Cristina Freitas

Land Use and Land Cover Mapping in the Brazilian Amazon Using Polarimetric Airborne P-Band SAR Data

In September 2000, an airborne synthetic aperture radar (SAR) mission acquired unprecedented full polarimetric P-band data over the Tapajos National Forest (Para State), which is an area in the Brazilian Amazon which has been continuously monitored in the last three decades. Eight land use/cover classes were identified, namely, primary forest, regeneration older than 25 years, regeneration between 12 and 25 years, regeneration between 6 and 12 years, regeneration younger than six years, crops/pasture, bare soil, and floodplain (FP). The objective of this paper is to analyze the potential of full polarimetric P-band data in distinguishing different land use/cover classes with a minimum established Kappa value of 75%, using the latest development on SAR statistical characterization. The iterated conditional mode (ICM) contextual classifier was applied to amplitude, intensity images, biomass index, and some polarimetric parameters (entropy, alpha angle, and anisotropy) extracted from the polarimetric P-band data. As the accuracy obtained for eight classes was not acceptable, another two sets, with five and four classes, were formed by the combination of the previous ones. They were defined by confusion matrix analysis and by the graphical analysis of average backscatter values, entropy, [alpha] angle, and anisotropy images and by the H/alpha plans of the land use samples. The classification accuracy with four classes (three levels of biomass plus FP) was then considered acceptable with a Kappa value of 76.81%, using the ICM classification with the adequate bivariate distribution for the HV and VV channels.

Power spectrum analysis of SAR data for spatial forest characterization in Amazonia

Power spectrum analysis was used for the analysis of spatial forest features from airborne X‐band synthetic aperture radar (SAR) data in the Brazilian Amazon. Spectral estimates were arrived at empirically by periodograms and correlograms, and from autoregressive moving‐average (ARMA) models. The spectral estimates derived from SAR data were validated by those derived from ground data with locational match. The results obtained by ARMA modelling revealed particularly good correspondence between remote sensing and reference data: repeating patterns at pixel level could be detected in the images. These patterns were shown to arise from canopy structure and distances between major tree individuals; and thus allowed the extraction of parameters of spatial forest structure, particularly of forest density. The method was applied to an example area of primary tropical forest, and its spatial patterns were modelled.

Remote Sensing and Geographic Information Systems for the Study of Schistosomiasis in the State of Minas Gerais, Brazil

This article uses remote sensing and geographical information system to establish a statistical model for estimating schistosomiasis prevalence in the state of Minas Gerais, Brazil. Remote sensing data were derived from MODIS and SRTM. The final regression model includes the Digital Elevation Model and winter Normalized Difference Vegetation Index variables. A risk map for the entire state of Minas Gerais is built, based on these variables.

Bone mineral density after simultaneous kidney-pancreas transplantation: four years follow-up of 57 recipients.

Bone disease and an high risk of fractures are major problems in transplantation. Among diabetic patients undergoing simultaneous kidney-pancreas (SKP) transplantation, there are few studies assessing long-term effects on bone mass. The aim of this study was to evaluate bone mineral density (BMD) over 4 years follow-up after SKP transplantation. Fifty-seven patients had 22.8 +/- 5.3 years of prior diabetes, 65% were female, and the overall mean age was 24.3 +/- 5.93 years. At the time of transplantation, the lumbar spine and femoral neck T-scores were -1.75 +/- 1.05 and -1.95 +/- 0.73, respectively; 28% of subjects had evidence of osteoporosis. One year after transplantation, 77.6% of patients displayed improved lumbar T-scores to -1.33 +/- 0.94 (P = .044) with stable femoral neck T-scores. Bone densitometry enhanced gradually through the 4 years follow-up: lumbar T-score to -1.04 +/- 0.67 (P = .004) and femoral neck T-score to -1.69 +/- 0.49 (P = .12). At year 4, no osteoporosis cases were detected but 86.7% of patients did not receive steroids in the immunosuppressive regimen. The graft function remained stable (serum creatinine, 1.2 mg/dL; fasting glucose, 87.7 mg/dL). During the follow-up, BMD improved more significantly at cortical sites. Our study reports a reduced prevalence of fractures (8.7%) compared with the literature, which could be related to a steroid-sparing protocol and/or aggressively treatment of osteoporosis.

Posttransplant Outcomes of Peritoneal Dialysis Versus Hemodialysis Patients

The impact of dialysis modality on posttransplant outcomes remains controversial. The authors have compared primary failure, delayed graft function (DGF), acute rejection episodes as well as patient and allograft survivals among patients undergoing renal transplantation between 2004 and 2009, according to the modality of hemodialysis (HD) versus peritoneal dialysis (PD). We studied 306 patients (268 HD and 38 PD) with a mean follow-up of 29 ± 16 months. The PD cohort included a predominance of females (68.4% vs 36.2%; P = .001), lower age at transplantation (38 ± 14 vs 46 ± 12 years; P = .004), shorter time on dialysis (33 ± 49 vs 59 ± 157 months; P = .043), and higher rate of living donor grafts (PD 31.6% vs HD 13.1%; P = .003). Donor age (PD 43 ± 13 vs HD 45 ± 14 years; P = .30), human leukocyte antigen mismatch (P = .17), panel reactive antibody values (HD 11 ± 22 vs PD 13 ± 26; P = .55), and hyperimmunized patients (HD 3.73%; PD 7.89%; P = .23) were not different. Primary graft failure (3.4% vs 0%; P = .025) and DGF (37.1% vs 13.1%; P = .037) were more frequent among HD patients, but incidences of acute rejection episodes were similar (HD 10.5% vs PD 5.3%; P = 0.19). Neither recipient survival at 1 (97% in PD and HD) or 3 years (HD 90% vs PD 94%; P = .657) nor allograft survival at 1 year (HD 94% vs PD 95%; P = .80) or 3 years: (HD 70%, vs PD 81%; P = .73) were different. Graft function was similar at 1 (HD 64.2 ± 25 vs PD 56.4 ± 24 mL/min; P = .17) and 3 years (HD 62.3 ± 21 vs PD 46 ± 23 mL/min; P = .16). In our study, HD patients showed an higher incidence of DGF and primary allograft failure, but there was no difference in acute rejection episodes, long-term survivals, or renal function.

