bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐640: Feasibility of Using a Commercially Available Surface Guided Radiotherapy System with An Open‐Face SRS Immobilization System
Authors: Chinsky B , Patel R , Roeske J , Surucu M 
Published: July 2016

Purpose:To evaluate the inherent accuracy of using a surface guided radiotherapy system (SGRT) in the setup and monitoring of patients receiving stereotactic radiosurgery with an open‐face SRS immobilization system.Methods:An anthropomorphic head phantom was set up using the Qfix Encompass SRS Immobilization System on a Varian Edge with OSMS and Varian TrueBeam with AlignRT. The phantom was positioned at 0° gantry and couch. A reference image was acquired using the SGRT system and an ROI was created over the mask opening. The couch and gantry were rotated to different combinations focusing on clinically used SRS gantry/couch combinations and those blocking the SGRT cameras. Perceived surface deviation by the SGRT system from the reference image was recorded. A Winston‐Lutz test was performed on couch angles tested and used to exclude couch walkout. The deviation magnitude was calculated using translational values and rotational raw values were recorded.Results:The maximum couch walkouts were: 0.4mm (Edge) and 0.5mm (TB). Solely rotating the gantry resulted in a median couch deviation of 0.2mm and range of 0.1–0.3mm for both linacs. Only rotating the couch (0° gantry) resulted in median deviations of 0.6mm and 0.5mm with ranges of 0.3–1.0mm and 0.3–0.7mm for the Edge and TB, respectively. Combining gantry and couch rotations, the median deviations were 0.7mm and 0.9mm with ranges of 0.3–1.1mm and 0.2–1.9mm for the Edge and TB, respectively. Including all combinations, rotation, roll, and pitch median deviations ranged from 0.1–0.3° with pitch demonstrating consistently higher values and a maximum deviation of 1.0° (both linacs).Conclusion:SGRT is a reliable monitoring tool, though taking into account system fluctuations, 1mm is too restrictive a site tolerance to use with the Qfix Encompass mask. Gantry rotation has little effect on system fluctuation even with camera blockage, whereas couch rotation has a larger effect.
SU‐F‐T‐641: Comparative Study On Planning and Delivery Efficiency of Volumetric Modulated Arc Therapy Between Varian and Elekta Platforms for SBRT Lung Treatment
Authors: Varadhan  , Arentsen L , Way S , Overbeck C , Yerich S , Garrity B , Fox M 
Published: July 2016

Purpose:To compare the plan quality between Eclipse (Varian) and Monaco (Elekta) TPS. To ascertain, if SBRT lung treatment could be delivered in a single coplanar arc (360 degrees) with both Elekta and Varian platforms. To assess if the smaller leaf width in Varian Millennium and Elekta Agility MLC heads have a dosimetric advantage over Elekta MLCi2 headMethods:Ten SBRT lung patients (PTV volumes ranging from 11 cc to 103cc) who were previously treated on Varian Linac with non‐coplanar arcs and received 50Gy in 5 fractions were chosen for this study. The patients were replanned in Eclipse TPS (AAA algorithm) using a 360 degree coplanar single arc (SA) delivery technique and 2 partial complimentary 180 degree arcs (PA). Treatment planning using single coplanar arc (360 degree arc) was also done on Monaco TPS (Montecarlo) for both Agility (160 leaf) and MLCi2 (80 leaf) Elekta MLC headsResults:The average monitor units to deliver 10 Gy across all delivery methods were 3000 ± 474 MU and did not vary with PTV size. Coplanar single arc and partial arc techniques did not compromise either the RTOG 0813 or 0915 low dose spillage criteria for R50% or the maximum dose to any point 2cm away from the PTV. OAR doses to spinal cord, heart, great vessels, esophagus, rib and lung were comparable on both Eclipse (Varian) and Monaco (Elekta) platforms regardless of the delivery method.Conclusion:SBRT lung tumors can be treated with a single coplanar 360 degree arc in both Varian and Elekta platforms. Non coplanar arcs and increasing arc degrees more than 360 degrees had no benefit in this study regardless of the volume of PTV. 0.5 cm leaf width used in Millennium and Agility MLC heads had no significant dosimetric improvement over 1 cm leaves in the MLCi2 head.
SU‐F‐T‐656: Monte Carlo Study On Air Activation Around a Medical Electron Linac
Authors: Horst F , Fehrenbacher G , Zink K 
Published: July 2016

