Anisotropic Analytical Algorithm Algorithm Research Articles

Investigation of Dose Calculation Accuracy of Eclipse Treatment Planning System in the Presence of Metal Hip Prosthesis with Thermoluminescence Dosimeters

Aim: This study investigated the dose calculation accuracy of different treatment planning algorithms used in radiotherapy patients with hip prostheses. Method: The current research produced a tissue-equivalent cylindrical phantom that imitates a leg using a 3D printer. Co-Cr-Mo alloy and Ti-6AI-4V alloy prostheses were placed in the centre of the phantom, respectively. Both prostheses' dose measurements were taken with thermoluminescent dosimeters (TLD) at 92 points. The dose calculation accuracy of the Analytical Anisotropic Algorithm (AAA) and Pencil Beam Convolution (PBC) algorithms, widely used in radiotherapy, were compared with the measurement results. Results: Since the Co-Cr-Mo hip prosthesis has a high density, the number of backscattered photons around it was higher than the Ti-6AI-4V hip prosthesis. The average surface dose of the Co-Cr-Mo alloy was 364.05 cGy, while the average surface dose of the Ti-6AI-4V alloy was 347.79 cGy. Conclusion: It was observed that the dose estimation abilities of the AAA and PBC algorithms decreased as the density of the hip replacement increased. In addition, the AAA algorithm predicted the surface dose in the phantom better than the PBC algorithm.

Feasibility of Achieving Dose Constraints for Dysphagia Aspiration-Related Structures and Its Clinical Significance in Intensity-Modulated Radiotherapy Planning of Head and Neck Cancer.

Introduction Dysphagia is commonly seen in patients with head and neck cancers after undergoing chemoradiotherapy and is often under-reported and also not given clinical importance. The quality of life of the patients can be significantly improved if the required dose constraints to the dysphagia aspiration-related structures (DARS) are achieved. The present study was conducted in order to determine the feasibility of achieving the dose constraints to DARS between the standard intensity-modulated radiotherapy(st-IMRT) arm and the dysphagia-optimized IMRT (do-IMRT) arm. Material and methods Sixty patients with head and neck cancer were recruited and randomized into two groups: In one group called the st-IMRT, constraints were not given to DARS, and in the other group called the do-IMRT, constraints were given to DARS. Treatment was given in the form of chemoradiation with a dose of 70 Gy in 35 fractions by IMRTtechnique, over seven weeks, 2 Gy per fraction along with weekly concurrent Cisplatin (35 mg/m2) in both the groups. Step and shoot IMRT setup was used for planning, and the system used forplanning was Eclipse 13.6 (Varian Medical System, Inc., Palo Alto, CA, US); progressive resolution optimizeralgorithm was used for optimization, and Anisotropic Analytical Algorithmalgorithm was used for dose calculation. Truebeam was used for treatment delivery. DARS dosimetric parameters assessed were Dmean, V30, V50, V60, V70, D50, and D80. Radiation-induced toxicities to the skin, mucosa, larynx, salivary gland, and dysphagiaand hematological toxicities were assessed in between both the groups during and after radiotherapy up to six months based on Common Terminology Criteria for Adverse Effects v5.0. p-values were calculatedusing the unpaired T-test. Results In the cohort of 60 patients with head and neck cancers, 95% were males. Dosimetric parameters of the planning target volume (PTV) were compared but were not found to be significant. In the dosimetry of the organs at risk, a p-value of some structures was found to be significant although the doses received were well within the tolerable limits in both arms. DARS dosimetry V60 and V70 of the inferior constrictor muscle was found to be statistically significant (p=0.01 and 0.008, respectively). V60 and V70 of larynx were also statistically significant (p=0.009 and 0.000, respectively). V70 and D50 of cricopharyngeus were found to be statistically significant (p=0.01 and 0.03, respectively), V30 and V60 for combined pharyngeal constrictor muscles were found to be statistically significant (p=0.02 and 0.01), and lastly, V60 for combined DARS was also significant (p=0.004). Post-treatment 33.3% of patients in the st-IMRT arm required Ryle's tube placement. No grade 4 toxicities were seen in either arm regarding hematological toxicities, acute or chronic radiation-induced toxicities. In site-wise comparison of doses, the p-value was not found to be significant in patients with oropharyngeal and oral cavity carcinomas but was found to be statistically significant in the larynx and hypopharynx subsites. Conclusion The feasibility of achieving dose constraints to the DARS was seen in cases of laryngeal and hypopharyngeal cancers where the constrictor muscles were at a distance from the PTV. Further, the feasibility of achieving dose constraints may be seen in lower-dose prescriptions either in postoperative cases or in low-risk clinical target volumenodal volumes.

The transition in practice to reduce bolus use in post-mastectomy radiotherapy: A dosimetric study of skin and subcutaneous tissue.

