Objective To verify and adjust the leaf position accuracy of a multi-leaf collimator (MLC) in a linear accelerator.Methods Ionization chamber arrays ( StarTrack, IBA) were used to measure the leaf position accuracy of a MLC in a linear accelerator (Precise, ELEKTA) and adjust the leaves out of tolerance.Results After the adjustment of leaf position of the MLC, the analysis of the verification films taken at the offset position showed that the leaf position of the MLC was accurate.Conclusions The method developed in this study is convenient and simple for measurement and calibration of leaf position of the MLC in the linear accelerator, which meets the MLC position accuracy requirement for the linear accelerator.

Objective To discuss the application of digital simulation positioning machine in radiation oncology. Methods We used digital simulation positioning machine to shoot isocenter reset digital simulator images of 0 degrees direction and 90 degrees direction, 10 × 10 cm2 rectangular field and actual time radiation field with any field number. Compared the images taken with the TPS corresponding DRR image through bone marker matching to measure the error of isocenter and actual time radiation field , the linear accelerator Iview-GT system with the same method was shot in rectangular field simulator the same field number EPID image , and the TPS corresponding DRR image. Finally, we compared the measured error of the digital simulator positioning machine with the error of Iview-GT system image. Results The result of measured isocenter error of the digital simulator positioning machine was better than EPID image error (P=0.000). Conclusion The application of digital simulation positioning machine in radiation oncology can be more accurate to measure the error and correct the position deviation, however, it can also make the radiotherapy and the treatment more accurate.