bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐167: Estimation of Effective Dose from a Single KV Imager for Real‐Time Intrafraction Tumor Position Monitoring
Authors: Ng J , Poulsen P , Kuncic Z , Keall P 
Published: November 2011

Purpose: A novel kV guidance method has been proposed in which the tumor position is continuously measured during IMRT and arc therapy by a single kV imager. Adding kV imaging during therapy adds radiation dose. We quantify the dose delivered and compare it to other imaging doses. Methods: The software PCXMC2.0 was used to calculate effective dose delivered to a mathematical human phantom. The Varian OBI system was simulated. The beam axis was set to intersect the geometric center of the prostate. Tube voltage and mAs settings were fixed. The imager angle, field size, height and mass (statistics from ten countries) of the phantom were varied. For different treatment scenarios, the effective dose was averaged over all angles to obtain an average angular effective dose. The field size was fixed to the minimum area sufficient to cover all markers and the average effective dose was obtained by weighting all the countries by their populations. This average effective dose per projection was used to calculate the effective dose based on treatment technique, fractionation and imaging frequency. The dose was compared to the Navotek radioactive fiducial and CBCT. Results: Effective dose varied with imager angle. For a 6cm×6cm field, the highest average angular dose per projection is 1.2 microSv (India), while the lowest is 0.6 microSv (Germany). The average dose weighted by population is 0.9 microSv. The effective dose increases linearly with field size, imaging frequency and treatment duration but decreases with height or mass. A 15 minute single fraction IMRT treatment delivers 0.84 mSv at 1 Hz. For comparison, a pre‐treatment CBCT pelvic scan delivers 4.3 mSv while the Navotek radioactive fiducial delivers 64 mSv of lifetime dose. Conclusion: Intrafraction kV guidance for tumor tracking gives less than 1mSv imaging dose with reasonable settings. This is lower than Navotek and CBCT.Conflict of interest: Supported by NCI R01 CA93626.
SU‐E‐T‐15: GEANT4 Microdosimetry for Simulation of Dose Enhancement in Vivo at Orthovoltage Energy
Authors: Ackerman N , Graves E , Bazalova M 
Published: November 2011

Purpose: This study simulates at the cellular scale the microscopic dose enhancement from high Z materials (such as gold nanoparticles) in tissue as a function of concentration and intracellular localization. Methods: Monte Carlo (MC) simulations were performed using Geant4 9.3p02 for a simple 3D geometry of 125 cubic cells with centered nuclei. Contrast materials of gold, iodine, and tungsten were simulated in a 150 kVp beam. The extra‐ and intra‐cellular contrast concentration was varied, and internal cellular contrast was placed either throughout the cytoplasm or in localized vesicles. Results: The enhancement factor for the nucleus is well described by a linear function of tissue contrast, regardless of whether the enhancement agent was contained in vesicles or throughout the cytoplasm. The predicted enhancement is smaller than previous simulations using macroscopic methods and is smaller than measured values. Conclusions: Cellular scale simulations show that macroscopic simulations overestimate the enhancement seen in the nucleus, but that intermediate energy secondaries interacting in the nucleus would not provide the enhancement measured experimentally.N. Ackerman is supported by a Weiland Family Fellowship
SU‐E‐T‐126: Analysis of Uncertainties for the RPC Remote Dosimetry Using Optically Stimulated Light Dosimetry (OSDL)
Authors: Aguirre J , Alvarez P , Ibbott G , Followill D 
Published: November 2011

