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Title: SU-F-SPS-01: Accuracy of the Small Field Dosimetry Using Acuros XB and AAA Dose Calculation Algorithms of Eclipse Treatment Planning System Within and Beyond Heterogeneous Media for Trubeam 2.0 Unit

Abstract

Purpose: In this study, the comparison of dosimetric accuracy of Acuros XB and AAA algorithms were investigated for small radiation fields incident on homogeneous and heterogeneous geometries Methods: Small open fields of Truebeam 2.0 unit (1×1, 2×2, 3×3, 4×4 fields) were used for this study. The fields were incident on homogeneous phantom and in house phantom containing lung, air, and bone inhomogeneities. Using the same film batch, the net OD to dose calibration curve was obtaine dusing Trubeam 2.0 for 6 MV, 6 FFF, 10 MV, 10 FFF, 15 MV energies by delivering 0- 800 cGy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. The dosimetric accuracy of Acuros XB and AAA algorithms in the presence of the inhomogeneities was compared against EBT3 film dosimetry Results: Open field tests in a homogeneous phantom showed good agreement betweent wo algorithms and measurement. For Acuros XB, minimum gamma analysis passin grates between measured and calculated dose distributions were 99.3% and 98.1% for homogeneousand inhomogeneous fields in thecase of lung and bone respectively. For AAA, minimum gamma analysis passingrates were 99.1% and 96.5% for homogeneous and inhomogeneous fields respectively for all used energies and field sizes.In the casemore » of the air heterogeneity, the differences were larger for both calculations algorithms. Over all, when compared to measurement, theAcuros XB had beter agreement than AAA. Conclusion: The Acuros XB calculation algorithm in the TPS is an improvemen tover theexisting AAA algorithm. Dose discrepancies were observed for in the presence of air inhomogeneities.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;  [1]
  1. Medipol University, Istanbul, Istanbul (Turkey)
Publication Date:
OSTI Identifier:
22624418
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ACCURACY; ALGORITHMS; CALIBRATION; FIELD TESTS; FILM DOSIMETRY; GRATINGS; INHOMOGENEOUS FIELDS; IRRADIATION; LUNGS; PHANTOMS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; SKELETON

Citation Formats

Codel, G, Serin, E, Pacaci, P, Sanli, E, Cebe, M, Mabhouti, H, Doyuran, M, Kucukmorkoc, E, Kucuk, N, Altinok, A, Canoglu, D, Acar, H, and Caglar Ozkok, H. SU-F-SPS-01: Accuracy of the Small Field Dosimetry Using Acuros XB and AAA Dose Calculation Algorithms of Eclipse Treatment Planning System Within and Beyond Heterogeneous Media for Trubeam 2.0 Unit. United States: N. p., 2016. Web. doi:10.1118/1.4955676.
Codel, G, Serin, E, Pacaci, P, Sanli, E, Cebe, M, Mabhouti, H, Doyuran, M, Kucukmorkoc, E, Kucuk, N, Altinok, A, Canoglu, D, Acar, H, & Caglar Ozkok, H. SU-F-SPS-01: Accuracy of the Small Field Dosimetry Using Acuros XB and AAA Dose Calculation Algorithms of Eclipse Treatment Planning System Within and Beyond Heterogeneous Media for Trubeam 2.0 Unit. United States. doi:10.1118/1.4955676.
Codel, G, Serin, E, Pacaci, P, Sanli, E, Cebe, M, Mabhouti, H, Doyuran, M, Kucukmorkoc, E, Kucuk, N, Altinok, A, Canoglu, D, Acar, H, and Caglar Ozkok, H. 2016. "SU-F-SPS-01: Accuracy of the Small Field Dosimetry Using Acuros XB and AAA Dose Calculation Algorithms of Eclipse Treatment Planning System Within and Beyond Heterogeneous Media for Trubeam 2.0 Unit". United States. doi:10.1118/1.4955676.
