Electron Beam Profile Assessment of Linear Accelerator Using Startrack Quality Assurance Device
01 Mar 2021-Vol. 1829, Iss: 1, pp 012015
TL;DR: It is concluded that StarTrack 2D array detector is favourable in the QA process because their implementation is not only easy, but gives information about the beam’s temporal stability and is particularly suitable for beam steering mounting.
Abstract: Electron beam therapy using linear accelerator done for patients with superficial cancerous tumors. Daily quality assurance is preferable to assess a good treatment for the patients. This study focuses on penumbra, flatness, and symmetry determination for four types of an electron beam using StarTrack 2D array for quality assurance. Eelectron beam with energies: 6MeV, 9MeV, 12 MeV, and 15MeV for both in-plane (x-axis) and cross-plane (y-axis) using Elekta synergy linac exposed to StarTrack 2D array readings during 16 weeks for testing the performance and stability of StarTrack. The testing protocol used is IEC.The beam profile estimation of variation, when compared with standard values of penumbra, flatness, and symmetry of electron beam energy at the time of commissioning, reveals that all had a variation but these variations are within the limits. It is concluded that StarTrack 2D array detector is favourable in the QA process. Their implementation is not only easy, but gives information about the beam’s temporal stability and is particularly suitable for beam steering mounting.
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TL;DR: 3 mm or less grid sizes should be routinely used in pre-treatment verification procedure IMRT plans using 2D Array Detectors, suggesting the gamma criteria of 5% DD and 5 mm DTA as the most suitable criteria for IMRT quality assurance.
Abstract: Aim: The main aim of our study was to compare the variation of Gamma Index (GI) in Pre-treatment Verification Procedure in Intensity Modulated Radiotherapy (IMRT) Plans with Varying Grid Sizes Using 2D Array Detectors. Choosing an optimum grid size plays a vital role for planning in radiotherapy cases especially while treating with IMRT. A minimal change of even 1 mm of grid size can result in large variation in treatment planning and is reflected in quality assurance results also.
Methods and Material: We compared IMRT plans for a total of 12 patients. Out of these 12 patients 4 were head and neck, 4 were pelvic and 4 were brain patients respectively. For each patient three plans were generated with three different grid sizes. The plan acceptance criteria were 95% of PTV to receive at least 95% of prescribed dose and dose to 1% of PTV not to exceed 107% of prescribed dose. Dose for the organs at risk were respected as per the QUANTEC guidelines. After plan acceptance corresponding Pre-treatment Verification Procedure for IMRT was executed by PTW 729 array detector. The Gamma index (GI) results of each plan were recorded for the three different grid sizes. The passing criteria were kept to be 3% Dose Difference (DD) and 3 mm Distance to Agreement (DTA) for all cases.
Results: We estimated the variations in GI quality assurance results for patients undergoing IMRT planning with varying grid sizes of 3 mm, 5 mm and 10 mm respectively. We also evaluated 2% DD and 2 mm DTA, 3% DD, 3 mm DTA and 5% DD, 5 mm DTA criteria for passing result. Stastical analysis: We have calculated the average and standard Deviations (Std. Dev.) for each passing criteria for 2% DD, 2 mm DTA, 3% DD, 3 mm DTA and 5% DD, 5 mm DTA for each IMRT plans with varying grid sizes.
Conclusions: Though the present results suggest the gamma criteria of 5% DD and 5 mm DTA as the most suitable criteria for IMRT quality assurance. This gamma criterion of 5% DD and 5 mm DTA favourably exceeds 95% in each case and grid sizes but it is not recommended for strict verification procedure in Intensity Modulated Radiotherapy (IMRT). The criteria of 2% DD and 2 mm DTA, and 3% DD and 3 mm DTA gamma values show below 90% for 5 mm and 10 mm grid sizes but exceeds 95% for the 3 mm grid sizes. Hence 3 mm or less grid sizes should be routinely used in pre-treatment verification procedure IMRT plans using 2D Array Detectors.
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TL;DR: The task group (TG-142) for quality assurance of medical accelerators accomplished the update to TG-40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator.
Abstract: The task group (TG) for quality assurance of medical accelerators was constituted by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance and Outcome Improvement Subcommittee. The task group (TG-142) had two main charges. First to update, as needed, recommendations of Table II of the AAPM TG-40 report on quality assurance and second, to add recommendations for asymmetric jaws, multileaf collimation (MLC), and dynamic/virtual wedges. The TG accomplished the update to TG-40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator. The imaging devices include x-ray imaging, photon portal imaging, and cone-beam CT. The TG report was designed to account for the types of treatments delivered with the particular machine. For example, machines that are used for radiosurgery treatments or intensity-modulated radiotherapy (IMRT) require different tests and/or tolerances. There are specific recommendations for MLC quality assurance for machines performing IMRT. The report also gives recommendations as to action levels for the physicists to implement particular actions, whether they are inspection, scheduled action, or immediate and corrective action. The report is geared to be flexible for the physicist to customize the QA program depending on clinical utility. There are specific tables according to daily, monthly, and annual reviews, along with unique tables for wedge systems, MLC, and imaging checks. The report also gives specific recommendations regarding setup of a QA program by the physicist in regards to building a QA team, establishing procedures, training of personnel, documentation, and end-to-end system checks. The tabulated items of this report have been considerably expanded as compared with the original TG-40 report and the recommended tolerances accommodate differences in the intended use of the machine functionality (non-IMRT, IMRT, and stereotactic delivery).
1,227 citations
"Electron Beam Profile Assessment of..." refers background in this paper
...2 Quality assurance is all systematic and planned activities are carried out within the quality program that can be shown to assure that the product or service will meet the quality specifications [7-9]....
