bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐T‐612: Integral Dose Study of Non‐Coplanar 4pi Radiotherapy
Authors: Nguyen D , Dong P , Ruan D , Low D , Sheng K
Published: July 2013

Purpose: To quantify the integral doses of 4π highly non‐coplanar treatment plans and compare them to traditional coplanar IMRT plans. Methods: A systematic study was conducted using an elliptical cylinder, with a major axis length of 35.4 cm and minor axis length of 23.6cm. A 4.5cm diameter spherical tumor was embedded at 4 equally spaced radial locations on the long axis from the center to the periphery. Twenty 6MV conformal non‐coplanar beams were selected in a fashion so that their trajectories would form a circular cone 24° with respect to the cone axis that converged on the tumor. A coplanar plan using twenty evenly spaced conformal 6MV coplanar beams was conducted for comparison. The dose distribution was calculated using the convolution/superposition algorithm. A patient study was also conducted for 10 liver and 12 lung SBRT cases. A column generation algorithm was used to optimize both beam orientations and the fluence map. The dosimetry was compared to clinical plans using 2‐arc volumetric modulated arc therapy (VMAT). Results: For the centrally‐located tumor, non‐coplanar plans delivered up to 37% greater integral dose but the ratio decreased rapidly with the tumor locating more superficially. Approximately the same integral dose resulted from both planning methods at a tumor depth of 10 cm. For the tumor at 6cm depth, the non‐coplanar plan integral dose was approximately 10% lower. Compared to VMAT, the integral dose to the liver and lung SBRT patients were reduced by 17% and 42% using 4π, respectively. Conclusion: Non‐coplanar plans can reduce integral doses as exemplified by both the phantom and patient studies. The effect is most significant with shallower tumors, e.g. the tumor center within 10 cm of a given surface in the simplified phantom model. Actual patient treatments benefit more due to the optimization of the non‐coplanar beam angles.
SU‐E‐T‐615: SmartArc‐Based Volumetric Modulated Arc Therapy for Endometrial Cancer: A Dosimetric Comparison with Helical Tomotherapy and Intensity‐Modulated Radiation Therapy
Authors: Yang R , Wang J , Xu S , Li H
Published: July 2013

Purpose: To investigate the feasibility of volumetric modulated arc therapy with Smart Arc (VMAT‐S) for endometrial cancer to achieve equivalent plan quality with higher delivery efficiency, against intensity‐modulated radiotherapy (IMRT) and helical tomotherapy (HT). Methods: Nine patients with endometrial cancer were retrospectively studied. Three plans were generated with VMAT‐S, IMRT and HT for each patient. The dose distribution of planning target volume (PTV), organs at risk (OARs) and normal tissue were compared. The monitor units (MUs) and treatment delivery time were also evaluated. Results: The average homogeneity index was 1.06, 1.10 and 1.07 for VMAT‐S, IMRT and HT plans. The V40 of rectum, bladder and pelvis bone decreased 9.0%, 3.0%, and 3.0% in VMAT‐S compared with IMRT, respectively. The target coverage and OARs sparing were comparable between VMAT‐S and HT. The average MU was 823, 1105 and 8403 for VMAT‐S, IMRT and HT. The average delivery time was 2.6 minutes, 8.6 minutes, and 9.5 minutes. Conclusion: VMAT‐S provided comparable plan quality with significantly shorter delivery time and less MUs compared with IMRT and HT for endometrial cancer. In addition, more homogeneous PTV coverage and superior OARs sparing in the medium to high dose region were observed in VMAT‐S over IMRT. Ruijie Yang was funded by the grant project: National Natural Science Foundation of China (No. 81071237). Junjie Wang, Shouping Xu and Hua Li have no competing interest.
SU‐E‐T‐616: Dosimetric Comparison of Volumetric Modulated Arc Therapy, Step‐And‐Shoot, and Sliding Window IMRT for Prostate Cancer
Authors: Schnell E , De La Fuente Herman T , Young J , Hildebrand K , Algan O , Syzek E , Herman T , Ahmad S
Published: July 2013

Purpose: To evaluate treatment plans generated by Step‐and‐Shoot (SS), Sliding Window (SW) and Volumetric Modulated Arc Therapy (VMAT) in order to assess the differences in dose volume histograms of planning target volume (PTV) and organs at risk (OAR), conformity indices, radiobiological evaluations, normal tissue dose, and plan quality for prostate cancer cases. Methods: Ten prostate cancer patients treated in our center were selected for this retrospective study. Treatment plans were generated with Eclipse version 8.9 using 10 MV photon beams. For VMAT, Varian Rapid Arc with 1 or 2 arcs, and for SS and SW IMRT, 7ndash;9 coplanar fields were used. Each plan had three PTVs with prescription doses of 81, 59.4, and 45 Gy to prostate, to prostate and lymph nodes, and to pelvis, respectively. Doses to PTV, OAR, normal tissues, and the conformal indices (COIN) were compared among three techniques. The equivalent uniform dose (EUD), tumor control probability (TCP), and normal tissue complication probability (NTCP) were calculated and compared. Results: The average mean doses to the PTV prostate were 82.8 Gy and the average differences of mean dose among all techniques were below 0.3 Gy. For bladder and rectum, the percent differences of average mean dose among all techniques were below 2.2%, though high dose rectal volumes were reduced for VMAT. The COIN slightly favoured VMAT. The average TCP varied by less than 0.001%. The average NTCP for the rectum was 3.55%, 3.75% and 3.87% for VMAT, SS and SW, respectively, while the differences in the average NTCP for the bladder was negligible. The full body volumes receiving 20 to 30 Gy were reduced in VMAT treatments. Conclusion: Data indicates similar target coverage and OAR sparing in general. Additional patients will continue to be added to the study. Variation in normal tissue distribution was less than expected.
SU‐E‐T‐621: Is Non‐Coplanar Tangential Beam IMRT Better Than the Field in Field Technique for Left Sided Whole Breast Radiotherapy?
Authors: Sidhique H , Madebo M , Kron T , Cramb J , Chua B , Durai M
Published: July 2013