@article{osti_22624418,
title = {SU-F-SPS-01: Accuracy of the Small Field Dosimetry Using Acuros XB and AAA Dose Calculation Algorithms of Eclipse Treatment Planning System Within and Beyond Heterogeneous Media for Trubeam 2.0 Unit},
author = {Codel, G and Serin, E and Pacaci, P and Sanli, E and Cebe, M and Mabhouti, H and Doyuran, M and Kucukmorkoc, E and Kucuk, N and Altinok, A and Canoglu, D and Acar, H and Caglar Ozkok, H},
abstractNote = {Purpose: In this study, the comparison of dosimetric accuracy of Acuros XB and AAA algorithms were investigated for small radiation fields incident on homogeneous and heterogeneous geometries Methods: Small open fields of Truebeam 2.0 unit (1×1, 2×2, 3×3, 4×4 fields) were used for this study. The fields were incident on homogeneous phantom and in house phantom containing lung, air, and bone inhomogeneities. Using the same film batch, the net OD to dose calibration curve was obtaine dusing Trubeam 2.0 for 6 MV, 6 FFF, 10 MV, 10 FFF, 15 MV energies by delivering 0- 800 cGy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. The dosimetric accuracy of Acuros XB and AAA algorithms in the presence of the inhomogeneities was compared against EBT3 film dosimetry Results: Open field tests in a homogeneous phantom showed good agreement betweent wo algorithms and measurement. For Acuros XB, minimum gamma analysis passin grates between measured and calculated dose distributions were 99.3% and 98.1% for homogeneousand inhomogeneous fields in thecase of lung and bone respectively. For AAA, minimum gamma analysis passingrates were 99.1% and 96.5% for homogeneous and inhomogeneous fields respectively for all used energies and field sizes.In the case of the air heterogeneity, the differences were larger for both calculations algorithms. Over all, when compared to measurement, theAcuros XB had beter agreement than AAA. Conclusion: The Acuros XB calculation algorithm in the TPS is an improvemen tover theexisting AAA algorithm. Dose discrepancies were observed for in the presence of air inhomogeneities.},
doi = {10.1118/1.4955676},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: In small field geometries, the electronic equilibrium can be lost, making it challenging for the dose-calculation algorithm to accurately predict the dose, especially in the presence of tissue heterogeneities. In this study, dosimetric accuracy of Monte Carlo (MC) advanced dose calculation and sequential algorithms of Multiplan treatment planning system were investigated for small radiation fields incident on homogeneous and heterogeneous geometries. Methods: Small open fields of fixed cones of Cyberknife M6 unit 100 to 500 mm2 were used for this study. The fields were incident on in house phantom containing lung, air, and bone inhomogeneities and also homogeneous phantom.more » Using the same film batch, the net OD to dose calibration curve was obtained using CK with the 60 mm fixed cone by delivering 0- 800 cGy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. The dosimetric accuracy of MC and sequential algorithms in the presence of the inhomogeneities was compared against EBT3 film dosimetry Results: Open field tests in a homogeneous phantom showed good agreement between two algorithms and film measurement For MC algorithm, the minimum gamma analysis passing rates between measured and calculated dose distributions were 99.7% and 98.3% for homogeneous and inhomogeneous fields in the case of lung and bone respectively. For sequential algorithm, the minimum gamma analysis passing rates were 98.9% and 92.5% for for homogeneous and inhomogeneous fields respectively for used all cone sizes. In the case of the air heterogeneity, the differences were larger for both calculation algorithms. Overall, when compared to measurement, the MC had better agreement than sequential algorithm. Conclusion: The Monte Carlo calculation algorithm in the Multiplan treatment planning system is an improvement over the existing sequential algorithm. Dose discrepancies were observed for in the presence of air inhomogeneities.« less
