bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐410: Investigation of Treatment Planning Accuracy with the Presence of Magnetic Injection Port (breast Tissue Expander)
Authors: Cai W , Wagar M , Lyatskaya Y , Czerminska M 
Published: July 2016

Purpose:Mastectomy patients with breast reconstruction usually have a magnetic injection port inside the breast during radiation treatments. The magnet has a very high CT number and produces severe streaking artifact across the entire breast in CT images. Our routine strategy is to replace the artifact volumes with uniform water, and it is necessary to validate that the planned dose, with such an artifact correction, is sufficiently accurate.Methods:A phantom was made with a gelatine‐filled container sitting on a Matrixx detector, and the magnetic port was inserted into gelatine with specific depths and orientations. The phantom was scanned on a CT simulator and imported into Eclipse for treatment planning. The dose distribution at the Matrixx detector plane was calculated for raw CT images and artifact‐corrected images. The treatment beams were then delivered to the phantom and the dose distributions were acquired by the Matrixx detector. Gamma index was calculated to compare the planned dose and the measurement.Results:Three field sizes (10×10, 15×15 and 20×20) and two depths (50mm and 20mm) were investigated. With the 2%/2mm or 3%/3mm criteria, several points (6–10) failed in the plan for raw CT images, and the number of failure was reduced close to zero for the corrected CT images. An assignment of 10,000 HU to the magnet further reduced the dose error directly under the magnet.Conclusion:It is validated that our routine strategy of artifact correction can effectively reduce the number of failures in the detector plane. It is also recommended to set the magnet with a CT number of 10,000HU, which could potentially improve the dose calculation at the points right behind the magnet.
SU‐F‐T‐426: Measurement of Dose Enhancement Due to Backscatter From Modern Dental Materials
Authors: Hurwitz M , Tso T , Lee S , Rosen E , Margalit D , Williams C 
Published: July 2016

Purpose:High‐density materials used in dental restoration can cause significant localized dose enhancement due to electron backscatter in head‐and‐neck radiotherapy, increasing the risk of mucositis. The materials used in prosthetic dentistry have evolved in the last decades from metal alloys to ceramics. We aim to determine the dose enhancement caused by backscatter from currently‐used dental materials.Methods:Measurements were performed for three different dental materials: lithium disilicate (Li2Si2O5), zirconium dioxide (ZrO2), and gold alloy. Small thin squares (2×2×0.15 cm3) of the material were fabricated, and placed into a phantom composed of tissue‐equivalent material. The phantom was irradiated with a single 6 MV photon field. A thin‐window parallel‐plate ion chamber was used to measure the dose at varying distances from the proximal interface between the material and the plastic.Results:The dose enhancement at the interface between the high‐density and tissue‐equivalent materials, relative to a homogeneous phantom, was 54% for the gold alloy, 31% for ZrO2, and 9% for Li2Si2O5. This enhancement decreased rapidly with distance from the interface, falling to 11%, 5%, and 0.5%, respectively, 2 mm from the interface. Comparisons with the modeling of this effect in treatment planning systems are performed.Conclusion:While dose enhancement due to dental restoration is smaller with ceramic materials than with metal alloys, it can still be significant. A spacer of about 2–3 mm would be effective in reducing this enhancement, even for metal alloys.
SU‐F‐T‐427: Utilization and Evaluation of Diagnostic CT Imaging with MAR Technique for Radiation Therapy Treatment Planning
Authors: Xu M , Foster R , Parks H , Pankuch M 
Published: July 2016