Purpose: To study the comparison of 4 field non‐coplanar tangential beam IMRT (nctbIMRT) with FIF technique for early stage left‐sided, instead widely used comparison of coplanar IMRT with FIF. Methods: Retrospective study was done on 10 patients left‐sided, intact, whole breast RT. Followings are the 2 simple factors:d' and Δd, where d' ‐distance between skin and posterior border of PTV and Δd‐distance between posterior border of PTV and heart at largest heart and breast CT‐slice. Both are on line that passes though center of heart. With these, patients were classified into 4 classes based on PTV size and distance of heart from PTV as follows: Class 1: large PTV, close heart; 2: large PTV distant heart; 3 small PTV, close heart; 4: small PTV, very close heart. Results: For patients with heart close to PTV, nctbIMRT showed better PTV coverage and better organs at risk sparing. The average D95 of PTV and D5 of heart for FIF were found to be 96.2% and 83.9%, 95.1% and 8.27%, 92.38% and 55.3% and 92.7% and 46.8% for class 1, 2, 3 and 4, respectively. For nctbIMRT, D95 of PTV and D5 of heart were 99.7% and 15.6%, 97.25% and 9.3%, 97.42% and 29.8% and 96.8% and 35% for class 1, 2, 3 and 4, respectively. Conclusion: Unlike coplanar IMRT, nctbIMRT containing tangential beams, as shown in study, is advantageous in that it reduces volumes receiving low dose in critical structures. This method of classification is more realistic than making generalisation based on the average dosimetric parameters of all patients considered. While all patients in Class 1, 3 and 4 are beneficiaries of the nctbIMRT technique, patient in Class 4 presenting with heart adjacent to PTV benefited the most. On the other hand, FIF may be preferable for Class 2 patients with distant heart to the PTV.
SU‐E‐T‐655: Dose Matrix Sampling Heuristic Applied to Improving IMRT Optimization Efficiency
Authors: Spaans J , Nazareth D
Published: July 2013

Purpose: To introduce a novel heuristic that increases the efficiency of IMRT fluence optimization, by employing sampled dose values in evaluation of the objective function. Methods: Pencil beam dose matrices were computed using CERR, for 1‐cm square beamlets. These matrices were then uniformly sampled at various rates (1–10%), and the resulting approximate dose‐volume values compared to the true values for various fractional volumes. By varying the beamlet weights for 10,000 random sets, we estimated the error in these approximations to be <1%. For IMRT optimization, a least squares objective function was used, based on clinical dose‐volume objectives. In the initial stage of optimization, the method utilizes approximate dose values, determined by 1% or 5% dose matrix sampling, in objective function evaluation. This results in a significant reduction in computation time, since the manipulation of large dose matrices is avoided. The optimized beamlet weights are subsequently used as the starting point in the final optimization. This method was evaluated on prostate bed and esophageal patients, by comparing the CPU time required with that of a standard optimization method. The downhill simplex and simulated annealing algorithms were used for the evaluations. Results: The prostate bed patient was optimized with both a 1% and 5% sampling rate resulting in patient treatment plans of equal score, and a time savings of 18% and 42%, respectively. The esophageal patient was optimized with a 5% sampling rate and provided a score improvement of 23%, with a time savings of 17%. Conclusion: We have developed a method to be used in conjunction with existing optimization algorithms, which dramatically decreases the number of standard objective function evaluations and computation time. This technique may be applied to any type of optimization algorithm and set of clinical variables requiring pre‐computed dose matrices and objective functions involving dose‐volume objectives (eg. multi‐criteria optimization).
SU‐E‐T‐667: Accuracy of XiO Treatment Planning System in Predicting Lateral Penumbra for Different Air Gap and Compensator Thickness in Uniform Scanning Proton Therapy
Authors: Rana S , Zeidan O , Ramirez E , Rains M , Gao J , Zheng Y
Published: July 2013

Purpose: The purpose of this study is to investigate the accuracy of XiO treatment planning system (TPS) in predicting lateral penumbra (80%‐20% distance) for different air gap (AG) and compensator thickness (COMP) in uniform scanning proton therapy. Methods: First, the dependency of lateral penumbra on AG was investigated for AG 0, 5, 10, 15, 20, 25, 30, and 35 cm using beam parameters of range (R)=16cm, modulation (M)=10cm, COMP=5cm, snout (SNT)=10, and aperture diameter(AP)=10 cm. Second, the dependency of lateral penumbra on COMP was investigated for COMP 0, 5, 10, 15, and 20 cm using beam parameters of R=30cm, M=10cm, AG=5cm, SNT=10, and AP=10cm. Dose calculations were performed in a virtual water phantom using XiO TPS with pencil beam algorithm, whereas measurements were done using solid‐water plates and EDR‐2 films. Furthermore, depth for all dose calculations and measurements was selected at the center of Spread Out Bragg Peak (SOBP), which coincided with the isocenter of the beam. The OmniPro‐I' mRT software was used to analyze the films. The lateral penumbra from the dose computations and measurements were compared for the horizontal and vertical scanning magnets. Results: Both the TPS and measurements showed an almost linear increase in lateral penumbra with increasing AG. The lateral penumbra results of TPS were larger than measurements, with difference ranged from 0.5 to 1.6 mm for horizontal scanning magnet and from 0.5 to 2.6 mm for vertical scanning magnet. The dependency of lateral penumbra on COMP was less sensitive compared to lateral penumbra versus AG. The discrepancy between lateral penumbra results of TPS and measurements for different COMP ranged from 0.2 to 0.8 mm for horizontal scanning magnet and from 0.9 to 1.7 mm for vertical scanning magnet. Conclusion: The XiO TPS over‐predicted the lateral penumbra compared with the measurements.
SU‐E‐T‐680: An Interactive Graphical User Interface for Physician‐Driven Treatment Plan Tuning
Authors: Shi F , Zarepisheh M , Gautier Q , Moore K , Cervino L , Jia X , Jiang S
Published: July 2013

