bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐23: An Accurate Algorithm to Match Imperfectly Matched Images for Lung Tumor Detection Without Markers
Authors: Rozario T , Bereg S , Chiu T , Liu H , Kearney V , Jiang L , Mao W 
Published: July 2014

Purpose:In order to locate lung tumors on projection images without internal markers, digitally reconstructed radiograph (DRR) is created and compared with projection images. Since lung tumors always move and their locations change on projection images while they are static on DRRs, a special DRR (background DRR) is generated based on modified anatomy from which lung tumors are removed. In addition, global discrepancies exist between DRRs and projections due to their different image originations, scattering, and noises. This adversely affects comparison accuracy. A simple but efficient comparison algorithm is reported.Methods:This method divides global images into a matrix of small tiles and similarities will be evaluated by calculating normalized cross correlation (NCC) between corresponding tiles on projections and DRRs. The tile configuration (tile locations) will be automatically optimized to keep the tumor within a single tile which has bad matching with the corresponding DRR tile. A pixel based linear transformation will be determined by linear interpolations of tile transformation results obtained during tile matching. The DRR will be transformed to the projection image level and subtracted from it. The resulting subtracted image now contains only the tumor. A DRR of the tumor is registered to the subtracted image to locate the tumor.Results:This method has been successfully applied to kV fluoro images (about 1000 images) acquired on a Vero (Brainlab) for dynamic tumor tracking on phantom studies. Radiation opaque markers are implanted and used as ground truth for tumor positions. Although, other organs and bony structures introduce strong signals superimposed on tumors at some angles, this method accurately locates tumors on every projection over 12 gantry angles. The maximum error is less than 2.6 mm while the total average error is 1.0 mm.Conclusion:This algorithm is capable of detecting tumor without markers despite strong background signals.
SU‐E‐J‐24: An Evaluation of the Stability of Image Quality Parameters of Varian On‐Board Imaging (OBI) and EPID Imaging Systems
Authors: Stanley D , Papanikolaou N , Gutierrez A 
Published: July 2014

Purpose:Quality assurance of the image quality for image guided localization systems is crucial to ensure accurate visualization and localization of target volumes. In this study, the long term stability of selected image parameters was assessed and evaluated for CBCT mode, planar radiographic kV mode and the radiographic MV EPID mode.Methods:The CATPHAN, QckV‐1 and QC‐3 phantoms were used to evaluate the image quality parameters. The planar radiographic images were analyzed in PIPSpro™ with spatial resolution (f30, f40, f50) being recorded. For OBI CBCT, High quality head Full‐Fan acquisition and Pelvis Half‐Fan acquisition modes were evaluated for Uniformity, Noise, Spatial Resolution, HU constancy and geometric distortion. Dose and kVp for the OBI were recorded using the Unfors RaySafe Xi system with the R/F High Detector for planar kV and the CT detector for CBCT. Dose for the MV EPID was recorded using a PTW975 Semiflex Ion Chamber, PTW Unidos electrometer and SolidWater™.Results:For each metric, values were normalized to the mean and the standard deviations were recorded. For the planar radiographic spatial resolution the f30, f40, f50 were 0.015, 0.008, 0.004 and 0.006, 0.009, 0.018 for the kV and MV, respectively. The standard deviation of the dose for kV was 0.010 and 0.005 for the MV. The standard deviations for Full and half fan were averaged together and the following standard deviations for each metric were recorded: 0.075(uniformity), 0.071(noise), 0.006(AP‐Geometric Distortion), 0.005(LAT‐Geometric Distortion), 0.058(mean slice thickness), 0.098(f30),0.101(f40),0.124(f50), 0.031(Lung/PMP‐HU constancy), 0.063(Water/poly‐HU constancy), 0.015(Bone/Derlin‐HU constancy),0.006(Dose‐Center), 0.004(Dose‐Periphery). Using these, tolerances can be reported as a warning and action threshold of 1σ and 2σ.Conclusion:A study was performed to assess the stability of the basic image quality parameters recommended by TG‐142 for the Varian OBI and EPID Imaging systems. The two systems show consistent imaging and dosimetric properties over the evaluated time frame.
SU‐E‐J‐27: Appropriateness Criteria for Deformable Image Registration and Dose Propagation
Authors: Papanikolaou P , Tuohy Rachel , Mavroidis P , Eng T , Gutierrez A , Stathakis S 
Published: July 2014

