bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐T‐141: Dosimetry and Error Analysis of HDR Brachytherapy Tandem Applicator Using A16 Microchamber and Monte Carlo Simulation
Authors: Amoush A
Published: June 2012

Purpose: Absolute dosimetry with the associated uncertainties for 192Ir High Dose Rate (HDR) Brachytherapy Tandem applicator are presented using A16 microchamber and Monte Carlo simulation. The results are compared to the TG‐43 protocol. Methods: An A16 Exradin MicroChamber, MCNPX 2.6 Monte Carlo simulation code and PTW farmer chamber with an ADCL calibration coefficient were used in this work. The A16 microchamber was calibrated using MCNPX simulation and PTW farmer chamber. Statistical and systematic uncertainty analyses associated with each experimental technique were analyzed quantitatively using MCNPX 2.6 to evaluate source positional error, Tandem positional error, phantom size effect, volume averaging, stem and wall effects, and Tandem effect. Results: A16 microchamber was calibrated according to the AAPM TG‐21 protocol and resulted in a value of 3.21E+09 Gy/C for Ngas in 60CO. To use the A16 with 192Ir spectrum, a correction factor of 1.13 was generated along the source transverse axis using MCNPX to account for energy difference. Absolute dose and uncertainty analyses along the transverse axis of a Tandem applicator were calculated using MCNPX and A16 microchamber and compared to the TG‐43 protocol. The generated overall uncertainties associated with the A16 microchamber are 22%, 17%, 15%, 15%, 16%, 17%, and 19% at 1cm, 2cm, 3cm, 4cm, and 5cm, respectively. Conclusions: In this work, the author investigated the absolute dosimetry for 192Ir HDR brachytherapy for a Tandem applicator using A16 microchamber and compared the results to the TG‐43 protocol. A16 microchamber has an effective volume of 0.007cc which makes it suitable to measure extremely small field sizes and enables high spatial resolution while minimizing volume averaging near the source. Furthermore, the author also investigated and analyzed the systematic and statistical uncertainties associated with A16 experimental dosimetry as recommended by AAPM TG‐138 and GEC‐ESTRO. Based on this work, dosimetry of HDR brachytherapy using A16 microchamber can be used, within uncertainties, as an alternative or redundant for the LiF TLDs.
SU‐E‐T‐145: MRI Gel Dosimetry Applied to Dose Profile Determination for 50kV X‐Ray Tube
Authors: Schwarcke M , Marques T , Nicolucci P , Filho O Baffa
Published: June 2012

Purpose: The aim of this study was to use MRI gel dosimetry to determine the dose profile of 50kV MAGNUM® X‐ray tube, MOXTEK Inc., in order to calibrate small solid dosimeters of alanine, tooth enamel and LiF‐TLDs, commonly used in clinical quality assurance and datation dosimetry. Methods: MAGIC‐f polymer gel was kept in two plastic containers of 100mL, avoiding attenuation of the primary beam trough the wall. Beam aberture of 3mm and dose rate of 16.5Gy/min were set, reproducing irradiation conditions of interest. The dose rate was assumed based on data of the vendor information of the tube and dose of 30Gy was delivered at the surface of the gel. MAGIC‐f gel was irradiated at source‐surface distances(SSD) of 0.1cm and 1.0cm. After 24hours of irradiation, gel was scanned in an Achieva® 3T Philips® MRI tomography using relaxometry sequence with 32 Echos, Time‐to‐Echo(TE) of 15.0ms, Time‐to‐Repetition(TR) of 6000ms and Field‐of‐View(FOV) of 0.5×0.5×2.0mm. Dose map at the central plain of irradiation was calculated from T2 relaxometry map. Results: The gel dosimetry results evidenced a build‐up depth of 0.13cm for SSD=0.1cm and no build‐up was detected for SSD=1.0cm. However, the dose profile evidenced high gradient of dose in SSD=0.1, decreasing the dose from 100% to 30% in 1.4cm depth inside the gel; In turn, the dose distribution is homogeneous after 0.4cm deth for SSD=1.0cm. Conclusions: MRI gel dosimetry using MAGIC‐f presented as feasible technique to determine dose profiles for kilovoltage x‐rays tubes. The results evidenced that the calibration of small solid dosimeters can be performed using SSD of 1.0cm in the 50kV MAGNUM® X‐ray tube using 0.4cm/g/cm3 filter. This work was funded supported by CNPQ, CAPES and FAPESP.
SU‐E‐T‐150: The Basic Dosimetric Properties of NIPAM Polymer Gel Dosimeter
Authors: Pak F , Farajollahi A , Miabi Z
Published: June 2012

