bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐10: Sliding Mode Control of a SMA Actuated Active Flexible Needle for Medical Procedures
Authors: Podder T 
Published: July 2016

Purpose:In medical interventional procedures such as brachytherapy, ablative therapies and biopsy precise steering and accurate placement of needles are very important for anatomical obstacle avoidance and accurate targeting. This study presents the efficacy of a sliding mode controller for Shape Memory Alloy (SMA) actuated flexible needle for medical procedures.Methods:Second order system dynamics of the SMA actuated active flexible needle was used for deriving the sliding mode control equations. Both proportional‐integral‐derivative (PID) and adaptive PID sliding mode control (APIDSMC) algorithms were developed and implemented. The flexible needle was attached at the end of a 6 DOF robotic system. Through LabView programming environment, the control commands were generated using the PID and APIDSMC algorithms. Experiments with artificial tissue mimicking phantom were performed to evaluate the performance of the controller. The actual needle tip position was obtained using an electromagnetic (EM) tracking sensor (Aurora, NDI, waterloo, Canada) at a sampling period of 1ms. During experiment, external disturbances were created applying force and thermal shock to investigate the robustness of the controllers.Results:The root mean square error (RMSE) values for APIDSMC and PID controllers were 0.75 mm and 0.92 mm, respectively, for sinusoidal reference input. In the presence of external disturbances, the APIDSMC controller showed much smoother and less overshooting response compared to that of the PID controller.Conclusion:Performance of the APIDSMC was superior to the PID controller. The APIDSMC was proved to be more effective controller in compensating the SMA uncertainties and external disturbances with clinically acceptable thresholds.
SU‐F‐J‐12: Dosimetrical Characteristics of a 2.5 MV Megavoltage Photon Beam
Authors: Anamalayil S , Liu H , Kim M , Zhu T 
Published: July 2016

Purpose:To evaluate the accuracy of modeling scatter factor (SF) and primary off‐axis ratio (POAR) for 2.5 MV megavoltage photon beams using an empirical model, which can be used as a dose calculation model for low energy EPID imaging.Methods:Scatter photon parameters were calculated for 2.5 MV photon beam from a Varian TrueBeam by fitting the product of depth dose, PDD, and the phantom scatter factor, Sp, for a range of square field sizes between 2 and 40 cm and depths between 0 and 30 cm. The model is then applied to off‐axis profiles measured for a slit field (3cm ×35 cm) for 5 depths: 0.6, 5, 10, and 20, 30 cm. Primary off‐axis ratio (POAR) values were determined based on the fitting to data using the empirical model.Results:The fitting to PDD*Sp has a maximum error of 14%, mostly near surface, where backscattering of photons dominate and has a standard deviation of 4.7%. The attenuation coefficient and beam‐hardening coefficient of the beam is determined to be 0.095 1/cm and 0.0038 1/cm, respectively. POAR for 2.5 MV has a peak in the center, corresponding to a beam without sufficient material to flatten the beam.Conclusion:This work illustrates a deficiency of the current empirical model to fit SF for a 2.5 MV photon beams. Most of the errors are near the surface region and an improved model that incorporate better modeling of backscattering can be developed to improve the model accuracy.
SU‐F‐J‐13: Choosing An IMRT Technique in the Treatment of Head and Neck Cancer with Daily Localization Uncertainties
Authors: Lin T , Wang L , Galloway T , Ma C 
Published: July 2016

Purpose:Head and Neck cancer treatment with IMRT/VMAT has two choices: split‐filed IMRT(SFI), in which the LAN is treated with a separate anterior field and the extended whole‐field IMRT(WFI) in which LAN is included with the IMRT/VMAT field. This study shows that under the same dose limit criteria, choosing the technique becomes a critical issue if daily localization and immobilization altered the dose distribution.Methods:Nine common head‐and‐neck cancer cases were chosen to illustrate how the daily localization and immobilization uncertainties affect to choose between SFI and WFI. Both SFI and WFI at upper target coverage were generated with VMAT. For each case, the same planning criteria were applied to the target and critical structures; therefore, similar target coverage and dose falloff can be observed in both techniques. Thirty days of kV cone beam CT(CBCT) images on each case were also delineated with contralateral and ipsilateral target as well as larynx as critical structure. About 300 CBCT images with daily delivered doses were analyzed and compared in a form of dose‐volume histograms.Results:While both plans for SFI and WFI with VMAT planning utilized and meet the criteria of D95>prescription dose and for not‐involved larynx with mean dose <35Gy and V55<10%, the daily localization and immobilization has a great contribution to the resulted dose delivery. With WFI, the better daily contralateral and ipsilateral neck target coverage can reflect a simpler or shorter localization; however, a much superior avoidance (WFI: mean dose a 42.5Gy; SFI: mean dose a 18.9Gy) of the non‐involved larynx from the SFI is preferred.Conclusion:Dosimetrically, SFI and WFI are equally well for head and Neck cancer treatment with VMAT technique; however, if considering the contribution of daily localization(CBCT) method uncertainties, SFI is better with sparing non‐involved larynx and WFI has better target coverage.
SU‐F‐J‐19: Robust Region‐Of‐Interest (ROI) for Consistent Registration On Deteriorated Surface Images
Authors: Kang H , Malin M , Chmura S , Hasan Y , Al‐Hallaq H 
Published: July 2016

