The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform
R. Nadarajan - One of the best experts on this subject based on the ideXlab platform.
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CT and MRI image compression using wavelet-based contourlet transform and binary array technique
Journal of Real-Time Image Processing, 2017Co-Authors: G. Uma Vetri Selvi, R. NadarajanAbstract:Compression techniques are essential for efficient storage and fast transfer of medical image data. In this paper, a rapid 2-D lossy compression technique constructed using wavelet-based contourlet transform (WBCT) and binary array technique (BAT) has been proposed for computed tomography (CT) and magnetic resonance imaging (MRI) images. In WBCT, the high-frequency subband obtained from wavelet transform is further decomposed into multiple directional subbands by directional filter bank to obtain more directional information. The relationship between the coefficients has been changed in WBCT as it has more directions. The differences in parent–child relationships are handled by a repositioning algorithm. The repositioned coefficients are then subjected to quantization. The quantized coefficients are further compressed by BAT where the most Frequently Occurring Value is coded only once. The proposed method has been experimented with real-time CT and MRI images, the results indicated that the processing time of the proposed method is less compared to existing wavelet-based set-partitioning in hierarchical trees and set-partitioning embedded block coders. The evaluation results obtained from radiologists indicated that the proposed method could reproduce the diagnostic features of CT and MRI images precisely.
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A rapid compression technique for 4-D functional MRI images using data rearrangement and modified binary array techniques
Australasian Physical & Engineering Sciences in Medicine, 2015Co-Authors: G. Uma Vetri Selvi, R. NadarajanAbstract:Compression techniques are vital for efficient storage and fast transfer of medical image data. The existing compression techniques take significant amount of time for performing encoding and decoding and hence the purpose of compression is not fully satisfied. In this paper a rapid 4-D lossy compression method constructed using data rearrangement, wavelet-based contourlet transformation and a modified binary array technique has been proposed for functional magnetic resonance imaging (fMRI) images. In the proposed method, the image slices of fMRI data are rearranged so that the redundant slices form a sequence. The image sequence is then divided into slices and transformed using wavelet-based contourlet transform (WBCT). In WBCT, the high frequency sub-band obtained from wavelet transform is further decomposed into multiple directional sub-bands by directional filter bank to obtain more directional information. The relationship between the coefficients has been changed in WBCT as it has more directions. The differences in parent–child relationships are handled by a repositioning algorithm. The repositioned coefficients are then subjected to quantization. The quantized coefficients are further compressed by modified binary array technique where the most Frequently Occurring Value of a sequence is coded only once. The proposed method has been experimented with fMRI images the results indicated that the processing time of the proposed method is less compared to existing wavelet-based set partitioning in hierarchical trees and set partitioning embedded block coder (SPECK) compression schemes [ 1 ]. The proposed method could also yield a better compression performance compared to wavelet-based SPECK coder. The objective results showed that the proposed method could gain good compression ratio in maintaining a peak signal noise ratio Value of above 70 for all the experimented sequences. The SSIM Value is equal to 1 and the Value of CC is greater than 0.9 for all experiments. Subjective evaluation on the reconstructed images indicated that the proposed method could reproduce the diagnostic features of fMRI images clearly.
G. Uma Vetri Selvi - One of the best experts on this subject based on the ideXlab platform.
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CT and MRI image compression using wavelet-based contourlet transform and binary array technique
Journal of Real-Time Image Processing, 2017Co-Authors: G. Uma Vetri Selvi, R. NadarajanAbstract:Compression techniques are essential for efficient storage and fast transfer of medical image data. In this paper, a rapid 2-D lossy compression technique constructed using wavelet-based contourlet transform (WBCT) and binary array technique (BAT) has been proposed for computed tomography (CT) and magnetic resonance imaging (MRI) images. In WBCT, the high-frequency subband obtained from wavelet transform is further decomposed into multiple directional subbands by directional filter bank to obtain more directional information. The relationship between the coefficients has been changed in WBCT as it has more directions. The differences in parent–child relationships are handled by a repositioning algorithm. The repositioned coefficients are then subjected to quantization. The quantized coefficients are further compressed by BAT where the most Frequently Occurring Value is coded only once. The proposed method has been experimented with real-time CT and MRI images, the results indicated that the processing time of the proposed method is less compared to existing wavelet-based set-partitioning in hierarchical trees and set-partitioning embedded block coders. The evaluation results obtained from radiologists indicated that the proposed method could reproduce the diagnostic features of CT and MRI images precisely.
