bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐21: A Novel Beam‐Light View, Collimating Applicator for HDR Ocular Conjunctiva Brachytherapy‐Treatments
Authors: Koren S , Kindler J , Tafo A Guemnie , Cohen G , Reich E 
Published: July 2016

Purpose:We propose the use of a HDR X‐ray source collimator to apply a conformal, relatively small, radiation suitable for a single fraction with short delivery time. In addition, this technique can be applied using a radioactive source.Methods:We have built a stainless steel 1.5 mm thick applicator, to accommodate the needle applicator of the Intra‐Beam X‐ray source. Additional cavity is created in the applicator to allow the hosting/nesting/positioning of a LED diode. This LED is allowing a pre‐irradiation beam marking on the tissue. The visible light emitted from the opening of the collimated applicator will delineate/verify the aperture of the kV beam to be applied, as well as serve as distance indicator and will assist in the determination of dose to be delivered. For the evaluation of the collimated spatial dose distribution we have performed water tank measurements using (IBA Dosimetry) with a 0.4 cc ion chamber (IBA Dosimetry). We have scanned a two dimensional array with 1mm pitch in depth and 0.3 mm step size laterally. Additional verifications were conducted using Gaf‐Chromic film for PDD measurements and Optical Stimulated Luminescence Dosimetry (OSLD, Landauer inc.) for absolute dosimetry.Results:The collimated applicator enables a conformal irradiated cross‐section of about 3 mm square at the applicator surface was used in this study. A 180 seconds of 50 kVp delivery yielded 29 Gy, 20.6 Gy and 14.5 Gy at 5, 10 and 15 mm depths respectively. These results are in good agreement with the needle applicator depth dose curve published data.Conclusion:We have demonstrated the feasibility of focal HDR brachytherapy for conjunctival and ocular tumors, using the Intra‐Beam needle applicator with in‐house developed collimator. The delivery time was found to be several minutes‐ suitable for an intra‐operative procedure and will allow dose fractionation deliveries.
SU‐F‐T‐23: Correspondence Factor Correction Coefficient for Commissioning of Leipzig and Valencia Applicators with the Standard Imaging IVB 1000
Authors: Donaghue J , Gajdos S 
Published: July 2016

Purpose:To determine the correction factor of the correspondence factor for the Standard Imaging IVB 1000 well chamber for commissioning of Elekta's Leipzig and Valencia skin applicators.Methods:The Leipzig and Valencia applicators are designed to treat small skin lesions by collimating irradiation to the treatment area. Published output factors are used to calculate dose rates for clinical treatments. To validate onsite applicators, a correspondence factor (CFrev) is measured and compared to published values. The published CFrev is based on well chamber model SI HDR 1000 Plus. The CFrev is determined by correlating raw values of the source calibration setup (Rcal,raw) and values taken when each applicator is mounted on the same well chamber with an adapter (Rapp,raw). The CFrev is calculated by using the equation CFrev =Rapp,raw/Rcal,raw. The CFrev was measured for each applicator in both the SI HDR 1000 Plus and the SI IVB 1000. A correction factor, CFIVB for the SI IVB 1000 was determined by finding the ratio of CFrev (SI IVB 1000) and CFrev (SI HDR 1000 Plus).Results:The average correction factors at dwell position 1121 were found to be 1.073, 1.039, 1.209, 1.091, and 1.058 for the Valencia V2, Valencia V3, Leipzig H1, Leipzig H2, and Leipzig H3 respectively. There were no significant variations in the correction factor for dwell positions 1119 through 1121.Conclusion:By using the appropriate correction factor, the correspondence factors for the Leipzig and Valencia surface applicators can be validated with the Standard Imaging IVB 1000. This allows users to correlate their measurements with the Standard Imaging IVB 1000 to the published data. The correction factor is included in the equation for the CFrev as follows: CFrev= Rapp,raw/(CFIVB*Rcal,raw). Each individual applicator has its own correction factor, so care must be taken that the appropriate factor is used.
SU‐F‐T‐25: Design and Implementation of a Multi‐Purpose Applicator for Pelvic Brachytherapy Applications
Authors: Bogue J , Parsai E 
Published: July 2016

