Ruben E. van Engen

Breast Cancer Screening Results 5 Years after Introduction of Digital Mammography in a Population-based Screening Program

PURPOSE To compare full-field digital mammography (FFDM) using computer-aided diagnosis (CAD) with screen-film mammography (SFM) in a population-based breast cancer screening program for initial and subsequent screening examinations. MATERIALS AND METHODS The study was approved by the regional medical ethics review board. Informed consent was not required. In a breast cancer screening facility, two of seven conventional mammography units were replaced with FFDM units. Digital mammograms were interpreted by using soft-copy reading with CAD. The same team of radiologists was involved in the double reading of FFDM and SFM images, with differences of opinion resolved in consensus. After 5 years, screening outcomes obtained with both modalities were compared for initial and subsequent screening examination findings. RESULTS A total of 367,600 screening examinations were performed, of which 56,518 were digital. Breast cancer was detected in 1927 women (317 with FFDM). At initial screenings, the cancer detection rate was .77% with FFDM and .62% with SFM. At subsequent screenings, detection rates were .55% and .49%, respectively. Differences were not statistically significant. Recalls based on microcalcifications alone doubled with FFDM. A significant increase in the detection of ductal carcinoma in situ was found with FFDM (P < .01). The fraction of invasive cancers with microcalcifications as the only sign of malignancy increased significantly, from 8.1% to 15.8% (P < .001). Recall rates were significantly higher with FFDM in the initial round (4.4% vs 2.3%, P < .001) and in the subsequent round (1.7% vs 1.2%, P < .001). CONCLUSION With the FFDM-CAD combination, detection performance is at least as good as that with SFM. The detection of ductal carcinoma in situ and microcalcification clusters improved with FFDM using CAD, while the recall rate increased.

Consequences of digital mammography in population-based breast cancer screening: initial changes and long-term impact on referral rates

Objectives:To investigate the referral pattern after the transition to full-field digital mammography (FFDM) in a population-based breast cancer screening programme.Methods:Preceding the nationwide digitalisation of the Dutch screening programme, an FFDM feasibility study was conducted. Detection and referral rates for FFDM and screen-film mammography (SFM) were compared for first and subsequent screens. Furthermore, radiological characteristics of referrals in digital screening were assessed.Results:A total of 312,414 screening mammograms were performed (43,913 digital and 268,501 conventional), with 4,473 consecutive referrals (966 following FFDM). Initially the FFDM referral rate peaked, and many false-positive results were noted as a consequence of pseudolesions and increased detection of (benign) microcalcifications. A higher overall referral rate was observed in FFDM screening in both first and subsequent examinations (p < .001), with a significant increase in cancer detection (p = .010).Conclusion:As a result of initial inexperience with digital screening images implementing FFDM in a population-based breast cancer screening programme may lead to a strong, but temporary increase in referral. Dedicated training in digital screening for radiographers and screening radiologists is therefore recommended. Referral rates decrease and stabilise (learning curve effect) at a higher level than in conventional screening, yet with significantly enhanced cancer detection.

Evaluation of software for reading images of the CDMAM test object to assess digital mammography systems

European Guidelines for quality control in digital mammography specify minimum and achievable standards of image quality in terms of threshold contrast, based on readings of images of the CDMAM test object by human observers. However this is time-consuming and has large inter- and intra-observer error. To overcome these problems a software program (CDCOM) is available to automatically read CDMAM images. After some further analysis the automated measurements can be used to predict the threshold contrast for a typical observer. The results of threshold contrast determination by human observers at three different centres were compared against automated readings. These data provide a means of predicting average human performance using the automated reading software. The coefficient of variation in automatically determined threshold gold thickness was about 4% for detail sizes from 0.2 to 1.0mm when 8 images were analysed. The coefficient of variation was about 10% at a detail size of 0.1mm. Using larger numbers of images improved reproducibility for all detail sizes. A change in phantom design could greatly improve reproducibility for the smallest detail sizes. Greater consistency of phantom construction would also be desirable as one of the four phantoms tested was significantly different from the other three. Despite some limitations automated reading of CDMAM images can provide a reproducible means of assessing digital mammography systems against European Guidelines.

