bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐643: Feasibility of Performing Patient Specific VMAT QA On Single Linac for Plans Treated in Beam‐Matched Elekta Agility Linacs
Authors: Leung R , Lee V , Cheung S , Lee K , Law G , Wong M , Chan M , Mun Tuen 
Published: July 2016

Purpose:The increasing application of VMAT demands a more efficient workflow and QA solution. This study aims to investigate the feasibility of performing VMAT QA measurements on one linac for plans treated on other beam‐matched Elekta Agility linacs.Methods:A single model was used to create 24 clinically approved VMAT plans (12 head‐and‐neck and 12 prostate using 6MV and 10MV respectively) on Pinnacle v9.10 (Philips, Einhoven, Netherlands). All head‐and‐neck plans were delivered on three beam‐matched machines while all prostate cases were delivered on two beam‐matched 10MV Agility machines. All plans were delivered onto PTW Octavius 4D phantom with 1500 detector array (PTW, Freiburg, Germany). Reconstructed volume doses were then compared with the Pinnacle reference plans in Verisoft 6.1 under 3%/3mm gamma criteria at local dose. Plans were considered clinically acceptable if >90% of the voxels passing the gamma criteria.Results:All measurements were passed (3D gamma passing rate >90%) and the result shows that the mean difference of 3D gamma of 12 head‐and‐neck cases is 1.2% with standard deviation of 0.6%. While for prostate cases, the mean difference of 3D gamma is 0.9% with standard deviation of 0.7%. Maximum difference of 3D gamma of all measurements between beam‐matched machines is less than 2.5%. The differences of passing rates between different machines were statistically insignificant (p>0.05). Conclusion. The result suggests that therConclusion:The result suggests that there exists a 3D gamma threshold, in our case 92.5%, above which the VMAT QA performed in any one of beam‐matched machine will also pass in another one. Therefore, VMAT QA efficiency may be increased and phantom set up time can be saved by implementing such method. A constant performance across all beam matched machines must be maintained to make this QA approach feasible.
SU‐F‐T‐647: Linac‐Based Stereotactic Radiosurgery (SRS) in the Treatment of Trigeminal Neuralgia: Detailed Description of SRS Procedural Technique and Reported Clinical Outcomes
Authors: Pokhrel D , Sood S , Badkul R , Jiang H , Stepp T , Camarata P , Wang F 
Published: July 2016

Purpose:SRS is an effective non‐invasive alternative treatment modality with minimal‐toxicity used to treat patients with medically/surgically refractory trigeminal neuralgia root(TNR) or those who may not tolerate surgical intervention. We present our linac‐based SRS procedure for TNR treatment and simultaneously report our clinical outcomes.Methods:Twenty‐eight TNR‐patients treated with frame‐based SRS at our institution (2009–2015) with a single‐fraction point‐dose of 60‐80Gy to TNR were included in this IRB‐approved study. Experienced neurosurgeon and radiation oncologist delineated the TNR on 1.0mm thin 3D‐FIESTA‐MRI that was co‐registered with 0.7mm thin planning‐CT. Treatment plans were generated in iPlan (BrainLAB) with a 4‐mm diameter cone using 79 arcs with differential‐weighting for Novalis‐TX 6MV‐SRS(1000MU/min) beam and optimized to minimize brainstem dose. Winston‐Lutz test was performed before each treatment delivery with sub‐millimeter isocenter accuracy. Quality assurance of frame placement was maintained by helmet‐bobble‐measurement before simulation‐CT and before patient setup at treatment couch. OBI‐CBCT scan was performed for patient setup verification without applying shifts. On clinical follow up, treatment response was assessed using Barrow Neurological Institute Pain Intensity Score(BNI‐score:I–V).Results:26/28 TNR‐patients (16‐males/10‐females) who were treated with following single‐fraction point‐dose to isocenter: 80Gy(n=22),75Gy(n=1),70Gy(n=2) and 60Gy(n=1, re‐treatment) were followed up. Median follow‐up interval was 8.5‐months (ranged:1–48.5months). Median age was 70‐yr (ranged:43–93‐yr). Right/left TNR ratio was 15/11. Delivered total # of average MUs was 19034±1204. Average beam‐on‐time: 19.0±1.3min. Brainstem max‐dose and dose to 0.5cc were 13.3±2.4Gy (ranged:8.1–16.5Gy) and 3.6±0.4Gy (ranged:3.0–4.9Gy). On average, max‐dose to optic‐apparatus was ≤1.2Gy. Mean value of max‐dose to eyes/lens was 0.26Gy/0.11Gy. Overall, 20‐patients (77%) responded to treatment: 5(19%) achieved complete pain relief without medication (BNI score: I); 5(19%) had no‐pain, decreased medication (BNI‐score:II); 2(7.7%) had no‐pain, but, continued medication (BNI‐score:IIIA), and 8(30.8%) had pain that was well controlled by medication (BNI‐score: IIIB). Six‐patients (23.0%) did not respond to treatment (BNI‐score:IV–V). Neither cranial nerve deficit nor radio‐necrosis of temporal lobe was clinically observed.Conclusion:Linac‐based SRS for medically/surgically refractory TNR provided an effective treatment option for pain resolution/control with very minimal if any normal tissue toxicity. Longer follow up of these patients is anticipated/needed to confirm our observations.
SU‐F‐T‐648: Sharpening Dose Fall‐Off Via Beam Number Enhancements For Stereotactic Brain Radiosurgery
Authors: Chiu J , Pierce M , Braunstein S , McDermott M , Sneed P , Ma L 
Published: July 2016

