bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐T‐516: Dosimetric Validation of AcurosXB Algorithm in Comparison with AAA & CCC Algorithms for VMAT Technique
Authors: Kathirvel M , Subramanian V Sai , Arun G , Thirumalaiswamy S , Ramalingam K , Kumar S Ashok , Jagadeesh K
Published: June 2012

Purpose: To dosimetrically validate AcurosXB algorithm for Volumetric Modulated Arc Therapy (VMAT) in comparison with standard clinical Anisotropic Analytic Algorithm(AAA) and Collapsed Cone Convolution(CCC) dose calculation algorithms. Methods: AcurosXB dose calculation algorithm is available with Varian Eclipse treatment planning system (V10). It uses grid‐based Boltzmann equation solver to predict dose precisely in lesser time. This study was made to realize algorithms ability to predict dose accurately as its delivery for which five clinical cases each of Brain, Head&Neck, Thoracic, Pelvic and SBRT were taken. Verification plans were created on multicube phantom with iMatrixx‐2D detector array and then dose prediction was done with AcurosXB, AAA & CCC (COMPASS System) algorithm and the same were delivered onto CLINAC‐iX treatment machine. Delivered dose was captured in iMatrixx plane for all 25 plans. Measured dose was taken as reference to quantify the agreement between AcurosXB calculation algorithm against previously validated AAA and CCC algorithm. Gamma evaluation was performed with clinical criteria distance‐to‐agreement 3&2mm and dose difference 3&2% in omnipro‐I'MRT software. Plans were evaluated in terms of correlation coefficient, quantitative area gamma and average gamma. Results: Study shows good agreement between mean correlation 0.9979±0.0012, 0.9984±0.0009 & 0.9979±0.0011 for AAA, CCC & Acuros respectively. Mean area gamma for criteria 3mm/3% was found to be 98.80±1.04, 98.14±2.31, 98.08±2.01 and 2mm/2% was found to be 93.94±3.83, 87.17±10.54 & 92.36±5.46 for AAA, CCC & Acuros respectively. Mean average gamma for 3mm/3% was 0.26±0.07, 0.42±0.08, 0.28±0.09 and 2mm/2% was found to be 0.39±0.10, 0.64±0.11, 0.42±0.13 for AAA, CCC & Acuros respectively. Conclusions: This study demonstrated that the AcurosXB algorithm had a good agreement with the AAA & CCC in terms of dose prediction. In conclusion AcurosXB algorithm provides a valid, accurate and speedy alternative to AAA and CCC algorithms in a busy clinical environment.
SU‐E‐T‐517: Characterization of Relative Doses and Source Strengths for Various Plaque Sizes and Tumor Dimensions in the Treatment of Uveal Melanoma
Authors: Esquivel C , Stathakis S , Gutierrez A , Papanikolaou N
Published: June 2012

Purpose: To characterize the relative doses and source strengths for various eye plaque sizes and tumor dimensions in the treatment of uveal melanoma. Materials and Method: Several tumors with basal diameters ranging from 6–16mm and apical height of 5–10mm were planned using the Pinnacle3 treatment planning system following the American Brachytherapy Society's recommendations. The data is based on 5‐day implant to deliver 85Gy with a dose rate of 70.9cGy/hr. Choice of plaque size is based on a 2–3 mm margin on either side of the tumor. Doses to the fixed locations: sclera, center of the eye and opposite sclera were obtained. Results: From our results we see larger source strengths needed for smaller plaques due to smaller number of sources used. The exception is with 14mm and 16mm plaques containing the same number of sources where the 16mm plaque has slightly higher source strengths. For both the inner and outer sclera, the relative dose increases with increasing height. For a 12mm plaque, the relative dose of the outer sclera increases from 4–10 times that of the Rx dose at the apex of the tumor. For a 20mm eye plaque, the relative dose of the outer sclera increases from 2–5 times that of the prescription dose at the apex of the tumor. As apical height increases, the relative dose at the center of the eye increases to about 75% of the Rx dose at 10cm depth for all plaque sizes. At the inner sclera surface opposite the center of the tumor base the relative dose is 20–22% of the Rx dose for all plaque sizes. Conclusion: The data provided will be a helpful tool in evaluating and predicting complications in the retina and sclera based on the tumor dimensions and selected plaque size.
SU‐E‐T‐525: Dosimetric Validation of the Algorithm Based on Linear Boltzmann Transport Equations for Photon 4MV Dose Calculation
Authors: Sato S , Miyabe Y , Nakata M , Tsuruta Y , Nakamura M , Mizowaki T , Hiraoka M
Published: June 2012

Purpose: To evaluate a dosimetric accuracy of AcurosXB dose calculation algorithm for 4 MV photon beam. Methods: Four MV beam (Clinac‐6EX) and AAA and AcurosXB algorithms (pre‐release version 11.0.03.) were used in this study. The differences of the calculation with AAA (EAAA) and AcurosXB (EAXB) to the measurement were evaluated in the depth doses to 25 cm depth and dose profiles within the water and slab phantoms (water, lung and bone equivalent). In addition, the clinical cases, including three whole breast plans and three head and neck IMRT plans, were evaluated. First the AAA plans were calculated, then AcurosXB plans were recalculated with dose‐to‐medium with identical beam setup and monitor units as in the AAA plan. Results: In the water phantom study, the EAAA and EAXB were up to 2.2% and 1.5% in the depth doses for the open field (field size = 4 − 40cm square), respectively. Under the heterogeneity conditions, the EAAA and EAXB were less than 4.4% and 2.2% in lung region, and less than 12.5% and 6.3% in bone region, respectively. In the re‐buildup region after passing through the lung phantom, the AAA overestimated the doses about 10%; however AcurosXB had good agreement with measurement within 3%. Dose profiles with AcurosXB were better agreement with measurement than AAA. In the clinical cases, the dose of the skin surface region with AcurosXB were higher than AAA by at least 10%, and the dose differences over 5% appeared in heterogeneous region. However, DVH shapes of each organ were similar between AAA and AcurosXB within 2%. Conclusions: In phantom study, AcurosXB had better agreement to measurement than AAA, especially in heterogeneous region and re‐buildup region. In the clinical cases, there were large differences between AcurosXB and AAA in the surface region. Evaluation Agreement of non‐clinical versions of Acuros XB withã€€Varian Medical Systems.
SU‐E‐T‐526: Evaluation of Dose Mapping Errors via Use of a Volume‐Based Dose Mapping Method
Authors: Chen H , Saleh‐Sayah N , Watkins W , Yan C , Salguero F , Heath E , Siebers J
Published: June 2012

