Evaluation of breast amorphous calcifications by a computer-aided detection system in full-field digital mammography

Objectives

The purpose of this study was to evaluate the performance of a direct computer-aided detection (d-CAD) system integrated with full-field digital mammography (FFDM) in assessment of amorphous calcifications.

Methods

From 1438 consecutive stereotactic-guided biopsies, FFDM images with amorphous calcifications were selected for retrospective evaluation by d-CAD in 122 females (mean age, 56 years; range, 35–84 years). The sensitivity, specificity, accuracy and false-positive rate of the d-CAD system were calculated in the total group of 124 lesions and in the subgroups based on breast density, mammographic lesion distribution and extension. Logistic regression analysis was used to stratify the risk of malignancy by patient risk factors and age.

Results

The d-CAD marked all (36/36) breast cancers, 85% (11/13) of the high-risk lesions and 80% (60/75) of benign amorphous calcifications (p<0.01) correctly. The sensitivity, specificity and diagnostic accuracy for the combined malignant and “high-risk” lesions was 96, 80 and 86%, respectively. The likelihood of malignancy was 29%. There was no significant difference between the marking of fatty or dense breasts (p>0.05); however, d-CAD marks showed differences for small (<7 mm) lesions (p=0.02) and clustered calcifications (p=0.03). The false-positive rate of d-CAD was 1.76 marks per full examination.

Conclusion

The d-CAD system correctly marked all biopsy-proven breast cancers and a large number of biopsy-proven high-risk lesions that presented as amorphous calcifications. Given our 29% likelihood of malignancy, imaging-guided biopsy appears to be a reasonable recommendation in cases of amorphous calcifications marked by d-CAD.Many cancers that cannot be detected with mammography are in dense tissue, and digital mammography is more accurate in females with radiographically dense breasts 1]. In order for a radiologist to diagnose a breast cancer, this cancer must first be detected and second be correctly interpreted. Computer-aided detection (CAD) systems help radiologists with the perception of the cancer, marking regions of interest on the screen. The use of CAD software primarily in full-field digital mammography (FFDM), also known as direct CAD (d-CAD), does not require digitisation of the films and by definition, once an image is acquired, the CAD detection result will be reproducible when the same d-CAD scheme is applied repeatedly to such an image 2].Breast microcalcifications are detected by high-quality mammography 3-8]. Amorphous calcifications are frequently difficult to identify on routine mammograms, with 78% seen retrospectively but not prospectively by Berg et al 9] in their series using screen-film mammograms. The purpose of CAD systems in breast imaging is to help the radiologist by marking suspicious regions that were initially missed; however, the radiologist has to decide whether true areas of concern are present in the highlighted locations and thus retains the ability to make the final decision about whether biopsy is deemed necessary.Because amorphous calcifications without associated findings can be easily overlooked on routine screening mammograms, the use of d-CAD systems to aid in detection could be beneficial to the radiologist. Therefore, the purpose of our study was to determine the performance of one commercially available d-CAD system in marking non-palpable amorphous calcifications not associated with other mammographic findings and comparing this with the histopathology results.