Purpose:The current generation of inflatable multichannel brachytherapy applicators, such as the Varian Capri, have limited implementation to only vaginal and rectal cancers. While there are similar designs utilizing rigid, non‐inflatable applicators, these alternatives could cause increased dose to surrounding tissue due to air gaps. Modification of the Capri could allow for easier treatment planning by reducing the number of channels and increased versatility by modifying the applicator to include an attachable single tandem for cervical or multiple tandems for endometrial applications.Methods:A Varian Capri applicator was simulated in water to replicate a patient. Multiple plans were optimized to deliver a prescribed dose of 100 cGy at 5mm away from the exterior of the applicator using six to thirteen existing channels. The current model was expanded upon to include a detachable tandem or multiple tandoms to increase its functionality to both cervical and endometrial cancers. Models were constructed in both threedimensional rendering software and Monte Carlo to allow prototyping and simulations.Results:Treatment plans utilizing six to thirteen channels produced limited dosimetric differences between channel arrangements, with a seven channel plan very closely approximating the thirteen channels. It was concluded that only seven channels would be necessary in future simulations to give an accurate representation of the applicator. Tandem attachments were prototyped for the applicator to demonstrate the ease of which they could be included. Future simulation in treatment planning software and Monte Carlo results will be presented to further define the ideal applicator geometryConclusion:The current Capri applicator design could be easily modified to increase applicability to include cervical and endometrial treatments in addition to vaginal and rectal cancers. This new design helps in a more versatile single use applicator that can easily be inserted and to further reduce dose to critical structures during brachytherapy treatments.
SU‐F‐T‐27: A Comparative Case Study Among Four Modalities for the Superficial Treatment of Squamous Cell Carcinoma
Authors: Ashenafi M , Koch N , Peng J , Terwillinger L , Wilder J , McDonald D , Mart C , Jenrette J , Vanek K 
Published: July 2016

Purpose:We performed a comparative planning study among High Dose Rate (HDR) brachytherapy, superficial electrons, Volume Modulated Arc Therapy (VMAT), and Helical IMRT (Tomotherapy) for squamous cell carcinoma of the abdominal wall with consideration for the underlining bowel.Methods:A 69‐year old female presented with squamous cell carcinoma protruding 8mm beyond the anterior skin surface of the midabdomen was considered for treatment. The patient had a ventral hernia which resulted in the reduction of the abdominal wall thickness and the adjacent small bowel being the dose limiting structure. Four plans were generated using different treatment modalities: a) an enface electron field (eMC, Eclipse v. 11), b) Tomotherapy (HI‐Art II v.5.0.5), c) VMAT (Acuros, Eclipse v. 11), and d) HDR using a Freiburg applicator (Oncentra v. 4.3). The following plan objectives were used for all four plans: for the CTV target, V90% ≥90% (61.8Gy2/2).For the small bowel, D0.1cc < 56.2 Gy2/2 was a hard constraint and expressed as a percentage of the prescription for comparison to demonstrate the dose fall‐off achieved among the modalities.For HDR, V200% <0.1cc was an additional constraint. Multiple dosimetric parameters, including those listed above, were compared among the four modalities.Results:The HDR plan showed comparable target coverage compared to the Tomotherapy plan and better coverage compared to the electron plan. Small bowel doses (D0.1cc) were lower in HDR plan compared to Tomotherapy, electron, & VMAT plans (88.8%, 89.6%, 90.9%, & 96.6%). Integral dose to the whole body (V5%) was much higher for HDR, VMAT, and Tomotherapy when compared to electron plan by factors of seven, eight, and ten, respectively. After reviewing all treatment modalities, the physician selected HDR owing to better control of the small bowel dose while maintaining adequate target coverage.Conclusion:This case study demonstrated HDR can successfully treat superficial lesions with superior sparing of underlying structures.
SU‐F‐T‐28: Evaluation of BEBIG HDR Co‐60 After‐Loading System for Skin Cancer Treatment Using Conical Surface Applicator
Authors: Safigholi H , Meigooni A S , Han D , Soliman A , Song W Y 
Published: July 2016