Purpose: To quantify dose mapping errors (DMEs) of a point‐based dose mapping method for 4D lung treatment plans. Methods: Point‐based dose mapping methods utilize deformation vector fields (DVFS) to interpolate dose from a deformed image. Volume‐based dose mapping methods consider the volume overlap between deformed and reference voxels; defining dose as the integral energy divided by the integral mass of the voxel, and conserving integral dose . DME is defined as the dose differences between volume‐based and point‐based mapped dose (DME=(DpointBased‐DvolumeBased)/DRx). The DME for a 4D lung case is compared with a bitmap DME method, both using a Pinnacle research version 8.1y DVF. DME is computed for ten 4D lung cases (five 10 phases, five 3 phase) with Pinnacle research version 9.100 DVFs. Multi‐phase accumulated 4D DMEs are also evaluated. Results: For all cases, the largest DMEs are located in the dose/density gradient regions. With Pinnacle 8.1y DVF, mapping dose from phase 9 to phase 0, results in a DME=−0.2%±6.1% (range of −76%∼112%). The same case with Pinnacle 9.100 DVFs, DME=0.3%±4.8%(−41%∼32%). Locations of large DME are consistent with those from the bitmap method. For the ten 4D lung cases, accumulated mean DME are within ±0.07% (std. deviations: 1∼5%, range −102%∼64%). Maximum tumor DMEs are less than 30cGy (DRx=7200cGy) for all patients. Conclusions: Due to its inherent integral dose conservation, volume‐based dose mapping methods can quantify errors in point‐based dose mapping methods. While mean DME values are small for the cases tested, standard deviations near 5% indicate that a substantial number of voxels have ∼5% dose mapping errors, however these dose errors do not occur in the target structures. Work supported by NIH P01CA116602
SU‐E‐T‐528: Appraisal of Acorus XB and Convolution Dose Algorithms in Field Junction of Breast Tangential/superclavicular Fields
Authors: Han T , Tailor R , LaNeave S , Howell R , Mourtada F , Salehpour M
Published: June 2012

Purpose: Dose accuracy injunction regions of breast‐tangential therapy is a challenge, and inaccurate dose predictions may lead to unreal hot/cold spots. Availability of the novel deterministic radiation transport method Acuros XB (AXB) provides a potential for more accurate dose predictions. This study assesses relative dose accuracies of this and the widely used other algorithms: collapsed cone convolution (CCC) and anisotropic analytical algorithm (AAA) against film measurements. Methods: A typical tangential and superclav fileld combination was planned for an anthropomorphic body phantom using Pinnacle‐9.0 treatment‐planning system (TPS). The created plan employing 6MV beam was delivered to the phantom on a Varian linac. In region of the field junction of tangentials & superclav, films (EBT2) were placed in coronal planes at two depths (∼ 2 and 4 cm). Optical density was measured along and ± 5mm away from the field‐match line, and converted to dose using film‐calibration curve specific to the batch of film. The same plan was also imported to Eclipse TPS using an import filter written in MATLAB. Algorithms Pinnacle CCC 9.0, Eclipse AAA 10.0.24 and AXB 11.0.3 were used for calculations. Comparison of the measured doses (assumed as gold standard) against doses calculated from planning‐systems were preformed in a MATLAB platform. Results: In general, dose distributions from all three TPS algorithms are found to agree closely with film data. Agreements between AXB and CCC dose calculations were found to be reasonable. AXB appears to be better in modeling the backscatter effects in the heterogeneous regions. AAA calculations gives acceptable results, but with less accuracy compared to CCC and AXB. Conclusions: The novel deterministic algorithm AXB in Eclipse is found to provide better agreement with measured data in breast‐tangential therapy. Benefits of using Acuors XB algorithm in tangential fields planning requires further investigation. This work was funded by National Institutes of Health through grant 2R44CA105806‐02 and MD Andersonâ€™s Cancer Center Support Grant CA0 16672
SU‐E‐T‐530: Relative Electron Density Phantom Comparison
Authors: Rasmussen B , Chu K , Tong S
Published: June 2012

