Quality Assurance Of Treatment Planning Systems Research Articles

A noise correction of the γ-index method for Monte Carlo dose distribution comparison.

Due to the increasing complexity of IMRT/IMPT treatments, quality assurance (QA) is essential to verify the quality of the dose distribution actually delivered. In this context, Monte Carlo (MC) simulations are more and more often used to verify the accuracy of the treatment planning system (TPS). The most common method of dose comparison is the γ-test, which combines dose difference and distance-to-agreement (DTA) criteria. However, this method is known to be dependent on the noise level in dose distributions. We propose here a method to correct the bias of the γ passing rate (GPR) induced by MC noise. The GPR amplitude was studied as a function of the MC noise level. A model of this noise effect was mathematically derived. This model was then used to predict the time-consuming low-noise GPR by fitting multiple fast MC dose calculations. MC dose maps with a noise level between 2% and 20% were computed, and the GPR was predicted at a noise level of 0.3%. Due to the asymmetry of the γ-test, two different cases were considered: the MC dose was first set as reference dose, then as evaluated dose in the γ-test. Our method was applied on six proton therapy plans including analytical doses from the TPS or patient-specific QA measurements. An average absolute error of 4.31% was observed on the GPR computed for MC doses with 2% statistical noise. Our method was able to improve the accuracy of the gamma passing rate by up to 13%. The method was found especially efficient to correct the noise bias when the DTA criterion is low. We propose a method to enhance the γ-evaluation of a treatment plan when there is noise in one of the compared distributions. The method allows, in a tractable time, to detect the cases for which a correction is necessary and can improve the accuracy of the resulting passing rates.

Determination of task group 43 dosimetric parameters for CSM40 137Cs source for use in brachytherapy.

The CSM40 137Cs source model is currently being used in clinical brachytherapy. According to the recommendations of task group No. 43 (TG-43) of the American Association of Physicists in Medicine, dosimetry parameters of brachytherapy sources should be determined by two independent investigators before their clinical use. The aim of this study was to determine the TG-43 dosimetry parameters for a medium-dose-rate CSM40 137Cs source. The determined dosimetric parameters included the air kerma strength, dose rate constant, radial dose function, and anisotropy function. To determine the source's dosimetric parameters, the CSM40 source was stimulated by the Monte Carlo N-Particle MCNP code. The TG-43 parameters were compared with the data of Vijande et al. on this source. The results showed that the dosimetry parameters for this source had good agreement with the results of Vijande et al. The dosimetric parameters of the CSM40 source can be used in treatment-planning systems incorporating this source model. The data can also be used for the quality assurance of treatment-planning systems.

WE-AB-201-00: Treatment Planning System Commissioning and QA

WE-AB-201-00: Treatment Planning System Commissioning and QA

WE-AB-201-02: TPS Commissioning and QA: A Process Orientation and Application of Control Charts

WE-AB-201-02: TPS Commissioning and QA: A Process Orientation and Application of Control Charts

WE-AB-201-01: Treatment Planning System Commissioning and QA: Challenges and Opportunities

WE-AB-201-01: Treatment Planning System Commissioning and QA: Challenges and Opportunities

WE-AB-201-04: The Recommendations of MPPG #5 and Practical Implementation Strategies

WE-AB-201-04: The Recommendations of MPPG #5 and Practical Implementation Strategies

SU‐E‐P‐05: Is Routine Treatment Planning System Quality Assurance Necessary?

Purpose:To evaluate the variation of dose calculations using a treatment planning system (TPS) over a two year period and assessment of the need for TPS QA on regular intervals.Methods:Two phantoms containing solid water and lung‐ and bone‐equivalent heterogeneities were constructed in two different institutions for the same brand treatment planning system. Multiple plans, consisting of photons and electron beams, including IMRT and VMAT ones, were created and calculated on the phantoms. The accuracy of dose computation in the phantoms was evaluated at the onset by dose measurements within the phantoms. The dose values at up to 24 points of interest (POI) within the solid water, lung, and bone slabs, as well as mean doses to several regions of interest (ROI), were re‐calculated over a two‐year period which included two software upgrades. The variations in POI and ROI dose values were analyzed and evaluated.Results:The computed doses vary slightly month‐over‐month. There are noticeable variations at the times of software upgrade, if the upgrade involves remodeling and/or re‐commissioning of the beams. The variations are larger in certain points within the phantom, usually in the buildup region or near interfaces, and are almost non‐existent for electron beams.Conclusion:Routine TPS QA is recommended by AAPM and other professional societies, and is often required by accreditation organizations. The frequency and type of QA, though, is subject to debate. The results presented here demonstrate that the frequency of these tests could be at longer intervals than monthly. However, it is essential to perform TPS QA at the time of commissioning and after each software upgrade.

Recommendations for quality control in curietherapy

Brachytherapy consists of sealed radioactive source implantation. The diversity in the nature of radioelements, in their energy and activity requires strict implantation and utilization rules. These rules include radioactive source physical parameters check, after-loading machine and treatment planning system quality assurance and safe and reproducible dosimetric systems. Patient and medical workers information guarantee radioprotection and prevention of accidental exposures.