scholarly journals Commissioning Measurements On An Elekta Unity MR-Linac

2021 ◽  
Author(s):  
Marcus Powers ◽  
John Baines ◽  
Robert Crane ◽  
Chantelle Fisher ◽  
Stephen Gibson ◽  
...  
Keyword(s):  
Beam Quality ◽  
Third Party ◽  
Planning System ◽  
Treatment Planning System ◽  
Pixel Intensity ◽  
Imrt Qa ◽  
Specialized Equipment ◽  
Standard Techniques ◽  
Gantry Angle

Abstract MR-guided radiotherapy technology is relatively new and commissioning publications, QA protocols and commercial products are limited. This work provides guidance for implementation measurements that may be performed on the Elekta Unity MR-Linac (Elekta, Stockholm, Sweden). Adaptions of vendor supplied phantoms facilitated determination of gantry angle accuracy and MV isocentre, whereas in-house developed phantoms were used for End-to-End (E2E) testing and anterior coil attenuation measurements. Third-party devices were used for measuring beam quality, reference dosimetry and during IMRT commissioning; however, due to several challenges, variations on standard techniques were required. Gantry angle accuracy was within 0.1°, confirmed with pixel intensity profiles, and MV isocentre diameter was < 0.5 mm. Anterior coil attenuation was < 0.6 %. Beam quality as determined by TPR20,10 was 0.704 ± 0.002, in agreement with treatment planning system (TPS) calculations, and gamma comparison against the TPS for a 22.0 × 22.0 cm2 field was above 95.0 % (2.0 %, 2.0 mm). G90 output was 1.000 ± 0.002 Gy per 100 MU, depth 5.0 cm. During IMRT commissioning, sub-standard results indicated issues with machine behaviour. Once rectified, gamma comparisons were above 95.0 % (2.0 %, 2.0 mm). Centres which may not have access to specialized equipment can use in-house developed phantoms, or adapt those supplied by the vendor, to perform commissioning work and confirm operation of the MRL within published tolerances. The IMRT QA devices and techniques used in this work highlight issues with machine behaviour when appropriate gamma criteria are set.

SU-C-213AB-05: IMRT QA Using R&V Data, Treatment Records, and a Second Treatment Planning System

2012 ◽  
Vol 39 (6Part2) ◽  
pp. 3598-3599
Author(s):  
J Ohrt ◽  
P Balter ◽  
L Court ◽  
M Gillin
Keyword(s):  
Treatment Planning ◽  
Planning System ◽  
Treatment Planning System ◽  
Imrt Qa ◽  
Data Treatment

scholarly journals The dependence of inhomogeneity correction factors on photon beam quality index performed with the Anisotropic Analytical Algorithm

2020 ◽  
Vol 26 (3) ◽  
pp. 127-134
Author(s):  
Md Akhtaruzzaman ◽  
Paweł Kukołowicz
Keyword(s):  
Lung Tissue ◽  
Quality Index ◽  
Beam Quality ◽  
Photon Beam ◽  
Planning System ◽  
Treatment Planning System ◽  
Correction Factors ◽  
Anisotropic Analytical Algorithm ◽  
Inhomogeneity Correction ◽  
Analytical Algorithm

AbstractPurpose: The purpose of the study was to investigate the dependence of tissue inhomogeneity correction factors (ICFs) on the photon beam quality index (QI).Materials and Methods: Heterogeneous phantoms, comprising semi-infinite slabs of the lung (0.10, 0.20, 0.26 and 0.30 g/cm3), adipose tissue (0.92 g/cm3) and bone (1.85 g/cm3) in water, were constructed in the Eclipse treatment planning system. Several calculation models of 6 MV and 15 MV photon beams for quality index (TPR20,10) = 0.670±k*0.01 and TPR20,10 = 0.760±k*0.01, k = -3, -2, -1, 0, 1, 2, 3 respectively were built in the Eclipse. The ICFs were calculated with the anisotropic analytical algorithm (AAA) for several beam sizes and points lying at several depths inside of and below inhomogeneities of different thicknesses.Results: The ICFs increased for lung and adipose tissues with increasing beam quality (TPR20,10), while decreased for bone. Calculations with AAA predict that the maximum difference in ICFs of 1.0% and 2.5% for adipose and bone tissues, respectively. For lung tissue, changes of ICFs of a maximum of 9.2% (6 MV) and 13.8% (15 MV). For points where charged particle equilibrium exists, a linear dependence of ICFs on TPR20,10 was observed. If CPE doesn’t exist, the dependence became more complex. For points inside of the low-density inhomogeneity, the dependence of the ICFs on energy was not linear but the changes of ICFs were smaller than 3.0%. Measurements results carried out with the CIRS phantom were consistent with the calculation results.Conclusions: A negligible dependence of the ICFs on energy was found for adipose and bone tissue. For lung tissue, in the CPE region, the dependence of ICFs on different beam quality indexes with the same nominal energy may not be neglected, however, this dependence was linear. Where there is no CPE, the dependence of the ICFs on energy was more complicated.

