In this paper, a theoretical framework is developed which removes the Gaussian assumption commonly used in ultrasonic attenuation estimation based on mean frequency shift. The theory is developed for general non-Gaussian spectra and for media whose attenuation coefficient is nonlinear with frequency. Then, a linear approximation in the estimation of the attenuation coefficient's slope is examined. It is shown that the error due to the linear approximation is negligibly small.
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http://dx.doi.org/10.1177/016173468400600202 | DOI Listing |
Clin Nucl Med
January 2025
From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland.
Purpose: The common approach for organ segmentation in hybrid imaging relies on coregistered CT (CTAC) images. This method, however, presents several limitations in real clinical workflows where mismatch between PET and CT images are very common. Moreover, low-dose CTAC images have poor quality, thus challenging the segmentation task.
View Article and Find Full Text PDFJ Neural Eng
January 2025
Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
Transcranial ultrasound stimulation (TUS) presents challenges in ultrasound wave transmission through the skull, affecting study outcomes due to aberration and attenuation. While planning strategies incorporating 3D computed tomography (CT) scans help mitigate these issues, they expose participants to radiation, which can raise ethical concerns. A solution involves generating skull masks from participants' anatomical magnetic resonance imaging (MRI).
View Article and Find Full Text PDFJ Contam Hydrol
January 2025
Mines Paris, PSL University, Center for Geosciences and Geoengineering, France; ORANO Mining, Environmental R&D Dpt., France.
Sandstone-hosted uranium is mined in the Sahel regions of Niger. The Teloua aquifer is located beneath the ore-processing facilities of one such former mine, COMINAK. The pores of the sandstone bedrock are partially filled by tosudite, a clay with sorption capacities.
View Article and Find Full Text PDFCoherent heterodyne lidars are typically used for windspeed and attenuated backscattering measurements. The lack of molecular backscattering detection capability has limited the calibrated backscattering measurements until recent advances in coherent lidar technology. In this work, the simultaneous detection of aerosol and molecular backscattering is demonstrated with coherent heterodyne lidar, and the results are compared with a state-of-the-art Raman lidar PollyXT as a reference in a long-range for the first time.
View Article and Find Full Text PDFNowadays, spaceborne LiDAR technology, particularly ICESat-2, has become a transformative tool in marine environmental research. Unlike traditional passive optical remote sensing methods, ICESat-2 offers detailed vertical structure mapping of oceanic optical properties. Despite the potential of ICESat-2 for observing the optical vertical structure, its application in the East China Sea with complex hydrological conditions and dynamic ecosystems remains limited.
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