bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐110: MRI‐Guided Single‐Session Simulation, Online Adaptation, and Treatment
Authors: Hill P , Geurts M , Mittauer K , Bayouth J 
Published: July 2016

Purpose:To develop a combined simulation and treatment workflow for MRI‐guided radiation therapy using the ViewRay treatment planning and delivery system.Methods:Several features of the ViewRay MRIdian planning and treatment workflows are used to simulate and treat patients that require emergent radiotherapy. A simple “pre‐plan” is created on diagnostic imaging retrieved from radiology PACS, where conformal fields are created to target a volume defined by a physician based on review of the diagnostic images and chart notes. After initial consult in radiation oncology, the patient is brought to the treatment room, immobilized, and imaged in treatment position with a volumetric MR. While the patient rests on the table, the pre‐plan is applied to the treatment planning MR and dose is calculated in the treatment geometry. After physician review, modification of the plan may include updating the target definition, redefining fields, or re‐balancing beam weights. Once an acceptable treatment plan is finalized and approved, the patient is treated.Results:Careful preparation and judicious choices in the online planning process allow conformal treatment plans to be created and delivered in a single, thirty‐minute session. Several advantages have been identified using this process as compared to conventional urgent CT simulation and delivery. Efficiency gains are notable, as physicians appreciate the predictable time commitment and patient waiting time for treatment is decreased. MR guidance in a treatment position offers both enhanced contrast for target delineation and reduction of setup uncertainties. The MRIdian system tools designed for adaptive radiotherapy are particularly useful, enabling plan changes to be made in minutes. Finally, the resulting plans, typically 6 conformal beams, are delivered as quickly as more conventional AP/PA beam arrangements with comparatively superior dose distributions.Conclusion:The ViewRay treatment planning software and delivery system can accommodate a fast simulation and treatment workflow.
SU‐F‐J‐121: Dosimetric Evaluation of Active Breathing Coordinator‐Response Gating System Linked to Linear Accelerator in Volumetric Modulated Arc Therapy
Authors: Lee S , Zheng Y , Albani D , Colussi V , Dorth J , Sohn J 
Published: July 2016

Purpose:To reduce internal target volume (ITV), respiratory management is a must in imaging and treatment for lung, liver, and breast cancers. We investigated the dosimetric accuracy of VMAT treatment delivery with a Response™ gating system linked to linear accelerator.Methods:The Response™ gating module designed to directly control radiation beam by breath‐holding with a ABC system (Elekta AB, Stockholm, Sweden) was tested for VMAT treatments. Seven VMAT plans including three conventional and four stereotactic body radiotherapy (SBRT) cases were evaluated. Each plan was composed of two or four arcs of 6MV radiation beam with prescribed dose ranged from 1.8 to 9 Gy per fraction. Each plan was delivered continuously without gating and delivered with multiple interruptions by the ResponseTM gating module with a 20 or 30 second breath‐holding period. MapCheck2 and Gafchromic EBT3 films sandwiched in MapPHAN were used to measure the delivered dose with and without gating. Films were scanned on a flatbed color scanner, and red channel was extracted for film dosimetry. Gamma analysis was performed to analyze the dosimetrical accuracy of the radiation delivery with gating.Results:The measured doses with gating remarkably agree with the planned dose distributions in the results of gamma index passing rate (within 20% isodose; >98% for 3%/3mm and >92% for 2%/2mm in MapCheck2, and >91% for 3%/3mm criteria in EBT3 film except one case which was for large target and highly modulated). No significant difference (student t‐test: p‐value < 0.0005) was shown between the doses delivered with and without gating. There was no indication of radiation gap or overlapping during deliver interruption in film dosimetry.Conclusion:The Response™ gating system can be safely used during VMAT treatment. The accurate performance of the gating system linked to ABC can contribute to ITV reduction for SBRT using VMAT.
SU‐F‐J‐123: CT‐Based Determination of DIBH Variability and Its Dosimetric Impact On Post‐Mastectomy Plus Regional Nodal Radiation Therapy
Authors: Malin M , Kang H , Tatebe K , Hasan Y , Chmura S , Al‐Hallaq H 
Published: July 2016