Purpose:For African‐American patients receiving breast radiotherapy with a bolus, skin darkening can affect the surface visualization when using optical imaging for daily positioning and gating at deep‐inspiration breath holds (DIBH). Our goal is to identify a region‐of‐interest (ROI) that is robust against deteriorating surface image quality due to skin darkening.Methods:We study four patients whose post‐mastectomy surfaces are imaged daily with AlignRT (VisionRT, UK) for DIBH radiotherapy and whose surface image quality is degraded toward the end of treatment. To simulate the effects of skin darkening, surfaces from the first ten fractions of each patient are systematically degraded by 25–35%, 40–50% and 65–75% of the total area of the clinically used ROI_ipsilateral‐chestwall. The degraded surfaces are registered to the reference surface in six degrees‐of‐freedom. To identify a robust ROI, three additional reference ROIs — ROI_chest+abdomen, ROI_bilateral‐chest and ROI_extended‐ipsilateral‐chestwall are created and registered to the degraded surfaces. Differences in registration using these ROIs are compared to that using ROI_ipsilateral‐chestwall.Results:For three patients, the deviations in the registrations to ROI_ipsilateral‐chestwall are > 2.0, 3.1 and 7.9mm on average for 25–35%, 40–50% and 65–75% degraded surfaces, respectively. Rotational deviations reach 11.1° in pitch. For the last patient, registration is consistent to within 2.6mm even on the 65–75% degraded surfaces, possibly because the surface topography has more distinct features. For ROI_bilateral‐chest and ROI_extended‐ipsilateral‐chest registrations deviate in a similar pattern. However, registration on ROI_chest+abdomen is robust to deteriorating image qualities to within 4.2mm for all four patients.Conclusion:Registration deviations using ROI_ipsilateral‐chestwall can reach 9.8mm on the 40–50% degraded surfaces. Caution is required when using AlignRT for patients experiencing skin darkening since the accuracy of AlignRT registration deteriorates. To avoid this inaccuracy, we recommend use of ROI_chest+abdomen, on which registration is consistent within 4.2mm even for highly degraded surfaces.
SU‐F‐J‐20: Commissioning and Acceptance Testing of the C‐Rad CatalystHD Surface Imaging System
Authors: Stanley D , Rasmussen K , Kirby N , Papanikolaou N , Gutierrez A 
Published: July 2016

Introduction:With the increasing use of surface‐based, nonionizing image‐guided radiotherapy (IGRT) systems, a comprehensive set of clinical acceptance and commissioning procedures are needed to ensure correct functionality and proper clinical integration. Although TG‐147 provides a specific set of parameters, measurement methodologies have yet to be described. The aim of this study was to provide a comprehensive overview of the commissioning and acceptance analysis performed for the C‐Rad CatalystHD imaging system.Methods and Materials:Methodology for the commissioning and acceptance of the C‐Rad CatalystHD imaging system was developed using commercially available clinical equipment. Following TG‐147 guidelines, the following tests were performed: integration of peripheral equipment, system drift, static spatial reproducibility and localization accuracy, static end‐to‐end analysis, static rotational accuracy, dynamic spatial accuracy, dynamic temporal accuracy, dynamic radiation delivery and a comprehensive end‐to‐end analysis.Results:The field of view (FOV) of the CatalystHD was 105×109×83 cm3 in the lateral, longitudinal and vertical directions. For thermal equilibrium and system drift, a thermal drift of 1.0mm was noted. A 45 min warmup time is recommended if the system has been shut off an extended period of time (>24 hours) before the QA procedure to eliminate any thermal drift. Spatial reproducibility was found to be 0.05±0.03 mm using a rigid phantom. For the static localization accuracy, system agreement with couch shifts was within 0.1±0.1 mm and positioning agreement with kV‐CBCT was 0.16±0.10 mm. For static rotational accuracy, system agreement with a high precision rotational stage (0.01 deg precision) was within 0.10±0.07 deg. Dynamic spatial and temporal localization accuracy was found to be within 0.2±0.1 mm.Conclusion:A comprehensive commissioning and acceptance study was performed using commercially available phantoms and in‐house methodologies to provide a performance evaluation of the CatalystHD imaging system.
SU‐F‐J‐21: Clinical Evaluation of Surface Scanning Systems in Different Treatment Locations
Authors: Moser T , Stefanowicz S , Rhein B , Oetzel D , Adeberg S , Koenig L , Wolf R , Rieken S , Karger C 
Published: July 2016

