bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐167: Use of MR for Permanent Prostate Implant Preplanning
Authors: Narayana V , Yao B , McLaughlin P 
Published: July 2016

Purpose:To study the feasibility using MR imaging to improve target definition on ultrasound during permanent prostate implants and aid in source strength determination for treatment planning in the OR.Methods:Patients who receive permanent prostate implants undergo MR and CT imaging prior to the implant procedure to determine the volume of the prostate, bony restriction to the procedure, bladder extension, external sphincter length and neurovascular bundle. The volume of the prostate is generally used to order seeds for the procedure. In 10 patients, the MR was used as the preplanning study with the PTV defined as a 2 mm expansion of the MR prostate in all directions except the posterior. Various dose volume parameters for the MR prostate and the PTV were compared to the actual preplan developed and executed in the OR. In addition, there parameters were compared to the post implant dosimetry performed 3 weeks after the implant procedure.Results:The results show that the number of seeds used using MR and US (ultrasound) planning was generally with 2 seeds and the maximum difference was 7 seeds. There is no significant difference between any of the dose index parameters of V100, V150, V200, D99 and D90 parameters between MR planning, US planning and postimplant evaluation There was a significant difference between planned D99 (avg of 105%) and achieved D99 (avg 91%).Conclusion:MR imaging is an invaluable tool to improve target definition for permanent prostate implants. Use of MR images for preplanning improves the confidence with which source can be ordered for the procedure that is OR planned. Ordering a maximum of 10 seeds more than planned would be sufficient to deliver a plan in the OR using US. Moving ahead to non‐rigid registration between MR ad US images could further increase the confidence level of MR planning.
SU‐F‐J‐175: Evaluation of Metal Artifact Reduction Algorithms in Computed Tomography and Their Application to Radiation Therapy Treatment Planning
Authors: Norris H , Rangaraj D , Kim S 
Published: July 2016

Purpose:High‐Z (metal) implants in CT scans cause significant streak‐like artifacts in the reconstructed dataset. This results in both inaccurate CT Hounsfield units for the tissue as well as obscuration of the target and organs at risk (OARs) for radiation therapy planning. Herein we analyze two metal artifact reduction algorithms: GE's Smart MAR and a Metal Deletion Technique (MDT) for geometric and Hounsfield Unit (HU) accuracy.Methods:A CT‐to‐electron density phantom, with multiple inserts of various densities and a custom Cerrobend insert (Zeff=76.8), is utilized in this continuing study. The phantom is scanned without metal (baseline) and again with the metal insert. Using one set of projection data, reconstructed CT volumes are created with filtered‐back‐projection (FBP) and the MAR and the MDT algorithms. Regions‐of‐Interest (ROIs) are evaluated for each insert for HU accuracy; the metal insert's Full‐Width‐Half‐Maximum (FWHM) is used to evaluate the geometric accuracy. Streak severity is quantified with an HU error metric over the phantom volume.Results:The original FBP reconstruction has a Root‐Mean‐Square‐Error (RMSE) of 57.55 HU (STD=29.19, range=−145.8 to +79.2) compared to baseline. The MAR reconstruction has a RMSE of 20.98 HU (STD=13.92, range=−18.3 to +61.7). The MDT reconstruction has a RMSE of 10.05 HU (STD=10.5, range=−14.8 to +18.6). FWHM for baseline=162.05; FBP=161.84 (−0.13%); MAR=162.36 (+0.19%); MDT=162.99 (+0.58%). Streak severity metric for FBP=19.73 (22.659% bad pixels); MAR=8.743 (9.538% bad); MDT=4.899 (5.303% bad).Conclusion:Image quality, in terms of HU accuracy, in the presence of high‐Z metal objects in CT scans is improved by metal artifact reduction reconstruction algorithms. The MDT algorithm had the highest HU value accuracy (RMSE=10.05 HU) and best streak severity metric, but scored the worst in terms of geometric accuracy. Qualitatively, the MAR and MDT algorithms increased detectability of inserts, although there is a loss of in‐plane resolution near the metallic insert.
SU‐F‐J‐182: Investigation of Systems for Improved Accuracy in Clinical Y‐90 Percent Delivered Calculations
Authors: McBeth R , Elder D , Kesner A 
Published: July 2016

