bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐G‐JeP3‐03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate
Authors: Gerlach S , Kuhlemann I , Ernst F , Fuerweger C , Schlaefer A 
Published: July 2016

Purpose:Ultrasound presents a fast, volumetric image modality for real‐time tracking of abdominal organ motion. How‐ever, ultrasound transducer placement during radiation therapy is challenging. Recently, approaches using robotic arms for intra‐treatment ultrasound imaging have been proposed. Good and reliable imaging requires placing the transducer close to the PTV. We studied the effect of a seven degrees of freedom robot on the fea‐sible beam directions.Methods:For five CyberKnife prostate treatment plans we established viewports for the transducer, i.e., points on the patient surface with a soft tissue view towards the PTV. Choosing a feasible transducer pose and using the kinematic redundancy of the KUKA LBR iiwa robot, we considered three robot poses. Poses 1 to 3 had the elbow point anterior, superior, and inferior, respectively. For each pose and each beam starting point, the pro‐jections of robot and PTV were computed. We added a 20 mm margin accounting for organ / beam motion. The number of nodes for which the PTV was partially of fully blocked were established. Moreover, the cumula‐tive overlap for each of the poses and the minimum overlap over all poses were computed.Results:The fully and partially blocked nodes ranged from 12% to 20% and 13% to 27%, respectively. Typically, pose 3 caused the fewest blocked nodes. The cumulative overlap ranged from 19% to 29%. Taking the minimum overlap, i.e., considering moving the robot's elbow while maintaining the transducer pose, the cumulative over‐lap was reduced to 16% to 18% and was 3% to 6% lower than for the best individual pose.Conclusion:Our results indicate that it is possible to identify feasible ultrasound transducer poses and to use the kinematic redundancy of a 7 DOF robot to minimize the impact of the imaging subsystem on the feasible beam directions for ultrasound guided and motion compensated SBRT.Research partially funded by DFG grants ER 817/1‐1 and SCHL 1844/3‐1.
SU‐G‐JeP3‐09: Tumor Location Prediction Using Natural Respiratory Volume for Respiratory Gated Radiation Therapy (RGRT): System Verification Study
Authors: Kim M , Jung J , Yoon D , Shin H , Kim S , Suh T 
Published: July 2016

Purpose:Respiratory gated radiation therapy (RGRT) gives accurate results when a patient's breathing is stable and regular. Thus, the patient should be fully aware during respiratory pattern training before undergoing the RGRT treatment. In order to bypass the process of respiratory pattern training, we propose a target location prediction system for RGRT that uses only natural respiratory volume, and confirm its application.Methods:In order to verify the proposed target location prediction system, an in‐house phantom set was used. This set involves a chest phantom including target, external markers, and motion generator. Natural respiratory volume signals were generated using the random function in MATLAB code. In the chest phantom, the target takes a linear motion based on the respiratory signal. After a four‐dimensional computed tomography (4DCT) scan of the in‐house phantom, the motion trajectory was derived as a linear equation. The accuracy of the linear equation was compared with that of the motion algorithm used by the operating motion generator. In addition, we attempted target location prediction using random respiratory volume values.Results:The correspondence rate of the linear equation derived from the 4DCT images with the motion algorithm of the motion generator was 99.41%. In addition, the average error rate of target location prediction was 1.23% for 26 cases.Conclusion:We confirmed the applicability of our proposed target location prediction system for RGRT using natural respiratory volume. If additional clinical studies can be conducted, a more accurate prediction system can be realized without requiring respiratory pattern training.
SU‐G‐TeP3‐03: Dose Enhancement of Gold Nanoparticle in Proton Therapy: A Monte Carlo Study Based On the Transmission Electron Microscopy Imaging
Authors: Ma Y , Laprise‐Pelletier M , Lagueux J , Cote M , Fordin M , Beaulieu L 
Published: July 2016

