical simulations were conducted to demonstrate its performance.
SU‐G‐JeP4‐01: An Assessment of a Microsoft Kinect V2 Sensor for Voluntary Breath‐Hold Monitoring in Radiotherapy
Authors: Edmunds D , Donovan E 
Published: July 2016

Purpose:To determine whether the Microsoft Kinect Version 2 (Kinect v2), a commercial off‐the‐shelf (COTS) depth sensors designed for entertainment purposes, were robust to the radiotherapy treatment environment and could be suitable for monitoring of voluntary breath‐hold compliance. This could complement current visual monitoring techniques, and be useful for heart sparing left breast radiotherapy.Methods:In‐house software to control Kinect v2 sensors, and capture output information, was developed using the free Microsoft software development kit, and the Cinder creative coding C++ library. Each sensor was used with a 12m USB 3.0 active cable. A solid water block was used as the object. The depth accuracy and precision of the sensors was evaluated by comparing Kinect reported distance to the object with a precision laser measurement across a distance range of 0.6m to 2.0 m. The object was positioned on a high‐precision programmable motion platform and moved in two programmed motion patterns and Kinect reported distance logged. Robustness to the radiation environment was tested by repeating all measurements with a linear accelerator operating over a range of pulse repetition frequencies (6Hz to 400Hz) and dose rates 50 to 1500 monitor units (MU) per minute.Results:The complex, consistent relationship between true and measured distance was unaffected by the radiation environment, as was the ability to detect motion. Sensor precision was < 1 mm and the accuracy between 1.3 mm and 1.8 mm when a distance correction was applied. Both motion patterns were tracked successfully with a root mean squared error (RMSE) of 1.4 and 1.1 mm respectively.Conclusion:Kinect v2 sensors are capable of tracking pre‐programmed motion patterns with an accuracy <2 mm and appear robust to the radiotherapy treatment environment. A clinical trial using Kinect v2 sensor for monitoring voluntary breath hold has ethical approval and is open to recruitment.The authors are supported by a National Institute of Health Research (NIHR) Career Development Fellowship (CDF‐2013‐06‐005). Microsoft Corporation donated three sensors. The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.
SU‐G‐JeP4‐11: Prospective Treatment Plan‐Specific Action Limits for Real‐Time Intrafractional Monitoring in Surface Image Guided Radiosurgery
Authors: Yock A , Pawlicki T , Kim G 
Published: July 2016

Purpose:Surface image‐guided radiosurgery action limits are created to determine when intrafractional patient motion warrants intervention. Action limits remain constant across patients despite plan‐specific effects on brain metastases target coverage. The purpose of this work was twofold: 1) characterize the sensitivity of single‐met per iso and multi‐met per iso treatment plans to motion, and 2) describe a method to prospectively determine plan‐specific action limits considering this sensitivity.Methods:Seventy‐two brain metastases were used for this study. Twenty‐five were treated individually (“single‐met per iso plans”), and 47 were treated simultaneously with at least one other met (“multi‐met per iso plans”). For each met, the proportion of the gross tumor volume that remained within the 100% prescription isodose line after various combinations of translations and rotations (0.0–3.0 mm and 0.0–3.0°) was estimated. This was achieved using code developed in the Matlab environment that exhaustively evaluated the effects of all combinations of translations and rotations in this range. The target volume and the prescription dose volume were considered concentric spheres that encompassed volumes determined from the treatment plan. Plan‐specific contour plots and DVHs were created to illustrate the sensitivity of a specific lesion to motion.Results:Both single‐met per iso and multi‐met per iso plans exhibited compromised target coverage after transformations, though multi‐met per iso plans were considerably more sensitive to motion (2.3% and 39.8%, respectively). Plan‐specific contour plots and DVHs illustrate how size, distance from isocenter, and planning technique affect motion sensitivity.Conclusion:Stereotactic radiosurgery treatment plans that treat multiple brain metastases using a common isocenter are particularly susceptible to patient motion. This technique and other plan‐specific factors should influence motion management. A graphical representation of the sensitivity of any plan to motion can be generated to determine appropriate action limit.
SU‐G‐JeP4‐15: Feasibility Study of Tumor Monitoring Technique Using Prompt Gamma Rays During Antiproton Therapy
Authors: Shin H , Yoon D , Jung J , Kim M , Suh T 
Published: July 2016

