Soft and Intermediate Plaques in Coronary Arteries: How Accurately Can We Measure CT Attenuation Using 64-MDCT?
Jun Horiguchi1,
Chikako Fujioka1,
Masao Kiguchi1,
Yun Shen2,
Christian E. Althoff3,4,
Hideya Yamamoto5 and
Katsuhide Ito3
1 Department of Clinical Radiology, Hiroshima University Hospital, 1-2-3,
Kasumi-cho, Minami-ku, Hiroshima, 734-8551, Japan.
2 CT Lab of Great China, GE Healthcare, Mongkok Kowloon, Hong Kong.
3 Department of Radiology, Division of Medical Intelligence and Informatics,
Programs for Applied Biomedicine, Graduate School of Biomedical Sciences,
Hiroshima University, Hiroshima, Japan.
4 Present address: Institute of Radiology, Universitaetsmedizin-Charité
-Berlin, Berlin, Germany.
5 Department of Molecular and Internal Medicine, Division of Clinical Medical
Science, Programs for Applied Biomedicine, Graduate School of Biomedical
Sciences, Hiroshima University, Hiroshima, Japan.
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Fig. 2 —Graph shows eight heart rate sequences that were programmed
in phantom: sequence 1, 50 beats per minute (bpm); sequence 2, 65 bpm;
sequence 3, 80 bpm; sequence 4, 95 bpm; sequence 5, 50 bpm with shifting;
sequence 6, 65 bpm with shifting; sequence 7, 80 bpm with shifting; and
sequence 8, 95 bpm with shifting.
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Fig. 3 —Coronary artery plaque models. This drawing shows plaque
size, plaque shape, and stenosis levels of coronary artery plaque models.
Seven plaques were prepared with different combinations of plaque shape,
plaque CT attenuation, and coronary artery diameter, respectively: D-shaped,
40 H, 4 mm; D-shaped, 40 H, 3 mm; centric, 40 H, 4 mm; centric, 40 H, 3 mm;
eccentric, 40 H, 4 mm; D-shaped, 100 H, 4 mm; and centric, 100 H, 4 mm.
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Fig. 4 —Balloon phantom. Seven plaque models were attached to balloon
phantom (mimicking heart) and were surrounded by water. Balloon was filled
with mixture of water and contrast medium (CT attenuation = 40 H).
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Fig. 5A —Region-of-interest (ROI) setting in coronary artery plaque.
Drawing shows typical ROI placement (dotted lines) in coronary artery
plaques (gray). All ROIs were ovoid and 1 mm2. ROIs were
set at center of plaques in theme 2 (A), near arterial lumen and at
center of plaque in theme 3 (B), at center of plaques in three stenotic
levels in theme 4 (C), and at center of plaques in various types of
plaque shape and coronary artery diameters in theme 5 (D).
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Fig. 5B —Region-of-interest (ROI) setting in coronary artery plaque.
Drawing shows typical ROI placement (dotted lines) in coronary artery
plaques (gray). All ROIs were ovoid and 1 mm2. ROIs were
set at center of plaques in theme 2 (A), near arterial lumen and at
center of plaque in theme 3 (B), at center of plaques in three stenotic
levels in theme 4 (C), and at center of plaques in various types of
plaque shape and coronary artery diameters in theme 5 (D).
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Fig. 5C —Region-of-interest (ROI) setting in coronary artery plaque.
Drawing shows typical ROI placement (dotted lines) in coronary artery
plaques (gray). All ROIs were ovoid and 1 mm2. ROIs were
set at center of plaques in theme 2 (A), near arterial lumen and at
center of plaque in theme 3 (B), at center of plaques in three stenotic
levels in theme 4 (C), and at center of plaques in various types of
plaque shape and coronary artery diameters in theme 5 (D).
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Fig. 5D —Region-of-interest (ROI) setting in coronary artery plaque.
Drawing shows typical ROI placement (dotted lines) in coronary artery
plaques (gray). All ROIs were ovoid and 1 mm2. ROIs were
set at center of plaques in theme 2 (A), near arterial lumen and at
center of plaque in theme 3 (B), at center of plaques in three stenotic
levels in theme 4 (C), and at center of plaques in various types of
plaque shape and coronary artery diameters in theme 5 (D).
