Comparison of Calcification Specificity in Digital Mammography Using Soft-Copy Display Versus Screen-Film Mammography

Analysis of computer-aided detection techniques and signal characteristics for clustered microcalcifications on digital mammography and digital breast tomosynthesis

With IRB approval, digital breast tomosynthesis (DBT) images of human subjects were collected using a GE GEN2 DBT prototype system. Corresponding digital mammograms (DMs) of the same subjects were collected retrospectively from patient files. The data set contained a total of 237 views of DBT and equal number of DM views from 120 human subjects, each included 163 views with microcalcification clusters (MCs) and 74 views without MCs. The data set was separated into training and independent test sets. The pre-processing, object prescreening and segmentation, false positive reduction and clustering strategies for MC detection by three computer-aided detection (CADe) systems designed for DM, DBT, and a planar projection image generated from DBT were analyzed. Receiver operating characteristic (ROC) curves based on features extracted from microcalcifications and free-response ROC (FROC) curves based on scores from MCs were used to quantify the performance of the systems. Jackknife FROC (JAFROC) and non-parametric analysis methods were used to determine the statistical difference between the FROC curves. The difference between the CAD_DM and CAD_DBT systems when the false positive rate was estimated from cases without MCs did not reach statistical significance. The study indicates that the large search space in DBT may not be a limiting factor for CADe to achieve similar performance as that observed in DM.

[Explorations of breast microcalcifications: Guidelines]

OBJECTIVES

To assess imaging performances for the detection, characterization and biopsy of breast microcalcifications and make recommendations.

MATERIALS AND METHODS

French and English publications were searched using PubMed, Cochrane Library and international learned societies recommendations.

RESULTS

Digital mammography (DR [Direct Radiography] and CR [Computed Radiography]) and screen-film mammography demonstrate good performances for the detection and the characterization of breast microcalcifications. Systematic use of the 2013 edition of the BI-RADS lexicon is recommended for description and characterization of microcalcifications. Faced with BI-RADS 4 or 5 microcalcifications, breast ultrasound is recommended but a normal result does not eliminate the diagnosis of cancer and other examination should be performed. Literature review does not allow recommending digital breast tomosynthesis, elastography or MRI to analyze microcalcifications. In case of probably benign microcalcifications (BI-RADS 3), six months, one year and at least two years follow-up are recommended. In case a biopsy is indicated, it is recommended to use a vacuum-assisted macrobiopsy system with 11-gauges needles or bigger. If no calcification is visible on the radiography of the specimen, it is recommended to obtain additional samples.

Detection of microcalcifications on digital screening mammograms using varying degrees of monitor zooming

OBJECTIVE

The American College of Radiology recommends that mammogram images be viewed at 100% resolution (also called one-to-one or full resolution). We tested the effect of this and three other levels of zooming on the ability of radiologists to identify malignant calcifications on screening mammographic views.

MATERIALS AND METHODS

Seven breast imagers viewed 77 mammographic images, 32 with and 45 without malignant microcalcifications, using four different degrees of monitor zooming. The readers indicated whether they thought a cluster of potentially malignant calcifications was present and where the cluster was located. Tested degrees of zooming included fit screen, a size midway between fit screen and 100%, 100%, and a size slightly larger than 100%.

RESULTS

Readers failed to detect 17 clusters of malignant calcifications with fit-screen images, 12 clusters with midway images, 13 clusters with 100% images, and 11 clusters with slightly larger images. When viewing images without malignant microcalcifications, the readers marked false-positive areas on 25 images using fit-screen images, 43 of the midway images, 40 of the 100% images, and 29 of the slightly larger images.

CONCLUSION

All four tested levels of zooming functioned well. There was a trend for the fit-screen images to function slightly less well than the others with regard to sensitivity, so it may not be prudent to rely on those images without other levels of zooming. The 100% resolution images did not function noticeably better than the others.

