Zooming method (× 2.0) of digital mammography vs digital magnification view (× 1.8) in full-field digital mammography for the diagnosis of microcalcifications

The purpose of this study was to determine whether the interpretation of microcalcifications assessed on images zoomed (× 2.0) from digital mammograms is at least equivalent to that from digital magnification mammography (× 1.8) with respect to diagnostic accuracy and image quality. Three radiologists with different levels of experience in mammography reviewed each full-field digital mammography reader set for 185 patients with pathologically proven microcalcification clusters, which consisted of digital magnification mammograms (MAGs) with a magnification factor of 1.8 and images zoomed from mammograms (ZOOM) with a zoom factor of 2.0. Each radiologist rated their suspicion of breast cancer in microcalcific lesions using a six-point scale and the image quality and their confidence in the decisions using a five-point scale. Results were analysed according to display methods using areas under the receiver operating characteristic curves (A_z value) for ZOOM and MAGs to interpret microcalcifications, and the Wilcoxon matched pairs signed rank test for image quality and confidence levels. There was no statistically significant difference in the level of suspicion of breast cancer between the ZOOM and MAG groups (A_z = 0.8680 for ZOOM; A_z = 0.8682 for MAG; p = 0.9897). However, MAG images were significantly better than ZOOM images in terms of visual imaging quality (p < 0.001), and the confidence level with MAG was better than with ZOOM (p < 0.001). In conclusion, the performance of radiologists in the diagnosis of microcalcifications using ZOOM was similar to that using MAGs, although image quality and confidence levels were better using MAGs.Magnification mammography produces better spatial resolution and signal-to-noise ratio than does contact mammography. It is well established as a valuable adjunct to contact mammography, especially for the diagnosis of microcalcifications, despite the additional radiation exposure and increased radiation dose because of the shorter distance between the breast and X-ray source during examination [1–4].However, with respect to full-field digital mammography (FFDM), a few studies using zoomed images from contact mammograms have recently been reported and, as a result, a debate has arisen over whether a digital zooming system of FFDM can replace the magnification view of digital mammography [5–7]. Whereas Fischer et al [5] reported that zoomed images of a digital contact mammogram were equivalent to direct magnification of FFDM for the interpretation of microcalcifications, our previous report suggested that magnification mammography yielded better sensitivity and receiver operating characteristic (ROC) analysis than did zoomed images [7]. However, that study compared images zoomed by a factor of 1.3 with images magnified by a factor of 1.8. Therefore, we wondered whether using a zooming factor comparable to a magnification factor of 1.8 would yield the same results.The purpose of this study was to determine whether the diagnostic accuracy and image quality of microcalcification assessments using images twice zoomed from contact mammograms were equivalent to those obtained using digital magnification mammography by a magnification factor of 1.8.     

Breast cancer detection in digital breast tomosynthesis and digital mammography—a side-by-side review of discrepant cases

Objective:

To analyse discrepant breast cancer detection in digital breast tomosynthesis (DBT) and digital mammography (DM).

Methods:

From a previous detection study comparing DBT and DM, 26 discrepant cases were extracted, 19 detected by DBT only and 7 by DM only. An expert panel of three radiologists reviewed these cases and documented the level of discrepancy, lesion visibility, radiographic pattern and lesion conspicuity and assessed the reason for non-detection. Differences between groups were tested using the Wilcoxon rank sum test, the Kruskal–Wallis test and visual grading characteristics.

Results:

The proportion of lesion periphery in fatty tissue was statistically significantly larger, and there were significantly more spiculated masses in DBT compared with DM in the DBT only group (p = 0.018; p = 0.015). The main reasons for missing a lesion were poor lesion visibility when using DM and interpretative error when using DBT.

Conclusion:

Lesion visualization is superior with DBT, particularly of spiculated tumours. A major reason for non-detection in DBT seems to be interpretative error, which may be due to lack of experience.

Advances in knowledge:

