SU-GG-T-225: Correction for Directional Response of a 2D Ion Chamber Array for Quality Assurance of Arc Radiotherapy and IMRT

2008 ◽  
Vol 35 (6Part12) ◽  
pp. 2777-2777 ◽  
Author(s):  
BK Teo ◽  
D Hristov ◽  
E Mok ◽  
G Luxton
Keyword(s):  
Quality Assurance ◽  
Directional Response ◽  
Ion Chamber

scholarly journals Leaf Open Time Sinogram (LOTS):  A novel approach for Patient specific quality assurance of Total marrow irradiation

2020 ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
Ganapathy Krishnan ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Dose Distribution ◽  
Upper Body ◽  
Patient Specific ◽  
Reconstruction Method ◽  
Ion Chamber ◽  
Modulation Factor ◽  
Novel Approach ◽  
Open Time ◽  
Total Marrow Irradiation

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for total marrow (TMI) and Lymphoid (TMLI) irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured leaf open time sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98%(D98%) and 2%(D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ±1.8% of planned and IC measurement. The planned dose distribution agrees with reconstructed and ArcCheck measured dose with mean(SD) 3Dγ of 98.7%(1.57%) and 2Dγ of 99.48%(0.81%). The deviation in D98% and D2% were within 1.71% and 4.1% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agrees within ±1.2%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from five upper body TMI/TMLI plans showed mean±SD 2Dγ of 97.82%±1.27%, the reconstruction method resulted poor mean(SD) 3Dγ of 92.00%(±5.83%), 64.80%(±28.28%), 69.20%(±30.46%), 60.80%(±19.37%) and 73.2% (±20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were <3.8% and 9.5%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% <1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.

scholarly journals Evaluation of Delta4DVH Anatomy in 3D Patient-Specific IMRT Quality Assurance

2020 ◽  
Vol 19 ◽  
pp. 153303382094581
Author(s):  
Du Tang ◽  
Zhen Yang ◽  
Xunzhang Dai ◽  
Ying Cao
Keyword(s):  
Quality Assurance ◽  
Treatment Planning ◽  
Treatment Plan ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Pencil Beam ◽  
Ion Chamber ◽  
Passing Rate ◽  
Gamma Passing Rate

Purpose: To evaluate the performance of Delta4DVH Anatomy in patient-specific intensity-modulated radiotherapy quality assurance. Materials and Methods: Dose comparisons were performed between Anatomy doses calculated with treatment plan dose measured modification and pencil beam algorithms, treatment planning system doses, film doses, and ion chamber measured doses in homogeneous and inhomogeneous geometries. The sensitivity of Anatomy doses to machine errors and output calibration errors was also investigated. Results: For a Volumetric Modulated Arc Therapy (VMAT) plan evaluated on the Delta4 geometry, the conventional gamma passing rate was 99.6%. For a water-equivalent slab geometry, good agreements were found between dose profiles in film, treatment planning system, and Anatomy treatment plan dose measured modification and pencil beam calculations. Gamma passing rate for Anatomy treatment plan dose measured modification and pencil beam doses versus treatment planning system doses was 100%. However, gamma passing rate dropped to 97.2% and 96% for treatment plan dose measured modification and pencil beam calculations in inhomogeneous head & neck phantom, respectively. For the 10 patients’ quality assurance plans, good agreements were found between ion chamber measured doses and the planned ones (deviation: 0.09% ± 1.17%). The averaged gamma passing rate for conventional and Anatomy treatment plan dose measured modification and pencil beam gamma analyses in Delta4 geometry was 99.6% ± 0.89%, 98.54% ± 1.60%, and 98.95% ± 1.27%, respectively, higher than averaged gamma passing rate of 97.75% ± 1.23% and 93.04% ± 2.69% for treatment plan dose measured modification and pencil beam in patients’ geometries, respectively. Anatomy treatment plan dose measured modification dose profiles agreed well with those in treatment planning system for both Delta4 and patients’ geometries, while pencil beam doses demonstrated substantial disagreement in patients’ geometries when compared to treatment planning system doses. Both treatment planning system doses are sensitive to multileaf collimator and monitor unit (MU) errors for high and medium dose metrics but not sensitive to the gantry and collimator rotation error smaller than 3°. Conclusions: The new Delta4DVH Anatomy with treatment plan dose measured modification algorithm is a useful tool for the anatomy-based patient-specific quality assurance. Cautions should be taken when using pencil beam algorithm due to its limitations in handling heterogeneity and in high-dose gradient regions.

scholarly journals Factor 10 Expedience of Monthly Linac Quality Assurance via an Ion Chamber Array and Automation Scripts

2019 ◽  
Vol 18 ◽  
pp. 153303381987689
Author(s):  
Lawrie B. Skinner ◽  
Yong Yang ◽  
Annie Hsu ◽  
Lei Xing ◽  
Amy S. Yu ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Standard Deviation ◽  
Linear Accelerator ◽  
Data File ◽  
Field Size ◽  
Linear Accelerators ◽  
Ion Chamber ◽  
Medical Linear Accelerators ◽  
Jaw Position ◽  
Dosimetric Leaf Gap

