Characterization of microcalcification: can digital monitor zooming replace magnification mammography in full-field digital mammography?

The aim of this study was to compare the diagnostic accuracy and image quality of microcalcifications in zoomed digital contact mammography with digital magnification mammography. Three radiologists with different levels of experience in mammography reviewed 120 microcalcification clusters in 111 patients with a full-field digital mammography system relying on digital magnification mammogram (MAG) images and zoomed images from contact mammography (ZOOM) using commercially available zooming systems on monitors. Each radiologist estimated the probability of malignancy and rated the image quality and confidence rate. Performance was evaluated by sensitivity, specificity, positive predictive value, negative predictive value, and receiver operating characteristic (ROC) analysis. All three radiologists rated MAG images higher than ZOOM images for sensitivity with statistical significance (average value, 92% vs. 87%, P < 0.05) and performance by ROC analysis improved with MAG imaging. The confidence rate for diagnosis decision and the assessment of lesion characteristics were also better in MAG images than in ZOOM images with statistical significance (P < 0.0001). Digital magnification mammography can enhance diagnostic performance when characterizing microcalcifications. Images zoomed from digital contact mammography cannot serve as an alternative to direct magnification digital mammography. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (KRF-2007-313-E00363).     

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.     

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.     

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).

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.     

“CADEAT”: considerations on the use of CAD (computer-aided diagnosis) in mammography

Computer-aided diagnosis (CAD) has been extensively reported to increase sensitivity by about 10% when added to a single reading while increasing recall rate by 12%, and its current use can be safely recommended in clinical practice. CAD has been suggested as a possible alternative to conventional double reading in screening. Uncontrolled comparison is consistent and suggests that CAD is comparable to double reading in incremental cancer detection rate (CAD +10.6%, double reading +9.1%) and possibly better in recall rate (CAD +12.5%, double reading +28.8%). However, controlled studies comparing single reading + CAD to conventional double reading are not consistent and on average suggest a lower cancer detection rate (?5.1%) and a lower recall rate (?9.8%) for CAD. Scientific evidence is not sufficient for a safe recommendation of single reading + CAD as a current alternative to conventional double reading.     

Analysis of interval cancers observed in an Italian mammography screening programme (2000–2006)

Purpose

The purpose of this study was to assess the interval cancer (IC) proportional incidence and review IC cases observed in an Italian mammography screening programme during 2000–2006.

Materials and methods

ICs were identified through linkage of a screening database with the local cancer registry and hospital discharge records to calculate proportional (observed/expected) incidence. Negatively reported mammograms preceding ICs underwent blind review (randomly mixed with negative controls in a 2:1 ratio) by three expert radiologists and classified according to European guidelines criteria (OC=occult, MS=minimal sign, SE=screening error) according to majority report. Proportional IC incidence and rate of reviewed IC classified as SE were compared with European guideline standards.

Results

Proportional IC incidence was 10.8% in the first and 40.0% in the second year of the interval (European standard=30% or 50%, respectively). Sensitivity estimate for the 2-year interval was 74.6%. ICs were reviewed as SE, MS or OC in 15.0%, 14.0% or 71.0% of cases, respectively. Corresponding review results for negative controls were 7.0%, 25.0% or 68.0%, respectively. Positive predictive value for IC was 51.7% for SE and 21.8% for MS reporting category, respectively (p=0.008). European standard (<20% reviewed as SE) was reached.

Conclusions

The study shows that the sensitivity of the mammography programme was good, complying with European guideline recommendations. Assessment of IC-based early indicators of screening efficacy is feasible in a current screening programme and should become a routine procedure.     

Computer-assisted diagnosis (CAD) in mammography: comparison of diagnostic accuracy of a new algorithm (Cyclopus®, Medicad) with two commercial systems

Purpose

The study compares the diagnostic accuracy (correct identification of cancer) of a new computer-assisted diagnosis (CAD) system (Cyclopus) with two other commercial systems (R2 and CADx).

Materials and methods

Cyclopus was tested on a set of 120 mammograms on which the two compared commercial systems had been previously tested. The set consisted of mammograms reported as negative, preceding 31 interval cancers reviewed as screening error or minimal sign, and of 89 verified negative controls randomly selected from the same screening database.

Results

Cyclopus sensitivity was 74.1% (R2=54.8%; CADx=41.9%) and was higher for interval cancers reviewed as screening error (90.9%; R2=54.5%; CADx=81.8%) compared with those reviewed as minimal sign (65.0%; R2=55.0%; CADx=20.0%). Specificity was 15.7% (R2=29.2%; CADx=17.9%). Overall accuracy was 30.8% (R2=35.8%; CADx=24.1%). The positive predictive value of a case with CAD marks [regions of interest (ROI)] was 23.4% (23/98; R2=16.0%; CADx=15.1%). Average ROI number per view among negative controls was 1.13 (R2=0.93; CADx=0.99). Cyclopus was more sensitive for masses compared with isolated microcalcifications (208 vs 62 ROI; R2=90 vs 213; CADx=192 vs 130).

Conclusions

Compared with two other commercial systems, Cyclopus was more sensitive (R2 p=0.14; CADx p=0.02) and less specific (R2 p=0.02; CADx p=0.64).     

