BI-RADS 3 (short-interval follow-up) assessment rate at diagnostic mammography: Correlation with recall rates and utilization as a performance benchmark.

The purpose of this study was to identify a correlation between the screening BI-RADS 0 (recall) rates and diagnostic BI-RADS 3 (short-interval follow-up) rates of individual interpreting radiologists, with the goal of utilizing the BI-RADS 3 rate as an acceptable performance metric in the diagnostic population. A multicenter retrospective analysis of medical audit statistics was conducted on annual radiologist performance data collected over a 14-year period in a community hospital-based practice. Mixed regression models were used to estimate the association between screening BI-RADS 0 and diagnostic BI-RADS 3 examinations while adjusting for calendar year, annual radiologist screening volume, annual radiologist diagnostic volume, and diagnostic examination indication. A moderate statistically significant positive correlation was established between the screening BI-RADS 0 rates and Diagnostic BI-RADS 3 rates (Pearson correlation coefficient + 0.349, P ≤ .001). Furthermore, when utilizing a national benchmark range of 8%-12% as an acceptable BI-RADS 0 rate within a screening population, the correlative BI-RADS 3 assessment rate was demonstrated to be approximately 16%. We propose that this BI-RADS category 3 rate may represent an additional acceptable performance metric in the diagnostic population. Routine inclusion of an interpreting mammographer's diagnostic BI-RADS 3 rate in the annual medical audit may help reduce inappropriate and/or excess use of the BI-RADS 3 category, which may lead to significant potential reductions in follow-up examinations with their associated healthcare-related costs, resource expenditure, and induced patient anxiety.

Topological RPdBi half-Heusler semimetals: A new family of noncentrosymmetric magnetic superconductors.

We report superconductivity and magnetism in a new family of topological semimetals, the ternary half-Heusler compound RPdBi (R: rare earth). In this series, tuning of the rare earth f-electron component allows for simultaneous control of both lattice density via lanthanide contraction and the strength of magnetic interaction via de Gennes scaling, allowing for a unique tuning of the normal-state band inversion strength, superconducting pairing, and magnetically ordered ground states. Antiferromagnetism with ordering vector (½,½,½) occurs below a Néel temperature that scales with de Gennes factor dG, whereas a superconducting transition is simultaneously supressed with increasing dG. With superconductivity appearing in a system with noncentrosymmetric crystallographic symmetry, the possibility of spin-triplet Cooper pairing with nontrivial topology analogous to that predicted for the normal-state electronic structure provides a unique and rich opportunity to realize both predicted and new exotic excitations in topological materials.

2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe3O4.

When electroactive nanomaterials are fully incorporated into an electrode structure, characterization of the crystallite sizes, agglomerate sizes, and dispersion of the electroactive materials can lend insight into the complex electrochemistry associated with composite electrodes. In this study, composite magnetite electrodes were sectioned using ultramicrotome techniques, which facilitated the direct observation of crystallites and agglomerates of magnetite (Fe3O4) as well as their dispersal patterns in large representative sections of electrode, via 2D cross sectional analysis by Transmission Electron Microscopy (TEM). Further, the electrochemistry of these electrodes were recorded, and Transmission X-ray Microscopy (TXM) was used to determine the distribution of oxidation states of the reduced magnetite. Unexpectedly, while two crystallite sizes of magnetite were employed in the production of the composite electrodes, the magnetite agglomerate sizes and degrees of dispersion in the two composite electrodes were similar to each other. This observation illustrates the necessity for careful characterization of composite electrodes, in order to understand the effects of crystallite size, agglomerate size, and level of dispersion on electrochemistry.

Electrochemical reduction of an Ag2VO2PO4 particle: dramatic increase of local electronic conductivity.

