bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐41: A Method for Performing An In‐House Batch Assay of I‐125 Seeds Used for Prostate Implants
Authors: Muryn J , Wilkinson D 
Published: June 2015

Purpose:The purpose of this work is to evaluate a method for confirming source strength of I‐125 seeds in a bulk assay while maintaining sterility and time efficiency.Methods:The I‐125 seeds used in this study (STM 1251, Bard Brachytherapy, Inc.) were available as loose seeds or linked in 3, 4, or 5 seed configurations. A third party 10% assay (NIST traceable) is provided. Source strengths ranging from 0.395 to 0.504 U were available for this study. A stand was built out of aluminum to hold an exposure meter (Inovision (Fluke) 451P) at 25 cm above the I‐125 sources to measure the exposure rate. Three different seed configurations were measured: loose, linked, and loaded needles (Bard FastFil Seed Implant Needle). The measurements were made in an operating room, and a sterile sheet was used under the non‐sterile aluminum stand. Seeds and needles were placed in a sterile tray.Results:One hundred forty‐two loose seeds in 5 batches (0.395, 0.395, 0.409, 0.444, 0.444 U/seed) and 902 seeds in 7 batches containing various strands (0.444, 0.444,.0444, 0.466, 0.466, 0.504, 0.504 U/seed) were measured. The average exposure rate per unit activity was measured to be 0.593 mR per hr per U with a standard deviation of 0.016. The Result for loaded needles was 0.261 mR per hr per U with a standard deviation of 0.014. Once the apparatus is set up, measurements of 180 linked sources as supplied in the Bard package requires only a few minutes.Conclusion:The proposed method can confirm the activity of a batch of loose or stranded I‐125 seeds within a range of 5%.
SU‐E‐T‐42: A Method to Determine the Optimal Proton Scanned Beam Angle to Ensure Robust Treatment Planning
Authors: Kiely J Blanco , White B , Both S 
Published: June 2015

Purpose:The ability of pencil beam scanning (PBS) to deliver highly conformal dose distributions may be affected by patient‐ and physics‐related uncertainties. In clinical practice, selection of proton beam angles is determined qualitatively. This study investigates whether an optimal proton PBS beam angle could be quantitatively determined to ensure robust planning for pelvic targets.Methods:PBS beam angles were optimized based on two independent criteria; shortest and most homogeneous path from the patient surface to the distal edge of the target. The beam angle optimization criteria for gantry angles between 90°‐270° were quantified in 10° increments for each ray, calculated as the straight line distance from the surface of the skin to the CTV's distal edge. The goal was to minimize the path length of a proton PBS beam from the patient surface to the distal edge of the CTV, relative to the entry point, while minimizing HU inhomogeneity along the ray. HU homogeneity (i.e. HU variation) was quantitatively defined as the standard deviation of the average intra‐ray HU intensity distribution of the rays comprising a single beam. This method was validated relative to inter‐fraction changes on ten consecutive, locally advanced, rectal cancer patients, who underwent an average 4 verification CTs. The displacement of the 95–98% isodose lines was determined from forward calculated dose distributions on verification CTs.Results:The posterior beam (180°) had the average shortest path length, 132.7±17.2mm, and the most homogenous path, 31.9±4.3HU. The 95–98% isodose lines from all plans verified our path length to within 2.3±1.2% and HU homogeneity to within 1.2±0.5%.Conclusion:The proposed optimization algorithm determined the posterior beam dose distribution as the most robust relative to inter‐fraction variation for large pelvic targets treated with PBS and was validated via verification CT for our patient cohort. Future work will focus on further algorithm development.
SU‐E‐T‐53: A New Method for Characterizing the Stability of the Treatment Couch Isocentre
Authors: Gete E , Wilson B , Lee R 
Published: June 2015

