Digital breast tomosynthesis: observer performance of clustered microcalcification detection on breast phantom images acquired with an experimental system using variable scan angles, angular increments, and number of projection views.

PURPOSE: To investigate the dependence of microcalcification cluster detectability on tomographic scan angle, angular increment, and number of projection views acquired at digital breast tomosynthesis ( DBT digital breast tomosynthesis ). MATERIALS AND METHODS: A prototype DBT digital breast tomosynthesis system operated in step-and-shoot mode was used to image breast phantoms. Four 5-cm-thick phantoms embedded with 81 simulated microcalcification clusters of three speck sizes (subtle, medium, and obvious) were imaged by using a rhodium target and rhodium filter with 29 kV, 50 mAs, and seven acquisition protocols. Fixed angular increments were used in four protocols (denoted as scan angle, angular increment, and number of projection views, respectively: 16°, 1°, and 17; 24°, 3°, and nine; 30°, 3°, and 11; and 60°, 3°, and 21), and variable increments were used in three (40°, variable, and 13; 40°, variable, and 15; and 60°, variable, and 21). The reconstructed DBT digital breast tomosynthesis images were interpreted by six radiologists who located the microcalcification clusters and rated their conspicuity. RESULTS: The mean sensitivity for detection of subtle clusters ranged from 80% (22.5 of 28) to 96% (26.8 of 28) for the seven DBT digital breast tomosynthesis protocols; the highest sensitivity was achieved with the 16°, 1°, and 17 protocol (96%), but the difference was significant only for the 60°, 3°, and 21 protocol (80%, P < .002) and did not reach significance for the other five protocols (P = .01-.15). The mean sensitivity for detection of medium and obvious clusters ranged from 97% (28.2 of 29) to 100% (24 of 24), but the differences fell short of significance (P = .08 to >.99). The conspicuity of subtle and medium clusters with the 16°, 1°, and 17 protocol was rated higher than those with other protocols; the differences were significant for subtle clusters with the 24°, 3°, and nine protocol and for medium clusters with 24°, 3°, and nine; 30°, 3°, and 11; 60°, 3° and 21; and 60°, variable, and 21 protocols (P < .002). CONCLUSION: With imaging that did not include x-ray source motion or patient motion during acquisition of the projection views, narrow-angle DBT digital breast tomosynthesis provided higher sensitivity and conspicuity than wide-angle DBT digital breast tomosynthesis for subtle microcalcification clusters.

A similarity study of content-based image retrieval system for breast cancer using decision tree.

PURPOSE: We are developing a decision tree content-based image retrieval (DTCBIR) CADx system to assist radiologists in characterization of breast masses on ultrasound images. METHODS: Three DTCBIR configurations, including decision tree with boosting (DTb), decision tree with full leaf features (DTL), and decision tree with selected leaf features (DTLs) were compared. For DTb, features of a query mass were combined first into a merged feature score and then masses with similar scores were retrieved. For DTL and DTLs, similar masses were retrieved based on the Euclidean distance between feature vectors of the query and those of selected references. For each DTCBIR configuration, we investigated the use of full feature set and subset of features selected by the stepwise linear discriminant analysis (LDA) and simplex optimization method, resulting in six retrieval methods and selected five, DTb-lda, DTL-lda, DTb-full, DTL-full, and DTLs-full, for the observer study. Three MQSA radiologists rated similarities between the query mass and computer-retrieved three most similar masses using nine-point similarity scale (9 = very similar). RESULTS: For DTb-lda, DTL-lda, DTb-full, DTL-full, and DTLs-full, average A(z) values were 0.90 ± 0.03, 0.85 ± 0.04, 0.87 ± 0.04, 0.79 ± 0.05, and 0.71 ± 0.06, respectively, and average similarity ratings were 5.00, 5.41, 4.96, 5.33, and 5.13, respectively. CONCLUSIONS: The DTL-lda is a promising DTCBIR CADx configuration which had simple tree structure, good classification performance, and highest similarity rating.

Breast mass characterization using 3-dimensional automated ultrasound as an adjunct to digital breast tomosynthesis: a pilot study.