Previously, we reported that electrodes containing silver vanadium phosphate (Ag2VO2PO4) powder exhibit a 15,000 fold increase in conductivity after discharge, concurrent with the formation of silver metal. In this study, in order to disentangle the complex nature of electrodes composed of electroactive powders, an electrochemical reduction of individual particles of Ag2VO2PO4 was conducted, to more directly probe the intrinsic materials properties of Ag2VO2PO4. Specifically, individual particle conductivity data from a nanoprobe system combined with SEM and optical imaging results revealed that the depth of discharge within an Ag2VO2PO4 particle is closely linked to the conductivity increase. Notably, the formation of silver metal may affect both inter- and intraparticle conductivity of the Ag2VO2PO4 material.

Synthetic control of composition and crystallite size of silver ferrite composites: profound electrochemistry impacts.

A paradigm for concomitant control of crystallite size and composition of bimetallic composites via co-precipitation is introduced. Direct preparation of composites of silver ferrite and amorphous maghemite via nonstoichiometric synthesis was demonstrated. Notable impact on electrochemistry was observed, with ∼200% increase in reversible capacity for the small crystallite material.

Batteries. In situ visualization of Li/Ag2VP2O8 batteries revealing rate-dependent discharge mechanism.

The functional capacity of a battery is observed to decrease, often quite dramatically, as discharge rate demands increase. These capacity losses have been attributed to limited ion access and low electrical conductivity, resulting in incomplete electrode use. A strategy to improve electronic conductivity is the design of bimetallic materials that generate a silver matrix in situ during cathode reduction. Ex situ x-ray absorption spectroscopy coupled with in situ energy-dispersive x-ray diffraction measurements on intact lithium/silver vanadium diphosphate (Li/Ag2VP2O8) electrochemical cells demonstrate that the metal center preferentially reduced and its location in the bimetallic cathode are rate-dependent, affecting cell impedance. This work illustrates that spatial imaging as a function of discharge rate can provide needed insights toward improving realizable capacity of bimetallic cathode systems.

In situ profiling of lithium/Ag2VP2O8 primary batteries using energy dispersive X-ray diffraction.

In situ, in operando characterization of electrochemical cells can provide insight into the complex discharge chemistries of batteries which may not be available with destructive methods. In this study, in situ energy-dispersive X-ray spectroscopy (EDXRD) measurements are conducted for the first time on active lithium/silver vanadium diphosphate, Li/Ag2VP2O8, electrochemical cells at several depths of discharge allowing depth profiling analysis of the reduction process. This technique enables non-destructive, in operando imaging of the reduction process within a battery electrode over a millimeter scale interrogation area with micron scale resolution. The discharge of Ag2VP2O8 progresses via a reduction displacement reaction forming conductive silver metal as a discharge product, a high Z material which can be readily detected by diffraction-based methods. The high energy X-ray capabilities of NSLS beamline X17B1 allowed spatially resolved detection of the reduction products forming conductive pathways providing insight into the discharge mechanism of Ag2VP2O8.

Pressure-induced unconventional superconducting phase in the topological insulator Bi2Se3.

Simultaneous low-temperature electrical resistivity and Hall effect measurements were performed on single-crystalline Bi2Se3 under applied pressures up to 50 GPa. As a function of pressure, superconductivity is observed to onset above 11 GPa with a transition temperature Tc and upper critical field Hc2 that both increase with pressure up to 30 GPa, where they reach maximum values of 7 K and 4 T, respectively. Upon further pressure increase, Tc remains anomalously constant up to the highest achieved pressure. Conversely, the carrier concentration increases continuously with pressure, including a tenfold increase over the pressure range where Tc remains constant. Together with a quasilinear temperature dependence of Hc2 that exceeds the orbital and Pauli limits, the anomalously stagnant pressure dependence of Tc points to an unconventional pressure-induced pairing state in Bi2Se3 that is unique among the superconducting topological insulators.

Reassessing specimen number and diagnostic yield of ultrasound guided breast core biopsy.