Digital mammography in a screening programme and its implications for pathology: a comparative study

Aims

Most studies comparing full-field digital mammography (FFDM) with conventional screen-film mammography (SFM) have been radiology-based. The pathological implications of FFDM have received little attention in the literature, especially in the context of screening programmes. The primary objective of this retrospective study is to compare FFDM with SFM in a population-based screening programme with regard to a number of pathological parameters.

Methods

During the study period, 107 818 women underwent screening mammograms with almost equal numbers obtained with each technique (49.9% with SFM vs 50.1% with FFDM). We compared SFM with FFDM using the following parameters: recall rate, diagnostic core biopsy rate, cancer detection rates, B3 rate, B4 rate, preoperative diagnostic rate for malignancy, positive predictive values and tumour characteristics.

Results

The recall rate was significantly higher with FFDM (4.21% vs 3.52%, p<0.0001). The overall cancer detection rate of 7.2 per 1000 women screened with FFDM was also significantly higher than the rate of 6.2 per 1000 women screened with SFM (p=0.04). The B3 rate in the SFM group was 1.3 per 1000 women screened versus 2.5 per 1000 women screened in the FFDM group (p<0.001). The recall rate and cancer detection rates (overall, invasive and pure ductal carcinoma in situ) were all significantly higher with FFDM for lesions presenting as microcalcifications.

Conclusions

The higher cancer detection rate with FFDM in this study was due to improved detection of microcalcifications. However, this was achieved at the cost of a higher recall rate and a higher B3 rate, indicating that overtreatment may be problematic with digital mammography.

Conspicuity of microcalcifications on digital screening mammograms using varying degrees of monitor zooming

RATIONALE AND OBJECTIVES

American College of Radiology guidelines suggest that digital screening mammographic images should be viewed at the full resolution at which they were acquired. This slows interpretation speed. The aim of this study was to examine the effect of various levels of zooming on the detection and conspicuity of microcalcifications.

MATERIALS AND METHODS

Six radiologists viewed 40 mammographic images five times in different random orders using five different levels of zooming: full resolution (100%) and 30%, 61%, 88%, and 126% of that size. Thirty-three images contained microcalcifications varying in subtlety, all associated with breast cancer. The clusters were circled. Seven images contained no malignant calcifications but also had randomly placed circles. The radiologists graded the presence or absence and visual conspicuity of any calcifications compared to calcifications in a reference image. They also counted the microcalcifications.

RESULTS

The radiologists saw the microcalcifications in 94% of the images at 30% size and in either 99% or 100% of the other tested levels of zooming. Conspicuity ratings were worst for the 30% size and fairly similar for the others. Using the 30% size, two radiologists failed to see the microcalcifications on either the craniocaudal or mediolateral oblique view taken from one patient. Interobserver agreement regarding the number of calcifications was lowest for the 30% images and second lowest for the 100% images.

CONCLUSIONS

Images at 30% size should not be relied on alone for systematic scanning for microcalcifications. The other four levels of magnification all performed well enough to warrant further testing.

Sonographic elastography combined with conventional sonography: how much is it helpful for diagnostic performance?

OBJECTIVE

The purpose of this study was to evaluate the diagnostic performance of conventional sonography combined with sonographic elastography for differentiation between benign and malignant breast lesions and to assess the diagnostic performance with two types of interpretation criteria for sonographic elastography.

METHODS

For this study, we included 281 lesions from 267 patients that were diagnosed as benign or malignant by sonographically guided biopsy and prospectively analyzed by conventional sonography and sonographic elastography from October to December 2007. The histopathologic results from sonographically guided biopsy were used as a reference standard. The final assessments were made prospectively on the basis of conventional sonography alone and then by sonographic elastography combined with conventional sonography. The diagnostic performance using area under the receiver operating characteristic (ROC) curve analysis (A(z)) was compared on the basis of conventional sonography alone and on elastography combined with conventional sonography. We also calculated the area ratio of lesions detected by elastography and the elasticity score reported by Itoh et al (Radiology 2006; 239:341-350).