Purpose: Determine the uncertainty of the Radiological Physics Centerˈs (RPC) remote audit dose measurement of photon and electron beam outputs using Optically Stimulated Luminescence Dosimeters (OSLD). Methods: In June 2010 the RPC implemented a switch from TLD to an OSLD mailed dosimetry audit using Landauerˈs InLight nanoDot™ OSL dosimeters and microStar reader System™. The steps and factors for the calculation of dose with OSLD were designed to follow those already in use with TLD including the use of the same acrylic mini‐phantoms and irradiation instructions. The OSLD sensitivity was referenced to Co‐60, and corrections for linearity, individual dosimeter response, fading, use of mini‐phantoms and energy were determined for the OSLD. An analysis of the uncertainty of each of the correction factors was determined to give an overall uncertainty of the OSLD dose measurement under Co‐60 reference conditions and megavoltage beam audits. Results: The expectation was that with the physical processes for OSLD, being so closely resembling those of TLD, the uncertainties of OSLD would be comparable to those of TLD. A combined uncertainty of 0.8% for irradiations with Co‐60 under controlled reference conditions and 1.8% for irradiations with high‐energy X‐rays was determined as compared to 1% and 2% for the previously used TLD, respectively. The OSLD energy block correction factor (KE) is the primary source of the overall OSLD dose measurement uncertainty. To date, the OSLD audit results after a year are essentially identical to the previous 5 years of TLD results both showing a mean TLD/Inst. Ratio of 1.00 ± 0.018.Conclusion: The uncertainty of the RPCˈs new OSLD remote dosimetry audit programˈs dose measurement is equal to if not less than that for the historical TLD program.Work supported by PHS CA010953, awarded by NCI, DHHS.
SU‐E‐T‐153: Proton Linearity and Energy Dependence Studies of Optically Stimulated Luminescent Detectors for Remote Audits of Proton Beam Calibrations by the Radiological Physics Center
Authors: Cho J , Alvarez P , Followill D , Gillin M , Ibbott G 
Published: November 2011

Purpose: Implement Optically Stimulated Luminescent Detectors (OSLD) into Radiological Physics Centerˈs (RPC) remote audit quality assurance (QA) program for protons. Methods: The OSLDs were aluminum oxide (Al2O3:C) nanoDots™ from Landauer, Inc. (Glenwood, IL.). A standard RPC remote audit electron phantom with detector inserts at two different locations with three scatter rings and slabs of water equivalent plastic phantom, added on top of the phantom to place both dosimeter locations within the SOBP, were used. Two nanoDots™ were placed in each detector insert of the phantom. For the linearity study, a 250 MeV proton beam with reference setup (FS = 10 × 10 cm2, 10cm SOBP) was used with the beam isocenter located between the two detector depths. Doses of 25, 50, 100, 200, 300, 350 cGy at isocenter were delivered. For the energy dependence study, doses of 200 cGy each were delivered with the reference setup for 250, 200, and 160 MeV proton beams. Co‐60 measurement was performed as a standardization process. The OSLDs were read on a MicroStar reader from Landauer between 5 to 7 days after irradiation. Results: The OSLD irradiated had a linear dose response of y=−8.3513E−5x+1.0084 with an R2 = 1.000 over the dose range where y=Kl (dose linearity factor) and x=dose. The energy dependence of the OSLD for the three different energies was less than 3% for the irradiation conditions and fluctuation for different OSLDs less than 1% for the same energy used for the RPC remote audit program. Conclusions: The OSLD showed a linear dose response and consistent energy dependence for three proton energies at the MD Anderson Cancer Center Proton Center. OSLD can be used to replace the TLD for RPCˈs remote audit QA program for proton beam output.Work supported by PHS CA0 10953 and CA081647 awarded by NCI, DHHS
SU‐E‐T‐155: Evaluation of An in Vivo Device for Daily Patient Treatment Delivery Measurements Using a Varian Linear Accelerator
Authors: Buckey C , Myers P , Esquivel C , Mihailidis D , Mavroidis P , Gutiérrez A , Papanikolaou N , Stathakis S 
Published: November 2011