To reassess the minimum number of specimens required for an accurate diagnosis compared to the standard acquisition of five specimens. A total of 190 consecutive breast mass biopsies were performed using a 14-gauge core biopsy needle under ultrasound guidance. Two to six specimens were obtained from each mass and placed in sequential containers. Each specimen was evaluated by a pathologist in the order it was obtained and was labeled as "diagnostic' or 'non-diagnostic'. During the biopsy procedure, the radiologist indicated after which number biopsy he was confident that an adequate diagnostic specimen had been obtained. This was based upon real-time visualization of the needle passing through the lesion and whether the specimen sank or floated in formalin. These observations were compared with the pathologic diagnostic yield according to specimen number. Fifty-eight lesions (30.5%) were malignant, four (2.1%) were atypical, and 128 (67.4%) were benign. Histologic diagnosis was obtained after the first specimen in 157 (82.6%) lesions, the second specimen in 172 (90.5%) lesions, the third specimen in 186 (97.9%) lesions, the fourth specimen in 188 (98.9%) lesions, and the fifth specimen in 190 (100%) lesions. A histologic diagnosis was made in 90% of the malignant lesions after the first biopsy pass, 95% after the second pass, 98% after the third pass, and 100% after the fourth and fifth passes. Nine (4.7%) lesions showed discrepancy between the radiologist's confidence of diagnosis and pathologic diagnostic yield. Of these lesions, seven were benign and two were malignant. A diagnostic yield of 95% was obtained based on operator estimate of the minimum number of required core biopsies. A high diagnostic yield of 98% was achieved after three biopsy passes and 100% after five passes.

Quantum critical scaling at the edge of Fermi liquid stability in a cuprate superconductor.

In the high-temperature cuprate superconductors, the pervasiveness of anomalous electronic transport properties suggests that violation of conventional Fermi liquid behavior is closely tied to superconductivity. In other classes of unconventional superconductors, atypical transport is well correlated with proximity to a quantum critical point, but the relative importance of quantum criticality in the cuprates remains uncertain. Here, we identify quantum critical scaling in the electron-doped cuprate material La(2-x)Ce(x)CuO(4) with a line of quantum critical points that surrounds the superconducting phase as a function of magnetic field and charge doping. This zero-temperature phase boundary, which delineates a metallic Fermi liquid regime from an extended non-Fermi liquid ground state, closely follows the upper critical field of the overdoped superconducting phase and gives rise to an expanse of distinct non-Fermi liquid behavior at finite temperatures. Together with signatures of two distinct flavors of quantum fluctuations, these facts suggest that quantum criticality plays a significant role in shaping the anomalous properties of the cuprate phase diagram.

Sr adatoms on As bridge positions on SrFe2As2 observed by scanning tunneling microscopy at 4.2 K.

We used a scanning tunneling microscope to image the surface of SrFe(2)As(2) single crystals at 4.2 K. We found, besides the commonly reported row structures and some disordered areas, also maze-like regions. Atomically resolved images of the maze show that the atoms on the surface sit on As bridge positions of the underlying Fe(2)As(2) layer. Examination of the corner positions within the maze-like reconstruction reveals the presence of adatoms rather than As dimers. Hence, the surface atoms on these samples are most likely to be Sr atoms.

Principal component analysis of breast DCE-MRI adjusted with a model-based method.

PURPOSE: To investigate a fast, objective, and standardized method for analyzing breast dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) applying principal component analysis (PCA) adjusted with a model-based method. MATERIALS AND METHODS: 3D gradient-echo DCE breast images of 31 malignant and 38 benign lesions, recorded on a 1.5T scanner, were retrospectively analyzed by PCA and by the model-based three-timepoints (3TP) method. RESULTS: Intensity-scaled (IS) and enhancement-scaled (ES) datasets were reduced by PCA yielding a first IS-eigenvector that captured the signal variation between fat and fibroglandular tissue; two IS-eigenvectors and the two first ES-eigenvectors captured contrast-enhanced changes, whereas the remaining eigenvectors captured predominantly noise changes. Rotation of the two contrast-related eigenvectors led to a high congruence between the projection coefficients and the 3TP parameters. The ES-eigenvectors and the rotation angle were highly reproducible across malignant lesions, enabling calculation of a general rotated eigenvector base. Receiver operating characteristic (ROC) curve analysis of the projection coefficients of the two eigenvectors indicated high sensitivity of the first rotated eigenvector to detect lesions (area under the curve [AUC] > 0.97) and of the second rotated eigenvector to differentiate malignancy from benignancy (AUC = 0.87). CONCLUSION: PCA adjusted with a model-based method provided a fast and objective computer-aided diagnostic tool for breast DCE-MRI.

