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Purpose. The aim of this study was to compare diffusion-weighted magnetic resonance imaging (DWI) with computed tomography perfusion (CTP) for preoperative detection of metastases to lymph nodes (LNs) in head and neck squamous cell carcinoma (SCC). Methods. Between May 2010 and April 2012, 30 patients with head and neck SCC underwent preoperative DWI and CTP. Two radiologists measured apparent diffusion coefficient (ADC) values and CTP parameters independently. Surgery and histopathologic examinations were performed on all patients. Results. On DWI, 65 LNs were detected in 30 patients. The mean ADC value of metastatic nodes was lower than benign nodes and the difference was statistically significant (P < 0.05). On CTP images, the mean value in metastatic nodes of blood flow (BF) and blood volume (BV) was higher than that in benign nodes, and mean transit time (MTT) in metastatic nodes was lower than that in benign nodes. There were significant differences in BF and MTT values between metastatic and benign LNs (P < 0.05). There were significant differences between the AUCs of DWI and CTP (Z=4.612, P < 0.001). Conclusion. DWI with ADC value measurements may be more accurate than CTP for the preoperative diagnosis of cervical LN metastases.

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Information reconciliation is a significant step for a continuous-variable quantum key distribution (CV-QKD) system. We propose a reconciliation method that allows two authorized parties to extract a consistent and secure binary key in a CV-QKD protocol, which is based on Gaussian-modulated coherent states and homodyne detection. This method named spherical reconciliation is based on spherical quantization and non-binary low-density parity-check (LDPC) codes. With the suitable signal-to-noise ratio (SNR) and code rate of non-binary LDPC codes, spherical reconciliation algorithm has a high efficiency and can extend the transmission distance of CV-QKD.

To provide quality-of-service (QoS) differentiation and guarantee user fairness, efficient power and spectrum utilization for the downlink multiuser orthogonal frequency-division multiplexing (MU-OFDM) systems, a novel QoS guaranteed cross-layer (QGCL) scheduling scheme is proposed in this paper. The scheme formulates the scheduling into an optimization problem of overall system utility under the system constraints. Moreover, we propose a simple and efficient binary constrained particle swarm optimization (PSO) to solve the scheduling more effectively. Comparing with the classical methods, simulation results show that the proposed QGCL scheduling scheme can significantly maximize the system throughput given that the fulfillment of the QoS requirements as well as the fairness is guaranteed.