Purpose:The purpose of this study is to suggest a tumor monitoring technique using prompt gamma rays emitted during the reaction between an antiproton and a boron particle, and to verify the increase of the therapeutic effectiveness of the antiproton boron fusion therapy using Monte Carlo simulation code.Methods:We acquired the percentage depth dose of the antiproton beam from a water phantom with and without three boron uptake regions (region A, B, and C) using F6 tally of MCNPX. The tomographic image was reconstructed using prompt gamma ray events from the reaction between the antiproton and boron during the treatment from 32 projections (reconstruction algorithm: MLEM). For the image reconstruction, we were performed using a 80 × 80 pixel matrix with a pixel size of 5 mm. The energy window was set as a 10 % energy window.Results:The prompt gamma ray peak for imaging was observed at 719 keV in the energy spectrum using the F8 tally fuction (energy deposition tally) of the MCNPX code. The tomographic image shows that the boron uptake regions were successfully identified from the simulation results. In terms of the receiver operating characteristic curve analysis, the area under the curve values were 0.647 (region A), 0.679 (region B), and 0.632 (region C). The SNR values increased as the tumor diameter increased. The CNR indicated the relative signal intensity within different regions. The CNR values also increased as the different of BURs diamter increased.Conclusion:We confirmed the feasibility of tumor monitoring during the antiproton therapy as well as the superior therapeutic effect of the antiproton boron fusion therapy. This result can be beneficial for the development of a more accurate particle therapy.
SU‐G‐TeP4‐03: A Multileaf Collimator Calibration and Quality Assurance Technique Using An Electronic Portal Imaging Device
Authors: Lebron S , Yan G , Li J , Lu B , Liu C 
Published: July 2016

Purpose:To develop an accurate and quick multileaf collimator (MLC) calibration and quality assurance technique using an electronic portal imaging device (EPID)Methods:The MLC models used include the MLCi and Agility (Elekta Ltd). This technique consists of two 22(L)x10(W) cm2 fields with 00 and 1800 collimator angles centered to an offset EPID. The MLC opening is estimated by calculating the profile at the image's center in the image's horizontal direction. Scans in the image's vertical direction were calculated every 20 pixels in the inner 70% of estimated MLC opening. The profiles’ edges were fitted with linear equations to determine the image's rotation angle. Then, crossline profiles were scanned at the center of each leaf taking into account the leaf's width at isocenter and the rotation angle. The profiles’ edges determine the location of the leaves’ edges and these were subtracted from the reference leaf's position in order to determine the relative leaf offsets. The edge location of all profiles was determined by using the parameterized gradient of the penumbra region. The technique was tested against an established diode array‐based method, and for different MLC systems, patterns, gantry angles, days, energies, beam modalities and MLC openings.Results:The differences between the proposed and established methods were 0.26±0.19mm. The leaf offsets’ deviation was <0.3mm (5 months period). For pattern fields, the differences between predetermined and calculated offsets were 0.18±0.18mm. The leaf offset deviation of measurements with different energies and MLC openings were <0.1mm and <0.3mm, respectively. The differences between offsets of FF and FFF beams were 0.01±0.02mm (<0.07mm). The differences between the offsets at different gantry angles were 0.08±0.15mm.Conclusion:The proposed method proved to be accurate and efficient in calculating the relative leaf offsets. Parameterized field edge is essential to obtain accurate result by eliminating the noise from EPID.
SU‐G‐TeP4‐04: An Automated Monte Carlo Based QA Framework for Pencil Beam Scanning Treatments
Authors: Shin J , Jee K , Clasie B , Depauw N , Madden T , Sharp G , Paganetti H , Kooy H 
Published: July 2016

