bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐540: Comprehensive Fluence Delivery Optimization with Multileaf Collimation
Authors: Weppler S , McGeachy P , Villarreal‐Barajas J , Khan R 
Published: July 2016

Purpose:Multileaf collimator (MLC) leaf sequencing is performed via commercial black‐box implementations, on which a user has limited to no access. We have developed an explicit, generic MLC sequencing model to serve as a tool for future investigations of fluence map optimization, fluence delivery optimization, and rotational collimator delivery methods.Methods:We have developed a novel, comprehensive model to effectively account for a variety of transmission and penumbra effects previously treated on an ad hoc basis in the literature. As the model is capable of quantifying a variety of effects, we utilize the asymmetric leakage intensity across each leaf to deliver fluence maps with pixel size smaller than the narrowest leaf width. Developed using linear programming and mixed integer programming formulations, the model is implemented using state of the art open‐source solvers. To demonstrate the versatility of the algorithm, a graphical user interface (GUI) was developed in MATLAB capable of accepting custom leaf specifications and transmission parameters. As a preliminary proof‐ofconcept, we have sequenced the leaves of a Varian 120 Leaf Millennium MLC for five prostate cancer patient fields and one head and neck field. Predetermined fluence maps have been processed by data smoothing methods to obtain pixel sizes of 2.5 cm2. The quality of output was analyzed using computer simulations.Results:For the prostate fields, an average root mean squared error (RMSE) of 0.82 and gamma (0.5mm/0.5%) of 91.4% were observed compared to RMSE and gamma (0.5mm/0.5%) values of 7.04 and 34.0% when the leakage considerations were omitted. Similar results were observed for the head and neck case.Conclusion:A model to sequence MLC leaves to optimality has been proposed. Future work will involve extensive testing and evaluation of the method on clinical MLCs and comparison with black‐box leaf sequencing algorithms currently used by commercial treatment planning systems.
SU‐F‐T‐625: Optimal Treatment Planning Strategy Among Arc Arrangements for Prostate SBRT with VMAT Technique
Authors: Chung J , Kang S , Suh T , Lee J , Kim J , Eom K 
Published: July 2016

Purpose:The purpose of this study is to determine the optimal treatment planning strategy among the different arc arrangements for prostate stereotactic body radiotherapy (SBRT) plans with volumetric modulated arc therapy (VMAT).Methods:Ten patients with prostate cancer were selected. The SBRT‐VMAT plans for each patient were generated with single‐full (181° to 179°; 1FA), single‐partial (240° to 120°; 1PA), double‐full (181° to 179° and 179° to 181°; 2FA), and double‐partial (240° to 120° and 120° to 240°; 2PA) arc arrangements. The prescription dose was 42.7 Gy in 7 fractions. Dose distribution was calculated using a 10‐MV flattening‐filter‐free beam and the Acuros XB algorithm. Dosimetric parameters of target volume and organs at risk (OARs) were evaluated from cumulative dose‐volume histograms on prostate SBRT‐VMAT plans between single‐arc (1FA and 1PA) and double‐arc (2FA and 2PA) arrangements.Results:All plans using four arc arrangements were highly conformal with conformity index (CI)<1.05 and conformation number (CN)=0.91, and the doses to target volume were homogeneous (homogeneity index (HI)= 0.09 0.12). Pertaining to the dose to the OARs, there were significant differences in the rectum, left and right femoral head doses while having no difference in the bladder dose. The partial‐arc (1PA and 2PA) had relatively high reductions for the mean rectum dose compared to full‐arc (1FA and 2FA). The near‐to‐maximum dose (D2%) and mean dose of the left and right femoral head were always lower on prostate SBRT‐VMAT plan using the full‐arc, when compared to the partial‐arc arrangement.Conclusion:This study confirmed that prostate SBRT‐VMAT using 1PA was feasible fast delivery time and produced equivalent target coverage and better rectum sparing, although the D2% and mean dose of the left and right femoral head increased slightly. Therefore, the results of this study suggest that the use of 1PA is an attractive choice for delivering prostate SBRT‐VMAT.
SU‐F‐T‐630: Energy Spectral Study On Lipiodol After Trans‐Arterial Chemoembolization Using the Flattened and Unflattened Photon Beams
Authors: Kawahara D , Ozawa S , Saito A , Nishio T , Hioki K , Masuda H , Okumura T , Ochi Y , Nakashima T , Suzuki T , Tanaka S , Ohno Y , Nagata Y 
Published: July 2016