OBJECTIVES: The purpose of this study was to retrospectively evaluate the effect of 3-dimensional automated ultrasound (3D-AUS) as an adjunct to digital breast tomosynthesis (DBT) on radiologists' performance and confidence in discriminating malignant and benign breast masses. METHODS: Two-view DBT (craniocaudal and mediolateral oblique or lateral) and single-view 3D-AUS images were acquired from 51 patients with subsequently biopsy-proven masses (13 malignant and 38 benign). Six experienced radiologists rated, on a 13-point scale, the likelihood of malignancy of an identified mass, first by reading the DBT images alone, followed immediately by reading the DBT images with automatically coregistered 3D-AUS images. The diagnostic performance of each method was measured using receiver operating characteristic (ROC) curve analysis and changes in sensitivity and specificity with the McNemar test. After each reading, radiologists took a survey to rate their confidence level in using DBT alone versus combined DBT/3D-AUS as potential screening modalities. RESULTS: The 6 radiologists had an average area under the ROC curve of 0.92 for both modalities (range, 0.89-0.97 for DBT and 0.90-0.94 for DBT/3D-AUS). With a Breast Imaging Reporting and Data System rating of 4 as the threshold for biopsy recommendation, the average sensitivity of the radiologists increased from 96% to 100% (P > .08) with 3D-AUS, whereas the specificity decreased from 33% to 25% (P > .28). Survey responses indicated increased confidence in potentially using DBT for screening when 3D-AUS was added (P < .05 for each reader). CONCLUSIONS: In this initial reader study, no significant difference in ROC performance was found with the addition of 3D-AUS to DBT. However, a trend to improved discrimination of malignancy was observed when adding 3D-AUS. Radiologists' confidence also improved with DBT/3DAUS compared to DBT alone.

Similarity evaluation in a content-based image retrieval (CBIR) CADx system for characterization of breast masses on ultrasound images.

PURPOSE: The authors are developing a content-based image retrieval (CBIR) CADx system to assist radiologists in characterization of breast masses on ultrasound images. In this study, the authors compared seven similarity measures to be considered for the CBIR system. The similarity between the query and the retrieved masses was evaluated based on radiologists' visual similarity assessments. METHODS: The CADx system retrieves masses that are similar to a query mass from a reference library based on computer-extracted features using a k-nearest neighbor (k-NN) approach. Among seven similarity measures evaluated for the CBIR system, four similarity measures including linear discriminant analysis (LDA), Bayesian neural network (BNN), cosine similarity measure (Cos), and Euclidean distance (ED) similarity measure were compared by radiologists' visual assessment. For LDA and BNN, the features of a query mass were combined first into a malignancy score and then masses with similar scores were retrieved. For Cos and ED, similar masses were retrieved based on the normalized dot product and the Euclidean distance, respectively, between two feature vectors. For the observer study, three most similar masses were retrieved for a given query mass with each method. All query-retrieved mass pairs were mixed and presented to the radiologists in random order. Three Mammography Quality Standards Act (MQSA) radiologists rated the similarity between each pair using a nine-point similarity scale (1 = very dissimilar, 9 = very similar). The accuracy of the CBIR CADx system using the different similarity measures to characterize malignant and benign masses was evaluated by ROC analysis. RESULTS: The BNN measure used with the k-NN classifier provided slightly higher performance for classification of malignant and benign masses (A(z) values of 0.87) than those with the LDA, Cos, and ED measures (A(z) of 0.86, 0.84, and 0.81, respectively). The average similarity ratings of all radiologists for LDA, BNN, Cos, and ED were 4.71, 4.95, 5.18, and 5.32, respectively. The k-NN with the ED measures retrieved masses of significantly higher similarity (p < 0.008) than LDA and BNN. CONCLUSIONS: Similarity measures using the resemblance of individual features in the multidimensional feature space can retrieve visually more similar masses than similarity measures using the resemblance of the classifier scores. A CBIR system that can most effectively retrieve similar masses to the query may not have the best A(z).

Can preoperative axillary US help exclude N2 and N3 metastatic breast cancer?

