bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐34: Setup Accuracy in Spine SBRT Using CBCT 6D Image Guidance in Comparison with 6D ExacTrac
Authors: Han Z , Yip S , Lewis J , Mannarino E , Friesen S , Wagar M , Hacker F 
Published: June 2015

PurposeVolumetric information of the spine captured on CBCT can potentially improve the accuracy in spine SBRT setup that has been commonly performed through 2D radiographs. This work evaluates the setup accuracy in spine SBRT using 6D CBCT image guidance that recently became available on Varian systems.MethodsExacTrac radiographs have been commonly used for Spine SBRT setup. The setup process involves first positioning patients with lasers followed by localization imaging, registration, and repositioning. Verification images are then taken providing the residual errors (ExacTracRE) before beam on. CBCT verification is also acquired in our institute. The availability of both ExacTrac and CBCT verifications allows a comparison study. 41 verification CBCT of 16 patients were retrospectively registered with the planning CT enabling 6D corrections, giving CBCT residual errors (CBCTRE) which were compared with ExacTracRE.ResultsThe RMS discrepancies between CBCTRE and ExacTracRE are 1.70mm, 1.66mm, 1.56mm in vertical, longitudinal and lateral directions and 0.27°, 0.49°, 0.35° in yaw, roll and pitch respectively. The corresponding mean discrepancies (and standard deviation) are 0.62mm (1.60mm), 0.00mm (1.68mm), −0.80mm (1.36mm) and 0.05° (0.58°), 0.11° (0.48°), −0.16° (0.32°). Of the 41 CBCT, 17 had high‐Z surgical implants. No significant difference in ExacTrac‐to‐CBCT discrepancy was observed between patients with and without the implants.ConclusionMultiple factors can contribute to the discrepancies between CBCT and ExacTrac: 1) the imaging iso‐centers of the two systems, while calibrated to coincide, can be different; 2) the ROI used for registration can be different especially if ribs were included in ExacTrac images; 3) small patient motion can occur between the two verification image acquisitions; 4) the algorithms can be different between CBCT (volumetric) and ExacTrac (radiographic) registrations.
SU‐E‐J‐35: Using CBCT as the Alternative Method of Assessing ITV Volume
Authors: Liao Y , Turian J , Templeton A , Redler G , Chu J 
Published: June 2015

PurposeTo study the accuracy of Internal Target Volumes (ITVs) created on cone beam CT (CBCT) by comparing the visible target volume on CBCT to volumes (GTV, ITV, and PTV) outlined on free breathing (FB) CT and 4DCT.MethodsA Quasar Cylindrical Motion Phantom with a 3cm diameter ball (14.14 cc) embedded within a cork insert was set up to simulate respiratory motion with a period of 4 seconds and amplitude of 2cm superioinferiorly and 1cm anterioposteriorly. FBCT and 4DCT images were acquired. A PTV‐4D was created on the 4DCT by applying a uniform margin of 5mm to the ITV‐CT. PTV‐FB was created by applying a margin of the motion range plus 5mm, i.e. total of 1.5cm laterally and 2.5cm superioinferiorly to the GTV outlined on the FBCT. A dynamic conformal arc was planned to treat the PTV‐FB with 1mm margin. A CBCT was acquired before the treatment, on which the target was delineated. During the treatment, the position of the target was monitored using the EPID in cine mode.ResultsITV‐CBCT and ITV‐CT were measured to be 56.6 and 62.7cc, respectively, with a Dice Coefficient (DC) of 0.94 and disagreement in center of mass (COM) of 0.59 mm. On the other hand, GTV‐FB was 11.47cc, 19% less than the known volume of the ball. PTV‐FB and PTV‐4D were 149 and 116 cc, with a DC of 0.71. Part of the ITV‐CT was not enclosed by the PTV‐FB despite the large margin. The cine EPID images have confirmed geometrical misses of the target. Similar under‐coverage was observed in one clinical case and captured by the CBCT, where the implanted fiducials moved outside PTV‐FB.ConclusionITV‐CBCT is in good agreement with ITV‐CT. When 4DCT was not available, CBCT can be an effective alternative in determining and verifying the PTV margin.
SU‐E‐J‐41: Is There An Optimal X‐Ray Technique for Prostate Treatment On CyberKnife?
Authors: Henderson E , Compuesto M , Gratton‐Liimatainen J 
Published: June 2015