Purpose:Sharp dose fall‐off is the hallmark of brain radiosurgery to deliver a high dose of radiation to the target while minimizing dose to normal brain tissue. In this study, we developed a technique for the purpose of enhancing the peripheral dose gradient by magnifying the total number of beams focused toward each isocenter via patient head tilt and simultaneous beam intensity modulations.Methods:Computer scripting for the proposed beam number enhancement (BNE) technique was developed. The technique was tested and then implemented on a clinical treatment planning system for a dedicated brain radiosurgical system (GK Perfexion, Elekta Oncology). To study technical feasibility and dosimetric advantages of the technique, we compared treatment planning quality and delivery efficiency for 20 radiosurgical cases previously treated at our institution. These cases included relatively complex treatments such as acoustic schwannoma, meningioma, brain metastasis and mesial temporal lobe epilepsy.Results:The BNE treatment plans were found to produce nearly identical target volume coverage (absolute value < 0.5%, P > 0.2) and dose conformity (BNE CI= 1.41±0.15 versus 1.41±0.20, P>0.9) as the original treatment plans. The total beam‐on time for theBNE treatment plans were comparable (within 1.0 min or 1.8%) with those of the original treatment plans for all the cases. However, BNE treatment plans significantly improved the mean gradient index (BNE GI = 2.9±0.3 versus original GI =3.0±0.3 p<0.0001) and low‐level isodose volumes, e.g. 20‐50% prescribed isodose volumes, by 2.0% to 5.0% (p<0.02). Furthermore, with 4 to 5‐fold increase in the total number of beams, the GI decreased by as much as 20% or 0.5 in absolute values.Conclusion:BNE via head tilt and simultaneous beam intensity modulation is an effective and efficient technique that physically sharpens the peripheral dose gradient for brain radiosurgery.
SU‐F‐T‐654: Pacemaker Dose Estimate Using Optically Stimulated Luminescent Dosimeter for Left Breast Intraoperative Radiation Therapy
Authors: Chen Y , Goenka A , Sharma A , Wang L , Cao Y , Jamshidi A 
Published: July 2016

Purpose:To assess and report the in vivo dose for a patient with a pacemaker being treated in left breast intraoperative radiation therapy (IORT). The ZEISS Intrabeam 50 kVp X‐ray beam with a spherical applicator was used.Methods:The optically stimulated luminescent dosimeters (OSLDs) (Landauer nanoDots) were employed and calibrated under the conditions of the Intrabeam 50 kVp X‐rays. The nanoDots were placed on the patient at approximately 15 cm away from the lumpectomy cavity both under and above a shield of lead equivalence 0.25 mm (RayShield X‐Drape D‐110) covering the pacemaker area during IORT with a 5 cm spherical applicator.Results:The skin surface dose near the pacemaker during the IORT with a prescription of 20 Gy was measured as 4.0±0.8 cGy. The dose behind the shield was 0.06±0.01 Gy, demonstrating more than 98% dose reduction. The in vivo skin surface doses during a typical breast IORT at a 4.5 cm spherical applicator surface were further measured at 5, 10, 15, and 20 cm away to be 159±11 cGy, 15±1 cGy, 6.6±0.5 cGy, and 1.8±0.1 cGy, respectively. A power law fit to the dose versus the distance z from the applicator surface yields the dose fall off at the skin surface following z^‐2.5, which can be used to estimate skin doses in future cases. The comparison to an extrapolation of depth dose in water reveals an underestimate of far field dose using the manufactory provided data.Conclusion:The study suggests the appropriateness of OSLD as an in vivo skin dosimeter in IORT using the Intrabeam system in a wide dose range. The pacemaker dose measured during the left breast IORT was within a safe limit.
SU‐F‐T‐661: Dependence of Gold Nano Particles Cluster Morphology On Dose Enhancement of Photon Radiation Therapy Apply for Radiation Biology Effect
Authors: Ahn S , Chung K , Han Y , Park H 
Published: July 2016