Purpose:The objective was to utilize and evaluate diagnostic CT‐MAR technique for radiation therapy treatment planning.Methods:A Toshiba‐diagnostic‐CT acquisition with SEMAR(Single‐energy‐MAR)‐algorism was performed to make the metal‐artifact‐reduction (MAR) for patient treatment planning. CT‐imaging datasets with and without SEMAR were taken on a Catphan‐phantom. Two sets of CT‐numbers were calibrated with the relative electron densities (RED). A tissue characterization phantom with Gammex various simulating material rods was used to establish the relationship between known REDs and corresponding CT‐numbers. A GE‐CT‐sim acquisition was taken on the Catphan for comparison. A patient with bilateral hip arthroplasty was scanned in the radiotherapy CT‐sim and the diagnostic SEMAR‐CT on a flat panel. The derived SEMAR images were used as a primary CT dataset to create contours for the target, critical‐structures, and for planning. A deformable registration was performed with VelocityAI to track voxel changes between SEMAR and CT‐sim images. The SEMAR‐CT images with minimal artifacts and high quality of geometrical and spatial integrity were employed for a treatment plan. Treatment‐plans were evaluated based on deformable registration of SEMAR‐CT and CT‐sim dataset with assigned CT‐numbers in the metal artifact regions in Eclipse v11 TPS.Results:The RED and CT‐number relationships were consistent for the datasets in CT‐sim and CT's with and without SEMAR. SEMAR datasets with high image quality were used for PTV and organ delineation in the treatment planning process. For dose distribution to the PTV through the DVH analysis, the plan using CT‐sim with the assigned CT‐number showed a good agreement to those on deformable CT‐SEMAR.Conclusion:A diagnostic‐CT with MAR‐algorithm can be utilized for radiotherapy treatment planning with CT‐number calibrated to the RED. Treatment planning comparison and DVH shows a good agreement in the PTV and critical organs between the plans on CT‐sim with assigned CT‐number and the deformable SEMAR CT datasets.
SU‐F‐T‐430: Validation of IBEAM Evo Couch Top for Different Relative Electron Density (RED) Combination During Photon Beam Dose Calculation in Monaco− Treatment Planning System
Authors: Manigandan D , Kumar M , Mohandas P , Puri A , Bhalla N 
Published: July 2016

Purpose:Validation of iBEAM™ evo couch‐top for different relative electron density (RED) combination during photon beam dose calculation in Monaco− TPS.Methods:The iBEAM™ evo couch‐top has two layers:outer carbon fiber (CF) and inner foam core (FC). To study the beam intensity attenuation of couch‐top, measured doses were compared with doses calculated for different REDs. Measurements were performed in solid water phantom with PTW‐0.125cc ion‐chamber positioned at center of the phantom with 5.3cm thickness slabs placed above and below the chamber. Similarly, in TPS, iBEAM™ evo couch‐top was simulated and doses were calculated for different RED combinations (0.2CF‐0.2FC, 0.4CF‐0.2FC, 0.6CF‐0.2FC, 0.8CF‐0.2FC, and 1.0CF‐0.2FC) by using Monte Carlo dose calculation algorithm in Monaco TPS (V5.1). Doses were measured for every 10 degree gantry angle separation, 10×10cm2 field size and 6MV photons. Then, attenuation is defined as the ratio of output at posterior gantry angle to output of its opposed anterior gantry angle (e.g.225°/45°). output fluctuation with different gantry angle was within ±0.21%. To confirm above results, dose‐planes were measured for five pelvic VMAT plans (360°arc) in PTW two‐dimensional array and compared with different calculated dose‐planes of above‐mentioned couch REDs. Gamma pass rates<1.00) were analyzed for 3%/2mm criteria.Results:Measured and calculated attenuation was in good agreement for the RED combination of 0.2CF‐0.2FC and difference was within ±0.515%. However, other density combination showed difference of ±0.9841%, ±1.667%, ±2.9241% and ±2.8832% for 0.4CF‐0.2FC, 0.6CF‐0.2FC, 0.8CF‐0.2FC, and 1.0CF‐0.2FC, respectively. Maximum couch‐top attenuation was observed at 110°–120° and 240°–250° and decreases linearly as the gantry angle approaches 180°. Moreover, gamma pass rate confirmed the above results and showed maximum pass rate of 96.23% for 0.2CF‐0.2FC, whereas others were 95.72%, 95.12%, 94.31% and 93.24%.Conclusion:RED value of 0.2CF‐0.2FC was found to be suitable for accurate couch‐top modeling for 6MV photon beam Monte Carlo calculations in Monaco TPS.
SU‐F‐T‐435: Helical Tomotherapy for Craniospinal Irradiation: What We Have Learned from a Multi‐Institutional Study
Authors: Du D , Han C , Chen J , Perez‐Andujar A , Lee B , Kaprealian T , Low D , Qi X 
Published: July 2016

