bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐FF‐T‐43: Feasibility of Using Radioactive Bone Cement to Treat Vertebral Metastases
Authors: Kaneko T , Sehgal V , Skinner H , Al‐Ghazi M , Hoang B , Ramsinghani N , Keyak J 
Published: April 2010

Purpose: To evaluate the feasibility of using radioactive bone cement to deliver therapeutic radiation to the vertebral body without undue risk to the spinal cord, i.e. vertebral brachytherapy. Method and Materials: CT‐scan based Monte Carlo N‐Particle radiation transport models, consisting of a three‐dimensional rectangular lattice of 0.625×0.625×1.25‐mm voxels, were created of a T‐12 human cadaveric vertebra. Trabecular and cortical bone were both represented by a spectrum of thirty complementary volume fractions of solid cortical bone and bone marrow, and all soft tissue was represented as a single material. A cylindrical volume of radioactive bone cement was simulated within the model, and two candidate radioisotopes were studied: P‐32 and Sr‐89. Thirty million particle histories were simulated (MCNPX v.2.5.0) to characterize the dose distribution within the vertebral body. Results: The dose distributions for both radioisotopes were axisymmetric about the cement implant and rapidly decreased with increasing distance from the cement. Initial activities of 0.94 mCi and 0.51 mCi for P‐32 and Sr‐89, respectively, would deliver >300 Gy to bone within 1.6 mm of the cement implant and >80 Gy to bone within 2.8 mm, while keeping the dose at 3.4 mm under 45 Gy. Conclusion: The predicted dose distributions show that a therapeutic radiation dose would be delivered to all bone within ∼3 mm of the cement without undue risk to tissue beyond 3.4 mm (such as the spinal cord), indicating preliminary feasibility of this technique. With further development, this technology may yield a clinically‐feasible procedure that would eliminate the need for 10 radiotherapy sessions, making it convenient for the patient, while potentially improving the clinical outcome by delivering a higher dose to the tumor and a lower dose to the spinal cord than conventional radiotherapy.Conflict of Interest (only if applicable): Research sponsored by Bone‐Rad Therapeutics, Inc.
SU‐FF‐T‐51: Robotically‐Assisted Minimally Invasive Brachytherapy: Dosimetric Aspects
Authors: Hanley J , Napoli J , Barbiere J , Tuna M , Smith D , Godfrey L 
Published: April 2010

Purpose: To investigate the dosimetric aspects of robotically‐assisted minimally invasive brachytherapy. Materials and Methods: Using the Intuitive Surgical DaVinci S System, the following were inserted into a porcine abdominopelvic cavity through a 12 mm auxiliary port and sutured directly to the pelvic sidewall: three 6‐French catheters; the Xoft Axxent delivery system; a prototype minimally invasive applicator (MIA). Plans were generated in Nucletron's treatment planning software for an Ir‐192 source and the Xoft 50 kV source. The ability of the prototype MIA to reproducibly position catheters was tested using film dosimetry. Other applicators were designed to allow an en face application of the source, and various catheter arrangements were investigated. For the en face application, the sensitivity of the delivered dose to random deviations from normal incidence of the catheters (⩽ 5 degrees) and regular catheter spacing were tested. Results: All three trials for introducing the catheters were performed with ease by the surgeon. After the apparatus was sutured into place, it maintained a fixed geometry. The dosimetric measurements using GafChromic EBT film showed a uniform distribution of dose. The treatment plan for the en‐face arrangement using the Xoft source with 16 catheters at random angles showed a deviation from the planned dose of ⩽ 0.39%.Conclusions: The feasibility of performing robotically‐assisted minimally invasive brachytherapy was demonstrated for techniques utilizing both parallel and en face geometries. A customized applicator was designed to deliver a uniform dose to the target. The reproducibility of the device was confirmed with film dosimetry. For the geometries tested, the en face application was found to be insensitive to random deviations of the catheters of up to 5 degrees from normal incidence. These techniques may be used for minimally invasive intra‐operative or post‐operative brachytherapy procedures using real‐time or atlas‐based planning.
SU‐FF‐T‐126: Initial Experience with Philips SmartArc On An Elekta Linac
Authors: Shepard D , Ca D , Rao M , Chen F , Mehta V 
Published: April 2010

