Performance evaluation of digital mammography, digital breast tomosynthesis and ultrasound in the detection of breast cancer using pathology as gold standard: an institutional experience

Background Mammography is the primary imaging modality for diagnosing breast cancer in women more than 40 years of age. Digital breast tomosynthesis (DBT), when supplemented with digital mammography (DM), is useful for increasing the sensitivity and improving BIRADS characterization by removing the overlapping effect. Ultrasonography (US), when combined with the above combination, further increases the sensitivity and diagnostic confidence. Since most of the research regarding tomosynthesis has been in screening settings, we wanted to quantify its role in diagnostic mammography. The purpose of this study was to assess the performance of DM alone vs. DM combined with DBT vs. DM plus DBT and ultrasound in diagnosing malignant breast neoplasms with the gold standard being histopathology or cytology. Results A prospective study of 1228 breasts undergoing diagnostic or screening mammograms was undertaken at our institute. Patients underwent 2 views DM, single view DBT and US. BIRADS category was updated after each step. Final categorization was made with all three modalities combined and pathological correlation was done for those cases in which suspicious findings were detected, i.e. 256 cases. Diagnosis based on pathology was done for 256 cases out of which 193 (75.4%) were malignant and the rest 63 (24.6%) were benign. The diagnostic accuracy of DM alone was 81.1%. Sensitivity, Specificity, PPV and NPV were 87.8%, 60%, 81.3% and 61.1%, respectively. With DM + DBT the diagnostic accuracy was 84.8%. Sensitivity, Specificity, PPV and NPV were 92%, 56.5%, 89% and 65%, respectively. The diagnostic accuracy of DM + DBT + US was found to be 85.1% and Sensitivity, Specificity, PPV and NPV were 96.3%, 50.7%, 85.7% and 82%, respectively. Conclusion The combination of DBT to DM led to higher diagnostic accuracy, sensitivity and PPV. The addition of US to DM and DBT further increased the sensitivity and diagnostic accuracy and significantly increased the NPV even in diagnostic mammograms and should be introduced in routine practice for characterizing breast neoplasms.

Comparison of Mean Glandular Dose between Full-Field Digital Mammography and Digital Breast Tomosynthesis

Early detection of breast cancer is diagnosed using mammography, the gold standard in breast screening. However, its increased use also provokes radiation-induced breast malignancy. Thus, monitoring and regulating the mean glandular dose (MGD) is essential. The purpose of this study was to determine MGD for full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) in the radiology department of a single centre. We also analysed the exposure factors as a function of breast thickness. A total of 436 patients underwent both FFDM and DBT. MGD was auto calculated by the mammographic machine for each projection. Patients’ data included compressed breast thickness (CBT), peak kilovoltage (kVp), milliampere-seconds (mAs) and MGD (mGy). Result analysis showed that there is a significant difference in MGD between the two systems, namely FFDM and DBT. However, the MGD values in our centre were comparable to other centres, as well as the European guideline (<2.5 mGy) for a standard breast. Although DBT improves the clinical outcome and quality of diagnosis, the risk of radiation-induced carcinogenesis should not be neglected. Regular quality control testing on mammography equipment must be performed for dose monitoring in women following a screening mammography in the future.

Diagnostic reference levels in digital mammography: A systematic review

Diagnostic reference levels (DRLs) in digital mammography (DM) serve as a useful benchmark for dose monitoring and optimization, allowing comparison amongst countries, institutions and mammography units. A systematic review of DRLs in DM, published in 2014, reported a lack of consistent and internationally accepted protocol in DRLs establishment, thereby resulting in wide variations in methodologies which complicates comparability between studies. In 2017, the International Commission of Radiation Protection (ICRP) published additional guidelines and recommendations to provide clarity in the protocol used in DRLs establishment. With the continuing evolvement of technology, optimization of examinations and updates in guidelines and recommendations, DRLs should be revised at regular intervals. This systematic review aims to provide an update and identify a more consistent protocol in the methodologies used to establish DRLs. Searches were conducted through Web of Science, PubMed-MEDLINE, ScienceDirect, CINAHL and Google Scholar, which resulted in 766 articles, of which 19 articles were included after screening. Relevant data from the included studies were summarized and analyzed. While the additional guidelines and recommendations have provided clarifications in the methodologies used in DRLs establishment, such as data source (i.e., the preference to use data derived from patient instead of phantoms to establish DRLs), protocol (i.e., stratification of DRLs by compressed breast thickness and detector technology, and the use of median value for DRLs quantity instead of mean) and percentiles used to establish DRLs (i.e., set at the 75th percentile with a minimum sample size of 50 patients), other differences such as the lack of a standard dose calculation method used to estimate mean glandular dose continues to complicate comparisons between studies and different DM systems. This systematic review update incorporated the updated guidelines and recommendations from ICRP which will serve as a useful resource for future research efforts related to DRLs, dose monitoring and optimization.