Purpose:To report cranio‐spinal irradiation (CSI) planning experience, compare dosimetric quality and delivery efficiency with Tomotherapy from different institutions, and to investigate effect of planning parameters on plan quality and treatment time.Methods:Clinical helical tomotherapy IMRT plans for thirty‐nine CSI cases from three academic institutions were retrospectively evaluated. The planning parameters: field width (FW), pitch, modulation factor (MF), and achieved dosimetric endpoints were cross‐compared. A fraction‐dose‐delivery‐timing index (FDTI), defined as treatment time per fraction dose per PTV length, was utilized to evaluate plan delivery efficiency. A lower FDTI indicates higher delivery efficiency. We studied the correlation between planning quality, treatment time and planning parameters by grouping the plans under specific planning parameters. Additionally, we created new plans using 5cm jaw for a subset of plans that used 2.5cm jaw to exam if treatment efficiency can be improved without sacrificing plan quality.Results:There were significant dosimetric differences for organ at risks (OARs) among different institutions (A,B,C). Using the lowest average MF (1.9±0.4) and 5cm field width, C had the highest lung, heart, kidney, liver mean doses and maximum doses for lens. Using the same field width of 5cm, but higher MF (2.6±0.6), B had lower doses to the OARs in the thorax and abdomen area. Most of A's plans were planned with 2.5cm jaw, the plans yielded better PTV coverage, higher OAR doses and slightly shorter FDTI compared to institution B. The replanned 5cm jaw plans achieved comparable PTV coverage and OARs sparing, while saving up to 44.7% treatment time.Conclusion:Plan quality and delivery efficiency could vary significantly in CSI planning on Tomotheapy due to choice of different planning parameters. CSI plans using a 5cm jaw, with proper selection of pitch and MF, can achieve comparable/ better plan quality with shorter delivery time compared to 2.5cm jaw plans.
SU‐F‐T‐436: A Method to Evaluate Dosimetric Properties of SFGRT in Eclipse TPS
Authors: Xu M , Wei J , Tobias R , Dick J , Crawford S , Swanson J , Pankuch M 
Published: July 2016

Purpose:The objective was to develop a method for dose distribution calculation of spatially‐fractionated‐GRID‐radiotherapy (SFGRT) in Eclipse treatment‐planning‐system (TPS).Methods:Patient treatment‐plans with SFGRT for bulky tumors were generated in Varian Eclipse version11. A virtual structure based on the GRID pattern was created and registered to a patient CT image dataset. The virtual GRID structure was positioned on the iso‐center level together with matching beam geometries to simulate a commercially available GRID block made of brass. This method overcame the difficulty in treatment‐planning and dose‐calculation due to the lack o‐the option to insert a GRID block add‐on in Eclipse TPS. The patient treatment‐planning displayed GRID effects on the target, critical structures, and dose distribution. The dose calculations were compared to the measurement results in phantom.Results:The GRID block structure was created to follow the beam divergence to the patient CT images. The inserted virtual GRID block made it possible to calculate the dose distributions and profiles at various depths in Eclipse. The virtual GRID block was added as an option to TPS. The 3D representation of the isodose distribution of the spatially‐fractionated beam was generated in axial, coronal, and sagittal planes. Physics of GRID can be different from that for fields shaped by regular blocks because the charge‐particle‐equilibrium cannot be guaranteed for small field openings. Output factor (OF) measurement was required to calculate the MU to deliver the prescribed dose. The calculated OF based on the virtual GRID agreed well with the measured OF in phantom.Conclusion:The method to create the virtual GRID block has been proposed for the first time in Eclipse TPS. The dosedistributions, in‐plane and cross‐plane profiles in PTV can be displayed in 3D‐space. The calculated OF's based on the virtual GRID model compare well to the measured OF's for SFGRT clinical use.
SU‐F‐T‐444: Quality Improvement Review of Radiation Therapy Treatment Planning in the Presence of Dental Implants
Authors: Parenica H , Ford J , Mavroidis P , Li Y , Papanikolaou N , Stathakis S 
Published: July 2016