Purpose:Breast cancer radiotherapy delivered using voluntary deep inspiration breath‐hold (DIBH) requires reproducible breath holds, particularly when matching supraclavicular fields to tangential fields. We studied the impact of variation in DIBHs on CTV and OAR dose metrics by comparing the dose distribution computed on two DIBH CT scans taken at the time of simulation.Methods:Ten patients receiving 50Gy in 25 fractions to the left chestwall and regional lymph nodes were studied. Two simulation CT scans were taken during separate DIBHs along with a free‐breathing (FB) scan. The treatment was planned using one DIBH CT. The dose was recomputed on the other two scans using adaptive planning (Pinnacle 9.10) in which the scans are registered using a cross‐correlation algorithm. The chestwall, lymph nodes and OARs were contoured on the scans following the RTOG consensus guidelines. The overall translational and rotational variation between the DIBH scans was used to estimate positional variation between breath‐holds. Dose metrics between plans were compared using paired t‐tests (p < 0.05) and means and standard deviations were reported.Results:The registration parameters were sub‐millimeter and sub‐degree. Although DIBH significantly reduced mean heart dose by 2.4Gy compared to FB (p < 0.01), no significant changes in dose were observed for targets or OARs between the two DIBH scans. Nodal coverage as assessed by V90% was 90%±8% and 89%±8% for supraclavicular and 99%±2% and 97%±22% for IM nodes. Though a significant decrease (10.5%±12.4%) in lung volume in the second DIBH CT was observed, the lung V20Gy was unchanged (14±2% and 14±3%) between the two DIBH scans.Conclusion:While the lung volume often varied between DIBHs, the CTV and OAR dose metrics were largely unchanged. This indicates that manual DIBH has the potential to provide consistent dose delivery to the chestwall and regional nodes targets when using matched fields.
SU‐F‐J‐129: Verification of Geometric and Dosimetric Accuracy of Respiratory Management Systems Using Homemade Phantom
Authors: Goksel E , Kucucuk H , Senkesen O , Tezcanli E 
Published: July 2016

Purpose:Different placements of Infrared Cameras (IRC) in CT and treatment rooms can cause gating window level (GWL) variations leading to differences between GWL used for planning and treatments. Although, Varian Clinac DHX‐OBI sytem and CT are equipped with the same kind of IRC, Truebeam STx (TB) has a different type of IRC known as banana type. In this study; geometric and dosimetric accuracy of respiratory management system (RPM) for different machines were investigated with a special homemade phantom.Methods:Special phantom was placed on the respiratory simulator machine and a CT data set was obtained at the end of the expirium phase (EOE). Conformal and IMRT plans were generated on the EOE CT image series for both DHX‐OBI and TB LINACs while a VMAT plan was generated only for TB.The acquired respiratory graphs in the CT were directly sent to DHX‐OBI system, and they were converted with software before sending to TB. EBT3 films were placed inside the phantom and were irradiated using RPM system with two machines for different plans. Planar dose distributions were compared with gamma analysis (GA) method (3mm, %3) to evaluate planned‐measured dose differences. In addition, radio‐opac marker was placed in the center of the phantom to evaluate the geometric accuracy of treatment field with gated flouroscopy (GF).Results:There were no shifts detected between planning and treeatment GWL for both DHX‐OBI and TB. Difference on the GF image between digital graticule and radio‐opac marker was <1mm for TB and 1mm for DHX‐OBI. Although, GA agreement was 97% for conformal and IMRT techniques in TB, it was 96% for VMAT technique. While GA agreement was 98% for conformal technique in DHX‐OBI, IMRT was 95%.ConclusionThis study showed that RPM can be used accurately in spite of different IRC placements or different types of ICR used.
SU‐F‐J‐135: Tumor Displacement‐Based Binning for Respiratory‐Gated Time‐Independent 5DCT Treatment Planning
Authors: Yang L , O'Connell D , Lee P , Shaverdian N , Kishan A , Lewis J , Dou T , Thomas D , Qi X , Low D 
Published: July 2016

