interpolation

This aimed to compare the interpolation of lead and zinc concentration at the National Lead and Zinc Corporation using Landsat satellite and laboratory data to introduce an optimal interpolation method.

After collecting the laboratory data, geostatistical approaches were applied to model the spatial distribution of lead and zinc, including radial basis functions, inverse distance weighting, and ordinary kriging (Gaussian, spherical, exponential, and circular). Estimation accuracy was evaluated by cross-validation and MAE, MBE, and RMSE diagnostic statistics.

The Gaussian model had the lowest error and was the optimal method for modeling lead and zinc. After investigating the correlations between the Landsat 5 satellite bands and soil element concentrations, the spatial distribution of lead and zinc was re-zoned in the ArcGIS software. In both methods, estimation accuracy was evaluated by cross-validation and MAE, MBE, and RMSE diagnostic statistics.

The MAE and RMSE of the satellite data of lead were 38.36 and 91.73, while they were 52.93 and 74.57 for zinc, respectively. The experimental data of lead were 53.04 and 125.18while they were 108.15 and 239.25 for zinc, respectively. The accuracy of the satellite data in the interpolation of the investigated elements had lower error and higher accuracy.

Estimating air pollution levels in areas with no measurements is a major concern in health-related studies. Therefore, the aim of this study was to investigate the amount of exposure to particulate matter below 2.5 μ (PM2.5) in the metropolis of Tehran.

The hourly concentrations of PM2.5 during 2017-2018 period were acquired from the Department of Environment (DOE) and Air Quality Control Company of Tehran (AQCC). The hourly concentrations were validated and 24-h concentrations were calculated. Inverse distance weighting (IDW), Universal Kriging, and Ordinary Kriging were used to spatially model the PM2.5 over Tehran metropolis area. Root Mean Square Error (RMSE) and Mean Error (ME) were used to measure and control for the accuracy of the methods.

The results of this study showed that RMSE and MENA values in Kriging method was less than the IDW, which indicates that the Kriging was the best method to estimate PM2.5 concentrations. According to the final map, the highest annual concentrations of PM2.5 were observed in the southern and southwestern areas of Tehran (districts 10, 15, 16, 17, and 18). The lowest exposure to PM2.5 was found to be in districts 1, 2, 3, 6, and 8.

It can be concluded that Kriging method can predict spatial variations of PM2.5 more accurately than IDW method.

Cardiac echocardiography and cardiac ECG-gated single-photon emission computed tomography (SPECT) are the most common modalities for left ventricle (LV) volumes and function assessment. The temporal resolution of SPECT images is limited and an ECG provides better temporal resolution. This study investigates the impact of frame numbers on images in terms of qualitative and quantitative assessments.

In this study, 5 patients underwent echocardiography and cardiac ECG-gated SPECT imaging, and 5 standard views of the LV were recorded to determine LV walls boundaries and volumes. Also, 2 original images with 8 frames and 16 frames per cardiac cycle were recorded simultaneously in a single gantry orbit. Using the data extracted from the LV model, 8 extra new frames were created with interpolation between existing frames of the original 8-frame image. Three series of images (8 and 16 original and 16 interpolated) were reconstructed separately. LV volumes and ejection fraction (EF) were calculated using Quantitative Gated SPECT (QGS) software.

Compared to the original 8-frame gating, original 16-frame gated images resulted in larger end-diastole volume (EDV) (mean ± SD: 68.6 ± 27.11 mL vs 66.2±25.41 mL, p<0.001), smaller end-systole volume (ESV) (mean ± SD: 24.6±8.7 mL vs 26±7.3 mL, p<0.001), and higher EF (64% vs 60.2%, p<0.001). The results for the interpolated series were also different from the original images (closer to the original 16-frame series rather than 8-frame).

Changing the frame number from 8 to 16 in cardiac ECG-gated SPECT images caused a significant change in LV volumes and EF. Frame interpolation with sophisticated algorithms can be used to improve the temporal resolution of SPECT images.