Our findings suggest that DBT is better than DM in visualizing breast cancer and that non-detection when using DBT is related to interpretative error regarding clearly visible lesions.Although digital mammography (DM) is the standard technique for imaging examination of symptomatic females, as well as for screening, it is a well-established fact that the technique has important limitations in terms of breast cancer detection, especially in dense breasts, where the sensitivity has been reported as being as low as 30–60%.^1,2 The main reasons are the obscuring effect of fibroglandular tissue and certain cancer growth patterns, for example, invasive lobular carcinoma (ILC) that sometimes grows diffusely in the breast in a single-file pattern and produces little desmoplastic response.³ In recent years, digital breast tomosynthesis (DBT) has developed into a promising three-dimensional (3D) breast-imaging technique that takes advantage of multiple exposures at different angles, which enables reconstruction of thin slices into a 3D volume and reduces the degrading effect of superimposed tissue.^4,5 Data indicate that DBT is an important adjunct to conventional DM, as well as being a promising screening modality, with about 30% higher cancer detection rate than that of ordinary screening, when read in combination with DM.^5–8In an experimental clinical series in our institution, comparing the accuracy of one-view DBT with that of two-view DM, sensitivities of approximately 90% and approximately 79%, respectively, for cancer detection were found.⁹ In brief, the study included 185 symptomatic or asymptomatic females with subtle or negative findings on DM, but suspicious lesions on ultrasonography, yielding 89 females with 95 cancer lesions and 96 females with normal or benign findings. The females underwent standard assessment and one-view DBT. Five breast radiologists interpreted DBT and DM images independently in accordance with free-response receiver operating characteristic methodology,¹⁰ classifying findings in accordance with the American College of Radiology''s Breast Imaging Reporting and Data System (BI-RADS).¹¹ Cases of discrepant detection in DBT and DM form the basis of the current study.When introducing a new diagnostic method, it is important to evaluate not only its accuracy but also to define its advantages and limitations in terms of imaging characteristics.¹² The aim of this study was to reassess possible reasons for discrepant breast cancer detection in DBT vs DM by analysing detectability parameters and radiographic lesion characteristics, with the DBT and DM images displayed side by side.     

Should previous mammograms be digitised in the transition to digital mammography?

Breast screening specificity is improved if previous mammograms are available, which presents a challenge when converting to digital mammography. Two display options were investigated: mounting previous film mammograms on a multiviewer adjacent to the workstation, or digitising them for soft copy display. Eight qualified screen readers were videotaped undertaking routine screen reading for two 45-min sessions in each scenario. Analysis of gross eye and head movements showed that when digitised, previous mammograms were examined a greater number of times per case (p = 0.03), due to a combination of being used in 19% more cases (p = 0.04) and where used, looked at a greater number of times (28% increase, p = 0.04). Digitising previous mammograms reduced both the average time taken per case by 18% (p = 0.04) and the participants’ perceptions of workload (p < 0.05). Digitising previous analogue mammograms may be advantageous, in particular in increasing their level of use.     

Does digital mammography in a decentralized breast cancer screening program lead to screening performance parameters comparable with film-screen mammography?

Objective:

To evaluate if the screening performance parameters of digital mammography (DM) in a decentralized screening organization were comparable with film-screen mammography (FSM).

Methods:

A nationwide screening program was launched in 2001, and since 2005 screening with DM has been allowed. Firstly, the parameters of the three regional screening units (RSUs) that first switched to DM (11,355 women) were compared with the FSM period of the same three RSUs (23,325 women). Secondly, they were compared with the results of the whole central breast unit (CBU).

Results:

The recall rate (RR) of the DM group in the initial round was 2.64% [2.40% for FSM (p?=?0.43)] and in the subsequent round 1.20% [1.58% for FSM (p?=?0.03)]. The cancer detection rate (CDR) was 0.59% for DM and 0.64% for FSM (p?=?0.56). The percentage of ductal carcinoma in situ was 0.07% for DM and 0.16% for FSM (p?=?0.02). The positive predictive value was high in the subsequent rounds (DM 48.00%, FSM 45.93%) and lower in the initial round (DM 24.05%, FSM 24.86%). Compared with the results of the whole CBU, DM showed no significant difference.

Conclusion:

DM can be introduced in a decentralized screening organization with a high CDR without increasing the RR.     

Indeterminate breast lesions: Can contrast enhanced digital mammography change our decisions?

Objective

To assess the efficiency of dual energy contrast enhanced mammography in the assessment of the indeterminate breast lesions (BIRADS 3 and BIRADS 4).

How good is the ACR accreditation phantom for assessing image quality in digital mammography?

