Evaluation of a polarimetric attenuation correction algorithm for NASA D3R observations during the IFloodS field campaign

2015 ◽  
Author(s):  
Haonan Chen ◽  
V. Chandrasekar
Keyword(s):  
Attenuation Correction ◽  
Correction Algorithm ◽  
Field Campaign

N staging of lung cancer patients with PET/MRI using a three-segment model attenuation correction algorithm: Initial experience

2013 ◽  
Vol 23 (11) ◽  
pp. 3161-3169 ◽  
Author(s):  
A. A. Kohan ◽  
J. A. Kolthammer ◽  
J. L. Vercher-Conejero ◽  
C. Rubbert ◽  
S. Partovi ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Cancer Patients ◽  
Attenuation Correction ◽  
Initial Experience ◽  
Correction Algorithm ◽  
Lung Cancer Patients ◽  
Segment Model ◽  
N Staging

scholarly journals Integrated Correction Algorithm for X Band Dual-Polarization Radar Reflectivity Based on CINRAD/SA Radar

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 119
Author(s):  
Chao Wang ◽  
Chong Wu ◽  
Liping Liu ◽  
Xi Liu ◽  
Chao Chen
Keyword(s):  
Attenuation Correction ◽  
Fixed Ratio ◽  
Water Layer ◽  
Resonance Scattering ◽  
Rain Attenuation ◽  
Correction Algorithm ◽  
Dual Polarization ◽  
Differential Phase ◽  
X Band ◽  
Ratio Correction

The values of ratio a of the linear relationship between specific attenuation and specific differential phase vary significantly in convective storms as a result of resonance scattering. The best-linear-fit ratio a at X band is determined using the modified attenuation correction algorithm based on differential phase and attenuation, as well as the premise that reflectivity is unattenuated in S band radar detection. Meanwhile, the systemic reflectivity bias between the X band radar and S band radar and water layer attenuation (ZW) on the wet antenna cover of the X band radar are also considered. The good performance of the modified correction algorithm is demonstrated in a moderate rainfall event. The data were collected by four X band dual-polarization (X-POL) radar sites, namely, BJXCP, BJXFS, BJXSY, and BJXTZ, and a China’s New Generation Weather Radar (CINRAD/SA radar) site, BJSDX, in Beijing on 20 July 2016. Ratio a is calculated for each volume scan of the X band radar, with a mean value of 0.26 dB deg−1 varying from 0.20 to 0.31 dB deg−1. The average values of systemic reflectivity bias between the X band radar (at BJXCP, BJXFS, BJXSY, and BJXTZ) and S band radar (at BJSDX) are 0, −3, 2, and 0 dB, respectively. The experimentally determined ZW is in substantial agreement with the theoretically calculated ones, and their values are an order of magnitude smaller than rain attenuation. The comparison of the modified attenuation correction algorithm and the empirical-fixed-ratio correction algorithm is further evaluated at the X-POL radar. It is shown that the modified attenuation correction algorithm in the present paper provides higher correction accuracy for rain attenuation than the empirical-fixed-ratio correction algorithm.

scholarly journals Polarimetric Attenuation Correction in Heavy Rain at C Band

2011 ◽  
Vol 50 (1) ◽  
pp. 39-58 ◽  
Author(s):  
Ji-Young Gu ◽  
A. Ryzhkov ◽  
P. Zhang ◽  
P. Neilley ◽  
M. Knight ◽  
...  
Keyword(s):  
Attenuation Correction ◽  
Metropolitan Area ◽  
Hot Spots ◽  
Heavy Rain ◽  
Radar Signal ◽  
Polarimetric Radar ◽  
Correction Algorithm ◽  
Correction Scheme ◽  
Radar Measurements ◽  
Convective Cells

Abstract The ability of C-band polarimetric radar to account for strong attenuation/differential attenuation is demonstrated in two cases of heavy rain that occurred in the Chicago, Illinois, metropolitan area on 5 August 2008 and in central Oklahoma on 10 March 2009. The performance of the polarimetric attenuation correction scheme that separates relative contributions of “hot spots” (i.e., strong convective cells) and the rest of the storm to the path-integrated total and differential attenuation has been explored. It is shown that reliable attenuation correction is possible if the radar signal is attenuated by as much as 40 dB. Examination of the experimentally derived statistics of the ratios of specific attenuation Ah and differential attenuation ADP to specific differential phase KDP in hot spots is included in this study. It is shown that these ratios at C band are highly variable within the hot spots. Validation of the attenuation correction algorithm at C band has been performed through cross-checking with S-band radar measurements that were much less affected by attenuation. In the case of the Oklahoma storm, a comparison was made between the data collected by closely located C-band and S-band polarimetric radars.