Comprehensive evaluation of electron radiation dose using beryllium oxide dosimeters at breast radiotherapy

2019 ◽  
Vol 19 (1) ◽  
pp. 38-44
Author(s):  
Serdar Şahin ◽  
Eren Şahiner ◽  
Fatih Göksel ◽  
Niyazi Meriç
Keyword(s):  
Comprehensive Evaluation ◽  
Absorbed Dose ◽  
Beryllium Oxide ◽  
Left Breast ◽  
Planning System ◽  
Treatment Planning System ◽  
Breast Radiotherapy ◽  
The Mean ◽  
Beam Dose

AbstractIntroduction:In this study, the differences between calculated and measured dose values were then analysed to assess the performance, in terms of accuracy, of the tested treatment planning system (TPS) algorithms applied to calculate electron beam dose targeted and non-targeted the breast region.Materials and methods:The beryllium oxide (BeO) dosimeters placed on the female RANDO phantom were irradiated 12 MeV electron energy with medical linear accelerator and repeatedly read in the Risø thermoluminescence (TL)/optically stimulated luminescence (OSL) system via OSL method at least three times.Results:For electron treatment, one made quantitative comparisons of the dose distributions calculated by TPSs with those from the measurements by OSL at various points in the RANDO phantom.The mean dose measured from the dosimeters placed on the female RANDO phantom target left breast region was 160 cGy and non-target right breast region was 1·2 cGy. Analysis of Generalised Gaussian Pencil Beam (GGPB) and Electron Monte Carlo (eMC) algorithms for determined region mean point dose values, respectively, 174 and 164 cGy. Two algorithms for non-targeted region calculated same point dose values of 0·2 cGy.Conclusions:The results of this study showed that BeO dosimeters can be used with OSL method in radiotherapy applications and it is a very important tool for the determination of targeted/non-targeted absorbed dose.

Selection of gamma analysis acceptance criteria in IMRT QA using Gafchromic EBT3 film dosimetry

2018 ◽  
Vol 18 (02) ◽  
pp. 127-131
Author(s):  
Muhammad Isa Khan ◽  
Muhammad Shakil ◽  
Muhammad Bilal Tahir ◽  
Muhammad Rafique ◽  
Tahir Iqbal ◽  
...  
Keyword(s):  
Intensity Modulated Radiation Therapy ◽  
High Energy ◽  
Planning System ◽  
Treatment Planning System ◽  
Photon Beams ◽  
Energy Photon ◽  
Imrt Qa ◽  
Gamma Analysis ◽  
Varian Medical System ◽  
Selection Of

AbstractBackground and purposeThis study reported the justification and selection of acceptable γ criteria with respect to low (6 MV) and high (15 MV) photon beams for intensity-modulated radiation therapy quality assurance (IMRT QA) using the Gafchromic external beam therapy 3 (EBT3) film.Materials and methodsFive-field step-and-shoot IMRT was used to treat 16 brain IMRT patients using the dual-energy DHX-S linear accelerator (Varian Medical System, Palo Alto, CA, USA). Dose comparisons between computed values of the treatment planning system (TPS) and Gafchromic EBT3 film were evaluated based on γ analysis using the Film QA Pro software. The dose distribution was analysed with gamma area histograms (GAHs) generated using different γ criteria (3%/2 mm, 3%/3 mm and 5%/3 mm) for the 6 and 15 MV photon beams, to optimise the best distance-to-agreement (DTA) criteria with respect to the beam energy.ResultsFrom the comparison between the dose distributions acquired from the TPS and EBT3 film, a DTA criterion of 3%/2 mm showed less dose differences (DDs) with passing rates up to 93% for the 6 MV photon beams, while for the 15 MV a relaxed DTA criterion of 5%/3 mm was consistent with the DD acceptability criteria with a 95% passing rate.ConclusionsOur results suggested that high-energy photon beams required relaxed DTA criteria for the brain IMRT QA, while low-energy photon beams showed better results even with tight DTA criteria.

scholarly journals Curtailing patient-specific IMRT QA procedures from 2D dose error distribution

2016 ◽  
Vol 57 (3) ◽  
pp. 258-264 ◽  
Author(s):  
Keita Kurosu ◽  
Iori Sumida ◽  
Hirokazu Mizuno ◽  
Yuki Otani ◽  
Michio Oda ◽  
...  
Keyword(s):  
Error Distribution ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Dose Error ◽  
Imrt Qa ◽  
Pelvic Region ◽  
Measured Dose ◽  
Calculated Dose ◽  
Medical Physicists

Abstract A patient-specific quality assurance (QA) test is conducted to verify the accuracy of dose delivery. It generally consists of three verification processes: the absolute point dose difference, the planar dose differences at each gantry angle, and the planar dose differences by 3D composite irradiation. However, this imposes a substantial workload on medical physicists. The objective of this study was to determine whether our novel method that predicts the 3D delivered dose allows certain patient-specific IMRT QAs to be curtailed. The object was IMRT QA for the pelvic region with regard to point dose and composite planar dose differences. We compared measured doses, doses calculated in the treatment planning system, and doses predicted by in-house software. The 3D predicted dose was reconstructed from the per-field measurement by incorporating the relative dose error distribution into the original dose grid of each beam. All point dose differences between the measured and the calculated dose were within ±3%, whereas 93.3% of them between the predicted and the calculated dose were within ±3%. As for planar dose differences, the gamma passing rates between the calculated and the predicted dose were higher than those between the calculated and the measured dose. Comparison and statistical analysis revealed a correlation between the predicted and the measured dose with regard to both point dose and planar dose differences. We concluded that the prediction-based approach is an accurate substitute for the conventional measurement-based approach in IMRT QA for the pelvic region. Our novel approach will help medical physicists save time on IMRT QA.