Purpose: To develop an interactive graphical user interface (GUI) for physicians to conveniently and efficiently fine‐tune an IMRT treatment plan. Methods: After an IMRT plan is developed either automatically or manually by a dosimetrist, the attending physician evaluates its quality and prefer to directly modify the DVH curves and the unsatisfactory part of dose distribution. We have developed an interactive GUI for this purpose. For the unsatisfactory part of a DVH curve, the physician can drag and drop it to where it is preferred using the computer mouse or touchpad. The treatment plan is then re‐optimized in near real‐time on the background GPUs to best match the physician's desire. The physician can also click a point in the dose distribution and drag it to modify the isodose lines to a more desired configuration. This mouse movement vector is propagated to its neighboring area to form a local vector field, which is used to modulate the underlying dose distribution. The new dose distribution is used to guide the plan re‐optimization in near real‐time. The re‐optimized DVHs and isodose lines are then displayed for the physicians to edit in the next iteration. This process is repeated until a physician satisfactory plan is achieved. Results: We have tested this GUI for a series of IMRT plans. Results indicate that the proposed method provides the physicians an intuitive and efficient graphical tool to edit the DVHs and dose distributions according to their preference. The input information is used to guide plan re‐optimization in near real‐time using our GPU optimization engine. Typically, a satisfactory plan can be developed by a physician in a few minutes using this tool. Conclusion: We have developed an interactive GUI for tuning IMRT treatment plans and demonstrated its feasibility through a series of clinical tests.
SU‐E‐T‐681: Pitfalls in Dose‐Volume Histogram Computations
Authors: Kaster F , Aznar M , Kadir T
Published: July 2013

Purpose: To systematically study the effects of computation details on DVH accuracy for the first time in a teletherapy planning context, measure the effect sizes of different parameters and make recommendations for quality assurance in multicentric studies. Methods: We defined two IMRT plans (maximum doses: 84/79 Gy) on a physical phantom (using a commercial TPS) and exported five dose volumes with different resolutions (1 * 1 * 0.83 mm^3, 2 * 2 * 2.5 mm^3, 3 * 3 * 2.5 mm^3, 4 * 4 * 5 mm^3, 5 * 5 * 5 mm^3) and contours for fifteen structures (volumes between 1 and 349 cm^3). We computed 7200 DVHs by independently varying dose bin number (2^7, 2^8, 2^9, 2^10), grid geometry (CT, dose volume), voxel counting scheme (completely inside, center inside, partial volume‐weighted), interpolation method (nearest neighbor, linear, cubic). For each structure, the DVH with optimal simulation / computation parameters was interpreted as ground truth, and compared against the suboptimal DVHs using the percentage of failing gammas (PFG) distance (doi:10.1088/0031‐9155/55/11/N04) [1 Gy dose tolerance, 2% volume tolerance]. The effect sizes of the various parameters were estimated via ANOVA. Results: DVH accuracy (as measured by PFG) depended significantly on dose resolution (p<1e‐15), grid geometry (p<1e‐15) and voxel counting scheme (p=9e‐4), with partial ŋ2 values of 0.408 / 0.104 / 0.002. Bin number and interpolation method were negligible. DVHs computed from a 4 mm grid had an almost three times higher average PFG than DVHs from a 2 mm grid (0.42 vs. 0.16). Conclusion: For applications where DVH comparability between clinical sites with different TPS is imperative (e.g. multicentric studies), the dose resolution should be strictly identical, and researchers should ensure that DVHs are consistently computed either in the dose or CT grid geometry. Differences in the other computation parameters can be tolerated. Dose volumes with a resolution of >3 mm, whilst occasionally encountered in clinical routine, are unsuitable for accurate DVH computation. FK and TK are employees of Mirada Medical. However, the contents of this abstract constitute strictly basic research, so that there is no conflict of interest.
SU‐E‐T‐696: Registry Based Framework for Plan Quality Improvement: A Head‐And‐Neck Radiotherapy Application Improving Simultaneous Integrated Boost Treatments
Authors: Qi S , Lee S , Kupelian P , Pham A , Low D , DeMarco J
Published: July 2013

