Baseline Indices Research Articles

Evaluation of Rayleigh-Corrected Reflectance on Remote Detection of Algal Blooms in Optically Complex Coasts of East China Sea

This study used GOCI-II data to systematically evaluate the feasibility of Rayleigh-corrected reflectance (Rrc) to detect algal blooms in the complex optical environment of the East China Sea (ECS). Based on long-term in situ remote sensing reflectance (Rrs), Rrc spectra demonstrated the similar capability of reflecting the water condition under various atmospheric conditions, and the baseline indices (BLIs) derived from Rrc and Rrs showed good consistency (R2 > 0.98). The effectiveness of five Rrc-based BLIs (SS490, CI, DI, FLH, and MCI) for algal bloom detection was assessed, among which SS490 and MCI showed better performances. A synthetic bloom detection algorithm based on the BLIs of Rrc was then developed to avoid the impact of turbid water. The validation of the BLI algorithm was carried out based on the in situ algal abundance data from 2021 to 2023. Specifically, SS490 showed the best bloom detection result (F-measure coefficient, FM = 0.97), followed by MCI (FM = 0.88). Since the 709 nm bands used in MCI were missing in many ocean color satellites, the SS490 algorithm was more useful in application. Compared to Rrs based bloom detection algorithms, synthetical Rrc BLI proposed in this paper provides more effective observation results and even better algal bloom detection performance. In conclusion, the study confirmed the feasibility of utilizing Rrc for algal bloom detection in the coastal areas of the ECS, and recognized the satisfactory performance of synthetical SS490 by comparing with the other BLIs.

Utility of serial Doppler ultrasound scans for the diagnosis of acute rejection in renal allografts.

This study aims to explore the utility of serial duplex scanning and to compare its results with those of single time-point scans of renal allografts in the diagnosis of acute rejection (AR). A retrospective analysis of 6017 serial duplex scans (mean: 9.8 scans per patient, 5.7 of which were done during the first 10 days) was performed in 614 patients with 462 episodes of AR from 1992-2000. Even in the absence of AR (n=278), there were day-to-day fluctuations in pulsatility index (PI) and resistive index (RI). An increase of >10% in intra-renal indices was noted 0.95 days (mean) before the commencement of treatment for AR (SD 1.3, range 1-6 days). In patients with acute tubular necrosis (ATN), who have high base line indices, sensitivity of single value of PI and RI was 58% (cut-off level 1.8) and 68% (cut-off level 0.8), with specificity of 66% and 56%, respectively. By contrast, a >10% increase over the previous 'best' in PI and RI had a sensitivity of 78% and 60% respectively, and a specificity of 78% and 90%, respectively. Reversal of flow during diastole (n=50) was found to be associated with 22% graft loss within 3 months of transplantation. We can conclude that a considerable overlap between the indices of patients with AR and those with ATN greatly limits the diagnostic yield of duplex scanning. Nonetheless, serial scanning of renal allografts is more likely to herald the need for biopsy in the diagnosis of AR than one-time scanning.