Purpose:Several commercial software packages have been recently released that allow the user to apply deformable registration algorithms (DRA) for image fusion and dose propagation. Although the idea of anatomically tracking the daily patient dose in the context of adaptive radiotherapy or merely adding the dose from prior treatment to the current one is very intuitive, the accuracy and applicability of such algorithms needs to be investigated as it remains somewhat subjective. In our study, we used true anatomical data where we introduced changes in the density, volume and location of segmented structures to test the DRA for its sensitivity and accuracy.Methods:The CT scan of a prostate patient was selected for this study. The CT images were first segmented to define structure such as the PTV, bladder, rectum, intestines and pelvic bone anatomy. To perform our study, we introduced anatomical changes in the reference patient image set in three different ways: (i) we kept the segmented volumes constant and changed the density of rectum and bladder in increments of 5% (ii) we changed the volume of rectum and bladder in increments of 5% and (iii) we kept the segmented volumes constant but changed their location by moving their COM in increments of 3mm. Using the Velocity software, we evaluated the accuracy of the DRA for each incremental change in all three scenarios.Results:The DRA performs reasonably well when the differential density difference against the background is more than 5%. For the volume change study, the DRA results became unreliable for relative volume changes greater than 10%. Finally for the location study, the DRA performance was acceptable for shifts below 9mm.Conclusion:Site specific and patient specific QA for DRA is an important step to evaluate such algorithms prior to their use for dose propagation.
SU‐E‐J‐30: Benchmark Image‐Based TCP Calculation for Evaluation of PTV Margins for Lung SBRT Patients
Authors: Li M , Chetty I , Zhong H 
Published: July 2014

Purpose:Tumor control probability (TCP) calculated with accumulated radiation doses may help design appropriate treatment margins. Image registration errors, however, may compromise the calculated TCP. The purpose of this study is to develop benchmark CT images to quantify registration‐induced errors in the accumulated doses and their corresponding TCP.Methods:4DCT images were registered from end‐inhale (EI) to end‐exhale (EE) using a “demons” algorithm. The demons DVFs were corrected by an FEM model to get realistic deformation fields. The FEM DVFs were used to warp the EI images to create the FEM‐simulated images. The two images combined with the FEM DVF formed a benchmark model. Maximum intensity projection (MIP) images, created from the EI and simulated images, were used to develop IMRT plans. Two plans with 3 and 5 mm margins were developed for each patient. With these plans, radiation doses were recalculated on the simulated images and warped back to the EI images using the FEM DVFs to get the accumulated doses. The Elastix software was used to register the FEM‐simulated images to the EI images. TCPs calculated with the Elastix‐accumulated doses were compared with those generated by the FEM to get the TCP error of the Elastix registrations.Results:For six lung patients, the mean Elastix registration error ranged from 0.93 to 1.98 mm. Their relative dose errors in PTV were between 0.28% and 6.8% for 3mm margin plans, and between 0.29% and 6.3% for 5mm‐margin plans. As the PTV margin reduced from 5 to 3 mm, the mean TCP error of the Elastix‐reconstructed doses increased from 2.0% to 2.9%, and the mean NTCP errors decreased from 1.2% to 1.1%.Conclusion:Patient‐specific benchmark images can be used to evaluate the impact of registration errors on the computed TCPs, and may help select appropriate PTV margins for lung SBRT patients.
SU‐E‐J‐43: Deformed Planning CT as An Electron Density Substitute for Cone‐Beam CT
Authors: Mishra K , Godley A 
Published: July 2014