RESULTS

The areas under the ROC curve for conventional sonography and the combination of conventional sonography and sonographic elastography were 0.927 and 0.876, respectively. The area ratio of the lesion had better diagnostic performance (A(z), 0.757) than the elasticity score (A(z), 0.54; P < .05).

CONCLUSIONS

The diagnostic performance of radiologists with respect to the characterization of breast masses as benign or malignant was not significantly improved with sonographic elastography. The area ratio of the lesion had a better diagnostic value in elastography than the elasticity score.

Observer study for evaluating potential utility of a super-high-resolution LCD in the detection of clustered microcalcifications on digital mammograms

We evaluated the potential utility of a newly developed liquid-crystal display (LCD), which used an independent sub-pixel drive (ISD) technique for increasing the spatial resolution of a standard LCD three times in one direction, by use of receiver operating characteristic (ROC) analysis and a two-alternative-forced-choice (2AFC) method to determine improvement in radiologists' accuracy in the detection of clustered microcalcifications (MCLs) on digital mammograms. We used a standard LCD without and with the ISD technique, which can increase the spatial resolution of the LCD three times in one direction from three mega- to nine megapixels without changes in the size of the display. We used 60 single views of digital mammograms (30 with and 30 without clustered MCLs) for ROC studies and 60 regions of interest (ROIs) with clustered MCLs for 2AFC studies. In the ROC study, seven radiologists attempted to detect clustered MCLs without and with the ISD on the same LCD. In the 2AFC study, the same observer group compared the visibility of MCLs by use of the LCD without and with the ISD. Our institutional review board approved the use of this database and the participation of radiologists in this study. The accuracy in detecting clustered MCLs in the ROC study was improved by use of the LCD with the ISD, but the improvement was not statistically significant (p = 0.08). However, the superiority of the LCD with the ISD was demonstrated as significant (p < 0.001) in the 2AFC study. An LCD with ISD can improve the visibility of clustered MCLs when high-resolution digital mammograms are available.

Observer variability in screen-film mammography versus full-field digital mammography with soft-copy reading

Full-field digital mammography (FFDM) with soft-copy reading is more complex than screen-film mammography (SFM) with hard-copy reading. The aim of this study was to compare inter- and intraobserver variability in SFM versus FFDM of paired mammograms from a breast cancer screening program. Six radiologists interpreted mammograms of 232 cases obtained with both techniques, including 46 cancers, 88 benign lesions, and 98 normals. Image interpretation included BI-RADS categories. A case consisted of standard two-view mammograms of one breast. Images were scored in two sessions separated by 5 weeks. Observer variability was substantial for SFM as well as for FFDM, but overall there was no significant difference between the observer variability at SFM and FFDM. Mean kappa values were lower, indicating less agreement, for microcalcifications compared with masses. The lower observer agreement for microcalcifications, and especially the low intraobserver concordance between the two imaging techniques for three readers, was noticeable. The level of observer agreement might be an indicator of radiologist performance and could confound studies designed to separate diagnostic differences between the two imaging techniques. The results of our study confirm the need for proper training for radiologists starting FFDM with soft-copy reading in breast cancer screening.

Digital mammography: what do we and what don't we know?

High-quality full-field digital mammography has been available now for several years and is increasingly used for both diagnostic and screening mammography. A number of different detector technologies exist, which all have their specific advantages and disadvantages. Diagnostic accuracy of digital mammography has been shown to be at least equivalent to film-screen mammography in a general screening population. Digital mammography is superior to screen-film mammography in younger women with dense breasts due to its ability to selectively optimize contrast in areas of dense parenchyma. This advantage is especially important in women with a genetic predisposition for breast cancer, where intensified early detection programs may have to start from 25 to 30 years of age. Tailored image processing and computer-aided diagnosis hold the potential to further improve the early detection of breast cancer. However, at present no consensus exists among radiologists on which processing is optimal for digital mammograms. Image processing may also vary significantly among vendors with so far limited interoperability. This review aims to summarize the available information regarding the impact of digital mammography on workflow and breast cancer diagnosis.