Purpose:In high energy photon therapy, several radiation protection issues result from photonuclear reactions. The activation of air ‐ directly by photonuclear reactions as well as indirectly by capture of photoneutrons generated inside the linac head ‐ is a major point of concern for the medical staff. The purpose of this study was to estimate the annual effective dose to medical workers due to activated air around a medical high energy electron linac by means of Monte Carlo simulations.Methods:The treatment head of a Varian Clinac in 18 MV‐X mode as well as the surrounding concrete bunker were modeled and the radiation transport was simulated using the Monte Carlo code FLUKA, starting from the primary electron striking the bremsstrahlung target. The activation yields in air from photo‐disintegration of O‐16 and N‐14 nuclei as well as from neutron capture on Ar‐40 nuclei were obtained from the simulations. The activation build‐up, radioactive decay and air ventilation were studied using a mathematical model. The annual effective dose to workers was estimated by using published isotope specific conversion factors.Results:The oxygen and nitrogen activation yields were in contrast to the argon activation yield found to be field size dependent. The impact of the treatment room ventilation on the different air activation products was investigated and quantified. An estimate with very conservative assumptions gave an annual effective dose to workers of < 1 mSv/a.Conclusion:From the results of this study it can be concluded that the contribution of air activation to the radiation exposure to medical workers should be negligible in modern photon therapy, especially when it is compared to the dose due to prompt neutrons and the activation of heavy solid materials such as the jaws and the collimators inside the linac head.
SU‐F‐T‐659: Nanoparticle‐Aided Eye Plaque Radiotherapy
Authors: Chin J , Ngwa W 
Published: July 2016

Purpose:Eye plaque brachytherapy is one of the approaches for radiotherapy treatment for ocular cancers: retinoblastoma and choroidal melanoma. This study, investigates the potential benefits of using gold nanoparticles to enhance therapeutic efficacy during eye plaque brachytherapy.Methods:The EYE PHYSICS Inc. Plaque Simulator program distributed by IsoAid, LLC, Port Richey, Florida was used. It is based on the superposition of dose contributions from individual seeds following the TG–43 formalism. Dose enhancement factor (DEF) values for feasible nanoparticle concentrations from previous studies was used to investigate the benefit of using nanoparticles to enhance dose to tumour or reduce dose to healthy tissue. The dose enhancement factor (DEF) represents the ratio of the dose deposited in tumour with nanoparticles divided by dose deposited in the tumour without nanoparticles. The investigation was done for I–125 and Pd–103 typical sources employed for eye plaque brachytherapy. The prescription dose used is 85 Gy.Results:Lower dose enhancement values were obtained for Pd–103. With DEF of 2 due to gold nanoparticles, critical structure doses reduce by a factor of 2. Optic disc dose is 6.69 Gy and 4.571 Gy, opposite retina dose is 4.064 and 2.484 Gy, lens dose is 12.66 Gy and 9.870 Gy, and fovea dose is 9.85 Gy and 7.275 Gy. With DEF of 3 due to gold nanoparticles, critical structure doses reduce by a factor of 3. Optic disc dose is 4.352 Gy and 2.975 Gy, opposite retina dose is 2.644 Gy and 1.618 Gy, lens dose is 8.322 Gy and 6.427 Gy, and fovea dose is 4.815 Gy and 4.737 Gy.Conclusion:The results of this research predict that using gold nanoparticles will lead to major sparing of dose to critical structures. The finding provides more impetus for the development of nanoparticle–aided brachytherapy.
SU‐F‐T‐660: Evaluating the Benefit of Using Dual‐Function Fiducial Markers for In‐Situ Delivery of Radiosenistizing Gold Nanoparticles During Image‐Guided Radiotherapy
Authors: AlMansour S , Chin J , Sajo E , Ngwa W 
Published: July 2016