Purpose: To systemically evaluate the dosimetric plan quality and consistency for multiple IMRT delivery techniques to further improve guidelines for head‐and‐neck (H&N) irradiation. Method: One hundred consecutive H&N patients from our patient registry were selected and analyzed retrospectively. Simultaneous integrated boost (SIB) IMRT treatment were generated with the same prescription dose of 69.3/62.7/56.1Gy on TomoTherapy(Tomo, Accuray), TrueBeam(TB, Varian) using fixed‐field IMRT(TB_IMRT) or RAPIDARC(TB_RAPIDARC) or Siemens Oncor (Siemens_IMRT, Siemens). The contouring was performed by the same physicians delineating targets and normal structures. The standard in house dose‐volume objectives were used as planning guideline for all cases for all techniques. A Matlab based dose‐volume extraction and analysis tool was developed to export dose‐volume endpoints for each patient. A more specific guideline was proposed for future planning purpose. Results: While all techniques yielded comparable target coverage, the doses to the critical structures differed. In average, the percent volumes receiving greater than 26Gy (V26 and standard deviation) for the total parotid were 37.8±0.1, 46.1±0.2, 44.3±0.2 and 41.8±12.9%, the V65 for mandible were 4.7±5.6, 6.3±11.1, 3.0±5.3 and 8.0±7.3 % with the mean mandible doses of 42.5±6.1, 41.4±8.2, 37.4±10.7 and 46.6±8.7 Gy for Tomo, TB_IMRT, TB_RAPIDARC and Siemens_IMRT plans respectively. ANOVA analyses showed significant difference for the maximum dose of cord but no significant difference was found for other selected structures among four IMRT techniques. Based on current dataset, the projected constraints (at 95% confidence level) for future H&N IMRT plans for cord maximum doses were established at 34.0±2.9, 42.7±2.5, 43.3±2.3, and 45.4±2.4Gy for the evaluated techniques, respectively. The refined dosimetric constraints may improve plan quality and consistency. Conclusion: Patient registry based processes enable easy access of systematic dosimetric monitoring of the plan quality and consistency. The self‐evolving real‐time dosimetric evaluation and ensuing guidelines will help to continuously improve plan quality, resulting in better clinical outcome.
SU‐E‐CAMPUS‐T‐06: Preliminary Investigation with In Vivo Dosimeters Into the Efficacy of a Dose Accumulation Workflow for Adaptive Planning
Authors: Studenski M , Gardner S , Pirozzi S , Den R
Published: July 2013

Purpose: Assess the applicability of the MIM Maestro (MIM Software, Inc.) dose accumulation algorithm for adaptive planning using data from MOSFET dosimeters implanted in the prostate. Methods: Under a previously approved IRB protocol, prostate cancer patients were implanted with MOSFET dosimeters (Dose Verification System (DVS) by Sicel Technologies) and treated with daily CBCT. Daily readings were compared to dose predictions generated by an automated dose accumulation workflow (MIM Software) for five patients (179 total fractions): (1) contours from the planning CT (PCT) were rigidly transferred to the day 1 CBCT (CBCT1), (2) contours on CBCT1 were manually reviewed by the treating physician, (3) contours for each subsequent fraction (CBCTf) were deformably transferred from CBCT1, (4) planning dose was rigidly applied to CBCTf, (5) dose was accumulated. Results: The MIM workflow was efficient and applicable in a clinical setting. When comparing the MIM readings to the daily DVS readings, 53% fell within 3% of the measured dose, 80% fell within 5% and only 0.8% were greater than 10% from the measured dose. The largest deviations from the expected dose found in the MIM readings resulted from difficulties in registering of the CBCTs due to artifacts in the images. Conclusion: The MIM workflow was able to accurately predict the dose to the DVS despite inferior image quality with CBCT. Rigid dose registration was used to avoid unrealistic dose deformations, but this approach does not take into account changes in external contour. To further assess the efficacy of the workflow for adaptive planning and dose accumulation, the original treatment plan will be applied to the daily CBCT with the deformed contours. Additional dosimetric endpoints will be analyzed on deformable structures such as the PTV and OARs. Sara Pirozzi is an employee at MIM Software, Inc.
SU‐E‐CAMPUS‐T‐01: Results of Irradiations Performed On Radiological Physics Center's Anthropomorphic Lung Phantom and Respiratory Simulating Motion Table
Authors: Alvarez P , Molineu A , Amador C , Nguyen T , Followill D
Published: July 2013

Purpose: To present the results of the irradiations performed on Radiological Physics Center's anthropomorphic lung phantom using a respiratory simulating motion table. Methods: The RPC's lung phantom is used to credential institutions to participate in NCI sponsored lung clinical trials. When institutions use breath hold, gating, ITV or tracking techniques to account for patient motion, a motion table was included with the phantom. The institutions designed and delivered 3D or IMRT plans that covered an ovoid shaped target located in the left lung. All irradiations in this analysis included heterogeneity dose calculation algorithms approved by the RTOG. The TLD criteria were ±5% about RPC/Inst=0.97 (about 1.00 for Monte Carlo algorithms). Before March 2012 the film criteria required a DTA <=5 mm in the fall off regions of orthogonal profiles taken through the center of the target. After March 2012 the film criteria changed to require >=80% of the pixels in the ROI in each plane to pass a 5%/5mm gamma calculation. The average of the 3 planes must be >=85%. Results: The lung phantom was irradiated 427 times by 304 institutions. 124 institutions irradiated it 157 times using the motion platform. 79% of the irradiations utilizing the motion platform and 87% of the static irradiations passed the criteria. The overall pass rate for the phantom is 84%. Thirty percent of the moving phantom failures and 67% of the static phantom failures were due to failing solely the film criteria. 4 of 4 (100%) breath hold irradiations, 54 of 68 (79%) gating irradiations, 43 of 61 (70%) ITV irradiations and 23 of the 24 (96%) tracking irradiations passed the criteria. Conclusion: The moving phantom has a pass rate that is statistically significantly different than that for a static phantom. Supported by PHS grant CA10953 and CA081647 from the NCI, DHHS.
SU‐E‐CAMPUS‐T‐05: Experimental Characterization of Two‐Dimensional Pencil Beam Scanning Proton Spot Profiles
Authors: Lin L , Ainsley C , McDonough J
Published: July 2013