Purpose:To quantify and compare the effect of metallic dental implants (MDI) on dose distributions calculated using Collapsed Cone Convolution Superposition (CCCS) algorithm or a Monte Carlo algorithm (with and without correcting for the density of the MDI).Methods:Seven previously treated patients to the head and neck region were included in this study. The MDI and the streaking artifacts on the CT images were carefully contoured. For each patient a plan was optimized and calculated using the Pinnacle3 treatment planning system (TPS). For each patient two dose calculations were performed, a) with the densities of the MDI and CT artifacts overridden (12 g/cc and 1 g/cc respectively) and b) without density overrides. The plans were then exported to the Monaco TPS and recalculated using Monte Carlo dose calculation algorithm. The changes in dose to PTVs and surrounding Regions of Interest (ROIs) were examined between all plans.Results:The Monte Carlo dose calculation indicated that PTVs received 6% lower dose than the CCCS algorithm predicted. In some cases, the Monte Carlo algorithm indicated that surrounding ROIs received higher dose (up to a factor of 2).Conclusion:Not properly accounting for dental implants can impact both the high dose regions (PTV) and the low dose regions (OAR). This study implies that if MDI and the artifacts are not appropriately contoured and given the correct density, there is potential significant impact on PTV coverage and OAR maximum doses.
SU‐F‐T‐506: Development and Commissioning of the Effective and Efficient Grid Therapy Using High Dose Rate Flattening Filter Free Beam and Multileaf Collimator
Authors: Liu M , Wen N , Beyer C , Siddiqui F , Chetty I , Zhao B 
Published: July 2016

Purpose:Treating bulky tumors with grid therapy (GT) has demonstrated high response rates. Long delivery time (∼15min), with consequent increased risk of intrafraction motion, is a major disadvantage of conventional MLC‐based GT (MLC‐GT). The goal of this study was to develop and commission a MLC‐GT technique with similar dosimetric characteristics, but more efficient delivery.Methods:Grid plan was designed with 10X‐FFF (2400MU/min) beam and MLC in a commercial treatment planning system (TPS). Grid size was 1cm by 1cm and grid‐to‐grid distance was 2cm. Field‐in‐field technique was used to flatten the dose profile at depth of 10cm. Prescription was 15Gy at 1.5cm depth. Doses were verified at depths of 1.5cm, 5cm and 10cm. Point dose was measured with a plastic scintillator detector (PSD) while the planar dose was measured with calibrated Gafchromic EBT3 films in a 20cm think, 30cmx30cm solid water phantom. The measured doses were compared to the doses calculated in the treatment planning system. Percent depth dose (PDD) within the grid was also measured using EBT3 film. Five clinical cases were planned to compare beam‐on time.Results:The valley‐to‐peak dose ratio at the 3 depths was approximately 10–15%, which is very similar to published result. The average point dose difference between the PSD measurements and TPS calculation is 2.1±0.6%. Film dosimetry revealed good agreement between the delivered and calculated dose. The average gamma passing rates at the 3 depths were 95% (3%, 1mm). The average percent difference between the measured PDD and calculated PDD was 2.1% within the depth of 20cm. The phantom plan delivery time was 3.6 min. Average beam‐on time was reduced by 66.1±5.6% for the 5 clinical cases.Conclusion:An effective and efficient GT technique was developed and commissioned for the treatment of bulky tumors using FFF beam combined with MLC and automation.The Department of Radiation Oncology at Henry Ford Health System receives research support from Varian Medical Systems and Philips Health Care
SU‐F‐T‐507: Modeling Cerenkov Emissions From Medical Linear Accelerators: A Monte Carlo Study
Authors: Shrock Z , Oldham M , Adamson J 
Published: July 2016

Purpose:Cerenkov emissions are a natural byproduct of MV radiotherapy but are typically ignored as inconsequential. However, Cerenkov photons may be useful for activation of drugs such as psoralen. Here, we investigate Cerenkov radiation from common radiotherapy beams using Monte Carlo simulations.Methods:GAMOS, a GEANT4‐based framework for Monte Carlo simulations, was used to model 6 and 18MV photon beams from a Varian medical linac. Simulations were run to track Cerenkov production from these beams when irradiating a 50cm radius sphere of water. Electron contamination was neglected. 2 million primary photon histories were run for each energy, and values scored included integral dose and total track length of Cerenkov photons between 100 and 400 nm wavelength. By lowering process energy thresholds, simulations included low energy Bremsstrahlung photons to ensure comprehensive evaluation of UV production in the medium.Results:For the same number of primary photons, UV Cerenkov production for 18MV was greater than 6MV by a factor of 3.72 as determined by total track length. The total integral dose was a factor of 2.31 greater for the 18MV beam. Bremsstrahlung photons were a negligibly small component of photons in the wavelength range of interest, comprising 0.02% of such photons.Conclusion:Cerenkov emissions in water are 1.6x greater for 18MV than 6MV for the same integral dose. Future work will expand the analysis to include optical properties of tissues, and to investigate strategies to maximize Cerenkov emission per unit dose for MV radiotherapy.
SU‐F‐T‐515: Increased Skin Dose in Supine Craniospinal Irradiation Due to Carbon Fiber Couch and Vacuum Bag Immobilization Device
Authors: Robertson D , Zhao Z , Wang X , Yang J 
Published: July 2016