Purpose:A published 5DCT breathing motion model enables image reconstruction at any user‐selected breathing phase, defined by the model as a specific amplitude (v) and rate (f). Generation of reconstructed phase‐specific CT scans will be required for time‐independent radiation dose distribution simulations. This work answers the question: how many amplitude and rate bins are required to describe the tumor motion with a specific spatial resolution?Methods:19 lung‐cancer patients with 21 tumors were scanned using a free‐breathing 5DCT protocol, employing an abdominally positioned pneumatic‐bellows breathing surrogate and yielding voxel‐specific motion model parameters α and β corresponding to motion as a function of amplitude and rate, respectively. Tumor GTVs were contoured on the first (reference) of 25 successive free‐breathing fast helical CT image sets. The tumor displacements were binned into widths of 1mm to 5mm in 1mm steps and the total required number of bins recorded. The simulation evaluated the number of bins needed to encompass 100% of the breathing‐amplitude and between the 5th and 95th percentile amplitudes to exclude breathing outliers.Results:The mean respiration‐induced tumor motion was 9.90mm ± 7.86mm with a maximum of 25mm. The number of bins required was a strong function of the spatial resolution and varied widely between patients. For example, for 2mm bins, between 1–13 amplitude bins and 1–9 rate bins were required to encompass 100% of the breathing amplitude, while 1–6 amplitude bins and 1–3 rate bins were required to encompass 90% of the breathing amplitude.Conclusion:The strong relationship between number of bins and spatial resolution as well as the large variation between patients implies that time‐independent radiation dose distribution simulations should be conducted using patient‐specific data and that the breathing conditions will have to be carefully considered. This work will lead to the assessment of the dosimetric impact of binning resolution.This study is supported by Siemens Healthcare
SU‐F‐J‐136: Impact of Audiovisual Biofeedback On Interfraction Motion Over a Course of Liver Cancer Stereotactic Body Radiotherapy
Authors: Pollock S , Tse R , Martin D , McLean L , Pham M , Tait D , Estoesta R , Whittington G , Turley J , Kearney C , Cho G , Hill R , Pickard S , Aston P , Makhija K , O'Brien R , Keall P 
Published: July 2016

Purpose:In abdominal radiotherapy inconsistent interfraction respiratory motion can result in deviations during treatment from what was planned in terms of target position and motion. Audiovisual biofeedback (AVB) is an interactive respiratory guide that produces a guiding interface that the patient follows over a course of radiotherapy to facilitate regular respiratory motion. This study assessed the impact of AVB on interfraction motion consistency over a course of liver cancer SBRT.Methods:Five liver cancer patients have been recruited into this study, 3 followed AVB over their course of SBRT and 2 were free breathing (FB). Respiratory signals from the Varian RPM were obtained during 4DCT and each treatment fraction. Respiratory signals were organized into 10 respiratory bins, and interfraction consistency was quantified by the difference between each treatment fraction respiratory bin and each respiratory bin from 4DCT. Interfraction consistency was considered as both the relative difference (as a percentage) and absolute difference (in centimeters) between treatment respiratory bins and 4DCT respiratory bins.Results:The relative difference between 4DCT and treatment respiratory bins was 22 ± 16% for FB, and 15 ± 10% for AVB, an improvement of 32% (p < 0.001) with AVB. The absolute difference between 4DCT and treatment respiratory bins was 0.15 ± 0.10 cm for FB, and 0.14 ± 0.13 cm for AVB, an improvement of 4% (p = 0.6) with AVB.Conclusion:This was the first study to compare the impact of AVB breathing guidance on interfraction motion consistency over a course of radiotherapy. AVB demonstrated to significantly reduce the relative difference between 4DCT and treatment respiratory motion, but the absolute differences were comparable, largely due to one AVB patient exhibiting a larger amplitude than the other patients. This study demonstrates the potential benefit of AVB in reducing motion variations during treatment from what was planned.Paul Keall, Sean Pollock, Ricky OBrien and Kuldeep Makhija are shareholders of Respiratory Innovations, an Australian company that is developing a device to improve breathing stability. No funding or support was provided by Respiratory Innovations. Paul Keall is one of the inventors of US patent # 7955270.
SU‐F‐J‐142: Proposed Method to Broaden Inclusion Potential of Patients Able to Use the Calypso Tracking System in Prostate Radiotherapy
Authors: Fiedler D , Kuo H , Bodner W , Tome W 
Published: July 2016