Purpose:To evaluate the possibility of utilizing the BEBIG HDR 60Co remote after‐loading system for malignant skin surface treatment using Monte Carlo (MC) simulation technique.Methods:First TG‐43 parameters of BEBIG‐Co‐60 and Nucletron Ir‐192‐mHDR‐V2 brachytherapy sources were simulated using MCNP6 code to benchmark the sources against the literature. Second a conical tungsten‐alloy with 3‐cm diameter of Planning‐Target‐Volume (PTV) at surface for use with a single stepping HDR source is designed. The HDR source is modeled parallel to treatment plane at the center of the conical applicator with a source surface distance (SSD) of 1.5‐cm and a removable plastic end‐cap with a 1‐mm thickness. Third, MC calculated dose distributions from HDR Co‐60 for conical surface applicator were compared with the simulated data using HDR Ir‐192 source. The initial calculations were made with the same conical surface applicator (standard‐applicator) dimensions as the ones used with the Ir‐192 system. Fourth, the applicator wall‐thickness for the Co‐60 system was increased (doubled) to diminish leakage dose to levels received when using the Ir‐192 system. With this geometry, percentage depth dose (PDD), and relative 2D‐dose profiles in transverse/coronal planes were normalized at 3‐mm prescription‐depth evaluated along the central axis.Results:PDD for Ir‐192 and Co‐60 were similar with standard and thick‐walled applicator. 2D‐relative dose distribution of Co‐60, inside the standard‐conical‐applicator, generated higher penumbra (7.6%). For thick‐walled applicator, it created smaller penumbra (<4%) compared to Ir‐192 source in the standard‐conicalapplicator. Dose leakage outside of thick‐walled applicator with Co‐60 source was approximately equal (≤3%) with standard applicator using Ir‐192 source.Conclusion:Skin cancer treatment with equal quality can be performed with Co‐60 source and thick‐walled conical applicators instead of Ir‐192 with standard applicators. These conical surface applicator must be used with a protective plastic end‐cap to eliminate electron contamination and over‐dosage of the skin.
SU‐F‐T‐30: Comprehensive Dosimetric Characterization of the Novel Direction Modulation Brachytherapy (DMBT) Tandem Applicator Using Monte Carlo Simulations
Authors: Safigholi H , Han D , Mashouf S , Soliman Abraam , Owrangi A , Song W Y 
Published: July 2016

Purpose:To characterize the dosimetric properties/distributions of the novel proposed direction modulated brachytherapy (DMBT) tandem applicator in combination with 192Ir HDR source, and compare against conventional tandem design, using Monte Carlo simulations.Methods:The proposed DMBT tandem applicator is designed for image‐guided adaptive brachytherapy, especially MRI, of cervical cancer. It has 6 peripheral holes of 1.3‐mm width, grooved along a 5.4‐mm diameter nonmagnetic tungsten alloy rod of density 18.0 g/cc, capable of generating directional dose profiles – leading to enhanced dose sculpting capacity through inverse planning. In‐water dosimetric parameters for the DMBT and conventional tandems have been calculated for various radial distances away and around the tandems. For the DMBT tandem, the cumulative dose from the 192Ir source occupying 1) one and 2) all six holes in equal dwell times was calculated and normalized to match the dose rate of the open source (in conventional tandem) at 1 cm from the center. This is done to compare and contrast the characteristic dose distributions to that of the isotropic TG43‐based 192Ir source.Results:All dose rates were normalized at 1‐cm radius from the center of the applicators, containing source(s). The normalized dose rates at 0.5, 3.0, and 5.0‐cm radiuses were then 388, 11.3, and 4.1% for conventional tandem, 657, 8.1, and 2.7% for DMBT tandem with the source in one hole at front entrance, and 436, 10.9, and 3.8% for DMBT tandem with the source in all six holes. For the DMBT tandem case with the source in one hole, the backside transmissions were 47, 2.4, and 0.9%, respectively.Conclusion:The DMBT tandem is able to generate closely similar dosimetric characteristics as that of the single‐channel conventional tandem if needed (with the source occupying all six holes), at the same time, generate directional radiation profile(s) for favorably enabling 3D dose sculpting capability.
SU‐F‐T‐33: Air‐Kerma Strength and Dose Rate Constant by the Full Monte Carlo Simulations
Authors: Tsuji S , Oita M , Narihiro N 
Published: July 2016

