Evaluation of a computer-aided detection (CAD)-enhanced 2D synthetic mammogram: comparison with standard synthetic 2D mammograms and conventional 2D digital mammography

Digital breast tomosynthesis (DBT) when combined with standard 2D digital mammography has been shown to improve the performance of breast cancer screening by increasing cancer detection rates [1-5]. The 2D component remains an important part of the examination and is used to facilitate assessment of symmetry between the breasts, aid comparison with prior mammograms and identify the presence of breast microcalcifications where the evidence for detection with DBT is less robust [1]. The mean glandular dose per view of a DBT image is around 2.3 mGy, which is between 1 - 1.5x more than the dose of standard 2D digital mammography [6]. Acquiring both a DBT and standard 2D digital mammogram on each woman leads to at least a doubling of the radiation dose, which may not be considered acceptable in an asymptomatic screening population. Consequently there has been much interest in the generation of synthetic 2D mammograms from the DBT data set eliminating the additional radiation burden of a separate 2D digital mammogram. There is evidence from prospective and retrospective studies to support the use of synthetic 2D mammograms [5,7-9]. Several retrospective multi-reader studies, including the UK TOMMY trial, have demonstrated comparable performance between synthetic and conventional 2D mammography [7,8]. The Oslo and Storm-2 prospective studies of DBT in breast cancer screening found equivalent cancer detection rates regardless of whether the conventional 2D or the synthetic mammograms were read, concluding that synthetic mammograms were an acceptable replacement for directly acquired conventional 2D mammograms [5,9]. Another approach to improve performance is to combine the synthesised image with a Computer Aided Detection (CAD) algorithm. CAD has been used over the years to assist with the interpretation of 2D mammography. CAD software places marks or prompts on the images to draw the reader’s attention to potential areas of concern, reducing observational oversights. A CAD algorithm has been developed with machine learning technology (iCAD Inc., Nashua , NH, USA and GE Healthcare, Buc, France) to assist in the detection of breast cancer on DBT images. Unlike a conventional CAD system which places marks on the image, areas of concern are automatically identified on each tomosynthesis slice and then blended onto a 2D synthetic image to provide a single CAD enhanced 2D synthetic image for each mammographic projection. The aim of this study was to evaluate the diagnostic performance of the CAD enhanced synthetic mammogram in comparison with standard 2D synthetic mammograms generated from the DBT data set and standard 2D digital mammography

Performance testing for radiologists interpreting chest radiographs

Performance testing for radiologists interpreting chest radiograph

Measuring performance in the interpretation of chest radiographs: a pilot study

AIM: To develop a system to assess the image interpretation performance of radiologists in identifying signs of malignancy on chest radiographs. MATERIALS AND METHODS: A test set of 30 chest radiographs was chosen by an experienced radiologist consisting of 11 normal and 19 abnormal cases. The malignant cases all had biopsyproven pathology; the normal and benign cases all had at least 2 years of imaging follow-up. Fourteen radiologists with a range of experiences were recruited. Participants individually read the test set displayed on a standard reporting workstation, with their findings entered directly into a laptop running specially designed reporting software. For each case, relevant clinical information was given and the reader was asked to mark any perceived abnormality and rate their level of suspicion on a five-point scale (normal, benign, indeterminate, suspicious, or malignant). On completion, participants were given instant feedback with performance parameters including sensitivity and specificity automatically calculated. An opportunity was then given to review the cases together with an expert opinion and pathology. The time each participant took to complete the test was recorded. RESULTS: Six consultant radiologists who took part showed significantly better performance as determined by receiver operating characteristic (ROC) analysis compared to eight specialist registrars (area under the ROC curve [AUC]¼0.9297 and 0.7648 respectively, p¼0.003). There was a significant correlation with years of experience in the interpretation of chest radiographs and performance on the test set (r¼0.573, p¼0.032). Consultant radiologists completed the test significantly more quickly that the specialist registrars: mean time 19.65 minutes compared to 26.51 minutes (p¼0.033). CONCLUSION: It is possible to use a test set to measure individual differences in the interpretation of chest radiographs. This has the potential to be a useful tool in performance testing

Is image manipulation necessary to interpret digital mammographic images efficiently?