Purpose:SBRT combining transarterial chemoembolization with Lipiodol is expected to improve local control. Our showed that the dose enhancement effect in the Lipiodol with 10X flattening filter free (FFF) was inserted. This study was to investigate the energy fluence variations of electron in the Lipiodol using flattened (FF) and FFF beams.Methods:FF and FFF for 6X and 10X beams by TrueBeam were used in this study. The Lipiodol (3 X 3 X 3 cm3) was located at the depth of 5 cm in water, the dose enhancement factor (DEF) and energy fluence were calculated by Monte Carlo (MC) calculations (PHITS).Results:DEFs with FF and FFF of 6X were 17.1% and 24.3% at rebuild‐up region in the Lipiodol (5.3cm depth), 7.0% and 17.0% at the center of Lipiodol (6.5cm depth), and −13.2% and −8.2% at behind Lipiodol (8.3cm depth). DEFs with FF and FFF of 10X were 21.7% and 15.3% at rebuild‐up region, 8.2% and 10.5% at the center of Lipiodol, and −14.0% and −8.6% at behind Lipiodol. Spectral results showed that the FFF beam contained more low‐energy (0–0.3MeV) component of electrons than FF beam, and FF beam contained more high‐energy (over 0.3MeV) electrons than FFF beam in Lipiodol. Behind the Lipiodol, build‐down effect with FF beam was larger than FFF beam because FF beam contained more high energy electrons. The difference of DEFs between FFF and FF beams for 6X were larger than for 10X. This is because 10X beam contained more high‐energy electrons. Conclusion: It was found that the 6XFFF beam gives the largest change of energy fluence and the largest DEF in this study. These phenomena are mainly caused by component of low‐energy electrons, and this energy is almost correspond to the boundary of photo electronic dominant and Compton scattering dominant region for photon beams.
SU‐F‐T‐635: Lung SBRT: Dosimetric and Treatment Time Comparison of Volumetric‐Modulated Arc Therapy and Three‐Dimensional Conformal Radiotherapy in Clinically Treated Cases
Authors: Han J , Xu Z , Baker J , Hsia A , Ryu S 
Published: July 2016

Purpose:To compare three‐dimensional conformal radiotherapy (3D CRT) and volumetric‐modulated arc therapy (VMAT) in lung stereotactic body radiation therapy (SBRT)Methods:A retrospective study of clinically treated lung SBRT cases treated between 2010 and 2015 at our hospital was performed. All treatment modalities were included in this evaluation (VMAT, 3D CRT, static IMRT, and dynamic conformal arc therapy). However, the majority of treatment modalities were either VMAT or 3D CRT. Treatment times of patients and dosimetric plan quality metrics were compared. Treatment times were calculated based on the time the therapist opened and closed the patient's treatment plan. This treatment time closely approximates the utilization time of the treatment room. The dosimetric plan quality metrics evaluated include ICRU conformity index, the volume of 105% prescribed dose outside PTV, the ratio of volume of 50% prescribed dose to the volume of PTV, the percentage of maximum dose at 2 cm away from PTV to the prescribed dose, and the V20 (percentage of lung volume receiving 20 Gy or more).Results:Treatment time comparisons show that on average VMAT has shorter treatment times than 3D CRT. Dose conformity, defined by the ICRU conformity index, and high dose spillage, defined by the volume of 105% dose outside the PTV, is reduced when using VMAT compared to 3D CRT. V20 and intermediate dose spillage/fall‐off metrics of VMAT and 3D are not significantly different.Conclusion:Clinically treated lung SBRT cases indicate VMAT is superior to 3D with regard to shorter treatment times, plan dose conformity, and plan high dose spillage.
SU‐F‐T‐649: Dosimetric Evaluation of Non‐Coplanar Arc Therapy Using a Novel Rotating Gamma Ray System
Authors: Eldib A , Chibani O , Mora G , Jin L , Fan J , Li J , Veltchev I , Ma C 
Published: July 2016