Purpose: Dose calculation of pencil‐beam scanning treatment plans relies on the accuracy of proton spot profiles; not only the primary component but also the broad tail components. A pair/magnification method is applied to EBT3 films to generate primary and tail components of two‐dimensional spot profiles and dose kernels. Methods: Four films are taken at multiple locations in air and multiple depths in Solidwater for six selected energies from the IBA universal nozzle. The films used for the primary component are exposed to 50–200 MU to avoid saturation. The films used for tail components are exposed to 800, 8000 and 80000 MU. By merging these data, dose kernels down to 10−4 of central spot dose can be generated. In‐house programs are developed to calculate the total dose from multiple spots in each treatment field at all in‐air locations and phantom depths based on the constructed dose kernels. Integration of these kernels from zero to 40 mm radius is used to evaluate the charge missed by the PTW Bragg peak chamber during integral depth‐dose measurements. Results: Measurement agrees within 1% of calculation for output versus field size using dose kernels. The asymmetric comet‐shaped profile tails have a bigger impact at superficial depths and low energies. This output difference between two orientations at the surface of a rectangular field of 40 mm by 200 mm, a typical cranialspinal field, is about 2%, which persists until a depth of 50 mm and drops to 1% at the end of range. The charge deficit in the Bragg peak chamber varies < 2% from entrance to the end of Bragg peak for energies < 180 MeV, but exceeds 5% at 225 MeV. Conclusion: Application of the pair/magnification method to EBT3 films shows the evolution of two‐dimensional composite spot profiles in air and dose kernels in phantom. This work was supported by the US Army Medical Research and Materiel Command under Contract Agreement No. DAMD17‐W81XWH‐04‐2‐0022. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the US Army.
SU‐F‐500‐01: Towards Personalized Dosimetry Using Diapeutic Radiopharmaceuticals
Authors: Besemer A , Grudzinski J , Titz B , Wickre P , Hall L , Weichert J , Bednarz B
Published: July 2013

Purpose: he efficacy of targeted radionuclide therapy (TRT) depends on the ability to accurately characterize the absorbed dose distribution within tumors as well as other potential dose limiting organs. Clinical data suggests a compelling need for personalized dosimetry given that conventional dose calculation methods fail to accurately predict dose response relationships. This work describes the implementation of a Monte Carlo patient‐specific 3D dosimetry platform for TRT. Methods: CLR1404, a small‐molecule, phospholipid ether analog can serve as a ‘diapeutic’ (diagnostic and therapeutic) agent for the detection and treatment of multiple solid tumors. Because both the I–124 labeled imaging and I–131 labeled therapy agent are administered in similar mass doses, they are expected to display equivalent in vivo pharmacokinetic profiles. Therefore, the 124I‐CLR1404 distribution can be converted to the therapeutic 131I‐CLR1404 distribution by simply accounting for the difference in decay rates. In this study, high grade Glioma patients were scanned at 4.5, 24, and 48 hours post injection of 124I‐CLR1404. PET, CT and MRI images were co‐registered, resampled to the CT resolution and contoured. The 131I‐CLR1404 dose deposition throughout the CT volume was simulated using the Monte Carlo code Geant4.9.4 assuming a source strength in each voxel was proportional to the PET activity. The total cumulated absorbed dose was calculated by numerically integrating the activity over all time on a voxel‐by‐voxel basis. Results: Spatial distributions of the absorbed dose rates, DVHs, and mean, minimum, maximum, and total dose rate values for each contoured region were generated for each time point, clearly illustrating CLR1404's pharmacokinetic properties. The mean cumulated absorbed dose within tumor was 52.3 mGy per injected activity of 131I‐CLR1404. Conclusion: This work demonstrates that a Geant4 based Monte Carlo radiopharmaceutical dose calculation platform is not only feasible, but can serve as invaluable tool for personalized dosimetry in TRT. JJG and JPW are affiliated with Novelos Therapeutics which owns the licensing rights to CLR1404 and related compounds.
SU‐F‐500‐06: Demonstration of a Planning Scheme for Emission Guided Radiation Therapy (EGRT) in a Metastatic Breast Cancer Patient
Authors: Fan Q , Nanduri A , Yang J , Yamamoto T , Loo B , Graves E , Zhu L , Mazin S
Published: July 2013

