Does Dose Volume Histogram of Parotid Glands Correlate with Xerostomia Radiation Therapy Oncology Group Scores in Locoregionally Advanced Head and Neck Cancer Patients Treated with Intensity-Modulated Radiation Therapy?

Introduction Xerostomia is an imminent complication of head and neck radiotherapy best assessed subjectively. This study aimed to evaluate the effects of sparing parotid glands with intensity-modulated radiation therapy (IMRT) on subjective xerostomia scores in patients with locoregionally advanced head and neck cancer. Subjects and Methods This is a prospective longitudinal study conducted in an outpatient department setting. A total of 43 patients with head and neck cancer were planned with IMRT as per the ICRU 62 (International Commission on Radiation Units and Measurement Report 62). The constraints to ipsilateral and contralateral parotid glands were 35 and 25 Gy, respectively. Treatment plan was assessed for doses to 100, 67, 50, and 33% volume of individual parotid glands. Patients were subjectively assessed using the Amosson’s Questionnaire and graded as per Eisbruch’s xerostomia Radiation Therapy Oncology Group scores. Dose volume histogram (DVH) was plotted and correlated with grades of xerostomia postradiation at 1, 3, 6, 9 and 12 months follow-ups. Statistical analysis was performed suing SPSS version 16, chi-square test, and one-way analysis of variance test. Results No statistically significant correlation between mean dose of radiation, volume of the parotid glands, and grades of xerostomia was noted postradiation. A statistically significant improvement in grades of xerostomia between 3 and 6 months (p = 0.0), 3 and 9 months (p = 0.020), 6 and 9 months (p = 0.009), 6 and 12 months (p = 0.05), and 9 and 12 months (p = 0.00) was noted. Recovery in grades was noted at 9 months. Conclusion There is no statistically significant direct correlation between DVH of the parotid glands and grades of xerostomia, although recovery in grades was statistically significant at 9 months

Design of Efficient Lightweight Strategies to Combat DoS Attack in Delay Tolerant Network Routing

Delay tolerant networks (DTNs) are characterized by delay and intermittent connectivity. Satisfactory network functioning in a DTN relies heavily on co-ordination among participating nodes. However, in practice, such co-ordination cannot be taken for granted due to possible misbehaviour by relay nodes. Routing in a DTN is, therefore, vulnerable to various attacks, which adversely affect network performance. Several strategies have been proposed in the literature to alleviate such vulnerabilities—they vary widely in terms of throughput, detection time, overhead etc. One key challenge is to arrive at a tradeoff between detection time and overhead. We observe that the existing table-based reactive strategies to combat Denial-of-service (DoS) attacks in DTN suffer from two major drawbacks: high overhead and slow detection. In this paper, we propose three secure, light-weight and time-efficient routing algorithms for detecting DoS attacks (Blackhole and Grey-hole attacks) in the Spray & Focus routing protocol. The proposed algorithms are based on use of a small fraction of privileged (trusted) nodes. The first strategy, called TN, outperforms the existing table-based strategy with 20—30 % lesser detection time, 20—25 % higher malicious node detection and negligible overhead. The other two strategies, CTN_MI and CTN_RF explore the novel idea that trusted nodes are able to utilize each others\u27 information/experience using their long range connectivity as and when available. Simulations performed using an enhanced ONE simulator reveals that investing in enabling connectivity among trusted nodes (as in CTN_RF) can have significant performance benefits