Dedicated breast CT: geometric design considerations to maximize posterior breast coverage.

An Institutional Review Board-approved protocol was used to quantify breast tissue inclusion in 52 women, under conditions simulating both craniocaudal (CC) and mediolateral oblique (MLO) views in mammography, dedicated breast CT in the upright subject position, and dedicated breast CT in the prone subject position. Using skin as a surrogate for the underlying breast tissue, the posterior aspect of the breast that is aligned with the chest-wall edge of the breast support in a screen-film mammography system was marked with the study participants positioned for CC and MLO views. The union of skin marks with the study participants positioned for CC and MLO views was considered to represent chest-wall tissue available for imaging with mammography and served as the reference standard. For breast CT, a prone stereotactic breast biopsy unit and a custom-fabricated barrier were used to simulate conditions during prone and upright breast CT, respectively. For the same breast marked on the mammography system, skin marks were made along the breast periphery that was just anterior to the apertures of the prone biopsy unit and the upright barrier. The differences in skin marks between subject positioning simulating breast CT (prone, upright) and mammography were quantified at six anatomic locations. For each location, at least one study participant had a skin mark from breast CT (prone, upright) posterior to mammography. However for all study participants, there was at least one anatomic location where the skin mark from mammography was posterior to that from breast CT (prone, upright) positioning. The maximum amount by which the skin mark from mammography was posterior to breast CT (prone and upright) over all six locations was quantified for each study participant and pair-wise comparison did not exhibit statistically significant difference between prone and upright breast CT (paired t- test, p = 0.4). Quantitatively, for 95% of the study participants the skin mark from mammography was posterior to breast CT (prone or upright) by at the most 9 mm over all six locations. Based on the study observations, geometric design considerations targeting chest-wall coverage with breast CT equivalent to mammography, wherein part of the x-ray beam images through the swale during breast CT are provided. Assuming subjects can extend their chest in to a swale, the optimal swale-depth required to achieve equivalent coverage with breast CT images as mammograms for 95% of the subjects varies in the range of ~30-50 mm for clinical prototypes and was dependent on the system geometry.

Diagnostic performance of a dedicated 1.5-T breast MR imaging system.

PURPOSE: To assess diagnostic performance of dedicated breast magnetic resonance (MR) imaging at breast imaging centers by using a dedicated 1.5-T breast MR system that used high-spatial-resolution, high-contrast-resolution spiral trajectory acquisitions. MATERIALS AND METHODS: The study was institutional review board approved and HIPAA compliant, with waiver of informed consent. Diagnostic performance was retrospectively assessed for 934 consecutive screening (n=347) and diagnostic (n=587) examinations performed from April 2006 to December 2007 in women aged 25-89 years old from four sites for which dedicated breast MR imaging reports and ground truth (biopsy for cancer cases, 1-year follow-up with negative results for cases with negative findings) were available. The sensitivity, specificity, and receiver operating characteristic (ROC) for breast MR imaging were determined. RESULTS: The sensitivity and specificity for the dedicated breast MR imaging system were 92% (92 of 100) and 88.8% (741 of 834). For all cases, the negative predictive value (NPV) was 98.9% (741 of 749). The NPV for screening cases was 100% (326 of 326). The area under the ROC curve was 0.942. Of the 93 cases with false-positive findings seen at dedicated breast MR imaging, 25 (27%) were high-risk histologic findings for which excision is often recommended. The false-positive rate was 93 of 834 (11.2%) for all cases, but only 16 of 326 (4.9%) for the screening cohort. CONCLUSION: High accuracy was achieved by using dedicated breast MR imaging.

Clinical comparison of full-field digital mammography and screen-film mammography for detection of breast cancer.

OBJECTIVE: The purpose of this work is to compare full-field digital mammography and screen-film mammography for the detection of breast cancer in a screening population. SUBJECTS AND METHODS: Full-field digital mammography was performed in addition to screen-film mammography in 6736 examinations of women 40 years old and older presenting for screening mammography at either of two institutions. Two views of each breast were acquired with each technique. The digital and screen-film mammograms were each interpreted independently. In addition to a clinical assessment, each finding was assigned a probability of malignancy for use in receiver operating characteristic analysis. In cases in which the digital and screen-film interpretations differed, a side-by-side analysis was performed to determine the reasons for the discrepancy. With few exceptions, findings detected on either technique were evaluated with additional imaging and, if warranted, biopsy. RESULTS: Additional evaluation was recommended on at least one technique in 1467 cases. These additional evaluations led to 181 biopsies and the detection of 42 cancers. Nine cancers were detected only on digital mammography, 15 were detected only on screen-film mammography, and 18 were detected on both. The difference in cancer detection is not statistically significant (p > 0.1). Digital mammography resulted in fewer recalls than did screenfilm mammography (799 vs 1007, p < 0.001). The difference between the receiver operating characteristic curve area for digital (0.74) and screen-film (0.80) mammography was not significant (p > 0.1). Reasons for discrepant interpretations of cancer were approximately equally distributed among those relating to lesion conspicuity, lesion appearance, and interpretation. CONCLUSION: No significant difference in cancer detection was observed between digital mammography and screen-film mammography. Digital mammography resulted in fewer recalls than did screen-film mammography.