Purpose:Gold nanoparticle (GNP) is a promising radiosensitizer that selectively boosts tumor dose in radiotherapy. Transmission electron microscopy (TEM) imaging observations recently revealed for the first time that GNP exists in vivo in the form of highly localized vesicles, instead of hypothetical uniform distribution. This work investigates the corresponding difference of energy deposition in proton therapy.Methods:First, single vesicles of various radii were constructed by packing GNPs (as Φ50 nm gold spheres) in spheres and were simulated, as well as a single GNP. The radial energy depositions (REDs) were scored using 100 concentric spherical shells from 0.1µm to 10µm, 0.1µm thickness each, for both vesicles and GNP, and compared. TEM images, 8 days after injection in a PC3 prostate cancer murine model, were used to extract position/dimension of vesicles, as well as contours of cytoplasmic and nucleus membranes. Vesicles were then constructed based on the TEM images. A 100 MeV proton beam was studied by using the Geant4‐DNA code, which simulates all energy deposition events.Results:The vesicle REDs, normalized to the same proton energy loss as in a single GNP, are larger (smaller) than that of a single GNP when radius >2µm (<2µm). The peak increase (at about 3µm radius) is about 10% and 18% for Φ1µm and Φ1.6µm vesicles respectively, relative to a single GNP. The TEM‐based simulation resulted in a larger energy deposition (by about one order of magnitude) that follows completely different pattern from that of hypothetical GNP distributions (regular dotted pattern in extracellular and/or extranucleus regions).Conclusion:The in vivo energy deposition, both in pattern and magnitude, of proton therapy is greatly affected by the true distribution of the GNP, as illustrated by the presence of GNP vesicles compared to hypothetical scenarios.Work supported by NSERC Discovery Grant #435510, Canada
SU‐G‐TeP3‐04: Evaluation of the Dose Enhancement with Gold Nanoparticle in Microdosimetry Level Using the Geant4‐DNA Toolkit
Authors: He C , Chow J 
Published: July 2016

Purpose:This study investigated the dose enhancement effect of using gold nanoparticles (GNP) as radiation sensitizers radiated by different photon beam energies. Microdosimetry of photon‐irradiated GNP was determined by the Geant4‐DNA process in the DNA scale.Methods:Monte Carlo simulation was conducted using the Geant4 toolkit (ver. 10.2). A GNP with different sizes (30, 50, and 100nm diameter sphere) and a DNA were placed in a water cube (1µm3). The GNP was irradiated by photon beams with different energies (50, 100, and 150keV) and produced secondary electrons to increase the dose to the DNA. Energy depositions were calculated for both with and without GNP and to investigate the dose enhancement effect at the DNA. The distance between the GNP and DNA was varied to optimize the best GNP position to the DNA. The photon beam source was set to 200nm from the GNP in each simulation.Results:It is found that GNP had a dose enhancement effect on kV photon radiations. For Monte Carlo results on different GNP sizes, distances between the GNP and DNA, and photon beam energies, enhancement ratio was found increasing as GNP size increased. The distance between the GNP and DNA affected the result that as distance increased while the dose enhancement ratio decreased. However, the effect of changing distance was not as significant as varying the GNP size. In addition, increasing the photon beam energy also increased the dose enhancement ratio. The largest dose enhancement ratio was found to be 3.5, when the GNP (100nm diameter) irradiated by the 150keV photon beam was set to 80nm from the DNA.Conclusion:Dose enhancement was determined in the DNA with GNP in the microdosimetry scale. It is concluded that the dose enhancement varied with the photon beam energy, GNP size and distance between the GNP and DNA.
SU‐G‐TeP3‐05: In Vitro Demonstration of Endothelial Dose Enhancement Due to Gold Nanoparticles During Low‐Voltage Radiotherapy
Authors: Yasmin‐Karim S , Moreau M , Kumar R , Makrigiorgos GM , Hanlon J , Arnoldussen M , Hempstead J , Celli J , Ngwa W 
Published: July 2016