PurposeTo establish guidelines for setting X‐ray technique for CyberKnife (Accuray) prostate treatments to keep imaging dose as low as reasonably achievable while maintaining consistent fiducial identification.MethodsFour gold seed fiducial markers were inserted into the prostate region of a Rando anthropomorphic phantom, following guidelines for fiducial placement provided by Accuray. A CT scan of the phantom was obtained using our standard clinical protocol and a treatment plan (Fiducial Tracking) was created. In order to simulate prostate treatment on the CyberKnife G4 (TDS v9.6), the phantom was aligned to within 0.2 degrees and 0.2mm of the planned position using X‐ray technique settings of 140kVp, 320mA and 100ms. The phantom was then shifted and rotated to 8 different positions. At each of these 8 positions, 5 orthogonal X‐ray image pairs were acquired at combinations of 3 kVp settings (110kVp, 125kVp, 140kVp), and 5 mAs settings (5mAs, 10mAs, 20mAs, 32mAs), and the frequency of the tracking software correctly identifying all four fiducials per technique setting was recorded. The experiment was repeated for three different simulated patient sizes by wrapping the phantom in layers of bolus.ResultsRegardless of phantom size, there were clear trends toward increased reliability of fiducial detection with increased X‐ray technique (both kVp and mAs), however gains achieved by increasing technique beyond 125kVp and 10mAs are modest. An increase in technique was increasingly ineffective in improving fiducial detection as the phantom was rotated away from the planned position (eg with increasing pitch). A dependence of tracking reliability on the planning DRRs was also noted.ConclusionThis method is a useful training tool for evaluating the effect of X‐ray technique on fiducial tracking. When fiducial tracking results are not reproducible, we recommend interventions such as eliminating an unreliable fiducial from tracking or adjusting patient position before increasing X‐ray technique.
SU‐E‐J‐45: The Correlation Between CBCT Flat Panel Misalignment and 3D Image Guidance Accuracy
Authors: Kenton O , Valdes G , Brousmiche S , Wikler D , Yin L , Teo B 
Published: June 2015

PurposeTo simulate the impact of CBCT flat panel misalignment on the image quality, the calculated correction vectors in 3D image guided proton therapy and to determine if these calibration errors can be caught in our QA process.MethodsThe X‐ray source and detector geometrical calibration (flexmap) file of the CBCT system in the AdaPTinsight software (IBA proton therapy) was edited to induce known changes in the rotational and translational calibrations of the imaging panel. Translations of up to ±10 mm in the x, y and z directions (see supplemental) and rotational errors of up to ±3° were induced. The calibration files were then used to reconstruct the CBCT image of a pancreatic patient and CatPhan phantom. Correction vectors were calculated for the patient using the software's auto match system and compared to baseline values. The CatPhan CBCT images were used for quantitative evaluation of image quality for each type of induced error.ResultsTranslations of 1 to 3 mm in the × and y calibration resulted in corresponding correction vector errors of equal magnitude. Similar 10mm shifts were seen in the y‐direction; however, in the x‐direction, the image quality was too degraded for a match. These translational errors can be identified through differences in isocenter from orthogonal kV images taken during routine QA. Errors in the z‐direction had no effect on the correction vector and image quality.Rotations of the imaging panel calibration resulted in corresponding correction vector rotations of the patient images. These rotations also resulted in degraded image quality which can be identified through quantitative image quality metrics.ConclusionMisalignment of CBCT geometry can lead to incorrect translational and rotational patient correction vectors. These errors can be identified through QA of the imaging isocenter as compared to orthogonal images combined with monitoring of CBCT image quality.
SU‐E‐J‐47: Comparison of Online Image Registrations of Varian TrueBeam Cone‐Beam CT and BrainLab ExacTrac Imaging Systems
Authors: Li J , Shi W , Andrews D , Werner‐Wasik M , Yu Y , Liu H 
Published: June 2015

