EP-1480: Patient-specific QA for CyberKnife MLC plans using Monte Carlo (original) (raw)
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Dosimetric and radiobiological comparison for quality assurance of IMRT and VMAT plans
Journal of applied clinical medical physics, 2017
The gamma analysis used for quality assurance of a complex radiotherapy plan examines the dosimetric equivalence between planned and measured dose distributions within some tolerance. This study explores whether the dosimetric difference is correlated with any radiobiological difference between delivered and planned dose. VMAT or IMRT plans optimized for 14 cancer patients were calculated and delivered to a QA device. Measured dose was compared against planned dose using 2-D gamma analysis. Dose volume histograms (for various patient structures) obtained by interpolating measured data were compared against the planned ones using a 3-D gamma analysis. Dose volume histograms were used in the Poisson model to calculate tumor control probability for the treatment targets and in the Sigmoid dose-response model to calculate normal tissue complication probability for the organs at risk. Differences in measured and planned dosimetric data for the patient plans passing at ≥94.9% rate at 3%/3...
La radiologia medica, 2020
Objectives Motivation of this study is to check the sensitivity of dosimetric tool gamma with 2D detector array combination when unexpected errors occur while transferring intensity-modulated radiation therapy treatment plans from planning system to treatment unit. Methods This study consists of 17 head and neck cancer patient's treatment plans. Nine types of verification plans are created for all 17 clinically approved treatment plans by consecutively deleting different segments (up to eight) one by one from each field of the plan. Decrement factor (χ) is introduced in our study which illustrated the degree of decay of gamma passing rate when intentional errors are introduced. We analyzed the data by two different methods-one without selecting the region of interest (ROI) in dose distributions and the other by selecting the region of interest. Results By linear regression, the absolute value of slopes is 0.025, 0.024 and 0.015 without ROI and 0.030, 0.027 and 0.015 with ROI for 2%/2 mm, 3%/3 mm and 5%/5 mm criteria, respectively. The higher absolute value of the fitted slope indicates the higher sensitivity of this method to identify erroneous plan in treatment unit. The threshold value for 2%/2 mm equivalent to 95% passing criteria in 3%/3 mm used in clinical practice is obtained as 83.44%. Conclusions The 2D detector array with dosimetric tool gamma is less sensitive in detecting errors when unprecedented errors of segment deletion occur within the treatment plans.
Iranian Journal of Radiation Research, 2021
Background: The intensity-modulated radiotherapy (IMRT) enables personalized treatment; the complexity of this technique increased the need for patient-specific quality assurance (QA). Objective: Comparing three dosimeters that common for patient-specific QA of IMRT. Material and Method: cases were planned at Eclipse treatment planning system (TPS) to receive radiotherapy at Unique VARIAN linear accelerator LINAC; Patient-specific QA was performed with three independent dosimeters: Gafchromic films EPT2, Electronic Portal Image Device (EPID), and PTW 2D array. The absolute dose was measured and analysis of 2D gamma index was performed, then compared with the plan calculated in TPS. Results: Analysis of absolute dose measured have highest difference from dose in Gafchromic film (89.1±4) % while EPID had a lower range (96.6 ± 1.2) and 2Darray showed an agreement up to (99±1.2) for patient specific QA both EBT2 and EPID enable to compare the measured map with TPS calculations, for plan conformity the gafchromic film enable measurement with lower accuracy even with localized brain tumor, the heterogeneity in lung case slightly affect the EPID measurement, this found also with irregular surface of head and neck and increased depth within pelvic case examine. Measurement with 2D array found to be the optimum dosimeter within different conditions. Conclusion: different parameters might affect the accuracy of gafchromic film including film scanning, storing, and calibration curve. EPID has an average deviation appears in beam fluence and 2D array as a 2D ion chamber found to have the most accurate dosimeter, but still time consuming when compared to EPID.