Purpose:Oraya Therapy uses low‐voltage, stereotactic, highly targeted X‐rays for the treatment of wet age‐related macular degeneration (AMD) — offering a new option for patients worldwide. Neovascular endothelial cells play a crucial role in the pathogenesis of this disease. This in‐vitro study investigates the potential of gold nanoparticles (GNP) to enhance endothelial cell damage during low‐voltage radiotherapy towards potential applications in the treatment of wet‐AMD.Methods:Primary human umbilical cord vein endothelium cells (HUVEC) were treated with 1.4 nm sized GNPs for 24 hrs and then irradiated with variable X‐ray doses using an Oraya therapy system (100 kVp) or a Small Animal Radiation and Research platform (SARRP) at other beam qualities (up to 220 kVp). Radio‐sensitization was assessed by clonogenic assays. Variable concentrations of GNPs (0.05 mg/ml, 0.1 mg/ml, 0.25 mg/ml, 0.5 mg/ml, and 1 mg/ml) where employed. The dose enhancement factor (DEF) was calculated as the ratio of radiation doses required to give the same biological effect (survival factor, SF) with and without GNPs.Results:Preliminary results show DEFs of up to 2.62 for the different combinations of x‐ray doses and GNP concentrations and beam qualities. In general the DEF increased with increase in GNP concentration. However, for high doses the effect of GNP becomes less apparent likely due to already high cell kill by the radiation alone.Conclusion:The findings suggest that targeted GNPs can play a significant synergistic role in enhancing stereotactic radiosurgery for wet AMD. The results also provide impetus for ongoing studies to find the optimal synergy between the doses or beam energies and GNPs concentration. This will benefit in‐vivo studies towards development of nanoparticle‐aided radiotherapy for treatment of wet‐AMD and potentially ocular cancers.
SU‐G‐TeP3‐12: Retrospective Assessment of R2star Using Ultra‐High Field MRI in a Rodent Model of Radiation Necrosis
Authors: Belliveau J , Menon R 
Published: July 2016

Purpose:To establish a quantitative MRI method that would be capable of predicting radiation necrosis without using a contrast agent.Methods:Healthy male Fischer 344 rats were irradiated using an animal irradiator capable of delivering 2.3 Gy/min with a kVp of 225 V. A dose of 40 Gy was given to half the brain in a single session. Rats were scanned using a 9.4 T animal MRI before irradiation and every two weeks following radiation until either necrosis developed or they were sacrificed for health reasons. A multi‐echo gradient‐echo sequence was acquired at every time point and the apparent transverse relaxation rate R2* was calculated based on the measured signal decay. At the last time point, an ROI mask with an R2* value of greater than 45 s−1 was applied in the area of the external and internal capsule where radiation necrosis was confirmed. A retrospective analysis was performed to determine whether R2* values would be able to predict where radiation necrosis would occur.Results:Radiation necrosis was morphologically visible between weeks 22–24 following treatment. Gadolinium MRI and histology confirmed radiation necrosis in the area of MRI enhancement. Our data suggests that there is a trend towards significance in the lesion as early as 12 weeks prior to morphological changes on MRI with significance occurring 6 weeks prior (p≤0.05, p≤0.01 at week 24). Measurements of the R2* in the hippocampus did not show any significant difference; however, there are areas of visible R2* change within sub‐hippocampal regions.Conclusion:R2* is a promising method that could be able to predict an underlying disease process that occurs prior to radiation necrosis. The constant increase in R2* values suggests a possible neuroinflammatory mechanism rather than an acute vascular event where R2* would tend to decrease in the area.
SU‐G‐IeP4‐04: DD‐Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study
Authors: Fong G , Kapadia A 
Published: July 2016

