Retrospective analysis of portal dosimetry pre-treatment quality assurance of intracranial SRS/SRT VMAT treatment plans

2021 ◽  
pp. 1-13
Author(s):  
Ernest Osei ◽  
Sarah Graves ◽  
Johnson Darko
Keyword(s):  
Quality Assurance ◽  
Retrospective Analysis ◽  
Low Dose ◽  
Treatment Quality ◽  
Patient Specific ◽  
Portal Dosimetry ◽  
Treatment Plans ◽  
The Mean ◽  
Pre Treatment ◽  
Action Levels

Abstract Background: The complexity associated with the treatment planning and delivery of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) volumetric modulated arc therapy (VMAT) plans which employs continuous dynamic modulation of dose rate, field aperture and gantry speed necessitates diligent pre-treatment patient-specific quality assurance (QA). Numerous techniques for pre-treatment VMAT treatment plans QA are currently available with the aid of several different devices including the electronic portal imager (EPID). Although several studies have provided recommendations for gamma criteria for VMAT pre-treatment QA, there are no specifics for SRS/SRT VMAT QA. Thus, we conducted a study to evaluate intracranial SRS/SRT VMAT QA to determine clinical action levels for gamma criteria based on the institutional estimated means and standard deviations. Materials and methods: We conducted a retrospective analysis of 118 EPID patient-specific pre-treatment QA dosimetric measurements of 47 brain SRS/SRT VMAT treatment plans using the integrated Varian solution (RapidArcTM planning, EPID and Portal dosimetry system) for planning, delivery and EPID QA analysis. We evaluated the maximum gamma (γmax), average gamma (γave) and percentage gamma passing rate (%GP) for different distance-to-agreement/dose difference (DTA/DD) criteria and low-dose thresholds. Results: The gamma index analysis shows that for patient-specific SRS/SRT VMAT QA with the portal dosimetry, the mean %GP is ≥98% for 2–3 mm/1–3% and Field+0%, +5% and +10% low-dose thresholds. When applying stricter spatial criteria of 1 mm, the mean %GP is >90% for DD of 2–3% and ≥88% for DD of 1%. The mean γmax ranges: 1·32 ± 1·33–2·63 ± 2·35 for 3 mm/1–3%, 1·57 ± 1·36–2·87 ± 2·29 for 2 mm/1–3% and 2·36 ± 1·83–3·58 ± 2·23 for 1 mm/1–3%. Similarly the mean γave ranges: 0·16 ± 0·06–0·19 ± 0·07 for 3 mm/1–3%, 0·21 ± 0·08–0·27 ± 0·10 for 2 mm/1–3% and 0·34 ± 0·14–0·49 ± 0·17 for 1 mm/1–3%. The mean γmax and mean γave increase with increased DTA and increased DD for all low-dose thresholds. Conclusions: The establishment of gamma criteria local action levels for SRS/SRT VMAT pre-treatment QA based on institutional resources is imperative as a useful tool for standardising the evaluation of EPID-based patient-specific SRS/SRT VMAT QA. Our data suggest that for intracranial SRS/SRT VMAT QA measured with the EPID, a stricter gamma criterion of 1 mm/2% or 1 mm/3% with ≥90% %GP could be used while still maintaining an in-control QA process with no extra burden on resources and time constraints.

Retrospective analysis of portal dosimetry pre-treatment quality assurance of hybrid IMRT breast treatment plans

2020 ◽  
pp. 1-8
Author(s):  
Meghan Koo ◽  
Johnson Darko ◽  
Ernest Osei
Keyword(s):  
Quality Assurance ◽  
Treatment Quality ◽  
Control Points ◽  
Calculation Algorithm ◽  
Positioning Errors ◽  
Passing Rate ◽  
Portal Dosimetry ◽  
Treatment Plans ◽  
Pre Treatment ◽  
Gamma Passing Rate