Purpose:In general, the air‐kerma strength (Sk) has been determined by the energy weighting the photon energy fluence and the corresponding mass‐energy absorption coefficient or mass‐energy transfer coefficient. Kerma is an acronym for kinetic energy released per unit mass, defined as the sum of the initial kinetic energies of all the charged particles. Monte Carlo (MC) simulations can investigate the kinetic energy of the charged particles after photo interactions and sum the energy. The Sk of 192Ir source is obtained in the full MC simulation and finally the dose rate constant Λ is determine.Methods:MC simulations were performed using EGS5 with the microSelectron HDR v2 type of 192Ir source. The air‐kerma rate obtained to sum the electron kinetic energy after photoelectric absorption or Compton scattering for transverse‐axis distance from 1 to 120 cm with a 10 m diameter air phantom. Absorbed dose in water is simulated with a 30 cm diameter water phantom. The transport cut‐off energy is 10 keV and primary photons from the source need two hundred and forty billion in the air‐kerma rate and thirty billion in absorbed dose in water.Results:Sk is multiplied by the square of the distance in air‐kerma rate and determined by fitting a linear function. The result of Sk is (2.7039±0.0085)*10‐−11 µGy m2 Bq−1 s−1. Absorbed dose rate in water at 1 cm transverse‐axis distance D(r0, θ0) is (3.0114±0.0015)*10−11 cGy Bq−1 s−1.Conclusion:From the results, dose rate constant Λ of the microSelectron HDR v2 type of 192Ir source is (1.1137±0.0035) cGy h−1 U−1 by the full MC simulations. The consensus value conΛ is (1.109±0.012) cGy h−1 U−1. The result value is consistent with the consensus data conΛ.
SU‐F‐T‐35: Optimization of Bladder and Rectal Doses Using a Multi‐Lumen Intracavitary Applicator for Gynecological Brachytherapy
Authors: Laoui S , Dietrich S , Sehgal V , Al‐Ghazi M 
Published: July 2016

Purpose:Radiation dose delivery for endometrial cancer using HDR techniques is limited by dose to bladder and rectum. A dosimetric study was performed using Varian Capri vaginal brachytherapy applicator to determine the optimal channel configuration which minimizes dose to bladder and rectum, while providing good target coverage.Methods:A total of 17 patients, 63 plans clinically delivered, and 252 simulated plans using Varian BrachyVision planning system were generated to investigate optimal channel configuration which results in minimum dose to bladder and rectum while providing adequate target coverage. The Capri applicator consists of 13 lumens arranged in two concentric rings, one central lumen and six lumens per ring. Manual dose shaping is invariably required to lower the dose to critical organs. Three‐dimensional plans were simulated for 4 channel arrangements, all 13 channels, channel 12 o'clock (close to bladder) and 6 o'clock (close to rectum) deactivated, central channel deactivated, and central channel in addition to 12 o'clock and 6 o'clock deactivated. A relationship between V100, the volume that receives the prescribed dose, and the amount of curie‐seconds required to deliver it, was established.Results:Using all 13 channels results in maximum dose to bladder and rectum. Deactivating central channel in addition to 12 o'clock and 6 o'clock resulted in minimizing bladder and rectum doses but compromised target coverage. The relationship between V100, the volume that receives the prescribed dose, and the curie seconds was found to be linear.Conclusion:Deactivating channels 12 o'clock and 6 o'clock was shown to be the optimal configuration leading to minimum dose to bladder and rectum without compromising target coverage. The linear relationship between V100 and the curie‐ seconds can be used as a verification parameter.
SU‐F‐T‐37: Dosimetric Evaluation of Planned Versus Decay Corrected Treatment Plans for the Treatment of Tandem‐Based Cervical HDR Brachytherapy
Authors: Goyal M , Manjhi J , Kehwar T , Rai D , Barker J , Heintz B , Shide K 
Published: July 2016

Purpose:This study evaluated dosimetric parameters for actual treatment plans versus decay corrected treatment plans for cervical HDR brachytherapy.Methods:125 plans of 25 patients, who received 5 fractions of HDR brachytherapy, were evaluated in this study. Dose was prescribed to point A (ICRU‐38) and High risk clinical tumor volume (HR‐CTV) and organs at risk (OAR) were, retrospectively, delineated on original CT images by treating physician. First HDR plan was considered as reference plan and decay correction was applied to calculate treatment time for subsequent fractions, and was applied, retrospectively, to determine point A, HR‐CTV D90, and rectum and bladder doses.Results:The differences between mean point A reference doses and the point A doses of the plans computed using decay times were found to be 1.05%±0.74% (−2.26% to 3.26%) for second fraction; −0.25%±0.84% (−3.03% to 3.29%) for third fraction; 0.04%±0.70% (−2.68% to 2.56%) for fourth fraction and 0.30%±0.81% (−3.93% to 2.67%) for fifth fraction. Overall mean point A dose difference, for all fractions, was 0.29%±0.38% (within ± 5%). Mean rectum and bladder dose differences were calculated to be −3.46%±0.12% and −2.47%±0.09%, for points, respectively, and −1.72%±0.09% and −0.96%±0.06%, for D2cc, respectively. HR‐CTV D90 mean dose difference was found to be −1.67% ± 0.11%. There was no statistically significant difference between the reference planned point A doses and that calculated using decay time to the subsequent fractions (p<0.05).Conclusion:This study reveals that a decay corrected treatment will provide comparable dosimetric results and can be utilized for subsequent fractions of cervical HDR brachytherapy instead of actual treatment planning. This approach will increase efficiency, decrease workload, reduce patient observation time between applicator insertion and treatment delivery. This would be particularly useful for institutions with limited resources or large patient populations with limited access to care.
SU‐F‐T‐43: Prediction of Dose Increments by Brain Metastases Resection Cavity Shrinkage Model with I‐125 and Cs‐131 LDR Seed Implantations
Authors: Han D , Braunstein S , Sneed P , McDermott M , Ma L 
Published: July 2016