Purpose: The recent introduction of delivery control systems capable of delivering intensity modulated arc therapy (IMAT) has led to renewed interest in arc‐based IMRT delivered on a conventional linac. A key challenge to successful implementation of IMAT is the need for robust inverse planning tools capable of properly accounting for IMAT delivery constraints. In this work, we evaluate a new IMAT planning module, called SmartArc, designed for the Pinnacle3 treatment planning system. Method and Materials: In February 2009, we received an alpha version of the SmartArc planning module for the Pinnacle3 treatment planning system. The SmartArc tools were developed by RaySearch and build on the existing direct machine parameter optimization (DMPO) functionality in Pinnacle3. The SmartArc module was used to create 9 IMAT plans (4 head‐and‐neck, 2 lung, and 3 prostates). Each plan was verified on an Elekta Synergy with the PreciseBeam VMAT delivery control system using the IBA Matrixx 2D ionization chamber array. Each plan was compared with a corresponding fixed‐field IMRT or helical tomotherapy plan in terms of both plan quality and delivery efficiency. Results: A single arc was sufficient to produce highly conformal IMAT treatment plans for the prostate and lung cases. On average, the prostate plans required 536 monitor units and delivered in 1.9 minutes while the lung plans required 750 monitor units and delivered in 2.2 minutes. For the more complex head‐and‐neck cases, the use of two arcs was necessary to meet the treatment goals and an average of 607 monitor units and 5.4 minutes were required. Conclusion: The SmartArc module in Pinnacle3 serves as a robust IMAT planning tool capable of planning both single arc and multiple arc deliveries. 2D gamma analysis showed that all plans verified with greater than 95% of the measured points meeting our 3%/3mm criteria.Research supported by Elekta
SU‐FF‐T‐131: Assessing the Dosimetric Impact of Intra‐Fraction Prostate Motion On Step‐And‐Shoot IMRT Plans
Authors: Langen K , Moore J , Kupelian P , Siebers J 
Published: April 2010

Purpose: To assess the dosimetric impact of intra‐fraction prostate motion for step‐and‐shoot IMRT plans. Method and Materials: For step‐and‐shoot IMRT plans, fluence maps for each segment are exported from the Pinnacle treatment planning system. Each fluence map segment is modified to simulate the effect of prostate motion observed during the simulated delivery. Modified fluence maps are re‐imported into Pinnacle for dose calculations. Calculated dose distributions are compared with unmodified fluence maps dose distributions to assess the impact of intrafraction motion on the dose delivery. Measured Calypso motion tracks for 16 patients (515 tracks) are used. Changes in prostate (4–6 mm margin) and PTV (zero‐margin) D95% are scored for each fraction and for the cumulative simulated delivery. Results: Average D95% changes (± 1SD) in the PTV and prostate are −0.5±1.1% and −0.2±0.5%. Maximum per‐fraction D95% changes are −12.7% and −6.4%. 12% and 4% of all fractions suffered a PTV and prostate D95% change in excess of 1 percent. Only 2% and 0.2% of all fractions suffered respective changes in excess of 3%. The patient specific cumulative D95% changes in the PTV and prostate average −0.15±0.2% and 0.07±0.15%. The maximum cumulative D95% variations for a single patient are −0.6% and 0.5%. After the delivery of 5 fractions the cumulative D95% variations for a single patient are −1% and 0.4% for the PTV and prostate. Conclusion: Inter‐fraction prostate motion has little effect on the dosimetric target coverage for step‐and‐shoot prostate plans. Very few fractions (2 and 0.2% for the PTV and prostate) suffered D95% changes in excess of 3%. After the delivery of all fractions the effect on the both the PTV and prostate was negligible.(Supported, in part, by by NIH P01CA116602 and T32CA113277)
SU‐FF‐T‐133: RapidArcTM: Commissioning and Dose Escalation Possibilities
Authors: Crijns W , Depuydt T , Defraene G , Verstraete J , Haustermans K , Budiharto T , Junius S , Van den Heuvel F 
Published: April 2010