Purpose:Injected gold nano particles (GNPs) to a body for dose enhancement are known to form in the tumorcell cluster morphology. We investigated the dependence of dose enhancement on the morphology characteristic with an approximated morphology model by using Monte Carlo simulations.Methods:For MC simulation, TOPAS version 2.0P‐03 was used. GNP cluster morphology was approximated as a body center cubic(BCC) model by placing 8 GNPs at the corner and one at the center of cube with length from 2.59 µm to 0.25 µm located in a 4 µm length water filled cube phantom. 4 µm length square shaped beams of poly‐energetic 50, 260 kVp photons were irradiated to the water filled cube phantom with 100 nm diameter GNPs in it. Dose enhancement ratio(DER) was computed as a function of distance from the surface of the GNP at the cube center for 18 cubes geometries. For scoring particles, 10 nm width of concentric shell shaped detector was constructed up to 100 nm from the center. Total dose in a sphere of 100 nm radius of detector were normalized to 2.59 µm length cube morphology. To verified biological effect of BCC model applied to cell survival curve fitting.Results:DER increase as the distance of the GNPs reduces. DER was largest for 0.25 µm length cube. Dependence of GNP distance DER increment was 1.73, 1.60 for 50 kVp, 260 kVp photons, respectively. Also, Using BCC model applied to cell survival curve was well prediction.Conclusion:DER with GNPs was larger when they are closely packed in the phantom. Therefore, better therapeutic effects can be expected with close‐packed GNPs.This research was supported by the NRF funded by the Ministry of Science, ICT & Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081]
SU‐F‐T‐663: Cerenkov Radiation Enhanced Radiotherapy with Titanium Dioxide Nanoparticle: A Monte Carlo Study
Authors: Liu B , Ouyang Z , Sajo E , Ngwa W 
Published: July 2016

Purpose:A recent publication has shown that by delivering titanium dioxide nanoparticles (titania) as a photosensitizer into tumors, Cerenkov radiation (CR) produced by radionuclides could be used for substantially boosting damage to cancer cells. The present work compares CR production by various clinically relevant radiation sources including internal radionuclides and external beam radiotherapy (EBRT), and provides preliminarily computational results of CR absorption by titania.Methods:1) Geant4.10.1 was used to simulate ionizing radiation‐induced CR production in a 1cm diameter spherical volume using external radiotherapy sources: Varian Clinac IX 6MV and Eldorado 60Co, both with 10*10 cm2 field size. In each case the volume was placed at the maximum dose depth (1.5cm for 6MV source and 0.5cm for 60Co). In addition, 18F, 192Ir and 60Co were simulated using Geant4 radioactive decay models as internal sources. Dose deposition and CR production spectra in 200nm‐400nm range were calculated as it is the excitation range of titania. 2) Using 6MV external source, the absorption by titania was calculated via the track length of CR in the spherical volume. The nanoparticle concentration was varied from 0.25 to 5µg/g.Results:Among different radioactive sources, results showed that 18F induced the highest amount of CR per disintegration, but 60Co had the highest yield per unit dose. When compared with external sources, 6MV source was shown to be the most efficient for the the same delivered dose. Simulations indicated increased absorption for increasing concentrations, with up to 68% absorption of generated CR for 5µg/g titania concentration.Conclusion:The results demonstrate that 6MV beam is favored with a higher CR yield, compared to radionuclides, and that the use of higher concentrations of titania may increase photosensitization. From the findings, we propose that if sufficiently potent concentrations of titania are delivered to tumors this could substantially boost EBRT.
SU‐F‐T‐664: The Efficacy of Gold Nanoparticles as Contrast Agents in Mice
Authors: Yuan Y , Zhang Y , Yasmin‐Karim S , Karve A , Sajo E , Ngwa W 
Published: July 2016