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the American College of Radiology (ACR) accreditation phantom for assessing image quality in digital mammography. MATERIALS AND METHODS: Digital images were obtained of an ACR accreditation phantom at varying mAs (constant kVp) and varying kVp (constant mAs). The average glandular dose for a breast with 50% glandularity was determined for each technique factor. Images were displayed on a 5 mega-pixel monitor, with the window width and level settings individually optimized for viewing the fibers, specks, and masses in the ACR phantom. Digital images of the ACR phantom were presented in a random manner to eight observers, each of whom indicated the number of objects visible in each image. RESULTS: Intraobserver variability was greater than interobserver variability for the detection of fibers and specks, but the reverse was true for the detection of masses. As the mAs increased, the number of fibers visible increased from less than one at 5 mAs to all six being visible at 80 mAs. The corresponding number of visible specks increased from 12 to 24, and the number of visible masses increased from 1.25 to about four. Above 26 kVp, object visibility was constant with increasing x-ray tube voltage. Reducing the x-ray tube voltage to 24 kVp, however, reduced the number of visible fibers from six to five, the number of visible specks from 24 to 21.1, and the number of visible masses from four to 3.1. Observer performance was approximately constant for average glandular doses greater than 1.6 mGy, so that the range of lesion detectability in the ACR phantom occurs at doses lower than those normally encountered in clinical practice. CONCLUSION: The current design of the ACR phantom is unsatisfactory for assessing image quality in digital mammography.     

The potential use of ultra-low radiation dose images in digital mammography—a clinical proof-of-concept study in craniocaudal views

Objective:

To estimate the potential of low-dose images in digital mammography by analysing the effect of substantial dose reduction in craniocaudal (CC) views on clinical performance.

Methods:

At routine mammography, additional CC views were obtained with about 10% of the standard dose. Five radiologists retrospectively read the standard [mediolateral oblique (MLO) + CC] and combination low-dose mammograms (standard MLO + low-dose CC). If present, lesion type, conspicuity and suggested work-up were recorded. Final diagnoses were made by histology or follow up. A t-test or χ² test was used to compare results.

Results:

421 cases were included, presenting 5 malignancies, 66 benign lesions and multiple non-specific radiologic features. Using MLO with low-dose CC, all lesions were detected by at least one reader, but altogether less often than with standard mammography (sensitivity, 73.9% vs 81.5%). Missed lesions concerned all types. Lesions detected with both protocols were described similarly (p = 0.084) with comparable work-up recommendations (p = 0.658).

Conclusion:

Mammography with ultra-low-dose CC images particularly influences detection. While sensitivity decreased, specificity was unaffected. In this proof-of-concept study a lower limit was to be determined that is not intended nor applicable for clinical practice. This should facilitate further research in optimization of a low-dose approach, which has potential in a relatively young and largely asymptomatic population.

Advances in knowledge:

Tungsten/silver-acquired mammography images might facilitate substantial dose reduction. Ultra-low-dose CC images reduce sensitivity, but not specificity. Low-dose images have potential in a largely young and asymptomatic population; a baseline is set for further research in optimization of a low-dose approach.Mammography is the most widely used modality in breast imaging. An increasing number of females throughout the world undergo mammography frequently, either in the diagnostic or screening setting. With the growing incidence of breast cancer, and the decreasing age of onset, the demand for mammography, particularly in the younger population, is still rising. Also, a considerable number of high-risk females are identified and advised to have annual mammograms, as part of a multimodality approach, preceding regular screening. With this development, in a relatively young and largely asymptomatic population, every opportunity to lower radiation dose in mammography should be investigated.Standard mammography is gradually being extended to tomosynthesis. When used with synthetic two-dimensional (2D) mammography, the mean radiation dose might be comparable to standard mammography,¹ but lower doses are not to be expected. Moreover, implementation of a new technology, in screening and diagnostic imaging practices, takes both time and money. Therefore, in low-income countries and countries in transition, 2D mammography will continue to play a significant role for many years. Hence, ongoing research in radiation protection in this field is of undiminished importance.Since digitization of radiology, low-dose imaging is receiving increased attention. In digital mammography, radiation dose can be easily adapted. Owing to image processing, the unfavourable effect of dose reduction on image quality can be compensated for to a certain level. This has the potential to decrease dose level with different X-ray spectra without impairing lesion detectability. Mammography studies on dosimetry suggested that the radiologists'' performance in detecting abnormalities with standard radiation dose images and markedly dose-reduced images (33–55%) does not differ significantly.^2–4These results motivated us to perform a small-scale study on breast specimen with the objective to determine a threshold dose level for single views. The results of this experimental study show that application of a tungsten/silver (W/Ag) beam quality for low-dose imaging permits a substantial reduction of the average glandular dose (AGD), possibly up to 90%, in single digital mammographic images, irrespective of breast thickness, particularly in combination with post-process noise reduction.⁵In the present study, the potential of these low-dose images in a clinical setting was assessed. Physical image quality is not synonymous to perceived image quality or the clinical value of an image. The current information on this aspect of mammography is mainly based on phantom studies. As degradation of clinical performance caused by dose reduction is unacceptable, mammography systems use radiation dose levels that are set on the safe side. However, it is unclear at what point dose reduction starts to influence clinical performance negatively. Our study was set up to find information on this cross-over point, where dose reduction meets performance degradation. To investigate this, we set up a clinical observer study, evaluating the potential of low-dose imaging in digital mammography by analysing the effect of substantial dose reduction in craniocaudal (CC) views on clinical performance. We considered the CC view to be the most suitable candidate for this trial. As, in general, the CC view is most valuable for differentiation, for example, to distinguish suspect lesions from summation artefacts that concern as many as 83% of the one-view-only lesions,⁶ but much less so for detection, particularly when microcalcifications are concerned.⁷To determine the lower limit in dose reduction, we obtained additional images with an extremely low radiation dose. These images are meant to be compared with regular images and are not intended to set a baseline for clinical practice. Instead, this proof-of-concept study is intended to pave the way for further research. With data on both ends of the spectrum, intermediate dose levels can be simulated, generating a potential clinical alternative for the current protocols under specific circumstances. With this, we aim to do evidence-based and justified assessments of pragmatic dose reduction in mammography in the future. To our knowledge, this is the first clinical study dedicated to dose reduction in digital mammography.     