Purpose:To introduce a non‐standard method of patient setup, using BellyBoard immobilization, to better utilize the localization and tracking potential of an RF‐beacon system with EBRT for prostate cancer.Methods:An RF‐beacon phantom was imaged using a wide bore CT scanner, both in a standard level position and with a known rotation (4° pitch and 7.5° yaw). A commercial treatment planning system (TPS) was used to determine positional coordinates of each beacon, and the centroid of the three beacons for both setups. For each setup at the Linac, kV AP and Rt Lateral images were obtained. A full characterization of the RF‐beacon system in clinical mode was completed for various beacons’ array‐to‐centroid distances, which includes vertical, lateral, and longitudinal offset data, as well as pitch and yaw offset measurements for the tilted phantom. For the single patient who has been setup using the proposed BellyBoard method, a supine simulation was first obtained. When abdominal protrusion was found to be exceeding the limits of the RF‐Beacon system through distance‐based analysis in the TPS, the patient is re‐simulated prone with the BellyBoard. Array to centroid distance is measured again in the TPS, and if found to be within the localization or tracking region it is applied.Results:Characterization of limitations for the RF‐beacon system in clinical mode showed acceptable consistency of offset determination for phantom setup accuracy. The nonstandard patient setup method reduced the beacons’ centroid‐to‐array distance by 8.32cm, from 25.13cm to 16.81cm; completely out of tracking range (greater than 20cm) to within setup tracking range (less than 20cm).Conclusion:Using the RF‐beacon system in combination with this novel patient setup can allow patients who would otherwise not be candidates for beacon enhanced EBRT to now be able to benefit from the reduced PTV margins of this treatment method.
SU‐F‐J‐149: Beam and Cryostat Scatter Characteristics of the Elekta MR‐Linac
Authors: Duglio M , Towe S , Roberts D 
Published: July 2016

Purpose:The Elekta MR‐Linac combines a digital linear accelerator system with a 1.5T Philips MRI machine. This study aimed to determine key characteristic information regarding the MR‐Linac beam and in particular it evaluated the effect of the MR cryostat on the out of field scatter dose.Methods:Tissue phantom ratios, profiles and depth doses were acquired in plastic water with an IC‐profiler or with an MR compatible water tank using multiple system configurations (Full (B0= 1.5T), Full (B0=0T) and No cryostat). Additionally, an in‐house CAD based Monte Carlo code based on Penelope was used to provide comparative data.Results:With the cryostat in place and B0=0T, the measured TPR for the MR Linac system was 0.702, indicating an energy of around 7MV. Without the cryostat, the measured TPR was 0.669. For the Full (B0=0T) case, out of field dose at a depth of 10 cm in the isocentric plane, 5 cm from the field edge was 0.8%, 3.1% and 5.4% for 3×3 cm2, 10×10 cm2 and 20×20 cm2 fields respectively.The out of field dose (averaged between 5 cm and 10 cm beyond the field edges) in the “with cryostat” case is 0.78% (absolute difference) higher than without the cryostat for clinically relevant field sizes (i.e. 10×10 cm2) and comparable to measured conventional 6MV treatment beams at a depth of 10 cm (within 0.1% between 5 cm and 6 cm from field edge). At dose maximum and at 5 cm from the field edge, the “with cryostat” out of field scatter for a 10×10 cm2 field is 1.5% higher than “without cryostat”, with a modest increase (0.9%) compared to Agility 6MV in the same conditions.Conclusion:The study has presented typical characteristics of the MR‐Linac beam and determined that out of field dose is comparable to conventional treatment beams.All authors are employed by Elekta Ltd., who are developing an MR‐Linac.
SU‐F‐J‐157: Effect of Contouring Uncertainty in Post Implant Dosimetry of Low‐Dose‐Rate Prostate Permanent Seed Brachytherapy
Authors: Mashouf S , Safigholi H , Merino T , Soliman A , Ravi A , Morton G , Song W 
Published: July 2016

Purpose:There is strong evidence relating post‐implant dosimetry for low‐dose‐rate (LDR) prostate seed brachytherapy to local control rates. The delineation of the prostate on CT images, however, represents a challenge due to the lack of soft tissue contrast in order to identify the prostate borders. This study aims at quantifying the sensitivity of clinically relevant dosimetric parameters to uncertainty in the contouring of prostate.Methods:CT images, post‐op plans and contours of a cohort of patients (n=43) (low risk=55.8%, intermediate risk=39.5%, high risk=4.7%), who had received prostate seed brachytherapy, were imported into MIM Symphony treatment planning system. The prostate contours in post‐implant CT images were expanded/contracted uniformly for margins of ±1.00 mm, ±2.00 mm, ±3.00 mm, ±4.00 mm and ±5.00 mm. The values for V100 and D90 were extracted from Dose Volume Histograms for each contour and compared.Results:Significant changes were observed in the values of D90 and V100 as well as the number of suboptimal plans for expansion or contraction margins of only few millimeters. Evaluation of coverage based on D90 was found to be less sensitive to expansion errors compared to V100. D90 led to a lower number of implants incorrectly identified with insufficient coverage for expanded contours which increases the accuracy of post‐implant QA using CT images compared to V100.Conclusion:In order to establish a successful post implant QA for LDR prostate seed brachytherapy, it is necessary to identify the low and high thresholds of important dose metrics of the target volume such as D90 and V100. Since these parameters are sensitive to target volume definition, accurate identification of prostate borders would help to improve accuracy and predictive value of the post‐implant QA process. In this respect, use of imaging modalities such as MRI where prostate is well delineated should prove useful.
SU‐F‐J‐162: Is Bulky Electron Density Assignment Appropriatefor MRI‐Only Based Treatment Planning for Lung Cancer?
Authors: Prior P , Chen X , Johnstone C , Gore E , Li X 
Published: July 2016