Purpose: A clinical evaluation of a commercially available dosimetric device for in‐vivo monitoring of IMRT and VMAT treatments. Methods: The Device for Advanced Verification of IMRT Deliveries (DAVID) system (PTW, Freiburg, Germany) is a transparent multi‐wire harp chamber that can slide into the wedge slot of a Varian linear accelerator. Its 40 measurement wires correspond to the positions of the leaf pairs of a Millennium‐80 MLC, with a projected spacing at isocenter of 5 mm. The DAVID was inserted into the beam during deliveries of clinically approved IMRT and VMAT treatments. The ability of the DAVID to detect errors in MLC positions was tested by introducing small errors into the plans. The reproducibility of measurements was tested for several disease sites over a series of deliveries. Results: The reproducibility of IMRT and VMAT plans is good. The maximum deviation of any one leaf among all plans and all deliveries was 3.11% (IMRT) and −2.09% (VMAT). The maximum total deviation among all plans and all deliveries was 3.41% (IMRT) and −1.99% (VMAT). The average total deviation among all plans and all deliveries for IMRT was 1.35% ± 1.06% and for VMAT was 0.40% ± 1.35%. When intentional errors were introduced, the DAVID could consistently detect leaf position errors when the resulting gap differed from the plan by great than or equal to 1 mm. Conclusions: The DAVID system is a useful, reliable tool for daily in‐vivo monitoring of patient treatments. It is capable of detecting errors as small as 1 mm, and requires no additional time or effort by the treatment staff for data collection. The DAVID system can provide assurance that every fraction of an IMRT or VMAT treatment is being executed as planned.This work partially supported by PTW (Freiburg, Germany).
SU‐E‐T‐173: Design, Development, and Evaluation of a Modified, Anthropomorphic, Head and Neck, Quality Assurance Phantom for Use in Stereotactic Radiosurgery
Authors: Faught A , Kry S , Luo D , Molineu A , Galvin J , Drzymala R , Timmerman R , Sheehan J , Gillin M , Ibbott G , Followill D 
Published: November 2011

Purpose: To design, construct, and evaluate a modified anthropomorphic head phantom for evaluation of stereotactic radiosurgery (SRS) dose planning and delivery, for protocols developed by NCI funded cooperative groups. Methods: A phantom was constructed from a water equivalent, plastic, head‐shaped shell. Modifications from an original phantom design containing only a spherical target included the addition of structures resembling a nonspherical target (pituitary) and an adjacent (within 2mm) organ at risk (OAR) (optic chiasm) simulating structures encountered when treating acromegaly. A separate insert for treatment delivery contained two thermoluminescent dosimeters (TLD) for absolute dosimetry and radiochromic film in the sagittal and coronal planes for relative dosimetry. The target and OAR proximity provided a more realistic treatment planning and dose delivery exercise than the original design. To create an achievable planning criterion, the volume of the OAR receiving &#8805;8Gy was limited to 10%. The rigor of the treatment planning process, reproducibility of the dosimeters, and agreement with calculated doses were assessed through three GammaKnife irradiations. Results: The TLD results from the three irradiations agreed with the calculated target dose to within 4.3% with a coefficient of variation of 2.0%. Gamma analysis in the film planes showed an average passing rate of 99.9% and 99% using 5%/3mm distance to agreement criteria in the coronal and sagittal planes, respectively. A gamma analysis using 3%/2mm criteria showed the percent of total pixels passing to be 87% and 79% respectively. Conclusions: A modified anthropomorphic SRS phantom has been designed that provides a more realistic clinical planning and delivery challenge that can be used to credential institutions wanting to participate in NCI funded clinical trials.Work supported by PHS CA010953, CA081647 and CA21661 awarded by NCI. DHHS
SU‐E‐T‐175: 3D Dose Verification of Varian RapidArc Treatment Plans by BANG Polymer Gel Dosimetry
Authors: Watanabe Y , Malmin R , Hayashi N 
Published: November 2011

Purpose: To verify 3D dose distributions predicted by Eclipse treatment planning software (with AAA version 8.2.23) with those measured by polymer gel dosimeters for RapidArc intensity modulated arc radiation therapy. Methods: Treatment plans were created for RapidArc therapy of two prostate cancer patients. The daily fraction size was 180 cGy for both plans (R and E). The treatments used 10MV photon beams from a Varian iX linear accelerator. Two cylindrical phantoms (15 cm diameter and 15 cm long) containing BANG3‐PRO polymer gel were used. For dosimetric verification, QA plans were created using the CT images of the polymer gel phantom, which were obtained using 3‐mm thick slices. The phantoms were irradiated using the dose delivery techniques identical to those used for the patient treatments. After irradiation, the phantoms were scanned using a 32 spin‐echo technique with a 3T MRI scanner. The major imaging parameters were as follows: 1 mm × 1mm pixels, 45 2‐mm thick slices, and the echo spacing of 13.6 ms. The MRI images were processed to obtain 3D dose distributions using in‐house MATLAB programs. 3D dose distributions of measurements and calculations were compared using gamma index (3 % and 3 mm criteria), dose volume and dose difference diagrams, line dose profiles, and planer dose distributions. Results: Mean percentage differences between the measured and calculated doses in the 3D volumes containing PTVs were −3.1±11.9 % and 1.6±9.8 % for Plans R and E, respectively. The passing rates of the gamma index analyses were 90% and 84% for doses greater than 80% of the maximum doses of those plans. Conclusions: The current study has demonstrated a potential usefulness of polymer gel dosimetry for 3D dose verification of RapidArc plans. However, the agreement of measured and calculated doses was not satisfactory. The causes of the disagreements need to be investigated.Japanese Society of Radiological Technology
SU‐E‐T‐193: EPID IMRT QA for Brain, and Head‐Neck Treatment Plans in Radiation Therapy
Authors: Vazquez‐Quino L , Fitzpatrick M , Chen X , Alkhatib H , Mavroidis P , Papanikolaou N 
Published: November 2011