Purpose:To measure the surface dose for supine craniospinal irradiation employing posterior beams, treating through an imaging couch and BlueBag immobilization device.Methods:The percentage depth dose (PDD) in the buildup region of a clinical 6 MV photon beam was measured using an Advanced Markus parallel plate ionization chamber in a solid water phantom. The PDD from a 10×10 cm2 anterior beam was measured at 100 cm SSD, simulating a traditional prone craniospinal technique. The measurements were compared to commissioning and treatment planning system data. The PDD was also measured in a posterior setup with the phantom surface laying directly on the Brainlab carbon fiber imaging couch, with the phantom surface 100 cm from the source, simulating a supine craniospinal setup. The posterior measurements were repeated with a BlueBag vacuum immobilization device between the couch and phantom, with thicknesses of 1.7 cm and 5 cm. The PDD from a 10×10 cm2 field and a typical 6×30 cm2 craniospinal field were also compared. The PDDs were normalized at 5 cm to reflect typical craniospinal prescription dose normalization.Results:The measured PDD curve from the anterior setup agreed well with commissioning and treatment planning data, with surface doses of 19.9%, 28.8% and 27.7%, respectively. The surface doses of the 10×10 cm2 and 6×30 cm2 fields delivered through the imaging couch were both 122.4%. The supine setup yielded surface doses of 122.4%, 121.6%, and 119.6% for the couch only, 1.7 cm bag, and 5 cm bag setups, respectively.Conclusion:Delivering craniospinal irradiation through a carbon fiber couch removes the majority of skin sparing. The addition of a vacuum bag immobilization device restores some skin sparing, but the magnitude of this effect is negligible.
SU‐F‐T‐518: Development and Characterization of a Gated Treatment System Implemented with An In‐House Optical Tracking System and the Elekta Response Interface
Authors: Barraclough B , Park J , Li F , Lu B , Li J , Liu C , Yan G 
Published: July 2016

Purpose:To report the development and characterization of the first in‐house gating system implemented with an optical tracking system (OTS) and the Elekta Response™ interface.Methods:The Response™ connects a patient tracking system with a linac, enabling the tracking system to control radiation delivery. The developed system uses an in‐house OTS to monitor patient breathing. The OTS consists of two infrared‐based cameras, tracking markers affixed on patient. It achieves gated or breath‐held (BH) treatment by calling beam ON/OFF functions in the Response™ dynamic‐link library (DLL). A 4D motion phantom was used to evaluate its dosimetric and time delay characteristics. Two FF‐ and two FFF‐IMRT beams were delivered in non‐gated, BH and gated mode. The sinusoidal gating signal had a 6 sec period and 15 mm amplitude. The duty cycle included 10%, 20%, 30% and 50%. The BH signal was adapted from the sinusoidal wave by inserting 15 sec BHs. Each delivery was measured with a 2D diode array (MapCHECK™) and compared with the non‐gated delivery using gamma analysis (3%). The beam ON/OFF time was captured using the service graphing utility of the linac.Results:The gated treatments were successfully delivered except the 10% duty cycle. The BH delivery had perfect agreement (100%) with non‐gated delivery; the agreement of gated delivery decreased from 99% to 88% as duty cycle reduced from 50% to 20%. The beam on/off delay was on average 0.25/0.06 sec. The delivery time for the 50%, 30% and 20% duty cycle increased by 29%, 71% and 139%, respectively. No dosimetric or time delay difference was noticed between FF‐ and FFF‐IMRT beams.Conclusion:The in‐house gating system was successfully developed with dosimetric and time delay characteristics in line with published results for commercial systems. It will be an important platform for further research and clinical development of gated treatment.