Purpose:To confirm that deforming the planning CT to the daily Cone‐Beam CTs (CBCT) can provide suitable electron density for adaptive planning. We quantify the dosimetric difference between plans calculated on deformed planning CTs (DPCT) and daily CT‐on‐rails images (CTOR). CTOR is used as a test of the method as CTOR already contains accurate electron density to compare against.Methods:Five prostate only IMRT patients, each with five CTOR images, were selected and re‐planned on Panther (Prowess Inc.) with a uniform 5 mm PTV expansion, prescribed 78 Gy. The planning CT was deformed to match each CTOR using ABAS (Elekta Inc.). Contours were drawn on the CTOR, and copied to the DPCT. The original treatment plan was copied to both the CTOR and DPCT, keeping the center of the prostate as the isocenter. The plans were then calculated using the collapsed cone heterogeneous dose engine of Prowess and typical DVH planning parameters used to compare them.Results:Each DPCT was visually compared to its CTOR with no differences observed. The agreement of the copied CTOR contours with the DPCT anatomy further demonstrated the deformation accuracy. The plans calculated using CTOR and DPCT were compared. Over the 25 plan pairs, the average difference between them for prostate D100, D98 and D95 were 0.5%, 0.2%, and 0.2%; PTV D98, D95 and mean dose: 0.3%, 0.2% and 0.3%; bladder V70, V60 and mean dose: 1.1%, 0.7%, and 0.2%; and rectum mean dose: 0.3%. (D100 is the dose covering 100% of the target; V70 is the volume of the organ receiving 70 Gy).Conclusion:We observe negligible difference between the dose calculated on the DPCT and the CTOR, implying that deformed planning CTs are a suitable substitute for electron density. The method can now be applied to CBCTs.Research version of Panther provided by Prowess Inc. Research version of ABAS provided by Elekta Inc.
SU‐E‐J‐45: Design and Study of An In‐House Respiratory Gating Phantom Platform for Gated Radiotherapy
Authors: Senthilkumar S 
Published: July 2014

Purpose:The main purpose of this work was to develop an in‐house low cost respiratory motion phantom platform for testing the accuracy of the gated radiotherapy system and analyze the dosimetric difference during gated radiotherapy.Methods:An in‐house respiratory motion platform(RMP) was designed and constructed for testing the targeting accuracy of respiratory tracking system. The RMP consist of acrylic Chest Wall Platform, 2 DC motors, 4 IR sensors, speed controller circuit, 2 LED and 2 moving rods inside the RMP. The velocity of the movement can be varied from 0 to 30 cycles per minute. The platform mounted to a base using precision linear bearings. The base and platform are made of clear, 15mm thick polycarbonate plastic and the linear ball bearings are oriented to restrict the platform to a movement of approximately 50mm up and down with very little friction.Results:The targeting accuracy of the respiratory tracking system was evaluated using phantom with and without respiratory movement with varied amplitude. We have found the 5% dose difference to the PTV during the movement in comparison with stable PTV. The RMP can perform sinusoidal motion in 1D with fixed peak to peak motion of 5 to 50mm and cycle interval from 2 to 6 seconds. The RMP was designed to be able to simulate the gross anatomical anterior posterior motion attributable to respiration‐induced motion of the thoracic region.Conclusion:The unique RMP simulates breathing providing the means to create a comprehensive program for commissioning, training, quality assurance and dose verification of gated radiotherapy treatments. Create the anterior/posterior movement of a target over a 5 to 50 mm distance to replicate tumor movement. The targeting error of the respiratory tracking system is less than 1.0 mm which shows suitable for clinical treatment with highly performance.
SU‐E‐J‐47: Development of a High‐Precision, Image‐Guided Radiotherapy, Multi‐ Purpose Radiation Isocenter Quality‐Assurance Calibration and Checking System
Authors: Liu C , Yan G , Helmig R , Lebron S , Kahler D 
Published: July 2014

