Diagnosis of coronary stenosis with CT angiography comparison of automated computer diagnosis with expert readings.

RATIONALE AND OBJECTIVES: To compare computer-generated interpretation of coronary computed tomography angiography (cCTA) by commercially available COR Analyzer software with expert human interpretation. MATERIALS AND METHODS: This retrospective Health Insurance Portability and Accountability Act‑compliant study was approved by the institutional review board. Among 225 consecutive cCTA examinations, 207 were of adequate quality for automated evaluation. COR Analyzer interpretation was compared to human expert interpretation for detection of stenosis defined as ≥50% vessel diameter reduction in the left main, left anterior descending (LAD), circumflex (LCX), right coronary artery (RCA), or a branch vessel (diagonal, ramus, obtuse marginal, or posterior descending artery). RESULTS: Among 207 cases evaluated by COR Analyzer, human expert interpretation identified 48 patients with stenosis. COR Analyzer identified 44/48 patients (sensitivity 92%) with a specificity of 70%, a negative predictive value of 97% and a positive predictive value of 48%. COR Analyzer agreed with the expert interpretation in 75% of patients. With respect to individual segments, COR Analyzer detected 9/10 left main lesions, 33/34 LAD lesions, 14/15 LCX lesions, 27/31 RCA lesions, and 8/11 branch lesions. False-positive interpretations were localized to the left main (n = 16), LAD (n = 26), LCX (n = 21), RCA (n = 21), and branch vessels (n = 23), and were related predominantly to calcified vessels, blurred vessels, misidentification of vessels and myocardial bridges. CONCLUSIONS: Automated computer interpretation of cCTA with COR Analyzer provides high negative predictive value for the diagnosis of coronary disease in major coronary arteries as well as first-order arterial branches. False-positive automated interpretations are related to anatomic and image quality considerations

Characterization and Normal Measurements of the Left Ventricular Outflow Tract by ECG-gated Cardiac CT: Implications for Disorders of the Outflow Tract and Aortic Valve.

RATIONALE AND OBJECTIVES: Studies suggest that electrocardiographically gated coronary computed tomographic angiography provides a clear definition of the left ventricular outflow tract (LVOT), and normal LVOT morphology may not be round, as assumed when the continuity equation is applied during echocardiography. The aims of this study were to demonstrate the morphology of the LVOT on coronary computed tomographic angiography and to establish normal values for LVOT measurements. MATERIALS AND METHODS: Two independent readers retrospectively measured anterior-posterior (AP) and transverse diameters of the LVOT and performed LVOT planimetry on coronary computed tomographic angiographic studies of 106 consecutive patients with normal aortic valves. RESULTS: Excellent interobserver agreement was observed for all measurements (r = 0.78-0.94). The LVOT was ovoid, with a larger transverse diameter than AP diameter during diastole and systole (P \u3c .001). However, the ratio of AP diameter to transverse diameter was closer to 1.0 during systole (P \u3c .001). Mean indexed LVOT area was minimally larger in systole than in diastole (P = .01-.04) and was larger in men than in women during diastole (P ≤ .001) and systole (P ≤ .01). Mean LVOT area indexed to body surface area was 2.3 ± 0.5 cm(2)/m(2) in women and 2.6 ± 0.7 cm(2)/m(2) in men. LVOT area demonstrated significant correlation with aortic root diameter. CONCLUSIONS: The normal LVOT is ovoid in shape. LVOT is more circular during systole, but the AP diameter remains smaller than the transverse diameter throughout the cardiac cycle. The oval shape of the LVOT has important implications when LVOT area is calculated from LVOT diameters. Normal LVOT area values established in this study should facilitate diagnosis of the fixed component of LVOT obstruction

Toward Expressive and Scalable Sponsored Search Auctions

Internet search results are a growing and highly profitable advertising platform. Search providers auction advertising slots to advertisers on their search result pages. Due to the high volume of searches and the users' low tolerance for search result latency, it is imperative to resolve these auctions fast. Current approaches restrict the expressiveness of bids in order to achieve fast winner determination, which is the problem of allocating slots to advertisers so as to maximize the expected revenue given the advertisers' bids. The goal of our work is to permit more expressive bidding, thus allowing advertisers to achieve complex advertising goals, while still providing fast and scalable techniques for winner determination.Comment: 10 pages, 13 figures, ICDE 200

Decision analytic model for evaluation of suspected coronary disease with stress testing and coronary CT angiography.