Purpose:In this work we propose a new method for characterizing the accuracy of a linear accelerator treatment couch's isocentre. This is accomplished by a direct determination of the coordinates of the center of rotation as a function of rotation angle.Methods:A phantom consisting of five metallic BBs arranged in a plane was constructed. The phantom was positioned on the treatment couch such that the plane of the BBs was horizontal, while the central BB was aligned with the linac isocentre. With the gantry in the vertical position, the couch was rotated through its full range of rotation while EPID images were acquired every 10 degrees. For each rotation angle, the coordinates of the rotation center were calculated from the displacement of each of the four off‐center BBs identified on a pair of EPID images taken between successive rotations. The accuracy of the couch isocentre was evaluated from the distribution of the rotation center coordinates. Our results were compared with film based star‐shot measurements of the couch isocentre.Results:The measured couch center of rotation consisted of a cloud of points clustered around the linac isocentre within < 0.7 mm distance. The deviations of these points from the linac isocentre were in the range of 0.01 to 0.20 mm in the cross‐plane direction, and 0.10 to 0.61 mm in the in‐plane direction, with mean values of 0.09 mm and 0.32 mm. These results were consistent with the results obtained from the star‐shot method.Conclusion:A new method for determining the location and accuracy of the couch center of rotation has been successfully implemented. This method gives explicit values of the location and the stability of the couch isocentre, and it can be extended to gantry and collimator rotations.
SU‐E‐T‐55: A Novel Applicator for High Dose Rate Brachytherapy Treatments of Ocular Conjunctiva
Authors: Koren S , Bragilovski D , Tafo A Guemnie , Cohen G 
Published: June 2015

Purpose:To evaluate the clinical feasibility of IntraBeam intra operative kV irradiation beam device for ocular conjunctiva treatments. The Intra‐Beam system offers a 4.4 mm diameter needle applicator, that is not suitable for treatment of a large surface with limits access. We propose an adaptor that will answer to this clinical need and provide initial dosimetry.Methods:The dose distribution of the needle applicator is non uniform and hence not suitable for treatment of relatively large surfaces. We designed an adapter to the needle applicator that will filter the X‐rays and produce a conformal dose distribution over the treatment area while shielding surfaces to be spared. Dose distributions were simulated using FLUKA is a fully integrated particle physics Monte Carlo simulation package.Results:We designed a wedge applicator made of Polythermide window and stainless steel for collimating. We compare the dose distribution to that of the known needle and surface applicators.Conclusion:Initial dosimetry shows feasibility of this approach. While further refinements to the design may be warranted, the results support construction of a prototype and confirmation of the Monte Carlo dosimetry with measured data.
SU‐E‐T‐56: A Novel Approach to Computing Expected Value and Variance of Point Dose From Non‐Gated Radiotherapy Delivery
Authors: Zhou S , Zhu X , Zhang M , Zheng D , Zhang Q , Lei Y , Li S , Driewer J , Wang S , Enke C 
Published: June 2015

Purpose:Randomness in patient internal organ motion phase at the beginning of non‐gated radiotherapy delivery may introduce uncertainty to dose received by the patient. Concerns of this dose deviation from the planned one has motivated many researchers to study this phenomenon although unified theoretical framework for computing it is still missing. This study was conducted to develop such framework for analyzing the effect.Methods:Two reasonable assumptions were made: a) patient internal organ motion is stationary and periodic; b) no special arrangement is made to start a non ‐gated radiotherapy delivery at any specific phase of patient internal organ motion. A statistical ensemble was formed consisting of patient's non‐gated radiotherapy deliveries at all equally possible initial organ motion phases. To characterize the patient received dose, statistical ensemble average method is employed to derive formulae for two variables: expected value and variance of dose received by a patient internal point from a non‐gated radiotherapy delivery. Fourier Series was utilized to facilitate our analysis.Results:According to our formulae, the two variables can be computed from non‐gated radiotherapy generated dose rate time sequences at the point's corresponding locations on fixed phase 3D CT images sampled evenly in time over one patient internal organ motion period. The expected value of point dose is simply the average of the doses to the point's corresponding locations on the fixed phase CT images. The variance can be determined by time integration in terms of Fourier Series coefficients of the dose rate time sequences on the same fixed phase 3D CT images.Conclusion:Given a non‐gated radiotherapy delivery plan and patient's 4D CT study, our novel approach can predict the expected value and variance of patient radiation dose. We expect it to play a significant role in determining both quality and robustness of patient non‐gated radiotherapy plan.
SU‐E‐T‐58: A Novel Monte Carlo Photon Transport Simulation Scheme and Its Application in Cone Beam CT Projection Simulation
Authors: Xu Y , Tian Z , Zhou L , Jiang S , Jia X 
Published: June 2015