Purpose: To asses a series of basic dosimetric properties such as reproducibility, linearity, tissue equivalency, dose rate and energy independency for NIPAM polymer gel dosimeter. Methods: The NIPAM gel was manufactured according to the method, described by senden et al (2006). The gels were irradiated approximately 2 h after manufacturing and MR images of the gel were made 24 h after irradiation. Transverse relaxation rates (R2=T2?1) were obtained from the signal decay data using the proper data analyzer. In order to investigate the absorbed dose response reproducibility, the experiment was repeated three times using the same batch of monomer, irradiation method, scanning parameters and conditions, also with analyzing two set of the gel with different batches of chemical the effect of different batches were investigated . For assessing if the NIPAM gel dosimeter response is dependent on different photon energies, two sets of NIPAM gel were irradiated using a 9 MV linear accelerator and a 60co. The effect of different dose rate on gel response was studied in SSD of 80, 90, 100, 110 and 120 and radiation beam were calibrated to give 5Gy in each SSD. To investigate the linearity of the gel, the vials were irradiated from 1 to 35 Gy. In order to verify tissue equivalency, effective atomic number and relative electron density of NIPAM dosimeter were calculated using CT number, and compared with tissue. Results: This polymer gel found to be tissue equivalent. The results showed that the dose response of NIPAM polymer gel is highly reproducible in same and different batches of chemical and its response was linear up to 26 Gy. Energy and dose rate had no effect on NIPAM gel response. Conclusions: NIPAM gel dosimeter appears to be a promising dosimeter in all aspects of dosimetric properties which were assessed in this study.
SU‐E‐T‐152: Development of a Phantom for Commissioning and Patient Specific QA for Volumetric Modulated Arc Therapy (VMAT)
Authors: Holla R , Pillai B
Published: June 2012

Purpose: To design a cost effective phantom for commissioning tests and patient specific quality assurance in VMAT techniqueMethods: The phantom is made of PMMA with the physical density of 1.18 gm/cc. It consists of 20 numbers of 20cm diameter discs connected together in a horizontal stack, making a cylinder of length 20cm. The centers of the discs are drilled with 2.1cm hole which accommodates chamber sleeve of near 2.1cm diameter, which is made of Delrin with the physical density of 1.414gm/cc. The cylindrical geometry of the phantom is ideal for rotational therapy QA like VMAT or Rapid arc. The entire phantom is self supporting and hence no supporting bar or holders are in the path of beam geometry. The chamber sleeve itself acts as the supporting rod for these discs and it can be inserted in to the disc assembly from distance of−9cm to +10cm from the origin and hence any axial point from −9cm to +10cm with respect to isocenter can be used for point dose measurement. The other side of the chamber sleeve is filled by spacer rod for sustaining the discs in place. The films can be inserted, transversely in any XZ plane from −9cm to +10cm from the origin between the discs next to the chamber center. Results: Simultaneous irradiation for the chamber and the film is done for VMAT plans without collapsing the gantry angles to nominal angle of zero. Evaluated the results using RIT film analysis software for gamma index of 3%, 3mm. Good agreement is found with more than 95% of pixels passing 3% 3mm criteria. The point dose verification showed less than 3% variation with TPS planned dose. Conclusions: Most of the commercial QA systems needs gantry to be collapsed to zero degree to perform QA for modern RT techniques. Especially for techniques like VMAT, collapsing gantry to zero will fail to validate the influence of gantry speed on dose delivery
SU‐E‐T‐164: Clinical Implementation of ASi EPID Panels for QA of IMRT/VMAT Plans
Authors: Hosier K , Wu C , Beck K , Radevic M , Asche D , Bareng J , Kroner A , Lehmann J , Logsdon M , Dutton S , Rosenthal S
Published: June 2012

Purpose: To investigate various issues for clinical implementation of aSi EPID panels for IMRT/VMAT QA. Methods: Six linacs are used in our clinic for EPID‐based plan QA; two Varian Truebeams, two Varian 2100 series, two Elekta Infiniti series. Multiple corrections must be accounted for in the calibration of each panel for dosimetric use. Varian aSi panels are calibrated with standard dark field, flood field, and 40×40 diagonal profile for beam profile correction. Additional corrections to account for off‐axis and support arm backscatter are needed for larger field sizes. Since Elekta iViewGT system does not export gantry angle with images, a third‐party inclinometer must be physically mounted to back of linac gantry and synchronized with data acquisition via iViewGT PC clock. A T/2 offset correctly correlates image and gantry angle for arc plans due to iView image time stamp at the end of data acquisition for each image. For both Varian and Elekta panels, a 5 MU 10×10 calibration field is used to account for the nonlinear MU to dose response at higher energies. Acquired EPID images are deconvolved via a high pass filter in Fourier space and resultant fluence maps are used to reconstruct a 3D dose ‘delivered’ to patient using DosimetryCheck. Results are compared to patient 3D dose computed by TPS using a 3D‐gamma analysis. Results: 120 IMRT and 100 VMAT cases are reported. Two 3D gamma quantities (Gamma(V10) and Gamma(PTV)) are proposed for evaluating QA results. The Gamma(PTV) is sensitive to MLC offsets while Gamma(V10) is sensitive to gantry rotations. When a 3mm/3% criteria and 90% or higher 3D gamma pass rate is used, all IMRT and 90% of VMAT QA pass QA. Conclusions: After appropriate calibration of aSi panels and setup of image acquisition systems, EPID based 3D dose reconstruction method is found clinically feasible.
SU‐E‐T‐167: Comprehensive Evaluation of EPID Image Acquisition for Integrating and Temporal Dosimetry of Fixed‐Gantry IMRT and ArcIMRT
Authors: Yeo I , Jung J , Yi B , Patyal B
Published: June 2012