PURPOSE: To determine the false-negative rate of axillary ultrasonography (US) with respect to stage N2 and N3 metastatic disease in patients with newly diagnosed breast cancer. MATERIALS AND METHODS: The study was approved by the institutional review board and complied with the HIPAA; the requirement for informed consent was waived. A retrospective search of radiology records identified 435 consecutive patients with breast cancer aged 25-88 years who underwent preoperative axillary US from January 1, 2006, to December 31, 2007. Two hundred five patients (203 women and two men) had 208 negative US scans with correlative surgical and/or pathologic lymph node data. Criteria used to detect abnormal lymph nodes included subjective assessment of diffuse cortical thickening, focal cortical mass/thickening, and replacement or effacement of the fatty hilum. Tumor type, grade, size, and hormone receptor status were documented. Statistical analysis was performed with the Fisher exact test. RESULTS: Of the 208 axillae with negative findings at US, 14 (6.7%) had a final node stage of N2 or N3. Twelve of the 208 axillae (5.8%) had stage N2 disease and two (1.0%) had stage N3 disease. Of the 14 axillae with stage N2 or N3 disease, eight (57.1%) had lobular histologic characteristics and six (42.9%) had ductal histologic characteristics. The false-negative rate for N2 and N3 disease was 4.1% (six of 146 axillae) for invasive ductal cancer and 17% (eight of 47 axillae) for invasive lobular cancer (P < .01). None of the 14 axillae with stage N2 or N3 disease were "triple negative" (ie, estrogen receptor negative, progesterone receptor negative, and human epidermal growth factor receptor type 2 negative). CONCLUSION: Preoperative axillary US excluded 96% of N2 and N3 invasive ductal metastases. The false-negative rate for N2 and N3 invasive lobular cancer was significantly higher than that for invasive ductal cancer, which suggests that axillary US cannot be used to exclude N2 and N3 metastases in these patients.

Multi-modality CADx: ROC study of the effect on radiologists' accuracy in characterizing breast masses on mammograms and 3D ultrasound images.

RATIONALE AND OBJECTIVES: To investigate the effect of a computer-aided diagnosis (CADx) system on radiologists' performance in discriminating malignant and benign masses on mammograms and three-dimensional (3D) ultrasound (US) images. MATERIALS AND METHODS: Our dataset contained mammograms and 3D US volumes from 67 women (median age, 51; range: 27-86) with 67 biopsy-proven breast masses (32 benign and 35 malignant). A CADx system was designed to automatically delineate the mass boundaries on mammograms and the US volumes, extract features, and merge the extracted features into a multi-modality malignancy score. Ten experienced readers (subspecialty academic breast imaging radiologists) first viewed the mammograms alone, and provided likelihood of malignancy (LM) ratings and Breast Imaging and Reporting System assessments. Subsequently, the reader viewed the US images with the mammograms, and provided LM and action category ratings. Finally, the CADx score was shown and the reader had the opportunity to revise the ratings. The LM ratings were analyzed using receiver-operating characteristic (ROC) methodology, and the action category ratings were used to determine the sensitivity and specificity of cancer diagnosis. RESULTS: Without CADx, readers' average area under the ROC curve, A(z), was 0.93 (range, 0.86-0.96) for combined assessment of the mass on both the US volume and mammograms. With CADx, their average A(z) increased to 0.95 (range, 0.91-0.98), which was borderline significant (P = .05). The average sensitivity of the readers increased from 98% to 99% with CADx, while the average specificity increased from 27% to 29%. The change in sensitivity with CADx did not achieve statistical significance for the individual radiologists, and the change in specificity was statistically significant for one of the radiologists. CONCLUSIONS: A well-trained CADx system that combines features extracted from mammograms and US images may have the potential to improve radiologists' performance in distinguishing malignant from benign breast masses and making decisions about biopsies.

Axillary staging prior to neoadjuvant chemotherapy for breast cancer: predictors of recurrence.