Purpose:To reduce imaging dose in fractionated IGRT, the ability of optical surface imaging systems (OSIS) to detect setup errors was tested. Therefore, clinical studies to evaluate for different treatment locations setup corrections derived by OSIS in comparison with x‐ray image guidance in fractionated radiation therapy was performed.Methods:The setup correction accuracy of an OSIS system (AlignRT, VisionRT, London, UK) will be analysed for the 4 tumour locations Pelvis, Upper Abdomen, Thorax and Breast, 20 patients for each location in comparison to a different system (Sentinel, C‐RAD, SE). For each patient, the setup corrections of the cone‐beam computed tomography (CBCT) of an Elekta Versa HD linear accelerator (Elekta, Crawley, UK) is considered as gold‐standard and then compared with those of the OSIS for the first ten fractions retrospectively. There were no clinical decisions made based on the surrogate system. For the OSIS, the reference surface is highly important as it represents the actual ground truth. It can be obtained either with the system itself or the surface structure delineated in the planning CT can be imported via DICOM interface. In this paper, the first results for the treatment region thorax are presented. The reference image modalities were compared.Results:Table 1 displays the difference between the setup corrections obtained with OSIS and CBCT in lateral (LAT), longitudinal (LNG) and vertical (VRT) direction for the DICOM reference image. While the median deviations are within a few millimeters, some outliers showed large deviations. Generally, the mean deviation as well as the spread was smallest in lateral and largest in vertical direction.Conclusion:Although the system allows fast, simple and non‐invasive determination of setup corrections, it should be evaluated treatment region dependant. Therefore, the study is ongoing. The application of OSIS may help to reduce the imaging dose for the patient.We gratefully acknowledge the support by our colleagues from the Radiological University Clinic Heidelberg, where the study was performed. This work was funded by the Federal Ministry of Education and Research (BMBF) Germany, grant number 01IB13001B.
SU‐F‐J‐24: Setup Uncertainty and Margin of the ExacTrac 6D Image Guide System for Patients with Brain Tumors
Authors: Kim S , Oh S , Yea J , Park J 
Published: July 2016

Purpose:This study evaluated the setup uncertainties for brain sites when using BrainLAB's ExacTrac X‐ray 6D system for daily pretreatment to determine the optimal planning target volume (PTV) margin.Methods:Between August 2012 and April 2015, 28 patients with brain tumors were treated by daily image‐guided radiotherapy using the BrainLAB ExacTrac 6D image guidance system of the Novalis‐Tx linear accelerator. DUONTM (Orfit Industries, Wijnegem, Belgium) masks were used to fix the head. The radiotherapy was fractionated into 27–33 treatments. In total, 844 image verifications were performed for 28 patients and used for the analysis. The setup corrections along with the systematic and random errors were analyzed for six degrees of freedom in the translational (lateral, longitudinal, and vertical) and rotational (pitch, roll, and yaw) dimensions.Results:Optimal PTV margins were calculated based on van Herk et al.'s [margin recipe = 2.5∑ + 0.7σ − 3 mm] and Stroom et al.'s [margin recipe = 2∑ + 0.7σ] formulas. The systematic errors (∑) were 0.72, 1.57, and 0.97 mm in the lateral, longitudinal, and vertical translational dimensions, respectively, and 0.72°, 0.87°, and 0.83° in the pitch, roll, and yaw rotational dimensions, respectively. The random errors (σ) were 0.31, 0.46, and 0.54 mm in the lateral, longitudinal, and vertical rotational dimensions, respectively, and 0.28°, 0.24°, and 0.31° in the pitch, roll, and yaw rotational dimensions, respectively. According to van Herk et al.'s and Stroom et al.'s recipes, the recommended lateral PTV margins were 0.97 and 1.66 mm, respectively; the longitudinal margins were 1.26 and 3.47 mm, respectively; and the vertical margins were 0.21 and 2.31 mm, respectively.Conclusion:Therefore, daily setup verifications using the BrainLAB ExacTrac 6D image guide system are very useful for evaluating the setup uncertainties and determining the setup margin.∑σ
SU‐F‐J‐26: Performance of 2.5MV Portal Imaging in Comparison with KV X‐Ray and 6MV and Flattening‐Filter‐Free 6MV Portal Imaging
Authors: Duan J , Yang Y , Faught A , Subashi E , Wu Q , Yin F 
Published: July 2016