Purpose: To evaluate EPID for dosimetry applications of arc and static‐gantry IMRT with sliding window (SW) and/or step‐and‐shoot (SS) deliveries Methods: IMRT beams (SW & SS) were designed that generate beam hold‐offs and dose rate modulation due to MLC motion under 10 × 10 cm jaw. An arcIMRT beam was designed by adding gantry movement to the SW field. A 10 cm × 10 cm open beam was also used. Despite differences in delivered dose rates/pulse characteristics, the four beams should deliver the same total dose. For each beam, various MUs with 6 MV beam at 300MU/min were irradiated on EPID which operated in image acquisition of integration mode (IM), continuous scanning mode with synchronization (CMs) and without (CMn) to beam pulses. Acquired images were evaluated in repeatability, dose linearity, and reproducibility (reproduce open beam output in IM). Results: In IM, repeatability, dose linearity, and reproducibility were within 1% for all dose levels and beams. In CMs, they were within 1–2% if dose rate was maintained steady (1) for SW beam (needed a minimum 1.3 MU/cm MLC motion) and (2) arcIMRT beam (needed a minimum 1 MU/degree and 2.8 MU/cm MLC motion) and (3) if a minimum of 38‐40 MU per shoot was used for SS beam. Nonlinearity was observed for fewer MUs. This is due to the response of EPID to pulse‐length reduction for fixed‐gantry therapy and pulse dropping for arc therapy. The latter produces in‐planar non‐uniformity making EPID unsuitable for temporal dosimetry of arcIMRT. Sacrifice in temporal resolution then became necessary such as multi‐frames per image (eg. ∼1 sec/image). In CMn the results were similar to those of CMs. However, they showed artifacts, thus this mode was not preferred. Conclusions: We found conditions under which integrating and temporal EPID dosimetry can be used for IMRT and arcIMRT dose deliveries.
SU‐E‐T‐169: Initial Investigation into the Use of Optically Stimulated Luminescent Dosimeters (OSLDs) for In‐Vivo Dosimetry of TBI Patients
Authors: Paloor S , Aland T , Mathew J , Al‐Hammadi N , Hammoud R
Published: June 2012

Purpose: To report on an initial investigation into the use of optically stimulated luminescent dosimeters (OSLDs) for in‐vivo dosimetry for total body irradiation (TBI) treatments. Specifically, we report on the determination of angular dependence, sensitivity correction factors and the dose calibration factors. Methods: The OSLD investigated in our work was InLight/OSL nanoDot dosimeters (Landauer Inc.). Nanodots are 5 mm diameter, 0.2 mm thick disk‐shaped Carbon‐doped Al2O3, and were read using a Landauer InLight microstar reader and associated software.OSLDs were irradiated under two setup conditions: a) typical clinical reference conditions (95cm SSD, 5cm depth in solid water, 10×10 cm field size), and b) TBI conditions (520cm SSD, 5cm depth in solid water, 40×40 cm field size,). The angular dependence was checked for angles ranging ±60 degree from normal incidence. In order to directly compare the sensitivity correction factors, a common dose was delivered to the OSLDs for the two setups. Pre‐ and post‐irradiation readings were acquired. OSLDs were optically annealed under various techniques (1) by keeping over a film view box, (2) Using multiple scan on a flat bed optical scanner and (3) Using natural room light. Results: Under reference conditions, the calculated sensitivity correction factors of the OSLDs had a SD of 2.2% and a range of 5%. Under TBI conditions, the SD increased to 3.4% and the range to 6.0%. The variation in sensitivity correction factors between individual OSLDs across the two measurement conditions was up to 10.3%. Angular dependence of less than 1% is observed. The best bleaching method we found is to keep OSLDs for more than 3 hours on a film viewer which will reduce normalized response to less than 1%. Conclusions: In order to obtain the most accurate results when using OSLDs for in‐vivo dosimetry for TBI treatments, sensitivity correction factors and dose calibration factors should all be determined under clinical TBI conditions.
SU‐E‐T‐170: A Viable Approach to Patient Specific QA for Spine VMAT SRS Using EPID‐Based Dosimetry
Authors: Song Y , Zhang P , Li J , Burman C , Chan M
Published: June 2012

Purpose: VMAT involves multi‐parameter modulations, thus presenting multi‐dimensional challenges. Here, we present a viable approach to VMAT patient specific QA using EPID‐based dosimetry for spine VMAT SRS casesMethods: Our spine VMAT SRS plans consisted of two full arcs and were optimized with 6 MV photons for a Varian Trilogy LINAC. The QA plans were computed by resetting all control points to 0° gantry angle while keeping the MLC apertures and corresponding MU weights intact. The dose distribution at the depth of clinical significance was calculated in a solid water phantom. EPIDose (Sun Nuclear Corp) was used to convert MV EPID images into absolute dose in a plane of interest in a homogeneous medium. During measurements, the source‐to‐detector distance (SDD) was set to 105 cm and the VMAT QA plan was delivered with 600 MU/min. For each QA plan, three measurements were made. The average pass rate (thresholds: 2%/2 mm) was then calculated. In addition, the dose at the isocenter or other points of clinical significance was also measured and the mean was calculated. Results: Our current institutional QA acceptance criteria for VMAT plans are: pass rate 90% for 2%/2mm with a dose threshold of 10% and the discrepancy between the measured and planned doses at the isocenter or other points of clinical significance 2%. Our preliminary investigation indicated that the pass rate was normally greater than 95.0% with a total number of valid detection points of ∼30000. The dose difference at the point of interest was, in general, around ±1.0 %. Sharp dose gradients were accurately detected at the PTV‐cord interface. Conclusions: EPID‐ based dosimetry is real‐time and financially viable. It can achieve sub‐ millimeter dosimetry accuracy without extensive inter‐diode interpolations. We believe that EPID‐based VMAT dosimetry offers a competitive alternative to other competing dosimetry technologies.
SU‐E‐T‐180: The Radiological Physics Center's Anthropomorphic Quality Assurance Phantom Program
Authors: Amador C , Hernandez N , Molineu A , Alvarez P , Followill D
Published: June 2012