Purpose: Modern treatment planning systems require lookup tables to convert Hounsfield Units (HU) to relative electron density (RED) for use in heterogeneity corrections during dose calculations. The purpose of this work is to illustrate the impact of using different model CT phantoms to determine HU to RED curves for treatment planning. Methods: A GAMMEX model 467 tissue characterization phantom and a CATPHAN model 500 multipurpose CT phantom were imaged using CT scanners in four different cancer centers and the HU to RED curves derived from each phantom were imported into an Eclipse 8.10 treatment planning system. Dose calculation were performed on a heterogeneity phantom and then compared to measurements. A comparison of isodose and DVH were performed by calculating 3D and IMRT plans onto identical CT datasets with different HU to RED curves to determine the clinical significance. Analysis based on effective atomic number of the phantom inserts was also performed. Results: The HU to RED curves from the GAMMEX and CATPHAN phantoms were found to be reasonably self‐consistent across the different CT scanners. However, observable differences for higher density materials were observed between the two phantom models. The differences for the larger HU values can be attributed to the effective atomic number of the materials. In kV range of a CT scanner x‐ray spectrum, photon interactions are partially due to the photoelectric effect which has a larger dependence on atomic number than Compton scatter which depends most directly on electron density. Conclusion: The HU to RED curve is more dependent on the phantom model than CT scanner. The HU to RED curve from the GAMMEX phantom produced better agreement between Eclipse AAA calculations and measured dose distributions on a heterogeneity phantom than that from the CATPHAN. However, DVH and isodose data on patient plans show small differences for common treatment sites.
SU‐E‐T‐532: Comparison of Dose Distributions Calculated Using Different Planning Systems with Radiochromic Film Measurements in an Inhomogeneous Phantom
Authors: Lovelock D , Lim S , Yorke E , Kirov A , LoSasso T
Published: June 2012

Purpose: Accurate modeling of the dose distribution in a lung tumor is challenging for traditional dose calculation algorithms. We compare the dose distributions of four commercial dose calculation Methods: Raysearch (Raysearch Laboratories) and Pinnacle (Philips Healthcare) collapsed cone, and Eclipse AAA and Eclipse Acuros,(Varian Medical Systems) with measurements using radiochromic film in a lung tumor phantomMethods: A simple lung tumor phantom was constructed using a thermoplastic cylinder 29 mm diameter and 40mm in length (density 1.3 gm/cc) imbedded in cork phantom 25 × 25 × 20 cm of density 0.32 gm/cc. Nine film layers normal to the axis of the cylinder where placed between layers of cork, above, below and through the cylindrical inhomogeneity. The phantom was irradiated with a single asymmetric 10×10 cm 6 MV field with the central axis collinear with the cylinder axis. Thirteen film exposures at 5 cm depth taken with doses 0–10 Gy were used to calibrate the film. The phantom was CT scanned and the DICOM study loaded into each of the treatment planning systems to calculate the dose distribution in the phantom. Results: Away from cork‐poly interfaces, agreement between the four algorithms was within 3% of the film measurements. For Acuros, the dose at the edge of the cylinder was found to be up to 2% lower than that at the center of the cylinder possibly because of the loss of lateral electron equilibrium. Conclusions: All four algorithms achieved remarkable agreement with the radiochromic film measurement. The Acuros algorithm appeared to more accurately model the peripheral dose deficit in the tumor, although a more detailed study is required for confirmation.
SU‐E‐T‐535: Proton Dose Calculations in Homogeneous Media
Authors: Chapman J , Fontenot J , Newhauser W , Hogstrom K
Published: June 2012

Purpose: To develop a pencil beam dose calculation algorithm for scanned proton beams that improves modeling of scatter events. Methods: Our pencil beam algorithm (PBA) was developed for calculating dose from monoenergetic, parallel proton beams in homogeneous media. Fermi‐Eyges theory was implemented for pencil beam transport. Elastic and nonelastic scatter effects were each modeled as a Gaussian distribution, with root mean square (RMS) widths determined from theoretical calculations and a nonlinear fit to a Monte Carlo (MC) simulated 1mm × 1mm proton beam, respectively. The PBA was commissioned using MC simulations in a flat water phantom. Resulting PBA calculations were compared with results of other models reported in the literature on the basis of differences between PBA and MC calculations of 80–20% penumbral widths. Our model was further tested by comparing PBA and MC results for oblique beams (45 degree incidence) and surface irregularities (step heights of 1 and 4 cm) for energies of 50–250 MeV and field sizes of 4cm × 4cm and 10cm × 10cm. Agreement between PBA and MC distributions was quantified by computing the percentage of points within 2% dose difference or 1mm distance to agreement. Results: Our PBA improved agreement between calculated and simulated penumbral widths by an order of magnitude compared with previously reported values. For comparisons of oblique beams and surface irregularities, agreement between PBA and MC distributions was better than 99%. Conclusions: Our algorithm showed improved accuracy over other models reported in the literature in predicting the overall shape of the lateral profile through the Bragg peak. This improvement was achieved by incorporating nonelastic scatter events into our PBA. The increased modeling accuracy of our PBA, incorporated into a treatment planning system, may improve the reliability of treatment planning calculations for patient treatments. This research was supported by contract W81XWH‐10‐1‐0005 awarded by The U.S. Army Research Acquisition Activity, 820 Chandler Street, Fort Detrick, MD 21702‐5014. This report does not necessarily reflect the position or policy of the Government, and no official endorsement should be inferred.
SU‐E‐T‐536: Is BJR Supplement #25 Recommendation for Megavoltage Energy Independent Scatter Factor Still Valid for Flattening Filter Free Photon Beams?
Authors: Chung H , Yi B , Prado K
Published: June 2012