Purpose:Y‐90 Selective Internal Radiation Therapy (SIRT) is used to treat liver tumors, and by nature has variability in the percent of the intended dose that is actually delivered. To determine the quality of the administration, pre and post activity measurements are taken, and used to infer percent delivered. Vendor specifications indicate the use of an ion chamber to take these measurements. In our work, we investigated the accuracy of ion chambers, and compared them to other detector systems.Methods:We have built phantoms, phantom holders, and protocols, which allow us to measure our Y90 doses with varying apparatuses: a dose calibrator, a Geiger‐counter, an ion chamber, a crystal based thyroid probe, and a gamma camera. We have set up a system that has enabled us to gather data by measuring clinical Y90 doses as they are used in the clinic using all of the instrumental methods. Five initial doses (25 measurements/acquisitions) have been taken at the time of this abstract submission.Results:Our initial results show that measurements acquired using scintillation based detectors (thyroid probe and gamma camera) correlate better with the gold standard (i.e. the dose calibrator). Pearson correlations between the dose calibrator measurements and the GM counter, Ion chamber, thyroid probe, and gamma camera were found to be 0.88, 0.83, 0.98, 0.99, respectively. More acquisitions and analysis are planned to determine the precision of the systems, as well as optimal energy window settings.Conclusion:It is likely that current standard practice can be improved using scintillation crystal based detectors. Such systems are more sensitive, can integrate signal, and can use energy discrimination. Furthermore, phantoms can be built to integrate with probe and gamma camera systems that are robust and provide reproducibility. Future work will include expanded acquisition and analysis.
SU‐F‐J‐187: The Statistical NTCP and TCP Models in the Proton Therapy
Authors: Jang S , Frometa T , Pyakuryal A , Sio T , Piseaux R , Acosta S , Ocana K 
Published: July 2016

Purpose:The statistical models (SM) are typically used as a subjective description of a population for which there is only limited sample data, and especially in cases where the relationship between variables is known. The normal tissue complications and tumor control are frequently stochastic effects in the Radiotherapy (RT). Based on probabilistic treatments, it recently has been formulated new NTCP and TCP models for the RT. Investigating the particular requirements for their clinical use in the proton therapy (PT) is the goal of this work.Methods:The SM can be used as phenomenological or mechanistic models. The former way allows fitting real data and getting theirparameters. In the latter one, we should do efforts for determining the parameters through the acceptable estimations, measurements, and/or simulation experiments. Experimental methodologies for determination of the parameters have been developed from the fraction cells surviving the proton irradiation curves in tumor and OAR, and precise RBE models are used for calculating the variable of effective dose. As the executions of these methodologies have a high costs, so we have developed computer tools enable to perform simulation experiments as complement to limitations of the real ones.Results:The requirements for the use of the SM in the PT, such as validation and improvement of the elaborated and existent methodologies for determining the SM parameters and effective dose respectively, were determined.Conclusion:The SM realistically simulates the main processes in the PT, and for this reason these can be implemented in this therapy, which are simples, computable and they have other advantages over some current models. It has been determined some negative aspects for some currently used probabilistic models in the RT, like the LKB NTCP and others derived from logistic functions; which can be improved with the proposed methods in this study.
SU‐F‐J‐191: Dosimetric Evaluation of a Left Chestwall Patient Treated with a Compact Proton Pencil Beam Gantry Utilizing Daily Setup CBCT
Authors: Maynard M , Chen K , Rosen L , Wu H 
Published: July 2016