Comparison of a flexible versus a rigid breast compression paddle: pain experience, projected breast area, radiation dose and technical image quality

AbstractPurposeTo compare pain, projected breast area, radiation dose and image quality between flexible (FP) and rigid (RP) breast compression paddles.MethodsThe study was conducted in a Dutch mammographic screening unit (288 women). To compare both paddles one additional image with RP was made, consisting of either a mediolateral-oblique (MLO) or craniocaudal-view (CC). Pain experience was scored using the Numeric Rating Scale (NRS). Projected breast area was estimated using computer software. Radiation dose was estimated using the model by Dance. Image quality was reviewed by three radiologists and three radiographers.ResultsThere was no difference in pain experience between both paddles (mean difference NRS: 0.08 ± 0.08, p = 0.32). Mean radiation dose was 4.5 % lower with FP (0.09 ± 0.01 p = 0.00). On MLO-images, the projected breast area was 0.79 % larger with FP. Paired evaluation of image quality indicated that FP removed fibroglandular tissue from the image area and reduced contrast in the clinically relevant retroglandular area at chest wall side.ConclusionsAlthough FP performed slightly better in the projected breast area, it moved breast tissue from the image area at chest wall side. RP showed better contrast, especially in the retroglandular area. We therefore recommend the use of RP for standard MLO and CC views.Key points• Pain experience showed no difference between flexible and rigid breast compression paddles. • Flexible paddles do not depict clinically relevant retroglandular areas as well. • Flexible paddles move breast tissue from image area at the chest wall side. • Rigid paddles depict more breast tissue and shows better contrast. • Rigid breast compression paddles are recommended for standard mediolateral-oblique and craniocaudal views.

A Monte Carlo model for mean glandular dose evaluation in spot compression mammography

Purpose To characterize the dependence of normalized glandular dose (DgN) on various breast model and image acquisition parameters during spot compression mammography and other partial breast irradiation conditions, and evaluate alternative previously proposed dose‐related metrics for this breast imaging modality. Methods Using Monte Carlo simulations with both simple homogeneous breast models and patient‐specific breasts, three different dose‐related metrics for spot compression mammography were compared: the standard DgN, the normalized glandular dose to only the directly irradiated portion of the breast (DgNv), and the DgN obtained by the product of the DgN for full field irradiation and the ratio of the mid‐height area of the irradiated breast to the entire breast area (DgNM). How these metrics vary with field‐of‐view size, spot area thickness, x‐ray energy, spot area and position, breast shape and size, and system geometry was characterized for the simple breast model and a comparison of the simple model results to those with patient‐specific breasts was also performed. Results The DgN in spot compression mammography can vary considerably with breast area. However, the difference in breast thickness between the spot compressed area and the uncompressed area does not introduce a variation in DgN. As long as the spot compressed area is completely within the breast area and only the compressed breast portion is directly irradiated, its position and size does not introduce a variation in DgN for the homogeneous breast model. As expected, DgN is lower than DgNv for all partial breast irradiation areas, especially when considering spot compression areas within the clinically used range. DgNM underestimates DgN by 6.7% for a W/Rh spectrum at 28 kVp and for a 9 × 9 cm2 compression paddle. Conclusion As part of the development of a new breast dosimetry model, a task undertaken by the American Association of Physicists in Medicine and the European Federation of Organizations of Medical Physics, these results provide insight on how DgN and two alternative dose metrics behave with various image acquisition and model parameters.

Mammography with and without radiolucent positioning sheets : Comparison of projected breast area, pain experience, radiation dose and technical image quality

PURPOSE To compare projected breast area, image quality, pain experience and radiation dose between mammography performed with and without radiolucent positioning sheets. METHODS 184 women screened in the Dutch breast screening programme (May-June 2012) provided written informed consent to have one additional image taken with positioning sheets. 5 cases were excluded (missing data). Pain was scored using the Numeric Rating Scale. Radiation dose was estimated using the Dance model and projected breast area using computer software. Two radiologists and two radiographers assessed image quality. RESULTS With positioning sheets significantly more pectoral muscle, lateral and medial breast tissue was projected (CC-views) and more and deeper depicted pectoral muscle (MLO-views). In contrast, visibility of white and darker areas was better on images without positioning sheets, radiologists were therefore better able to detect abnormalities (MLO-views). Women experienced more pain with positioning sheets (MLO-views only, mean difference NRS 0.98; SD 1.71; p=0,00). CONCLUSION Mammograms with positioning sheets showed more breast tissue. Increased breast thickness after compression with sheets resulted in less visibility of white and darker areas and thus reduced detection of abnormalities. Also, women experienced more pain (MLO-views) due to the sheet material. A practical consideration is the fact that more subcutaneous fat tissue and skin are being pulled forward leading to folds in the nipple area. On balance, improvement to the current design is required before implementation in screening practice can be considered.