Purpose: In the process of measuring and validating fundamental dosimetry data prior to the clinical use of a treatment unit, it is prudent to compare measurements with previously published equivalent data. During the commissioning of an accelerator with flattening filter free (FFF) photon beams (Varian True Beam 6 MV FFF and 10 MV FFF) we compared measured Phantom Scatter Factors (Sp) with the Normalized Peak Scatter Factors (NPSFs) from the British Journal of Radiology Supplement 25 (BJR #25). The purpose of this work was to determine whether the energy independent NPSFs BJR#25 are valid for comparison with FFF photon beams. Methods: All measurements were performed using a Varian TrueBeam linear accelerator with photon energies of 6‐MV, 6‐MV FFF and 10‐MV FFF modes. For all measurements, a Scanditronix CC04 ionization chamber was used. Both water and in‐air measurements were made to obtain NPSFs normalized to the 10 × 10 cm2 field size. For measurements in water, the chamber was positioned at 100 cm source‐to‐axis distance at the depth of dose maximum. For in‐air measurements, the chamber was positioned at 100 cm source‐to‐axis distance with appropriate build‐up cap. From BJR #25, NPSFs were obtained for comparison with the measurements. Results: The NPSF agreement between the 6‐MV and 6‐MV FFF with the BJR#25 were all within ±0.5%. The agreement ranged from 0.996 to 1.004 and 0.995 to 1.002 for 6‐MV and 6‐MV FFF, respectively. We also found that 10‐MV FFF showed very similar trend. Conclusions: The scatter factors reported in BJR #25 are valid for comparison for 6‐MV, 6‐MV FFF, and 10‐MV. Additional investigation is needed to further understand the dosimetric characteristics of FFF mode.
SU‐E‐T‐538: Evaluation of IMRT Dose Calculation Based on Pencil‐Beam and AAA Algorithms
Authors: Yuan Y , Duan J , Popple R , Brezovich I
Published: June 2012

Purpose: To evaluate the accuracy of dose calculation for intensity modulated radiation therapy (IMRT) based on Pencil Beam (PB) and Analytical Anisotropic Algorithm (AAA) computation algorithms. Methods: IMRT plans of twelve patients with different treatment sites, including head/neck, lung and pelvis, were investigated. For each patient, dose calculation with PB and AAA algorithms using dose grid sizes of 0.5 mm, 0.25 mm, and 0.125 mm, were compared with composite‐beam ion chamber and film measurements in patient specific QA. Discrepancies between the calculation and the measurement were evaluated by percentage error for ion chamber dose and γ〉l failure rate in gamma analysis (3%/3mm) for film dosimetry. Results: For 9 patients, ion chamber dose calculated with AAA‐algorithms is closer to ion chamber measurement than that calculated with PB algorithm with grid size of 2.5 mm, though all calculated ion chamber doses are within 3% of the measurements. For head/neck patients and other patients with large treatment volumes, γ〉l failure rate is significantly reduced (within 5%) with AAA‐based treatment planning compared to generally more than 10% with PB‐based treatment planning (grid size=2.5 mm). For lung and brain cancer patients with medium and small treatment volumes, γ〉l failure rates are typically within 5% for both AAA and PB‐based treatment planning (grid size=2.5 mm). For both PB and AAA‐based treatment planning, improvements of dose calculation accuracy with finer dose grids were observed in film dosimetry of 11 patients and in ion chamber measurements for 3 patients. Conclusion: AAA‐based treatment planning provides more accurate dose calculation for head/neck patients and other patients with large treatment volumes. Compared with film dosimetry, a γ〉l failure rate within 5% can be achieved for AAA‐based treatment planning.
SU‐E‐T‐539: The Effect of the Scattering Volume of Phantom on Dose Calculation Accuracy Using Elekta's Cone‐Beam Computed Tomography (CBCT) for Head‐Neck Radiotherapy
Authors: Jiang X , Li T , Peng G , Zhong R , Jiang Q , Zhuang L , Bai S
Published: June 2012

Purpose: To analyze the scattering volume effect of phantom on HU values and dose calculation accuracy utilizing Elekta's cone‐beam computed tomography (CBCT) for head and neck radiotherapy. Methods: A water phantom was designed to simulate different scattering volume by varying its lengthfrom 5cm to 30cm.A CIRS density reference phantom combined with the water phantom was used to measure the CBCT HU values. HU‐ED correction curves for 30cm length (Correction‐A) and 5cm length (Correction‐B) were generated for CBCT dose calculation, respectively. A four‐field‐box plan was designed both on CBCT and conventional CT of a head‐neck anatomical phantom to compare the dosimetric difference. Results: The maximum HU variance in the CBCT of the water phantom was up to 10% with varying phantom length. For the combined CIRS phantom, the HU value in CBCT was found to decrease in high‐density inserts, but increase in low‐density inserts with increasing scatter length.For dense‐bone insert, the change in HU values was up to 1422HU. For head‐neck anatomical phantom, the dose results showed an average difference of 0.3% of cGy /MU, 2–3mm of isodose discrepancy,and 97% of 2%/2mm DTA index for each beam with Correction‐A; and 3.7% of cGy /MU,1.5–3cm of isodose discrepancy,and 59.5% of 2%/2mm DTA index for each beam with Correction‐B. Conclusions: The scattering volume of phantom has a significant impact on the HU value and further HU‐D calibration of Elekta's CBCT. Excellent dosimetric agreement between CBCT and conventional CT was found when the HU‐D calibration phantom volume is close to patient volume imaged by CBCT.
SU‐E‐T‐541: Dose Calculation Algorithm for External Neutron Radiotherapy Based on Pencil Beam Method
Authors: Moiseev A , Klimanov V
Published: June 2012