Purpose:Micro‐Computed Tomography (micro‐CT) has been widely used as a non‐invasive, high‐resolution imaging modality in preclinical research. However, tumors cannot be well distinguished, since their density are similar to those of surrounding tissues, and the tumors’ natural contrast is very low. The benefits of using Gold Nanoparticles (AuNPs) as a promising high atomic weight contrast agent have been published in recent years. The aim of this study is to investigate the efficacy of AuNPs as contrast agents using different energy x‐rays.Methods:The left flank of an immune‐compromised athymic nude mouse was implanted with subcutaneous xenograft model of human lung cancer line, A549 cells (from ATCC). After 14 days, this mouse was imaged with dual energy cone‐beam micro‐CT. The selected energies were 45 kVp and 65 kVp. 10µg AuNPs (200 µg/ml concentration) approximately 12 nm in size were injected subcutaneously into the tumor. The mouse was imaged 0, 3 and 24 hours post‐injection. During scanning, this mouse was anesthetized. All projection raw data have been optimized and then images were reconstructed with the FDK Algorithm.Results:Based on images, at 0 hour, AuNPs provided obvious contrast no matter which energy selected, 45 kVp or 65 kVp; and using 45 kVp X‐ray, AuNps showed greater contrast. After 3 hours or evenand longer, AuNPs distributed throughout the whole body of mouse, and they were not shown clearly shown in the images.Conclusion:In this study, we investigated the efficacy of AuNPs as image contrast agents at different energies with dual‐energy micro‐CT, using 200µg/mL of AuNPs. Sufficiently high concentrations of AuNPs are needed to be able to track intratumoral distribution. Images showed good contrast immediately following the administration of the agent but results were poor after 3 hours.
SU‐F‐T‐667: Development and Validation of Dose Calculation for An Open‐Source KV Treatment Planning System for Small Animal Radiotherapy
Authors: Prajapati S , Mo X , Bednarz B , Lawless M , Hammer C , Flynn R , Westerly D , Jeraj R , Mackie T 
Published: July 2016

Purpose:An open‐source, convolution/superposition based kV‐treatment planning system(TPS) was developed for small animal radiotherapy from previously existed in‐house MV‐TPS. It is flexible and applicable to both step and shoot and helical tomotherapy treatment delivery. For initial commissioning process, the dose calculation from kV‐TPS was compared with measurements and Monte Carlo(MC) simulations.Methods:High resolution, low energy kernels were simulated using EGSnrc user code EDKnrc, which was used as an input in kV‐TPS together with MC‐simulated x‐ray beam spectrum. The Blue Water™ homogeneous phantom (with film inserts) and heterogeneous phantom (with film and TLD inserts) were fabricated. Phantom was placed at 100cm SSD, and was irradiated with 250 kVp beam for 10mins with 1.1cm × 1.1cm open field (at 100cm) created by newly designed binary micro‐MLC assembly positioned at 90cm SSD. Gafchromic™ EBT3 film was calibrated in‐phantom following AAPM TG‐61 guidelines, and were used for measurement at 5 different depths in phantom. Calibrated TLD‐100s were obtained from ADCL. EGS and MNCP5 simulation were used to model experimental irradiation set up calculation of dose in phantom.Results:Using the homogeneous phantom, dose difference between film and kV‐TPS was calculated: mean(x)=0.9%; maximum difference(MD)=3.1%; standard deviation(σ)=1.1%. Dose difference between MCNP5 and kV‐TPS was: x=1.5%; MD=4.6%; σ=1.9%. Dose difference between EGS and kV‐TPS was: x=0.8%; MD=1.9%; σ=0.8%. Using the heterogeneous phantom, dose difference between film and kV‐TPS was: x=2.6%; MD=3%; σ=1.1%; and dose difference between TLD and kV‐TPS was: x=2.9%; MD=6.4%; σ=2.5%.Conclusion:The inhouse, open‐source kV‐TPS dose calculation system was comparable within 5% of measurements and MC simulations in both homogeneous and heterogeneous phantoms. The dose calculation system of the kV‐TPS is validated as a part of initial commissioning process for small animal radiotherapy. The kV‐TPS has the potential for accurate dose calculation for any kV treatment or imaging modalities.
SU‐F‐T‐676: Measurement of Hydroxyl Radicals in Radiolized Water Systems
Authors: Ouyang Z , Strack G , Sajo E , Ngwa W 
Published: July 2016