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A rapid compression technique for 4-D functional MRI images using data rearrangement and modified binary array techniques
Australasian Physical & Engineering Sciences in Medicine, 2015Co-Authors: G. Uma Vetri Selvi, R. NadarajanAbstract:Compression techniques are vital for efficient storage and fast transfer of medical image data. The existing compression techniques take significant amount of time for performing encoding and decoding and hence the purpose of compression is not fully satisfied. In this paper a rapid 4-D lossy compression method constructed using data rearrangement, wavelet-based contourlet transformation and a modified binary array technique has been proposed for functional magnetic resonance imaging (fMRI) images. In the proposed method, the image slices of fMRI data are rearranged so that the redundant slices form a sequence. The image sequence is then divided into slices and transformed using wavelet-based contourlet transform (WBCT). In WBCT, the high frequency sub-band obtained from wavelet transform is further decomposed into multiple directional sub-bands by directional filter bank to obtain more directional information. The relationship between the coefficients has been changed in WBCT as it has more directions. The differences in parent–child relationships are handled by a repositioning algorithm. The repositioned coefficients are then subjected to quantization. The quantized coefficients are further compressed by modified binary array technique where the most Frequently Occurring Value of a sequence is coded only once. The proposed method has been experimented with fMRI images the results indicated that the processing time of the proposed method is less compared to existing wavelet-based set partitioning in hierarchical trees and set partitioning embedded block coder (SPECK) compression schemes [ 1 ]. The proposed method could also yield a better compression performance compared to wavelet-based SPECK coder. The objective results showed that the proposed method could gain good compression ratio in maintaining a peak signal noise ratio Value of above 70 for all the experimented sequences. The SSIM Value is equal to 1 and the Value of CC is greater than 0.9 for all experiments. Subjective evaluation on the reconstructed images indicated that the proposed method could reproduce the diagnostic features of fMRI images clearly.
S. M. Sonbawne - One of the best experts on this subject based on the ideXlab platform.
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Sun-sky radiometer-derived column-integrated aerosol optical and physical properties over a tropical urban station during 2004-2009
Journal of Geophysical Research, 2011Co-Authors: Sumit Kumar, P. C. S. Devara, K. K. Dani, S. M. Sonbawne, Sabyasachi SahaAbstract:[1] This paper reports the first observational results of aerosol characteristics over Pune, India (an AERONET site), using CIMEL Sun-sky radiometer. Here 5 years of observational data have been analyzed. The aerosol loading, in terms of the aerosol type and optical depth, undergoes strong seasonal variation over Pune with coarse-mode aerosols dominating during premonsoon season while fine-mode anthropogenic pollution particles result in boundary layer haze during postmonsoon and winter months. The daily mean AOD440 at this location ranged between 0.10 and 1.12, with the most Frequently Occurring Value in the range 0.45–0.55. The overall mean for the 5 year period is 0.49, with a day-to-day variability of about 36.7%. The annual average of CWV over the region shows a fluctuating trend with a marginal increase in the last 2 years. CWV shows strong annual cycle with two maxima, one in the postmonsoon and the other in the premonsoon season. Angstrom exponent (α) varies in the range 0.3–1.7, with large seasonal variability. The spectral variation of SSA has been found to be large during the postmonsoon season as compared to that in the other seasons. Real n(λ) and imaginary k(λ) parts of complex refractive index show contrasting spectral behavior during the observational period. The average asymmetry factor (g) representative of the total aerosol layer exhibits a distinct wavelength dependence with g = 0.70 (0.02) at 440 nm and decreasing to 0.64 (0.04) at 1020 nm.
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Variability in Sun photometer–derived total ozone over a tropical urban station
Journal of Geophysical Research, 2004Co-Authors: P. C. S. Devara, Govindan Pandithurai, R. S. Maheskumar, K. K. Dani, Subodh K. Saha, S. M. SonbawneAbstract:[1] A portable, handheld, multichannel Sun photometer (ozonometer) has been used to measure total column ozone over Pune (18°32′N, 73°51′E, 559 m above mean sea level), India, a tropical urban station. Data collected on about 575 mostly clear-sky days during the 5 year period from May 1998 to May 2003 have been used in this study to examine diurnal and seasonal variations. The overall daily mean total ozone at this station is 254 Dobson units (DU), with a variability of about 7%, while the most Frequently Occurring Value is in the range 241–250 DU. The diurnal (daytime) patterns are observed to be different in the winter (December–February), premonsoon (March–May), and postmonsoon (October–November) seasons. There exists a predominant seasonal oscillation in total ozone, with higher Values (265 DU) during premonsoon months and lower Values (246 DU) during winter months. Ground-based Sun photometer–derived total ozone variations compare very well with those obtained by Earth Probe-Total Ozone Mapping Spectrometer.
