bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐41: Experimental Validation of a Cascaded Linear System Model for MVCBCT with a Multi‐Layer EPID
Authors: Hu Y , Fueglistaller R , Rottmann J , Myronakis M , Wang A , Shedlock D , Morf D , Star‐Lack J , Berbeco R 
Published: July 2016

Purpose:The purpose of this study was to validate the use of a cascaded linear system model for MV cone‐beam CT (CBCT) using a multi‐layer (MLI) electronic portal imaging device (EPID) and provide experimental insight into image formation. A validated 3D model provides insight into salient factors affecting reconstructed image quality, allowing potential for optimizing detector design for CBCT applications.Methods:A cascaded linear system model was developed to investigate the potential improvement in reconstructed image quality for MV CBCT using an MLI EPID. Inputs to the three‐dimensional (3D) model include projection space MTF and NPS. Experimental validation was performed on a prototype MLI detector installed on the portal imaging arm of a Varian TrueBeam radiotherapy system. CBCT scans of up to 898 projections over 360 degrees were acquired at exposures of 16 and 64 MU. Image volumes were reconstructed using a Feldkamp‐type (FDK) filtered backprojection (FBP) algorithm. Flat field images and scans of a Catphan model 604 phantom were acquired. The effect of 2×2 and 4×4 detector binning was also examined.Results:Using projection flat fields as an input, examination of the modeled and measured NPS in the axial plane exhibits good agreement. Binning projection images was shown to improve axial slice SDNR by a factor of approximately 1.4. This improvement is largely driven by a decrease in image noise of roughly 20%. However, this effect is accompanied by a subsequent loss in image resolution.Conclusion:The measured axial NPS shows good agreement with the theoretical calculation using a linear system model. Binning of projection images improves SNR of large objects on the Catphan phantom by decreasing noise. Specific imaging tasks will dictate the implementation image binning to two‐dimensional projection images.The project was partially supported by a grant from Varian Medical Systems, Inc. and grant No. R01CA188446‐01 from the National Cancer Institute.
SU‐F‐J‐44: Development of a Room Laser Based Real‐Time Alignment Monitoring System Using An Array of Photodiodes
Authors: Noh Y , Kim S , Kim T , Kang S , Kim D , Cho M , Kim K , Shin D , Suh T 
Published: July 2016

Purpose:To develop a real‐time alignment monitoring system (RAMS) to compensate for the limitations of the conventional room laser based alignment system, and to verify the feasibility of the RAMS.Methods:The RAMS was composed of a room laser sensing array (RLSA), an analog‐todigital converter, and a control PC. In the RLSA, seven photodiodes (each in 1 mm width) are arranged in a pattern that the RAMS provides alignment in 1 mm resolution. It works based on detecting laser light aligned on one of photodiodes. When misaligned, the laser would match with different photodiode(s) giving signal at unexpected location. Thus, how much displaced can be determined. To verify the reproducibility of the system with respect to time as well as repeated set‐ups, temporal reproducibility and repeatability test was conducted. The accuracy of the system was tested by obtaining detection signals with varying laser‐match positions.Results:The signal of the RAMS was found to be stable with respect to time. The repeatability test resulted in a maximum coefficient of variance of 1.14%, suggesting that the signal of the RAMS was stable over repeated set‐ups. In the accuracy test, signals between when the laser was aligned and notaligned with any of sensors could be distinguished by signal intensity. The signals of not‐aligned sensors were always below 75% of the signal of the aligned sensor. It was confirmed that the system could detect 1 mm of movement by monitoring the pattern of signals, and could observe the movement of the system in real‐time.Conclusion:We developed a room laser based alignment monitoring system. The feasibility test verified that the system is capable of quantitative alignment monitoring in real time. The system is relatively simple, not expensive, and considered to be easily incorporated into conventional room laser systems for real‐time alignment monitoring.This research was supported by the Mid‐career Researcher Program through NRF funded by the Ministry of Science, ICT & Future Planning of Korea (NRF‐2014R1A2A1A10050270) and by the Radiation Technology R&D program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (No. 2013M2A2A7038291)
SU‐F‐J‐45: Sparing Normal Tissue with Ultra‐High Dose Rate in Radiation Therapy
Authors: Feng Y 
Published: July 2016