Purpose: While critical for safe and accurate radiotherapy, monthly quality assurance of medical linear accelerators is time-consuming and takes physics resources away from other valuable tasks. The previous methods at our institution required 5 hours to perform the mechanical and dosimetric monthly linear accelerator quality assurance tests. An improved workflow was developed to perform these tests with higher accuracy, with fewer error pathways, in significantly less time. Methods: A commercial ion chamber array (IC profiler, Sun Nuclear, Melbourne, Florida) is combined with automation scripts to consolidate monthly linear accelerator QA. The array was used to measure output, flatness, symmetry, jaw positions, gated dose constancy, energy constancy, collimator walkout, crosshair centering, and dosimetric leaf gap constancy. Treatment plans were combined with automation scripts that interface with Sun Nuclear’s graphical user interface. This workflow was implemented on a standard Varian clinac, with no special adaptations, and can be easily applied to other C-arm linear accelerators. Results: These methods enable, in 30 minutes, measurement and analysis of 20 of the 26 dosimetric and mechanical monthly tests recommended by TG-142. This method also reduces uncertainties in the measured beam profile constancy, beam energy constancy, field size, and jaw position tests, compared to our previous methods. One drawback is the increased uncertainty associated with output constancy. Output differences between IC profiler and farmer chamber in plastic water measurements over a 6-month period, across 4 machines, were found to have a 0.3% standard deviation for photons and a 0.5% standard deviation for electrons, which is sufficient for verifying output accuracy according to TG-142 guidelines. To minimize error pathways, automation scripts which apply the required settings, as well as check the exported data file integrity were employed. Conclusions: The equipment, procedure, and scripts used here reduce the time burden of routine quality assurance tests and in most instances improve precision over our previous methods.

Dosimetric verification and quality assurance for intensity-modulated radiation therapy using Gafchromic® EBT3 film

2017 ◽  
Vol 17 (1) ◽  
pp. 85-95 ◽  
Author(s):  
Khalid Iqbal ◽  
Muhammad Mazhar Iqbal ◽  
Muhammad Akram ◽  
Saima Altaf ◽  
Saeed Ahmad Buzdar
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Imrt Qa ◽  
Ion Chamber ◽  
Intensity Modulated ◽  
Dosimetric Verification ◽  
Therapy Quality ◽  
Dosimetric Assessment ◽  
Radiation Therapy Quality Assurance

AbstractPurposeThis study aimed to examine the dosimetric properties of Gafchromic® EBT3 film and intensity-modulated radiation therapy quality assurance (IMRT QA).Materials and methodsBeams characteristics dosimetric properties and 20 IMRT plans were created and irradiated on Varian dual-energy DHX-S Linac for 6 and 15 MV energies. EBT3 films were analysed using ‘film Pro QA 2014’ software.ResultsThe dosimetric comparison of EBT3 film (for red channel dosimetry) and ionisation ion chamber measurement showed that average deviations of symmetry, flatness, central axis, penumbra (left) and penumbra (right) of dose profile were 0·18, 1·34, 0·49%, 3·68 and 3·61 mm for 6 MV and 0·10, 1·3, 0·45, 2·65 and 2·71 mm for 15 MV, respectively. The blue and green channels dosimetry showed greater dose deviation as compared with red channel. IMRT QA verification plan complied about 95% at all different criteria. Reproducibility, stability and face orientation of film were within 1·4% for red channel.ConclusionsThe results advocate that the film can be used not only for dosimetric assessment but also as a reliable IMRT QA tool.

scholarly journals A management method for the statistical results of patient-specific quality assurance for intensity-modulated radiation therapy

2016 ◽  
Vol 58 (4) ◽  
pp. 572-578
Author(s):  
Satoshi Nakamura ◽  
Hiroyuki Okamoto ◽  
Akihisa Wakita ◽  
Rei Umezawa ◽  
Kana Takahashi ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Intensity Modulated Radiation Therapy ◽  
Tolerance Limit ◽  
Patient Specific ◽  
Ion Chamber ◽  
Intensity Modulated ◽  
Patient Specific Qa ◽  
Management Method ◽  
Statistical Results ◽  
Dose Difference

Abstract There are many reports concerning patient-specific quality assurance (QA) for intensity-modulated radiation therapy (IMRT). However, reports about the statistical results of QA are lacking. Management methods for the results of the QA are needed, even though we have the ESTRO group recommendation that a tolerance limit of 1.96 standard deviation (SD) be established in each institution. The purpose of this study was to establish a management method for determining the tolerance limit and to report the statistical results of patient-specific QA. From April 2006 to March 2015, five linacs in the National Cancer Center, Tokyo, Japan, were used to treat 1185 patients with IMRT. Patient-specific QA was performed using an ion chamber, films, and some detectors. To establish a management method for the results, differences between the measured and calculated doses in the ion chamber were analyzed for each linac, each phantom, and each treatment site. The overall mean dose difference was 0.5 ± 1.3%, and the mean dose difference in each linac was 0.6 ± 1.2%, 0.9 ± 1.3%, −0.4 ± 1.4%, −0.1 ± 1.2% and −0.1 ± 0.9%. The difference between linacs and between treatment sites was significant (P &lt; 0.001 and 0.01, respectively). The proportion of the dose difference within ±3% was 97.7%, and that was improved from 2006 to 2014. The results of the patient-specific QA should be managed for each linac and each treatment site in order to decide the suitable tolerance limit. Reports of statistical results will be helped if a new tolerance limit and action level will be considered.

On-line quality assurance of rotational radiotherapy treatment delivery by means of a 2D ion chamber array and the Octavius phantom

2007 ◽  
Vol 34 (10) ◽  
pp. 3825-3837 ◽  
Author(s):  
Ann Van Esch ◽  
Christian Clermont ◽  
Magali Devillers ◽  
Mauro Iori ◽  
Dominique P. Huyskens
Keyword(s):  
Quality Assurance ◽  
Treatment Delivery ◽  
Ion Chamber ◽  
On Line ◽  
Radiotherapy Treatment
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