Purpose:This work aims to determine dose variability via a brain metastases resection cavity shrinkage model (RC‐SM) with I‐125 or Cs‐131 LDR seed implantations.Methods:The RC‐SM was developed to represent sequential volume changes of 95 consecutive brain metastases patients. All patients underwent serial surveillance MR and change in cavity volume was recorded for each patient. For the initial resection cavity, a prolate‐ellipsoid cavity model was suggested and applied volume shrinkage rates to correspond to 1.7, 3.6, 5.9, 11.7, and 20.5 months after craniotomy. Extra‐ring structure (6mm) was added on a surface of the resection volume and the same shrinkage rates were applied. Total 31 LDR seeds were evenly distributed on the surface of the resection cavity. The Amersham 6711 I‐125 seed model (Oncura, Arlington Heights, IL) and the Model Cs‐1 Rev2 Cs‐131 seed model (IsoRay, Richland, WA) were used for TG‐43U1 dose calculation and in‐house‐programed 3D‐volumetric dose calculation system was used for resection cavity rigid model (RC‐RM) and the RC‐SM dose calculation.Results:The initial resection cavity volume shrunk to 25±6%, 35±6.8%, 42±7.7%, 47±9.5%, and 60±11.6%, with respect to sequential MR images post craniotomy, and the shrinkage rate (SR) was calculated as SR=56.41Xexp(−0.2024Xt)+33.99 and R‐square value was 0.98. The normal brain dose as assessed via the dose to the ring structure with the RC‐SM showed 29.34% and 27.95% higher than the RC‐RM, I‐125 and Cs‐131, respectively. The dose differences between I‐125 and Cs‐131 seeds within the same models, I‐125 cases were 9.17% and 10.35% higher than Cs‐131 cases, the RC‐RM and the RC‐SM, respectively.Conclusion:A realistic RC‐SM should be considered during LDR brain seed implementation and post‐implement planning to prevent potential overdose. The RC‐SM calculation shows that Cs‐131 is more advantageous in sparing normal brain as the resection cavity volume changes with the LDR seeds implementation.
SU‐F‐T‐45: Dosimetric Effects of Saline Filled Balloons During IORT Using Xoft Electronic Brachytherapy
Authors: Redler G , Templeton A , Turian J , Chu J , Bernard D , Zhen H , Liao Y 
Published: July 2016

Purpose:The portability of Xoft Axxent Electronic Brachytherapy (EBx) System has made it a viable option for intraoperative radiation therapy (IORT) treatment of early‐stage breast cancer. The low energy (50kVp) of the X‐ray source makes the shielding easy, but also means its dose distribution is sensitive to the medium's composition. Current treatment planning systems (TPS) typically assume homogenous water for brachytherapy dose calculations, including the pre‐calculated atlas plans for the Xoft IORT cases. However, Xoft recommends using saline to fill the balloon applicator. This study investigates the dosimetric difference due to the increased effective atomic number (Zeff) from water (7.42) to saline (7.56).Methods:The diameter of the balloon applicators ranges from 3–6cm, with 4cm being most frequently used. For the 4‐cm and 6‐cm diameter applicators, MCNP Monte Carlo program was used to calculate the dose at the surface (Ds) of the middle section of the balloon and 1 cm away (D1cm) for water‐ and saline‐filled balloons: one plan with a single dwell at the center and another with multiple dwells as in the atlas plans. The single dwell plan is a simple estimation of the dosimetry, while the atlas plan is representative of the actual dose distribution.Results:The single‐dwell plan showed a 5.1% and 6.1% decrease in Ds for the 4‐ and 6‐cm applicators, respectively, due to the saline. The atlas plan showed similarResults:4.8% and 6.4% decrease, respectively. The decrease in D1cm is 4.3%–5.2% and 3.3%–5.3s% in the single‐dwell and atlas plans, respectively, for the 4‐ and 6‐cm applicator.Conclusion:The dosimetric effect introduced by saline is on the order of 5%. This effect should be taken into account during both treatment planning and patient outcome studies.