OBJECTIVE To develop an instrument for quantifying innovation and assess the diffusion of innovation in radiation oncology (RO) in the United States. METHODS Primary data were collected for using total population convenience sampling. Innovation Score and Innovation Utilization Score were determined using 20 indicators. 240 medical physicists (MPs) practicing in RO in the United States completed a custom Internet-based survey. RESULTS Centers with no academic affiliation are trailing behind in innovation in total (MD = 1.65, 95% C I[0.38,2.917], p = 0.011, d = 0.351), in patient treatment (MD = 0.39, 95% CI [0.021,0.76], p = 0.038, d = 0.282), and workflow innovation (MD = 7.09, 95% CI [0.78,13.39], p = 0.028, d = 0.330). Centers with no academic affiliation are trailing behind in innovation utilization in total (MD = 0.46, 95% CI [0.05,0.86], p = 0.028, d = 0.188). Rural center are trailing behind in patient positioning in innovation (MD = 0.31, 95% CI [0.011,0.612], p = 0.042, d = 0.293) and innovation utilization (MD = 16.22, 95% CI [0.73,31.72], p = 0.04, d = 0.608). Rural centers are trailing behind in innovative treatments (MD = 0.62, 95% CI [0.23,1.00], p = 0.002, d = 0.457). Motivation (rs = 0.224, p = 0.002) and appreciation (rs = 0.215, p = 0.003) were statistically significant personal factors influencing innovation utilization. CONCLUSIONS There is a wide range of innovation across RO centers in the United States. RO centers in the United States are not practicing as innovative as reasonably achievable. CONCLUSIONS This work quantified how innovative RO in the United States is and results provide guidance on how to improve it in the future.