With the introduction of digital breast screening across the UK, screeners need to learn how best to inspect these images. A key advantage over mammographic film is the facility to use workstation image manipulation tools. Forty two-view FFDM screening cases, representing malignant, normal and benign appearances were examined by fourteen radiologists and advanced practitioners from two UK screening centres. For half the cases, the mammography workstation image manipulation tools could be employed and for the other half these were not used. Participants classified each case and indicated whether an abnormality was present. Throughout the study the participants’ visual search behaviour as well as their image manipulations was recorded. Whether or not image manipulation tools were used made very little difference to overall performance (t-test, p>.05) as confirmed by JAFROC analysis Figure-Of-Merit values of 0.816 and 0.838 (with and without tools respectively); performance not using tools was better. However, using tools significantly increased inspection time (p<0.5) as well as participants’ confidence. Detailed examination of participants’ image inspection behaviour elicited that the average time on each case in the different viewing conditions differed significantly between the high experienced readers and low experienced readers. The visual data analysis revealed that the participants made similar overall pattern of errors on both modalities. The visual search behaviour on both modalities are surprisingly similar

Breast screening: visual search as an aid for digital mammographic interpretation training

Digital mammography is gradually being introduced across all breast screening centres in the UK during 2010. This provides increased training opportunities using lower resolution, lower cost and more widely available devices, in addition to the clinical digital mammography workstations. This study examined how experienced breast screening personnel performed when they examined sets of difficult DICOM two-view screening cases in three conditions: on GE digital mammography workstations, on a standard LCD monitor (using a DICOM viewer) and an iPhone (running Osirix software). In each condition they either viewed the full images unaided or were permitted to use the post-processing manipulations of pan, zoom and window level/width adjustments. For each case they had to report the feature type, rate their confidence on the presence of abnormality, classify the case and specify case density. Their visual search behaviour was recorded throughout using a head mounted eye tracker. Additionally aspects of their real life screening performance and performance on a national self assessment scheme were examined. Data indicate that screening experience plays a major role in doing well on the self assessment scheme. Task performance was best on the clinical workstation. However, the data also suggest that a DICOM viewer that runs on a PC or laptop with a standard LCD display allows viewing digital images in full resolution support impressive cancer detection performance. The iPhone is not ideal for examining full images due to the amount of scrolling and zooming required. Overall, the results indicate that low cost devices could be used to provide additional tailored training as long as device resolution and HCI aspects are carefully considered

Contrast-enhanced spectral mammography: what is the 'added value' in a symptomatic setting? Initial findings from a UK centre

Contrast-enhanced spectral mammography (CESM) is a new technology. Dual energy acquisitions during one exposure yield two sets of images: a low energy (LE) set, equivalent to standard full field digital mammography (FFDM); and a recombined set displaying contrast uptake. In our symptomatic breast service, specific patients, including those with a P4/5 clinical abnormality are offered CESM instead of FFDM. Despite encouraging data from Europe and the USA, there are, until now, no UK data to support its use in this setting

Contrast-enhanced spectral mammography improves diagnostic accuracy in the symptomatic setting

Aim. To assess the diagnostic accuracy of Contrast Enhanced Spectral Mammography (CESM), and gauge its “added value” in the symptomatic setting. Methods. At our institution, women aged 35-70 years with a suspicious or malignant clinical abnormality are offered CESM instead of standard Full-Field Digital Mammography (FFDM) as an initial imaging test. CESM is also offered to younger women whose ultrasound is suspicious, or who have biopsy-proven malignancy. It is occasionally used as an alternative to breast MRI following multi-disciplinary team discussion. We performed a retrospective multi-reader review of 100 consecutive CESM examinations. Anonymised Low Energy (LE) images were reviewed and given a score for malignancy. At least 3 weeks later, the entire examination (LE and recombined images) was reviewed. Pathology data was obtained for all cases. Differences in performance were assessed using receiver operative characteristic (ROC) analysis. Sensitivity, specificity and lesion size (vs MRI or histopathology) differences were calculated. Results. 73% cases were malignant at final histology, 27% were benign following standard triple assessment. ROC analysis showed improved overall performance of CESM over LE alone, with area under the curve of 93% vs 83% (p<0.025). CESM showed increased sensitivity (95% vs 84, p<0.025) and specificity (81% vs 63%, p<0.025) compared to LE alone, with all 5 readers showing improved accuracy. Tumour size estimation at CESM was significantly more accurate than LE alone, the latter tending to undersize lesions. In 75% of cases CESM was deemed a useful or significant aid to diagnosis. Conclusion. CESM provides immediately available, clinically useful information in the symptomatic clinic in patients with suspicious palpable abnormalities. Radiologist sensitivity, specificity and size accuracy for breast cancer detection and staging are all improved using CESM as the primary mammographic investigation

