Purpose Dynamic tumor tracking with intensity modulated radiation therapy(DTT IMRT)function was newly installed in Vero4DRT in our hospital.The purpose of this study was to perform dosimetric verification for DTT IMRT using a chamber and a Gafchromic film.Material & Method The dosimetric verification system was comprised of a 0.13 cc ionization chamber,Gafchromic EBT3 films,a water-equivalent phantom,and a moving phantom(QUASAR platform phantom).First,the water-equivalent phantom was positioned on the QUASAR platform phantom with the chamber.Subsequently,step-and-shoot IMRT delivery was performed under the conditions as follows:(1)Stationary IMRT,(2)Non-DTT IMRT and(3)DTT IMRT.The phantom was reciprocated along superior-inferior direction by sinusoidal patterns(Amplitude:10-40 mm,Breathing cycle:2-4 s).In the dose distribution verification,the EBT3 films were inserted in the water-equivalent phantom and the IMRT delivery was performed in the same manner.The dosimetric tolerance to the planned dose was set to dose error within ±5%in each port and ±3%in total,and Gamma Pass rate > 90%.Result Absolute dosimetric verification:In Non-DTT IMRT,it was observed that the dose error was greater than the tolerance at several spots having steep dose gradient for complicated plans.On the other hand,the dose error became less than the tolerance in DTT IMRT for all patterns.Dose distribution verification:Gamma pass rate became greater than 94%for all patterns in DTT IMRT,while Gamma pass rate became lower for patterns with larger amplitude in Non-DTT IMRT.Conclusion We have demonstrated that DTT IMRT for the moving target had good agreement with Static IMRT for the stationary target in terms with dosimetry,suggesting that DTT IMRT function in the Vero4DRT system can improve the dosimetric accuracy of IMRT for the moving target.