Purpose:To evaluate the robustness of the gradient technique for treating a multi‐isocenter left chest wall patient with a compact proton pencil beam gantry. Both CBCT and stereoscopic imaging are used to facilitate daily treatment setup.Methods:To treat the elongated chest wall planning target volume (PTV) with the compact PBS system, a 28 fraction (5040 CcGE) treatment plan was created using two fields with gradient matching technique. Daily table shifts between treatment field isocenters were obtained from the record and verify system for each treatment fraction. Copies of the initial treatment plan were made for each fraction and the field isocenter coordinates for each plan copy were adjusted to reflect daily table shifts. Doses were re‐calculated for each fraction, summed, and compared against the initial plan.Results:The table shifts (average and range) were 2.2 (−5.1–+3.9), 3.0 (−6.0–+4.0) and 3.0 (−10.1–+1.9) millimeters in the anterior‐posterior, superior‐inferior and right‐left directions, respectively. Dose difference to the PTV, heart and ipsilateral lung were evaluated. The percentage of the PTV receiving the prescription dose decreased from 94.6% to 89.1%. The D95 of the PTV increased from 99.6% to 99.9%. The maximum dose in PTV increased from 106.6% to 109.2% and V105 increased from 1.0% to 16.5%. The V20 of the ipsilateral lung increased from 18.5% to 21.0%. The mean heart dose difference was negligible.Conclusion:Observed dose differences to lung and heart tissues due to daily setup variations remained acceptably low while maintaining sufficient dose coverage to the PTV. This initial case study demonstrates the robustness of the gradient technique to treat a large target, multi‐isocenter plan with a compact proton pencil beam gantry equipped with CBCT and stereoscopic imaging modalities.
SU‐F‐J‐198: A Cross‐Platform Adaptation of An a Priori Scatter Correction Algorithm for Cone‐Beam Projections to Enable Image‐ and Dose‐Guided Proton Therapy
Authors: Andersen A , Park Y , Casares‐Magaz O , Elstroem U , Petersen J , Winey B , Muren L 
Published: July 2016

Purpose:Cone‐beam CT (CBCT) imaging may enable image‐ and dose‐guided proton therapy, but is challenged by image artefacts. The aim of this study was to demonstrate the general applicability of a previously developed a priori scatter correction algorithm to allow CBCT‐based proton dose calculations.Methods:The a priori scatter correction algorithm used a plan CT (pCT) and raw cone‐beam projections acquired with the Varian On‐Board Imager. The projections were initially corrected for bow‐tie filtering and beam hardening and subsequently reconstructed using the Feldkamp‐Davis‐Kress algorithm (rawCBCT). The rawCBCTs were intensity normalised before a rigid and deformable registration were applied on the pCTs to the rawCBCTs. The resulting images were forward projected onto the same angles as the raw CB projections. The two projections were subtracted from each other, Gaussian and median filtered, and then subtracted from the raw projections and finally reconstructed to the scatter‐corrected CBCTs. For evaluation, water equivalent path length (WEPL) maps (from anterior to posterior) were calculated on different reconstructions of three data sets (CB projections and pCT) of three parts of an Alderson phantom. Finally, single beam spot scanning proton plans (0–360 deg gantry angle in steps of 5 deg; using PyTRiP) treating a 5 cm central spherical target in the pCT were re‐calculated on scatter‐corrected CBCTs with identical targets.Results:The scatter‐corrected CBCTs resulted in sub‐mm mean WEPL differences relative to the rigid registration of the pCT for all three data sets. These differences were considerably smaller than what was achieved with the regular Varian CBCT reconstruction algorithm (1–9 mm mean WEPL differences). Target coverage in the re‐calculated plans was generally improved using the scatter‐corrected CBCTs compared to the Varian CBCT reconstruction.Conclusion:We have demonstrated the general applicability of a priori CBCT scatter correction, potentially opening for CBCT‐based image/dose‐guided proton therapy, including adaptive strategies.Research agreement with Varian Medical Systems, not connected to the present project.
SU‐F‐J‐201: Validation Study of Proton Radiography Against CT Data for Quantitative Imaging of Anatomical Changes in Head and Neck Patients
Authors: Hammi A , Weber D , Lomax A 
Published: July 2016

Purpose:In clinical pencil‐beam‐scanned (PBS) proton therapy, the advantage of the characteristic sharp dose fall‐off after the Bragg Peak (BP) becomes a disadvantage if the BP positions of a plan's constituent pencil beams are shifted, eg.due to anatomical changes. Thus, for fractionated PBS proton therapy, accurate knowledge of the water equivalent path length (WEPL) of the traversed anatomy is critical. In this work we investigate the feasibility of using 2D proton range maps (proton radiography, PR) with the active‐scanning gantry at PSI.Methods:We simulated our approach using Monte Carlo methods (MC) to simulate proton beam interactions in patients using clinical imaging data. We selected six head and neck cases having significant anatomical changes detected in per‐treatment CTs.PRs (two at 0°/90°) were generated from MC simulations of low‐dose pencil beams at 230MeV. Each beam's residual depth‐dose was propagated through the patient geometry (from CT) and detected on exiting the patient anatomy in an ideal depth‐resolved detector (eg. range telescope). Firstly, to validate the technique, proton radiographs were compared to the ground truth, which was the WEPL from ray‐tracing in the patient CT at the pencil beam location. Secondly, WEPL difference maps (per‐treatment – planning imaging timepoints) were then generated to locate the anatomical changes, both in the CT (ground truth) and in the PRs. Binomial classification was performed to evaluate the efficacy of the technique relative to CT.Results:Over the projections simulated over all six patients, 70%, 79% and 95% of the grid points agreed with the ground truth proton range to within ±0.5%, ±1%, and ±3% respectively. The sensitivity, specificity, precision and accuracy were high (mean±1σ, 83±8%, 87±13%, 95±10%, 83±7% respectively).Conclusion:We show that proton‐based radiographic images can accurately monitor patient positioning and in vivo range verification, while providing equivalent WEPL information to a CT scan, with the advantage of a much lower imaging dose.
SU‐F‐T‐54: Determination of the AAPM TG‐43 Brachytherapy Dosimetry Parameters for A New Titanium‐Encapsulated Yb‐169 Source by Monte Carlo Calculations
Authors: Reynoso F , Munro J , Cho S 
Published: July 2016