Purpose:Monte Carlo (MC) simulation is an important tool to solve radiotherapy and medical imaging problems. Low computational efficiency hinders its wide applications. Conventionally, MC is performed in a particle‐by ‐particle fashion. The lack of control on particle trajectory is a main cause of low efficiency in some applications. Take cone beam CT (CBCT) projection simulation as an example, significant amount of computations were wasted on transporting photons that do not reach the detector. To solve this problem, we propose an innovative MC simulation scheme with a path‐by‐path sampling method.Methods:Consider a photon path starting at the x‐ray source. After going through a set of interactions, it ends at the detector. In the proposed scheme, we sampled an entire photon path each time. Metropolis‐Hasting algorithm was employed to accept/reject a sampled path based on a calculated acceptance probability, in order to maintain correct relative probabilities among different paths, which are governed by photon transport physics. We developed a package gMMC on GPU with this new scheme implemented. The performance of gMMC was tested in a sample problem of CBCT projection simulation for a homogeneous object. The results were compared to those obtained using gMCDRR, a GPU‐based MC tool with the conventional particle‐by‐particle simulation scheme.Results:Calculated scattered photon signals in gMMC agreed with those from gMCDRR with a relative difference of 3%. It took 3.1 hr. for gMCDRR to simulate 7.8e11 photons and 246.5 sec for gMMC to simulate 1.4e10 paths. Under this setting, both results attained the same ∼2% statistical uncertainty. Hence, a speed‐up factor of ∼45.3 was achieved by this new path‐by‐path simulation scheme, where all the computations were spent on those photons contributing to the detector signal.Conclusion:We innovatively proposed a novel path‐by‐path simulation scheme that enabled a significant efficiency enhancement for MC particle transport simulations.
SU‐E‐T‐59: A Novel Multi‐Beam Dynamic IMRT with Fixed‐Jaw Technique for Left Breast Cancer Patients with Regional Lymph Nodes Radiotherapy
Authors: Wang J , Yang Z , Hu W 
Published: June 2015

Purpose:This study was to investigate the dosimetric benefit of a novel intensity modulated radiation therapy (IMRT) technique for irradiating the left breast and regional lymph node (RLN).Methods:The breast and RLN (internal mammary node and periclavicular node) and normal tissue were contoured for 16 consecutive left‐sided breast cancer patients previously treated with RT after lumpectomy. Nine equi‐spaced fields IMRT (9 ‐field IMRT), tangential multi‐beam IMRT (tangential‐IMRT) and IMRT with fixed‐jaw technique (FJT‐IMRT) were developed and compared with three‐dimensional conformal RT (3DCRT). Prescribed dose was 50 Gy in 25 fractions. Dose distributions and dose volume histograms were used to evaluate plans.Results:All IMRTs achieved similar target coverage and substantially reduced heart V30 and V20 compared to the 3DCRT. The average heart mean dose had different changes, which were 9.0Gy for 9‐field IMRT, 5.7Gy for tangential‐IMRT and 4.2Gy for FJT‐IMRT. For the contralateral lung and breast, the 9‐field IMRT has the highest mean dose; and the FJT‐IMRT and tangential‐IMRT had similar lower value. For the thyroid, both 9‐field IMRT and FJT‐IMRT had similar V30 (20% and 22%) and were significantly lower than that of 3DCRT (34%) and tangential‐IMRT (46%). Moreover, the thyroid mean dose of FJT‐IMRT is the lowest. For cervical esophagus and humeral head, the FJT‐IMRT also had the best sparing.Conclusion:All 9‐field IMRT, tangential‐IMRT and FJT‐IMRT had superiority for targets coverage and substantially reduced the heart volume of high dose irradiation. The FJT‐IMRT showed advantages of avoiding the contralateral breast and lung irradiation and decreasing the thyroid, humeral head and cervical esophagus radiation dose at the expense of a slight monitor units (MUs) increasing.
SU‐E‐T‐60: A Plan Quality Index in IMRT QA That Is Independent of the Acceptance Criteria
Authors: Kim D , Kim S , Kang S , Kim T , Kim K , Park S , Cho M , Shin D , Suh T 
Published: June 2015