Purpose:Dual‐function fiducials loaded with radiosensitizers, like gold nanoparticles (GNP), offer an innovative approach for ensuring geometric accuracy during image‐guided radiotherapy (IGRT) and significantly increasing therapeutic efficacy due to controlled in‐situ release of the radiosensitizers. This study retrospectively investigates the dosimetric benefit of using up to two such dual‐function fiducial markers instead of traditional single function fiducials during IGRT.Methods:A computational code was developed to investigate the dosimetric benefit for 10 real patient tumor volumes of up to 6.5 cm diameter. The intra‐tumoral space‐time biodistribution of the GNP was modeled as in previous studies based on Fick's second law. The corresponding dose‐enhancement for each tumor voxel due to the GNP was also calculated for clinical 6MV beam configurations. Various loading concentrations (25–50 mg/g) were studied, as a function of GNP size, to determine potential for clinically significant dose enhancement. The time between initial implantation of dual‐function fiducials to the beginning of radiotherapy was assumed to be 14 days as typical for many clinics.Results:A single dual‐function fiducial could achieve at least a DEF of 1.2 for patients with tumors less than 1.4 cm diameter after 14 days. Replacing two single function fiducials with dual‐function ones at the same locations achieved at least the required minimal DEF for tumors that are 2 cm diameter in 3 patients. The results also revealed dosimetrically better fiducial locations which could enable significant DEF when using one or two dual function fiducials. 2 nm sizes showed the most feasibility.Conclusion:The results highlight the potential of tumor sub‐volume radiation boosting using GNP released from fiducials, and the ability to customize the DEF throughout the tumor by using two dual‐function fiducials, varying the initial concentration and nanoparticle size. The results demonstrate potential for employing dual‐function fiducials in the development of GNP‐aided radiotherapy.
SU‐F‐T‐668: Irradiating Mouse Brain with a Clinical Linear Accelerator
Authors: Perez‐Torres C 
Published: July 2016

Purpose:To design and construct a “mouse jig” device that would allow for irradiation of the mouse brain with a clinical Varian 6 MeV Linear Accelerator. This device must serve as a head immobilizer, gaseous anesthesia delivery, and radiation bolus concurrently.Methods:The mouse jig was machined out of nylon given that it is inexpensive, easy to machine, and has similar electron density to water. A cylindrical opening with diameter of 16 mm and 40 mm depth was drilled into a nylon block sized 56×56×50 mm (width, length, depth). Additional slots were included in the block for ear bars and a tooth bar to serve as a three‐point immobilization device as well as for anesthesia delivery and scavenging. For ease of access when loading the mouse into the holder, there is a removable piece at the top of the block that is 15 mm in depth. This serves a dual purpose, as with the proper extra shielding, the mouse jig could be used with lower linear energy transfer photons with this piece removed. A baseplate was then constructed with five square slots where the mouse jig can securely be inserted plus additional slots that would allow the baseplate to be mounted on a standard lock bar in the treatment couch. This maximizes the reproducibility of placement between imaging and treatment and between treatment sessions.Results:CT imaging and radiation treatment planning was performed that showed acceptable coverage and uniformity of radiation dose in the mouse brain while sparing the throat and eyes.Conclusion:We have designed and manufactured a device that fulfills our criteria allowing us to selectively irradiate the mouse brain with a clinical linear accelerator. This setup will be used for generating mouse models of radiation‐induced brain injury.
SU‐F‐T‐670: From the OR to the Radiobiology Lab: The Journey of a Small X‐Ray Source
Authors: Lehmann J , Barry M , Jones R , Fay M 
Published: July 2016

Purpose:Irradiation of small animal tumor models within laboratories is vital to radiobiological experiments. Often the animals are not able to be brought back into the lab after being taken out for irradiation. Cell biology laboratories benefit from irradiation capability available around the clock without regard to patient load in an associated radiotherapy clinic. Commercial systems are available, but bulky and expensive.Methods:An intraoperative kV irradiation system (IntraBeam™) designed to deliver spherical dose distributions to surgical cavities has been repurposed for the irradiation of cell plates and small laboratory animals. An applicator has been altered to allow for simple, open fields. Special collimators are being developed. BEAMnrc Monte Carlo simulations with the “NRC swept BEAM” source model have been performed to characterize the dose distributions, to develop optimal collimators and as basis for dose prescription. Measurements with radiochromic film and with an ionization chamber were performed to characterize the beam and to validate the simulations.Results:Using its highest setting (50 kV and 40 µA) the x‐ray unit is capable of delivering dose rates over 1 Gy/min homogeneously to standard cell plates even without an optimized collimator. Smaller areas (tumors in animals) can be irradiated with significantly higher dose rates (> 20 Gy/min) depending on distance of the source to the tumor. The HVL was found to be 0.21 mm Al which means the shielding requirements for the device are easily achievable in the lab.Conclusion:A mobile irradiation facility is feasible. It will allow easier access to radiation for radiobiology experiments. The modified system is versatile in that for cell plates homogenous irradiations can be achieved through distance from the source, while for high dose rate small field irradiations the source can be brought in close proximity to the target.
SU‐F‐T‐673: Effects of Cardiac Induced Brain Pulsations On Proton Minibeams
Authors: Eagle J , Marsh S , Lee E , Meyer J 
Published: July 2016