To inform clinical practice for women receiving post-mastectomy radiotherapy (PMRT), this study demonstrates the dosimetric impact of removing daily bolus on skin and subcutaneous tissue. Two planning strategies were used: clinical field-based (n = 30) and volume-based planning (n = 10). The clinical field-based plans were created with bolus and recalculated without bolus for comparison. The volume-based plans were created with bolus to ensure a minimum target coverage of the chest wall PTV and recalculated without bolus. In each scenario, the dose to superficial structures, including skin (3 mm and 5 mm) and subcutaneous tissue (a 2 mm layer, 3 mm deep from surface) were reported. Additionally, the difference in the clinically evaluated dosimetry to skin and subcutaneous tissue in volume-based plans were recalculated using Acuros (AXB) and compared to the Anisotropic Analytical Algorithm (AAA) algorithm. For all treatment planning strategies, chest wall coverage (V90%) was maintained. As expected, superficial structures demonstrate significant loss in coverage. The largest difference observed in the most superficial 3 mm where V90% coverage is reduced from a mean (± standard deviation) of 95.1% (± 2.8) to 18.9% (± 5.6) for clinical field-based treatments with and without bolus, respectively. For volume-based planning, the subcutaneous tissue maintains a V90% of 90.5% (± 7.0) compared to the clinical field-based planning coverage of 84.4% (± 8.0). In all skin and subcutaneous tissue, the AAA algorithm underestimates the volume of the 90% isodose. Removing bolus results in minimal dosimetric differences in the chest wall and significantly lower skin dose while dose to the subcutaneous tissue is maintained. Unless the skin has disease involvement, the most superficial 3 mm is not considered part of the target volume. The continued use of the AAA algorithm is supported for the PMRT setting.

Radiobiological Comparison of Acuros External Beam and Anisotropic Analytical Algorithm on Esophageal Carcinoma Radiotherapy Treatment Plans.

ObjectiveThe present study aimed to investigate the dose differences and radiobiological assessment between Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB) with its 2 calculation models, namely, dose-to-water (AXB-Dw) and dose-to-medium (AXB-Dm), on esophageal carcinoma radiotherapy treatment plans.Materials and methodsThe AXB-Dw and AXB-Dm plans were generated by recalculating the initial 66 AAA plans using the AXB algorithm with the same monitor units and beam parameters as those in the original plan. The dosimetric and radiobiological assessment parameters were calculated for the planning target volume (PTV) and organs at risk (OARs). The gamma agreement for the PTV and the correlation between it and the volume of the air cavity and bone among the different algorithms were compared simultaneously. The dose discrepancy between the theoretical calculation and treatment planning system (TPS) when switching from AXB-Dm to AXB-Dw was analyzed according to the composition of the structures.ResultsThe PTV dose of AXB-Dm plans was significantly smaller than that of the AAA and AXB-Dw plans (P < .05), except for D2. The difference values for AAA vs AXB-Dm (∆Dx,(AAA-AXB,Dm)) and AXB-Dw vs AXB-Dm (∆Dx,(AXB,Dw-AXB,Dm)) were 1.94% [1.27%, 2.64%] and 1.95% [1.56%, 2.27%], respectively. For the spinal cord and heart, there were obvious differences between the AAA vs AXB-Dm (spinal cord: 1.15%, heart: 2.89%) and AXB-Dw vs AXB-Dm (spinal cord: 1.88%, heart: 3.25%) plans. For the lung, the differences between AAA vs AXB-Dm and AAA vs AXB-Dw were significantly larger than those of AXB-Dm vs AXB-Dw. Compared to the case of AAA and AXB-Dw, the decrease in biologically effective dose (BED10, ) of AXB-Dm due to dose non-uniformity exceeded 6.5%, even for a small . The average values of equivalent uniform dose in the AAA, AXB-Dw, and AXB-Dm plans were 52.03±.39 Gy, 52.24 ± .81 Gy, and 51.13 ± .47 Gy, respectively. The tumor control probability (TCP) results for PTV in the AAA, AXB-Dw, and AXB-Dm plans were 62.29 ± 1.57%, 62.82 ± 1.69%, and 58.68±1.88%, respectively. With the 2%/2 mm and 3%/3 mm acceptance criteria, the mean values of , , and were 87.24, 63.3, and 64.81% vs 97.86, 91.77, and 89.25%, respectively. The dose discrepancy between the theoretical calculation and TPS when switching from AXB-Dm to AXB-Dw was approximately 1.63%.ConclusionsThe AAA and AXB-Dw algorithms overestimated the radiobiological parameters when the tumor particularly consisted of nonuniform tissues. A relatively small dose difference could cause a significant reduction in the corresponding TCP. Dose distribution algorithms should be carefully chosen by physicists and oncologists to improve tumor control, as well as to optimize OARs protection.

Dosimetric comparison and validation of Eclipse Anisotropic Analytical Algorithm (AAA) and AcurosXB (AXB) algorithms in RapidArc-based radiosurgery plans of patients with solitary brain metastasis.