Purpose: To describe the phantoms, program logistics and current results for the Radiological Physics Center's (RPC) anthropomorphic QA phantom program for credentialing institutions for participation in NCI‐sponsored advanced technology clinical trials. Methods: The RPC has developed an extensive phantom credentialing program consisting of four different phantoms designs: H&N, pelvis, lung and spine. These QA phantoms are water‐filled plastic shells with imageable targets, avoidance structures, and heterogeneities that contain TLD and radiochromic film dosimeters. Institutions wishing to be credentialed request a phantom and are prioritized for delivery. At the institution, the phantom is imaged, a treatment plan is developed, the phantom is positioned on the treatment couch and the treatment is delivered. The phantom is returned and the measured dose distributions are compared to the institution's electronically submitted treatment plan dosimetry data. Results: The RPC currently has an inventory of 31 H&N, 10 pelvis, 9 lung, and 8 spine phantoms that are mailed to institutions nationally and internationally. In 2011, 444 of these phantoms were mailed out for credentialing. Once the phantom is sent, it takes the institution an average of 26 days to return it to the RPC. On average the dosimeters are analyzed within 17 days and the report is sent 21 days after receipt of the phantom data. In 2011 the percent of phantoms meeting the acceptance criteria increased by 12, 13 and 6 percentage points for the H&N, spine and lung phantoms, respectively. It fell by 5 percentage points for the pelvis phantom. Conclusions: The RPC's QA phantom program has been an effective and responsive QA tool for assessing the use of advanced technologies in NCI sponsored clinical trials. The RPC has been efficient in its mailing of phantoms, and analyzing and reporting results. Work supported by PHS grant CA10953 and CA081647 (NCI, DHHS).
SU‐E‐T‐183: Managing and Assessing Patients Receiving Radiotherapy with Implantable Cardiac Devices
Authors: Prisciandaro J , Fox C , Horwood L , Hayman J , Makkar A , Moran J , Pelosi F
Published: June 2012

Purpose: To assess the effectiveness of the management of patients with cardiac electronic implantable devices (CEIDS) receiving radiotherapy.Method and Materials: In 2005, a formal communication process was established between Radiation Oncology and Cardiac Electrophysiology (EP) for the management of patients with permanent, implantable cardiac devices receiving radiotherapy. The process requires a pre‐treatment consult with EP. This information is provided to a medical physicist, who works with the primary radiation oncologist and dosimetrist. Based on the estimated dose to the device, EP and Radiation Oncology will determine the appropriate oversight required for treatment. To assess the effectiveness of this program, a retrospective analysis of patients with implantable cardiac devices receiving radiotherapy between the years 2005 and 2011 was performed. Results: Sixty‐nine patients with CEIDs (19 implantable cardioverter defibrillators (ICDs) and 50 pacemakers) were treated in Radiation Oncology between 2005 and 2011. Patients were treated to a variety of sites, including 21 patients treated to multiple sites. Doses were estimated prior to radiotherapy, and in vivo measurements were obtained for patients near or exceeding our institutional device tolerance (ICDs = 1 Gy and ICPs = 2 Gy), or if the device was less than 10 cm from the edge of a treatment field. Of the patients evaluated, there were only two patients with ICD devices which had a partial reset of diagnostic data during their treatment. There were no major device failures of arrhythmia detection or treatment. Conclusions: Our multi‐disciplinary team has worked together to develop a process to manage the care of patients with permanent implantable cardiac devices. There have been few device events noted in our patient cohort. The team will continue to follow our institutional management methodology to assess the appropriate amount of EP care necessary during radiation therapy. Laura Horwood is on the speakers bureau for Medtronic. Frank Pelosi is on the advisory board for Boston Scientific Corp and St. Jude Medical, is receiving an educational grants from Medtronic, St Jude, Boston Scientific, Biotronik, and a research grants from Medtronic.
SU‐E‐T‐184: LINAC Commissioning Measurements Utilizing the Cylindrical Arc Check Phantom
Authors: Aristophanous M , Balter P , Martel M , Murray N , Court L
Published: June 2012