  • Purpose: Advanced stereotactic radiotherapy (SRT) treatments require accurate dose calculation for treatment planning especially for treatment sites involving heterogeneous patient anatomy. The purpose of this study was to evaluate the accuracy of dose calculation algorithms, Raytracing and Monte Carlo (MC), implemented in the MultiPlan treatment planning system (TPS) in presence of heterogeneities. Methods: First, the LINAC of a CyberKnife radiotherapy facility was modeled with the PENELOPE MC code. A protocol for the measurement of dose distributions with EBT3 films was established and validated thanks to comparison between experimental dose distributions and calculated dose distributions obtained with MultiPlan Raytracing and MCmore » algorithms as well as with the PENELOPE MC model for treatments planned with the homogenous Easycube phantom. Finally, bones and lungs inserts were used to set up a heterogeneous Easycube phantom. Treatment plans with the 10, 7.5 or the 5 mm field sizes were generated in Multiplan TPS with different tumor localizations (in the lung and at the lung/bone/soft tissue interface). Experimental dose distributions were compared to the PENELOPE MC and Multiplan calculations using the gamma index method. Results: Regarding the experiment in the homogenous phantom, 100% of the points passed for the 3%/3mm tolerance criteria. These criteria include the global error of the method (CT-scan resolution, EBT3 dosimetry, LINAC positionning …), and were used afterwards to estimate the accuracy of the MultiPlan algorithms in heterogeneous media. Comparison of the dose distributions obtained in the heterogeneous phantom is in progress. Conclusion: This work has led to the development of numerical and experimental dosimetric tools for small beam dosimetry. Raytracing and MC algorithms implemented in MultiPlan TPS were evaluated in heterogeneous media.« less
  • Purpose: Inaccuracies in out-of-field calculations could lead to underestimation of dose to organs-at-risk. This study evaluates the dose calculation accuracy of a model-based calculation algorithm at points outside the primary treatment field for an intensity modulated radiation therapy (IMRT) plan using experimental measurements. Methods: The treatment planning system investigated is Varian Eclipse V.10 with Analytical Anisotropic Algorithm (AAA). The IMRT fields investigated are from real patient treatment plans. The doses from a dynamic (DMLC) IMRT brain plan were calculated and compared with measured doses at locations outside the primary treatment fields. Measurements were performed with a MatriXX system (2-D chambermore » array) placed in solid water. All fields were set vertically incident on the phantom and were 9 cm × 6 cm or smaller. The dose was normalized to the central axis for points up to 15 cm off isocenter. The comparisons were performed at depths of 2, 10, 15, and 20 cm Results: The measurements have shown that AAA calculations underestimate doses at points outside the primary treatment field. The underestimation occurs at 2 cm depth and decreases down to a factor of 2 as depth increases to 20 cm. In low dose (<2% of target dose) regions outside the primary fields the local dose underestimations can be >200% compared to measured doses. Relative to the plan target dose, the measured doses to points outside the field were less than 1% at shallow depths and less than 2% at greater depths. Conclusion: Compared to measurements, the AAA algorithm underestimated the dose at points outside the treatment field with the greatest differences observed at shallow depths. Despite large local dose uncertainties predicted by the treatment planning system, the impact of these uncertainties is expected to be insignificant as doses at these points were less than 1-2% of the prescribed treatment dose.« less
  • Purpose: To compare the doses calculated by the Acuros XB (AXB) algorithm and analytical anisotropic algorithm (AAA) with experimentally measured data adjacent to and within heterogeneous medium using intensity modulated radiation therapy (IMRT) and RapidArc{sup Registered-Sign} (RA) volumetric arc therapy plans for nasopharygeal carcinoma (NPC). Methods: Two-dimensional dose distribution immediately adjacent to both air and bone inserts of a rectangular tissue equivalent phantom irradiated using IMRT and RA plans for NPC cases were measured with GafChromic{sup Registered-Sign} EBT3 films. Doses near and within the nasopharygeal (NP) region of an anthropomorphic phantom containing heterogeneous medium were also measured with thermoluminescent dosimetersmore » (TLD) and EBT3 films. The measured data were then compared with the data calculated by AAA and AXB. For AXB, dose calculations were performed using both dose-to-medium (AXB{sub Dm}) and dose-to-water (AXB{sub Dw}) options. Furthermore, target dose differences between AAA and AXB were analyzed for the corresponding real patients. The comparison of real patient plans was performed by stratifying the targets into components of different densities, including tissue, bone, and air. Results: For the verification of planar dose distribution adjacent to air and bone using the rectangular phantom, the percentages of pixels that passed the gamma analysis with the {+-} 3%/3mm criteria were 98.7%, 99.5%, and 97.7% on the axial plane for AAA, AXB{sub Dm}, and