Purpose:To quantify the dosimetric impact of internal motion within the brain on spatially modulated proton minibeam radiation therapy (pMRT) for small animal research.Methods:The peak‐to‐valley dose ratio (PVDR) is an essential dosimetric factor for pMRT. Motion of an animal brain caused by cardiac‐induced pulsations (CIP) can impact dose deposition. For synchrotron generated high dose rate X‐ray microbeams this effect is evaded due to the quasi‐instantaneous delivery. By comparison, pMRT potentially suffers increased spread due to lower dose rates. However, for a given dose rate it is less susceptible to beam spread than microbeams, due to the spatial modulation being an order of magnitude larger. Monte Carlo simulations in TOPAS were used to model the beam spread for a 50.5MeV pMRT beam. Motion effects were simulated for a 50mm thick brass collimator with 0.3mm slit width and 1.0mm center‐to‐center spacing in a water phantom. The maximum motion in a rat brain due to CIP has been reported to be 0.06mm. Motion was simulated with a peak amplitude in the range 0–0.2mm.Results:The impact of 0.06mm peak motion was minimal and reduced the PVDR by about 1% at a depth of 10mm. For 0.2mm peak motion the PVDR was reduced by 16% at a depth of 10mm.Conclusion:For the pMRT beam the magnitude of cardiac‐induced brain motion has minimal impact on the PVDR for the investigated collimator geometry. For more narrow beams the effect is likely to be larger. This indicates that delivery of pMRT to small animal brains should not be affected considerably by beamlines with linac compatible dose rates.
SU‐F‐T‐674: In Vitro Study of 5‐Aminolevulinic Acid‐Mediated Photo Dynamic Therapy in Human Cancer Cell Lines
Authors: Cvetkovic D , Wang B , Gupta R , Ma C 
Published: July 2016

Purpose:Photodynamic therapy (PTD) is a promising cancer treatment modality. 5‐sminolevulinic acid (ALA) is a clinically approved photosensitizer. Here we studied the effect of 5‐ALA administration with irradiation on several cell lines in vitro.Methods:Human head and neck (FaDu), lung (A549) and prostate (LNCaP) cancer cells (104/well) were seeded overnight in 96‐well plates (Figure 1). 5‐ALA at a range from 0.1 to 30.0mg/ml was added to confluent cells 3h before irradiation in 100ul of culture medium. 15MV photon beams from a Siemens Artiste linear accelerator were used to deliver 2 Gy dose in one fraction to the cells. Cell viability was evaluated by WST1 assay. The development of orange color was measured 3h after the addition of WST‐1 reagent at 450nm on an Envision Multilabel Reader (Figure 2) and directly correlated to cell number. Control, untreated cells were incubated without 5‐ALA. The experiment was performed twice for each cell line.Results:The cell viability rates for the head and neck cancer line are shown in Figure 3. FaDu cell viability was reduced significantly to 36.5% (5‐ALA) and 18.1% (5‐ALA + RT) only at the highest concentration of 5‐ALA, 30mg/ml. This effect was observed in neither A549, nor LNCaP cell line. No toxicity was detected at lower 5‐ALA concentrations.Conclusion:Application of 5‐ALA and subsequent PDT was found to be cytotoxic at the highest dose of the photosensitizer used in the FaDu head and neck cell line, and their effect was synergistic. Further efforts are necessary to study the potential therapeutic effects of 5‐ALA PTD in vitro and in vivo. Our results suggest 5‐ALA may improve the efficacy of radiotherapy by acting as a radiomediator in head and neck cancer.
SU‐F‐T‐675: Down‐Regulating the Expression of Cdc42 and Inhibition of Migration of A549 with Combined Treatment of Ionizing Radiation and Sevoflurane
Authors: Feng Y , Feng J , Huang Z 
Published: July 2016