Purpose:To assess image quality and imaging dose of 2.5MV electronic portal imaging in comparison to kV imaging and 6MV and Flattening‐Filter‐Free 6MV (6MVFFF) portal imaging using a DMI imager.Methods:Quantitative assessment of image quality was performed with Leeds and Las Vegas test phantoms in conjunction with qualitative evaluation of clinical patient images for kV imaging and 2.5MV, 6MV and 6MVFFF portal imaging. High and low contrast resolutions were evaluated and imaging doses were measured using these x‐rays. Phantom test was performed both in air and in solid water. Clinical patient portal images were also reviewed and qualitatively assessed for these three imaging MV energies.Results:Among the 28 objects in Las Vegas phantom, 16, 17 and 26 of them were resolved using Low Dose technique and 18, 22 and 26 were resolved using High Quality technique with 6MV, 6MVFFF and 2.5MV, respectively. The number of Leeds low contrast objects resolved by 6MV, 6MFFFF and 2.5MV was 6, 15 and 18 with Low Dose technique and 14, 17 and 18 with High Quality technique, respectively. When the test phantoms were embedded in 20cm thick solid water, the results were noticeably affected, but the performance of 2.5MV was still substantially better than 6MV and 6MVFFF. Imaging dose with 2.5MV measured at 10 cm depth was about half of that with 6MV or 6MVFFF. Clinical patient portal images were reviewed and qualitatively assessed for different sites including brain, head‐and‐neck, chest and pelvis. 2.5MV imaging provided more details and substantially higher contrast.Conclusion:While portal imaging with 6MVFFF provides noticeably better image quality than that with 6MV, the performance of 2.5MV portal imaging is substantially better than both 6MV and 6MVFFF in terms of high and low contrast resolutions as well as lower imaging dose. 2.5MV imaging provides near kV imaging quality.
SU‐F‐J‐27: Segmentation of Prostate CBCT Images with Implanted Calypso Transponders Using Double Haar Wavelet Transform
Authors: Liu Y , Saleh Z , Song Y , Obcemea C , Chan M , Li X , Happersett L , Shi C , Qian X , Tang X 
Published: July 2016

Purpose:Segmentation of prostate CBCT images is an essential step towards real‐time adaptive radiotherapy. It is challenging For Calypso patients, as more artifacts are generated by the beacon transponders. We herein propose a novel wavelet‐based segmentation algorithm for rectum, bladder, and prostate of CBCT images with implanted Calypso transponders.Methods:Five hypofractionated prostate patients with daily CBCT were studied. Each patient had 3 Calypso transponder beacons implanted, and the patients were setup and treated with Calypso tracking system. Two sets of CBCT images from each patient were studied. The structures (i.e. rectum, bladder, and prostate) were contoured by a trained expert, and these served as ground truth. For a given CBCT, the moving window‐based Double Haar transformation is applied first to obtain the wavelet coefficients. Based on a user defined point in the object of interest, a cluster algorithm based adaptive thresholding is applied to the low frequency components of the wavelet coefficients, and a Lee filter theory based adaptive thresholding is applied to the high frequency components. For the next step, the wavelet reconstruction is applied to the thresholded wavelet coefficients. A binary/segmented image of the object of interest is therefore obtained. DICE, sensitivity, inclusiveness and ΔV were used to evaluate the segmentation result.Results:Considering all patients, the bladder has the DICE, sensitivity, inclusiveness, and ΔV ranges of [0.81–0.95], [0.76–0.99], [0.83–0.94], [0.02–0.21]. For prostate, the ranges are [0.77–0.93], [0.84–0.97], [0.68–0.92], [0.1–0.46]. For rectum, the ranges are [0.72–0.93], [0.57–0.99], [0.73–0.98], [0.03–0.42].Conclusion:The proposed algorithm appeared effective segmenting prostate CBCT images with the present of the Calypso artifacts. However, it is not robust in two scenarios: 1) rectum with significant amount of gas; 2) prostate with very low contrast. Model based algorithm might improve the segmentation in these two scenarios.
SU‐F‐J‐29: Dosimetric Effect of Image Registration ROI Size and Focus in Automated CBCT Registration for Spine SBRT
Authors: Magnelli A , Smith A , Chao S , Suh J , Xia P 
Published: July 2016