Journal of Applied Clinical Medical Physics
Purpose: Patient-specific quality assurance (QA) is very important in radiotherapy, especially for patients with highly conformed treatment plans like VMAT plans. Traditional QA protocols for these plans are time-consuming reducing considerably the time available for patient treatments. In this work, a new MC-based secondary dose check software (SciMoCa) is evaluated and benchmarked against well-established TPS (Monaco and Pinnacle 3) by means of treatment plans and dose measurements. Methods: Fifty VMAT plans have been computed using same calculation parameters with SciMoCa and the two primary TPSs. Plans were validated with measurements performed with a 3D diode detector (ArcCHECK) by translating patient plans to phantom geometry. Calculation accuracy was assessed by measuring point dose differences and gamma passing rates (GPR) from a 3D gamma analysis with 3%-2 mm criteria. Comparison between SciMoCa and primary TPS calculations was made using the same estimators and using both patient and phantom geometry plans. Results: TPS and SciMoCa calculations were found to be in very good agreement with validation measurements with average point dose differences of 0.7 AE 1.7% and −0.2 AE 1.6% for SciMoCa and two TPSs, respectively. Comparison between SciMoCa calculations and the two primary TPS plans did not show any statistically significant difference with average point dose differences compatible with zero within error for both patient and phantom geometry plans and GPR (98.0 AE 3.0% and 99.0 AE 3.0% respectively) well in excess of the typical 95%clinical tolerance threshold. Conclusion: This work presents results obtained with a significantly larger sample than other similar analyses and, to the authors' knowledge, compares SciMoCa with a MC-based TPS for the first time. Results show that a MC-based secondary patient-specific QA is a clinically viable, reliable, and promising technique, that potentially allows significant time saving that can be used for patient treatment and a per-plan basis QA that effectively complements traditional commissioning and calibration protocols.
International Journal of Nuclear Medicine & Radioactive Substances, 2019
Purpose: In modern radiotherapy techniques such as intensity-modulated radiation therapy (IMRT) and volume modulated arc therapy (VMAT), the quality assurance (QA) process is vital. The goal of the study was to verify the treatment planning dose delivered during delivery of complex treatment plans. The QA standard is to perform patientspecific comparisons between planned doses and doses measured in a phantom. Materials and Methods: Ninety-five complex IMRT and VMAT plans for different pathologies planned using Eclipse treatment planning system (TPS). The Octavius 4D phantom has been used to verify patient specific quality assurance of all VMAT plans calculating with different algorithms. Conclusion: Overall, good agreement was observed between measured and calculated doses in most cases with gamma values above 1 in >95% of measured points in volumetric 3D analysis and 1 in >90% in 2D analysis. The Octavius 4D phantom is an effective and efficient method for patient specific QA.
Journal of Applied Clinical Medical Physics, 2019
PurposeDose volume histogram (DVH)‐based analysis is utilized as a pretreatment quality assurance tool to determine clinical relevance from measured dose which is difficult in conventional gamma‐based analysis. In this study, we report our clinical experience with an ionization‐based transmission detector and model‐based verification system, using DVH analysis, as a comprehensive pretreatment QA tool for complex volumetric modulated arc therapy plans.Methods and MaterialsSeventy‐three subsequent treatment plans categorized into four clinical sites (Head and Neck, Thorax, Abdomen, and Pelvis) were evaluated. The average dose (Dmean) and dose received by 1% (D1) of the planning target volumes (PTVs) and organs at risks (OARs) calculated using the treatment planning system (TPS) were compared to a computed (model‐based) and reconstructed dose, from the measured fluence, using DVH analysis. The correlation between gamma (3% 3 mm) and DVH‐based analysis for targets was evaluated. Further...
Purpose: The authors investigated the performance of several patient-specific intensity-modulated radiation therapy (IMRT) quality assurance (QA) dosimeters in terms of their ability to correctly identify dosimetrically acceptable and unacceptable IMRT patient plans, as determined by an inhouse-designed multiple ion chamber phantom used as the gold standard. A further goal was to examine optimal threshold criteria that were consistent and based on the same criteria among the various dosimeters. Methods: The authors used receiver operating characteristic (ROC) curves to determine the sensitivity and specificity of (1) a 2D diode array undergoing anterior irradiation with field-by-field evaluation, (2) a 2D diode array undergoing anterior irradiation with composite evaluation, (3) a 2D diode array using planned irradiation angles with composite evaluation, (4) a helical diode array, (5) radiographic film, and (6) an ion chamber. This was done with a variety of evaluation criteria for a set of 15 dosimetrically unacceptable and 9 acceptable clinical IMRT patient plans, where acceptability was defined on the basis of multiple ion chamber measurements using independent ion chambers and a phantom. The area under the curve (AUC) on the ROC curves was used to compare dosimeter performance across all thresholds. Optimal threshold values were obtained from the ROC curves while incorporating considerations for cost and prevalence of unacceptable plans. Results: Using common clinical acceptance thresholds, most devices performed very poorly in terms of identifying unacceptable plans. Grouping the detector performance based on AUC showed two significantly different groups. The ion chamber, radiographic film, helical diode array, and anteriordelivered composite 2D diode array were in the better-performing group, whereas the anteriordelivered field-by-field and planned gantry angle delivery using the 2D diode array performed less well. Additionally, based on the AUCs, there was no significant difference in the performance of any device between gamma criteria of 2%/2 mm, 3%/3 mm, and 5%/3 mm. Finally, optimal cutoffs (e.g., percent of pixels passing gamma) were determined for each device and while clinical practice commonly uses a threshold of 90% of pixels passing for most cases, these results showed variability in the optimal cutoff among devices. Conclusions: IMRT QA devices have differences in their ability to accurately detect dosimetrically acceptable and unacceptable plans. Field-by-field analysis with a MapCheck device and use of the MapCheck with a MapPhan phantom while delivering at planned rotational gantry angles resulted in a significantly poorer ability to accurately sort acceptable and unacceptable plans compared with the other techniques examined. Patient-specific IMRT QA techniques in general should be thoroughly evaluated for their ability to correctly differentiate acceptable and unacceptable plans. Additionally, optimal agreement thresholds should be identified and used as common clinical thresholds typically worked very poorly to identify unacceptable plans. C 2014 American Association of Physicists in Medicine. [http://dx.