Purpose:To optimize collimation and shielding for a deuterium‐deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT).Methods:Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm3 polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source‐side and target‐side openings) and aperture placements (13–39 cm from source‐side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system.Results:Analysis of primary beam indicated the beam‐width is linear to the aperture size. Increasing source‐side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings.Conclusion:The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well‐defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan time should be considered to determine the optimal design for specific NSECT applications.
SU‐G‐IeP4‐11: Monitoring Tumor Growth in Subcutaneous Murine Tumor Model in Vivo: A Comparison Between MRI and Small Animal CT
Authors: Wang B , He W , Cvetkovic D , Chen L , Fan J , Ma C 
Published: July 2016

Purpose:The purpose of the study is to compare the volume measurement of subcutaneous tumors in mice with different imaging platforms, namely a GE MRI and a Sofie‐Biosciences small animal CT scanner.Methods:A549 human lung carcinoma cells and FaDu human head and neck squamous cell carcinoma cells were implanted subcutaneously into flanks of nude mice. Three FaDu tumors and three A549 tumors were included in this study. The MRI scans were done with a GE Signa 1.5 Tesla MR scanner using a fast T2‐weighted sequence (70mm FOV and 1.2mm slice thickness), while the CT scans were done with the CT scanner on a Sofie‐Biosciences G8 PET/CT platform dedicated for small animal studies (48mm FOV and 0.2mm slice thickness). Imaging contrast agent was not used in this study. Based on the DICOM images from MRI and CT scans, the tumors were contoured with Philips DICOM Viewer and the tumor volumes were obtained by summing up the contoured area and multiplied by the slice thickness.Results:The volume measurements based on the CT scans agree reasonably with that obtained with MR images for the subcutaneous tumors. The mean difference in the absolute tumor volumes between MRI‐ and CT‐based measurements was found to be −6.2% ± 1.0%, with the difference defined as (VMR – VCT)*100%/VMR. Furthermore, we evaluated the normalized tumor volumes, which were defined for each tumor as V/V0 where V0 stands for the volume from the first MR or CT scan. The mean difference in the normalized tumor volumes was found to be 0.10% ± 0.96%.Conclusion:Despite the fact that the difference between normal and abnormal tissues is often less clear on small animal CT images than on MR images, one can still obtain reasonable tumor volume information with the small animal CT scans for subcutaneous murine xenograft models.
SU‐G‐JeP4‐08: External and Internal Motion Assessments with Amplitude and Time Based Reconstruction and AveCT
Authors: Fogg P , Aland T , West M 
Published: July 2016

Purpose:To investigate the effects of external surrogate and tumour motion by observing the reconstructed phases and AveCT in an Amplitude and Time based 4DCT.Methods:Based on patient motion studies, Cos6 and sinusoidal motions were simulated as external surrogate and tumour motions in a motion phantom. The diaphragm and tumour motions may or may not display the same waveform therefore the same and different waveforms were programmed into the phantom, scanned and reconstructed based on Amplitude and Time. The AveCT and phases were investigated with these different scenarios. The AveCT phantom images were also compared with CBCT phantom images programmed with the same motions.Results:For the same surrogate and tumour sin motions, the phases (Amplitude and Time) and AveCT indicated similar motions based on the position of the BB at the slice and displayed contrast values respectively. For cos6 motions, due to the varied time the tumour spends at each position, the Amplitude and Time based phases differed. The AveCT images represented the actual tumour motions and the Time and Amplitude based phases were represented by the surrogate with varied times.Conclusion:Different external surrogate and tumour motions may result in different displayed image motions when observing the AveCT and reconstructed phases. During the 4DCT, the surrogate motion is readily available for observation of the amplitude and time of the diaphragm position. Following image reconstruction, the user may need to observe the AveCT in addition to the reconstructed phases to comprehend the time weightings of the tumour motion during the scan. This may also apply to 3D CBCT images where the displayed tumour position in the images is influenced by the long duration of the CBCT. Knowledge of the tumour motion represented by the greyscale of the AveCT may also assist in CBCT treatment beam verification matching.
SU‐G‐JeP4‐13: Continuous Intra‐Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation
Authors: Parsons D , Robar J 
Published: July 2016