Purpose:Hydroxyl radicals can be produced within tissue by radiation therapy, and they are largely responsible for DNA damage and cell killing. Coumarin‐3‐carboxylic acid (3‐CCA) and crystal violet are reported to react with hydroxyl radicals and can be used for fluorescence and absorbance measurements, respectively. This study assesses the ability of hydroxyl measurement for both 3‐CCA and crystal violet in radiolized water systems in order to provide dosimetric information in radiation chemistry and radiation biology experiments.Methods:3‐CCA and crystal violet were both dissolved in phosphate buffered saline (PBS, pH 7.4) with final concentrations 0.5 mg/mL and 0.05 mg/mL. 3‐CCA and control solutions (PBS only) were loaded in black bottom 96‐well plates. Crystal violet and control solutions were loaded in clear bottom 96‐well plates. The prepared solutions were irradiated at 2 Gy using a small animal radiation research platform. Fluorescence reading with 360 nm excitation wavelength and 485 nm emission wavelength was done for 3‐CCA, and absorbance reading at wavelength 580 nm was done for crystal violet before and after radiation.Results:3‐CCA showed clear difference in fluorescence before and after radiation, which suggested hydroxyl production during radiation. However, crystal violet absorbance at 580 nm was not changed significantly by radiation.Conclusion:The overall conclusion is that 3‐CCA can be used for hydroxyl measurement in radiolized water systems, while crystal violet cannot, although crystal violet is reported widely to react with hydroxyl radicals produced in Fenton reactions. Possible reasons could relate to reaction pH.
SU‐F‐T‐680: Radiobiological Analysis of the Impact of Daily Patient Deformation and Setup Variations Through the Use of the Cone Beam CT and Deformable Image Registration in Lung Cancer IMRT
Authors: Jurkovic I , Stathakis S , Markovic M , Papanikolaou N , Mavroidis P 
Published: July 2016

Purpose:To estimate the dose distributions delivered to the patient in each treatment fraction using deformable image registration (DIR) and assess the radiobiological impact of the inter‐fraction variations due to patient deformation and setup.Methods:The work is based on the cone beam CT (CBCT) images and treatment plans of two lung cancer patients. Both patients were treated with intensity modulated radiation therapy (IMRT) to 66Gy in 2Gy/fraction. The treatment plans were exported from the treatment planning system (TPS) to the Velocity AI where DIR was performed and the same deformation matrix was used for the deformation of the planned dose distribution and organ contours to each CBCT dataset. A radiobiological analysis was performed based on the radiobiological parameters of the involved organs at risk (OARs) and planning target volume (PTV). Using the complication free tumor control probability (P+) index, differences in P+ were observed between each CBCT as well as between CBCT and planning dose distributions.Results:The optimal CBCT P? values ranged from 91.6 % to 94.8 % for patient #1 and from 88.8 % to 90.6 % for patient #2. At the dose level of the clinical prescription, the CBCT P+ values ranged from 80.3% to 80.7% for patient #1 and from 80.7% to 81.0% for the patient #2. The planning CT P+ values were 81.0% and 80.7% for the two patients, respectively. These differences emphasize the significance of using the radiobiological analysis when assessing changes in the dose distribution due to the tumor motion and lung deformations.Conclusion:Daily setup variations yield to differences in the actual dose delivered versus the planned one. The observed differences were rather small when only looking at the dosimetric comparison of the dose distributions, however the radiobiology analysis was able to detect clinically relevant differences among the studied dose distributions.
SU‐G‐BRA‐13: An Advanced Deformable Lung Phantom for Analyzing the Dosimetric Impact of Respiratory Motion
Authors: Shin D , Kang S , Kim D , Kim T , Kim K , Cho M , Suh T 
Published: July 2016

Purpose:The difference between three‐dimensional (3D) and four‐dimensional (4D) dose is affected by factors such as tumor size and motion. To quantitatively analyze the effects of these factors, a phantom that can independently control for each factor is required. The purpose of this study is to develop a deformable lung phantom with the above attributes and evaluate characteristics.Methods:A phantom was designed to simulate diaphragm motion with amplitude in the range 1 to 7 cm and various periods of regular breathing. To simulate different size tumors, tumors were produced by pouring liquid silicone into custom molds created by a 3D printer. The accuracy of phantom diaphragm motion was assessed using calipers and protractor. To control tumor motion, tumor trajectories were evaluated using 4D computed tomography (CT), and diaphragm‐tumor correlation curve was calculated by curve fitting method. Three‐dimensional dose and 4D dose were calculated and compared according to tumor motion.Results:The accuracy of phantom diaphragm motion was less than 1 mm. Maximum tumor motion amplitudes in the left‐right and anterior‐posterior directions were 0.08 and 0.12 cm, respectively, in a 10 cm3 tumor, and 0.06 and 0.27 cm, respectively, in a 90 cm3 tumor. The diaphragm‐tumor correlation curve showed that tumor motion in the superior‐inferior direction was increased with increasing diaphragm motion. In the 10 cm3 tumor, the tumor motion was larger than the 90 cm3 tumor. According to tumor motion, variation of dose difference between 3D and 4D was identified.Conclusion:The developed phantom can independently control factors such as tumor size and motion. In potentially, this phantom can be used to quantitatively analyze the dosimetric impact of respiratory motion according to the factors that influence the difference between 3D and 4D dose.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)