Information Technology Reference
In-Depth Information
MEASUREMENT
Data acquisition using color Doppler unit
SPECTRAL ANALYSIS
Power spectral density and sonogram using Welch FFT
method
CLASSIFICATION
Artificial Immune Recognition System with Fuzzy resource
allocation mechanism
CLASSFICATION RESULTS
Healthy
Atherosclerosis
Fig. 1.
The Procedure used in the proposed system.
extremes of the arterial compliance. We have utilized Toshiba PowerVision 6000
Doppler Ultrasound Unit in the Radiology Department for data acquisition.
A linear ultrasound probe of 10 MHz was used to transmit pulsed ultrasound sig-
nals to the proximal left common carotid artery. In all tests performed on the patients
and healthy subjects, the insonation angle and the presettings of the ultrasound were
kept constant.
2.2 Spectral Analysis of Carotid Artery Doppler Signals
Welch method of power spectrum estimation was applied on the Doppler data. Blood
flow can only be considered statistically stationary for typically 10 to 20 ms. There-
fore acquired Doppler data was grouped in frames of 512 data points and the method
was applied on these frames. Welch's method is one among the classical methods of
spectrum estimation based on FFT.
2.2.1 Welch Method of Spectral Analysis
FFT based Welch method is defined as classical (Nonparametric) method. It is made
the second modification of periodogram spectral estimator, which is to window data
segments prior to computing the periodogram [4-9]. If avaliable information on
the signal consists of the samples
{}
N
n
x
(
n
)
, the periodogram spectral estimator is
=
1
given by;
