Search

This study aims to assess wildfire hazard in northern Portugal by combining landscape-scale wildfire spread modeling and connectivity analysis to help fuel management planning. We used the Minimum Travel Time (MTT) algorithm to run simulations under extreme (95th percentile) fire weather conditions. We assessed wildfire hazard through burn probability, fire size, conditional flame length and fire potential index wildfire descriptors. Simulated fireline intensity (FLI) using historical fire weather conditions were used to build landscape networks and assess the impact of weather severity in landscape wildfire connectivity (Directional Index of Wildfire Connectivity, DIWC). Our results showed that 27 % of the study area is likely to experience high-intensity fires and 51 % of it is susceptible to spread fires larger than 1000 ha. Furthermore, the increase in weather severity led to the increase in the extent of high-intensity fires and highly connected fuel patches, covering about 13 % of the landscape in the most severe weather. Shrublands and pine forests are the main contributors for the spread of these fires, and highly connected patches were mapped. These are candidates for targeted fuel treatments. This study contributes to improving future fuel treatment planning by integrating wildfire connectivity in wildfire management planning of fire-prone Mediterranean landscapes.

The importance of implementing preventive fuel reduction strategies to build wildfire resilient landscapes has been increasingly present in the Portuguese politicians’ agenda. Science-based information is crucial to guide decision-makers, to better allocate resources, to decrease the projected increasing impacts of large wildfires following climate change, and to ensure the sustainability of environmental resources. Currently, fuel management is implemented without prior evaluation of wildfire exposure or optimization of strategic location of landscape treatments units, impairing a greater reduction in wildfire hazard and losses.Prescribed burning can be used to create spatial fuel discontinuities in the landscape thus, to mitigate wildfire impacts. This study proposes to evaluate wildfire exposure in a large and diverse fire-prone area (~193 000ha) containing the Cabreira Mountain, located in Northwestern Portugal. The main goal is to locate vegetation patches where fuel management can decrease landscape connectivity, fire spread (ROS) and fireline intensity (FLI), simultaneously reducing wildfire burn probability (BP). To address this, we run simulations using the FlamMap MTT fire spread model and quantify landscape connectivity using indexes from the graph theory, under different weather scenarios. Input data on fuels and topography were assembled in a binary landscape file at 100m spatial resolution.Fire regime analysis was done for burned areas larger than 100 ha, from 2001 to 2019. Using the national fire ignition database and satellite data, the dates of active fire progression and fire durations are calculated. Daily weather variables (temperature, relative humidity, wind speed and direction) corresponding to those dates are compiled. To calibrate the fire model, we compare the observed and the estimated distributions of fire sizes, and the observed fire frequency with the estimated BP. A hierarchical clustering analysis identified three historical weather scenarios. Besides these a 95th percentile extreme weather scenario is also defined.Results show a strong relationship between wind speed and landscape connectivity. The contribution of old, burned Pine stands and shrubland areas, mainly located at the east part of the Cabreira Mountain, is high for the overall landscape connectivity. For the extreme weather scenario, assessment of the impact of different fuel treatment extents (Treatment Optimization Model), from 5 to 30%, on the landscape connectivity and on the decrease of the FLI values showed that with a 20% of fuel treatment area (~39 000ha): 1) landscape connectivity decreases 85%; 2) the proportion of the two most extreme FLI classes decreases to ~10% within the study area.Based on the results, we discuss the best strategies to reduce wildfire hazard for multi criteria based on the studied fire regime and under different weather scenarios, providing information to support a fire management plan. This study explores the potential of fire spread models and graph theory to assess wildfire landscape connectivity and to identify the landcover patches that mostly contribute to that, to determine optimal landscape treatment proportion and to evaluate the impact of treatment locations on the decrease of wildfire properties, ultimately leading to a more comprehensive and effective wildfire management strategy.