Purpose:Prior to treating new PBS field, multiple (three) patient‐field‐specific QA measurements are performed: two 2D dose distributions at shallow depth (M1) and at the tumor depth (M2) with treatment hardware at zero gantry angle; one 2D dose distribution at iso‐center (M3) without patient specific devices at the planned gantry angle. This patient‐specific QA could be simplified by the use of MC model. The results of MC model commissioning for a spot‐scanning system and the fully automated TOPAS/MC‐based QA framework will be presented.Methods:We have developed in‐house MC interface to access a TPS (Astroid) database from a computer cluster remotely. Once a plan is identified, the interface downloads information for the MC simulations, such as patient images, apertures points, and fluence maps and initiates calculations in both the patient and QA geometries. The resulting calculations are further analyzed to evaluate the TPS dose accuracy and the PBS delivery.Results:The Monte Carlo model of our system was validated within 2.0 % accuracy over the whole range of the dose distribution (proximal/shallow part, as well as target dose part) due to the location of the measurements. The averaged range difference after commissioning was 0.25 mm over entire treatment ranges, e.g., 6.5 cm to 31.6 cm.Conclusion:As M1 depths range typically from 1 cm to 4 cm from the phantom surface, The Monte Carlo model of our system was validated within +− 2.0 % in absolute dose level over a whole treatment range. The averaged range difference after commissioning was 0.25 mm over entire treatment ranges, e.g., 6.5 cm to 31.6 cm.This work was supported by NIH/NCI under CA U19 21239
SU‐G‐TeP4‐10: Do Small Errors Matter When Treating Pituitary Adenoma Patients Using Gamma Knife?
Authors: Johnson P , Yang F , Lamichhane N 
Published: July 2016

Purpose:To determine whether positional errors on the order of 0.5–1 mm have any effect on critical structure dose or target coverage for pituitary adenoma patients treated with the Gamma Knife Perfexion.Methods:Treatment plans for six pituitary adenoma patients were modified to include positional shifts of 0.5 mm and 1 mm for each shot and in each cardinal direction. Twelve new plans were created per patient, and changes in target coverage and maximum dose to surrounding critical structures were recorded. Of particular interest were cases in which dose to the optic apparatus exceeded a tolerance of 8 Gy or dose to the brainstem exceeded a tolerance of 10–12 Gy. Target volumes ranged from 0.8–4.7 cc, and prescription doses ranged from 12–20 Gy.Results:Target coverage was significantly affected for only the smallest lesion. In this case, a shift of 1 mm in the superior or inferior direction resulted in a loss of coverage equal to 10%. A shift of 0.5 mm in the superior direction resulted in a loss of coverage equal to 4%. Critical structure tolerances were exceeded in 6/36 altered plans applying a 1 mm shift, and 3/36 altered plans applying a 0.5 mm shift. The increase in critical structure dose was between 2.0–2.7 Gy for these cases.Conclusion:In the world of radiosurgery accuracy is often quoted as sub‐millimeter. It is important to recognize, however, that even at this scale small errors can lead to situations where OAR tolerances are exceeded or target coverage is lost. The risk of such errors is dependent on the uncertainties involved with each step of the planning/treatment process. Future work will be devoted to better quantifying these uncertainties and defining the risk/benefit ratio for specific treatment approaches, i.e. margin vs no margin, optimization strategy, choice of prescription dose, etc.
SU‐G‐TeP4‐11: Implementation of a Non‐Measurement‐Based Patient‐Specific IMRT QA Program
Authors: Chen S , Guerrero M , Zhang B , Yi B , Mossahebi S , Prado K , D'Souza W , Langen K 
Published: July 2016