Purpose: Emission guided radiation therapy (EGRT) is a new modality that uses PET emissions in real‐time for direct tumor tracking during radiation delivery. Radiation beamlets are delivered along PET lines of response (LOR' s) by a fast rotating ring therapy unit consisting of a Linac and PET detectors. The feasibility of tumor tracking has been demonstrated previously. In this work, we develop a planning scheme for EGRT to accomplish sophisticated intensity modulation based on an intensity modulated radiation therapy (IMRT) plan while preserving tumor tracking. Methods: To incorporate the IMRT plan into EGRT treatment, we sample EGRT's detection and delivery space into 3D parallel sinogram space. Planning modulation is achieved via generating an LOR response probability distribution in the same sinogram space, which accounts for attenuation correction, PET activity normalization, and a modified IMRT plan. The IMRT plan is optimized for a planning target volume that encompasses the tumor motion. Evaluation studies are performed on a 4D digital patient as well as a clinical breast cancer patient with moving tumors in the lung. The Linac dose delivery is simulated using a Monte Carlo algorithm. Emission data are obtained using GATE and a commercial PET scanner. Results: Compared with the 3D IMRT treatment which covers the same PTV based on the same IMRT plan, EGRT achieves a 15.1%, 15.2% relative increase in dose to 95% of the gross tumor volume (GTV) and a 31.8%, 20.7% increase to 50% of the GTV for the digital and clinical patients, respectively. The organs at risk doses are kept similar or lower for EGRT in both cases, with tumor tracking preserved. Conclusion: With the capabilities of incorporating planning modulation and accurate tumor tracking, EGRT has the potential to enable a practical and effective implementation of 4D biologically guided radiation therapy for planning and delivery. This work is supported by Georgia Institute of Technology new faculty startup fund, RefleXion Medical and the National Cancer Institute (R43CA153466). SRM, ASN and LZ have financial interest in RefleXion Medical. BWL receives speaking honoraria from Varian and research support from Varian, Philips, and RaySearch Labs.
SU‐F‐500‐10: Targeted Delivery of Microbeam Irradiation and Initial Mouse Brain Tumor Model Studies Using a Table Top MRT System
Authors: Zhang L , Yuan H , Hadsell M , Burk L , Inscoe C , Chtcheprov P , Lee Y , Lu J , Chang S , Zhou O
Published: July 2013

Purpose: Microbeam radiation therapy (MRT) is an experimental and preclinical radiotherapy method for cancer treatment that has been shown, in animal studies, to have the capability to selectively eradicate tumor without damaging normal tissue functions. The reliance of MRT on synchrotron radiation has prevented widespread research in this field and is a major roadblock for future clinical applications. Our goal is to develop a compact image‐guided MRT system based on high power distributed x‐ray source array and explore the radiobiology behind MRT using various mouse brain tumor models. Methods: We developed a novel protocol of combined MRI/x‐ray radiograph image‐guided MRT which enables irradiating two mice simultaneously. This protocol proceeds as follows: tumor localization with MRI, landmark identification with x‐ray projections, registration between the two images to determine the relative location of the tumor in the RT coordinate space, and treatment with the microbeam irradiator. We evaluated the targeting accuracy and tumor cell response of the protocol with U87 MG human glioma tumor bearing mice using γ‐H2AX staining. A survival study of U87 human glioma tumor bearing mice treated with three‐microbeam MRT (32Gy/beam) was carried out using this protocol. Results: The average targeting accuracy measured in the γ‐H2AX stained slices was about 280 μrn which is well below our beamwidth (350 μrn). In the survival study, U87 tumor mice treated using this MRT protocol showed an average survival time of 45 days, an extension of 6 days compared with 39 days in the control group. Conclusion: The initial tumor mice studies have demonstrated the feasibility of MRI/x‐ray radiograph guided MRT treatment in animal research. We believe this image‐guide MRT protocol could enable more efficient animal experiments with various brain tumor models to better understand MRT mechanisms.
MO‐A‐500‐01: Future of Radiation Therapy Safety
Authors: Low D , Mutic S , Moore K
Published: July 2013

Radiation therapy has undergone considerable changes in the past 20 years. The complexity of radiation therapy treatments has increased and there has been a corresponding response by medical physicists to adopt new techniques to assure that treatments are safely delivered. Quality assurance equipment manufacturers have developed devices that substantially aid the medical physicist in measurement and analysis of treatments. The radiation therapy delivery device manufacturers have also stepped in, modifying their traditional approach to device manufacturing and providing extensive equipment operation recording and to a lesser extent reporting. Treatment planning system vendors have also provided tools to aid medical physicists in developing critical treatment planning quality assurance processes. This symposium examines some of the current quality assurance technology research. It presents research into tools that will provide the treatment planner insights regarding the absolute quality of a specific treatment plan, methods for automatically and redundantly assuring that the proper patient is being treated in the proper location, in highly automated redundant checks of treatment plan delivery quality. Many of the techniques that will be described are looking for rare but potentially catastrophic errors, including human error, process errors, equipment failure, and software bugs. One of the challenges for designing and implementing these techniques includes the assumption that there will be little or no additional manpower available to implement and monitor these techniques. Therefore, most of the presented research will utilize autonomous functions and workflows that either involve no additional manpower efforts or improve the efficiency of existing efforts.

Learning Objectives:

1. Teach the challenges that medical physicists face in an ever increasingly complex medicine.

2. Show examples of novel quality assurance technologies that improve the stability and quality of treatment plans.

3. Show examples of autonomous software and quality assurance workflows that monitors the treatment planning and delivery process to identify errors.

4. Show examples of techniques that expand the ability of medical physicists to provide expert advice.
MO‐A‐103‐01: Nuclear Medicine: Regulatory Guidelines and Computational Methods for Safe Release of Radioactive Patients
Authors: Wendt R , Mourtada F
Published: July 2013

Radiation therapy using radioactive materials within the patient, i.e., permanently implanted sealed brachytherapy seeds and unsealed targeted radiopharmaceuticals, is routinely used to treat cancer patients. Radioactive patients may safely be released from radiation safety restrictions when the most exposed person is unlikely to receive more than 5 mSv (500 mrem) according to the United States Nuclear Regulatory Commission. NUREG 1556 Volume 9 Appendix U Revision 2 presents regulatory guidance that may be used to assure compliance with this limit. This risk‐based approach is a big step forward from the prior activity‐based release criteria. This session will introduce commonly used radiation therapies using internal sealed and unsealed radioactive sources and discuss the criteria and computational methods for the safe release of radioactive patients. Essential components of NRC Part 35 Medical Use of Byproduct Material will also be presented.

