The Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center has processed and released 2100 Landsat ...Thematic Mapper and Enhanced Thematic Mapper Plus surface reflectance scenes, providing 30-m resolution wall-to-wall reflectance coverage for North America for epochs centered on 1990 and 2000. This dataset can support decadal assessments of environmental and land-cover change, production of reflectance-based biophysical products, and applications that merge reflectance data from multiple sensors e.g., the Advanced Spaceborne Thermal Emission and Reflection Radiometer, Multiangle Imaging Spectroradiometer, Moderate Resolution Imaging Spectroradiometer (MODIS). The raw imagery was obtained from the orthorectified Landsat GeoCover dataset, purchased by NASA from the Earth Satellite Corporation. Through the LEDAPS project, these data were calibrated, converted to top-of-atmosphere reflectance, and then atmospherically corrected using the MODIS/6S methodology. Initial comparisons with ground-based optical thickness measurements and simultaneously acquired MODIS imagery indicate comparable uncertainty in Landsat surface reflectance compared to the standard MODIS reflectance product (the greater of 0.5% absolute reflectance or 5% of the recorded reflectance value). The rapid automated nature of the processing stream also paves the way for routine high-level products from future Landsat sensors.
Direct stenting (DS) has been shown to be associated with reduced radiation exposure and procedural costs but has a restenosis rate and clinical outcomes similar to conventional stenting (CS) with ...balloon predilatation. Whether DS confers benefit in diabetic patients, who have been shown to have high restenosis risk after stent implantation, remains unknown.
In a multicenter randomized trial, diabetic patients undergoing elective coronary stent implantation for a de novo lesion in a native coronary artery between April 2001 and October 2002 were randomized into DS or CS treatment groups. All patients received NirElite stents (SciMed, Boston Scientific, Maple Grove, Minn). They were scheduled to undergo a 6-month angiographic follow-up with quantitative coronary analysis evaluation. The primary end point was a 6-month binary restenosis rate and the secondary end point involved 6-month all-cause mortality, nonfatal acute myocardial infarction, or target vessel revascularization rates.
A total of 128 diabetic patients were randomized into DS or CS treatment groups (n = 64, both groups). The 2 groups were well matched in baseline and lesion characteristics. The procedural success rate was similar (DC vs CS; 98.4% vs 96.9%). Nineteen patients (29.7%) crossed over from DS to CS. Six-month angiographic follow-up showed similar restenosis rates, minimum luminal diameter and late lumen loss. The binary restenosis rate was 43% in DS and 52% in CS groups (
P = NS). The 6-month all-cause mortality, nonfatal acute myocardial infarction, or target vessel revascularization rates were also similar in both groups.
Among diabetic patients undergoing elective coronary stent implantation, DS is safe and feasible. However, it is not associated with reduction in restenosis rate or improvement in clinical outcomes when compared with CS.