Purpose: New devices for IMRT and VMAT QA are continually becoming available. Despite the availability of these devices they are underutilized for routine mechanical QA. In this work we take advantage of the cylindrical geometry of the Arc Check phantom to perform tests that are an integral part of commissioning and routine QA. Methods: The Arc Check is a cylindrical phantom with a diameter of 26.59cm and a 1386 diode array arranged on a cylindrical plane. Owing to its cylindrical design it is capable of measuring entry and exit radiation. For this experiment the Arc Check was set up using the mechanical pointer at 86.7cm SSD. The device was leveled using its inclinometer and was properly rotated to align with the lasers and cross‐hair. With the phantom set up at the expected isocenter of the LINAC, 100MUs with a 10×10 field were delivered at different gantry angles, couch and collimator rotations. Each delivery was recorded individually and for each one the radiation center at the entry and exit levels of the detector were estimated. That provided the path of the radiation center through the device. The radiation path was reconstructed for each rotation individually and the coincidence of the mechanical and radiation isocenter was evaluated. Results: A procedure and MATLAB routine were developed that accepted as input the text files that are the output of the Arc Check measurement and geometrically reconstructed in 3‐dimensions the isocenter and radiation central axis for each rotation. The coincidence of the radiation and mechanical isocenter was verified. Conclusions: This work demonstrates that by utilizing the geometry of a commercially available device multiple mechanical LINAC tests that are part of routine QA can be evaluated in one single setup.
SU‐E‐T‐190: Design, Development, and Evaluation of a Modified, Anthropomorphic, Head, Quality Assurance Phantom for Use in Stereotactic Radiosurgery
Authors: Faught A , Kry S , Luo D , Molineu A , Bellezza D , Gerber R , Davidson S , Bosch W , Galvin J , Drzymala R , Timmerman R , Sheehan J , Gillin M , Ibbott G , Followill D
Published: June 2012

Purpose: To develop and evaluate a modified anthropomorphic head phantom for evaluation of stereotactic radiosurgery (SRS) dose planning and delivery. Methods: A phantom was constructed from a water equivalent, plastic, head‐shaped shell. The original phantom design, with only a spherical target, was modified to include a nonspherical target (pituitary) and an adjacent organ at risk (OAR) (optic chiasm), within 2 mm, simulating the anatomy encountered when treating acromegaly. The target and OAR spatial proximity provided a more realistic treatment planning and dose delivery exercise. A separate dosimetry insert contained two TLD for absolute dosimetry and radiochromic film, in the sagittal and coronal planes, for relative dosimetry. The prescription was 25Gy to 90% of the GTV with >= 10% of the OAR volume receiving >= 8Gy. The modified phantom was used to test the rigor of the treatment planning process, dosimeter reproducibility, and measured dose delivery agreement with calculated doses using a Gamma Knife, CyberKnife, and linear accelerator based radiosurgery systems. Results: TLD results from multiple irradiations using either a CyberKnife or Gamma Knife agreed with the calculated target dose to within 4.7% with a maximum coefficient of variation of+/−2.0%. Gamma analysis in the coronal and sagittal film planes showed an average passing rate of 99.3% and 99.5% using +/−5%/3mm criteria, respectively. A treatment plan for linac delivery was developed meeting the prescription guidelines. Dosimeter reproducibility and dose delivery agreement for the linac is expected to have results similar to the results observed with the CyberKnife and Gamma Knife. Conclusions: A modified anatomically realistic SRS phantom was developed that provided a 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, CA21661 awarded by NCI. DHHS
SU‐E‐T‐192: Computer Vision for Final Online Treatment Parameter Verification
Authors: Stakhursky V , Finn J , Kanumalla V , Lysiuk I , Kriminski S
Published: June 2012

Purpose: In a typical model of Radiation Oncology data flow, treatment plan is designed on treatment planning station (TPS) under the supervision of physician and physicist, and machine specific parameters are pushed to Record and Verify system (RV) for treatment data storage, where it stays available for daily uploads to treatment station. While various QA programs could be established to verify uncorrupted planning data storage and transfer, the ultimate goal is a daily confirmation of patient treatment parameters versus original treatment plan. Methods: A new computer vision approach, RTcheck, is used to digitize loaded machine parameters directly from the screen of Varian Clinical Console every time before the beam is turned on by a therapist. The verification engine runs a check against the parameters automatically extracted from the printed postscript planning report (Pinnacle, Philips) prepared during planning stage and approved by physician. All important beam data, MUs, jaws position, beam energy, couch angle, and wedge specifiers are displayed side by side on the screen of RTcheck station. All field verifications are recorded to a log file, periodically reviewed by a physicist. Results: In our clinical tests, the electronic verification of machine treatment parameters shortened patient ‘on the table’ time, as the manual therapist's ‘time out’ check before every beam on may take up to several minutes for patient treatments with multiple beams (more than 10). Our analysis of verification logs revealed several instances of a small X1 jaw position discrepancy of 0.1cm for jaw position range of 0 to −2cm. After jaw recalibration, the problem was eliminated. Conclusions: RTcheck is the end‐to‐end quality assurance approach to verify data flow from TPS to treatment machine for every patient treatment. Computer vision approach may help reduce human error factor, and shorten patient treatment time. Conflict of interest: S. Kriminski and I. Lysiuk: provisional patent application is submitted to United States Patent and Trademark Office
SU‐E‐T‐195: Experience in Implementing Intraoperative Radiation Therapy for Accelerated Partial Breast Irradiation Using Low‐Energy X‐Ray Source
Authors: Morales‐Paliza M , Luo G , Ding G
Published: June 2012