Purpose: To evaluate the availability and performance of pencil beam algorithm for fast neutrons radiotherapy dose calculations and to achieve improvements in universality, speed and inhomogeneities corrections. Methods: Pencil beam (PB) method uses integration of dose kernel cross field size to estimate dose distribution. In order to calculate dose kernels we used general purpose Monte‐Carlo (MC) code MCNP. The same program was used also for PB benchmarking. Multi‐group approach used for kernels calculation virtually allows calculation for arbitrary spectrum. Nevertheless we took four common spectra to investigate accuracy and to establish according corrections. Several approaches for inhomogeneities corrections have been investigated. The output of MC calculations is discrete kernel data, which does not allow fast calculations. To overcome this limitation we investigated different dose kernels approximations and integrations. Results: PB dose kernel library was established. Comparison of PB calculation with reference algorithm shows adequate precision for arbitrary neutron spectra with inhomogeneities correction, while calculations are fast enough for optimization tasks. Secondary photon dose distributions comparison give worse still promising results. Conclusions: Researches of this paper show benefits and limitations of PB method for neutron teletherapy treatment planning. Calculations made during research allow saying that results of PB method are generally acceptable. Still additional data are needed to evaluate our results, probably voxel phantom MC calculations and/or beam data measurements.
SU‐E‐T‐542: Impact of Tongue‐And‐Groove Width on MLC‐Defined Small Field Dosimetry for Pinnacle 9.0
Authors: Jang S
Published: June 2012

Purpose: the dosimetric impact of Tongue‐and‐Groove (TG) width on MLC‐defined small fields of 1cm in X/Y‐jaw directions for Pinnacle Version 9.0. Methods: Open field of 5cmx5cm was created using the Physics Tool of Pinnacle Version 9.0 and then the MLC leaves were placed manually for creating MLC‐defined small fields of 1cmx2cm to 1cmx5cm as well as of 2cmx1cm to 5cmx1cm at the source‐to‐surface distance of 95cm and depth of 5cm. With the commissioned machine data of Varian 6EX, a series of test machines were simulated by changing the size of MLC TG width (no TG gap, 0.1mm, 0.25mm, 0.5mm, 0.75mm, 1.25mm, and 1.5mm). The other machine/MLC parameters were set to the commissioned values of Varian 6EX. In addition, dose grid sizes of 2mm and 4mm were used for dose calculation purpose. Mapcheck measurements were performed for the MLC‐defined fields of 2×1 cm to 5×1 cm to compare with the calculated dose of Pinnacle Version 9.0. Results: Regardless of MLC‐defined small fields with X‐direction size of 1cm, there was negligible variation of calculated dose as TG width varied from zero TG to 1.5mm. The calculated dose was very sensitive to the dose grid size and there was a good agreement of less than 3% in between measurement and calculation with the dose grid size of 2mm. However, there was over 5% discrepancy with the dose grid size of 4mm for the MLC‐defiled small fields. For the MLC‐defined small fields with Y‐direction size of 1cm, there was over 8% decrease of computed dose compared to those of small fields with X‐direction size of 1 cm, even though the TG width was set to zero, which was that the effective field size of MLC 5cm×1cm was identical to that of MLC 1cm×5cm. With the dose grid size of 4mm, the calculated dose was underestimated over 10% compared to that of 2mm dose grid. Conclusions: Pinnacle Version 9.0 was insensitive to the variation of TG width from no TG to 1.5mm for MLC‐defined small fields with X‐direction size of 1cm. For the MLC‐defined small fields with Y‐direction size of 1cm, there was over 8% decrease of calculated doses compared to those of small fields with X‐direction size of 1 cm, even though the TG width was set to zero.
SU‐E‐T‐546: Cumulative Dose Evaluation for Head and Neck Cancers
Authors: Grevenow M , Scanderbeg D , Kim G
Published: June 2012

Purpose: In this study, we retrospectively analyzed patient treatments utilizing a prototype of the Varian Eclipse™ treatment planning system integrated with their new DART™ technology. Structure volume changes, structure displacements, and dose deviations were analyzed to assess the need for more adaptive treatment planning. Methods: Ten patients with head and neck cancer who received daily cone‐beam imaging CTs, as part of their radiation therapy, were chosen from the University of California San Diego Moores Cancer Center database. With the aid of DART™, we were able to retrospectively calculate the accumulated dose to both the tumor and healthy tissue over the entire course of treatment. This process was accomplished through rigid and deformable registrations of their daily cone‐beam CT scans and cumulative dose measurements. Volumetric changes were compared to their original planning CT image. Results: Our results showed notable changes to the parotid glands in all patients, in both structure shrinkage and dose escalation, which were often correlated with a medial displacement of the glands towards the high‐dose region. Our study estimated that the mean rate of parotid volume reduction was 0.18 cm3/treatment day with a range of 0.08 – 0.31 cm3/treatment day. GTV, CTV, and PTV regions also showed significant volume reductions which was shown to be more pronounced during the first half of treatment. In 6 out of 9 patients with contoured parotids, the absorbed dose increase to these glands was >3%. The GTV, CTV, and PTV showed smaller variations, and in only 1 out of the 10 patients studied did the dose accumulation increase >3%. Conclusions: While the program used was just a prototype, it is our hope for the future that this project could be integrated clinically to develop more adaptive treatment plans allowing for better treatment accuracy and patient care.
SU‐E‐T‐550: Influence of the Clinical Outcome and Quality of Life by Replanning during Intensity‐Modulated Radiation Therapy for Nasopharyngeal Carcinoma
Authors: Yang H , Hu W , Wang W , Chen P
Published: June 2012