Validation of image quality in full-field digital mammography: Is the replacement of wet by dry laser printers justified?

OBJECTIVE: Dry laser printers have replaced wet laser printers to produce hard copies of high-resolution digital images, primarily because of environmental concerns. However, no scientific research data have been published that compare the image quality of dry and wet laser printers in full-field digital mammography (FFDM). This study questions the image quality of these printers. MATERIALS AND METHODS: Objective image quality parameters of both printers were evaluated using a standardized printer test image, i.e., optical density and detectability of specific image elements (lines, curves, and shapes). Furthermore, mammograms of 129 patients with different breast tissue composition patterns were imaged with both printers. A total of 1806 subjective image quality parameters (brightness, contrast, and detail detection of anatomic structures), the detectability of breast lesions, as well as diagnostic performance according to the BI-RADS classification were evaluated. In addition, the presence of film artifacts was investigated. RESULTS: Optical density values were equal for the dry and the wet laser printer. Detection of specific image elements on the printer test image was not different. Ratings of subjective image quality parameters were equal, as were the detectability of breast lesions and the diagnostic performance. Dry laser printer images showed more artifacts (164 versus 27). However, these artifacts did not influence image quality. CONCLUSION: Based on the evidence of objective and subjective parameters, a dry laser printer equals the image quality of a wet laser printer in FFDM. Therefore, not only for reasons of environmental preference, the replacement of wet laser printers by dry laser printers in FFDM is justified.     

Contrast-enhanced spectral mammography vs. mammography and MRI – clinical performance in a multi-reader evaluation

Objectives

To compare the diagnostic performance of contrast-enhanced spectral mammography (CESM) to digital mammography (MG) and magnetic resonance imaging (MRI) in a prospective two-centre, multi-reader study.

Methods

One hundred seventy-eight women (mean age 53 years) with invasive breast cancer and/or DCIS were included after ethics board approval. MG, CESM and CESM?+?MG were evaluated by three blinded radiologists based on amended ACR BI-RADS criteria. MRI was assessed by another group of three readers. Receiver-operating characteristic (ROC) curves were compared. Size measurements for the 70 lesions detected by all readers in each modality were correlated with pathology.

Results

Reading results for 604 lesions were available (273 malignant, 4 high-risk, 327 benign). The area under the ROC curve was significantly larger for CESM alone (0.84) and CESM?+?MG (0.83) compared to MG (0.76) (largest advantage in dense breasts) while it was not significantly different from MRI (0.85). Pearson correlation coefficients for size comparison were 0.61 for MG, 0.69 for CESM, 0.70 for CESM?+?MG and 0.79 for MRI.

Conclusions

This study showed that CESM, alone and in combination with MG, is as accurate as MRI but is superior to MG for lesion detection. Patients with dense breasts benefitted most from CESM with the smallest additional dose compared to MG.

Key Points

? CESM has comparable diagnostic performance (ROC-AUC) to MRI for breast cancer diagnostics.? CESM in combination with MG does not improve diagnostic performance.? CESM has lower sensitivity but higher specificity than MRI.? Sensitivity differences are more pronounced in dense and not significant in non-dense breasts.? CESM and MRI are significantly superior to MG, particularly in dense breasts.

     

Has the mammography quality standards act affected the mammography quality in North Carolina?

