Image Processing Reference
In-Depth Information
FIGURE 2 Block diagram of reconstruction process.
2.1 RF Dataset
The data were taken from examinations in the Department of Hemodynamic in the Heart
Institute of the Medical School of the University of São Paulo (Heart Institute, HCFMUSP),
Brazil, using iLab IVUS equipment (Boston Scientific, Fremont, USA), equipped with a
40-MHz catheter Atlantis SR 40 Pro and anonymized to avoid the identification of the patient
and used only for research purposes.
The RF File Reader (designed by Boston Scientific) is an xml file that contains information
about the examination. This file allows us to identify the number of rows, columns, and frames
from each exam. Beyond this, the reader contains the distance from each pixel in the image, in
Once image atributes have been found using the RF File Reader, it is possible to extract the
data. These data were placed in a tri-dimensional matrix. The rows of this matrix represent the
lines in A-mode, each line with radial information about the vessel, the columns represent the
distance to the tip of catheter and the slices, third dimension, represent each time frames of
the exam. The study of IVUS used in this work results in a 3D matrix, where the dimensions
represents the size of each image and the third dimension being the number of frames.
After this, each frame was submited to the reconstruction shown in Figure 2 .
2.2 Band-Pass Filter
A Buterworth band-pass ilter was applied to dataset in order to eliminate frequencies that do
not come from the transducer. The manufacture of transducer describes the central frequency
emitted by transducer at the tip of catheter as 40 MHz and frequency sample rate as 200 MHz.
Each line in A-mode was iltered by a Buterworth inite impulse response (FIR) ilter. The
frequency range was adjusted between 20 and 60 MHz as can be viewed in Figure 3(a) .
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