Purpose:To assess the appropriateness of bulky electron density assisment for MRI‐only treatment planning for lung cancer via comparing dosimetric difference between MRI‐ and CT‐based plans.Methods:Planning 4DCTs acquired for six representative lung cancer patients were used to generate CT‐based IMRT plans. To avoid the effect of anatomic difference between CT and MRI, MRI‐based plans were generated using CTs by forcing the relative electron density (rED) of organ specific values from ICRU report 46 and using the mean rED value of the internal target volume (ITV) of the patient for the ITV. Both CT and “MRI” plans were generated using a research planning system (Monaco, Elekta) employing Monte Carlo dose calculation the following dose‐volume‐parameters (DVPs): D99 – dose delivered to 99% of the ITV/PTV volume; D95; D5; D1; Vpd –volume receiving the prescription dose; V5 – volume of normal lung irradiated > 5 Gy; and V20. The percent point difference and dose difference was used for comparison for Vpd‐V5‐V20 and D99‐D1, respectively. Four additional plans per patient were calculated with rEDITV = 0.6 and 1.0 and rEDlung = 0.1 and 0.5.Results:Noticeable differences in the ITV and PTV point doses and DVPs were observed. Variations in Vpd ranged from 0.0–6.4% and 0.32–18.3% for the ITV and PTV, respectively. The ITV and PTV variations in D99, D95, D5 and D1 were 0.15–3.2 Gy. The normal lung V5 & V20 variations were no larger than 1.9%. In some instances, varying the rEDITV between rEDmean, 0.6 and 1.0 resulted in D95 increases ranging from 3.9–6.3%. Uniform rED assignment on normal lung affected DVPs of ITV and PTV by 4.0–9.8% and 0.3–19.6%, respectively.Conclusion:The commonly‐used uniform rED assignment in MRI‐only based planning may not be appropriate for lung‐cancer. A voxel based method, e.g. synthetic CT generated from MRI data, is required.This work was partially funded by Elekta, Inc.
SU‐F‐J‐164: A Simulation Study On Anovel 4D MRI Reconstruction Method Based On Probability‐Driven Sorting
Authors: Liang X , Yin F , Liu Y , Cai J 
Published: July 2016

Purpose:To evaluate a novel probability‐driven sorting based 4D MRI reconstruction method by comparing with the conventional 4D MRI reconstruction methods.Methods:We have proposed a novel probability‐driven sorting based 4D MRI reconstruction method capable of retaining breathing variation information in breathing signals by generating multiple breathing cycles instead of a single cycle as the case with conventional 4D MRI reconstruction methods. It is expected that our proposed method can reduce motion artifacts caused by breathing variations, and can generate more accurate Average Intensity Projections (AIP). To evaluate the performance of the novel method, the probability‐driven sorting based method, along with two conventional phase‐based methods, for cine acquisition mode, and sequential acquisition mode, was applied on six patient breathing curves to simulate the 4D MRI reconstruction process using eXtended CArdiac Torso (XCAT) phantom. In the 4D images, a spherical target of 3 cm in diameter was generated in the liver and set to move with the liver. AIPs were generated for all three sets of 4D images. Ground‐truth AIP was generated by averaging all the 3D volumes of the phantom. Motion artifacts were evaluated by the tumor volume consistency in 4D images and volume difference from the tumor volumes measured in 3D images. AIPs from the three sorting methods were evaluated and compared to the reference AIP in terms of intensity difference.Results:Probability‐driven sorting has higher target volume consistency between phases for all the six patients, indicating the less motion artifacts. AIP from probability‐driven sorting has the best agreement with the ground‐truth AIP among the three reconstruction methods.Conclusion:Based on the cases in this study, it has been shown that probability‐driven sorting method is capable of generating multi‐cycle 4D MRI images with reduced motion artifacts and improved AIP accuracy. 1R21CA165384