Purpose: To present our preliminary experience and quality‐assurance (QA) procedures in implementing intraoperative‐radiation therapy (IORT) for accelerated‐partial‐breast irradiation (APBI) using the Axxent‐system controller (Xoft Inc.) Methods: IORT was implemented in our institution utilizing a 50‐keV x‐ray source. APBI allows breast conserving in patients with early‐stage‐breast cancer by delivering radiation to the lumpectomy bed via an applicator balloon filled with water, to which a prescribed dose of 20 Gy was applied to its surface. In‐situ anesthesiology, breast‐surgery and radiation‐oncology teams were required to achieve this procedure. Calibration of the source, including temperature and pressure corrections, was performed by the controller resulting in a calibration factor, which was manually introduced by a physicist into an in‐house program providing the corrected dwell times. Evaluation of exposure measurements determined that personnel standing behind glass‐rolling shields during irradiation were sufficient protection. Results: We have successfully treated four patients to date. Surgical times averaged about two hours, QA and setup of controller took about 30 minutes, while radiation‐treatment times ranged 7.8–10.4 minutes. Exposure to personnel showed a negligible dose compared to background based on the in‐vivo measurements. Our measurements have shown that placement of a shielding layer (FlexiShield) on top of the drape‐protected breast reduced radiation exposure to in‐room personnel. In one case, treatment was automatically stopped by the controller due to a sudden undetected cooling water flow; due to the pre‐treatment training, treatment was successfully resumed within a minute after manual adjustment of the flow sensor. Conclusions: Implementation of IORT to treat patients with APBI using low‐energy x‐ray source should follow the manufacturer's recommendations regarding to the acceptance and personnel training. Our experience indicates that two physicists are necessary at least at the implementation stage. Appropriate training to deal with potential problems is crucial before clinical treatment can be ready.
SU‐E‐T‐198: Patient Scheduling Monitor (PSM)‐A New Tool for Radiation Therapy Patient Scheduling and Workflow Management in an Increasingly Digital Environment
Authors: Liu H , Kim J , Chen Z
Published: June 2012

Purpose: To develop an easy‐to‐use and customizable Patient Scheduling Monitor for 1) active monitoring of radiation therapy workflow from CT simulation to the start of treatment and 2) for optimizing the workflow based on treatment complexity. Methods: Microsoft Access database and Visual Basic language were used to create an in‐house software application, Patient Scheduling Monitor (PSM). The PSM was designed with three functional modules: a patient schedule calculator, a workflow progress tracker, and a workflow evaluator. The PSM divides the radiation treatment workflow into 6 tasks including image acquisition/fusion, target delineation, dosimetry planning, MD review, physics QA and RTT QA. On the day of CT simulation, the scheduling calculator generates a planned timeline for each task based on the CT‐simulation date and the default standard established for each given task and treatment type. Each task within the PSM can also be individualized as needed. After simulation, the progress tracker enables staff to actively monitor the workflow. The workflow evaluator will query the database and analyze the planned versus actual timeline and provide data for future workflow analysis. Results: We have used the PSM since Nov, 2011 for 186 patients. The PSM has allowed us to provide patient start times at the completion of simulation. It has helped to improve patient satisfaction. The workflow progress tracker enabled us to actively manage the workflow. Currently, for patients managed using the PSM, no rescheduling has been required. The use of PSM has reduced the average CT simulation to treatment start times. It also has improved intradepartmental communications. Conclusions: An easy‐to‐use patient scheduling monitor has been developed. The PSM has been shown to be an efficient and effective tool in managing, assessing and improving the radiation therapy workflow and will be useful in managing the timelines in an increasingly dynamic working environment.
SU‐E‐T‐200: IMRT Patient Specific QA for On‐Line Adaptive Radiotherapy
Authors: Gao Z , Wong J , Merrick S , Karim M , Li M
Published: June 2012

Purpose: On‐line adaptive IMRT requires a highly efficient radiotherapy team and an intensive amount of work, as well as significant amount of Quality Assurance (QA). With regard to patient specific QA, it is clinically unrealistic to perform fluence measurements via a QA phantom while patient is setup awaiting treatment. We therefore developed an alternative way to check point dose and the IMRT fluence right before beam delivery. Methods: In this study, 28 IMRT plans were generated with Prowess Panther 5.1 for three prostate cancer patients on 28 CT datasets with CTV and critical organs contoured by treating physicians. The corresponding QA plans were generated by Prowess, and then transfered to Pinnacle 9.2 for fluence recalculation on a flat surface phantom, In addition 28 QA plans were delivered on a Siemens Artiste accelerator and fluence were measured with Matrixx IMRT Device. We analyzed both point dose and fluence for these 28 samples. Results: Of all 28 IMRT plans, the point dose difference between Prowess and Pinnacle are well within 1%. The point dose difference between measurements and Prowess calculation are all within 3%. The passing rates using gamma criteria (3%3mm) for the fluence comparison between Prowess and Pinnacle calculation are at least 98.5% while the passing rates of the gamma analysis between fluence measurement and Prowess calculation are all better than 98.5%. The passing rate of gamma difference between Prowess vs Pinnacle and Prowess vs QA measurement is less than 1.5% for all 28 samples. Therefore, second TPS (e.g. Pinnacle) can be used to verify planned fluencies and can serve as a valuable patient specific QA when conventional IMRT QA measurement is not feasible. Conclusions: A new IMRT plan is desired if significant anatomy change from the date of original CT scan is observed before the radiation delivery. It is not clinically feasible to check the fluence on the machine before radiation delivery while the patient is in the treatment suite awaiting radiation delivery. Our method showed here is an alternative way to verify the planned fluence with a second TPS and can serve as a valuable IMRT patient specific QA in online adaptive radiotherapy.
SU‐E‐T‐201: Safety‐Focused Customization of Treatment Plan Documentation
Authors: Schubert L , Westerly D , Stuhr K , Miften M
Published: June 2012