PurposeTo compare online image registrations of TrueBeam cone‐beam CT (CBCT) and BrainLab ExacTrac imaging systems.MethodsTests were performed on a Varian TrueBeam STx linear accelerator (Version 2.0), which is integrated with a BrainLab ExacTrac imaging system (Version 6.0.5). The study was focused on comparing the online image registrations for translational shifts. A Rando head phantom was placed on treatment couch and immobilized with a BrainLab mask. The phantom was shifted by moving the couch translationally for 8 mm with a step size of 1 mm, in vertical, longitudinal, and lateral directions, respectively. At each location, the phantom was imaged with CBCT and ExacTrac x‐ray. CBCT images were registered with TrueBeam and ExacTrac online registration algorithms, respectively. And ExacTrac x‐ray image registrations were performed. Shifts calculated from different registrations were compared with nominal couch shifts.ResultsThe averages and ranges of absolute differences between couch shifts and calculated phantom shifts obtained from ExacTrac x‐ray registration, ExacTrac CBCT registration with default window, ExaxTrac CBCT registration with adjusted window (bone), Truebeam CBCT registration with bone window, and Truebeam CBCT registration with soft tissue window, were: 0.07 (0.02–0.14), 0.14 (0.01–0.35), 0.12 (0.02–0.28), 0.09 (0–0.20), and 0.06 (0–0.10) mm, in vertical direction; 0.06 (0.01–0.12), 0.27 (0.07–0.57), 0.23 (0.02–0.48), 0.04 (0–0.10), and 0.08 (0– 0.20) mm, in longitudinal direction; 0.05 (0.01–0.21), 0.35 (0.14–0.80), 0.25 (0.01–0.56), 0.19 (0–0.40), and 0.20 (0–0.40) mm, in lateral direction.ConclusionThe shifts calculated from ExacTrac x‐ray and TrueBeam CBCT registrations were close to each other (the differences between were less than 0.40 mm in any direction), and had better agreements with couch shifts than those from ExacTrac CBCT registrations. There were no significant differences between TrueBeam CBCT registrations using different windows. In ExacTrac CBCT registrations, using bone window led to better agreements than using default window.
SU‐E‐J‐144: Low Activity Studies of Carbon 11 Activation Via GATE Monte Carlo
Authors: Elmekawy A , Butuceanu C , Qu L , Ewell L 
Published: June 2015

Purpose:To investigate the behavior of a Monte Carlo simulation code with low levels of activity (∼1,000Bq). Such activity levels are expected from phantoms and patients activated via a proton therapy beam.Methods:Three different ranges for a therapeutic proton radiation beam were examined in a Monte Carlo simulation code: 13.5, 17.0 and 21.0cm. For each range, the decay of an equivalent length11C source and additional sources of length plus or minus one cm was studied in a benchmark PET simulation for activities of 1000, 2000 and 3000Bq. The ranges were chosen to coincide with a previous activation study, and the activities were chosen to coincide with the approximate level of isotope creation expected in a phantom or patient irradiated by a therapeutic proton beam. The GATE 7.0 simulation was completed on a cluster node, running Scientific Linux Carbon 6 (Red Hat©). The resulting Monte Carlo data were investigated with the ROOT (CERN) analysis tool. The half‐life of11C was extracted via a histogram fit to the number of simulated PET events vs. time.Results:The average slope of the deviation of the extracted carbon half life from the expected/nominal value vs. activity showed a generally positive value. This was unexpected, as the deviation should, in principal, decrease with increased activity and lower statistical uncertainty.Conclusion:For activity levels on the order of 1,000Bq, the behavior of a benchmark PET test was somewhat unexpected. It is important to be aware of the limitations of low activity PET images, and low activity Monte Carlo simulations.This work was funded in part by the Philips corporation.
SU‐E‐J‐175: Comparison of the Treatment Reproducibility of Tumors Affected by Breathing Motion
Authors: Adamczyk M , Piotrowski T , Adamczyk S 
Published: June 2015