Learning Objectives:

1. Introduce commonly used radiation therapies involving internally administered radioactive materials

2. Present NRC guidelines and perform the calculations in the regulatory guidance documents

3. Understand the implications and limitation of the release criteria calculation
MO‐A‐137‐05: Assessment and Prediction of Treatment Plan Quality Through Integrated Planning Script
Authors: Cao M , Ruan D , DeMarco J , King C , Kupelian P , Wang J , Low D
Published: July 2013

Purpose: To identify plan quality prognostic features that can be used to improve treatment plan quality and intra‐and inter‐planner consistency using a self‐evolving institutional treatment planning workflow that employs treatment‐planning scripts. Methods: Institution‐specific plan quality analysis software was developed using scripting integrated with a commercial treatment planning system (TPS). During treatment plan review, the script automatically extracted a set of representative quantities derived from dose volume histograms (DVH). The quantities were compared against national published standards and institution‐specific criteria generated from statistics of accumulated planning data to assist in plan evaluation or further optimization. After plan acceptance, the plan quality indices and patient specific parameters, such as DVH endpoints and geometric features, were extracted by the script and saved into an evolving treatment plan database to update the existing institution‐specific planning statistics. Results: A treatment‐planning database was constructed using a group of prostate patients (n=48) and following the proposed workflow. Dosimetric indices and geometric features were exacted and analyzed. For example, the PTV and OAR overlap volumes consistently provided good prognostic power for plan quality prediction. Retrospective analysis of the prostate planning database showed a consistent PTV volume coverage (PTV‐V100 of 94.9±1.09%). No significant difference in PTV volume coverage was found for different prescription levels or target size. A conformity index (V50/VPTV) of 3.51±0.26 was achieved for prostate‐only treatment plans. Strong correlations (R>0.8) were observed between OAR dose volume indices (Rectum V70Gy, V65Gy and Bladder V70Gy, V65Gy) and the OAR and PTV overlapping volumes. Conclusion: The feasibility of automatic treatment plan quality aggregation, analysis and consistency improvement using planning scripts integrated into the treatment planning system was demonstrated in this pilot study. It is being incorporated into the clinical routine in our institute to determine its full utility.
MO‐A‐108‐01: The Impact of Intensity Modulated Proton Therapy On Proton Therapy?
Authors: Chen R , Bortfeld T , Kruse J , Zhang X , Chang J
Published: July 2013

One of the major controversies surrounding proton therapy is that despite the high cost of proton therapy relative to conventional x‐ray radiotherapy, the clinical benefit of proton therapy has not been clearly demonstrated in the literature. The majority of clinical studies comparing proton and photon therapy have compared passive scattering proton therapy (PSPT) with intensity‐modulated radiation therapy (IMRT). However, the delivery of proton therapy, while predominantly in the form of PSPT, is likely to be superseded by intensity modulated proton therapy (IMPT). Improvement in dose distribution by IMPT in a representative series of patients compared to IMRT has been reported. It appears that IMPT will have the opportunity to justify adopting the proton therapy in the routine care for majority disease.This session will begin with a short introduction explaining the current state of the art for IMPT. This introduction will be followed by four presentations. The first presentation will cover the efficacy of proton therapy for prostate cancer from a clinician's point of view. The second presentation will provide more detail on the current state of the art for proton therapy, introduce future research directions for IMPT technology, and address the impact of the research on proton therapy. The third presentation will cover the clinical and operational reasoning behind an all‐scanning‐beam facility and the expertise needed to build such a facility. In the fourth presentation, a physicist and a physician will present their center's experience with implementing IMPT techniques for lung, head and neck, and central nervous system tumors and present relevant clinical protocols and data.

Learning Objectives:

1. Describe the current machine delivery systems and treatment planning, quality assurance, and dose verification techniques for IMPT.

2. Explain the clinical efficacy and cost‐effectiveness of proton therapy.

3. Differentiate the capabilities of IMPT from those of PSPT and IMRT and explain how the unique capabilities of IMPT improve the clinical efficacy and cost‐effectiveness of proton therapy.

4. Provide examples of working clinical protocols, workflow, and quality assurance procedures for the use of IMPT in routine patient care.
MO‐A‐WAB‐01: MRI‐Guided Radiation Therapy
Authors: Jaffray D , Mutic S , Fallone B , Raaymakers B
Published: July 2013

The concept of integrating a magnetic resonance imaging (MRI) scanner with a therapy radiation source, either a therapy linear accelerator (linac) or 60 Co, emerged as a feasible novel approach for MRI‐guided radiation therapy (i.e. MRIgRT or MRgRT) in recent years. The main motivation for the technological development of such radiotherapy systems is to provide state of the art MR imaging inside the treatment room to guide the treatment delivery. MRI offers the capability to visualize soft‐tissue as well as to perform physiological assessment of healthy and tumor tissues. The aim of MRIgRT is to facilitate adaptive radiotherapy by using on demand MRI data to update and personalize patient treatments.The MRI‐linac/ 60 Co system integration is a challenging task due to the intrinsic default incompatibility between the sub‐components. Multiple interdependent issues need to be resolved in order to achieve the optimal operation of the MRI scanner and the radiation source(s) such as: a) radiofrequency (RF) interference, b) magnetic field coupling, c) perturbation of the dose deposited in tissue due to the presence of an external magnetic field, and d) escalation of patient skin dose. This translates into solving a complex optimization problem which drives the overall system architecture. The session will provide an overview of the MRI‐guided radiation therapy systems. The speakers will present the specifics of their proposed designs and the latest technological developments (hardware and software). They will also discuss key aspects related to the clinical implementation of their systems such as safety, applications, workflows, quality control, staffing models for supporting the infrastructure, and preliminary data.