Purpose: Plan report documentation contains numerous details about the treatment plan, but critical information for patient safety is often presented without special emphasis. This can make it difficult to detect errors from treatment planning and data transfer during the initial chart review. The objective of this work is to improve safety measures in radiation therapy practice by customizing the treatment plan report to emphasize safety‐critical information. Methods: Commands within the template file from a commercial planning system (Eclipse, Varian Medical Systems) that automatically generates the treatment plan report were reviewed and modified. Safety‐critical plan parameters were identified from published risks known to be inherent in the treatment planning process. Risks having medium to high potential impact on patient safety included incorrect patient identifiers, erroneous use of the treatment prescription, and incorrect transfer of beam parameters or consideration of accessories. Specific examples of critical information in the treatment plan report that can be overlooked during a chart review included prescribed dose per fraction and number of fractions, wedge and open field monitor units, presence of beam accessories, and table shifts for patient setup. Results: Critical information was streamlined and concentrated. Patient and plan identification, dose prescription details, and patient positioning couch shift instructions were placed on the first page. Plan information to verify the correct data transfer to the record and verify system was re‐organized in an easy to review tabular format and placed in the second page of the customized printout. Placeholders were introduced to indicate both the presence and absence of beam modifiers. Font sizes and spacing were adjusted for clarity, and departmental standards and terminology were introduced to streamline data communication among staff members. Conclusions: Plan reporting documentation has been customized to concentrate and emphasize safety‐critical information, which should allow for a more efficient, robust chart review process.
SU‐E‐T‐204: A Prototype of Dose‐Guided Radiation Therapy
Authors: Ren Qiang , Li Gui , Wang Yu , Wu Yican ,   FDS Team
Published: June 2012

Purpose: With the advancement in dosimetric devices and the development of dose reconstruction algorithm, the implementation of dose‐guided radiation therapy (DGRT) is feasible. In order for DGRT to be performed clinically, a prototype of DGRT was developed in this study. Methods: The prototype adopted a strategy for DGRT that adjusted the treatment plan for future fractions to compensate for dosimetric errors from past fractions, which included four main functional modules: management of patient plan information, dose reconstruction, dose evaluation, plan adjustment. we developed our dose reconstruction procedure, including the dosimetric calibration of the portal image acquired using electronic portal image device (EPID) during treatment and three‐dimensional (3D) patient dose reconstruction based on Monte Carlo Finite‐size pencil beam (MCFSPB) model and Conjugate‐gradient (CG) algorithm developed by FDS Team (www.fds.org.cn). The dose evaluation tools including 3D Gamma analysis and dose‐volume‐histogram (DVH) analysis were also available which were used to compare the reconstruction dose with the planning dose. Finally we re‐optimizing the treatment plan according to the information provided by dose evaluation. Results: In order to validate the availability of the workstation prototype, lots of experiments were carried out based on head phantom. The result showed that disagreement between the reconstructed dose and the planning dose (calculated by the Accurate Radiotherapy System (ARTS) developed by FDS Team) was observed by the DGRT prototype when there existed position error for head phantom or the accelerator delivery was not accurate. Conclusions: An effective prototype for DGRT has been developed. With these techniques, the clinical implementation of DGRT is possible in the near future. Supported by the National Natural Science Foundation under grant No.30900386 and the National Science Foundation of Anhui Province (Nos.090413095 and 111040606Q55).
SU‐E‐T‐205: MLC Predictive Maintenance Using Statistical Process Control Analysis
Authors: Able C , Hampton C , Baydush A , Bright M
Published: June 2012

Purpose: MLC failure increases accelerator downtime and negatively affects the clinic treatment delivery schedule. This study investigates the use of Statistical Process Control (SPC), a modern quality control methodology, to retrospectively evaluate MLC performance data thereby predicting the impending failure of individual MLC leaves. Methods: SPC, a methodology which detects exceptional variability in a process, was used to analyze MLC leaf velocity data. A MLC velocity test is performed weekly on all leaves during morning QA. The leaves sweep 15 cm across the radiation field with the gantry pointing down. The leaf speed is analyzed from the generated dynalog file using quality assurance software. MLC leaf speeds in which a known motor failure occurred (8) and those in which no motor replacement was performed (11) were retrospectively evaluated for a 71 week period. SPC individual and moving range (I/MR) charts were used in the analysis. The I/MR chart limits were calculated using the first twenty weeks of data and set at 3 standard deviations from the mean. Results: The MLCs in which a motor failure occurred followed two general trends: (a) no data indicating a change in leaf speed prior to failure (5 of 8) and (b) a series of data points exceeding the limit prior to motor failure (3 of 8). I/MR charts for a high percentage (8 of 11) of the non‐replaced MLC motors indicated that only a single point exceeded the limit. These single point excesses were deemed false positives. Conclusions: SPC analysis using MLC performance data may be helpful in detecting a significant percentage of impending failures of MLC motors. The ability to detect MLC failure may depend on the method of failure (i.e. gradual or catastrophic). Further study is needed to determine if increasing the sampling frequency could increase reliability. Project was support by a grant from Varian Medical Systems, Inc
SU‐E‐T‐206: Standardization in Documentation Format Can Significantly Reduce Manual Data Entry Error in Patient Chart
Authors: Zhou S , Chen S , Wahl A , Enke C
Published: June 2012