D-dimers and efficacy of clinical risk estimation algorithms: sensitivity in evaluation of acute pulmonary embolism.

OBJECTIVE: The goal of this study was to test the efficacy of clinical risk algorithms and a quantitative immunoturbidimetric D-dimer assay in the evaluation of patients undergoing pulmonary CT angiography for suspected acute pulmonary embolism. SUBJECTS AND METHODS: From April 1, 2007, to March 31, 2008, emergency department evaluations for clinically suspected pulmonary embolism were performed with the revised Geneva score, a quantitative D-dimer assay, and pulmonary CT angiography. RESULTS: Evaluations for pulmonary embolism were performed for 745 consecutively registered patients, 627 of whom were included in the study. The other 118 patients were excluded because a d-dimer assay was not performed. According to the revised Geneva score, 281 patients had low clinical probability of having pulmonary embolism; 330, intermediate probability; and 16, high probability. CT angiography showed that 28 patients had pulmonary embolism (six in the low-probability group, 17 in the intermediate-probability group, and five in the high-probability group). The sensitivity, negative predictive value, and specificity of the D-dimer assay were 100%, 100%, and 25% (low-clinical-probability group); 100%, 100%, and 33% (intermediate-probability group); and 80%, 80%, and 37% (high-probability group). CONCLUSION: The data appear to support the use of a quantitative D-dimer assay as a first-line test in evaluation for pulmonary embolism when the clinical probability of the presence of pulmonary embolism is low or intermediate. The sensitivity and negative predictive value were 100% for these cases. More than 26% of CT angiographic examinations might have been avoided if the D-dimer assay had been used as a first-line test in the care of patients at low or intermediate risk. Because of the small sample size, the D-dimer assay is not recommended as a first-line test in the evaluation of patients at high risk.

CT radiographic findings: atrio-esophageal fistula after transcatheter percutaneous ablation of atrial fibrillation.

INTRODUCTION: Radio-frequency catheter ablation (RFCA) is an ever increasing modality for treating refractory atrial fibrillation. Radiologists should not only be able to interpret and convey anatomic variations of pulmonary veins and left atrium to referring electrophysiologists, but also should be aware of all the post-RFCA complications and their radiographic findings including this rare, but often fatal complication. This report describes a fatal atrio-esophageal fistula (AEF) involving a normal variant single left common pulmonary vein after transcatheter ablation. RESULTS: A 59-year-old man who presented to the Emergency Department (ED) with altered mental status previously complaining of fatigue and malaise. The patient underwent a total of 2 uneventful circumferential percutaneous pulmonary vein ablations for atrial fibrillation. The most recent was performed 5 weeks before admission to ED. Within hours of initial evaluation, the patient quickly deteriorated owing to overwhelming sepsis requiring both inotropic and ventilatory support. Transthoracic echocardiography within ED showed no evidence of valvular vegetation or gas bubbles in the left atrium. Computed tomography (CT) of the chest with intravenous contrast revealed findings compatible with AEF. Head CT was negative for ischemic changes or emboli. Patient underwent emergent cardiac and esophageal surgery at which point the patient later died on the operating table. CONCLUSIONS: Patients who present with signs and symptoms of endocarditis, and particularly with new neurologic symptom after RFCA should be promptly evaluated for AEF. In our case, radiographic findings in correlation with clinical history and high suspicion strongly suggested this rare, often fatal complication. During review of the chest CT, particular vigilance should be made to the left pulmonary vein/posterior left atrium junction at which site fistulous tracts tend to occur. Prompt diagnosis necessitates emergent cardiac and esophageal surgery to prevent rapid deterioration and death.

