Texture analysis on fluence maps was performed to evaluate the degree of modulation for volumetric modulated arc therapy (VMAT) plans. A total of 6 textural features including angular second moment (ASM), inverse difference moment (IDM), contrast, variance, correlation and entropy were calculated for fluence maps generated from 20 prostate and 20 head and neck (H&N) VMAT plans. For each of the textural features, particular displacement distances (d) of 1, 5 and 10 were adopted. To investigate the deliverability of each VMAT plan, gamma passing rates of pre-treatment quality assurance (QA),...