Purpose: To demonstrate that standardization in documentation format can significantly reduce manual data entry error in patient chart. Method and Materials: Due to lack of direct data link between CT on rail imaging registration software and patient R&V system, therapists have to manually enter translation correction of patient position into R&V system after performing imaging registration between CT image taken just before treatment delivery and treatment planning CT image. Approximately six months after CT on rail was placed into clinical service, we started requiring therapists to use a standard format to document the shifts when they manually enter data to reduce manual data entry error rate. The therapist manual data entry errors in R&V system before (551 entries) and after the format standardization (1645 entries) are the subjects of statistical analysis. The errors are divided into two categories (recoverable and non‐recoverable errors) depending on whether a human being can recover the translation shifts in lateral, longitudinal, and vertical directions from the therapist notes. Fisher's exact test is performed to test the statistical significance of therapist's data entry error reduction after our imposing the documentation format requirement. Temporal information on when the errors were made is also analyzed to find out when errors are more likely to happen. Results: Statistical analysis indicated that reductions in the numbers of recoverable, non‐recoverable, and total errors after standardization in document format are all statistically significant with p values less than 0.05. Conclusion: A simple and low cost measure like standardization in document format can significantly reduce the errors operators introduce to patient R&V system when they perform manual data entry. We hope our experience will convince people to follow more disciplined documentation rule to reduce the error rate and therefore potentially can improve the quality of patient care when manual data entry is involved.
SU‐E‐T‐209: Four‐Dimensional Gamma Method for Dose‐Guided Radiotherapy
Authors: Wang Y , Li G , Ren Q , Wu Y
Published: June 2012

Purpose: The technique known as ‘Gamma Evaluation Method’ was an effective measure for dose distribution comparison; however, it could not be used for accurate real‐time verification because of the unstable systematic factors. To reduce the errors induced by systematic factors and there was a requirement for real‐time dose verification in Dose‐guided Radiotherapy (DGRT), the formula of Gamma Method was improved, and four‐dimensional(4D) Gamma Method was proposed. Methods: The gamma index, showing the deviation of two sets of dose distributions, should remove the error caused by different treatment delivery time to realize accurate real‐time verification in Dose‐guided Radiotherapy. Besides dose and distance, the variable of time, which was proportional to monitor unit (MU), was added to the formula. The criterion for acceptable distribution was generally defined as a tolerance of the dose, the distance and monitor unit. The algorithm was designed and realized using the tool of Microsoft Visual C++ 6.0. Results: Two typical five beam treatment plans of Conformal Radiotherapy and Intensity‐Modulated Radiotherapy were adopted to verify the algorithm. The two‐dimensional (2D) ionization chamber MatriXX was used to measure the dose distribution. The verification for each beam was as follows: (1) analyze the evaluation results of gamma method and the improved gamma method. (2)Analyze the evaluation results of measured dose distributions at different time with the same dosage .The result showed that there existed errors caused by systematic factors before formula was improved. Improved method could obviously reduce the error induced by systematic factors, meeting DGRT's requirement for accurate real‐time verification. The result could also be used to judge the stability of the accelerator. Conclusions: The 4‐dimensional gamma method could reduce errors caused by systematic factors, and it could be used to reflect the stability of different accelerators. Supported by the National Natural Science Foundation under grant No.30900386 and the National Science Foundation of Anhui Province (Nos.090413095 and111040606Q55).
SU‐E‐T‐215: A Technique for Treating Patients outside the Mosaiq R&V System for TrueBeam Users (or 4DTC)
Authors: Nelson C , Gifford K , Kisling K , Kirsner S
Published: June 2012

Purpose: When the record and verify (R&V) system (Mosaiq, Elekta Medical Systems) is unavailable to send information to the treatment console of the linear accelerator (Varian Clinac, Varian Medical Systems), treatment is manually delivered by entering parameters into the treatment console and loading backed up MLC files. The new linear accelerator, the TrueBeam (Varian Medical Systems) lacks the ability to manually deliver treatment by entering machine parameters into the treatment console. Methods: The TrueBeam can only deliver treatments using the R&V system or loading DICOM RT plan files directly in File Mode. Every time a prescription site is sent from the R&V system to the accelerator, a DICOM RT plan file is created by the R&V system. A script was created that reads the headers of these files, copies them to the treatment console and renames them in an identifiable form. At the end of each treatment day, the script is executed transferring only the DICOM RT plan files created that treatment day. A contingency report is then generated from the R&V system, which contains machine parameters for all fields for all patients under treatment. When the R&V system is unavailable the RT plan files are opened in file mode, and the machine parameters are verified using the contingency report before delivery. This system was tested on a cohort of patients. Each patient's plan was opened in file mode and the machine parameters were verified against the patient's planned treatment in the R&V system. Results: All files opened in file mode were identical to the information stored in the R&V system. This was tested both on the TrueBeam and accelerators having the 4DTC. Conclusions: Our technique was validated and is an alternative method for delivering treatment when the R&V system is unavailable.