Purpose: Since amorphous‐silicon electronic portal imaging devices (EPIDs) availability the interest for radiation dosimetry use increases. In clinical quality assurance (QA) program, EPIDs has the potential to be used to verify IMRT plans in radiation therapy. The present study purpose is to test the use of an EPID phantom‐less method in clinical applications for IMRT. Methods: EPID images were acquired using a aS1000 EPID in the integrated mode, 6 MV beam, 600 MU/min dose rate (IMRT) . Signal intensity of EPID images were converted to dose map using a calibrated linear signal‐dose relationship. An EPID‐based QA system was designed, which includes IMRT Quality Assurance (QA). For IMRT and VMAT QA, a phantom‐less method was proposed, which used fluence maps reconstructed from EPID‐measured fluences as input to treatment plan system for dose calculation and comparison Results: Comparison of the calculated dose using EPID‐measured fluence to the plan dose for IMRT to a point and plane dose calculated by the TPS and measured by Ion Chamber were made for 16 patient specific QA plans. The EPID‐based IMRT method was able to verify the treatment plan and capture the reasonable plan‐versus‐QA comparison with a gamma analysis (3% maximum dose, 3mm) resulting in >99 % of points with a gamma <1 . EPID‐based QA dose matches well to the plan dose with similar contours. Point dose between EPID and Ion chamber measurements for IMRT plans were in average 2.24% for 16 plans including brain and Head/Neck cases. Conclusions: The results show that EPID may be properly used as a tool for clinical QA tasks and the developed EPID‐based QA system may be used for IMRT patient specific QA. Our method for EPID IMRT QA indicates the feasibility to use EPID measurements for daily patient QA verification.Potential for Conflict of Interest: Research sponsored by Oncology Data Systems, Inc, Oklahoma City, OK
SU‐E‐T‐204: Real‐Time Monitoring of Age‐Related Macular Degeneration Radiosurgery Using Plastic Scintillation Dosimetry
Authors: Tien C , Cantley J , Hintenlang D , Bolch W , Firpo M , Chell E 
Published: November 2011

Purpose: Age‐related macular degeneration (AMD) is the leading cause of vision loss and blindness among those over age 65. In its wet form, blood vessels grow from the choroid, causing macular tension and sometimes retinal displacement. As an alternative to monthly direct‐injection methods, Oraya Therapeutics has developed the IRayTM stereotactic radiosurgery device. This table‐top system has been validated in Monte Carlo simulations, human cadaver eye studies, pre‐clinical animal studies, and a phase 1 clinical trial. A plastic scintillation dosimetry (PSD) system was developed to monitor dose delivery in real‐time and provide measurement of total dose delivered. Methods: The IRayTM uses 100 keV x‐rays to deliver 24 Gy of macular dose, divided into three positions along the inferior pars plana. The PSDˈs small volume (0.5 mm diameter and 2 mm height), allows placement within the machine head. The PSD is fiber‐optically coupled to a photomultiplier tube via a plastic waveguide. Before direct characterization of the IRayTM, the preliminary PSD performance was tested using a portable x‐ray unit, mobile c‐arm fluoroscopy unit, and an ion chamber. Results: In order to avoid buffering issues, real‐time measurements used 250 ms bins, but can be adjustable to 10 ms. A calibration factor (CF) from PSD percent‐depth‐dose to ion chamber percent‐depth‐dose was 1.06 at a depth of 1.5 cm in solid water, the typical macular target depth. Counts‐to‐exposure CF varied less than 1% from 0.862 to 15.26R. Counts‐to‐exposure CF remained linear with R2 of 0.999 up to 16R even with varying dose rate (.002 R/s to 1.0 R/s). Conclusions: The PSD demonstrated linear dose measurements even at high dose and high dose rates. This study demonstrates the feasibility, accuracy, and precision of a PSD for clinical implantation in the IRayTM, a device for treatment of AMD.This research was supported by a grant from Oraya Therapeutics, Inc.
SU‐E‐T‐226: Image Acquisition and Processing Characteristics of a Siemens EPID: Potential Problems for EPID Dosimetry
Authors: Deshpande S , Vial P , Holloway L , Metcalfe P 
Published: November 2011