Cancer Conspicuity on Low-energy Images of Contrast-enhanced Mammography Compared With 2D Mammography

Objective Low-energy (LE) images of contrast-enhanced mammography (CEM) have been shown to be noninferior to digital mammography. However, our experience is that LE images are superior to 2D mammography. Our purpose was to compare cancer appearance on LE to 2D images. Methods In this IRB-approved retrospective study, seven breast radiologists evaluated 40 biopsy-proven cancer cases on craniocaudal (CC) and mediolateral oblique (MLO) LE images and recent 2D images for cancer visibility, confidence in margins, and conspicuity of findings using a Likert scale. Objective measurements were performed using contrast-to-noise ratio (CNR) estimated from regions of interest placed on tumor and background parenchyma. Reader agreement was evaluated using Fleiss kappa. Per-reader comparisons were performed using Wilcoxon test and overall comparisons used three-way analysis of variance. Results Low-energy images showed improved performance for visibility (CC LE 4.0 vs 2D 3.5, P &lt; 0.001 and MLO LE 3.7 vs 2D 3.5, P = 0.01), confidence in margins (CC LE 3.2 vs 2D 2.8, P &lt; 0.001 and MLO LE 3.1 vs 2D 2.9, P &lt; 0.008), and conspicuity compared to tissue density compared to 2D mammography (CC LE 3.6 vs 2D 3.2, P &lt; 0.001 and MLO LE 3.5 vs 2D 3.2, P &lt; 0.001). The average CNR was significantly higher for LE than for digital mammography (CC 2.1 vs 3.2, P &lt; 0.001 and MLO 2.1 vs 3.4, P &lt; 0.001). Conclusion Our results suggest that cancers may be better visualized on the LE CEM images compared with the 2D digital mammogram.

At Which Mean Glandular Dose Does the Benefit of Breast Cancer Deaths Averted Equal the Risk of Lives Lost to Screening From Radiation-induced Malignancy for Mammography With and Without Tomosynthesis?

Objective To estimate benefit-to-radiation-risk mean glandular dose (MGD) equivalence values for screening mammography, defined as the yearly MGD (over a 10-year period) at which the estimated benefit of mammography in terms of deaths averted equals the estimated risk of lives lost to screening due to radiation exposure (a benefit-to-risk ratio of 1). Methods Benefit-to-risk ratios were calculated as the ratio of breast cancer deaths averted and lives lost to screening over 10-year intervals starting at age 40 for mammography and tomosynthesis using previously published methodology. The MGD values at which estimated benefit equals risk were tabulated. Results The MGD values at which benefit-to-risk equivalence points were met for digital screening mammography are 63 milligray (mGy) (ages 40–49), 88 mGy (ages 50–59), 176 mGy (ages 60–69), and 336 mGy (ages 70–79). The MGD values that met benefit-to-risk equivalence for screening tomosynthesis plus digital mammography or synthetic mammography are 80 mGy (ages 40–49), 111 mGy (ages 50–59), 224 mGy (ages 60–69), and 427 mGy (ages 70–79). Conclusion Cutoff MGD values at which the estimated benefit from screening equals the estimated risk are well above standard screening MGD exposures. Care is necessary to ensure that threshold values are not exceeded during a screening exam, particularly for women ages 40–49 years old when using digital mammography plus tomosynthesis (due to an approximate doubling of dose per exam that will more readily exceed cutoff MGD values) and when many additional views are obtained.