Stereotactic radiosurgery (SRS) is increasingly being used to manage solitary or multiple brain metastasis. This study aims to compare and validate Anisotropic Analytical Algorithm (AAA) and AcurosXB (AXB) algorithms of Eclipse Treatment Planning System (TPS) in RapidArc-based SRS plans of patients with solitary brain metastasis. Twenty patients with solitary brain metastasis who have been already treated with RapidArc SRS plans calculated using AAA plans were selected for this study. These plans were recalculated using AXB algorithm keeping the same arc orientations, multi-leaf collimator apertures, and monitor units. The two algorithms were compared for target coverage parameters, isodose volumes, plan quality metrics, dose to organs at risk and integral dose. The dose calculated by the TPS using AAA and AXB algorithms was validated against measured dose for all patient plans using an in-house developed cylindrical phantom. An Exradin A14SL ionization chamber was positioned at the center of this phantom to measure the in-field dose. NanoDot Optically Stimulated Luminescent Dosimeters (OSLDs) (Landauer Inc.) were placed at distances 3.0 cm, 4.0 cm, 5.0 cm, and 6.0 cm respectively from the center of the phantom to measure the non-target dose. In addition, the planar dose distribution was measured using amorphous silicon aS1000 Electronic Portal Imaging Device. The measured 2D dose distribution was compared against AAA and AXB estimated 2D distribution using gamma analysis. All results were tested for significance using the paired t-test at 5% level of significance. Significant differences between the AAA and AXB plans were found only for a few parameters analyzed in this study. In the experimental verification using cylindrical phantom, the difference between the AAA calculated dose and the measured dose was found to be highly significant (p < 0.001). However, the difference between the AXB calculated dose and the measured dose was not significant (p = 0.197). The difference between AAA/AXB calculated and measured at non-target locations was statistically insignificant at all four non-target locations and the dose calculated by both AAA and AXB algorithms shows a strong positive correlation with the measured dose. The results of the gamma analysis show that the AXB calculated planar dose is in better agreement with measurements compared to the AAA. Even though the results of the dosimetric comparison show that the differences are mostly not significant, the measurements show that there are differences between the two algorithms within the target volume. The AXB algorithm may be therefore more accurate in the dose calculation of VMAT plans for the treatment of small intracranial targets. For non-target locations either algorithm can be used for the estimation of dose accounting for their limitations in non-target dose estimations.

Dosimetric Influence of Acuros XB Dose-to-Medium and Dose-to-Water Reporting Modes on Carcinoma Cervix Using Intensity-Modulated Radiation Therapy and Volumetric RapidArc Technique.

Aim:We aimed to evaluate the dosimetric influence of Acuros XB (AXB) dose-to-medium (Dm) and dose-to-water (Dw) reporting mode on carcinoma cervix using intensity-modulated radiation therapy (IMRT) and RapidArc (RA) technique.Materials and Methods:A cohort of thirty patients cared for carcinoma cervix was retrospectively selected for the study. Plans were computed using analytical anisotropic algorithm (AAA), AXB-Dm, and AXB-Dw algorithms for dosimetric comparison. A paired t-test and Pitman–Morgan dispersion test were executed to appraise the difference in mean values and the inter-patient variability of the differences.Results:The dose–volume parameters were higher for AXB-Dw in contrast to AAA for IMRT and RA plans, excluding D98%, minimum dose to planning target volume (PTV) and rectum mean dose (RA). There was no systematic trend observed in dose–volume parameters for PTV and organs at risk (OARs) between AXB-Dm and AXB-Dw for IMRT and RA plans. The dose–volume parameters for target were higher for AXB-Dm in comparison to AAA in IMRT and RA plans, except D98% and minimum dose to PTV. Analysis envisaged less inter-patient variability while switching from AAA to AXB-Dm in comparison to those switching from AAA to AXB-Dw.Conclusions:The present study reveals the important difference between AAA, AXB-Dm, and AXB-Dw computations for cervix carcinoma using IMRT and RA techniques. The inter-patient variability and systematic difference in dose–volume parameters computed using AAA, AXB-Dm, and AXB-Dw algorithms present the possible impact on the dose prescription to PTV and their relative constraints to OARs for IMRT and RA techniques. This may help in the decision-making in clinic while switching from AAA to AXB (Dm or Dw) algorithm for cervix carcinoma using IMRT and RA techniques.

Commissioning of a three-dimensional arc-based technique for total body irradiation.

The purpose of this study is to describe the commissioning of a novel three‐dimensional arc‐based technique for total body irradiation (TBI) treatments. The development and implementation of this technique allowed our institution to transition from a bilateral two‐dimensional (2D) technique to a methodology based on volumetric dose calculation. The methodology described in this work is a derivation from the MATBI technique, with the static fields being replaced by four contiguous arc‐fields for each anterior and posterior incidence. The reduced number of fields we employed makes it possible to reach a satisfactory dose uniformity through manual optimization in a straightforward process. We use the Eclipse anisotropic analytical algorithm (AAA) algorithm, commissioned with preconfigured beam data for a 6 MV photon beam, at standard SSD (100 cm). A thorough evaluation of the accuracy of the AAA algorithm at an extended distance (approximately 200 cm) was carried out. For the evaluation, we compared measured and calculated percentage depth–dose and profiles that included open‐field, penumbra, and out‐of‐field regions. The analysis was performed for both static and arc fields, taking into consideration unshielded fields and also in the presence of lung shielding blocks. End‐to‐end tests were carried out for our institutional template plan by two means: with a 2D ion chamber array detector in solid phantom and using Gafchromic films in an anthropomorphic phantom. The results obtained in this work demonstrate that the Eclipse AAA algorithm commissioned for standard treatments can be safely used with our TBI planning technique. Moreover, this technique proved to be a highly efficient path to replace conventional treatment techniques, providing a homogeneous dose distribution, dosimetric robustness, and shorter treatment times. In addition, as inherited from the MATBI technique, our methodology can be implemented in small treatment rooms, with no need for ancillary equipment.