Purpose:To spare normal tissue by reducing the location uncertainty of a moving target, we proposed an ultra‐high dose rate system and evaluated.Methods:High energy electrons generated with a linear accelerator were injected into a storage ring to be accumulated. The number of the electrons in the ring was determined based on the prescribed radiation dose. The dose was delivered within a millisecond, when an online imaging system found that the target was in the position that was consistent with that in a treatment plan. In such a short time period, the displacement of the target was negligible. The margin added to the clinical target volume (CTV) could be reduced that was evaluated by comparing of volumes between CTV and ITV in 14 cases of lung stereotactic body radiation therapy (SBRT) treatments. A design of the ultra‐high dose rate system was evaluated based clinical needs and the recent developments of low energy (a few MeV) electron storage ring.Results:This design of ultra‐high dose rate system was feasible based on the techniques currently available. The reduction of a target volume was significant by reducing the margin that accounted the motion of the target. ∼50% volume reduction of the internal target volume (ITV) could be achieved in lung SBRT treatments.Conclusion:With this innovation of ultra‐high dose rate system, the margin of target is able to be significantly reduced. It will reduce treatment time of gating and allow precisely specified gating window to improve the accuracy of dose delivering.
SU‐F‐J‐47: Inherent Uncertainty in the Positional Shifts Determined by a Volumetric Cone Beam Imaging System
Authors: Giri U , Ganesh T , Saini V , Munshi A , Sarkar B , Mohanti B 
Published: July 2016

Purpose:To quantify inherent uncertainty associated with a volumetric imaging system in its determination of positional shifts.Methods:The study was performed on an Elekta Axesse™ linac's XVI cone beam computed tomography (CBCT) system. A CT image data set of a Penta‐ Guide phantom was used as reference image by placing isocenter at the center of the phantom.The phantom was placed arbitrarily on the couch close to isocenter and CBCT images were obtained. The CBCT dataset was matched with the reference image using XVI software and the shifts were determined in 6‐dimensions. Without moving the phantom, this process was repeated 20 times consecutively within 30 minutes on a single day. Mean shifts and their standard deviations in all 6‐dimensions were determined for all the 20 instances of imaging. For any given day, the first set of shifts obtained was kept as reference and the deviations of the subsequent 19 sets from the reference set were scored. Mean differences and their standard deviations were determined. In this way, data were obtained for 30 consecutive working days.Results:Tabulating the mean deviations and their standard deviations observed on each day for the 30 measurement days, systematic and random errors in the determination of shifts by XVI software were calculated. The systematic errors were found to be 0.03, 0.04 and 0.03 mm while random errors were 0.05, 0.06 and 0.06 mm in lateral, craniocaudal and anterio‐posterior directions respectively. For rotational shifts, the systematic errors were 0.02°, 0.03° and 0.03° and random errors were 0.06°, 0.05° and 0.05° in pitch, roll and yaw directions respectively.Conclusion:The inherent uncertainties in every image guidance system should be assessed and baseline values established at the time of its commissioning. These shall be periodically tested as part of the QA protocol.
SU‐F‐J‐49: IGRT Credentialing in NCTN Trials
Authors: Lowenstein J , Molineu A , Al‐Hallaq H , Matuszak M , Craig T , Ulin K , Xiao Y , Yin F , Followill D 
Published: July 2016

