The article "Mapping the Literature of Radiation Therapy" in the April 2013 issue of the Journal of the Medical Library Association, analyzes the sources of the most frequently cited articles relating to radiation therapy [Table 6, online only]. From a total of 908 citations, a third of them came from just eleven journals (listed in Zone 1: #1-11).
Delwiche, F. A. (2013). Mapping the literature of radiation therapy. Journal of the Medical Library Association : JMLA, 101(2), 120–127. http://doi.org/10.3163/1536-5050.101.2.007