Purpose: This paper reports our experience in commissioning RapidArc™ for use in clinical practice. Additionally, we performed a dose escalation planning study using radiobiological parameters to compare the outcome of IMRT and RapidArc plans. Method and Materials: For commissioning we used a standard set of guidelines as outlined by C. Ling et al. This augmented with dosimetry checks, including absolute point measurements in phantom and relative comparisons in air. In addition, we introduced more automated methodologies for picket fence testing of the MLC during RapidArc delivery. Because of different couch systems than presumed in the implementation by the manufacturers a new parameterization of the couch was introduced. In a preliminary dose escalation study of 8 clinical patients we evaluated the treatment plans on a radiobiological basis. Results: For Commissioning: the measurements differed not more than 2% of the predicted values. For Dose Escalation: NTCP calculations for grade 2 rectal bleeding showed a significant reduction (p=0.03) of the mean NTCP from 2.6% to 1.9%, even in this small group of patients. TCP values did not differ significantly (TCP(IMRT)=75.5%, TCP(RA)=75.4%). Conclusion: Methods described in this report lead to successful implementation of RapidArc in clinical practice. At time of presentation we expect to increase the statistics to 25 patients.Conflict of Interest: Research sponsored by Varian Medical Systems, Palo Alto, California, USA
SU‐FF‐T‐273: Energy Dependence of TLD‐100 Chips and Microcubes for the Xoft Axxent® 50 KV Miniature X‐Ray Source and Cs‐137 Relative to Co‐60
Authors: Pike T , Raffi J , Davis S , DeWerd L 
Published: April 2010

Purpose: To use experimental methods to measure the overall energy dependence of LiF:Mg,Ti thermoluminescent dosimeters (TLDs) for the Xoft Axxent® miniature x‐ray source (mean energy ∼27 keV) and 137Cs (662 keV) relative to 60Co (1250 keV), to calculate the absorbed‐dose energy dependence with the Monte Carlo (MC) code MCNP5, and to determine the intrinsic energy dependence of the TLDs by dividing the measured overall energy dependence by the absorbed‐dose energy dependence. Method and Materials: TLDs were irradiated to a known air kerma with all three sources. The air kerma rate of the miniature x‐ray source was measured using an Attix free‐air chamber. Each irradiation was performed for TLDs of two different sizes, microcubes (1 mm3) and chips (3×3×1 mm3). MC simulations were performed for each setup to calculate dose to the TLDs including photon scatter from the holders. MC methods were also used to calculate the air kerma. Results: The overall measured energy response was greater than the MC calculated absorbed‐dose energy dependence for both sources and both chip sizes. The difference between the measured and calculated energy dependence for the miniature x‐ray source was greater than for 137Cs, which means that the intrinsic energy dependence of LiF:Mg,Ti TLD chips and microcubes relative to 60Co is more pronounced at lower energies. Conclusion: This experiment provides further evidence that TLDs have intrinsic energy dependence in addition to the absorbed‐dose energy dependence that can be calculated using Monte Carlo methods. MC corrections alone are not able to calculate the overall energy dependence of TLDs. Therefore, appropriate energy dependence corrections must be measured and applied to TLD measurements when calibration irradiations are performed at a different energy.Conflict of Interest: This research was partially sponsored by Xoft, Inc.
SU‐FF‐T‐322: Geometric Calibration of a Dual Cone Beam CT System with Large Flat Panel Detectors
Authors: Li H , Bowsher J , Giles W , Roper J , Li T , Yin F 
Published: April 2010