BACKGROUND: The value of axillary staging prior to delivery of neoadjuvant chemotherapy (NEO) for breast cancer is controversial. Our goal was to analyze the prognostic and therapeutic impact of axillary staging on recurrence. METHODS: The study cohort included 161 patients undergoing comprehensive evaluation by a multidisciplinary approach during the period 1996-2006. Clinicopathologic features were assessed before and after delivery of NEO. Patients with node-positive disease before NEO underwent a post-NEO axillary lymph node dissection at time of definitive breast surgery. RESULTS: At presentation, median age was 49 years; mean tumor size was 45 mm. The axilla was negative in 45 (28.6%) patients. Of the 114 pre-NEO node-positive patients, 65 (57%) were staged histologically. At completion of NEO, partial or complete clinical response was observed in 90.6%; complete pathologic response occurred in 23.6%. Mean residual tumor size was 10.5 mm. Of the 112 initially node-positive patients, 36 (31.6%) had no residual axillary disease post NEO. At median follow-up of 38.1 months, 21.7% patients relapsed. The pre-NEO nodal status was the strongest predictor of treatment failure. A significant risk of distant relapse was based on nodal response to NEO: 8.1% in node-negative patients, 13.9% in the downstaged group, and 22.1% in the persistently positive group (P = 0.047). Delivery of nodal irradiation decreased local recurrence in the downstaged group (12.5% versus 3.7%, P = NS). CONCLUSION: Our experience suggests that comprehensive axillary staging with ultrasound and fine-needle aspiration (FNA) and sentinel lymph node biopsy prior to NEO is both prognostically and therapeutically important in predicting those patients at higher risk of recurrence.

Digital mammography: are there advantages in screening for breast cancer?

Digital mammography separates the processes of image acquisition, processing, and display, which allows for the optimization of each process. The result addresses some of the limitations of screen film mammography. This work reviews the advantages of the decoupling of the processes and the clinical trials comparing digital mammography with film-screen mammography in the screening setting. Advanced applications of digital mammography, such as contrast-enhanced digital mammography and tomosynthesis, are also discussed.

Multi-modality 3D breast imaging with X-Ray tomosynthesis and automated ultrasound.

This study evaluated the utility of 3D automated ultrasound in conjunction with 3D digital X-Ray tomosynthesis for breast cancer detection and assessment, to better localize and characterize lesions in the breast. Tomosynthesis image volumes and automated ultrasound image volumes were acquired in the same geometry and in the same view for 27 patients. 3 MQSA certified radiologists independently reviewed the image volumes, visually correlating the images from the two modalities with in-house software. More sophisticated software was used on a smaller set of 10 cases, which enabled the radiologist to draw a 3D box around the suspicious lesion in one image set and isolate an anatomically correlated, similarly boxed region in the other modality image set. In the primary study, correlation was found to be moderately useful to the readers. In the additional study, using improved software, the median usefulness rating increased and confidence in localizing and identifying the suspicious mass increased in more than half the cases. As automated scanning and reading software techniques advance, superior results are expected.

Sentinel lymph node biopsy performed after neoadjuvant chemotherapy is accurate in patients with documented node-positive breast cancer at presentation.

BACKGROUND: The optimal strategy for incorporating lymphatic mapping and sentinel lymph node biopsy into the management of breast cancer patients receiving neoadjuvant chemotherapy remains controversial. Previous studies of sentinel node biopsy performed following neoadjuvant chemotherapy have largely reported on patients whose prechemotherapy, pathologic axillary nodal status was unknown. We report findings using a novel comprehensive approach to axillary management of node-positive-patients receiving neoadjuvant chemotherapy. METHODS: We evaluated 54 consecutive breast cancer patients with biopsy-proven axillary nodal metastases at the time of diagnosis that underwent lymphatic mapping with nodal biopsy as well as concomitant axillary lymph node dissection after receiving neoadjuvant chemotherapy. All cases were treated at a single comprehensive cancer center between 2001 and 2005. RESULTS: The sentinel node identification rate after delivery of neoadjuvant chemotherapy was 98%. Thirty-six patients (66%) had residual axillary metastases (including eight patients that had undergone resection of metastatic sentinel nodes at the time of diagnosis), and in 12 cases (31%) the residual metastatic disease was limited to the sentinel lymph node. The final, post-neoadjuvant chemotherapy sentinel node was falsely negative in three cases (8.6%). The negative final sentinel node accurately identified patients with no residual axillary disease in 17 cases (32%). CONCLUSIONS: Sentinel lymph node biopsy performed after the delivery of neoadjuvant chemotherapy in patients with documented nodal disease at presentation accurately identified cases that may have been downstaged to node-negative status and can spare this subset of patients (32%) from experiencing the morbidity of an axillary dissection.