AXB{sub Dw}, respectively, averaged over all IMRT and RA plans, while they were 97.6%, 98.2%, and 97.7%, respectively, on the coronal plane. For the verification of planar dose distribution within the NP region of the anthropomorphic phantom, the percentages of pixels that passed the gamma analysis with the {+-} 3%/3mm criteria were 95.1%, 91.3%, and 99.0% for AAA, AXB{sub Dm}, and AXB{sub Dw}, respectively, averaged over all IMRT and RA plans. Within the NP region where air and bone were present, the film measurements represented the dose close to unit density water in a heterogeneous medium, produced the best agreement with the AXB{sub Dw}. For the verification of point doses within the target using TLD in the anthropomorphic phantom, the absolute percentage deviations between the calculated and measured data when averaged over all IMRT and RA plans were 1.8%, 1.7%, and 1.8% for AAA, AXB{sub Dm} and AXB{sub Dw}, respectively. From all the verification results, no significant difference was found between the IMRT and RA plans. The target dose analysis of the real patient plans showed that the discrepancies in mean doses to the PTV component in tissue among the three dose calculation options were within 2%, but up to about 4% in the bone content, with AXB{sub Dm} giving the lowest values and AXB{sub Dw} giving the highest values. Conclusions: In general, the verification measurements demonstrated that both algorithms produced acceptable accuracy when compared to the measured data. GafChromic{sup Registered-Sign} film results indicated that AXB produced slightly better accuracy compared to AAA for dose calculation adjacent to and within the heterogeneous media. Users should be aware of the differences in calculated target doses between options AXB{sub Dm} and AXB{sub Dw}, especially in bone, for IMRT and RA in NPC cases.« less
  • Purpose: To assess the accuracy against measurements of two photon dose calculation algorithms (Acuros XB and the Anisotropic Analytical algorithm AAA) for small fields usable in stereotactic treatments with particular focus on RapidArc. Methods: Acuros XB and AAA were configured for stereotactic use. Baseline accuracy was assessed on small jaw-collimated open fields for different values for the spot sizes parameter in the beam data: 0.0, 0.5, 1, and 2 mm. Data were calculated with a grid of 1 x 1 mm{sup 2}. Investigated fields were: 3 x 3, 2 x 2, 1 x 1, and 0.8 x 0.8 cm{sup 2}more » with a 6 MV photon beam generated from a Clinac2100iX (Varian, Palo Alto, CA). Profiles, PDD, and output factors were measured in water with a PTW diamond detector (detector size: 4 mm{sup 2}, thickness 0.4 mm) and compared to calculations. Four RapidArc test plans were optimized, calculated and delivered with jaw settings J3 x 3, J2 x 2, and J1 x 1 cm{sup 2}, the last was optimized twice to generate high (H) and low (L) modulation patterns. Each plan consisted of one partial arc (gantry 110 deg. to 250 deg.), and collimator 45 deg. Dose to isocenter was measured in a PTW Octavius phantom and compared to calculations. 2D measurements were performed by means of portal dosimetry with the GLAaS method developed at authors' institute. Analysis was performed with gamma pass-fail test with 3% dose difference and 2 mm distance to agreement thresholds. Results: Open square fields: penumbrae from open field profiles were in good agreement with diamond measurements for 1 mm spot size setting for Acuros XB, and between 0.5 and 1 mm for AAA. Maximum MU difference between calculations and measurements was 1.7% for Acuros XB (0.2% for fields greater than 1 x 1 cm{sup 2}) with 0.5 or 1 mm spot size. Agreement for AAA was within 0.7% (2.8%) for 0.5 (1 mm) spot size. RapidArc plans: doses were evaluated in a 4 mm diameter structure at isocenter and computed values differed from measurements by 0.0, -0.2, 5.5, and -3.4% for Acuros XB calculations (1 mm spot size), and of -0.1, 0.3, 6.7, and -1.2% for AAA, respectively for J3 x 3, J2 x 2, J1 x 1H, J1 x 1L RapidArc plans. Gamma Agreement Index from 2D dose analysis was higher than 95% for J3 x 3 and J2 x 2 plans, being around 80% for J1 x 1 maps. Sensitivity with respect to the dosimetric leaf gap and transmission factor MLC parameters was evaluated in the four RapidArc plans, showing the need to properly set the dosimetric leaf gap for accurate calculations. Conclusions: Acuros XB and AAA showed acceptable characteristics for stereotactic small fields if adequate tuning of configuration parameters is performed. Dose calculated for RapidArc stereotactic plans showed an acceptable agreement against point and 2D measurements. Both algorithms can therefore be considered safely applicable to stereotactic treatments.« less