Image Quality Measurements in Breast Tomosynthesis

Breast tomosynthesis systems are developed by a number of manufacturers. It is desirable to have methods for image quality evaluation that can be used for quality control and minimum performance. In this study methods of measurement of three aspects of image quality (homogeneity, artifacts and detail detection on a homogeneous background) are evaluated on a prototype tomosynthesis system. The homogeneity evaluation showed that pixel value and standard deviation varied by up to respectively 6% and 30% in the tomosynthesis image. Artifacts have been quantified using an aluminium sphere of 2 mm diameter. In the plane of the object higher pixel value artefacts were visible. In all other planes artefacts were also visible. The detail detection did not fulfil the limiting values of threshold contrast for projection mammography, but image quality might have been underestimated. Homogeneity, detail detection and artifacts should be evaluated in future quality control procedures for tomosynthesis.

A supplement to the european guidelines for quality assurance in breast cancer screening and diagnosis

In 2006 the fourth edition of the European Guidelines for Breast Cancer Screening and Diagnosis was published by the European Commission Due to the fast developments in the field of digital mammography and the experience with digital mammography systems over the past years a supplement to the technical quality control procedures proved necessary This paper describes important changes compared to the Guidelines and their rationale Testing methods which are new or have changed include: the size of the standard region of interest (ROI), the thickness compensation measurement, noise evaluation, threshold contrast visibility, an AEC measurement which simulates local dense area A paragraph on evaluation of image processing has been added With these changes European quality control procedures are again up-to-date with current knowledge.

Quality Control in Digital Mammography

An effective quality control system for digital mammography needs to evaluate the status of each stage of image formation — acquisition, processing and display. Such quality control benefits greatly from the ability to make more precise and reproducible measurements than was possible with film-screen systems. On the other hand, the greater variety of system designs and general lack of experience with different digital systems has complicated the introduction of quality control (QC) procedures. Those with extensive experience of QC in digital mammography have stressed the importance of checking regularly for artifacts in images of uniform test blocks for the early detection of any problems arising in the image acquisition stage, e.g. the detector. Although the tests for the subsequent stages of image processing and display are less well developed, they are of considerable importance and will be the focus of further work. Digital technology makes possible the automation of routine QC procedures and a method of doing this is described.

New reconstruction algorithm for digital breast tomosynthesis: better image quality for humans and computers:

Background The image quality of digital breast tomosynthesis (DBT) volumes depends greatly on the reconstruction algorithm. Purpose To compare two DBT reconstruction algorithms used by the Siemens Mammomat Inspiration system, filtered back projection (FBP), and FBP with iterative optimizations (EMPIRE), using qualitative analysis by human readers and detection performance of machine learning algorithms. Material and Methods Visual grading analysis was performed by four readers specialized in breast imaging who scored 100 cases reconstructed with both algorithms (70 lesions). Scoring (5-point scale: 1 = poor to 5 = excellent quality) was performed on presence of noise and artifacts, visualization of skin-line and Cooper’s ligaments, contrast, and image quality, and, when present, lesion visibility. In parallel, a three-dimensional deep-learning convolutional neural network (3D-CNN) was trained (n = 259 patients, 51 positives with BI-RADS 3, 4, or 5 calcifications) and tested (n = 46 patients, nine positives), separately with FBP and EMPIRE volumes, to discriminate between samples with and without calcifications. The partial area under the receiver operating characteristic curve (pAUC) of each 3D-CNN was used for comparison. Results EMPIRE reconstructions showed better contrast (3.23 vs. 3.10, P = 0.010), image quality (3.22 vs. 3.03, P < 0.001), visibility of calcifications (3.53 vs. 3.37, P = 0.053, significant for one reader), and fewer artifacts (3.26 vs. 2.97, P < 0.001). The 3D-CNN-EMPIRE had better performance than 3D-CNN-FBP (pAUC-EMPIRE = 0.880 vs. pAUC-FBP = 0.857; P < 0.001). Conclusion The new algorithm provides DBT volumes with better contrast and image quality, fewer artifacts, and improved visibility of calcifications for human observers, as well as improved detection performance with deep-learning algorithms.