Purpose:The aim of the dose distribution simulations was to form a global idea of intensity‐modulated radiation therapy (IMRT) realization, by its comparison to three‐dimensional conformal radiation therapy (3DCRT) delivery for tumors affected by respiratory motion.Methods:In the group of 10patients both 3DCRT and IMRT plans were prepared.For each field the motion kernel was generated with the largest movement amplitude of 4;6 and 8mm.Additionally,the sets of reference measurements were made in no motion conditions(0 mm).The evaluation of plan delivery,using a diode array placed on moving platform,was based on the Gamma Index analysis with distance to agreement of 3mm and dose difference of 3%.Results:IMRT plans tended to spare doses delivered to lungs compared to 3DCRT.Nonetheless,analyzed volumes showed no significant difference between the static and dynamic techniques,except for the volumes of both lungs receiving 10 and 15Gy.After adding the components associated with the respiratory movement,all IMRT lung parameters evaluated for the ipsilateral,contralateral and both lungs together,revealed considerable differences between the 0vs.6, 0vs.8 and 4vs.8‐mm amplitudes.Similar results were obtained for the 3DCRT lung measurements,but without significance between the 0vs.6‐mm amplitude.Taking into account the CTV score parameter in 3DCRT and IMRT plans,there was no statistically significant difference between the motion patterns with the smallest amplitudes.The differences were found for the 8‐mm amplitude when it was compared both with static conditions and 4‐mm amplitude (for 3DCRT) and between 0vs.6, 0vs.8 and 4vs.8‐mm amplitudes (for IMRT).All accepted and measured 3DCRT and IMRT doses to spinal cord,esophagus and heart were always below the QUANTEC limits.Conclusion:The application of IMRT technique in lung radiotherapy affords possibilities for reducing the lung doses.For maximal amplitudes of breathing trajectory below 4mm,the disagreement between CTV planned and delivered dose distribution can be neglected.Whereas respiratory motion with an amplitude above 5mm leads to significant changes in IMRT delivery.
SU‐E‐J‐182: Reproducibility of Tumor Motion Probability Distribution Function in Stereotactic Body Radiation Therapy of Lung Using Real‐Time Tumor‐Tracking Radiotherapy System
Authors: Shiinoki T , Kawamura S , Hanazawa H , Park S , Uehara T , Yuasa Y , Koike M , Takahashi T , Shibuya K 
Published: June 2015

Purpose:We aim to achieve new four‐dimensional radiotherapy (4DRT) using the next generation real‐time tumor‐tracking (RTRT) system and flattening‐filter‐free techniques. To achieve new 4DRT, it is necessary to understand the respiratory motion of tumor. The purposes of this study were: 1.To develop the respiratory motion analysis tool using log files. 2.To evaluate the reproducibility of tumor motion probability distribution function (PDF) during stereotactic body RT (SBRT) of lung tumor.Methods:Seven patients having fiducial markers closely implanted to the lung tumor were enrolled in this study. The positions of fiducial markers were measured using the RTRT system (Mitsubishi Electronics Co., JP) and recorded as two types of log files during the course of SBRT. For each patients, tumor motion range and tumor motion PDFs in left‐right (LR), anterior‐posterior (AP) and superior‐inferior (SI) directions were calculated using log files of all beams per fraction (PDFn). Fractional PDF reproducibility (Rn) was calculated as Kullback‐Leibler (KL) divergence between PDF1 and PDFn of tumor motion. The mean of Rn (Rm) was calculated for each patient and correlated to the patient's mean tumor motion range (Am). The change of Rm during the course of SBRT was also evluated. These analyses were performed using in‐house developed software.Results:The Rm were 0.19 (0.07–0.30), 0.14 (0.07–0.32) and 0.16 (0.09–0.28) in LR, AP and SI directions, respectively. The Am were 5.11 mm (2.58–9.99 mm), 7.81 mm (2.87–15.57 mm) and 11.26 mm (3.80–21.27 mm) in LR, AP and SI directions, respectively. The PDF reproducibility decreased as the tumor motion range increased in AP and SI direction. That decreased slightly through the course of RT in SI direction.Conclusion:We developed the respiratory motion analysis tool for 4DRT using log files and quantified the range and reproducibility of respiratory motion for lung tumors.
SU‐E‐J‐191: Motion Prediction Using Extreme Learning Machine in Image Guided Radiotherapy
Authors: Jia J , Cao R , Pei X , Wang H , Hu L 
Published: June 2015