Purpose:Stereotactic intra and extra‐cranial body radiation therapy has evolved with advances in treatment accuracy, effective radiation dose, and parameters necessary to maximize machine capabilities. Novel gamma systems with a ring type gantry were developed having the ability to perform oblique arcs. The aim of this study is to explore the dosimetric advantages of this new system.Methods:The rotating Gamma system is named CybeRay (Cyber Medical Corp., Xian, China). It has a treatment head of 16 cobalt‐60 sources focused to the isocenter, which can rotate 360° on the ring gantry and swing 35° in the superior direction. Treatment plans were generated utilizing our in‐house Monte Carlo treatment planning system. A cylindrical phantom was modeled with 2mm voxel size. Dose inside the cylindrical phantom was calculated for coplanar and non‐coplanar arcs. Dosimetric differences between CybeRay cobalt beams and CyberKnife 6MV beams were compared in a lung phantom and for previously treated SBRT patients.Results:The full width at half maxima of cross profiles in the S‐I direction for the coplanar setup matched the cone sizes, while for the non‐coplanar setup, FWHM was larger by 2mm for a 10mm cone and about 5mm for larger cones. In the coronal and sagittal view, coplanar beams showed elliptical shaped isodose lines, while non‐coplanar beams showed circular isodose lines. Thus proper selection of the oblique angle and cone size can aid optimal dose matching to the target volume. Comparing a single 5mm cone from CybeRay to that from CyberKnife showed similar penumbra in a lung phantom but CybeRay had significant lower doses beyond lung tissues. Comparable treatment plans were obtained with CybeRay as that from CyberKnife.ConclusionThe noncoplanar multiple source arrangement of CybeRay will be of great clinical benefits for stereotactic intra and extra‐cranial radiation therapy.
SU‐F‐T‐650: The Comparison of Robotic Partial Breast Stereotactic Irradiation Using MLC Vs. Iris Cone
Authors: Ding C , Timmerman R , Jiang S , Rahimi A 
Published: July 2016

Purpose:To evaluate the dosimetric impact on treatment planning for partial breast stereotactic irradiation using Cyberknife with MLC versus Iris Cone.Methods:Ten patients whom underwent lumpectomy for DCIS or stage I invasive non‐lobular epithelial breast cancer were included in this study. All patients were previously treated on the Cyberknife using Iris cone with the prescription dose of 37.5Gy in 5 fractions covering at least 95% of PTV on our phase I SBRT 5 fraction partial breast irradiation trial. Retrospectively, treatment planning was performed and compared using the new Cyberknife M6 MLC system for each patient. Using the same contours and critical organ constraints for both MLC and Iris cone plans, the dose on target and critical organs were analyzed accordingly.Results:Dose to critical organs such as ipsilateral lung, contralateral lung, heart, skin, ipsilateral breast, and rib were analyzed, as well as conformity index and high dose spillage of the target area. In 9 of 10 patients, the MLC plans had less total ipsilateral breast volume encompassing the 50% prescription isodose (mean:22.3±8.2% MLC vs. 31.6±8.0 Iris, p=0.00014) .The MLC plans mean estimated treatment delivery time was significantly less than the Iris plans (51±3.9min vs. 56.2±9min, p=0.03) Both MLC and Iris cone plans were able to meet all dose constraints and there was no statistical difference between those dose constraints.Conclusion:Both MLC and Iris Cone can deliver conformal dose to a partial breast target and satisfy the dose constraints of critical organs. The new Cyberknife with MLC can deliver a more conformal dose in the lower dose region and spare more ipsilateral breast tissue to the 50% prescription isodose. The treatment time for partial breast SBRT plans was also reduced using MLC.Project receives research support from Accuray Inc.
SU‐F‐T‐655: Evaluation of Neutron Dose Equivalent Inside of Treatment Vault of Radiotherapy by Photoneutron Production in the Primary Barriers
Authors: Choi C , Kim J , Park S , Park J 
Published: July 2016

Purpose:Photon beams with energy higher than 10 MV interact with metal material in the primary barriers, where lead or steel have been widely used, neutrons can be generated. Monte Carlo simulations were performed to simulate the production of photoneutrons and the neutron shielding effect.Methods:For two photon beam energies, 15 MV and 18 MV, we simulated to strike metal sheets (steel and lead), and the ambient dose equivalents were calculated at the isocenter (in the patient plane) while delivering 1 Gy to the patient. For these cases, the thickness of the neutron shielding materials (Borated polyethylene (BPE) and concrete) were simulated to reduce the patient exposure by neutron doses.Results:When 18 MV photons interact with the metal sheets in the primary barrier, the evaluated neutron doses at the isocenter inside the treatment vault were 48.7 µSv and 7.3 µSv for lead and steel, respectively. In case of 15 MV photons, the calculated neutron doses were 18.6 µSv and 0.6 µSv for lead and steel, respectively. The neutron dose delivered to the patient can be reduced to negligible levels by including a 10 cm thick sheet of BPE or 22 cm thick sheet of concrete.Conclusion:When bunker shielding is designed with a primary barrier including a metal sheet inside the wall for a high energy machine, proper neutron shielding should be constructed to avoid undesirable extra dose.
SU‐F‐T‐657: In‐Room Neutron Dose From High Energy Photon Beams
Authors: Christ D , Ding G 
Published: July 2016