Purpose:Cdc42 is involved in cell transformation, proliferation, invasion and metastasis of human cancer cells. Cdc42 overexpression has been reported in several types of cancers. This study investigated the combined treatment effects of ionizing radiation and sevoflurane on down‐regulating Cdc42 expression and suppressing migration of human adenocarcinoma cell line A549.Methods:Samples of A549 cells with Cdc42 overexpression were created and Cdc42 expression was determined by Western blotting. Increase of migration speed by Cdc42‐HA overexpression was confirmed with an initial in‐vitro scratch assay. The cells grown in culture media were separated into 2 groups of 6 samples: one for the control and the other was treated with 4% sevoflurane for 5hrs prior to a single‐fraction radiation of 4Gy using a 6MV beam. Cell migration speeds of the 2 groups were measured with an initial in‐vitro scratch assay. The scratch was created with a pipette tip immediately after treatment and images at 4 post‐treatment time points (0h, 3h, 6h, 12h) were acquired. The distance between the two separated sides at 0h was used as reference and subsequent changes of the distance over time was defined as the cell migration speed. Image processing and measurement were performed with an in‐house software. The experiment was repeated three times independently to evaluate the repeatability and reliability. Statistical analysis was performed with SPSS 19.0.Results:Western blotting showed the treatment down‐regulated Cdc42 overexpression. Quantitative analysis and two‐tailed t‐test showed that cell migration speed of the treated group was higher than the control group at all time points after treatment (p < 0.02).Conclusion:Combined treatment of 6MV photon and sevoflurane can cause the effects of down‐regulating Cdc42 overexpression and decrease of migration speed of A549 cells which provides potential of clinical benefit for the cancer therapy. More investigation is needed to further quantify the benefits of the combined therapy.
SU‐F‐T‐678: Clotrimazole Sensitizes MCF‐7 Breast Cancer Cell Line to Radiation
Authors: Garcia L , Tambasco M 
Published: July 2016

Purpose:To study the effects of Clotrimazole (CLT) on radiosensitivity of MCF‐7 Cells in correlation to detachment of Hexokinase II from the Voltage Dependent Anion Channel on the outer membrane of the mitochondria. Apoptotic fractions were also analyzed in relation to the detachment of Hexokinase.Methods:This study focused on the mammary adenocarcinoma cell line, MCF‐7. Colony forming assays were used to analyze radiosensitization by CLT. Flow cytometry methods were used to analyze apoptotic vs necrotic fractions after treatment with CLT. Spectrophotometery was used to analyze the mitochondrial bound and soluble fraction of Hexokinase by means of relative enzymatic activity.Results:Our preliminary data have shown that CLT sensitizes MCF‐7 cells to radiation in a dose and incubation time dependent manner up. We have also demonstrated that there are two radiosensitizing periods in MCF‐7 cells with the first corresponding to the cycle arrest after 24 hours observed in other cell lines. The second radiosensitizing period occurs with incubation in CLT after irradiation which reaches maximum effect around 24 hours of incubation time. Preliminary data from our Hexokinase detachment assay show a factor of two increase in the ratio of unbound to bound Hexokinase when comparing incubation for 24 hours in media containing 0 and 20 µM CLT.Conclusion:This study and others indicate CLT as a possible radiosensitizing agent in cancer therapies. While CLT itself shows toxicity to the liver in high doses, this study further demonstrates that disruption of the Warburg Effect and unbinding of mitochondrial bound Hexokinase as a possible pathway for cancer treatment.
SU‐G‐206‐03: CTDI Per KV at Phantom Center and Periphery: Comparison Between Major CT Manufacturers
Authors: Al‐Senan R , Demirkaya O 
Published: July 2016

Purpose:The purpose of this study was to: 1) compare scanners output by measuring normalized CTDIw (mGy/100mAs) in different CT makes and models and at different kV's, and 2) quantify the relationship between kV and CTDI and compare this relationship between the different manufacturers.Methods:Study included forty scanners of major CT manufacturers and of various models. Exposure was measured at center and 12 o'clock holes of head and body CTDI phantoms, at all available kV's, and with the largest or second largest available collimation in each scanner. Average measured CTDI's from each CT manufacturer were also plotted against kV and the fitting equation: CTDIw (normalized) = a.kVb was calculated. The power (b) value may be considered as an indicator of spectral filtration, which affects the degree of beam hardening. Also, HVLs were measured at several scanners.Results:Results showed GE scanners, on average, had higher normalized CTDIw than those of Siemens and Philips, in both phantom sizes and at all kV's. ANOVA statistic indicated the difference was statistically significant (p < 0.05). Comparison between Philips and Siemens, however, was not statistically significant. Curve fitting showed b values ranged from 2.4 to 2.9 (for Head periphery and center, respectively); and was about 2.8 for Body phantom periphery, and 3.2 at the center of Body phantom. Fitting equations (kV vs. CTDI) will be presented and discussed. GE's CTDIw vs. HVL showed very strong correlation (r > 0.99).Conclusion:Partial characterization of scanners output was performed which may be helpful in dose estimation to internal organs. The relatively higher output from GE scanners may be attributed to lower filtration. Work is still in progress to obtain CTDI values from other scanners as well as to measure their HVLs.