Purpose:The focus of this work is to improve the available kV image quality for continuous intra‐fraction monitoring of the prostate. This is investigated using a novel blade collimation system enabling modulated volume‐of‐interest (VOI) imaging of prostate fiducial markers.Methods:A four‐blade dynamic kV collimator was used to track a VOI during gantry rotation. Planar image quality was investigated as a function of collimator dimension, while maintaining the same dose to isocenter, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert. A sample prostate anatomy was defined in the planning system, including three fiducial markers within the CTV. The VOI margin around each marker was set to be 2σ of the population covariance matrix characterizing prostate motion. DRRs were used to calculate the kV attenuation for each VOI as a function of angle. The optimal marker and tube current were determined using kV attenuation. Monte Carlo simulations were used to calculate the imaging dose to the phantom and MV scatter dose to the imaging panel.Results:Preliminary measurements show an increase in CNR by a factor of 1.3 with the VOI method, when decreasing from an 6×6 to 2×2 cm2 field. Attenuation calculations show a change in kV fluence at the detector by a factor of 21.6 with fiducial optimization; resultant tube current modulation increases maximum dose by a factor of 1.4 compared to no modulation. MV scatter contribution to the kV detector changes by approximately a factor of two over a complete gantry rotation.Conclusion:The dynamic collimation system allows single fiducial marker tracking at a very low dose, with reduction of scatter and improvement of image quality, compared to imaging the entire prostate. The approach is compatible with tube current modulation, which enables consistent image quality throughout the range of gantry rotation.This project was funded by Varian Medical Systems.
SU‐G‐TeP4‐01: A High Resolution Pre‐Treatment VMAT QA Technique Based On EPID for Single Isocenter Multiple Mets Stereotactic Radiosurgery
Authors: Wu Q , Adamson J , Liang B , Liu B , Zhou F 
Published: July 2016

Purpose:For multiple mets radiosurgery, it is advantageous to use VMAT with a single isocenter for the ease in planning and efficiency in delivery. Insightful pre‐treatment QA for these cases is difficult to obtain because (1) target size is often small and the same order of magnitude as the detector size for commercial array based VMAT pre‐treatment QA devices; and furthermore (2) targets are located away from central axis where the array detectors are located. In this study, we present and validate an in‐house developed VMAT QA technique that is capable of addressing these challenges.Methods:The VMAT plan is delivered on a Varian Truebeam STX with HDMLC. The MV cine images are converted to portal dose (PD) after calibration. The gantry and MU index encoded in each image are used to extract a sub‐arc from the plan to compute corresponding PD. A 3D matrix is constructed with the 3rd axis representing gantry angle for subsequent γ‐analysis. The EPID has a resolution of 0.8×0.8 mm2 and field size up to 40×30 cm2. Measurements were performed for 21 arcs from 4 patients. Average(range) number of mets is 7(4–9), with volume of 0.36(0.01–1.39)cc. Varian's integrated PD was compared.Results:In PD analysis with 3%, 3mm, and 5% in threshold, pass rate of γ>1.0 is (99.6±0.3)%. Our EPID 3D analysis has the pass rate of (98.8±0.9)%, with additional criteria of 3° in angle‐to‐agreement. Projecting the 3D matrix along each axis, our analysis is reduced to 3 2D analyses, with one mimicking PD analysis at (99.0±0.9)%. Results on other planes are (99.5±0.4)% and (99.5±0.4)%, respectively. Additional criteria can be chosen to diagnose potential treatment abnormalities.Conclusion:We have developed an efficient EPID‐based QA technique for VMAT that has sufficient spatial and gantry angular resolution for use with single isocenter VMAT radiosurgery of multiple mets.