Purpose: The purposes of this study were to expound on the benefit of replanning using clinical outcome and Quality of life (QoL) during Intensity‐Modulated Radiation Therapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: A total of 129 new patients with NPC, who were curatively treated by IMRT from June 2007 to August 2011, were recruited. Eighty‐six patients with repeat CT and replanning and 43 patients non‐replanning were retrospectively analyzed. The Chinese version of the European Organization for Research and Treatment of Cancer Quality of Life (QoL) Questionnaire C30 and H&N were completed before treatment, the end of treatment, 1, 3, 6, 12 month after treatment. QoL and Kaplan‐ Meier estimators were used to estimate the survival function of patients with or without replanning. Results: The clinical outcome comparison indicated that replanning during the IMRT for NPC improved the locoregional control (LRC) (p=0.040), but did not improved the overall survival (OS) (p=0.475). The 2‐year LRC, OS rates were 92.4%, 82.2%, and 97.2%, 89.8% in non‐replanning ans replanning, respectively. Global QoL (p=0.012) and role functioning (p=0.000) and social functioning (p=0.000) and dyspnea (p=0.001) and appetite loss (p=0.010) and constipation (p=0.010) and diarrhea (p=0.010) and speech problems (p=0.000) and trouble with social contact (p=0.000) and teeth (p=0.031) and opening mouth and dry mouth (p=0.000) and sticky saliva (p=0.015), have significantly differences between replanning and non‐replanning in patients with NPC. Conclusions: Our results indicate that replanning can improve significantly LRC and QoL variables in patients with NPC. Grant No. 2008B198 from Zhejiang Provincial Medical and Health science Foundation of China.
SU‐E‐T‐551: A Customized Plan Evaluation System for On‐Line Adaptive Radiotherapy
Authors: Jiang L , Arhjoul L , Anderson J , Nedzi L , Solberg T , Mao W
Published: June 2012

Purpose: Treatment plan evaluation based on daily images, to determine whether it is necessary to re‐plan the treatment, is an essential element of adaptive radiotherapy. A fully automatic system, incorporating physician preferences and requirements of specific protocols quantified by a series of objective functions, was developed to evaluate treatment plans. Methods: The evaluation system was developed using IDL 6.1 (ITT Visual Information Solutions, Boulder, CO). Based on customized evaluation guidelines, dosimetric parameters, including maximum dose, minimum dose, uniformity dose, dose coverage, conformity index, heterogeneity index, gEUD, and DVH for the targets and OARs are evaluated as series of cost functions which incorporate specific protocol constraints and physician requirements. The evaluation system was applied to IMRT plans of head/neck cancer patients. The Pinnacle Treatment Planning System (research version 9.0) was used to generate verification treatment plan trials, with image datasets, ROI structures, and dose distributions exported to evaluation system. Results: Results show that the evaluation system can complete evaluation of a dose plan within 2∼8 seconds. The system is capable of displaying and comparing dose distributions among different plans. It also demonstrates great flexibility in customizing cost functions based on physician preferences. This system is supported with various user‐friendly options, graphical displays, and feasibly structure in adding new modules. Conclusions: This evaluation system is capable of quantifying specific protocols and preferences of physicians and completing automatic evaluation almost in real‐time. It is an essential a platform for adaptive radiation therapy and also valuable for initial treatment planning. This research is supported by CPRIT Individual Investigator Award RP110329.
SU‐E‐T‐552: Maximizing the Biological Effect of Proton Dose Delivered with Scanned Beam
Authors: Zeng C , Giantsoudi D , Grassberger C , Goldberg S , Niemierko A , Paganetti H , Trofimov A
Published: June 2012

Purpose: Biological effect of radiation can be enhanced with hypofractionation, localized dose escalation, and controlled distribution of proton's linear energy transfer (LET). We evaluate potential gain in therapeutic effect from delivery of daily inhomogeneous fractional dose distributions in pencil beam scanning proton therapy (PBS‐PT). Methods: For cases of prostate cancer, we considered a hypofractionated course of 20 fractions of 3 Gy (assuming α/β=1.5, the equivalent dose in 2‐Gy fractions (ED2Gy) is 77.1 Gy). Two sets of dose distributions were planned using two opposed lateral fields to deliver a uniform dose: (1) in full‐target plans (FTP) each beam targeted the entire gland (2) in split‐target plans (STP), beams targeted only the respective proximal hemispheres (prostate split sagittally). Linear combinations of optimized beam intensity maps from FTP and STP, for a variety of mixing weights, were used to evaluate inhomogeneous fractional dose (IFD) distributions. IFD delivered doses boosting either hemisphere in alternating fractions, e.g., alternating between 40% and 160% of the nominal fractional dose (1.2–4.8 Gy). The equivalent uniform dose (EUD) was calculated for ED2Gy distributions. IFD plans were rescaled so that the EUD of rectum and bladder did not increase. LET distributions were calculated with Monte Carlo, and compared for different plans. Results: In the IFD courses, the whole prostate received a nearly uniform dose in every 2 fractions, however EUD was higher than in conventional FTP by up to 8%. Rectal EUD decreased by 2%, and bladder EUD was unchanged. The LET distributions of FTP and STP were distinctly different, thus, in IFD, LET depended strongly on the mixing weights. Conclusions: In PBS‐PT, modestly improved therapeutic outcome can be expected with delivery of inhomogeneous daily dose distributions, while administering the prescribed dose to target over the entire course. The biological effectiveness may be further enhanced by optimizing the LET distributions. The project was supported by the Federal Share of program income earned by Massachusetts General Hospital on C06 CA059267, Proton Therapy Research and Treatment Center.
SU‐E‐T‐553: Dose‐Mass Vs. Dose‐Volume Optimization: A Phantom Study
Authors: Mihaylov I , Moros E , Siebers J
Published: June 2012