Purpose:To develop a system that can define the radiation isocenter and correlate this information with couch coordinates, laser alignment, optical distance indicator (ODI) settings, optical tracking system (OTS) calibrations, and mechanical isocenter walkout.Methods:Our team developed a multi‐adapter, multi‐purpose quality assurance (QA) and calibration device that uses an electronic portal imaging device (EPID) and in‐house image‐processing software to define the radiation isocenter, thereby allowing linear accelerator (Linac) components to be verified and calibrated. Motivated by the concept that each Linac component related to patient setup for image‐guided radiotherapy based on cone‐beam CT should be calibrated with respect to the radiation isocenter, we designed multiple concentric adapters of various materials and shapes to meet the needs of MV and KV radiation isocenter definition, laser alignment, and OTS calibration. The phantom's ability to accurately define the radiation isocenter was validated on 4 Elekta Linacs using a commercial ball bearing (BB) phantom as a reference. Radiation isocenter walkout and the accuracy of couch coordinates, ODI, and OTS were then quantified with the device.Results:The device was able to define the radiation isocenter within 0.3 mm. Radiation isocenter walkout was within ±1 mm at 4 cardinal angles. By switching adapters, we identified that the accuracy of the couch position digital readout, ODI, OTS, and mechanical isocenter walkout was within sub‐mm.Conclusion:This multi‐adapter, multi‐purpose isocenter phantom can be used to accurately define the radiation isocenter and represents a potential paradigm shift in Linac QA. Moreover, multiple concentric adapters allowed for sub‐mm accuracy for the other relevant components. This intuitive and user‐friendly design is currently patent pending.
SU‐E‐J‐48: Development of An Abdominal Compression Device for Respiratory Correlated Radiation Therapy
Authors: Kim T , Kang S , Kim D , Kim S , Suh T 
Published: July 2014

Purpose:The aim of this study is to develop the abdominal compression device which could control pressure level according to the abdominal respiratory motion and evaluate its feasibility.Methods:In this study, we focused on developing the abdominal compression device which could control pressure level at any point of time so the developed device is possible to use a variety of purpose (gating technique or respiratory training system) while maintaining the merit of the existing commercial device. The compression device (air pad form) was designed to be able to compress the front and side of abdomen and the pressure level of the abdomen is controlled by air flow. Pressure level of abdomen (air flow) was determined using correlation data between external abdominal motion and respiratory volume signal measured by spirometer. In order to verify the feasibility of the device, it was necessary to confirm the correlation between the abdominal respiratory motion and respiratory volume signal and cooperation with respiratory training system also checked.Results:In the previous study, we could find that the correlation coefficient ratio between diaphragm and respiratory volume signal measured by spirometer was 0.95. In this study, we confirmed the correlation between the respiratory volume signal and the external abdominal motion measured by belt‐transducer (correlation coefficient ratio was 0.92) and used the correlated respiratory volume data as an abdominal pressure level. It was possible to control the pressure level with negligible time delay and respiratory volume data based guiding waveforms could be properly inserted into the respiratory training system.Conclusion:Through this feasibility study, we confirmed the correlation between the respiratory volume signal and the external abdominal motion. Also initial assessment of the device and its compatibility with the respiratory training system were verified. Further study on application in respiratory gated therapy and respiratory training system will be investigated.This work was supported by Radiation Technology R&D program (No. 2013M2A2A7043498)and Basic Atomic Energy Research Institute (BAERI)(No. NRF‐2009‐0078390) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
SU‐E‐J‐51: Dose Response of Common Solid State Detectors in Homogeneous Transverse and Longitudinal Magnetic Fields
Authors: Reynolds M , Fallone B , Rathee S 
Published: July 2014

Purpose:Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is evaluated in varying transverse and longitudinal magnetic fields for eventual use in MR‐Linac devices.Methods:A PTW 60003 and IBA PFD detector were modeled in the Monte Carlo code PENELOPE, incorporating a magnetic field which was varied in strength and oriented both transversely and longitudinally with respect to the incident photon beam. The detectors' long axis was in turn oriented either parallel or perpendicular to the photon beam. Dose to the active volume of each detector was scored, and its ratio to dose with zero magnetic field strength (dose response) was determined. Accuracy of the simulations was evaluated by measurements using both chambers taken at low field with a small electromagnet. Simulations were also performed in a water phantom to compare to the in air results.Results:Significant dose response was found in transverse field geometries, nearing 20% at 1.5T. The response is highly dependent on relative orientations to the magnetic field and photon beam, and on detector composition. Low field measurements confirm these results. In the presence of longitudinal magnetic fields, the detectors exhibit little dose response, reaching 0.5–1% at 1.5T regardless of detector orientation. Water tank simulations compared well to the in air simulations when not at the beam periphery, where in transverse magnetic fields only, the water tank simulations differed from the in air results.Conclusion:Transverse magnetic fields can cause large deviations in dose response, and are highly position orientation dependent. Comparatively, longitudinal magnetic fields exhibit little to no dose response in each detector as a function of magnetic field strength. Water tank simulations show longitudinal fields are generally easier to work with, but each detector must be evaluated separately.
SU‐E‐J‐63: Estimating the Effects of Respiratory Motion On Dose Heterogeneity for ITV‐Based Treatments
Authors: Williams C , Lewis J 
Published: July 2014