Abstract Background: The purpose of this study is to evaluate the effectiveness and sensitivity of the Varian portal dosimetry (PD) system as a quality assurance (QA) tool for breast intensity-modulated radiation therapy (IMRT) treatment plans. Materials and methods: Four hundred portal dose images from 200 breast cancer patient IMRT treatment plans were analysed. The images were obtained using Varian PortalVision electronic portal imaging devices (EPIDs) on Varian TrueBeam Linacs. Three patient plans were selected, and the multi-leaf collimator (MLC) positions were randomly altered by a mean of 0·5, 1, 1·5 and 2 mm with a standard deviation of 0·1 mm on 50, 75 and 100% of control points. Using the improved/global gamma calculation algorithm with a low-dose threshold of 10% in the EPID, the change in gamma passing rates for 3%/3 mm, 2%/2 mm and 1%/1 mm criterion was analysed as a function of the introduced error. The changes in the dose distributions of clinical target volume and organ at risk due to MLC positioning errors were also analysed. Results: Symmetric and asymmetric breast or chest wall plan fields are different in delivery as well as in the QA. An average gamma passing rate of 99·8 ± 0·5 is presented for 3%/3 mm symmetric plans and 96·9 ± 4·5 is presented for 3%/3 mm asymmetric plans. An average gamma passing rate of 98·4 ± 4·3 is presented for 2%/2 mm symmetric plans and 89·7 ± 9·5 is presented for 2%/2 mm asymmetric plans. A large-induced error in MLC positioning (2·0 mm, 100% of control points) results in an insignificant change in dose that would be delivered to the patient. However, EPID portal dosimetry is sensitive enough to detect even the slightest change in MLC positioning error (0·5 mm, 50% of control points). Conclusions: Stricter pre-treatment QA action levels can be established for breast IMRT plans utilising EPID. For improved sensitivity, a multigamma criteria approach is recommended. The PD tool is sensitive enough to detect MLC positioning errors that contribute to even insignificant dose changes.

scholarly journals Portal Dosimetry as a patient specific Quality Assurance tool for Volumetric Arc Radiotherapy

2021 ◽  
Vol 9 (1) ◽  
pp. 29-33
Author(s):  
Vikram Rathore ◽  
◽  
Mr. V.K Mishra ◽  
Dr. V Choudhary ◽  
Mr. G.S. Gautam ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Patient Specific ◽  
Advanced Technique ◽  
Mean Values ◽  
Treatment Patient ◽  
Portal Dosimetry ◽  
Gamma Index ◽  
Patient Specific Qa ◽  
The Mean ◽  
Pre Treatment

Introduction: Volumetric Arc Radiotherapy (VMAT) is an advanced technique. Calculations of VMATplans are not so accurate even with State-of-Art dose calculation algorithms due to their complexity.Hence pre-treatment patient specific Quality Assurance (QA) of each VMAT plan is required. In thepresent study Electronic Portal Imaging Device (EPID) based portal dosimetry system was used forpre-treatment patient specific QA. Material and Methods: A total of 50 patients were chosen inthis study. Verification plans of each patient were calculated for portal dosimetry then executed onthe EPID system to measure the spatial distribution of radiation dose. Calculated and measured dosedistribution were compared to evaluate Gamma Index (GI) passing criteria of Dose Difference (DD)of 3% and Distance–to-Agreement (DTA) of 3mm, Area Gamma (γ% ≤1) >95%, Average Gamma(gAve) <0.5% and Maximum Gamma (gMax) <3.5%. Results: The mean values of Area Gamma (γ%≤1) were observed to be varied from 99.14±0.23% to 99.87±0.18%. The Mean Values of AverageGamma (gAve) are found to vary from 0.19±0.05% to 0.15±0.04% and the mean values ofMaximum Gamma (gMax) found to be varied from 1.94±0.37% to 1.59±0.41%. All the plans werepassed the gamma index criteria with very good agreement. Thus the use of Portal Dosimetry forpre-treatment patient QA is found to be a very useful, quick, precise, efficient and effective pre-treatment patient specific QA tool for VMAT treatment. Conclusion: Portal Dosimetry can be utilizedfor routine use for patient specific quality assurance for Volumetric Arc Radiotherapy treatment.

scholarly journals Analysis of Clinical Patient-Specific Pre-Treatment Quality Assurance with the New Helical TomoTherapy® Platform, following the AAPM TG-218 Report

2021 ◽  
Author(s):  
Marco Fusella ◽  
Samuele Cavinato ◽  
Alessandra Germani ◽  
Marta Paiusco ◽  
Nicola Pivato ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Helical Tomotherapy ◽  
Treatment Quality ◽  
Patient Specific ◽  
Mean Values ◽  
Clinical Patient ◽  
Passing Rate ◽  
Pre Treatment ◽  
Delivery Accuracy ◽  
Global And Local

Abstract Purpose: This study presents patient-specific quality assurance (QA) results from the first 395 clinical cases for the new helical TomoTherapy® platform (Radixact) coupled with dedicated Precision TPS.Methods: The passing rate of the Gamma Index (GP%) of 395 helical QA of patient-specific Tomotherapy, acquired with ArcCHECK, is presented, analysed and correlated to various parameters of the plan. Following TG-218 recommendations, the clinic specific action limit (ALcs) and tolerance limit (TLcs) were calculated for our clinic and monitored during the analysed period.Results: the mean values ​​(± 1 standard deviation) of GP% (3% / 2mm) (both global and local normalization) are: 97.6% and 90.9%, respectively. The proposed ALcs and TLcs, after a period of two years’ process monitoring are 89.4% and 91.1% respectively.Conclusions: The phantom measurements closely match the planned dose distributions, demonstrating that the calculation accuracy of the new Precision TPS and the delivery accuracy of the Radixact unit are adequate, with respect to international guidelines and reports. Furthermore, a first correlation with the planning parameters was made. Action and tolerance limits have been set for the new Radixact Linac.