Purpose: To demonstrate the merits of mass‐based optimization in comparison with volume‐based optimization using a simple test phantom. Methods: Dose‐volume‐histogram‐based (DVH‐based) quadratic objective functions are converted into dose‐mass‐histogram‐based (DMH‐based) objective functions by multiplying per‐voxel volumes by per‐voxel densities within the objective. A digital phantom with a 1.0 g/cm3 target is constructed for irradiation with two beams: one beam path contains a 0.2 g/cm3 volume‐of‐interest (VOI0.2) while the orthogonal beam‐path contains an equal‐volume 0.8 g/cm3 VOI (VOI0.8). Monitor‐units are computed to achieve a 100 cGy average target dose for each individual beam, and for two‐beam DVH‐based and DMH‐based optimizations. Results: For single‐beam irradiation through VOI0.2, the average dose to VOI0.2 is 20.5 cGy. For single‐beam irradiation through VOI0.8, the average dose to VOI0.8 is 25.2 cGy. Traversing the low density volume results in ∼23% lower dose. When DVH‐ and DMH‐based optimizations are performed such that target dose‐volume‐histograms of the optimizations match, for the DVH optimization 60% vs. 40% of the dose is delivered through VOI0.2 vs. VOI0.8. For DMH‐optimization, the split between dose delivered through VOI0.2 vs. VOI0.8 is 70% vs. 30%. Conclusions: When density is constant, there is no difference between DVH‐ and DMH‐based optimizations. However, in heterogeneous media, DMH and DVH solutions differ when low and high density materials have the same dose objectives. Delivering target dose through lower density VOIs facilitates target dose deposition due to a decrease in attenuating material, and the decreased attenuation lowers dose to the low density VOI. From mathematical and physical points of view dose‐mass optimization is more general than dose‐volume optimization.
SU‐E‐T‐555: Weighted Four‐Dimensional IMRT Planning for Dynamic MLC Tracking Using a Practical and Simple Framework
Authors: Tachibana H , Cheung Y , Jain S , Sawant A
Published: June 2012

Purpose: We present a simple, practical framework for truly 4D lung IMRT planning based on a weighted individual‐phase optimization paradigm. This strategy is specifically developed for use in real‐time tumor tracking delivery systems so as to utilize respiratory motion as an additional degree of freedom rather than a constraint. Methods: A 4D‐CT scan from a lung SBRT patient was loaded into the Eclipse treatment planning system. The target and normal structures were manually contoured on each of the ten phases. For each phase, the total dose prescription was scaled by the number of phases and a seven‐field plan was developed. An open‐source deformable image and dose registration engine (DIRART) was used to deform the dose map at each phase to a reference phase. DVH data from the individually optimized phase plans were input into an in‐house linear programming‐based optimizer implemented in MATLAB, in order to determine dose‐weighting factors for each phase. The objective function aimed to maintain PTV coverage while keeping normal structure dose as low as possible. This weighted‐4D plan (W‐4D) was compared to an ITV‐based plan and a 4D plan with equal dose‐weights to individual phases (E‐4D). Results: The W‐4D dose fractions were determined to be 0.33, 0.01, 0.65 and 0.02 at phase 0%, 30%, 40%, and 90%, respectively (and zero elsewhere). PTV coverage (V95) was close to identical for all three strategies. The W‐4D plan exhibited mean lung dose 18.8% and 8.5% lower and mean liver dose 23.3% and 5.7% lower than corresponding values from ITV‐based and E‐4D plans, respectively. Conclusions: By significantly improving normal structure sparing while maintaining PTV coverage, weighted 4D planning represents a more attractive solution than ITV‐based planning for (currently investigational) real‐time tumor tracking‐based delivery systems.
SU‐E‐T‐558: Assessing the Effect of Inter‐Fractional Motion in Esophageal Sparing Plans
Authors: Williamson R , Bluett J , Niedzielski J , Liao Z , Gomez D , Court L
Published: June 2012

Purpose: To compare esophageal dose distributions in esophageal sparing IMRT plans with predicted dose distributions which include the effect of inter‐fraction motion. Methods: Seven lung cancer patients were used, each with a standard and an esophageal sparing plan (74Gy, 2Gy fractions). The average max dose to esophagus was 8351cGy and 7758cGy for the standard and sparing plans, respectively. The average length of esophagus for which the total circumference was treated above 60Gy (LETT60) was 9.4cm in the standard plans and 5.8cm in the sparing plans. In order to simulate inter‐fractional motion, a three‐dimensional rigid shift was applied to the calculated dose field. A simulated course of treatment consisted of a single systematic shift applied throughout the treatment as well a random shift for each of the 37 fractions. Both systematic and random shifts were generated from Gaussian distributions of 3mm and 5mm standard deviation. Each treatment course was simulated 1000 times to obtain an expected distribution of the delivered dose. Results: Simulated treatment dose received by the esophagus was less than dose seen in the treatment plan. The average reduction in maximum esophageal dose for the standard plans was 234cGy and 386cGY for the 3mm and 5mm Gaussian distributions, respectively. The average reduction in LETT60 was 0.6cm and 1.7cm, for the 3mm and 5mm distributions respectively. For the esophageal sparing plans, the average reduction in maximum esophageal dose was 94cGy and 202cGy for 3mm and 5mm Gaussian distributions, respectively. The average change in LETT60 for the esophageal sparing plans was smaller, at 0.1cm (increase) and 0.6cm (reduction), for the 3mm and 5mm distributions, respectively. Conclusions: Interfraction motion consistently reduced the maximum doses to the esophagus for both standard and esophageal sparing plans.
MO‐F‐213CD‐03: Design and Testing of the VirtualDose Software Under the Software as a Service (SaaS) Platform for Tracking and Reporting CT Doses
Authors: Ding A , Gao Y , Caracappa P , Liu B , Xu X
Published: June 2012