Purpose:To make Image Guided Radiation Therapy (IGRT) credentialing a more unified, consistent and efficient process across the entire National Clinical Trial Network (NCTN).Methods:IGRT plays a role in several advanced NCTN trials. Previously an institution had to be IGRT credentialed for each protocol. When institutions were allowed to use previous credentials for new protocols it was limited to the same disease site as the original credentialing. The credentialing was analyzed by the physics PI of the protocol. We consulted with several of these physicists to determine what is important to consider when reviewing submissions and to learn ways to apply credentialing more broadly.Results:For trials open in 2016, IGRT credentialing can be simplified to cover either boney anatomy or soft tissue. This revised credentialing will cover all disease sites based on the type of anatomy, unless otherwise stated within the protocol. Institutions will submit will complete an online questionnaire about their IGRT procedures. Boney anatomy requirements will include submission of data from 2 sequential fraction of both a patient aligned with boney anatomy and pelvic patient. Soft tissue will require similar submissions for a patient aligned using soft tissue and a pelvic patient. Institutions will only be required to submit the pelvic patient once. Data should be in DICOM format and includes planning CT set, RT structure set, RT plan file, RT dose file, localization images and spatial registration file (if available). Reviews will be done by IROC‐Houston staff who will continue to provide feedback to the sites.Conclusion:This revised IGRT credentialing process will bring consistency, a savings in time and effort for both the IROC Houston QA office and to those institutions wanting to be credentialed to participate in NCTN Trials.Sponsored by NIH/NCI CA10953
SU‐F‐J‐53: A 3D Printed Phantom for the Use of Daily Quality Assurance Alignment Tests
Authors: Woods K , Ayan A , Woollard J , Gardner N , Gupta N 
Published: July 2016

Purpose:To discuss experiences and results for a 3D printed QA phantom used for daily alignment purposes for a six degrees‐of‐freedom (6DoF) tableMethods:A 3D model was created using a fused deposition modeling (FDM) printer using free online computer‐aided design (CAD) software. The model has been under use for daily QA alignment tests for a 6DoF couch. An aligned and angled baseplate were also printed in order to introduce known angles for 6DoF corrections during image‐guidance. Unique registration contours were created on the faces of the phantom in order to achieve a better cone‐beam computed tomography (CBCT) match using an auto‐registration algorithm. A BB was also introduced at the center of the phantom in order to deliver an integrated daily Winston‐Lutz (WL) test. Translational, rotational, and WL results were tabulated over one month.Results:The 'honeycomb’ structure of the print was apparent in the EPID images for the WL test, which affected the results of the analysis software. This was fixed by inserting a cube made of polyoxymethylene within the 3D phantom that encompass the BB. Auto‐registration results for the three translational and three rotational from a known offset to the BB isocenter consistently fell within 1 mm and 0.2°, respectively. WL tests resulted in an average of 0.71 ± 0.14 mm.Conclusion:3D printed models allow for accurate builds that can be customized to a variety of clinical needs. Results from translational, rotational, and WL show consistent results over a month's time. Given its relatively cheap and streamlined workflow, 3D printing could be implemented into any clinic looking to create customized phantoms.
SU‐F‐J‐55: Feasibility of Supraclavicular Field Treatment by Investigating Variation of Junction Position Between Breast Tangential and Supraclavicular Fields for Deep Inspiration Breath Hold (DIBH) Left Breast Radiation
Authors: Zhao H , Sarkar V , Paxton A , Rassiah‐Szegedi P , Huang Y , Szegedi M , Huang L , Su F , Salter B 
Published: July 2016

Purpose:To explore the feasibility of supraclavicular field treatment by investigating the variation of junction position between tangential and supraclavicular fields during left breast radiation using DIBH technique.Methods:Six patients with left breast cancer treated using DIBH technique were included in this study. AlignRT system was used to track patient's breast surface. During daily treatment, when the patient's DIBH reached preset AlignRT tolerance of ±3mm for all principle directions (vertical, longitudinal, and lateral), the remaining longitudinal offset was recorded. The average with standard‐deviation and the range of daily longitudinal offset for the entire treatment course were calculated for all six patients (93 fractions totally). The ranges of average ± 1σ and 2σ were calculated, and they represent longitudinal field edge error with the confidence level of 68% and 95%. Based on these longitudinal errors, dose at junction between breast tangential and supraclavicular fields with variable gap/overlap sizes was calculated as a percentage of prescription (on a representative patient treatment plan).Results:The average of longitudinal offset for all patients is 0.16±1.32mm, and the range of longitudinal offset is −2.6 to 2.6mm. The range of longitudinal field edge error at 68% confidence level is −1.48 to 1.16mm, and at 95% confidence level is −2.80 to 2.48mm. With a 5mm and 1mm gap, the junction dose could be as low as 37.5% and 84.9% of prescription dose; with a 5mm and 1mm overlap, the junction dose could be as high as 169.3% and 117.6%.Conclusion:We observed longitudinal field edge error at 95% confidence level is about ±2.5mm, and the junction dose could reach 70% hot/cold between different DIBH. However, over the entire course of treatment, the average junction variation for all patients is within 0.2mm. The results from our study shows it is potentially feasible to treat supraclavicular field with breast tangents.
SU‐F‐J‐56: The Connection Between Cherenkov Light Emission and Radiation Absorbed Dose in Proton Irradiated Phantoms
Authors: Darafsheh A , Taleei R , Kassaee A , Finlay J 
Published: July 2016