Dosimetric evaluation of analytic anisotropic algorithm and Acuros XB algorithm using in-house developed heterogeneous thorax phantom and homogeneous slab phantom for stereotactic body radiation therapy technique

To perform patient-specific quality assurance (QA), the accuracy of the dose calculation algorithm is vital, especially in the lung cancer stereotactic body radiation therapy (SBRT). The present study is based on the evaluation of two widely used algorithms, analytical anisotropic algorithm (AAA) and Acuros XB (AXB) inside the in-house developed heterogeneous thorax phantom (HTP) and a homogeneous slab phantom (HSP) simultaneously. To evaluate dosimetric differences between the two algorithms, point dose measurement was performed for pretreatment QA plans of 35 lung cancer patients by keeping the same monitor units and beam angles as those for the actual patient treatment. The dose was calculated on the Eclipse treatment planning system inside both the medium by using both AAA and AXB algorithms. Plans were delivered on the Edge linear accelerator (LA) (Varian Medical Systems, Palo Alto, CA, USA), and measurements were taken by using a 0.01 cc ion chamber and DOSE1 electrometer. Statistical analysis was performed on the observed data set, and percentage (%) variations between the measured and planned doses were calculated and analyzed. The mean % variations between the measured and planned doses inside HTP for all QA plans were found to be 2.61 (standard deviation [SD]: 0.66) and 2.19 (SD: 0.64) for AAA and AXB algorithms, respectively. Whereas, inside HSP, it was found to be 1.79 (SD: 0.74) and 1.64 (SD: 0.70) for AAA and AXB algorithms, respectively. The mean % difference between the measured dose and the planned dose was derived to be statistically significant for HTP, however, it was found to be statistically insignificant inside the HSP at P

The effect on tumour control probability of using AXB algorithm in replacement of AAA for SBRT of hepatocellular carcinoma located at lung-liver boundary region.

Objective:To retrospectively analyze the clinical impact on stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC) located at lung–liver boundary due to the use of Acuros XB algorithm (AXB) in replacement of anisotropic analytical algorithm (AAA).Methods:23 SBRT volumetric modulated arc therapy (VMAT) plans for HCC located at lung–liver boundary were calculated using AAA and AXB respectively with the same treatment parameters. The dose–volume data of the planned target volumes (PTVs) were compared. A published tumour control probability (TCP) model was used to calculate the effect of dosimetric difference between AAA and AXB on tumour control probability.Results:For dose calculated by AXB (Dose to medium), the D95% and D98% of the PTV were on average 2.4 and 3.1% less than that calculated by AAA. For dose calculated by AXB (dose to water), the D95% and D98% of the PTV were on average 1.8%, and 2.7% less than that calculated by AAA. Up to 5% difference in D95% and 8% difference in D98% were observed in the worst cases. The significant decrease in D95% calculated by AXB compared to AAA could result in a % decrease in 2 year TCP up to 8% in the worst case (from 46.8 to 42.9%).Conclusion:The difference in dose calculated by AAA and AXB could lead to significant difference in TCP for HCC SBRT located at lung–liver boundary region.Advances in knowledge:The difference in calculated dose and tumour control probability for HCC SBRT between AAA and AXB algorithm at lung–liver boundary region was compared.

Assessing the out-of-field dose calculation accuracy by eclipse treatment planning system in sliding window IMRT of prostate cancer patients

AimThe objective of this study was to evaluate out-of-field dose distribution calculation accuracy by the Anisotropic Analytical Algorithm (AAA), version 13.0.26, in Eclipse TPS, (Varian Medical Systems, Palo Alto, Ca, USA) for sliding window IMRT delivery technique in prostate cancer patients. Materials and methodsProstate IMRT plans with nine coplanar were calculated with the AAA Eclipse treatment planning system. To assess the accuracy of dose calculation predicted by the Eclipse in normal tissue and OARs located out of radiation field areas, including the rectum, bladder, right and left head of the femur, absolute organ dose value, and dose distribution were measured using the Delta4+ IMRT phantom. ResultsIn the out-of-field areas, underestimation of −0.66% in organs near the field edge to −39.63% in organs far from the field edge (2.5 and 7.3 cm respectively) occurred in the TPS calculations. The percentage of dose deviation for the femoral heads was 95.7 on average while for the organ closer to the target (rectum) it was 79.81. ConclusionsAAA dosimetry algorithm (used in Eclipse TPS) showed poor dose calculation in areas beyond the treatment fields border where underestimation varies with the distance from the field edges. A significant underestimation was found for the AAA algorithm in the sliding window IMRT technique (P-value > 0.05).

