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. 2024 Sep 1;25(9):3283-3291.
doi: 10.31557/APJCP.2024.25.9.3283.

Impact of Reference Selection on Gamma Analysis in Patient-Specific Quality Assurance for Monte Carlo-Based Treatment Planning Systems

Arun Krishnan M P  1   2 , Ummal Momeen M  1
Affiliations

Impact of Reference Selection on Gamma Analysis in Patient-Specific Quality Assurance for Monte Carlo-Based Treatment Planning Systems

Arun Krishnan M P et al. Asian Pac J Cancer Prev. .

Abstract

Objective: Our study aimed to establish a standardized methodology for selecting "reference" and "evaluated" distributions in gamma analysis for Monte Carlo (MC) based intensity modulated treatment plans. Evaluation of importance of reference selection in MC based and non MC based treatment planning systems were analysed using a study classification.

Methods: Three categories were utilized to analyzed gamma passing rates across using different treatment planning systems (TPS) and detectors for thirty five patients. Category 1 utilized MC-based Monaco TPS plans and a 2 dimensional(2D) I'mRTMatriXX detector. Category 2 employed non-MC-based Eclipse TPS plans, assessed with a 2D I'mRTMatriXX detector. In Category 3, MC-based Monaco TPS plans were validated using a Dolphin detector. All plans were subjected to analysis using gamma criteria, which considered a dose difference of 3% and a distance to agreement of 3mm. Additionally, another set of gamma criteria was employed, with a dose difference of 3% and a distance to agreement of 2mm. An introduced Asymmetric factors in both 2D and 3D analysis will quantify the asymmetric nature of gamma based on the choice of "reference" distribution.

Result: For 2D Gamma analysis, MC-based Monaco TPS and I'mRTMatriXX showed a consistent positive Zk2D trend for all patients, with significant p-values below 0.01 for both gamma passing criteria. In contrast, non-MC based Eclipse TPS exhibited varied Zk2D results, with non-significant p-values. In 3D Gamma analysis, all patients exhibited positive Zk3D values with significant p-values below 0.01 when "references" were swapped. The Pearson correlation between asymmetricity and isodose volumes was notably high at 0.99 for both gamma criteria.

Conclusion: Our study highlights the imperative of using MC-based TPS as the definitive "reference" in gamma analysis for patient specific quality assurance of intensity modulated radiation therapy, emphasizing that variations can mislead results, especially given gamma analysis's sensitivity to MC calculation noise.

Keywords: Asymmetric factor; Gamma; Intensity modulated radiation therapy; Monte Carlo; Patient Specific QA.

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Conflict of interest statement

Authors declare that they have no conflict of interest.

Figures

Figure 1
Figure 1
Measurement Setup with I’mRT MatrixXX with 5 cm of Buildup and Back Scatter. The lateral laser beams are lined up along the lateral grooves on I’mRT MatrixXX.
Figure 2
Figure 2
Dolphin Detector Array Attached to the Gantry Head of Versa-HD for 3D Gamma Analysis.
Figure 3
Figure 3
Flow Chart of Demonstrating the Stratification of the Study Primarily in to Three Categories.
Figure 4
Figure 4
Qualitative Variation of Average Asymmetric Factor in 3D with Response to Changes in the Gamma Search Volume.
Figure 5
Figure 5
Boxplots Show Spread of 2D and 3D Asymmetry Factors for 3% 3mm and 3% 2mm Gamma Criteria
See this image and copyright information in PMC

References

    1. Nutting CM, Morden JP, Harrington KJ, Urbano TG, Bhide SA, Clark C, et al. Parotid-sparing intensity modulated versus conventional radiotherapy in head and neck cancer (parsport): A phase 3 multicentre randomised controlled trial. Lancet Oncol. 2011;12(2):127–36. - PMC - PubMed
    1. Du T, Xiao J, Qiu Z, Wu K. The effectiveness of intensity-modulated radiation therapy versus 2d-rt for the treatment of nasopharyngeal carcinoma: A systematic review and meta-analysis. PLoS One. 2019;14(7):e0219611. - PMC - PubMed
    1. Byrne M, Archibald-Heeren B, Hu Y, Fong A, Chong L, Teh A. Comparison of semiautomated tangential vmat with 3dcrt for breast or chest wall and regional nodes. J Appl Clin Med Phys. 2018;19(5):684–93. - PMC - PubMed
    1. Moningi S, Ajani JA, Badgwell BD, Murphy MB, Ikoma N, Mansfield PF, et al. Imrt reduces acute toxicity in patients treated with preoperative chemoradiation for gastric cancer. Adv Radiat Oncol. 2020;5(3):369–76. - PMC - PubMed
    1. Ismael Dk, Hassan Ff. 3d-conformal radiation therapy and intensity-modulated radiation therapy techniques for laryngeal cancer taking parotid glands as organ at risk. Hospital practices and research. 2020;5(1):10–6.

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