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For the first time, we experimentally demonstrate ultra-low-loss guiding in bi-periodic photonic crystal waveguides over a large bandwidth of more than 60 nm. In such bi-periodic waveguides, we achieve a propagation loss very similar to that of a dielectric ridge waveguide, which indicates that the dominant loss mechanism in these bi-periodic waveguides is due to fabrication imperfections. [ABSTRACT FROM AUTHOR]

Purpose: Radiotherapy is a well-established treatment option for bone metastases. One of the commonly associated toxicities is pain flare, which can be broadly defined as a transient increase in pain during or immediately post-treatment. Previously published data indicates that incidence rates can be as high as 40% with conventional radiotherapy. With the emergence of stereotactic body radiotherapy (SBRT) as a high-dose alternative for spinal metastases, there is a need to define the pain flare phenomenon within this setting. The purpose of this prospective toxicity study was to determine the incidence rate of pain flare for SBRT of spinal metastases. Methods: From February 2010 to April 2012,41 patients were enrolled in this study. Pain scores were evaluated using the Brief Pain Inventory (BPI) before, during and 10 days after radiotherapy. Both analgesic and corticosteroid use was also documented. Pain flare was defined as per published criteria (i.e. two-point increase in worst pain on an 11-point numeric scale compared to baseline with no decrease in analgesic use, or 25% increase in analgesic intake with no decrease in worst pain score). The definition was slightly modified such that pain flare was also recorded if corticosteroids were initiated. Predictive factors were evaluated using univariate and multivariate logistic regression analysis. Results: Within this cohort, the mean (SD) age was 57.5 (12.4) years old with a median (range) KPS score of 80 (50-100). The most common primary sites were renal (36.6%), lung (24.4%) and breast (17.1%). The incidence of pain flare was 68.3% (28/41). The most common day of occurrence was day 1 post-radiotherapy (28.6%; 8/28). On multivariate logistic regression analysis, higher KPS (p=0.0174) and cervical (p=0.0498) or lumbar (p=0.0176) spine involvement were the factors significantly associated with pain flare. No association was noted for baseline pain scores, dose-fractionation schedule used or subsequent dosimetric data. Conclusions: With SBRT for spinal metastases, the incidence of pain flare was much higher than what would be expected for conventional radiotherapy. Our practice now is to offer prophylactic dexamethasone to all patients undergoing spine treatment. If validated with a larger cohort though, it may be possible to identify a high-risk subgroup that would allow for further individualization of care. At this time, this study represents the first attempt at characterizing pain flare secondary to spinal SBRT, the importance of which will only be underscored as its utility increases. Disclosure: No significant relationships. [ABSTRACT FROM AUTHOR]