Purpose:In IMRT QA, plan quality evaluation is made based on pass rate under preset acceptance criteria, mostly using gamma‐values. This method is convenient but, its Result highly depends on what the acceptance criteria are and suffers from the lack of sensitivity in judging how good the plan is. In this study, we introduced a simple but effective plan quality index of IMRT QA based on dose difference only to supplement such shortcomings, and investigated its validity.Methods:The proposed index is a single value which is calculated mainly based on point‐by‐point comparison between planned and measured dose distributions, and it becomes “1” in an ideal case. A systematic evaluation was performed with one‐dimensional test dose distributions. For 3 hypothetical dose profiles, various displacements (in both dose and space) were introduced, the proposed index was calculated for each case, and the behavior of obtained indices was analyzed and compared with that of gamma evaluation. In addition, the feasibility of the index was assessed with clinical IMRT/VMAT/SBRT QA cases for different sites (prostate, head & neck, liver, lung, spine, and abdomen).Results:The proposed index showed more robust correlation with the amount of induced displacement compared to the gamma evaluation method. No matter what the acceptance criteria are (e.g., whether 3%/3mm or 2%/2mm), it was possible to clearly rank every case with the proposed index while it was difficult to do with the gamma evaluation method.Conclusion:IMRT plan quality can be evaluated quantitatively by the proposed index. It is considered that the proposed index would provide useful information for better judging the level of goodness of each plan and its Result is independent of the acceptance criteria.This work was supported by the Radiation Technology R&D program (No. 2013M2A2A7043498) and the Mid‐career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
SU‐E‐T‐67: A Quality Assurance Procedure for VMAT Delivery Technique with Multiple Verification Metric Using TG‐119 Protocol
Authors: Katsuta Y , Kadoya N , Shimizu E , Matsunaga K , Inoue M , Majima K , Jingu K 
Published: June 2015

Purpose:A successful VMAT plan delivery includes precise modulations of dose rate, gantry rotational and multi‐leaf collimator shapes. The purpose of this research is to construct routine QA protocol which focuses on VMAT delivery technique and to obtain a baseline including dose error, fluence distribution and mechanical accuracy during VMAT.Methods:The mock prostate, head and neck (HN) cases supplied from AAPM were used in this study. A VMAT plans were generated in Monaco TPS according to TG‐119 protocol. Plans were created using 6 MV and 10 MV photon beams for each case. The phantom based measurement, fluence measurement and log files analysis were performed. The dose measurement was performed using 0.6 cc ion chamber, which located at isocenter. The fluence distribution were acquired using the MapCHECK2 mounted in the MapPHAN. The trajectory log files recorded inner 20 leaf pairs and gantry angle positions at every 0.25 sec interval were exported to in‐house software developed by MATLAB and determined those RMS values.Results:The dose difference is expressed as a ratio of the difference between measured and planned doses. The dose difference for 6 MV was 0.91%, for 10 MV was 0.67%. In turn, the fluence distribution using gamma criteria of 2%/2 mm with a 50% minimum dose threshold for 6 MV was 98.8%, for 10 MV was 97.5%, respectively. The RMS values of MLC for 6 MV and 10 MV were 0.32 mm and 0.37 mm, of gantry were 0.33 degree and 0.31 degree.Conclusion:In this study, QA protocol to assess VMAT delivery accuracy is constructed and results acquired in this study are used as a baseline of VMAT delivery performance verification.
SU‐E‐T‐71: A Radiochromic Film Based Quantitative Assessment of Thermoplastic Mask Bolus Effect in Head and Neck IMRT/VMAT
Authors: Kalavagunta C , Lin M , Snider J , Xu H , Schrum A , Vadnais P , Marter K , Suntharalingam M , Prado K 
Published: June 2015

Purpose:To quantify the factors leading to thermoplastic mask bolus‐associated‐increased skin dose in head and neck IMRT/VMAT using EBT2 film.Methods:EBT2 film placed beneath a dual layer 3‐point ORFIT head, neck and shoulder mask was used to test the effect of mask thickness, beam modulation, air gap, and beam obliquity on bolus effect. Mask thickness was varied based on the distribution of 1.6mm Orfilight layer on top of 2 mm Efficast layer. Beam modulation was varied by irradiating the film with an open field (no beam modulation) and a step and shoot field (beam modulation). Air gap between mask and film was varied from 0 to 5mm. Beam obliquity was varied by irradiating the film at gantry angles of 0°, 35°, and 70°.Finally, film strips placed on a Rando phantom under an Orfit mask, in regions of expected high dose, were irradiated using 5 IMRT and 5 VMAT plans with various modulation levels (modulation factor 2 to 5) and the results were compared with those obtained placing OSLDs at the same locations.Results:An 18–34% increase in mask bolus effect was observed for three factors where the effect of beam obliquity ≥ beam modulation > mask thickness. No increase in mask bolus effect was observed for change in air gap. A 6–13% increase in dose due to mask bolus effect was observed on film strips.Conclusion:This work underlines the role of beam obliquity and beam modulation combined with thermoplastic mask thickness in increasing mask bolus‐associated skin dose in head and neck IMRT/VMAT. One possible method of dose reduction, based on knowledge gained from this work, is inclusion of skin as an avoidance structure in treatment planning. Another approach is to design a mask with the least amount of thermoplastic material necessary for immobilization.
SU‐E‐T‐73: A Robust Proton Beam Therapy Technique for High‐Risk Prostate Cancer Whole Pelvis Irradiation: Bilateral Opposed Single Field Uniform Dose (SFUD) Plan with Lateral Penumbra Gradient Matching
Authors: Ding X , Wu H , Rosen L 
Published: June 2015

