Pulse (signal processing)

About: Pulse (signal processing) is a research topic. Over the lifetime, 18160 publications have been published within this topic receiving 154025 citations.

Handbook of MRI Pulse Sequences

Abstract: Part I: Background Introduction. Part II: RF Pulses RF Pulse Shapes Basic RF Pulse Functions Spectral RF Pulses Spatial RF Pulses Adiabatic RF Pulses. Part III: Gradients Gradient Lobe Shapes Imaging Gradients Motion Sensitizing Gradients Correction Gradients. Part IV: Data Acquisition, K-Space Sampling, and Image Reconstruction Signal Acquisition and K-Space Sampling Basics of Physiologica Gating, Triggering, and Monitoring Common Image Reconstruction Techniques. Part V: Pulse Sequences Basic Pulse Sequences Angiographic Pulse Sequences Echo Train Pulse Sequences Advanced Pulse Sequence Techniques.

Qualitative mapping of cerebral blood flow and functional localization with echo-planar MR imaging and signal targeting with alternating radio frequency.

Abstract: PURPOSE: To create qualitative maps of cerebral blood flow (CBF) with the EPISTAR (echo-planar imaging and signal targeting with alternating radio frequency) technique. MATERIALS AND METHODS: The EPISTAR technique was performed in a pig model of hypercapnia and then tested in 26 volunteers by using various paradigms for cortical activation. Echo-planar images were acquired with and without use of a radio-frequency inversion pulse applied to inflowing arterial spins. A qualitative map of CBF was then created by subtracting the image obtained without the radio-frequency pulse from that obtained with the radio-frequency pulse. RESULTS: Progressively more distal portions of the tagged vessels were seen as the inflow time was lengthened until cortical enhancement was seen for inflow times of approximately 1 second or longer. Signal intensity increases from rest to sensorimotor activation ranged from 13% to 193%. CBF changes in the motor strip, primary visual cortex, and the motor area for eye movements were we...

Simultaneous spatial and spectral selective excitation.

Abstract: Using a k-space interpretation of small-tip excitation, a single excitation pulse has been designed that is simultaneously selective in space and resonant frequency. An analytic expression for the response of this pulse has been derived. The pulse has been implemented on a 1.5-T imaging system. The pulse has been applied to a rapid gradient-echo imaging sequence that forms both water and fat images within a breath-holding interval. These rapid images are free of the chemical shift artifacts at organ boundaries that typically afflict conventional rapid images. The pulse can be applied to a variety of other sequences, such as multislice water/fat sequences and rapid k-space scanning. © 1990 Academic Press, Inc.

Pulse responsive device

Abstract: A pulse responsive device, for example, a pulse rate meter or pulse oximetry device, is disclosed, which includes a light emitter and a light sensor for receiving light from the emitter after transmission through, or reflection from, body tissue to give an electrical signal varying according to blood flow or other fluid pulsations. A movement transducer gives an additional electrical signal representing body movements or vibrations, but independent of blood flow pulsations. This movement transducer may include a light emitter and sensor responsive to a different wavelength from the light emitter and light sensor used for measuring, and varying with, blood flow or other fluid pulsations. The pulse responsive device compares the two electrical signals produced to cancel out the movement or vibration noise fro the signal obtained from the light sensor which obtains measurements which vary with blood or other fluid flow pulsations.

Pulse oximetry data confidence indicator

Abstract: An intelligent, rule-based processor provides a pulse indicator designating the occurrence of each pulse in a pulse oximeter-derived photo-plethysmograph waveform. When there is relatively no distortion corrupting the plethysmograph signal, the processor analyzes the shape of the pulses in the waveform to determine where in the waveform to generate the pulse indication. When distortion is present, looser waveform criteria are used to determine if pulses are present. If pulses are present, the pulse indication is based upon an averaged pulse rate. If no pulses are present, no indication occurs. The pulse indicator provides a trigger and amplitude output. The trigger output is used to initiate an audible tone 'beep' or a visual pulse indication on a display, such as a vertical spike on a horizontal trace or a corresponding indication on a bar display. The amplitude output is used to indicate data integrity and corresponding confidence in the computed values of saturation and pulse rate. The amplitude output can vary a characteristic of the pulse indicator, such as beep volume or frequency or the height of the visual display spike. The visual pulse indicator is supplemented by a signal quality alert. Combined with several indicators of signal quality, the alert is used to initiate a warning when data confidence is very low. The alert may be in the form of a message generated on the pulse oximeter display to warn that the accuracy of saturation and pulse rate measurements may be compromised. A confidence-based alarm utilizes signal quality measures to reduce the probability of false alarms when data confidence is low and to reduce the probability of missed events when data confidence is high.