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The definition of meningioma growth adopted in this study was absolute growth rate ≥2 cm3/year OR absolute growth rate ≥1 cm3/year AND relative growth rate ≥30%/year. The decision to use this definition was based on a joint longitudinal and time-to-event model and subsequent classification and regression tree analysis. The online tool provided in this page is to help determine whether the incidental meningioma being assessed has met a meningioma growth endpoint as defined above. 


By using the calculator or the website, you accept this disclaimer. If you do not accept this disclaimer, do not use the calculator or the website.

This calculator is distributed under the terms of the Creative Commons Attribution-Non-Commercial 3.0 International License (CC BY-NC 3.0) (, which permits the user to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Data should only be used for non-commercial research purposes by research professionals.

IMPACT provides individualised active monitoring strategies for incidentally-found asymptomatic meningioma based on radiological and clinical parameters. It has not been externally validated. Implementation of the results in a clinical setting is in the sole responsibility of the user and/or treating physician.

By using the calculator, you agree not to hold the authors, any of their affiliated institutions, or any of their respective directors, officers, employees, agents, suppliers or partners liable in any way for the use of the calculator or use of the data obtained by using the calculator. You agree to indemnify and hold the aforementioned parties harmless from and against any and all damages, losses, liabilities, costs and expenses incurred by any of them arising out of or related to your use of the calculator.

The calculator and the information provided are not intended or implied to be a substitute for medical advice offered by a healthcare professional. If you require such services or advice regarding the calculator or the information and results generated by the calculator, you should consult a healthcare professional.

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