Purpose:To determine the AAPM TG‐43 brachytherapy dosimetry parameters of a new titanium‐encapsulated Yb‐169 source designed to maximize the dose enhancement during gold nanoparticle‐aided radiation therapy (GNRT).Methods:An existing Monte Carlo (MC) model of the titanium‐encapsulated Yb‐169 source, which was described in the current investigators’ published MC optimization study, was modified based on the source manufacturer's detailed specifications, resulting in an accurate model of the titanium‐encapsulated Yb‐169 source that was actually manufactured. MC calculations were then performed using the MCNP5 code system and the modified source model, in order to obtain a complete set of the AAPM TG‐43 parameters for the new Yb‐169 source.Results:The MC‐calculated dose rate constant for the new titanium‐encapsulated Yb‐169 source was 1.05 ± 0.03 cGy per hr U, indicating about 10% decrease from the values reported for the conventional stainless steel‐encapsulated Yb‐169 sources. The source anisotropy and radial dose function for the new source were found similar to those reported for the conventional Yb‐169 sources.Conclusion:In this study, the AAPM TG‐43 brachytherapy dosimetry parameters of a new titanium‐encapsulated Yb‐169 source were determined by MC calculations. The current results suggested that the use of titanium, instead of stainless steel, to encapsulate the Yb‐169 core would not lead to any major change in the dosimetric characteristics of the Yb‐169 source, while it would allow more low energy photons being transmitted through the source filter thereby leading to an increased dose enhancement during GNRT. Supported by DOD/PCRP grant W81XWH‐12‐1‐0198This investigation was supported by DOD/PCRP grant W81XWH‐12‐1‐ 0198.
SU‐F‐T‐57: Delivered Activity Accuracy of Radium 223 Dichloride Injections, When Being Administrated for Castration Resistant Prostate Cancer, Symptomatic Bone Metastases. The Impact of Residual Activity in the Spent Syringe and Dispensing Accuracy of Ra 223
Authors: Jennings G 
Published: July 2016

Purpose:To quantify the delivered activity accuracy of Radium 223 dichloride injections, when being administrated for castration – resistant prostate cancer, symptomatic bone metastases. The impact of residual activity in the spent syringe and dispensing accuracy of Ra 223.Methods:The administration is by slow intravenous injection over 1 minute followed by double flushing of the 10 mL syringe and IV with saline. Eighty (80) procedures was used to investigate variations in the activity from the amount prescribed (µCi) = 1.35 × Patient weight Kg. The Activity dispensed into a 10mL syringe using a NIST traceable Capintec CRC‐25R Chamber and a cross calibrated capintec CRC‐15R to measure activity in the syringe immediately before and after administrationResults:The patients weight range from 121Ib to 235lb and doses ranging 74.25 µCi to 144.2 µCi. The deviation of dispensed dose vs Prescribed dose average +2.1% with a range of −1.1% to +5.7%. The Dose measured before administration ranges 79.3 µCi to 154.9 µCi. Deviation from the dispensed dose was show to average +2.9% with a range of −0.8% to +7.3%. The average residual dose post injection was 2.5 µCi or 2.2% of the pre injection activity. Ranging from 0.9 µCi to 6.2 µCi, 0.7% to 5.4% respectively. Subtracting the residual activity from that measured activity before injection and comparing it to prescription dose was shown to have an average variation of +2.7% with a range of −0.8% to 7.4%.Conclusion:The case resulted in the 6.2 µCi maximum residual dose had two syringes. A small, 82.8 µCi activity, case resulted in the 7.4% maximum variation in measures less residual verses prescription dose. The average +2.1 % dispenses activity of Ra 223 over the prescription dosage was seen to counteract the average 2.2% residual dosage found to remain in the syringe
SU‐F‐T‐69: Correction Model of NIPAM Gel and Presage for Electron and Proton PDD Measurement
Authors: Lin C , Chao T , Lin C , Nien H , Tu P , Yueh C , Wu C 
Published: July 2016