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.     

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.     

Can the size of microcalcifications predict malignancy of clusters at mammography?

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether the size of mammographically detected microcalcifications is predictive of malignancy. MATERIALS AND METHODS: Two hundred sixty mammograms showing clustered microcalcifications with proven diagnoses (160 malignant, 100 benign) were respectively reviewed by experienced mammographers. Lesions that were obviously benign in appearance were excluded from the study. A computer-aided diagnosis system digitized the lesions at 600 dpi, and the microcalcifications on the digital image were interactively defined by mammographers. Subsequently, three quantitative features that reflected the size of the microcalcifications-length, area, and brightness-were automatically extracted by the system. For each feature, the standard average of values obtained for individual calcifications within the cluster and the average with emphasis on extreme values (E) obtained in a single cluster were analyzed and matched with pathologic results. RESULTS: In the malignant group of cases, the mean values of the standard average length and area were significantly higher (P < .0001) than the mean values in the benign group. Distribution analysis demonstrated that an average length of more than 0.41 mm was associated with malignant lesions 77% of the time, while an average length of less than 0.41 mm was associated with benign lesions 71% of the time. The mean of the average length (E) and area (E) of microcalcifications within the cluster demonstrated an even higher discriminative power when compared with the standard average length and area. The average brightness, on the other hand, showed only a low discriminative power. CONCLUSION: Digital computerized analysis of mammographically detected calcifications demonstrated that the average length and area of the calcifications in benign clusters were significantly smaller than those in malignant clusters.     

Can mechanical imaging increase the specificity of mammography screening?

Objectives

This study aimed to investigate the effects of adding adjunct mechanical imaging to mammography breast screening. We hypothesized that mechanical imaging could detect increased local pressure caused by both malignant and benign breast lesions and that a pressure threshold for malignancy could be established. The impact of this on breast screening was investigated with regard to reductions in recall and biopsy rates.

Methods

155 women recalled from breast screening were included in the study, which was approved by the regional ethical review board (dnr 2013/620). Mechanical imaging readings were acquired of the symptomatic breast. The relative mean pressure on the suspicious area (RMPA) was defined and a threshold for malignancy was established.

Results

Biopsy-proven invasive cancers had a median RMPA of 3.0 (interquartile range (IQR)?=?3.7), significantly different from biopsy-proven benign at 1.3 (IQR?=?1.0) and non-biopsied cases at 1.0 (IQR?=?1.3) (P?<?0.001). The lowest RMPA for invasive cancer was 1.4, with 23 biopsy-proven benign and 33 non-biopsied cases being below this limit. Had these women not been recalled, recall rates would have been reduced by 36% and biopsy rates by 32%.

Conclusions

If implemented in a screening situation, this may substantially lower the number of false positives.

Key Points

? Mechanical imaging is used as an adjunct to mammography in breast screening. ? A threshold pressure can be established for malignant breast cancer. ? Recalls and biopsies can be substantially reduced.

     

Lack of Correlation between Radiosensitivity and Inhibition of DNA Synthesis in Hybrids (A-T × HeLa)

Summary

Hybrid cells obtained from A-T and D98/AH(HeLa) cells showed normal radiation sensitivity to cell killing, but retained radioresistant DNA synthesis similar to parental A-T cells.     

Are unnecessary follow-up procedures induced by computer-aided diagnosis (CAD) in mammography? Comparison of mammographic diagnosis with and without use of CAD

OBJECTIVE: To evaluate the rate of unnecessary follow-up procedures recommended by radiologists using a CAD-system. MATERIALS AND METHODS: 185 patients (740 images) were consecutively selected from three groups (36 histologically proven cancers = group 1; 49 histologically proven benign lesions = group 2 and 100 screening cases (4 years-follow up = group 3). Mammograms were evaluated by a CAD system (Second Look, CADx, Canada). Five blinded radiologists assessed the images without/with CAD outputs. Diagnostic decisions were ranked from surely benign to surely malignant according to BIRADS classification, follow-up procedures were recommended for each observed lesion (a, screening; b, short interval follow-up examination in 6 months; c, pathologic clarification). RESULTS: CAD-system detected 32/36 cancers (88.9%) (FP-rate: 1.04 massmarks and 0.27 calcmarks/image). The following values were reached by all observers without/with CAD in the mean: Sensitivity 80.6/80.0%, specificity 83.2/86.4%, PPV 53.1/58.1%, and NPV 94.6/94.7%. Observers described a similar number of additional lesions without/with the use of CAD (325/326). Whereas the number of unnecessary short-time follow up recommendations increased in all case-subgroups with CAD: 40.8/42.9% (group 1), 35.6/38.1% (group 2), 44.7/46.8% (group 3), respectively, the number of recommended biopsies decreased in all subgroups: group 1: 34.7/27.1%; group 2: 47.4/41.5%, group 3: 33.3/22.0%, respectively. CONCLUSION: In this rather small population additional usage of CAD led to a lower rate of unnecessary biopsies. The observed decrease of recommended unnecessary biopsies due to the usage of CAD in the screening group suggests a potential financial benefit by using CAD as diagnostic aid.