Pancreas-Kidney Transplantation: Complications and Readmissions in 9-Years of Follow-up

Over 9 years, we have performed 93 simultaneous pancreas-kidney transplants (SPKT). The morbidity of this procedure is high compared with kidney transplantation alone; readmissions are frequent and costs are higher. Herein we have presented the complications during follow-up of these 93 patients. Their mean age was 34 +/- 6 years and prior dialysis time was 32 +/- 25 months. The median hospital stay on the first admission for the transplant procedure was 22 days, including 2 days in the intensive care unit. Bleeding, thrombosis, and infection were the most frequent reasons for prolonged hospitalization. Thirty patients underwent >or=1 surgical reinterventions. Incidence of acute rejection episodes was 11.8%. After discharge, 74.2% of the patients had 197 readmission episodes with infection being the main cause, urinary tract infections, the most frequent; however, systemic viral and fungal infections required the longest readmission periods. The need for surgical interventions, graft dysfunction, and vascular problems were the remaining causes of readmission. At the end of follow-up, 87 patients were alive, 86 with well-functioning kidneys and 74 with normal functioning pancreata. Global survival rates for patient, kidney, and pancreas were 96%, 95%, and 81% at 1-year; 93%, 90%, and 79% at 5-years; and 93%, 90% and 79% at 9-years. Although pancreas-kidney transplant patients are complex presenting many management difficulties, our overall results represent a positive stimulus for diabetic patients.

Risk Mapping of Schistosomiasis in Minas Gerais, Brazil, Using MODIS and Socioeconomic Spatial Data

Schistosomiasis mansoni is a disease with social and behavioral characteristics. Snails of the Biomphalaria species, the diseases intermediate host, use water as a vehicle to infect man, the disease main host. In Brazil, six million people are infected. From 1995 to 2005, more than a million positive cases were reported, 27% of them in the state of Minas Gerais. The objective of this paper is to estimate the prevalence risk of schistosomiasis, in terms of remote sensing, climate, socioeconomic, or neighborhood variables or a subset of them. We present two approaches for modeling and classifying the infection risk: a global and a regional one, both of them using the aforementioned variables. In the first approach, a unique regression model was generated and used to estimate the disease risk for the entire state. In the second approach, the state was divided in four regions, and a model was generated for each of them. The first model obtained 47.2% of overall accuracy (AC) and the second achieved 62.4%, which were considered unsatisfactory. To improve these results, the concept of imprecise classification, defined in terms of the standard deviation of estimates and several reliability levels, is used for the generation of two imprecise classification maps. The AC for the imprecise classification was 83.8% for the global model and 91.9% for the regional one, which were now considered acceptable. Particularly, regionalization has proven to be a good guideline to follow in future works involving geographical aspects and large data heterogeneity.

Relationship Between PALSAR Backscatter and Surface-Roughness Parameters From Iron Laterites in CarajÁs, Amazon Region

The objective of this investigation was to evaluate the influence of micro- and macrotopography on PALSAR fine-beam dual backscattering in the characterization of iron laterites in Carajas Province, Amazon Region. The moderate linear correlation between sigma0 and surface roughness indicated that, only for L-HH polarization, sigma0 was modulated by the morphology of the geological surfaces.

Chylous Ascites in a Renal Transplant Recipient Under Sirolimus (Rapamycin) Treatment

Ascites is a rare complication of renal transplantation. Ascites has been reported after kidney transplantation due to rejection, decapsulation of the graft, urinary or vascular leak, lymphocele, transudation, or infection. While technical complications of the procedure are the most frequent cause, portal hypertension and graft rejection are other causes. Ascites can occur after renal transplantation independent of kidney function. Usually, a time relation can be made between the surgical procedure and ascites development. Chylous ascites is still more uncommon; it is usually related to traumatic lymphatic injury. Drugs are rarely associated with the genesis of ascites. Sirolimus has been associated with a high rate of lymphoceles, lymphedema, and pulmonary alveolar proteinosis. The exact mechanisms remain unknown. The risk for lymphocele formation with sirolimus is 12% to 15%. Ascites is an adverse effect with an incidence between 3% and 20%, but no relation between sirolimus and chylous ascites was previously established. We present a clinical report of chylous ascites in a renal transplant patient under sirolimus therapy; our investigation pointed to sirolimus as the cause.

The use of airborne P-band radar data for land use and land cover mapping in Brazilian Amazonia

The aim of this work was to analyze the potentiality of polarimetric P-band data for land use and land cover mapping in a site of the Brazilian Amazonia. These data are the first P-band image set gathered in the Brazilian Amazonia, so they represent a unique opportunity of analyzing the potentiality of this frequency for classification purposes. The stratification of land use/land cover classes was performed using a classification system specially developed for polarimetric data. Results showed that P-band data were able to discriminate forest and regeneration areas from crop, pasture and bare soil areas. Moreover, regeneration areas (older than 12 years) were successfully distinguished from primary forest and other regeneration stages.