SU-E-T-134: Patient Specific Quality Assurance of RapidArc Pre Treatment Plans Using Semiflex 0.125 Cc Ionization Chamber

2012 ◽  
Vol 39 (6Part11) ◽  
pp. 3734-3734
Author(s):  
SA Syam Kumar ◽  
S Prabakar ◽  
P Sriram ◽  
N Vivekanandan
Keyword(s):  
Quality Assurance ◽  
Ionization Chamber ◽  
Patient Specific ◽  
Treatment Plans ◽  
Pre Treatment

203. Patient specific pre-treatment Quality Assurance in multiple lesions lung SBRT VMAT plans

2018 ◽  
Vol 56 ◽  
pp. 185
Author(s):  
S. Linsalata ◽  
V. Ravaglia ◽  
L. Paladini ◽  
A. Tofani
Keyword(s):  
Quality Assurance ◽  
Treatment Quality ◽  
Patient Specific ◽  
Multiple Lesions ◽  
Lung Sbrt ◽  
Pre Treatment

scholarly journals Analysis of clinical patient-specific pre-treatment quality assurance with the new helical tomotherapy platform, following the AAPM TG-218 report

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Marco Fusella ◽  
Samuele Cavinato ◽  
Alessandra Germani ◽  
Marta Paiusco ◽  
Nicola Pivato ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Helical Tomotherapy ◽  
Treatment Quality ◽  
Patient Specific ◽  
Mean Values ◽  
Clinical Patient ◽  
Passing Rate ◽  
Pre Treatment ◽  
Delivery Accuracy ◽  
Global And Local

Abstract Purpose This study presents patient-specific quality assurance (QA) results from the first 395 clinical cases for the new helical TomoTherapy® platform (Radixact) coupled with dedicated Precision TPS. Methods The passing rate of the Gamma Index (GP%) of 395 helical QA of patient-specific tomotherapy, acquired with ArcCHECK, is presented, analysed and correlated to various parameters of the plan. Following TG-218 recommendations, the clinic specific action limit (ALcs) and tolerance limit (TLcs) were calculated for our clinic and monitored during the analysed period. Results The mean values ​​(± 1 standard deviation) of GP% (3%/2 mm) (both global and local normalization) are: 97.6% and 90.9%, respectively. The proposed ALcs and TLcs, after a period of two years’ process monitoring are 89.4% and 91.1% respectively. Conclusions The phantom measurements closely match the planned dose distributions, demonstrating that the calculation accuracy of the new Precision TPS and the delivery accuracy of the Radixact unit are adequate, with respect to international guidelines and reports. Furthermore, a first correlation with the planning parameters was made. Action and tolerance limits have been set for the new Radixact Linac.

Fraction-specific post-treatment quality assurance for active breath-hold radiation therapy

2019 ◽  
Vol 18 (03) ◽  
pp. 262-270
Author(s):  
Rajesh Thiyagarajan ◽  
Arunai Nambiraj ◽  
Durai Manigandan ◽  
Tamilseivan Singaravelu ◽  
Rajesh Selvaraj ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Post Treatment ◽  
Patient Comfort ◽  
Treatment Quality ◽  
Patient Specific ◽  
Breath Hold ◽  
Therapist Communication ◽  
Dosimetric System

AbstractPurposeThe purpose of this study is to evaluate variation in the treatment hold pattern and quantify its dosimetric impact in breath-hold radiotherapy, using fraction-specific post-treatment quality assurance.Material and MethodsA patient with lung mets treated using intensity-modulated radiation therapy (IMRT) with active breath coordinator (ABC) was recruited for the study. Treatment beam hold conditions were recorded for all the 25 fractions. The linearity and reproducibility of the dosimetric system were measured. Variation in the dose output of unmodulated open beam with beam hold was studied. Patient-specific quality assurance (PSQA) was performed with and without beam hold, and the results were compared to quantify the dosimetric impact of beam hold.ResultsThere was a considerable amount of variation observed in the number of beam hold for the given field and the monitor unit at which the beam held. Linearity and reproducibility of the dosimetric system were found within the acceptable limits. The average difference over the 25 measurements was 0·044% (0·557 to −0·318%) with standard deviation of 0·248.ConclusionPatient comfort with the ABC system and responsiveness to the therapist communication help to maintain consistent breathing pattern, in turn consistent treatment delivery pattern. However, the magnitude of dosimetric error is much less than the acceptable limits recommended by IROC. The dosimetric error induced by the beam hold is over and above the dose difference observed in conventional PSQA.

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