There are several methods to evaluate objectively the quality of a digital image. For digital mammography, objective quality assessment must be performed without references. In a previous study, the authors investigated the use of a normalized anisotropic quality index (NAQI) to assess mammography images blindly, in terms of noise and spatial resolution. Since the NAQI is used as a quality metric, it must not be highly dependent on the breast anatomy. Thus, in this work, we analyze the NAQI behavior with different breast anatomies. A computerized system was used to synthesize 1,440 anthropomorphic breast phantom images with realistically selected range of anatomical variations. The results show that NAQI achieves a small dependency on breast anatomy when images are acquired without degradation (<12%). However, for realizations that simulate the acquisition process in digital mammography, the NAQI is more sensitive (33%) due to quantum noise. Thus, NAQI can be used in clinical practice to assess mammographic image quality.