Purpose:To quantify the relationship between the amount of dose heterogeneity in a treatment plan that uses an internal target volume (ITV) to account for respiratory motion and the true amount of heterogeneity in the dose delivered to the tumor contained within that ITV.Methods:We develop a convolution‐based framework for calculating dose delivered to a tumor moving inside an ITV according to a common sinusoid‐based breathing model including asymmetry. We model the planned ITV dose distribution as a centrally peaked analytic function approximating the profile of clinical stereotactic body radiotherapy treatments. Expressions for the minimum and maximum dose received by the tumor are derived and evaluated for a range of clinically relevant parameters. Results of the model are validated with phantom measurements using an ion chamber array.Results:An analytic expression is presented for the maximum and minimum doses received by the tumor relative to the planned ITV dose. The tumor dose heterogeneity depends solely on the ratio of tumor size to ITV size, the peak dose in the planned ITV dose distribution, and the respiratory asymmetry parameter. Under the assumptions of this model, using a typical breathing asymmetry parameter and a dose distribution with a fixed size ITV covered by the 100% line and with a 130% hotspot, the maximum dose to the tumor varies between 113%–130%, and the minimum dose varies between 100%–116% depending on the amount of tumor motion.Conclusion:This modeling exercise demonstrates the interplay between motion and dose heterogeneity. Tumors that exhibit large amounts of respiratory motion relative to their size will receive a more homogeneous dose and a larger minimum dose than would be inferred from the ITV dose distribution. This effect is not captured in current clinical treatment planning methods unless 4D dose calculation techniques are used.This work was partially supported by a Varian Medical Systems research grant
SU‐E‐J‐65: Evaluation of a Radiation‐Induced Cell Proliferation Probability Formula Using Monte Carlo Simulation
Authors: Watanabe Y , Dahlman E 
Published: July 2014

Purpose:To evaluate the analytic formula of the cell death probability after single fraction dose.Methods:Cancer cells endlessly divide, but radiation causes the cancer cells to die. Not all cells die right away after irradiation. Instead, they continue dividing for next few cell cycles before they stop dividing and die. At the end of every cell cycle, the cell decides if it undertakes the mitotic process with a certain probability, Pdiv, which is altered by the radiation. Previously, by using a simple analytic model of radiobiology experiments, we obtained a formula of Pdeath (= 1 − Pdiv). A question is if the proposed probability can reproduce the well‐known survival data of the LQ model. In this study, we evaluated the formula by doing a Monte Carlo simulation of the cell proliferation process. Starting with Ns seed cells, the cell proliferation process was simulated for N generations or until all cells die. We counted the number of living cells at the end. Assuming that the cell colony survived when more than Nc cells were still alive, the surviving fraction S was estimated. We compared the S vs. dose, or S‐D curve, with the LQ model.Results:The results indicated that our formula does not reproduce the experimentally observed S‐D curve without selecting appropriate α and α/β. With parameter optimization, there was a fair agreement between the MC result and the LQ curve of dose lower than 20Gy. However, the survival fraction of MC decreased much faster in comparison to the LQ data for doses higher than 20 Gy.Conclusion:This study showed that the previously derived probability of cell death per cell cycle is not sufficiently accurate to replicate common radiobiological experiments. The formula must be modified by considering its cell cycle dependence and some other unknown effects.