P. C. S. Devara - One of the best experts on this subject based on the ideXlab platform.
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Sun-sky radiometer-derived column-integrated aerosol optical and physical properties over a tropical urban station during 2004-2009
Journal of Geophysical Research, 2011Co-Authors: Sumit Kumar, P. C. S. Devara, K. K. Dani, S. M. Sonbawne, Sabyasachi SahaAbstract:[1] This paper reports the first observational results of aerosol characteristics over Pune, India (an AERONET site), using CIMEL Sun-sky radiometer. Here 5 years of observational data have been analyzed. The aerosol loading, in terms of the aerosol type and optical depth, undergoes strong seasonal variation over Pune with coarse-mode aerosols dominating during premonsoon season while fine-mode anthropogenic pollution particles result in boundary layer haze during postmonsoon and winter months. The daily mean AOD440 at this location ranged between 0.10 and 1.12, with the most Frequently Occurring Value in the range 0.45–0.55. The overall mean for the 5 year period is 0.49, with a day-to-day variability of about 36.7%. The annual average of CWV over the region shows a fluctuating trend with a marginal increase in the last 2 years. CWV shows strong annual cycle with two maxima, one in the postmonsoon and the other in the premonsoon season. Angstrom exponent (α) varies in the range 0.3–1.7, with large seasonal variability. The spectral variation of SSA has been found to be large during the postmonsoon season as compared to that in the other seasons. Real n(λ) and imaginary k(λ) parts of complex refractive index show contrasting spectral behavior during the observational period. The average asymmetry factor (g) representative of the total aerosol layer exhibits a distinct wavelength dependence with g = 0.70 (0.02) at 440 nm and decreasing to 0.64 (0.04) at 1020 nm.
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Variability in Sun photometer–derived total ozone over a tropical urban station
Journal of Geophysical Research, 2004Co-Authors: P. C. S. Devara, Govindan Pandithurai, R. S. Maheskumar, K. K. Dani, Subodh K. Saha, S. M. SonbawneAbstract:[1] A portable, handheld, multichannel Sun photometer (ozonometer) has been used to measure total column ozone over Pune (18°32′N, 73°51′E, 559 m above mean sea level), India, a tropical urban station. Data collected on about 575 mostly clear-sky days during the 5 year period from May 1998 to May 2003 have been used in this study to examine diurnal and seasonal variations. The overall daily mean total ozone at this station is 254 Dobson units (DU), with a variability of about 7%, while the most Frequently Occurring Value is in the range 241–250 DU. The diurnal (daytime) patterns are observed to be different in the winter (December–February), premonsoon (March–May), and postmonsoon (October–November) seasons. There exists a predominant seasonal oscillation in total ozone, with higher Values (265 DU) during premonsoon months and lower Values (246 DU) during winter months. Ground-based Sun photometer–derived total ozone variations compare very well with those obtained by Earth Probe-Total Ozone Mapping Spectrometer.
K. K. Dani - One of the best experts on this subject based on the ideXlab platform.
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Sun-sky radiometer-derived column-integrated aerosol optical and physical properties over a tropical urban station during 2004-2009
Journal of Geophysical Research, 2011Co-Authors: Sumit Kumar, P. C. S. Devara, K. K. Dani, S. M. Sonbawne, Sabyasachi SahaAbstract:[1] This paper reports the first observational results of aerosol characteristics over Pune, India (an AERONET site), using CIMEL Sun-sky radiometer. Here 5 years of observational data have been analyzed. The aerosol loading, in terms of the aerosol type and optical depth, undergoes strong seasonal variation over Pune with coarse-mode aerosols dominating during premonsoon season while fine-mode anthropogenic pollution particles result in boundary layer haze during postmonsoon and winter months. The daily mean AOD440 at this location ranged between 0.10 and 1.12, with the most Frequently Occurring Value in the range 0.45–0.55. The overall mean for the 5 year period is 0.49, with a day-to-day variability of about 36.7%. The annual average of CWV over the region shows a fluctuating trend with a marginal increase in the last 2 years. CWV shows strong annual cycle with two maxima, one in the postmonsoon and the other in the premonsoon season. Angstrom exponent (α) varies in the range 0.3–1.7, with large seasonal variability. The spectral variation of SSA has been found to be large during the postmonsoon season as compared to that in the other seasons. Real n(λ) and imaginary k(λ) parts of complex refractive index show contrasting spectral behavior during the observational period. The average asymmetry factor (g) representative of the total aerosol layer exhibits a distinct wavelength dependence with g = 0.70 (0.02) at 440 nm and decreasing to 0.64 (0.04) at 1020 nm.
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Variability in Sun photometer–derived total ozone over a tropical urban station
Journal of Geophysical Research, 2004Co-Authors: P. C. S. Devara, Govindan Pandithurai, R. S. Maheskumar, K. K. Dani, Subodh K. Saha, S. M. SonbawneAbstract:[1] A portable, handheld, multichannel Sun photometer (ozonometer) has been used to measure total column ozone over Pune (18°32′N, 73°51′E, 559 m above mean sea level), India, a tropical urban station. Data collected on about 575 mostly clear-sky days during the 5 year period from May 1998 to May 2003 have been used in this study to examine diurnal and seasonal variations. The overall daily mean total ozone at this station is 254 Dobson units (DU), with a variability of about 7%, while the most Frequently Occurring Value is in the range 241–250 DU. The diurnal (daytime) patterns are observed to be different in the winter (December–February), premonsoon (March–May), and postmonsoon (October–November) seasons. There exists a predominant seasonal oscillation in total ozone, with higher Values (265 DU) during premonsoon months and lower Values (246 DU) during winter months. Ground-based Sun photometer–derived total ozone variations compare very well with those obtained by Earth Probe-Total Ozone Mapping Spectrometer.