Purpose: To report recent progress toward developing and testing the VirtualDose software under the ‘Software as a Service (SaaS)’ platform for tracking and reporting patient CT doses. Methods: Many of existing tools for reporting CT dose are based on data derived from phantoms that are anatomically crude and ignore pediatric, obese and pregnant patients. Based on extensive original dose data derived from Monte Carlo simulations and computational phantoms including a new set of BMI‐adjustable obese patient phantoms, VirtualDose was designed under the ‘Software as a Service (SaaS)’ platform to provide a Web based software application to a large number of client users. Unlike the traditional software, SaaS does not require the installation of the software on a user's computer. Organ doses and effective doses are computed using ICRP Publication 60 and 103. Dosimetry capabilities for tube current modulation (TCM) protocols are included by integrating a DICOM information extraction function module. A new ‘Service‐Orientated Architecture (SOA)’ software developing pattern is adopted in designing and building the whole software architecture. The entire software framework was developed using Microsoft .NET platform. C# was used as the primary programming language in the development of the graphical user interface (GUI). Results: Testing of the VirtualDose package shows that the modern GUI accommodates for interactively displaying 3D phantoms and selecting scanner parameters. The patient (weight, age, gender) and scan parameter information(e.g., kVp, mAs, scan protocol, etc.) stored in the DICOM file can be automatically retrieved and imported into ‘VirtualDose’ to calculate the organ dose and effective dose for specific patients. After the dose calculation process is complete, the software will automatically summarizes various scan parameters and results in Microsoft Word (‘.doc’) format. Conclusions: The VirtualDose package shows improved patient organ dose database, software GUI design, reporting features, and software distribution mode when compared with existing tools. This project was supported by the National Institute of Biomedical Imaging and Bioengineering (R42EB010404).
MO‐F‐213CD‐04: Characterization of Optically Stimulated Luminescence Detectors for Organ Dose Phantom Measurement in Diagnostic Radiology
Authors: Rodriguez M , Yukihara E , Ahmad S , Ruan C
Published: June 2012

Purpose: To evaluate the feasibility and accuracy of using aluminum oxide doped with carbon (Al2O3:C) and beryllium oxide (BeO) optically stimulated luminescence (OSL) detectors for the purpose of measuring organ dose in a phantom for diagnostic radiology. Methods: The energy response of each type of detector as a function of kVp and in‐phantom depth was determined using blocks of Polymethyl methacrylate (PMMA) and an ionization chamber (0.4 cm3). The Al2O3:C detectors used in this study were cut from LuxelTM tape into 4 mm diameter circles of thickness 0.3 mm. The BeO detectors used in this study are ∼4.7 mm x ∼4.7 mm x 0.5 mm chips. Clinical irradiations were performed using a radiographic unit. The BeO signal was read using a Riso/, TL/OSL‐DA‐15 automated reader and the Al2O3:C signal was read using a custom‐built light emitting diode (LED)‐based reader system. The results were compared to those obtained from LiF:Mg,Ti thermoluminescence detectors (TLD). Results: The energy‐dependent response as a function of depth within the phantom for BeO and Al2O3:C were found to be < 8% and < 10%, respectively. For comparison, the TLDs were found to have an energy‐dependent response of ∼8%. The OSL detectors both offered reproducibility better than 5%. Conclusions: The proposed method of using BeO and Al2O3:C OSL detectors to perform in‐phantom measurements has a comparable in‐phantom energy response to that of TLD's and shows improved reproducibility of the measurements when compared to TLD's. Given the flexibility and accuracy of OSL detectors for various readout techniques, OSL detectors have a great potential to be used in clinical organ dose measurement for diagnostic x‐ray exams.
MO‐F‐213CD‐06: Implementation of Fluoroscopy Dose Mining and Analysis Process for Continuous Quality Assurance
Authors: Stewart B , Zamora D , Dickinson R , Rohrmann C , Kanal K
Published: June 2012

Purpose: The varied dose reporting capabilities of fluoroscopic equipment combined with the difficultly in compiling and correlating data to specific procedures represents a challenge. The aim is to establish a method of collecting and analyzing cumulative dose from a collection of fluoroscopic equipment in a radiology department. Methods: Preliminary work was performed on each fluoroscopic system, including verification of dose display availability (software modification/upgrade) and accuracy and documentation of current dose metric capabilities and units. For a given procedure, the technologist manually entered the cumulative air kerma (AK) into the radiology information system (RIS). A quarterly report was generated containing AK values and procedure information for every fluoroscopy case performed. Data was separated by equipment classification (customized based on clinical application) and procedure type. For each data subset, cases exceeding a z_score of 5 (indicating >5 SD above mean) were excluded and catalogued. Basic statistics (mean/SD/median/percentiles/min/max) were calculated for the purpose of observing longitudinal trends. Finally, a list of flagged studies ‐ cases exceeding the 95 th percentile for a given data subset ‐ was generated for the purpose of clinical review. Results: Presentation of longitudinal data as a box‐and‐whisker plot highlights shifts in median AK and in the population distributions. For gastrointestinal (GI) studies using a remote digital unit, we observed median AK ranging from 25 mGy for a video esophagram up to 165 mGy for an upper GI with KUB. For mobile c‐arms, median AK values ranged from 0.1 mGy to 402 mGy, depending on procedure. Conclusions: We have developed a robust method of collecting and analyzing dose data from fluoroscopic equipment. By reviewing identified high dose cases, we hope to improve training and clinical practice. To better discern explicit procedure types, modification of the RIS procedure codes is necessary for certain equipment classifications.