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TL;DR: This book is a worthwhile addition to the library of any university or hospital department of medical physics, but has a slightly dated feel despite its age.
Abstract: This book, published in 2005 by the International Atomic Energy Agency, is a comprehensive compendium of all of the topics that should be covered by a radiation oncology physics course, from basic physics to dosimetry, commissioning and quality assurance of equipment, treatment planning and radiation protection and safety. It has an extensive section on brachytherapy, some basic radiation biology and a chapter on special procedures and techniques.
As a handbook, as opposed to a textbook, it contains a large number of useful data tables and basic formulae, but in places it does not go deep enough into the issues that are of current concern in the radiotherapy physics community. It has a comprehensive review of various calibration methods for both photon and electron beams, but it does not reproduce the basic tables of the most recent protocols. It also has a reasonably up to date review of the various radiation distribution algorithms employed by modern treatment planning systems, but it does not discuss the advantages and disadvantages of the various approaches.
In general, it is a little disappointing that such a recent publication is not more focused on new developments in radiotherapy and their implications for the physicists' workload. The section on radiation producing equipment is historically inclusive of somewhat outdated models, but it hardly touches on the newer developments, such as cyclotrons or synchrotrons for proton therapy. Multi-leaf Collimators are not even included in this chapter, despite their wide availability, confining them to the special techniques chapter. Virtual simulators are presented alongside conventional ones, but their impact on the treatment planning process is not discussed. The Intensity Modulated Radiation Therapy Section in the otherwise comprehensive section on special procedures is inadequate. Given its great and wide impact on recent practice, one would have expected the Intensity Modulated Radiation Therapy Section to warrant a chapter of its own, with a detailed discussion on the associated quality assurance and its analysis. References to the up and coming heavy particle therapy, such as neutrons, protons and carbon ions, and their physical characteristics, are very sparse.
In summary, this book is a worthwhile addition to the library of any university or hospital department of medical physics, but has a slightly dated feel despite its age.
744 citations
TL;DR: The work that has been done during the first E. van der Schueren fellowship is reported, focusing on four phase III EORTC clinical trials: 22921 for rectal cancer, 22961 and 22991 for prostate cancer and 22922 for breast cancer.
52 citations
"Electron Beam Profile Assessment of..." refers background in this paper
...2 Quality assurance is all systematic and planned activities are carried out within the quality program that can be shown to assure that the product or service will meet the quality specifications [7-9]....
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TL;DR: This publication provides a comprehensive overview of the basic medical physics knowledge required in the form of a syllabus for modern radiation oncology, used to define the level of knowledge expected of medical physicists worldwide.
Abstract: This publication is aimed at students and teachers involved in programmes that train professionals for work in radiation oncology. It provides a comprehensive overview of the basic medical physics knowledge required in the form of a syllabus for modern radiation oncology. It will be particularly useful to graduate students and residents in medical physics programmes, to residents in radiation oncology, as well as to students in dosimetry and radiotherapy technology programmes. It will assist those preparing for their professional certification examinations in radiation oncology, medical physics, dosimetry or radiotherapy technology. It has been endorsed by several international and national organizations, and the material presented has already been used to define the level of knowledge expected of medical physicists worldwide.
40 citations
"Electron Beam Profile Assessment of..." refers background or methods in this paper
...Areas below the Dmax beam profile are alternatively defined on each side (left and right) of the central axis, which extends to 50% (normalized up to 100% at the central axis), and S.B is calculated from [3, 7]....
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...The flatness (beam flatness) is calculated with the maximum (Dmax) and minimum (Dmin) dose points values within the central 80% 0f beam width of the beam profile and then with the references [3, 7]: F....
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...Its results appear in percentages [7]....
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...The flatness (beam flatness) is calculated with the maximum (Dmax) and minimum (Dmin) dose points values within the central 80% 0f beam width of the beam profile and then with the references [3, 7]:...
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...its results appear in (mm) or (cm) [7]....
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TL;DR: The BIS 710 has been used in the current study to develop a QA procedure for measurements of flatness and symmetry of a linac x-ray beam, demonstrating that the technique can pick up the “cold” and “hot” spots in the analysed area, providing thus more information about the radiation beam.
Abstract: The input/output characteristics of the Wellhofer BIS 710 electronic portal imaging device (EPID) have been investigated to establish its efficacy for periodic quality assurance (QA) applications. Calibration curves have been determined for the energy fluence incident on the detector versus the pixel values. The effect of the charge coupled device (CCD) camera sampling time and beam parameters (such as beam field size, dose rate, photon energy) on the calibration have been investigated for a region of interest (ROI) around the central beam axis. The results demonstrate that the pixel output is a linear function of the incident exposure, as expected for a video-based electronic portal imaging system. The field size effects of the BIS 710 are similar to that of an ion chamber for smaller field sizes up to 10 x 10 cm2. However, for larger field sizes the pixel value increases more rapidly. Furthermore, the system is slightly sensitive to dose rate and is also energy dependent. The BIS 710 has been used in the current study to develop a QA procedure for measurements of flatness and symmetry of a linac x-ray beam. As a two-dimensional image of the radiation field is obtained from a single exposure of the BIS 710, a technique has been developed to calculate flatness and symmetry from a defined radiation area. The flatness and symmetry values obtained are different from those calculated conventionally from major axes only (inplane, crossplane). This demonstrates that the technique can pick up the “cold” and “hot” spots in the analysed area, providing thus more information about the radiation beam. When calibrated against the water tank measurements, the BIS 710 can be used as a secondary device to monitor the x-ray beam flatness and symmetry.
27 citations
"Electron Beam Profile Assessment of..." refers background in this paper
...The beam profiles include penumbral region, flatness, and symmetry [7, 18, 19]....
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