Purpose: To assess errors in a simple visual alignment of a dual large‐flat‐panel, cone‐beam‐CT (CBCT) system, and to obtain misalignment parameters that can be incorporated into image reconstruction for accurate target localization in image‐guided radiation therapy (IGRT). Method and Materials: A dual CBCT system with large flat panels has been developed. Two tube‐detector sets are put in the orthogonal position on one optical bench. The designed source‐to‐detector distances (SDDs) and source‐to‐isocenter distances (SIDs) are 150 cm, and 100 cm, respectively. The detectors are 40 × 30cm 194μm‐pixel Varian Paxscan 4030CB flat panels. A ball bearing phantom was scanned with the system. The centroids of the ball bearing projections were measured on both detectors, and geometrical misalignments were calculated firstly for each tube/detector subsystem. Then misalignments between the two subsystems were determined. Results: The effects of out‐of‐plane tilt and skew on the image quality are very limited and have been ignored in our calibration. Calculated in‐plane rotations for both detectors were found to be small. Horizontal and vertical shifts off the detector center were 0.06 and 0.02 cm for subsystem I, and 0.2 and 0.02 cm for subsystem II, respectively. Calculated SDDs and SIDs differed from designed values by 0.5 and 0.2 cm for subsystem I, and 0.2 and 0.5 cm for subsystem II. The vertical shift between the two subsystems was 0.12 cm, and the angle between them was 87.6 degrees. Conclusion: The measurements show misalignments that are sufficient to warrant further mechanical adjustment and/or modeling of misalignment within image reconstruction. Notably the more substantial misalignments include those between the two subsystems.Conflict of Interest: This work is supported in part by Varian Medical Systems and Carestream Health Inc..
SU‐FF‐T‐367: Surface Dose Measurements with OneDose MOSFET System
Authors: Lehmann Joerg , Sydlowski Kristen 
Published: April 2010

The purpose of the study was to evaluate the performance of the MOSFET based OneDose system in comparison with an established TLD system for clinical surface dose measurements for electron and photon irradiation. The impact of an oblique beam angle was investigated for electron beams. Three electron (6, 12, 22MeV) and two photon (6, 20MV) energies have been investigated. For each energy OneDose and TLD detectors were irradiated at reference condition in a solid water phantom and on the surface of the phantom (100 cm SSD). For the electron beams additional surface measurements were performed with an incident beam angle of 30°. Four OneDose detectors and two TLDs were irradiated in each measurement. Three such measurements were performed for each data point. Comparisons were made between OneDose and TLD data as well as with established machine depth dose data. The average standard deviation of the OneDose dose measurements over 13 sets of 12 measurements was 1.8% with higher standard deviations for the photon beam surface measurements (5.7%). Without correction for energy and beam type, which is generically offered by the system, the measured OneDose dose agreed within 2% with the TLD measured data for the photon beams and was 4–7% low for the electron beams. Applying these deviations as corrections for the surface measurements, the OneDose system was found to be in good agreement with the reference data (3%) and the TLD measurements (0–8%). OneDose underestimated the photon surface dose by 22%, TLD by 14%. Changing the beam angle to 30 degrees did not impact the OneDose electron beam surface measurements. The OneDose is fit for use for electron surface patient measurements with applied beam correction factors. Surface measurements for photon beams are more challenging as with TLD.Sicel Technologies provided the OneDose detectors used in this study.
SU‐FF‐T‐447: A Monte Carlo Study for Characterization of Solid Brass Compensators Used for IMRT
Authors: Zhai Y , Stathakis S , Jin X , Papanikolaou N 
Published: April 2010

Purpose: A Monte Carlo study for characterization of solid brass compensators used for IMRT is performed, to investigate their dosimetric properties. Method and Materials: A group various solid brass compensators with different shapes were constructed and simulated by Monte Carlo code EGSnrc (BEAMnrc/DOSXYZnrc). A Varian 2100Ex linear accelerator was commissioned prior to the simulation of the compensators. The simulation included five solid slab brass compensators with thicknesses ranging from 1 to 7cm and solid brass compensators of varying thickness within the field. The same fluences as the ones produced by the compensators were created using Varian Millennium MLC collimator. Phase‐space files were scored after the compensators and after the MLC collimator. The phase space files were used as sources in DOSXYZnrc and the dose was calculated in a solid 30×30×30cm3 water phantom. Dose distribution profiles and PDD were obtained from the dose simulations. Particle fluence, energy fluence, energy spectrum and angular distributions were obtained from the phase space files. Results: Dosimetric data analysis of the PDDs and profiles showed that beam hardening does not have a significant effect on the PDD as it does on the energy spectrum. The PDDs are more penetrating than their open‐field counterparts. Comparing results from MLC‐based IMRT fields and compensators, we find them to be consistently dosimetrically equivalent for all the fields we studied. Conclusion: This study shows that the compensator is an inexpensive and reliable dose delivery device for IMRT and produces an optimized dose profile similar to the ones obtained with the MLC based IMRT delivery.Research sponsored by .decimal Incorporation.
SU‐FF‐T‐484: Late Survival Post Acute Total Body Irradiation in the Rhesus Macaque With Bone Marrow Sparing
Authors: Lerma F , MacVittie T , Farese A , Wang Z , Amin P 
Published: April 2010

