Figure 1.
The flowchart of the proposed method.
Figure 2.
The region inside the yellow contour represents the acoustic shadowing behind the calcified plaque. (b) The image corresponding to (a) processed by the RMM with the class number , and the colorbar shows the colors of each class. The group including Class “1” contains 82.35% pixels inside the acoustic shadowing. (c) The image corresponding to (a) processed by the RMM with the class number
, and the colorbar shows the colors of each class. The group including Class “1” and Class “2” contains 97.74% pixels inside the acoustic shadowing. (d)
. It corresponds to (a) in polar coordinates, and the red curve is the maximum intensity curve (MIC). (e)
. It corresponds to (c) in polar coordinates. (f)
. The white region is
, and the blue curve is
.
Figure 3.
contains the acoustic shadowing and part of the calcified plaque. The column coordinates of four vertical dashed lines from left to right are
,
,
,
, respectively. (b) The subregion composed of
and
extracted from (a). And the region between the the green dashed rectangle and the red curve (MIC) is
. (c) The cost function of
and
, and their gap is the MIC in (b). The yellow curves are the optimal paths acquired by the graph searching algorithm in
and
, respectively. (d) The yellow curve is the detected calcified plaque in polar coordinate. (e) The yellow curve is the detected calcified plaque in Cartesian coordinate.
Figure 4.
Some results of the detection of the calcified plaque.
()-(
) are original IVUS images. (
)-(
) are the results of our method corresponding to (
)-(
), respectively, where the region within the yellow contour is the calcified plaque. (
)-(
) are the results of the manual drawing method by a cardiologist corresponding to (
)-(
), respectively, where the region within the red contour is the calcified plaque.
Figure 5.
The white “×” represents the catheter center.
The region within the yellow closed curve represents the detected calcified plaque. The yellow curve “a” and “b” are the leading edge and the trailing edge of the calcified plaque. The region between and
(two blue dashed lines) represents the angular location of the plaque. AL is angular length of the red dash line. AC is the mean of
and
. PA is the area within the yellow closed curve. PT is the mean distance between the curve “a” and the curve “b”. DC is the mean distance between the curve “a” and the catheter center.
Table 1.
The results of distinguishing between the IVUS images with and without the calcified plaque.
Figure 6.
The results of the linear regression with respect to AL, AC, PA, PT and DC for all patients.
The horizontal axis and vertical axis represent results acquired from our method and the manual drawing, respectively.
Figure 7.
The between-patient results of our method separately from Patient 1 to Patient 8 with respect to AL, AC, PA, PT and DC.
The left five columns represents the results of the linear regression. The right five column represents the results of the Bland-Altman analysis, where the blue dashed lines and the green dashed lines indicate the location of MEAN and 2
STD, respectively.
Figure 8.
The Bland-Altman plot with respect to AL, AC, PA, PT and DC for all patients.
The blue dashed lined and the green dashed lines indicate the location of MEAN and 2
STD, respectively.
Table 2.
The results of the linear regression.
Table 3.
The results of the Bland-Altman analysis.
Table 4.
The results of the overlapping rate between the calcified plaques detected by our method and drawn by manual.
Table 5.
The computing time of the proposed method is formulated as mean standard deviation measured by the second.
Figure 9.
The left and right yellow points represent the points with coordinate and
, respectively.
The red curve and the green curve are and
, respectively. The region below
is
.
is the number of pixels inside the intersection between the blue dashed rectangle and
.
is the number of pixels inside the intersection between the red dashed rectangle and
.