Purpose: Digital mammography is known to have lower spatial resolution compared to conventional analogic mammography. The aim of this study was to evaluate whether this physical feature could compromise the perception of microcalcifications in radiological findings.
Materials and methods: Fifty-two surgical samples of non-palpable breast lesions with microcalcifications were imaged using both techniques. The images were examined by four different radiologists. Data processing was limited to comparing the number of microcalcifications found on the conventional and digital images, in both standard and magnified modality. The cases were classified into 3 groups according to the number of calcifications demonstrated in the surgical sample: less than 10, 10 to 30, and more than 30. The differences in the count of microcalcifications with the two acquisition modalities were evaluated with the Kappa test. In order to compare the differences we synthesised by percentage those cases exhibiting a larger or lesser number of calcifications.
Results: The Kappa test was 0.546 in standard analogic vs standard digital, 0.582 in magnified analogic vs magnified digital, 0.828 in standard analogic vs magnified analogic and 0.492 in standard digital vs magnified digital. The most significant results were observed on comparing the magnifications produced with the two modalities: in 25% of cases, digital magnification detected more calcifications than did traditional magnification. The number of cases where standard digital images allowed the detection of more calcifications than standard analogic images was significant, although less important (17.8%).
Conclusions: The study was able to provide data that confirm the overall equivalence of the two techniques, as far as subtle mammographic findings (such as microcalcifications) are concerned. In particular, as applied to the series we examined, there is a cautious advantage in favour of the digital technique. More clinical studies, on larger series, will be necessary for a further and more thorough comparison of the two techniques, so that the results might be consistently useful in clinical practice.