Objective To observe the value of Zero-Shot Noise2Noise(ZS-N2N)based on Z-axis correlation for reducing noise of low dose CT(LDCT)images.Methods CT data of the cancer imaging archive were enrolled,including normal dose CT(NDCT)images and LDCT images,with 3 sets of chest and 3 sets of abdominal images.Noise on LDCT images were reduced with ZS-N2N method based on Z-axis correlation,and the peak signal-to-noise ratio(PSNR),structural similarity(SSIM)and time-consuming of reducing noise were compared with those of Self2Self,simple ZS-N2N and traditional Block-matching and 3D filtering(BM3D).Results After reducing noise,noise on Self2Self denoised images remained significant,the structure edges on BM3D denoised images were blurry with some details lost,while simple ZS-N2N and ZS-N2N based on Z-axis correlation denoised images preserved more details and had better quality.PSNR and SSIM of Self2Self denoised images were poor and the time-consuming were longer.PSNR,SSIM and time-consuming of the other 3 methods were similar,among which PSNR of ZS-N2N based on Z-axis correlation were slightly higher than BM3D and simple ZS-N2N,but the time-consuming were also slightly longer.Conclusion ZS-N2N based on Z-axis correlation had high value for reducing noise of LDCT images.

Objective:To explore the feasibility of the clinical implementation of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans with 6MV photon on two Elekta Linacs (Versa HD and Synergy) after beam matching.Methods:The images of 12 patients with nasopharyngeal carcinoma, central lung cancer and prostate cancer were randomly selected, and the IMRT and VMAT plans were designed. Two different dose tools of ionization chamber and three-dimensional detector ArcCheck were used to verify the individualized radiation treatment of 6MV photon beams on two Linacs and compare the differences.Results:The deviations between the doses of two Linacs (Versa HD and Synergy) measured by the ion chamber and treatment planning system were (0.32±1.32)% and (0.54±1.29)%. The differences of all plans were within the range of ±3%, and the deviations of the point dose between two Linacs were within the range of ±2% with no statistical significance (both P>0.05). The γ analysis of verification using ArcCheck showed that the passing rates of all plans under the 2mm/3% and 3mm/3% with 10% threshold conditions were over 95%, respectively. The average differences between two Linacs were 0.19%(2mm/3%) and 0.09%(3mm/3%). Conclusions:The results of performing IMRT/VMAT plans on two Linacs meet the clinical requirements and the differences between two Linacs are small. Hence, the same plans can be implemented interchangeably on different Linacs.