Purpose:Range verification in proton therapy is of great importance. Cherenkov light follows the photon and electron energy deposition in water phantom. The purpose of this study is to investigate the connection between Cherenkov light generation and radiation absorbed dose in a water phantom irradiated with proton beams.Methods:Monte Carlo simulation was performed by employing FLUKA Monte Carlo code to stochastically simulate radiation transport, ionizing radiation dose deposition, and Cherenkov radiation in water phantoms. The simulations were performed for proton beams with energies in the range 50–600 MeV to cover a wide range of proton energies.Results:The mechanism of Cherenkov light production depends on the initial energy of protons. For proton energy with 50–400 MeV energy that is below the threshold (∼483 MeV in water) for Cherenkov light production directly from incident protons, Cherenkov light is produced mainly from the secondary electrons liberated as a result of columbic interactions with the incident protons. For proton beams with energy above 500 MeV, in the initial depth that incident protons have higher energy than the Cherenkov light production threshold, the light has higher intensity. As the slowing down process results in lower energy protons in larger depths in the water phantom, there is a knee point in the Cherenkov light curve vs. depth due to switching the Cherenkov light production mechanism from primary protons to secondary electrons. At the end of the depth dose curve the Cherenkov light intensity does not follow the dose peak because of the lack of high energy protons to produce Cherenkov light either directly or through secondary electrons.Conclusion:In contrast to photon and electron beams, Cherenkov light generation induced by proton beams does not follow the proton energy deposition specially close to the end of the proton range near the Bragg peak.
SU‐F‐J‐57: Effectiveness of Daily CT‐Based Three‐Dimensional Image Guided and Adaptive Proton Therapy
Authors: Moriya S , Tachibana H , Hotta K , Nakamura N , Baba H , Kohno R , Miyakawa S , Kurosawa T , Akimoto T 
Published: July 2016

Purpose:Daily CT‐based three‐dimensional image‐guided and adaptive (CTIGRT‐ART) proton therapy system was designed and developed. We also evaluated the effectiveness of the CTIGRT‐ART.Methods:Retrospective analysis was performed in three lung cancer patients: Proton treatment planning was performed using CT image datasets acquired by Toshiba Aquilion ONE. Planning target volume and surrounding organs were contoured by a well‐trained radiation oncologist. Dose distribution was optimized using 180‐deg. and 270‐deg. two fields in passive scattering proton therapy. Well commissioned Simplified Monte Carlo algorithm was used as dose calculation engine. Daily consecutive CT image datasets was acquired by an in‐room CT (Toshiba Aquilion LB). In our in‐house program, two image registrations for bone and tumor were performed to shift the isocenter using treatment CT image dataset. Subsequently, dose recalculation was performed after the shift of the isocenter. When the dose distribution after the tumor registration exhibits change of dosimetric parameter of CTV D90% compared to the initial plan, an additional process of was performed that the range shifter thickness was optimized. Dose distribution with CTV D90% for the bone registration, the tumor registration only and adaptive plan with the tumor registration was compared to the initial plan.Results:In the bone registration, tumor dose coverage was decreased by 16% on average (Maximum: 56%). The tumor registration shows better coverage than the bone registration, however the coverage was also decreased by 9% (Maximum: 22%) The adaptive plan shows similar dose coverage of the tumor (Average: 2%, Maximum: 7%).Conclusion:There is a high possibility that only image registration for bone and tumor may reduce tumor coverage. Thus, our proposed methodology of image guidance and adaptive planning using the range adaptation after tumor registration would be effective for proton therapy.This research is partially supported by Japan Agency for Medical Research and Development (AMED).
SU‐F‐J‐58: Evaluation of RayStation Hybrid Deformable Image Registration for Accurate Contour Propagation in Adaptive Planning
Authors: Rong Y , Rao S , Daly M , Wright C , Benedict S , Yamamoto T 
Published: July 2016