RATIONALE AND OBJECTIVES: The aim of this study was to apply a decision analytic model for the evaluation of coronary artery disease (CAD) to define the optimal utilization of coronary computed tomographic angiography (cCTA) and stress testing. MATERIALS AND METHODS: The model tested in this study assumes that CAD is evaluated with a stress test and/or cCTA and that a patient with positive evaluation results undergoes cardiac catheterization. On the basis of values of sensitivity, specificity, and radiation dose from the published literature and test costs from the Medicare fee schedule, a decision tree model was constructed as a function of disease prevalence. RESULTS: The false-negative rate is lowest when cCTA is used as an isolated test. The false-positive rate is minimized when cCTA is used in combination with stress echocardiography. Effective radiation is minimized by use of stress electrocardiography or stress echocardiography alone or prior to cCTA. When the pretest probability of CAD is low, a strategy that uses stress echocardiography followed by cCTA minimizes the false-positive rate and effective radiation exposure, with relatively low imaging costs and with a false-negative rate only slightly higher than a strategy including stress myocardial scintigraphy. As the pretest probability of CAD increases above 20%, the false-negative rate of stress echocardiography followed by cCTA increases by \u3e5% relative to cCTA alone. CONCLUSION: Effective radiation dose and imaging costs for the workup of CAD may be minimized by an appropriate combination of stress testing and cCTA. A strategy that uses stress echocardiography followed by cCTA is most appropriate for the evaluation of low-risk patients with CAD with a pretest probability \u3c 20%, while cCTA alone may be more appropriate in intermediate-risk patients

Hearing in the mind\u27s ear: A PET investigation of musical imagery and perception

Neuropsychological studies have suggested that imagery processes may be mediated by neuronal mechanisms similar to those used in perception. To test this hypothesis, and to explore the neural basis for song imagery, 12 normal subjects were scanned using the water bolus method to measure cerebral blood flow (CBF) during the performance of three tasks. In the control condition subjects saw pairs of words on each trial and judged which word was longer. In the perceptual condition subjects also viewed pairs of words, this time drawn from a familiar song; simultaneously they heard the corresponding song, and their task was to judge the change in pitch of the two cued words within the song. In the imagery condition, subjects performed precisely the same judgment as in the perceptual condition, but with no auditory input. Thus, to perform the imagery task correctly an internal auditory representation must be accessed. Paired-image subtraction of the resulting pattern of CBF, together with matched MRI for anatomical localization, revealed that both perceptual and imagery. tasks produced similar patterns of CBF changes, as compared to the control condition, in keeping with the hypothesis. More specifically, both perceiving and imagining songs are associated with bilateral neuronal activity in the secondary auditory cortices, suggesting that processes within these regions underlie the phenomenological impression of imagined sounds. Other CBF foci elicited in both tasks include areas in the left and right frontal lobes and in the left parietal lobe, as well as the supplementary motor area. This latter region implicates covert vocalization as one component of musical imagery. Direct comparison of imagery and perceptual tasks revealed CBF increases in the inferior frontal polar cortex and right thalamus. We speculate that this network of regions may be specifically associated with retrieval and/or generation of auditory information from memory

Is Hey Jude in the Right Key? Cognitive Components of Absolute Pitch Memory

Most individuals, regardless of formal musical training, have long-term absolute pitch memory (APM) for familiar musical recordings, though with varying levels of accuracy. The present study followed up on recent evidence suggesting an association between singing accuracy and APM (Halpern & Pfordresher, 2022, Attention, Perception, & Psychophysics, 84(1), 260–269), as well as tonal short-term memory (STM) and APM (Van Hedger et al., 2018, Quarterly Journal of Experimental Psychology, 71(4), 879–891). Participants from three research sites (n = 108) completed a battery of tasks including APM, tonal STM, singing accuracy, and self-reported auditory imagery. Both tonal STM and singing accuracy predicted APM, replicating prior results. Tonal STM also predicted singing accuracy, music training, and auditory imagery. Further tests suggested that the association between APM and singing accuracy was fully mediated by tonal STM. This pattern comports well with models of vocal pitch matching that include STM for pitch as a mechanism for sensorimotor translation

New Algorithm for Mixmaster Dynamics

We present a new numerical algorithm for evolving the Mixmaster spacetimes. By using symplectic integration techniques to take advantage of the exact Taub solution for the scattering between asymptotic Kasner regimes, we evolve these spacetimes with higher accuracy using much larger time steps than previously possible. The longer Mixmaster evolution thus allowed enables detailed comparison with the Belinskii, Khalatnikov, Lifshitz (BKL) approximate Mixmaster dynamics. In particular, we show that errors between the BKL prediction and the measured parameters early in the simulation can be eliminated by relaxing the BKL assumptions to yield an improved map. The improved map has different predictions for vacuum Bianchi Type IX and magnetic Bianchi Type VI$_0$ Mixmaster models which are clearly matched in the simulation.Comment: 12 pages, Revtex, 4 eps figure

Mastering the Master Field

The basic concepts of non-commutative probability theory are reviewed and applied to the large $N$ limit of matrix models. We argue that this is the appropriate framework for constructing the master field in terms of which large $N$ theories can be written. We explicitly construct the master field in a number of cases including QCD$_2$. There we both give an explicit construction of the master gauge field and construct master loop operators as well. Most important we extend these techniques to deal with the general matrix model, in which the matrices do not have independent distributions and are coupled. We can thus construct the master field for any matrix model, in a well defined Hilbert space, generated by a collection of creation and annihilation operators---one for each matrix variable---satisfying the Cuntz algebra. We also discuss the equations of motion obeyed by the master field.Comment: 46 pages plus 11 uuencoded eps figure