Background: The dose distribution of the Flatting-Filter-Free (FFF) of medical linear accelerator (LINACS) has been proved to have its advantages in clinical use. With the recent development of three-dimensional conformal radiotherapy and intensity-modulated radiation therapy

field of clinical treatment is mainly achieved by using Multi-leaf Collimator (MLC). Because of the rare researches on dosimetry characteristics of MLC field under FFF beam

it is interesting to note the importance of its further development. Purpose: For the TureBeam accelerator of 6 MV-X

the dose characteristics of the MLC are studied in the presence of the FFF beam. Methods: The off-axis dose curve characteristics are analyzed by using the Monte Carlo (MC) method

combined with three-dimensional dose scanning data. Results: The compared results

including MLC leaf position accuracy

leakage radiations along X-axis and Y-axis

field penumbra and the influence of the concave-convex structure of the leaf

show that the MC simulations result in good agreement with the clinical data. MLC irregular radiation field’s geometry

MC calculation and clinical measurement discrepancy degree are 3.6290%

3.2626% and 2.0394%

respectively. A circle field of radius 5 cm and uneven borders field geometry and MC calculation discrepancy degree are 0.8662%

0.8794% and 0.2314%

0.8170%

respectively. Conclusion: The results provide a reliable basis for the clinical use of MLC. Abstract