Analytic Study of the Post Attenuation Correction Algorithm

SIAM Review ◽  
1995 ◽  
Vol 37 (3) ◽  
pp. 439-440 ◽  
Author(s):  
William G. Hawkins
Keyword(s):  
Attenuation Correction ◽  
Analytic Study ◽  
Correction Algorithm

Myocardial perfusion scintigraphy in Germany

2007 ◽  
Vol 46 (02) ◽  
pp. 49-55 ◽  
Author(s):  
W. Burchert ◽  
F. M. Bengel ◽  
R. Zimmermann ◽  
J. vom Dahl ◽  
W. Schäfer ◽  
...  
Keyword(s):  
Nuclear Medicine ◽  
Myocardial Perfusion ◽  
Attenuation Correction ◽  
Working Group ◽  
Primary Care Physicians ◽  
Gated Spect ◽  
Myocardial Perfusion Scintigraphy ◽  
German Society ◽  
University Hospitals ◽  
Perfusion Scintigraphy

SummaryThe working group Cardiovascular Nuclear Medicine of the German Society of Nuclear Medicine (DGN), in cooperation with the working group Nuclear Cardiology of the German Cardiac Society (DGK), decided to conduct a national survey on myocardial perfusion scintigraphy (MPS). Method: A questionnaire to evaluate MPS for the year 2005 was sent. Results: 346 completed questionnaires had been returned (213 private practices, 99 hospitals and 33 university hospitals). MPS of 112 707 patients were reported with 110 747 stress and 95 878 rest studies. The majority (>75%) was performed with 99mTc-MIBI or tetrofosmin. 201Tl stress-redistribution was used in 22 637 patients (20%). The types of stress were exercise in 78%, vasodilation with adenosine or dipyridamol in 21% and dobutamine in 1%. 99.97% of all MPS were SPECT studies. Gated SPECT was performed in 36% of the stress and in 32% of the rest studies. An attenuation correction was used in 21%. 29 institutions (8%) performed gated SPECT (stress and rest) and attenuation correction. 47% of all MPS were requested by ambulatory care cardiologists, 17% by internists, 12% by primary care physicians, 21% by hospital departments and 2% by others. Conclusion: In Germany, MPS is predominantly performed with 99mTc-perfusion agents. The common type of stress is ergometry. Gated SPECT and attenuation correction do not yet represent standards of MPS practice in Germany, which indicates some potential of optimization.

F-18-FDG Positron Imaging in Oncological Patients: Gamma Camera Coincidence Detection versus Dedicated PET

1999 ◽  
Vol 38 (04) ◽  
pp. 108-114 ◽  
Author(s):  
H.-J. Kaiser ◽  
U. Cremerius ◽  
O. Sabri ◽  
M. Schreckenberger ◽  
P. Reinartz ◽  
...  
Keyword(s):  
Attenuation Correction ◽  
Spatial Resolution ◽  
Gamma Camera ◽  
Lesion Detection ◽  
Coincidence Detection ◽  
System Sensitivity ◽  
Oncological Patients ◽  
Phantom Studies ◽  
Pet System ◽  
Dedicated Pet

Summary Aim of the present study was to investigate the feasibility of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) imaging in oncological patients with a dual head gamma camera modified for coincidence detection (MCD). Methods: Phantom studies were done to determine lesion detection at various lesion-to-background ratios, system sensitivity and spatial resolution. Thirty-two patients with suspected or known malignant disease were first studied with a dedicated full-ring PET system (DPET) applying measured attenuation correction and subsequently with an MCD system without attenuation correction. MCD images were first interpreted without knowledge of the DPET findings. In a second reading, MCD and DPET were evaluated simultaneously. Results: The phantom studies revealed a comparable spatial resolution for DPET and MCD (5.9 × 6.3 × 4.2 mm vs. 5.9 × 6.5 × 6.0 mm). System sensitivity of MCD was less compared to DPET (91 cps/Bq/ml/cmF0V vs. 231 cps/ Bq/ml/cmFOv). At a lesion-to-background ratio of 4:1, DPET depicted a minimal phantom lesion of 1.0 cm in diameter, MCD a minimal lesion of 1.6 cm. With DPET, a total of 91 lesions in 27 patients were classified as malignant. MCD without knowledge of DPET results revealed increased FDG uptake in all patients with positive DPET findings. MCD detected 72 out of 91 DPET lesions (79.1 %). With knowledge of the DPET findings, 11 additional lesions were detected (+12%). MCD missed lesions in six patients with relevance for staging in two patients. All lesions with a diameter above 18 mm were detected. Conclusion: MCD FDG imaging yielded results comparable to dedicated PET in most patients. However, a considerable number of small lesions clearly detectable with DPET were not detected by MCD alone. Therefore, MCD cannot yet replace dedicated PET in all oncological FDG studies. Further technical refinement of this new method is needed to improve image quality (e.g. attenuation correction).

Buffalo Crusaders: The Sacred Struggle for America’s Last Wild and Pure Herd

2017 ◽  
Author(s):  
Justin Farrell
Keyword(s):  
Brucella Abortus ◽  
Direct Action ◽  
Moral Relativism ◽  
Religious Conflict ◽  
Field Campaign ◽  
Activist Group ◽  
Religious Dimensions ◽  
Post Hoc

This chapter examines the bitter, long-lasting, and sometimes violent dispute over the Yellowstone bison herd—America's only remaining genetically pure and free-roaming herd, which once numbered more than 30 million but was exterminated down to a mere 23 single animals. This intractable issue hinges on current scientific disagreements about the biology and ecology of the disease brucellosis (Brucella abortus). But in recent years, a more radical, grassroots, and direct action activist group called the Buffalo Field Campaign (BFC) has found success by shifting the focus of the debate away from science, toward the deeper religious dimensions of the issue. The chapter shows how the infusion of the conflict with moral and spiritual feeling has brought to the fore deeper questions that ultimately needed to be answered, thus making this a public religious conflict as much as a scientific one, sidestepping rabbit holes of intractability. It observes the ways in which BFC activists engaged in a phenomenon called moral and religious “muting.” This has theoretical implications for understanding how certain elements of culture (e.g., individualism and moral relativism) can organize and pattern others—especially in post hoc explanations of religiously motivated activism.

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