Purpose:To estimate neutron dose inside the treatment room from photodisintegration events in high energy photon beams using Monte Carlo simulations and experimental measurements.Methods:The Monte Carlo code MCNP6 was used for the simulations. An Eberline ESP‐1 Smart Portable Neutron Detector was used to measure neutron dose. A water phantom was centered at isocenter on the treatment couch, and the detector was placed near the phantom. A Varian 2100EX linear accelerator delivered an 18MV open field photon beam to the phantom at 400MU/min, and a camera captured the detector readings. The experimental setup was modeled in the Monte Carlo simulation. The source was modeled for two extreme cases: a) hemispherical photon source emitting from the target and b) cone source with an angle of the primary collimator cone. The model includes the target, primary collimator, flattening filter, secondary collimators, water phantom, detector and concrete walls. Energy deposition tallies were measured for neutrons in the detector and for photons at the center of the phantom.Results:For an 18MV beam with an open 10cm by 10cm field and the gantry at 180°, the Monte Carlo simulations predict the neutron dose in the detector to be 0.11% of the photon dose in the water phantom for case a) and 0.01% for case b). The measured neutron dose is 0.04% of the photon dose. Considering the range of neutron dose predicted by Monte Carlo simulations, the calculated results are in good agreement with measurements.Conclusion:We calculated in‐room neutron dose by using Monte Carlo techniques, and the predicted neutron dose is confirmed by experimental measurements. If we remodel the source as an electron beam hitting the target for a more accurate representation of the bremsstrahlung fluence, it is feasible that the Monte Carlo simulations can be used to help in shielding designs.
SU‐F‐T‐672: A Novel Kernel‐Based Dose Engine for KeV Photon Beams
Authors: Reinhart M , Fast M F , Nill S , Oelfke U 
Published: July 2016

Purpose:Mimicking state‐of‐the‐art patient radiotherapy with high precision irradiators for small animals allows advanced dose‐effect studies and radiobiological investigations. One example is the implementation of pre‐clinical IMRT‐like irradiations, which requires the development of inverse planning for keV photon beams. As a first step, we present a novel kernel‐based dose calculation engine for keV x‐rays with explicit consideration of energy and material dependencies.Methods:We follow a superposition‐convolution approach adapted to keV x‐rays, based on previously published work on micro‐beam therapy. In small animal radiotherapy, we assume local energy deposition at the photon interaction point, since the electron ranges in tissue are of the same order of magnitude as the voxel size. This allows us to use photon‐only kernel sets generated by MC simulations, which are pre‐calculated for six energy windows and ten base materials. We validate our stand‐alone dose engine against Geant4 MC simulations for various beam configurations in water, slab phantoms with bone and lung inserts, and on a mouse CT with (0.275mm)3 voxels.Results:We observe good agreement for all cases. For field sizes of 1mm2 to 1cm2 in water, the depth dose curves agree within 1% (mean), with the largest deviations in the first voxel (4%) and at depths>5cm (<2.5%). The out‐of‐field doses at 1cm depth agree within 8% (mean) for all but the smallest field size. In slab geometries, the mean agreement was within 3%, with maximum deviations of 8% at water‐bone interfaces. The γ‐index (1mm/1%) passing rate for a single‐field mouse irradiation is 71%.Conclusion:The presented dose engine yields an accurate representation of keV‐photon doses suitable for inverse treatment planning for IMRT. It has the potential to become a significantly faster yet sufficiently accurate alternative to full MC simulations. Further investigations will focus on energy sampling as well as calculation times.Research at ICR is also supported by Cancer Research UK under Programme C33589/A19727 and NHS funding to the NIHR Biomedical Research Centre at RMH and ICR. MFF is supported by Cancer Research UK under Programme C33589/A19908.
SU‐G‐BRA‐04: Simulation of Errors in Maximal Intensity Projection (MIP)‐Based Lung Tumor Internal Target Volumes (ITV) Using Real‐Time 2D MRI and Deformable Image Registration Based Lung Tumor Tracking
Authors: Thomas D , Kishan A , Santhanam A , Min Y , O'Connell D , Lamb J , Cao M , Agazaryan N , Yang Y , Lee P , Low D 
Published: July 2016