Purpose: To investigate the behavior of the imaging control software on a Siemens EPID and the resulting impact on EPID based IMRT dosimetry Method and Materials:Four ‘simple’ and four ‘clinical’ IMRT fields were created. Each segment of the ‘simple’ field had a constant field size of 10 × 10 cm2. The ‘simple’ fields had 2, 4, 5, and 10 segments with 10, 5, 4, and 2 MU per segment respectively. The ‘clinical’ fields all consisted of 20 segments with constant MU per segment of 2, 4, 5, and 10 MU. The fields were measured simultaneously with a Siemens EPID and ImRT MatriXX ionisation chamber array (iba) by placing the MatriXX beneath EPID. The integrated EPID dose response was determined from the frame average pixel value multiplied by the reported number of frames. Reproducibility of central axis response, beam profiles, and pixel‐by‐pixel response (2D) was compared from 10 repeat measurements. Results: The percentage standard deviation of the integrated EPID response for the ‘simple’ case was within 1% for the 2 and 10 MU per segment fields but more than 10% for the 4 and 5 MU per segment fields. EPID crossplane profiles also yielded large variations in amplitude and shape for the 4 and 5 MU per segment cases only. No such variations were observed by concurrent MatriXX measurements. A similar but less obvious trend was observed for the ‘clinical’ case. In both cases the number of frames per segment reported for the 2 MU and 10 MU per segment fields remained constant. The number of frames reported for the 4 MU and 5 MU per segment fields varied and appeared unreliable. Conclusions: EPID images of IMRT fields displayed large variations in reproducibility depending on the MU per segment. Poor reproducibility correlated with inconsistent reporting of the number of frames.Cancer Institute NSW Research Equipment Grant 10/REG/1‐20
SU‐E‐T‐280: DSA as the Primary Image Modality in Frameless SRS for Treatment of Arteriovenous Malformations
Authors: Lu X‐Q , Mathiowitz G , Lin P 
Published: November 2011

Purpose: Stereotactic radiosurgery (SRS) is an effective alternative to microsurgical resection or embolization for arteriorvenous malformations (AVMs). Digital Subtraction Angiography (DSA) is the gold standard for diagnosis and characterization of vascular anatomy, but it requires a frame attached to the skull. Proton and the new image‐guided LINAC SRS systems are frameless. These frameless systems represent a major progress in radiotherapy — however, they prevent the usage of DSA. Without DSA as the primary image, the outcome may be less‐than‐optimal and sometimes even impossible to treat. This study intends to solve the problem. Methods: The solution is based on a conceptual breakthrough whereby, in contrast to the previous practice where a localizer was fixed to the skull during angiography, the patient can now be angiographed under standard clinical conditions without frame and localizer, while a newly‐designed localizer box is radiographed separately. Based on several fiducials implanted into the skull, a target volume on DSA can be transferred to the localizer system in 3D, then further transferred to contours in multi‐CT slices. Combined with other imaging modalities, a treatment can be planned and executed by a routine frameless SRS. Results: Phantom tests demonstrated that the uncertainty in transferring a point target to the localizer is less than 0.3 mm. The maximum transformation errors from the localizer to CT system are ∼0.3 mm. The overall uncertainty of placing a point target to CT is 0.4 mm. For volume targets the volume determined is accurate within < 6%. The algorithm and software are robust and accurate. The method has been successfully applied clinically. Conclusions: A new reliable method for frameless Stereotactic Radiosurgery has been developed, which allows using DSA as the primary imaging in AVM treatment. Implanted fiducials are required for the time being, but using non‐implanted fiducials is feasible.This work is partially supported by the JCRT Foundation.