Onkologia i Radioterapia, 2021
The aim of this work is to investigate the dose verification of common conventional Intensity Modulated Radiation Therapy (IMRT) Quality Assurance (QA) performance metric using verisoft software. Based on Gamma index analysis we performed a comparison between 2D and 3D of the delivered and planed dose for complex geometry, Gamma index passing rate (GP%) is calculated using different criteria 3%/3 mm, 3%/2 mm and 2%/2mm dose difference/ distance-to-tolerance criteria (DD/DTA) to check the quality the plan before starting the treatment. Materials and methods: Ten complex Intensity Modulated Radiation Therapy (IMRT) (80 beams) plans for two different pathologies are calculated using the Eclipse Treatment Planning System (TPS), Pre-treatment verifications were performed for all patients plans by acquiring planar dose distributions of each treatment field with 2D-diode array Octavius 4D cylindrical phantom that is matrix composed of 1500 ionisation chambers with a size of 4.4 × 4.4× 3 mm3, whose centres are separated two by two by 7.07 mm. Measured dose and calculated dose were compared by using Gamma index method, and pass/failed test were generated foe each pair of planar doses using the following acceptance criteria 3%/3 mm, 3%/2 mm and 2%/2mm. During the pre-treatment verification we acquired the dose distribution with DICOM RT plan, RT stricter set, and RT dose file from TPS, and then we loaded all plans into the verisoft softwar to analyse each individual plan. Results: Overall, a good correlation was observed between the measured and calculated doses in most of the beams with success agreement of the Gamma index for 3D analysis being 99% compared to 2D which was 97.11% for the 3%/3mm criterion. The average difference in the percentage of passing pixels between the 2D and 3D analyses ranged from 0.9% to 2%.
Annals of Tropical Medicine and Public Health
Background: Step and shoot (SS) IMRT treatment technique is one of the modern planning techniques used in radiotherapy. It conforms to the dose to the possible minimum as to the OARs. Dosimetric error calculations used to estimate the sensitivity of reading and the dose difference between TPS and phantom detector. Monitor units (MUs) are measured by monitor chambers, which are ionization chambers that measure the dose delivered by a beam and are built into the treatment head of radiotherapy linear accelerators. Material and Method: Thirty cases of two regions (25 HN and 5 pelvic cases) performed with SS IMRT using MONACO5.1 Treatment Planning System (TPS). Then the QA tested using OCTAVIUS 4D-1500 phantom in Baghdad Center for Radiotherapy and Nuclear Medicine, Baghdad, Iraq. Gamma index and %GP calculated index by comparing the actual QA (using Octavius) with virtual QA (using MONACO TPS). Dosimetric error percentage with global and local %GP and the total Monitor Unit (MU) correlation with global and local %GP were measured. Results: The %GP was ≥95%, where 20% for local %GP for all cases and 73.3 % for global passing rate. A significant correlation found between the %DEs resulted in the %GP for both local and global. There was a correlation between the total MUs for global %GP. For a local %GP, it was statistically not correlated with MUs. Conclusion: There is a correlation found between dosimetric error percentage (%DE) and %GP for both local and global. There is a correlation between the total Monitor Unit (MU) and global %GP but not with local.