Purpose:To implement a comprehensive non‐measurement‐based verification program for patient‐specific IMRT QAMethods:Based on published guidelines, a robust IMRT QA program should assess the following components: 1) accuracy of dose calculation, 2) accuracy of data transfer from the treatment planning system (TPS) to the record‐and‐verify (RV) system, 3) treatment plan deliverability, and 4) accuracy of plan delivery.Results:We have implemented an IMRT QA program that consist of four components: 1) an independent re‐calculation of the dose distribution in the patient anatomy with a commercial secondary dose calculation program: Mobius3D (Mobius Medical Systems, Houston, TX), with dose accuracy evaluation using gamma analysis, PTV mean dose, PTV coverage to 95%, and organ‐at‐risk mean dose; 2) an automated in‐house‐developed plan comparison system that compares all relevant plan parameters such as MU, MLC position, beam iso‐center position, collimator, gantry, couch, field size settings, and bolus placement, etc. between the plan and the RV system; 3) use of the RV system to check the plan deliverability and further confirm using “mode‐up” function on treatment console for plans receiving warning; and 4) implementation of a comprehensive weekly MLC QA, in addition to routine accelerator monthly and daily QA. Among 1200 verifications, there were 9 cases of suspicious calculations, 5 cases of delivery failure, no data transfer errors, and no failure of weekly MLC QA. These 9 suspicious cases were due to the PTV extending to the skin or to heterogeneity correction effects, which would not have been caught using phantom measurement‐based QA. The delivery failure was due to the rounding variation of MLC position between the planning system and RV system.Conclusion:A very efficient, yet comprehensive, non‐measurement‐based patient‐specific QA program has been implemented and used clinically for about 18 months with excellent results
SU‐G‐TeP4‐12: Individual Beam QA for a Robotic Radiosurgery System Using a Scintillator Cone
Authors: McGuinness C , Descovich M , Sudhyadhom A 
Published: July 2016

Purpose:The targeting accuracy of the Cyberknife system is measured by end‐to‐end tests delivering multiple isocentric beams to a point in space. While the targeting accuracy of two representative beams can be determined by a Winston‐Lutz‐type test, no test is available today to determine the targeting accuracy of each clinical beam. We used a scintillator cone to measure the accuracy of each individual beam.Methods:The XRV‐124 from Logos Systems Int'l is a scintillator cone with an imaging system that is able to measure individual beam vectors and a resulting error between planned and measured beam coordinates. We measured the targeting accuracy of isocentric and non‐isocentric beams for a number of test cases using the Iris and the fixed collimator.Results:Collimator‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Num. Beams‐‐‐‐‐‐‐Avg. Diff. (mm)‐‐‐‐‐‐StDev. (mm)‐‐‐‐‐‐‐‐Max Diff. (mm)Fixed 10mm____________52___________0.837____________0.380___________1.73Iris 10mm______________52___________1.076____________0.433___________1.873Iris 12.5mm____________52___________1.232____________0.489___________2.043Iris 15mm______________52___________1.218____________0.475___________2.01Iris 20mm______________52___________1.202____________0.501___________2.508Iris 25mm______________52___________1.234____________0.494___________2.32Iris 30mm______________52___________1.096____________0.483___________2.433PlanQA Fixed 20mm______86___________0.900____________0.388___________1.667 PlanQA Iris 12.5–30mm___164__________0.806____________0.313___________1.571 The average difference between plan and measured beam position was 0.8–1.2mm across the collimator sizes and plans considered here. The max error for a single beam was 2.5mm for the isocentric plans, and 1.67mm for the non‐isocentric plans. The standard deviation of the differences was 0.5mm or less.Conclusion:The CyberKnife System is specified to have an overall targeting accuracy for static targets of less than 0.95mm. In E2E tests using the XRV124 system we measure average beam accuracy between 0.8 to 1.23mm, with maximum of 2.5mm. We plan to investigate correlations between beam position error and robot position, and to quantify the effect of beam position errors on patient specific plans.Martina Descovich has received research support and speaker honoraria from Accuray