The aim of our prospective study was to compare the diagnostic accuracy of early, delayed and dual-time-point positron emission tomography (PET) acquisition with contrast enhanced computed tomography (CT) within a PET-CT examination in the evaluation of pulmonary solitary nodules (SPNs).Thirty patients were enrolled in the study. All the patients underwent a dual-time-point PET-CT examination. Whole-body PET images were acquired at 50 min after fluorine18-fluorodeoxyglucose ((18)F-FDG) administration (early), followed by a chest acquisition (delayed). Lung nodules with maximum standardised uptake value SUVmaxor =2.5 were considered malignant. SUVmax was calculated on early and delayed images; SUV increasingor =10% (Delta SUVmax) was considered suggestive of malignancy. Absence of significant lung nodule enhancement (15 Delta HU) at CT was considered strongly predictive of benignity. For the CT morphological assessment, the irregularity of the shape of each lesion was rated. PET-CT results were related to histological assays and clinical records. Diagnostic accuracy was assessed by area under the receiveroperarting characteristic (ROC) curves analysis.Early and delayed SUVmax of malignant nodules were significantly higher than those of benign disease. Early SUVmax sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 77%, 91%, 79.5% and 66.7%; delayed SUVmax corresponding values were 77%, 66%, 74% and 66%; dual-time-point SUVmax values were 83%, 67%, 75% and 74%; DeltaHU values were 94%, 34%, 67%, 96%; CT morphologic evaluation values were 61%, 46%, 60%, 47%. Area under the curve (AUC) for early SUVmax was 0.79, for delayed SUVmax 0.80, for dual-time-point SUVmax 0.85, for DeltaHU 0.63 and for CT morphologic assessment 0.58.In our small series of patients, early and delayed SUVmax showed comparable accuracies, whereas morphological and contrast enhanced CT evaluations showed the lowest accuracies. Dual-time-point SUVmax showed the largest AUC. However, dual-time-point SUVmax was most sensitive, whereas single-time-point SUVmax was most specific.

Cranial osteomyelitis is a potentially fatal lesion. White blood cell scanning (WBC) with 99mTc-hexamethylpropylene amine oxime (HMPAO) has proven highly sensitive and specific in the diagnosis and follow-up of patients with suspected osteomyelitis. In this report we show the usefulness of SPECT and transmission CT performed simultaneously using a hybrid imaging device for the functional anatomic mapping of soft tissue and cranial bone infections. 99mTc-HMPAO-labeled leukocytes scintigraphy was performed on an elderly diabetic man with an intracranial mass lesion and with suspected temporal bone infection. Planar scans were acquired 30 min, 4 h, and 24 h after injection. SPECT/CT was obtained 6 h after tracer injection, using a dual-head camera coupled with a low-power X-ray tube. The scintigraphic results were matched with the results of surgery and of clinical follow-up. The planar images alone were true-positives for abscess in this patient. SPECT/CT improves the accuracy of99mTc-HMPAO scintigraphy especially in discriminating between soft-tissue and bone involvement. In fact, SPECT/CT also showed temporal bone osteomyelitis. This result indicates that SPECT/CT performed using a hybrid device can improve imaging with 99mTc-HMPAO-labeled leukocytes in patients with suspected osteomyelitis by providing accurate anatomic localization and precise definition of the extent of infection.

123I-FP-CIT SPECT binding to striatal dopamine transporter (DAT) is markedly reduced in patients with Parkinson's disease (PD) and it may also help in identifyng pre-symptomatic nigrostriatal dysfunction in subjects at risk. This study used semi-quantitative analysis of 123I-FP-CIT SPECT to evaluate the possibility of a more extensive and earlier diagnosis of dopaminergic damage. We used qualitative visual assessment and semiquantitative measures of striatal DAT binding using123I-FP-CIT SPECT in 154 patients with suspected PD. A control group comprised 18 people age-matched to the PD group whose follow-up disclosed essential tremor. Abnormal striatal 123I-FP-CIT uptake was evident in 134 out of 154 patients (87%). Qualitative visual assessment showed striatal dopaminergic123I-FP-CIT uptake was significantly reduced in 60.4% (controlateral putamen to the symptoms), in 31.3% (caudate nucleus) and in 8.3% (ipsolateral basal ganglia to the symptoms). Semi-quantitative analysis showed the following results: 32.8%, 50.7% and 16.5% respectively. We compared these two assessments and their correlation with PD clinical progression. At 24 month follow-up, patients with greater dopaminergic damage at semiquantitative analysis showed a more severe motor disability. Our findings indicate that123I-FP-CIT SPECT with semiquantitative analysis can offer a more accurate characterization of the dopaminergic damage in patients with suspected Parkinson's disease.

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia in the elderly. Magnetic resonance (MR) or computed tomography (CT) imaging is recommended for routine evaluation of dementias. The development of molecular imaging agents and the new techniques of MR for AD are critically important for early diagnosis, neuropathogenesis studies and assessing treatment efficacy in AD. Neuroimaging using nuclear medicine techniques such as SPECT, PET and MR spectroscopy has the potential to characterize the biomarkers for Alzheimer's disease. The present review summarizes the results of radionuclide imaging and MR imaging in AD.