Learning Objectives:

1. Understand the main concepts of MRI‐guided radiation therapy;

2. Understand the issues and proposed solutions related to the integration of MRI‐guided radiotherapy systems;

3. Understand the advantages and limitations of MRI‐guided radiotherapy systems.
MO‐A‐141‐01: Memorial to Fearghus O' tFoghludha ‐ Memorial Lecture
Authors: Samei E
Published: July 2013

Medical Physics community lost one of its prominent members, Fearghus O' tFoghludha, in July 2012. Fearghus O' tFoghludha was the editor of Medical Physics from 1985 to 1987 and the President of the AAPM from 1971 to 1972. Born in 1927 in Dublin, Fearghus studied at University College Dublin, National University of Ireland, Royal University of Uppsala (Sweden), and the University of Lund (Sweden). He served as Senior Physicist at St. Luke's Hospital in Dublin and the head of Radiation Physics at the Medical College of Virginia till 1970 when he joined Duke University. Noteworthy among his accomplishments are the design and optimization of modern mammography equipment, and the design of an experiment on solar radiation for the Apollo 13 lunar mission. He was one of the pioneers in designing imaging equipment so that radiation dose can be minimized. During his distinguished career, he had working affiliation with the Oak Ridge National Lab, NIH, NSF, ACR, the Atomic Energy Commission, CERN, and NASA.
MO‐A‐141‐02: Session In Memory of Fearghus O't Foghludha – Virtual Tools for Validation of X‐Ray Breast Imaging Systems
Authors: Bakic P , Myers K , Reiser I , Kiarashi N , Zeng R
Published: July 2013

Given the large number of design parameters available to an x‐ray imaging system innovator (x‐ray spectrum, number of projection angles, angular range, dose and reconstruction algorithm, to name a few), simulation methods offer significant advantages over clinical studies for evaluation of the alternatives in terms of reproducibility, reduced radiation exposures of patients and volunteers, a known reference standard, and the capability for studying patient and disease subpopulations through appropriate choice of breast and patient model parameters. For these reasons, the emergent use of Virtual Clinical Trials for preclinical assessment of x‐ray breast imaging methods has introduced a demand to optimize protocols for simulation studies. The protocols should comprise of specifications for breast phantoms, the simulated data representation, methods for incorporating phantoms into a model for the imaging process, and appropriate statistical assessment methods applied to the resulting simulated images. This symposium explores simulation methods for evaluation of novel x‐ray breast imaging systems — the subject of recently established AAPM taskgroup TG234. The focus is on the various approaches of developing software anthropomorphic phantoms and their use in the statistical assessment of novel imaging systems along with computational models for the x‐ray image formation process. The symposium will review and discuss the state of the science of Virtual Clinical Trials for novel x‐ray breast imaging systems. Presentations will discuss real‐time simulation of breast anatomy, simulation of small‐scale tissue properties, generation of breast phantoms based upon clinical datasets, and task‐based evaluation of x‐ray breast imaging systems using software phantoms.

Learning Objectives:

1. Review current approaches for simulation of breast phantoms for x‐ray imaging, along with their strengths and limitations;

2. Understand the validation of software phantoms using object and image statistics;

3. Review methods for statistical and task‐based image quality assessment and discuss their applications in x‐ray breast imaging systems;

4. Illustrate methods for performing virtual clinical trials of emerging 3D x‐ray breast imaging systems.

P.R.B. is a PI on NSF grant IIS0916690 and co‐investigator on NIH R01 CA154444, NIH R21 CA155906‐01A1, and DoD HBCU PTA BC083639, and is also involved in research collaboration with Barco, Inc. and Hologic, Inc.

N.K. is funded by NIH R01 CA134658 and R01 CA11243, and is involved in resaerch collaboration with Siement Medical Solution.
MO‐A‐144‐02: Workshop
Authors: Sammet S , Lu Z
Published: July 2013

List of the companies who have promised to support the workshop:

1. Philips MR guided HIFU. (Contact person: Lizette Warner, Ph.D., 595 Miner Rd Cleveland, OH 44143, Tel: (440) 483‐3000, e‐mail: Lizette Warner@philips.com)

2. InSightec Ltd. ( Contact person: James E. Davis, Chief Executive Officer, 10501 W Research Dr., Ste G100, Milwaukee, WI 53226, Tel: (262)613‐4212, email: jamesd:jamesd@Insightec.com@Insightec.com :jamesd@Insightec.com)

3. US HIFU, LLC (Contact: Naren Sanghvi, Chief Scientific Officer, 4000 Pendleton Way, Indianapolis, IN 46226. Email: narensanghvi :narensanghvi@ushifu.com@ushifu.com :narensanghvi@ushifu.com, Phone: 317‐352‐5812.)

4. Alpinion Medical Systems (Contact person: Yuchi Chu, Director, Suite 229, 10604 NE 38th Place, Kirkland, WA 98033, tel: (425) 949‐4907, email: ychu :ychu@alpinionus.com@alpinionus.com :ychu@alpinionus.com)

5. FUS Instruments Inc. (Contact person: Daniel Pajek, VP, Operations, (647)238‐7146, email: dpajek :dpajek@fusinstruments.com@fusinstruments.com :dpajek@fusinstruments.com>)