Comparison and evaluation for the dose distribution and physical characteristics between two AAA and AXB algorithms in Eclipse v13.6 software on treatment plans in regions heterogenous densities at 108 Military Central Hospital

The aim of this study is to compare and evaluate the dose distribution and physical characteristics of two algorithms Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) inEclipse v13.6 software in regions heterogeneous densities. Computed Tomography Simulation (CT –Sim) data of 48 treated cancer patients (20 head and neck cancer (H&amp;N) patients, 15 esophageal cancer patients, 8 lung cancer patients with 3 Dimensions Conformal Radiation Therapy (3D-CRT)and 5 lung cancer patients treated with Volumetric Modulated Arc Therapy (VMAT)) were used to replan the Eclipse v13.6 software with two algorithm AAA and AXB. For all plans, the Quality of Coverage (Q), the Conformity Index (CI), the Homogeneity Index (HI) and the dose volume histograms (DVH) for the targets and the organs at risk (OARs) were compared and evaluated. Pretreatment quality assurance (QA) was performed using the Electronic Portal Imaging Device(EPID) for all VMAT plans, and the gamma index method was used to qualify the agreement between calculations and measurements. In addition, total Monitor Units (MUs) and the calculation time were investigated. The indicators obtained from the H&amp;N VMAT plans calculated by AAA close to ideal values than AXB. The total MUs obtained from two algorithms are approximately equal. The lung cancer 3D – CRT plans, the indicators for target and OARs are approximately the same. However, the calculation time of the AAA is faster than the AXB from 7.5 to 14 times. The indicator obtained from the lung cancer VMAT plans calculated by two algorithms AAA and AXB are approximately equal. The total MUs and time calculation are approximate the same. However, the V5, V10, V20 and Mean Lung Dose (MLD) obtained from AAA is lower than AXB. For esophageal cancer VMAT plans, the indicators HIRTOG, HIWu, and Q calculated by AAA close to the ideal values than AXB. However, the indicators CIPaddick, CIICRU-62, V5, V10, V20 and MLD calculated by AXB are better than AAA. The dose distribution indicators obtained from AAA algorithm are better than AXB algorithm in H&amp;N cancer and lung cancer plans. For the esophageal cancer plans, AXB algorithm gave the dose distribution indicator are better than AAA.

Evaluation of Adaptive Planning of Lung Cases based on Cone Beam CT Images

The purpose of this study was to evaluate the accuracy of dose calculation based on Cone Beam Computed Tomography (CBCT) as adaptive planning for lung cancer. Dose calculation based on CBCT images was compared to Computed Tomography (CT) simulator images as references. Treatment planning was generated for 7 patients of lung using Intensity Modulated Radiotherapy (IMRT) technique and Volumetric Arc Therapy (VMAT) technique. Eclipse v13.6 Treatment Planning System (TPS) with Analytical Anisotropic Algorithm (AAA) and Acuros External Beam (AXB) algorithm were used to calculate the dose. This study was divided into three major parts: (1) Hounsfield Unit (HU) calibration for CBCT images by using CIRS 002LFC phantom; (2) analysis of Dose Volume Histogram (DVH); (3) analysis of Passing Rate Gamma with criteria Dose Difference (DD) 2%/Distance To Agreement (DTA) 2mm and DD 3%/DTA 3mm using Electronic Portal Imaging Device (EPID). The DVH analysis for D98%, D50% and D2% deviation was evaluated and compared to the DVH for CT images with AAA algorithm as reference. The deviation of D98%, D50% and D2% for lung cancer was less than 2%. The range of conformity index based on CBCT images for all planning was 0,923-0,999 and the homogeneity index was in the range of 0,042-0,197. The gamma criteria (DD/DTA) of dose difference and distance to agreement for 2%/2mm are 87% - 94% and for 3%/3mm were 96% -98% for IMRT techniques. Passing Rate Gamma for VMAT with 2%/2mm criteria were 87% -96% and 3%/3mm criteria were 96% - 98%. The results of this study showed that dose calculation based on CBCT image was similar to dose calculation using CT image with descrepancy less than 2%.

Dosimetric Accuracy Comparison between ACUROSE XB, AAA and PBC Dose Calculation Algorithms in EclipseTM TPS Using a Heterogeneous Phantom

Purpose: The aim of this study is to compare the accuracy of different algorithms in EclipseTM Treatment Planning System (TPS) using a heterogeneous phantom.&#x0D; Materials and Methods: The method is based on the International Atomic Energy Agency's TEC-DOC 1583 report. The chest phantom of CIRS, PTW30010 ionization chamber and an electrometer (PTW, Freiburg) were used for the measurements.&#x0D; Three ACUROSE XB (AXB), Analytical Anisotropic Algorithm (AAA) and Pencil Beam Convolution (PBC) dose calculation algorithms available in Eclipse TM TPS were considered in this study.&#x0D; Results: Based on the measurements, the maximum differences between calculated dose by TPS and measured dose in TEC-DOC 1583 tests were 2.5%, 8.6% and 16.1% for the AXB, AAA and PBC algorithms in heterogeneous media, respectively.&#x0D; Conclusion: The Acuros XB algorithm has superior accuracy to predict the dose distribution in the heterogeneous tissues such as lung compared to AAA and PBC algorithms

Effects of metal implants and a metal artifact reduction tool on calculation accuracy of AAA and Acuros XB algorithms in small fields.