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Fig. 6A —Relationship of CT attenuation values between plaque and
intracoronary enhancement. Graphs show results for soft (A) and
intermediate (B) plaques. Repeated measures analysis of variance
revealed that CT attenuation values of soft plaque were different among
intracoronary artery enhancement levels (p < 0.01) and
combinations of heart rates and reconstruction algorithms (p <
0.01). Scheffé test for multiple pairwise comparisons revealed that CT
attenuation values were significantly different between intracoronary
enhancement of 150 and 350 H (p < 0.01), 150 and 450 H (p
< 0.01), and 250 and 450 H (p < 0.01) on static cardiac phantom
using half reconstruction and between intracoronary enhancement of 150 and 350
H (p < 0.01), 150 and 450 H (p < 0.01), 250 and 350 H
(p < 0.01), and 250 and 450 H (p < 0.01) on cardiac
phantom at 50 beats per minute (bpm) using half reconstruction algorithm.
Scheffé test revealed that CT attenuation values of plaque on
intracoronary artery enhancement of 150 H were significantly different between
static cardiac phantom with half reconstruction algorithm and 65 bpm with half
reconstruction (p < 0.01) and between 50 bpm with half
reconstruction and 65 bpm with half reconstruction (p < 0.01).
Scheffé test also revealed that CT attenuation values of plaque on
intracoronary artery enhancement of 250 H were significantly different between
static phantom with half reconstruction and 65 bpm with half reconstruction
(p < 0.01) and between 50 bpm with half reconstruction and 65 bpm
with half reconstruction (p < 0.01). In contrast, CT attenuation
values of intermediate plaque were not statistically different based on
intracoronary artery enhancement level (p = 0.09) or combinations of
heart rate and reconstruction algorithm (p = 0.10).
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Fig. 6B —Relationship of CT attenuation values between plaque and
intracoronary enhancement. Graphs show results for soft (A) and
intermediate (B) plaques. Repeated measures analysis of variance
revealed that CT attenuation values of soft plaque were different among
intracoronary artery enhancement levels (p < 0.01) and
combinations of heart rates and reconstruction algorithms (p <
0.01). Scheffé test for multiple pairwise comparisons revealed that CT
attenuation values were significantly different between intracoronary
enhancement of 150 and 350 H (p < 0.01), 150 and 450 H (p
< 0.01), and 250 and 450 H (p < 0.01) on static cardiac phantom
using half reconstruction and between intracoronary enhancement of 150 and 350
H (p < 0.01), 150 and 450 H (p < 0.01), 250 and 350 H
(p < 0.01), and 250 and 450 H (p < 0.01) on cardiac
phantom at 50 beats per minute (bpm) using half reconstruction algorithm.
Scheffé test revealed that CT attenuation values of plaque on
intracoronary artery enhancement of 150 H were significantly different between
static cardiac phantom with half reconstruction algorithm and 65 bpm with half
reconstruction (p < 0.01) and between 50 bpm with half
reconstruction and 65 bpm with half reconstruction (p < 0.01).
Scheffé test also revealed that CT attenuation values of plaque on
intracoronary artery enhancement of 250 H were significantly different between
static phantom with half reconstruction and 65 bpm with half reconstruction
(p < 0.01) and between 50 bpm with half reconstruction and 65 bpm
with half reconstruction (p < 0.01). In contrast, CT attenuation
values of intermediate plaque were not statistically different based on
intracoronary artery enhancement level (p = 0.09) or combinations of
heart rate and reconstruction algorithm (p = 0.10).
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Fig. 7 —Differences in CT attenuation values between
region-of-interest placement inside plaque. CT attenuation values of 250 and
350 H were chosen as representative levels from our clinical study results.
Wilcoxon's signed rank test revealed that CT attenuation values of plaque near
lumen (dark gray) were overestimated and higher than those at center
(light gray): soft plaque and intracoronary enhancement of 250 H,
soft plaque and 350 H, intermediate plaque and 250 H, and intermediate plaque
and 350 H (p < 0.01).
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Fig. 8 —Relationship between plaque CT attenuation values and
stenosis level. CT attenuation values of plaque between three stenotic
levels—that is, 25% (dark gray), 50% (light gray), and
75% (black) (in diameter). Kruskal-Wallis test revealed that CT
attenuation values of plaque were different between stenosis levels: soft
plaque and intracoronary enhancement of 250 H, soft plaque and 350 H,
intermediate plaque and 250 H, and intermediate plaque and 350 H (p
< 0.01).
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Fig. 9 —Plaque CT attenuation values in combinations of plaque shape
and coronary artery diameter. Kruskal-Wallis test revealed that CT attenuation
values of plaque were statistically different between combinations of soft
plaque and coronary artery enhancement of 250 H (gray) and soft
plaque and coronary artery enhancement of 350 H (black) (p
< 0.01).
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Copyright © 2007 by the American Roentgen Ray Society.