Magnetic resonance imaging reveals functional diversity of the vasculature in benign and malignant breast lesions.

BACKGROUND: Tumor perfusion through the microvascular network can be imaged noninvasively by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The objective of the current study was to quantify the microvascular perfusion parameters in various human breast lesions and to determine whether they varied between benign lesions and malignancy and whether they were altered with increased invasiveness. METHODS: Perfusion parameters in 22 benign fibrocystic changes, 15 ductal carcinomas in situ (DCIS), 30 infiltrating ductal carcinomas (IDC), and 22 fibroadenomas were measured using high-resolution DCE-MRI. Pixel-by-pixel image analysis yielded parametric images of two perfusion indicators: the influx transcapillary transfer constant (k(trans)) and the efflux transcapillary rate constant (k(ep)). Correlations of lesion type and perfusion parameters were calculated using Spearman correlation. Logistic regression analysis evaluated the best predictors of the kinetic parameters that differentiate between IDC and benign lesions. RESULTS: The perfusion parameters exhibited a progressive increase from benign fibrocystic changes to DCIS and IDC, with a significant correlation between lesion type and the parameters' values (range of correlation coefficients, 0.56-0.76; P < 0.0001). In addition, k(trans) increased from low-grade DCIS to high-grade DCIS. Fibroadenomas were characterized uniquely by high k(trans) but low k(ep). Stepwise logistic regression selected k(trans) as the best predictor for distinguishing benign fibrocystic changes from IDC, yielding 93% sensitivity and 96% specificity. CONCLUSIONS: The microvascular perfusion parameters in breast lesions were elevated with invasiveness. Quantification of these parameters using high-resolution DCE-MRI was helpful for differentiating between breast lesions and should improve breast carcinoma diagnosis.

Stereotactic core needle biopsy of nonpalpable breast lesions using a conventional mammography unit with an add-on device.

OBJECTIVE: The purpose of this prospective study was to assess the accuracy of an add-on stereotactic unit for core needle biopsy of mammographic lesions. SUBJECTS AND METHODS. Between September 1994 and February 2001, 506 stereotactic core needle biopsies of mammographic lesions in 492 patients were performed in our center on a mammography unit with add-on stereotactic equipment. Of the initial 92 patients, 80 underwent stereotactic core needle biopsy and surgical excision simultaneously. In subsequent cases, surgical biopsy was performed after core biopsy in patients who had malignant or atypical histologic results or discordance between mammographic and pathologic findings. Follow-up mammography was advised for all patients whose core biopsy results were diagnosed as benign lesions. RESULTS: Histologic results for 506 lesions undergoing stereotactic core needle biopsy were as follows: 113 (22.3%) were malignant; 369 (72.9%), benign; and 24 (4.7%), atypical. Of 113 malignant lesions identified at stereotactic core needle biopsy, 111 were confirmed as malignant, whereas two showed no evidence of malignancy at surgical excision. Of 369 lesions diagnosed as benign at stereotactic core needle biopsy, 172 (46.6%) showed no change on follow-up mammography, 114 (30.9%) were lost to follow-up, and 83 (22%) underwent surgical excision. Of 24 lesions with atypical histology, 23 had surgical follow-up, six were malignant, nine were benign, and eight were confirmed as showing atypical histology. Stereotactic core needle biopsy of the 506 lesions was complicated by five (1.0%) cases of vasovagal attack and four (0.8%) cases of bleeding. The resulting sensitivity, specificity, and positive and negative predictive values were 98.3%, 93.0%, 86.0%, and 99.2% respectively. CONCLUSION: Biopsy with an add-on unit is safe, reliable, accurate, and cost-effective with results comparable to those reported for dedicated prone biopsy devices.