Purpose:The current standard equipment for proton PDD measurement is multilayer‐parallel‐ion‐chamber. Disadvantage of multilayer‐parallel‐ion‐chamber is expensive and complexity manipulation. NIPAM‐gel and Presage are options for PDD measurement. Due to different stopping power, the result of NIPAM‐gel and Presage need to be corrected. This study aims to create a correction model for NIPAM‐gel and Presage PDD measurement.Methods:Standard water based PDD profiles of electron 6MeV, 12MeV, and proton 90MeV were acquired. Electron PDD profile after 1cm thickness of NIPAM‐gel added on the top of water was measured. Electron PDD profile with extra 1cm thickness of solid water, PTW RW3, was measured. The distance shift among standard PDD, NIPAM‐gel PDD, and solid water PDD at R50% was compared and water equivalent thickness correction factor (WET) was calculated. Similar process was repeated. WETs for electron with Presage, proton with NIPAM‐gel, and proton with Presage were calculated. PDD profiles of electron and proton with NIPAM‐gel and Presage columns were corrected with each WET. The corrected profiles were compared with standard profiles.Results:WET for electron 12MeV with NIPAM‐gel was 1.135, and 1.034 for electron 12Mev with Presage. After correction, PDD profile matched to the standard profile at the fall‐off range well. The difference at R50% was 0.26mm shallower and 0.39mm deeper. The same WET was used to correct electron 6MeV profile. Energy independence of electron WET was observed. The difference at R50% was 0.17mm deeper for NIPAM‐gel and 0.54mm deeper for Presage. WET for proton 90MeV with NIPAM‐gel was 1.056. The difference at R50% was 0.37 deeper. Quenching effect at Bragg peak was revealed. The underestimated dose percentage at Bragg peak was 27%.Conclusion:This correction model can be used to modify PDD profile with depth error within 1mm. With this correction model, NIPAM‐gel and Presage can be practical at PDD profile measurement.
SU‐F‐T‐74: Experimental Validation of Monaco Electron Monte Carlo Dose Calculation for Small Fields
Authors: Varadhan  , Way S , Arentsen L , Gerbi B 
Published: July 2016

Purpose:To verify experimentally the accuracy of Monaco (Elekta) electron Monte Carlo (eMC) algorithm to calculate small field size depth doses, monitor units and isodose distributions.Methods:Beam modeling of eMC algorithm was performed for electron energies of 6, 9, 12 15 and 18 Mev for a Elekta Infinity Linac and all available (6, 10, 14 20 and 25 cone) applicator sizes. Electron cutouts of incrementally smaller field sizes (20, 40, 60 and 80% blocked from open cone) were fabricated. Dose calculation was performed using a grid size smaller than one‐tenth of the R80–20 electron distal falloff distance and number of particle histories was set at 500,000 per cm2. Percent depth dose scans and beam profiles at dmax, d90 and d80 depths were measured for each cutout and energy with Wellhoffer (IBA) Blue Phantom2 scanning system and compared against eMC calculated doses.Results:The measured dose and output factors of incrementally reduced cutout sizes (to 3cm diameter) agreed with eMC calculated doses within ± 2.5%. The profile comparisons at dmax, d90 and d80 depths and percent depth doses at reduced field sizes agreed within 2.5% or 2mm.Conclusion:Our results indicate that the Monaco eMC algorithm can accurately predict depth doses, isodose distributions, and monitor units in homogeneous water phantom for field sizes as small as 3.0 cm diameter for energies in the 6 to 18 MeV range at 100 cm SSD. Consequently, the old rule of thumb to approximate limiting cutout size for an electron field determined by the lateral scatter equilibrium (E (MeV)/2.5 in centimeters of water) does not apply to Monaco eMC algorithm.