OBJECTIVE: The United States Food and Drug Administration implemented federal regulations governing mammography under the Mammography Quality Standards Act (MQSA) of 1992. During 1995, its first year in implementation, we examined the impact of the MQSA on the quality of mammography in North Carolina. MATERIALS AND METHODS: All mammography facilities were inspected during 1993-1994, and again in 1995. Both inspections evaluated mean glandular radiation dose, phantom image evaluation, darkroom fog, and developer temperature. Two mammography health specialists employed by the North Carolina Division of Radiation Protection performed all inspections and collected and codified data. RESULTS: The percentage of facilities that met quality standards increased from the first inspection to the second inspection. Phantom scores passing rate was 31.6% versus 78.2%; darkroom fog passing rate was 74.3% versus 88.5%; and temperature difference passing rate was 62.4% versus 86.9%. CONCLUSION: In 1995, the first year that the MQSA was in effect, there was a significant improvement in the quality of mammography in North Carolina. This improvement probably resulted from facilities' compliance with federal regulations.     

Why do women refrain from mammography screening?

IntroductionBreast cancer is the leading cause of death for middle-aged women in Sweden. Approximately 600,000 women are surveyed annually within the national screening program. However, 20% of Swedish women do not participate in mammography screening. Participation in mammography screening is a complex phenomenon that has many dimensions. The aim of this study was to explore the reasons why women refrain from mammography screening from the perspective of non-attending women.MethodA qualitative approach was chosen, and 10 women were interviewed. The interviews were analysed using qualitative content analysis.ResultsTwo categories were identified: individual needs and absence of active promotion. “Non-personalized system” was the main theme that emerged from the analysis.ConclusionThe mammography screening does not adapt to the needs of each individual. This may be the reason why some women refrain from mammography screening.     

Can positron emission mammography help to identify clinically significant breast cancer in women with suspicious calcifications on mammography?

Objective

To evaluate the diagnostic accuracy of positron emission mammography (PEM) for identifying malignant lesions in patients with suspicious microcalcifications detected on mammography.

Methods

A prospective, single-centre study that evaluated 40 patients with suspicious calcifications at mammography and indication for percutaneous or surgical biopsy, with mean age of 56.4 years (range: 28-81 years). Patients who agreed to participate in the study underwent PEM with 18F-fluorodeoxyglucose before the final histological evaluation. PEM findings were compared with mammography and histological findings.

Results

Most calcifications (n?=?34; 85.0 %) were classified as BIRADS 4. On histology, there were 25 (62.5 %) benign and 15 (37.5 %) malignant lesions, including 11 (27.5 %) ductal carcinoma in situ (DCIS) and 4 (10 %) invasive carcinomas. On subjective analysis, PEM was positive in 15 cases (37.5 %) and most of these cases (n?=?14; 93.3 %) were confirmed as malignant on histology. There was one false-positive result, which corresponded to a fibroadenoma, and one false negative, which corresponded to an intermediate-grade DCIS. PEM had a sensitivity of 93.3 %, specificity of 96.0 % and accuracy of 95 %.

Conclusion

PEM was able to identify all invasive carcinomas and high-grade DCIS (nuclear grade 3) in the presented sample, suggesting that this method may be useful for further evaluation of patients with suspected microcalcifications.

Key Points

? Many patients with suspicious microcalcifications at mammography have benign results at biopsy. ? PEM may help to identify invasive carcinomas and high-grade DCIS. ? Management of patients with suspicious calcifications can be improved.

     

Evaluation of the diagnostic value of a computed radiography system by comparison of digital hard copy images with screen–film mammography: results of a prospective clinical trial

The purpose of the study was to determine prospectively the diagnostic value of a computed radiography (CR) system by comparing mammographic hard copy images with screen–film mammography (SFM). A series of 100 patients, who came for diagnostic investigation, underwent two-view SFM (Lorad M-IV Platinum) and digital mammography with a CR system (AGFA CR system). The images were obtained by double exposure, i.e. same view without removing compression of the corresponding breast. The CR images were processed with dedicated processing for mammography. Six radiologists read sets of SFM and CR images. The primary efficacy parameter was the overall diagnostic value. The secondary efficacy parameters were lesion conspicuity and lesion details (for masses and micro-calcifications), tissue visibility at chest wall and at skin line, axillary details, overall density and sharpness impression and the overall noise impression. These parameters were scored by a 7-point scoring system. “CR non-inferior to SFM” was concluded if the lower confidence interval bound exceeded 80%. The confidence interval for the overall diagnostic value was between 96.4% and 100%. Pooled analysis of the ten features for image quality comparison demonstrated for all but one feature (lesion details of the calcifications) CR non-inferiority to SFM.