In this study, the dosimetric accuracy of analytical anisotropic algorithm (AAA) and Acuros XB (AXB) dose calculation algorithms (Varian Medical Systems, Palo Alto, CA) was investigated for small radiation fields incident on phantoms of various metals that include stainless steel grade 316L (SS316L) and titanium alloy grade 5 (Ti5) implants. In addition, the effects of using metal artifact reduction for orthopedic implants (O-MAR, Philips Healthcare, Cleveland, OH) were evaluated. The evaluations of AAA and AXB were performed by comparing the crossline profiles calculated by AAA and AXB with GafChromicTM EBT3 film measurements at the phantom-implant interfaces and in close vicinity of implant materials for small field sizes (1×1cm2 , 2×2cm2 , 3×3cm2 , and 4×4cm2 ) of a 6MV flattening filter free photon beam. O-MAR corrected and uncorrected (UC) computed tomography (CT) images were used for dose calculations. The values of average and standard deviations (SD) of Hounsfield unit (HU) for selected regions of each case were evaluated. The differences in average dose percentages in defined regions were calculated to quantify the relative dosimetric changes between doses calculated on UC and O-MAR corrected CT images. Compared to UC images, the values of SD were reduced, and the average HU became closer to its reference value in the O-MAR images. There was some discrepancy in average dose percentage differences between calculations using UC and O-MAR images at 1cm above the SS316L implant (average dose percentage differences were AXB/UC=5.9% and AXB/O-MAR=-1.2%; AAA/UC=2.2%, and AAA/O-MAR=-0.8%). Neither AAA nor AXB algorithms predict increase in dose at upper phantom-implant interface (4.9%, 9.9%. 13.5%, and 13.8% for the fields from 1×1cm2 to 4×4cm2 , respectively). At the side of the SS316L implant (where dark streak artifacts exist), dose difference averages were estimated as-1.1% and 22.3% when AXB/O-MAR and AXB/UC calculations are compared with EBT3 measurements, respectively. Dose predictions at 1cm below the SS316L implant were underestimated by AXB/O-MAR (average -0.5%) and AXB/UC (average 2.0%). The O-MAR tool was shown to have a favorable dosimetric effect or no effect on the calculations in the upper proximity of the implant materials. The dose differences between EBT3 film measurements and calculations at upper phantom-implant interfaces were smaller when they were calculated using O-MAR images. However, the dose differences increased when O-MAR corrected images were used for AAA calculations at lower phantom-implant interfaces. Use of O-MAR enabled closer agreement for the AXB algorithm, especially in the dark streak artifact regions. The O-MAR algorithm should be used when the dose is calculated with the AXB algorithm in cases of patients with the metal implants. The estimations using AAA and AXB algorithms, in phantom setups, with Ti5 implant material were found to be closer to the EBT3 film measurements, when compared with the same estimations using SS316L implant material.

Dosimetric evaluation of the dose calculation accuracy of different algorithms for two different treatment techniques during whole breast irradiation

In-field, partially in-field, and out-of-field organ doses calculated by the Acuros XB (AXB) and analytical anisotropic algorithm (AAA) were compared with experimentally measured data for two different techniques of whole breast radiotherapy (WBRT). The field-in-field conformal radiotherapy (FIF) and intensity-modulated radiation therapy (IMRT) plans were calculated by AAA and dose-to-water (Dw) and dose-to-medium (Dm) options used by AXB. In field (planning target volume (PTV)), partially in-field (ipsilateral lung, heart, left ascending coronary artery (LAD)), and out-of-field (contralateral lung and contralateral breast) organ at risk (OAR) doses were measured using thermoluminescent dosimeters (TLDs) and EBT3 films in an anthropomorphic phantom. Furthermore, target dose differences between AAA and AXB were analyzed for the corresponding real patients. For the verification of planar dose distribution in PTV, the percentages of pixels that passed the gamma analysis with the ± 3%/3mm criteria were 93.5%, 93.9%, and 99.0% for AAA, AXB_Dm, and AXB_Dw, respectively, averaged over all IMRT and FIF plans. For the verification of point doses within the target using TLD in the randophantom, the max percentage deviations between the calculated and measured data when averaged over all IMRT and FIF plans were 6.8%, 4.7%, and 3.9% for AAA, AXB_Dm, and AXB_Dw, respectively. When using the Eclipse TPS for breast cancer, AXB should be used instead of the AAA algorithm, bearing in mind that the AXB may still overestimate all OARs doses.

Which Dose Specification Should Be Used for NRG Radiation Therapy Trials: Dose-to-Medium or Dose-to-Water?

