Quadratic time-scale detection of microemboli in flowing blood with Doppler ultrasound

Brian S. Krongold; Akbar M. Sayeed; Mark Moehring; James A. Ritcey; M. Spencer; Douglas L. Jones

doi:10.1117/12.279483

24 October 1997 Quadratic time-scale detection of microemboli in flowing blood with Doppler ultrasound

Brian S. Krongold, Akbar M. Sayeed, Mark Moehring, James A. Ritcey, M. Spencer, Douglas L. Jones

Proceedings Volume 3162, Advanced Signal Processing: Algorithms, Architectures, and Implementations VII; (1997) https://doi.org/10.1117/12.279483
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

Small formed elements and gas bubbles in flowing blood, called microemboli, can be detected using pulse Doppler ultrasound. In this application, a pulsed constant-frequency ultrasound signal insonates a volume of blood in the middle cerebral artery, and microemboli moving through this sample volume produce a Doppler shifted transient reflection. Current detection methods include searching for these transients in a short-time Fourier transform (STFT) of the reflected signal. However, since the embolus transit time through the Doppler sample volume is inversely proportional to the embolus velocity (Doppler shift frequency), a matched-filter detector should in principle use a wavelet transform, rather than a short-time Fourier transform, for optimal results. Closer examination of the Doppler shift signals usually shows a chirping behavior apparently due to acceleration or deceleration of the emboli during their transit through the Doppler sample volume. These variations imply that a linear wavelet detector is not optimal. We argue from physical principles that quadratic time- scale detectors provide a robustness to variations that is nearly optimal for embolus detection. Using a theory for optimal quadratic time-scale detection, we develop a method for designing the optimal detection kernels from training data and derive efficient algorithms for implementation of the resulting quadratic time-scale detectors. The performance of these detectors is compared with optimized STFT and wavelet detectors. The performance for all of these methods is found to be very similar, and on average only about 2.5 dB less than an 'oracle' detector which provides a theoretical upper bound for microembolus detection.

Citation Download Citation

Brian S. Krongold, Akbar M. Sayeed, Mark Moehring, James A. Ritcey, M. Spencer, and Douglas L. Jones "Quadratic time-scale detection of microemboli in flowing blood with Doppler ultrasound", Proc. SPIE 3162, Advanced Signal Processing: Algorithms, Architectures, and Implementations VII, (24 October 1997); https://doi.org/10.1117/12.279483

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available