Malignant and benign breast masses on 3D US volumetric images: effect of computer-aided diagnosis on radiologist accuracy.

PURPOSE: To retrospectively investigate the effect of using a custom-designed computer classifier on radiologists' sensitivity and specificity for discriminating malignant masses from benign masses on three-dimensional (3D) volumetric ultrasonographic (US) images, with histologic analysis serving as the reference standard. MATERIALS AND METHODS: Informed consent and institutional review board approval were obtained. Our data set contained 3D US volumetric images obtained in 101 women (average age, 51 years; age range, 25-86 years) with 101 biopsy-proved breast masses (45 benign, 56 malignant). A computer algorithm was designed to automatically delineate mass boundaries and extract features on the basis of segmented mass shapes and margins. A computer classifier was used to merge features into a malignancy score. Five experienced radiologists participated as readers. Each radiologist read cases first without computer-aided diagnosis (CAD) and immediately thereafter with CAD. Observers' malignancy rating data were analyzed with the receiver operating characteristic (ROC) curve. RESULTS: Without CAD, the five radiologists had an average area under the ROC curve (A(z)) of 0.83 (range, 0.81-0.87). With CAD, the average A(z) increased significantly (P = .006) to 0.90 (range, 0.86-0.93). When a 2% likelihood of malignancy was used as the threshold for biopsy recommendation, the average sensitivity of radiologists increased from 96% to 98% with CAD, while the average specificity for this data set decreased from 22% to 19%. If a biopsy recommendation threshold could be chosen such that sensitivity would be maintained at 96%, specificity would increase to 45% with CAD. CONCLUSION: Use of a computer algorithm may improve radiologists' accuracy in distinguishing malignant from benign breast masses on 3D US volumetric images.

Outcome of men presenting with clinical breast problems: the role of mammography and ultrasound.

The purpose of this study was to determine the outcome of men presenting with clinical breast problems for breast imaging and to evaluate the role of mammography and ultrasound in the diagnosis of benign and malignant breast problems. We retrospectively reviewed clinical, radiographic, and pathologic records of 165 consecutive symptomatic men presenting to Breast Imaging over a 4 year period. We assessed the clinical indication for referral, mammographic findings, sonographic findings, histologic results, and clinical outcomes. Patients ranged in age from 22 to 96 years. Breast Imaging Reporting and Data System (BI-RADS) category 4 and 5 mammograms and solid sonographic masses were considered suspicious for malignancy. Six of 165 men (4%) had primary breast carcinoma, which were mammographically suspicious in all 6 (100%). Five were invasive ductal carcinoma and one was ductal carcinoma in situ (DCIS). Of 164 mammograms, 20 (12%) were suspicious. Six were cancer and 14 were benign. Clinical follow-up for 2 years or biopsy results were available for 138 of the 165 men (84%). Twelve with benign mammographic findings had benign biopsies. All men with benign mammography not undergoing biopsy were cancer free. Sensitivity for cancer detection (mammography) was 100% and specificity was 90%. Positive predictive value (mammography) was 32% (6 of 19) and the negative predictive value was 100%. Sonography was performed in 68 of the 165 men (41%). Three of three cancers (100%) were solid sonographic masses. There were 9 of 68 false-positive examinations (13%). Sensitivity and negative predictive value for cancer detection (ultrasound) was 100% and specificity was 74%. The most common clinical indication for referral was mass/thickening (56%). Mammography had excellent sensitivity and specificity for breast cancer detection and should be included as the initial imaging examination of men with clinical breast problems. The negative predictive value of 100% for mammography suggests that mammograms read as normal or negative need no further examination if the clinical findings are not suspicious. A normal ultrasound in these men confirms the negative predictive value of a normal mammogram.

Breast masses: computer-aided diagnosis with serial mammograms.

