Frequency of Malignancy and Imaging Characteristics of Probably Benign Lesions Seen at Breast MRI.

OBJECTIVE: The purposes of this study were to evaluate the frequency, follow-up compliance, and cancer rate of MRI BI-RADS category 3 lesions and to determine the cancer rate for individual BI-RADS descriptors. MATERIALS AND METHODS: A retrospective review was conducted of breast MRI examinations with an assessment of probably benign (BI-RADS category 3) from among 4279 consecutive breast MRI examinations performed from January 2005 through December 2009. The review revealed 282 (6.6%) examinations with 332 lesions defined as BI-RADS 3. Pathologic results, 2 years of follow-up imaging findings, or both were reviewed. The frequency of BI-RADS 3 assessments, follow-up imaging compliance, and cancer yield were calculated. Three fellowship-trained breast imagers reevaluated all lesions and recorded descriptors from the MRI lexicon of the fifth edition of the BI-RADS atlas. The distribution and likelihood of malignancy for each descriptor were calculated. RESULTS: The follow-up compliance rate was 84.3% (280/332), and the malignancy rate was 4.3% (12/280). There were 50 (17.9%) individual foci, 61 (21.8%) multiple foci, 74 (26.4%) masses, and 95 (33.9%) nonmass enhancement lesions. Masses were most commonly oval (59.5% [44/74]), circumscribed (75.7% [56/74]), and homogeneously enhancing (43.2% [32/74]). Nonmass enhancement was most commonly focal (57.9% [55/95]) with heterogeneous enhancement (53.7% [51/95]) Most of the lesions had persistent kinetics (74.3% [208/280]). The background parenchymal enhancement was most commonly mild (51.1% [143/280]). CONCLUSION: MRI BI-RADS category 3 is not frequently used, and the levels of patient compliance with follow-up imaging are acceptable. The cancer yield for probably benign lesions is greater for MRI-detected than for mammographically detected lesions, especially for specific BI-RADS descriptors.

Interobserver Variability Between Breast Imagers Using the Fifth Edition of the BI-RADS MRI Lexicon.

OBJECTIVE: The purpose of this study was to assess the interobserver variability of users of the MRI lexicon in the fifth edition of the BI-RADS atlas. MATERIALS AND METHODS: Three breast imaging specialists reviewed 280 routine clinical breast MRI findings reported as BI-RADS category 3. Lesions reported as BI-RADS 3 were chosen because variability in the use of BI-RADS descriptors may influence which lesions are classified as probably benign. Each blinded reader reviewed every study and recorded breast features (background parenchymal enhancement) and lesion features (lesion morphology, mass shape, mass margin, mass internal enhancement, nonmass enhancement distribution, nonmass enhancement internal enhancement, enhancement kinetics) according to the fifth edition of the BI-RADS lexicon and provided a final BI-RADS assessment. Interobserver variability was calculated for each breast and lesion feature and for the final BI-RADS assessment. RESULTS: Interobserver variability for background parenchymal enhancement was fair (ĸ = 0.28). There was moderate agreement on lesion morphology (ĸ = 0.53). For masses, there was substantial agreement on shape (ĸ = 0.72), margin (ĸ = 0.78), and internal enhancement (ĸ = 0.69). For nonmass enhancement, there was substantial agreement on distribution (ĸ = 0.69) and internal enhancement (ĸ = 0.62). There was slight agreement on lesion kinetics (ĸ = 0.19) and final BI-RADS assessment (ĸ = 0.11). CONCLUSION: There is moderate to substantial agreement on most MRI BI-RADS lesion morphology descriptors, particularly mass and nonmass enhancement features, which are important predictors of malignancy. Considerable disagreement remains, however, among experienced readers whether to follow particular findings.

The effect of posterior thoracic spine anatomical structures on motion segment flexion stiffness.

STUDY DESIGN: This in vitro human cadaveric study tested the loss of thoracic motion segment flexion stiffness after sequential posterior upper instrumented vertebra anchor placement techniques and posterior column destabilization. OBJECTIVE: This study was designed to determine the possible destabilizing effects of upper thoracic instrumentation anchor site preparation. SUMMARY OF BACKGROUND DATA: Proximal junctional kyphosis after instrumentation and arthrodesis for scoliosis and related spine deformities has recently been reported to range from 10% to 46%. The effect of posterior skeletal dissection associated with upper instrumented vertebra anchor placement on adjacent motion segment flexion stiffness has not been previously studied. METHODS.: Twenty-three intact thoracic motion segments were obtained from 6 human cadavers. Biomechanical testing was performed with each motion segment flexed to approximately 3.2 degrees at a rate of 0.1 Hz, with corresponding torques recorded. Data were collected after a series of 6 posterior procedures. Differences with P value <0.01 were considered significant and those with P value <0.05 marginally significant. RESULTS: Supratransverse process hook, supralaminar hook, pedicle screw placement, or pedicle screw removal done, bilaterally, produced similar, small (range, 2.09%-6.03%), nonsignificant reductions in motion segment flexion stiffness. But when totaled, these 4 procedures resulted in a significant 16.31% loss of flexion stiffness. The fifth procedure of supraspinous and interspinous process ligament transection added a marginally significant 6.59% incremental loss of flexion stiffness. Supralaminar hook site preparation combined with supraspinous and interspinous process ligament transection resulted in a marginally significant 12.62% incremental loss of flexion stiffness. Transection of the remaining posterior structures (facet joints and all other posterior soft tissue structures) produced a significant additional flexion stiffness loss of 44.72%. The anterior column alone provided only 32.39% of the total motion segment flexion stiffness. Transection of all posterior stabilizing structures, similar to a Smith-Peterson/chevron/Ponte resection, decreased motion segment flexion stiffness significantly, 67.61%. CONCLUSION: Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

Role of fibrillar structure of collagenous carrier in bone sialoprotein-mediated matrix mineralization and osteoblast differentiation.

To investigate the effects of the microstructure of collagenous carriers on the in vivo function of bone sialoprotein (BSP) in mineralization and osteoblast differentiation, we examined the ultrastructure of reconstituted type I collagen (collagen) and heat-denatured collagen (gelatin) and the in vivo responses to purified bone-derived BSP that was implanted with collagen or gelatin into surgically created 8-mm rat calvarial bone defects. Scanning and transmission electron microscopies revealed that the collagen displayed a fine fibrillar structure with interconnecting spaces between the fibrils/fibers, while the gelatin completely lost this unique three-dimensional structure after denaturation. The rates of in vivo release of BSP from the collagen scaffold were significantly lower than those from the gelatin. Collagen-BSP, but not gelatin-BSP, induced early mineral deposition in the matrix of proliferating repair cells in the calvarial defects at approximately 4-7 days after implantation. Expression levels of osteoblast markers, alkaline phosphatase activity and amounts of new bone synthesized in the collagen-BSP treated defects were significantly greater than that in the gelatin-BSP treated defects (p<0.001). The data suggest that the fibrillar microstructure of reconstituted collagen is essential for retaining BSP at a higher concentration within the defects, which enhances BSP-mediated matrix mineralization and osteoblast differentiation during the repair of rat calvarial defects.