Accuracy of GE digital breast tomosynthesis vs supplementary mammographic views for diagnosis of screen-detected soft-tissue breast lesions

Objective: To compare the accuracy of standard supplementary views and GE digital breast tomosynthesis (DBT) for assessment of soft-tissue mammographic abnormalities. Methods: Women recalled for further assessment of soft-tissue abnormalities were recruited and received standard supplementary views (typically spot compression views) and two-view GE DBT. The added value of DBT in the assessment process was determined by analysing data collected prospectively by radiologists working up the cases. Following anonymization of cases, there was also a retrospective multireader review. The readers first read bilateral standard two-view digital mammography (DM) together with the supplementary mammographic views and gave a combined score for suspicion of malignancy on a five-point scale. The same readers then read bilateral standard two-view DM together with two-view DBT. Pathology data were obtained. Differences were assessed using receiver operating characteristic analysis. Results: The study population was 342 lesions in 322 patients. The final diagnosis was malignant in 113 cases (33%) and benign/normal in 229 cases (67%). In the prospective analysis, the performance of two-view DM plus DBT was at least equivalent to the performance of two-view DM and standard mammographic supplementary views—the area under the curve (AUC) was 0.946 and 0.922, respectively, which did not reach statistical significance. Similar results were obtained for the retrospective review—AUC was 0.900 (DBT) and 0.873 (supplementary views), which did not reach statistical significance. Conclusion: The accuracy of GE DBT in the assessment of screen detected soft-tissue abnormalities is equivalent to the use of standard supplementary mammographic views. Advances in knowledge: The vast majority of evidence relating to the use of DBT has been gathered from research using Hologic equipment. This study provides evidence for the use of the commercially available GE DBT system demonstrating that it is at least equivalent to supplementary mammographic views in the assessment of soft-tissue screen-detected abnormalities

The use of lower resolution viewing devices for mammographic interpretation: implications for education and training

Aims To establish whether lower resolution, lower cost viewing devices have the potential to deliver mammographic interpretation training. Methods On three occasions over eight months, fourteen consultant radiologists and reporting radiographers read forty challenging digital mammography screening cases on three different displays: a digital mammography workstation, a standard LCD monitor, and a smartphone. Standard image manipulation software was available for use on all three devices. Receiver operating characteristic (ROC) analysis and ANOVA (Analysis of Variance) were used to determine the significance of differences in performance between the viewing devices with/without the application of image manipulation software. The effect of reader’s experience was also assessed. Results Performance was significantly higher (p<.05) on the mammography workstation compared to the other two viewing devices. When image manipulation software was applied to images viewed on the standard LCD monitor, performance improved to mirror levels seen on the mammography workstation with no significant difference between the two. Image interpretation on the smartphone was uniformly poor. Film reader experience had no significant effect on performance across all three viewing devices. Conclusion Lower resolution standard LCD monitors combined with appropriate image manipulation software are capable of displaying mammographic pathology, and are potentially suitable for delivering mammographic interpretation training. Key points • This study investigates potential devices for training in mammography interpretation. • Lower resolution standard LCD monitors are potentially suitable for mammographic interpretation training. • The effect of image manipulation tools on mammography workstation viewing is insignificant. • Reader experience had no significant effect on performance in all viewing devices. • Smart phones are not suitable for displaying mammograms