PURPOSE: To retrospectively evaluate effects of computer-aided diagnosis (CAD) involving an interval change classifier (which uses interval change information extracted from prior and current mammograms and estimates a malignancy rating) on radiologists' accuracy in characterizing masses on two-view serial mammograms as malignant or benign. MATERIALS AND METHODS: The data collection protocol had institutional review board approval. Patient informed consent was waived for this HIPAA-compliant retrospective study. Ninety temporal pairs of two-view serial mammograms (depicting 47 malignant and 43 benign biopsy-proved masses) were obtained from 68 patient files and were digitized. Biopsy was the reference standard. Eight Mammography Quality Standards Act of 1992-accredited radiologists and two breast imaging fellows assessed digitized two-view temporal pairs (in preselected regions of interest only) by estimating likelihood of malignancy and Breast Imaging Reporting and Data System (BI-RADS) category without and with CAD. Observers' rating data were analyzed with Dorfman-Berbaum-Metz (DBM) multireader multicase method. Statistical significance of differences was estimated with the DBM method and Student two-tailed paired t test. RESULTS: Average area under the receiver operating characteristic curve for likelihood of malignancy across the 10 observers was 0.83 (range, 0.74-0.88) without CAD and improved to 0.87 (range, 0.80-0.92) with CAD (P < .05). The average partial area index above a sensitivity of 0.90 for likelihood of malignancy was 0.35 (range, 0.13-0.54) without CAD and 0.49 (range, 0.18-0.73) with CAD--a nonsignificant improvement (P = .11). For BI-RADS assessment, it was estimated that with CAD, six radiologists would correctly recommend additional biopsies for malignant masses (range, 4.3%-10.6%) and five would correctly recommend reduction of biopsy (ie, fewer biopsies) for benign masses (range, 2.3%-9.3%). However, five radiologists would incorrectly recommend additional biopsy for benign masses (range, 2.3%-14.0%), and one would incorrectly recommend reduction of biopsy (4.3%). CONCLUSION: CAD involving interval change analysis of preselected regions of interest can significantly improve radiologists' accuracy in classifying masses on digitized screen-film mammograms as malignant or benign.

Lobular carcinoma in situ or atypical lobular hyperplasia at core-needle biopsy: is excisional biopsy necessary?

PURPOSE: To retrospectively determine frequency of invasive cancer or ductal carcinoma in situ (DCIS) at excisional biopsy in women with atypical lobular hyperplasia (ALH) or lobular carcinoma in situ (LCIS) at percutaneous core-needle biopsy (CNB). MATERIALS AND METHODS: Review of results in 6,081 consecutive patients who underwent CNB at two institutions revealed that in 35 (0.58%), LCIS (n = 15) or ALH (n = 20) was the pathologic finding with highest risk. Patient age range was 41-84 years (mean, 59 years). Of 35 patients, 26 (74%) underwent excisional biopsy and nine (26%) underwent mammographic follow-up for longer than 2 years. Lesions with a pathologic upgrade were noted when invasive cancer or DCIS occurred at the CNB site. CNB results in patients with a diagnosis of atypical ductal hyperplasia (ADH) (75 of 6,081 [1.2%]) were reviewed; these patients underwent subsequent excisional biopsy. Statistical comparison of frequency of upgrading of lesions in patients with a diagnosis of LCIS or ALH at CNB and in those with a diagnosis of ADH at CNB was performed (Pearson chi(2) test). RESULTS: In six (17%) of 35 (95% CI: 4.7%, 29.6%) patients, lesions were upgraded to DCIS (n = 4) or invasive cancer (n = 2). In 15 patients with LCIS diagnosed at CNB, lesions in four (27%) were upgraded to either DCIS or invasive cancer. In 20 patients with ALH diagnosed at CNB, lesions were upgraded to DCIS in two (10%). Lesions in nine patients who underwent mammographic follow-up were stable. No mammographic or technical findings distinguished patients with upgraded lesions from those whose lesions were not upgraded. In 12 (16%) of 75 (95% CI: 7.7%, 24.3%) patients with ADH, lesions were upgraded. Difference between the upgrade rate in patients with LCIS or ALH and that in those with ADH was not significant (P =.88). CONCLUSION: Lesions in 17% of patients with LCIS or ALH at CNB were upgraded to invasive cancer or DCIS; this rate was similar to the upgrade rate in patients with ADH. Excisional biopsy is supported when LCIS, ALH, or ADH is diagnosed at CNB.