scholarly journals Evaluation of MU2net as an Online Secondary Dose Check for MR Guided Radiation Therapy with the Elekta Unity MR Linac

2021 ◽  
Author(s):  
John Baines ◽  
Ariadne Shoobridge
Keyword(s):  
Dose Calculation ◽  
Measured Data ◽  
Reference Points ◽  
Planning System ◽  
Treatment Planning System ◽  
Computational Accuracy ◽  
Adaptive Workflow ◽  
Step And Shoot ◽  
Secondary Dose ◽  
Gantry Angle

Abstract During the adaptive workflow associated with MRgRT, a secondary dose calculation is required and MU2net (DOSIsoft, France) is one commercial option. The suitability of MU2net to be used in conjunction with the online Monaco treatment planning system of the Elekta Unity (Elekta AB, Stockholm, Sweden), is evaluated in this work. Monaco and MU2net point doses are compared for various fields on and off axis and at different SSDs. To investigate the comparative effects of attenuation due to the cryostat, couch and posterior coil, measured, MU2net and Monaco dose outputs at the isocentre, as a function of gantry angle, were compared. Point doses for the beams of nine step and shoot IMRT (SSIMRT) test plans (courtesy Elekta) were calculated with Monaco v5.4 and compared to corresponding doses computed with MU2net. In addition, Monaco v5.4 and MU2net point doses were compared for 1552 beams treated on the Unity at our facility. For the on-axis fields investigated the agreement between MU2net and measured data is acceptable. MU2net and Monaco point doses for the Elekta SSIMRT test plans were within ± 5.0 % and ± 6.4 % for beams delivered from gantry zero and at planned beam angles, respectively. For the 1552 beams delivered approximately 80.0 % of MU2net and Monaco point doses agree within ± 5.0 %, therefore it is recommended to correlate MU2net Dose Reference Points (DRPs )with pre and post treatment dosimetry verification. Computational accuracy of MU2net could be enhanced with improved modelling of attenuation due to the couch, cryostat and posterior MR imaging coil.

Determination of computed tomography number of high-density materials in 12-bit, 12-bit extended and 16-bit depth for dosimetric calculation in treatment planning system

2019 ◽  
Vol 18 (03) ◽  
pp. 285-294
Author(s):  
Jayapramila Jayamani ◽  
Noor Diyana Osman ◽  
Abdul Aziz Tajuddin ◽  
Zaker Salehi ◽  
Mohd Hanafi Ali ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Treatment Planning ◽  
Region Of Interest ◽  
High Density ◽  
Planning System ◽  
Treatment Planning System ◽  
Tube Voltage ◽  
Ct Number ◽  
Significant Difference

AbstractAimThe main aim was to examine the effect of bit depth on computed tomography (CT) number for high-density materials. Analysis of the CT number for high-density materials using 16-bit scanners will extend the CT scale that currently exists for 12-bit scanners and thus will be beneficial for use in CT–electron density (ED) curve in radiotherapy treatment planning system (TPS). Implementation of this extended CT scale will compensate for tissue heterogeneity during CT–ED conversion in treatment planning.Materials and methodsAn in-house built phantom with 10 different metal samples was scanned using 80, 100 and 120 kVp in two different CT scanners. A region of interest was set at the centre of the material and the mean CT numbers together with data deviation were determined. Dosimetry calculation was performed by applying a direct anterior beam on 12-bit, 12-bit extended and 16-bit.ResultsHigh-density materials (&gt;4·34 g cm−3) in 16-bit depth provide disparities up to 44% compared to Siemens’ 12-bit extended. Influence of tube voltage showed a significant difference (p&lt;0·05) in both bit depth and CT number of the gold and amalgam saturated in 16-bit depth. A 120 kVp energy illustrated a low variation on CT number for different scanners, but dosimetry calculation showed significant disparities at the metal interface in 12-bit, 12-bit extended and 16-bit.FindingsHigh-density materials require 16-bit scanners to obtain CT number to be implemented in treatment planning in radiotherapy. This also suggests that proper tube voltage together with correct CT–ED resulted in accurate TPS algorithm calculation.

PRE-TREATMENT IMRT QA USING PORTAL IMAGING AND THE PINNACLE TREATMENT PLANNING SYSTEM

2009 ◽  
Vol 92 ◽  
pp. S215-S216
Author(s):  
R. Monshouwer ◽  
M. Luesink ◽  
H. Huizenga ◽  
K. Pasma
Keyword(s):  
Treatment Planning ◽  
Planning System ◽  
Treatment Planning System ◽  
Portal Imaging ◽  
Imrt Qa ◽  
Pre Treatment
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