Purpose:To develop a clinical feasible and robust proton therapy technique to spare bowel, bladder and rectum for high‐risk prostate cancer patientsMethods:The study includes 3 high‐risk prostate cancer cases treated with bilateral opposed SFUD with lateral penumbra gradient matching technique prescribed to 5400cGyE in 30 fx in our institution. To treat whole pelvic lymph node chain, the complicated ‘H’ shape, using SFUD technique, we divided the target into two sub‐targets (LLAT beam treating ‘90 degree T‐shape’ and RLAT beam treating ‘: shape’) in Plan A and use lateral penumbra gradient matching at patient's left side. Vice verse in Plan B. Each plan deliver half of the prescription dose. Beam‐specific PTVs were created to take range uncertainty and setup error into account. For daily treatment, patient received four fields from both plan A and B per day. Robustness evaluation were performed in the worst case scenario with 3.5% range uncertainty and 1, 2, 3mm overlap or gap between LLAT and RLAT field matching in Raystation 4.0. All of cases also have a Tomotherapy backup plan approved by physician as a dosimetric comparison.Results:The total treatment time take 15–20mins including IGRT and four fields delivery on ProteusONE, a compact size PBS proton system, compared to 25–30min in traditional Tomotherapy. Robustness analysis shows that this plan technique is insensitive to the range uncertainties. With the lateral gradient matching, 1, 2, 3mm overlap renders only 2.5%, 5.5% and 8% hot or cool spot in the junction areas. Dosimetric comparisons with Tomotherapy show a significant dose reduction in bladder D50%(14.7±9.3Gy), D35%(7.3±5.8Gy); small bowel and rectum average dose(19.6±7.5Gy and 14.5±6.3Gy respectively).Conclusion:The bilateral opposed(SFUD) plan with lateral penumbra gradient matching has been approved to be a safe, robust and efficient treatment option for whole pelvis high‐risk prostate cancer patient which significantly spares the OARs.
SU‐E‐T‐79: A Study of the Effect of Clinical Tumor Volume Displacement On the Dosage of Post Modified Radical Mastectomy Intensity‐Modulated Radiation Therapy Plans for Left‐Sided Breast Cancer
Authors: Zhang W , Ma C , Li D , Wu F 
Published: June 2015

Purpose:To explore the effect of clinical tumor volume (CTV) displacement on the dosage of intensity‐modulated radiation therapy (IMRT) plans for left‐sided breast cancer after modified radical mastectomy.Methods:We created 2 sets of IMRT plans based on PTV0.5 and PTV0.7 (with CTV displacement of 0.5cm and 0.7cm respectively) for each of the ten consecutive left‐sided breast cancer patients after modified radical mastectomy, and compared the difference in PTV coverage and organ at risk (OAR) sparing between the two groups. And then, we compared the difference in PTV coverage in IMRT plans based on PTV0.5 between the group with properly estimated CTV displacement (presuming the actual CTV displacement was 0.5cm) and the one with underestimated CTV displacement (presuming the actual CTV displacement was 0.7cm). The difference in results between the corresponding two groups was compared using paired‐sample t‐test. P values less than 0.05 were considered statistically significant.Results:IMRT plans derived from PTV0.5 had more homogenous PTV coverage, and less heart, left lung, right breast, right lung, left humeral head and B‐P radiation exposure, as well as less total Mu as compared with the ones stemmed from PTV0.7 (all p<0.05). IMRT plans with appropriate estimation of CTV displacement had better PTV coverage compared with the ones with underestimated CTV displacement (all p<0.01).Conclusion:The IMRT plans with smaller CTV displacement in post modified radical mastectomy radiotherapy for left‐sided breast cancer has dosimetrical advantages over the ones with larger CTV displacement. Underestimation of CTV displacement can lead to significant reduction of PTV coverage. Individually quantifying and minimizing CTV displacement can significantly improve PTV coverage and OAR (including heart and left lung) sparing.This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)