Purpose:Real‐time motion tracking is a critical issue in image guided radiotherapy due to the time latency caused by image processing and system response. It is of great necessity to fast and accurately predict the future position of the respiratory motion and the tumor location.Methods:The prediction of respiratory position was done based on the positioning and tracking module in ARTS‐IGRT system which was developed by FDS Team (www.fds.org.cn). An approach involving with the extreme learning machine (ELM) was adopted to predict the future respiratory position as well as the tumor's location by training the past trajectories. For the training process, a feed‐forward neural network with one single hidden layer was used for the learning. First, the number of hidden nodes was figured out for the single layered feed forward network (SLFN). Then the input weights and hidden layer biases of the SLFN were randomly assigned to calculate the hidden neuron output matrix. Finally, the predicted movement were obtained by applying the output weights and compared with the actual movement. Breathing movement acquired from the external infrared markers was used to test the prediction accuracy. And the implanted marker movement for the prostate cancer was used to test the implementation of the tumor motion prediction.Results:The accuracy of the predicted motion and the actual motion was tested. Five volunteers with different breathing patterns were tested. The average prediction time was 0.281s. And the standard deviation of prediction accuracy was 0.002 for the respiratory motion and 0.001 for the tumor motion.Conclusion:The extreme learning machine method can provide an accurate and fast prediction of the respiratory motion and the tumor location and therefore can meet the requirements of real‐time tumor‐tracking in image guided radiotherapy.
SU‐E‐J‐193: Application of Surface Mapping in Detecting Swallowing for Head‐&‐Neck Cancer
Authors: Cao D , Xie X , Mehta V , Shepard D 
Published: June 2015

Purpose:Recent evidence is emerging that long term swallowing function may be improved after radiotherapy for head‐&‐neck cancer if doses are limited to certain swallowing structures. Immobilization of patients with head‐&‐neck cancer is typically done with a mask. This mask, however, doesn't limit patient swallowing. Patient voluntary or involuntary swallowing may introduce significant tumor motion, which can lead to suboptimal delivery. In this study, we have examined the feasibility of using surface mapping technology to detect patient swallowing during treatment and evaluated its magnitude.Methods:The C‐RAD Catalyst system was used to detect the patient surface map. A volunteer lying on the couch was used to simulate the patient under treatment. A virtual marker was placed near the throat and was used to monitor the swallowing action. The target motion calculated by the Catalyst system through deformable registration was also collected. Two treatment isocenters, one placed close to the throat and the other placed posterior to the base‐of‐tongue, were used to check the sensitivity of surface mapping technique.Results:When the patient's throat is not in the shadow of the patient's chest, the Catalyst system can clearly identify the swallowing motion. In our tests, the vertical motion of the skin can reach to about 5mm. The calculated target motion can reach up to 1 cm. The magnitude of this calculated target motion is more dramatic when the plan isocenter is closer to the skin surface, which suggests that the Catalyst motion tracking technique is more sensitive to the swallowing motion with a shallower isocenter.Conclusion:Surface mapping can clearly identify patient swallowing during radiation treatment. This information can be used to evaluate the dosimetric impact of the involuntary swallowing. It may also be used to potentially gate head‐&‐neck radiation treatments. A prospective IRB approved study is currently enrolling patients in our institution.Research was funded through an Elekta grant
SU‐E‐J‐208: Feasibility Study On Using Small Plastic Phantoms for Auditing Radiation Output of MR‐Linac Systems
Authors: Wen Z , Alvarez P , Ibbott G 
Published: June 2015

Purpose:To study feasibility of using small plastic phantoms designed for conventional linac output auditing to measure the output of MR‐Linac systems.Methods:For simulations, the CT scan of an IROC(formerly RPC) acrylic block phantom designed for 8 MV beams was imported in a research version of the treatment planning system (Monaco). Dose delivered to three TLDs in the block was calculated with a Monte Carlo algorithm and a beam model based on an MR‐linac prototype with and without a magnetic field (B=1.5T). In a large mathematical water phantom, the same beam was used to calculate dose in full scatter conditions. The block factor (F) was calculated as the ratio of the average dose to the block TLDs to the dose at the reference point in the mathematical phantom. For experimental measurement, four IROC blocks were irradiated with the MR‐linac prototype, and data were analyzed by IROC.Results:The F factor without a B field was 1.053. When a B field was applied, it changed the dose distribution in the block, especially on the edges. With a B field parallel to the long axes of the TLD, F was 1.038. However, with a perpendicular B field, F factor increased slightly to 1.075. In the IROC report, the output determined with two blocks parallel to the B field was 2.3% higher than the output by the two blocks perpendicular to the B field. The average of all four blocks was within 2% of machine output measured with an ion chamber.Conclusion:It may be feasible to expand the utility of the acrylic block phantoms for radiation output auditing from conventional linacs to MR‐linacs. However, the scatter correction factor can change due to the B field and its orientation to the block. More symmetric phantom designs may be less prone to mistakes.We acknowledge research support from Elekta