PurposeTo compare the doses calculated by the Analytical Anisotropic Algorithm (AAA), Acuros dose-to-medium, and Acuros dose-to-water for the patients with lung cancer treated at our institution and show that further investigation and clarification are needed about what dose specifications should be used for NRG clinical trials. Methods and MaterialsTwenty-one patients with lung cancer who previously received intensity modulated radiation therapy or volumetric modulated arc therapy–based treatments at our institution were analyzed by recalculating their plans for each one with the AAA algorithm (reviewed and approved by our radiation oncologists) and with both reporting modes of the Acuros algorithm. All plans used the same monitor units as the original approved plan and a 2.5-mm grid size. For each patient, D100 of clinical target volume (CTV) and CTV coverage ratios in each plan were compared, and dose distributions and dose-volume histograms calculated by AAA, Acuros dose-to-water (Dw,m), and Acuros dose-to-medium (Dm,m) were compared as well. ResultsDifferences between CTV D100 calculated by AAA and Acuros Dm,m were larger than the differences between AAA and Acuros XB Dw,m for all patients. When D100 of CTV was evaluated, the largest difference between AAA and Acuros Dm,m was 14.12% and between AAA and Acuros XB Dw,m was 3.68%. The average differences between the CTV D100 calculated by AAA and Acuros Dm,m was 5.39%. Coverage ratio between Acuros Dm,m and AAA ranges from 51.08% to 100% with an average of 91.32%; coverage ratio between Acuros Dw,m and AAA ranges from 87.2% to 100.41% with average of 98.94%; coverage ratio between Acuros Dm,m and Acuros Dw,m ranges from 58.58% to 100% with an average of 92.03%. ConclusionsThe present study shows large and systematic differences in doses calculated by AAA and Acuros Dm,m. Therefore, further investigation and clarification are needed about which dose reporting mode should be used.

Dosimetric comparison of different algorithms in stereotactic body radiation therapy (SBRT) plan for non-small cell lung cancer (NSCLC).

PurposesThe main aim of the study was to investigate the dosimetric difference between acuros XB algorithm (AXB), anisotropic analytic algorithm (AAA), and pencil beam convolution (PBC) algorithm in stereotactic body radiation therapy (SBRT) plan for non-small cell lung cancer (NSCLC).Patients and MethodsThirty-eight NSCLC patients were included. GTV, PTV, and organs at risk were delineated by the radiation oncologists. Three optimized SBRT plans for each patients were gained using three algorithms of AXB, AAA, and PBC with the identical plan parameters. Dosimetric endpoints were collected and compared among the three plans, including dosimetric criteria: V100%, V90%, PTV Dmin, Dmax, Dmean, homogeneity index (HI), and Paddick conformity index (CI).ResultsAXB plan resulted in decreased V100% with a mean difference 6.14% compared with PBC plan (For V100%, AXB vs AAA vs PBC=93.44% vs 95.54% vs 99.58%, P<0.05). Three plans showed no significant difference as to the parameter V90%. AXB plan leaded to reduced Dmin of PTV compared with other two algorithms (For Dmin of PTV, AXB vs AAA vs PBC=4048cGy vs 4365Gy vs 4873Gy, P<0.05). PBC induced the enhanced trend of Dmax of PTV compared with other two algorithms (Dmax among three algorithms, P>0.05); and increased the Dmean of PTV in three algorithms with significant difference (For Dmean of PTV, AXB vs AAA vs PBC=5332cGy vs 5330Gy vs 5785Gy, P<0.05). AXB algorithm achieved a similar plan conformity with other two algorithms (For CI, AXB vs AAA vs PBC=0.80 vs 0.85 vs 0.71, P>0.05).ConclusionFor SBRT plan of NSCLC, AAA and PBC algorithms overestimate target coverage, AXB algorithm is recommended for the SBRT plan of NSCLC.

Evaluating small field dosimetry with the Acuros XB (AXB) and analytical anisotropic algorithm (AAA) dose calculation algorithms in the eclipse treatment planning system