Purpose:Spinal stereotactic body radiotherapy (SBRT) involves highly conformal dose distributions and steep dose gradients due to the proximity of the spinal cord to the treatment volume. To achieve the planning goals while limiting the spinal cord dose, patients are setup using kV cone‐beam CT (kV‐CBCT) with 6 degree corrections. The kV‐CBCT registration with the reference CT is dependent on a user selected region of interest (ROI). The objective of this work is to determine the dosimetric impact of ROI selection.Methods:Twenty patients were selected for this study. For each patient, the kV‐CBCT was registered to the reference CT using three ROIs including: 1) the external body, 2) a large anatomic region, and 3) a small region focused in the target volume. Following each registration, the aligned CBCTs and contours were input to the treatment planning system for dose evaluation. The minimum dose, dose to 99% and 90% of the tumor volume (D99%, D90%), dose to 0.03cc and the dose to 10% of the spinal cord subvolume (V10Gy) were compared to the planned values.Results:The average deviations in the tumor minimum dose were 2.68%±1.7%, 4.6%±4.0%, 14.82%±9.9% for small, large and the external ROIs, respectively. The average deviations in tumor D99% were 1.15%±0.7%, 3.18%±1.7%, 10.0%±6.6%, respectively. The average deviations in tumor D90% were 1.00%±0.96%, 1.14%±1.05%, 3.19%±4.77% respectively. The average deviations in the maximum dose to the spinal cord were 2.80%±2.56%, 7.58%±8.28%, 13.35%±13.14%, respectively. The average deviation in V10Gy to the spinal cord were 1.69%±0.88%, 1.98%±2.79%, 2.71%±5.63%.Conclusion:When using automated registration algorithms for CBCT‐Reference alignment, a small target‐focused ROI results in the least dosimetric deviation from the plan. It is recommended to focus narrowly on the target volume to keep the spinal cord dose below tolerance.
SU‐F‐J‐32: Do We Need KV Imaging During CBCT Based Patient Set‐Up for Lung Radiation Therapy?
Authors: Gopal A , Zhou J , Prado K , D'souza W , Yi B 
Published: July 2016

Purpose:To evaluate the role of 2D kilovoltage (kV) imaging to complement cone beam CT (CBCT) imaging in a shift threshold based image guided radiation therapy (IGRT) strategy for conventional lung radiotherapy.Methods:A retrospective study was conducted by analyzing IGRT couch shift trends for 15 patients that received lung radiation therapy to evaluate the benefit of performing orthogonal kV imaging prior to CBCT imaging. Herein, a shift threshold based IGRT protocol was applied, which would mandate additional CBCT verification if the applied patient shifts exceeded 3 mm to avoid intraobserver variability in CBCT registration and to confirm table shifts. For each patient, two IGRT strategies: kV + CBCT and CBCT alone, were compared and the recorded patient shifts were categorized into whether additional CBCT acquisition would have been mandated or not. The effectiveness of either strategy was gauged by the likelihood of needing additional CBCT imaging for accurate patient set‐up.Results:The use of CBCT alone was 6 times more likely to require an additional CBCT than KV+CBCT, for a 3 mm shift threshold (88% vs 14%). The likelihood of additional CBCT verification generally increased with lower shift thresholds, and was significantly lower when kV+CBCT was used (7% with 5 mm shift threshold, 36% with 2 mm threshold), than with CBCT alone (61% with 5 mm shift threshold, 97% with 2 mm threshold). With CBCT alone, treatment time increased by 2.2 min and dose increased by 1.9 cGy per fraction on average due to additional CBCT with a 3mm shift threshold.Conclusion:The benefit of kV imaging to screen for gross misalignments led to more accurate CBCT based patient localization compared with using CBCT alone. The subsequently reduced need for additional CBCT verification will minimize treatment time and result in less overall patient imaging dose.