Purpose:To evaluate the effect of inter‐ and intra‐fractional tumor motion on the error in four‐dimensional computed tomography (4DCT) maximal intensity projection (MIP)–based lung tumor internal target volumes (ITV), using deformable image registration of real‐time 2D‐sagital cine‐mode MRI acquired during lung SBRT treatments.Methods:Five lung tumor patients underwent free breathing SBRT treatment on the ViewRay, with dose prescribed to PTV (4DCT MIP‐based ITV+3–6mm margin). Sagittal slice cine‐MR images (3.5×3.5mm pixels) were acquired through the center of the tumor at 4 frames per second throughout the treatments (3–4 fractions of 21–32 minutes duration). Tumor GTVs were contoured on the first frame of the cine and tracked throughout the treatment using off‐line optical‐flow based deformable registration implemented on a GPU cluster. Pseudo‐4DCT MIP‐based ITVs were generated from MIPs of the deformed GTV contours limited to short segments of image data. All possible pseudo‐4DCT MIP‐based ITV volumes were generated with 1s resolution and compared to the ITV volume of the entire treatment course. Varying pseudo‐4DCT durations from 10‐50s were analyzed.Results:Tumors were covered in their entirety by PTV in the patients analysed here. However, pseudo‐4DCT based ITV volumes were observed that were as small as 29% of the entire treatment‐ITV, depending on breathing irregularity and the duration of pseudo‐4DCT. With an increase in duration of pseudo‐4DCT from 10–50s the minimum volume acquired from 95% of all pseudo‐4DCTs increased from 62%–81% of the treatment ITV.Conclusion:A 4DCT MIP‐based ITV offers a ‘snap‐shot’ of breathing motion for the brief period of time the tumor is imaged on a specific day. Real time MRI over prolonged periods of time and over multiple treatment fractions shows that the accuracy of this snap‐shot varies according to inter‐ and intra‐fractional tumor motion. Further work is required to investigate the dosimetric effect of these results.
SU‐G‐BRA‐05: Application of a Feature‐Based Tracking Algorithm to KV X‐Ray Fluoroscopic Images Toward Marker‐Less Real‐Time Tumor Tracking
Authors: Nakamura M , Nakao M , Matsuo Y , Mukumoto N , Iizuka Y , Yokota K , Mizowaki T , Hiraoka M 
Published: July 2016

Purpose:To detect target position on kV X‐ray fluoroscopic images using a feature‐based tracking algorithm, Accelerated‐KAZE (AKAZE), for markerless real‐time tumor tracking (RTTT).Methods:Twelve lung cancer patients treated with RTTT on the Vero4DRT (Mitsubishi Heavy Industries, Japan, and Brainlab AG, Feldkirchen, Germany) were enrolled in this study. Respiratory tumor movement was greater than 10 mm. Three to five fiducial markers were implanted around the lung tumor transbronchially for each patient. Before beam delivery, external infrared (IR) markers and the fiducial markers were monitored for 20 to 40 s with the IR camera every 16.7 ms and with an orthogonal kV x‐ray imaging subsystem every 80 or 160 ms, respectively. Target positions derived from the fiducial markers were determined on the orthogonal kV x‐ray images, which were used as the ground truth in this study. Meanwhile, tracking positions were identified by AKAZE. Among a lot of feature points, AKAZE found high‐quality feature points through sequential cross‐check and distance‐check between two consecutive images. Then, these 2D positional data were converted to the 3D positional data by a transformation matrix with a predefined calibration parameter. Root mean square error (RMSE) was calculated to evaluate the difference between 3D tracking and target positions. A total of 393 frames was analyzed. The experiment was conducted on a personal computer with 16 GB RAM, Intel Core i7‐2600, 3.4 GHz processor.Results:Reproducibility of the target position during the same respiratory phase was 0.6 +/− 0.6 mm (range, 0.1–3.3 mm). Mean +/− SD of the RMSEs was 0.3 +/− 0.2 mm (range, 0.0–1.0 mm). Median computation time per frame was 179 msec (range, 154–247 msec).Conclusion:AKAZE successfully and quickly detected the target position on kV X‐ray fluoroscopic images. Initial results indicate that the differences between 3D tracking and target position would be clinically acceptable.