AbstractBackground:An increasing number of external beam treatment modalities including intensity modulated radiation therapy, volumetric modulated arc therapy (VMAT) and stereotactic radiosurgery uses very small fields for treatment planning and delivery. However, there are major challenges in small photon field dosimetry, due to the partial occlusion of the direct photon beam source’s view from the measurement point, lack of lateral charged particle equilibrium, steep dose-rate gradient and volume averaging effect of the detector response and variation of the energy fluence in the lateral direction of the beam. Therefore, experimental measurements of dosimetric parameters such as percent depth doses (PDDs), beam profiles and relative output factors (ROFs) for small fields continue to be a challenge.Materials and Methods:In this study, we used a homogeneous water phantom and the heterogeneous anthropomorphic stereotactic end-to-end verification (STEEV) head phantom for all dose measurements and calculations. PDDs, lateral dose profiles and ROFs were calculated in the Eclipse Treatment Planning System version 13·6 using the Acuros XB (AXB) and the analytical anisotropic algorithms (AAAs) in a homogenous water phantom. Monte Carlo (MC) simulations and measurements using the Exradin W1 Scintillator were also accomplished for four photon energies: 6 MV, 6FFF, 10 MV and 10FFF. Two VMAT treatment plans were generated for two different targets: one located in the brain and the other in the neck (close to the trachea) in the head phantom (CIRS, Norfolk, VA, USA). A Varian Truebeam linear accelerator (Varian, Palo Alto, CA, USA) was used for all treatment deliveries. Calculated results with AXB and AAA were compared with MC simulations and measurements.Results:The average difference of PDDs between W1 Exradin Scintillator measurements and MC simulations, AAA and AXB algorithm calculations were 1·2, 2·4 and 3·2%, respectively, for all field sizes and energies. AXB and AAA showed differences in ROF of about 0·3 and 2·9%, respectively, compared with W1 Exradin Scintillator measured values. For the target located in the brain in the head phantom, the average dose difference between W1 Exradin Scintillator and the MC simulations, AAA and AXB were 0·2, 3·2 and 2·7%, respectively, for all field sizes. Similarly, for the target located in the neck, the respective dose differences were 3·8, 5·7 and 3·5%.Conclusion:In this study, we compared dosimetric parameters such as PDD, beam profile and ROFs in water phantom and isocenter point dose measurements in an anthropomorphic head phantom representing a patient. We observed that measurements using the W1 Exradin scintillator agreed well with MC simulations and can be used efficiently for dosimetric parameters such as PDDs and dose profiles and patient-specific quality assurance measurements for small fields. In both homogenous and heterogeneous media, the AXB algorithm dose prediction agrees well with MC and measurements and was found to be superior to the AAA algorithm.

On the use of AAA and AcurosXB algorithms for three different stereotactic ablative body radiotherapy (SABR) techniques: Volumetric modulated arc therapy (VMAT), intensity modulated radiation therapy (IMRT) and 3D conformal radiotherapy (3D-CRT).

The purpose of this study was to investigate the dosimetric characteristics of three stereotactic ablative body radiotherapy (SABR) techniques using the anisotropic analytical algorithm (AAA) and Acuros XB algorithm. The SABR techniques include coplanar volumetric modulated arc therapy (C-VMAT), non-coplanar intensity modulated radiation therapy (NC-IMRT) and non-coplanar three-dimensional conformal radiotherapy (NC-3D CRT). SABR is a special type of radiotherapy where a high dose of radiation is delivered over a short time. The treatment outcome and accuracy of the dose delivered to cancer patients highly depend on the dose calculation algorithm and treatment technique. Twelve lung cancer patients underwent 4D CT scanning, and three different treatment plans were generated: C-VMAT, NC-IMRT, NC-3D CRT. Dose calculation was performed using the AAA and Acuros XB algorithm. The dosimetric indices, such as conformity index (CI), homogeneity index, dose fall-off index, doses received by organs at risk and planning target volume, were used to compare the plans. The accuracy of AAA and Acuros XB (AXB) algorithms for the lung was validated against measured dose on a CIRS thorax phantom. The CIs for C-VMAT, NC-IMRT and NC-3D CRT were 1.21, 1.28 and 1.38 for the AAA, respectively, and 1.17, 1.26 and 1.36 for the Acuros XB algorithm, respectively. The overall dose computed by AcurosXB algorithm was close to the measured dose when compared to the AAA algorithm. The overall dose computed by the AcurosXB algorithm was close to the measured dose when compared to the AAA algorithm. This study showed that the treatment planning results obtained using the Acuros XB algorithm was better than those using the AAA algorithm in SABR lung radiotherapy.

Dosimetric Comparison of Integral Radiation Dose: Anisotropic Analytical Algorithm and Acuros XB in Breast Radiotherapy

The impact of the difference between Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) in breast radiotherapy is not clearly due to different uses and further research is required to explain this effect. The aim of this study is to investigate the contribution of calculation differences between AAA and AXB to the integral radiation dose (ID) on critical organs. Seven field intensity modulated radiotherapy (IMRT) plans were generated using with AAA and AXB algorithms for twenty patients with early stage left breast cancer after breast conserving surgery. Volumetric and dosimetric differences, as well as, the Dmean, V5, V20 doses of the left and right-sided lung, the Dmean, V10, V20, V30 doses of heart and the Dmean, V5, V10 doses of the contralateral breast were investigated. The mean dose (Dmean), V5, V20 doses of the left-sided lung, the Dmean, V5, V10 doses of right-sided lung, the Dmean, V10, V20, V30 doses of heart and the Dmean, V5, V10 doses of the contralateral breast were found to be significantly higher with AAA. In this research integral dose was also higher in the AAA recalculated plan and the AXB plan with the average dose as follows left lung 2%, heart 2%, contralateral breast 8%, contralateral lung 4% respectively. Our study revealed that the calculation differences between Acuros XB (AXB) and Anisotropic Analytical Algorithm (AAA) in breast radiotherapy caused serious differences on the stored integral doses on critical organs. In addition, AXB plans showed significantly dosimetric improvements in multiple dosimetric parameters.