Purpose:Adaptive radiotherapy requires complete new sets of regions of interests (ROIs) delineation on the mid‐treatment CT images. This work aims at evaluating the accuracy of the RayStation hybrid deformable image registration (DIR) algorithm for its overall integrity and accuracy in contour propagation for adaptive planning.Methods:The hybrid DIR is based on the combination of intensity‐based algorithm and anatomical information provided by contours. Patients who received mid‐treatment CT scans were identified for the study, including six lung patients (two mid‐treatment CTs) and six head‐and‐neck (HN) patients (one mid‐treatment CT). DIRpropagated ROIs were compared with physician‐drawn ROIs for 8 ITVs and 7 critical organs (lungs, heart, esophagus, and etc.) for the lung patients, as well as 14 GTVs and 20 critical organs (mandible, eyes, parotids, and etc.) for the HN patients. Volume difference, center of mass (COM) difference, and Dice index were used for evaluation. Clinical‐relevance of each propagated ROI was scored by two physicians, and correlated with the Dice index.Results:For critical organs, good agreement (Dice>0.9) were seen on all 7 for lung patients and 13 out of 20 for HN patients, with the rest requiring minimal edits. For targets, COM differences were within 5 mm on average for all patients. For Lung, 5 out of 8 ITVs required minimal edits (Dice 0.8–0.9), with the rest 2 needed re‐drawn due to their small volumes (<10 cc). However, the propagated HN GTVs resulted in relatively low Dice values (0.5–0.8) due to their small volumes (3–40 cc) and high variability, among which 2 required re‐drawn due to new nodal target identified on the mid‐treatment CT scans.Conclusion:The hybrid DIR algorithm was found to be clinically useful and efficient for lung and HN patients, especially for propagated critical organ ROIs. It has potential to significantly improve the workflow in adaptive planning.
SU‐F‐J‐69: The Dosimetric Impact of Interfraction Anorectum and Bladder Variability in Prostate Radiation Therapy
Authors: Patel V , Chinea F , Abramowitz M , Studenski M 
Published: July 2016

Purpose:In the era of dose escalation and numerous protocols evaluating radiation delivery to the prostate, it is imperative to achieve accurate and standardized daily set up. At the Sylvester Comprehensive Cancer Center, patients are instructed to drink 8 ounces of water 30 minutes prior to RT and follow a low residue diet to ensure that the anorectum is not distended and the bladder is adequately filled. If daily CBCT imaging shows any variation, the patient is removed from the table and drinks water or evacuates their rectum prior to a repeat CBCT. Here we attempt to quantify the efficacy of this procedure.Methods:CBCTs were collected for 5 patients receiving 40 fractions of definitive treatment for prostate cancer. CBCTs were imported into MIM (v6.5.7, Cleveland OH) and the bladder, anorectum, and prostate were contoured. Using the daily registration reviewed by the attending physician, the planning dose was rigidly transferred to the daily CBCT. On days that multiple CBCTs were performed due to inadequate anorectum or bladder preparation, the repeated and final CBCTs were evaluated for variations in V40Gy and V65Gy to both the anorectum and bladder.Results:A high level of variability in doses to the anorectum and bladder was found in the scans that were not utilized for treatment. The aggregate lower quartile for the unused versus used CBCTs was 27.2% vs. 16.83% for V40Gy and 8.53% vs. 5.66% for V65Gy bladder. The upper quartiles showed to be 48.88% vs. 41.92% and 21.05% vs. 20.55%. The combined lower quartile for the unused vs. used CBCTs was 8.24% vs. 5.49% for V40Gy and 0.57% vs. 0.0% for V65Gy anorectum. The upper quartiles were 34.35% vs. 33.25% and 18.37% vs. 16.11%.Conclusion:This study shows that daily imaging is insufficient and that proper bladder and anorectum preparation are essential to deliver proper treatment.