The effect of surgeon's specialty and volume on the perioperative outcome of carotid endarterectomy.

BACKGROUND: Several studies have demonstrated better outcomes for carotid endarterectomy (CEA) at high-volume hospitals and providers. However, only a few studies have reported on the impact of surgeons' specialty and volume on the perioperative outcome of CEA. METHODS: This is a retrospective analysis of CEA during a recent 2-year period. Surgeons' specialties were classified according to their Board specialties into general surgeons (GS), cardiothoracic surgeons (CT), and vascular surgeons (VS). Surgeons' annual volume was categorized into low volume (<10 CEAs), medium volume (10 to <30 CEAs), and high volume (≥30 CEAs). The primary outcome was 30-day perioperative stroke and/or death; however, other perioperative complications were analyzed. Both univariate and multivariate analyses were done to predict the effect of specialty/volume and any other patient risk factors on stroke outcome. RESULTS: Nine hundred and fifty-three CEAs were performed by 24 surgeons: 122 by seven GS, 383 by 13 CT, and 448 by 4 VS. Patients' demographics/clinical characteristics were similar between specialties, except the incidence of coronary artery disease, which was higher for CT (P < .0001). The indications for CEA were symptomatic disease in 38% for VS, 31% for GS, and 23% for CT (P < .0001). The perioperative stroke and death rates were 4.1%, 2.9%, and 1.3% for GS, CT, and VS, respectively (P = .126). A subgroup analysis showed that the perioperative stroke rates for symptomatic patients were 5.3%, 2.3%, and 2.3% (P = .511) and for asymptomatic patients were 3.6%, 3%, and 0.72% (P = .099) for GS, CT, and VS, respectively. Perioperative stroke rates were significantly higher for nonvascular surgeons (GS and CT combined) vs VS in asymptomatic patients (3.2% vs 0.72%; P = .033). Perioperative stroke/death was also significantly lower for high-volume surgeons: 1.3% vs 4.1% and 4.3% for medium- and low-volume surgeons (P = .019) (1.3% vs 4.15% for high vs low/medium combined; P = .005). More CEAs were done for asymptomatic patients in the low/medium-volume surgeons (78%) vs high-volume surgeons (64%; P < .0001) with a stroke rate of 4.6% for low/medium-volume surgeons vs 0.51% for high-volume surgeons (P = .0005). A univariate logistic analysis showed that the odds ratio of having a perioperative stroke was 0.3 (95% confidence interval [CI], 0.13-0.73; P =.008) for high-volume surgeons vs low/medium-volume surgeons, 0.4 (95% CI, 0.16-1.07; P = .069) for VS vs CT/GS and 0.2 (95% CI, 0.06-0.45; P = .0004) when patching was used. A multivariate analysis showed that the odds ratio of having a perioperative stroke for CT VS was 2.1 (95% CI, 0.71-5.92; P = .183); for GS vs VS, 1.8 (95% CI, 0.49-6.90; P = .3709); for low-volume surgeons (vs high-volume) 3.4 (95% CI, 0.96-11.77; P = .0581); medium- vs high-volume surgeons 2.2 (95% CI, 0.75-6.42; P = .1509). CONCLUSIONS: High-volume surgeons had significantly better perioperative stroke/death rates for CEA than low/medium-volume surgeons. Perioperative stroke/death rates were also higher for nonvascular surgeons in asymptomatic patients.

Optically induced rotation of an exciton spin in a semiconductor quantum dot.

We demonstrate control over the spin state of a semiconductor quantum dot exciton using a polarized picosecond laser pulse slightly detuned from a biexciton resonance. The control pulse follows an earlier pulse, which generates an exciton and initializes its spin state as a coherent superposition of its two nondegenerate eigenstates. The control pulse preferentially couples one component of the exciton state to the biexciton state, thereby rotating the exciton's spin direction. We detect the rotation by measuring the polarization of the exciton spectral line as a function of the time difference between the two pulses. We show experimentally and theoretically how the angle of rotation depends on the detuning of the second pulse from the biexciton resonance.

Coherent optical writing and reading of the exciton spin state in single quantum dots.

We demonstrate a one-to-one correspondence between the polarization state of a light pulse tuned to neutral exciton resonances of single semiconductor quantum dots and the spin state of the exciton that it photogenerates. This is accomplished using two variably polarized and independently tuned picosecond laser pulses. The first "writes" the spin state of the resonantly excited exciton. The second is tuned to biexcitonic resonances, and its absorption is used to "read" the exciton spin state. The absorption of the second pulse depends on its polarization relative to the exciton spin direction. Changes in the exciton spin result in corresponding changes in the intensity of the photoluminescence from the biexciton lines which we monitor, obtaining thus a one-to-one mapping between any point on the Poincaré sphere of the light polarization to a point on the Bloch sphere of the exciton spin.

Determining the asymmetry of skin lesion with fuzzy borders.

It is highly desirable to identify malignant melanoma, a common cancer, at an early stage. One important clinical feature of this cancer is asymmetrical skin lesions. In this paper, we propose an adaptive fuzzy approach that uses symmetric distance (SD) to measure lesions with fuzzy borders. The use of a number of SD variations and the adoption of a backpropagation neural network enhances the discriminative power of the approach. Digitized images from the Lesion Clinic in Vancouver, Canada, demonstrate the accurate classification of asymmetric lesions at around 80%.