Purpose: There are several sequelae consequent to acute high‐dose radiation exposure. The sequelae, in order of occurrence, are the acute radiation syndrome (ARS) composed of the two subsyndromes responsible for early mortality, the hematopoietic and gastrointestinal, followed by delayed effects. The delayed effects expected are pneumonitis and subsequent lung fibrosis and respiratory failure. We investigate these delayed effects in rhesus macaques surviving acute total body irradiation with bone marrow (TBI‐BM) sparing at 11.5 to 12 Gy. Method and Materials: A varian 21EX linear accelerator is used to irradiate non‐human primates (NHP) at 153 SSD using a 40 × 40 cm field size at isocenter. The irradiation takes place at approximately 80 cGy / min at midplane. The fields are in the AP and PA directions and sparing of the primates is achieved from the knee cap down. CT imaging is conducted at intervals of 30 days to evaluate the gut and lungs. Results: Three survivors are obtained from a cohort of 16 NHP undergoing TBI‐BM at 11.5–12.0 Gy, in a single exposure. CT scans are evaluated for defects in the gut and lung at 30 day intervals, showing radiographical evidence of a late GI syndrome, pleural effusion, ascites and pneumonitis. The pleural effusion and ascites are associated with pericardial irradiation. Conclusion: These result confirm that sufficient active bone marrow sparing drastically improves long term survival at doses greater than 7.5 Gy. Notably, the longest surviving NHP in this cohort has presented with ascites and pleural effusion that have led to cause of death at day 100. This result confirms an important late effect, pericardial injury as a possible cause of death in late survivors that may override other lung‐injury associated mortality.This work supported by NIAID Contract ♯ HHSN266200500043C
MO‐B‐BRC‐01: Shielding Design for Linear Accelerators Using NCRP Report 151
Authors: Martin M 
Published: April 2010

The application of the structural shielding design techniques and goals as outlined in NCRP Report 147: Structural Shielding Design for Medical X‐ray Imaging Facilities (November 2004) and NCRP Report 151: Structural Shielding Design and Evaluation for Megavoltage X‐ and Gamma‐Ray Radiotherapy Facilities will be the basis for this practical course. Actual facility designs will be used as the example calculations of required shielding for Linear Accelerators to be installed in modern radiation therapy facilities. Examples of methods to minimize the amount of additional shielding needed for new departments due to well planned designs will be given.As the equipment in radiation oncology departments has evolved to linear accelerators with IMRT as state of the art modalities, the requirements for adequate radiation shielding for these modalities has become more rigorous. Architectural designs no longer depend on standard maze design rectangular rooms. Innovative layouts and utilization of multiple layers of shielding materials allow much greater flexibility in room designs. Shielding calculations for these challenging designs will be covered in this presentation.Learning Objectives:1. Understand the workload and occupancy factors to be used for dual energy linear accelerators with IMRT capabilities to determine required structural shielding to meet exposure limits for occupational personnel and the public.2. Understand the effectiveness of existing and additional structural shielding materials to provide radiation protection and methods to calculate the required amounts of these materials.3. Understand the calculation methods to be used in performing the shielding calculations for all aspects of linear accelerator installations to insure adequate shielding is provided to meet applicable state and ALARA requirements.