High-Resolution CT Using Multidetector CT Equipment
Evaluation of Image Quality in 11 Cadaveric Lungs and a Phantom
Osamu Honda1,
Takeshi Johkoh1,
Noriyuki Tomiyama1,
Takenori Kozuka1,
Naoki Mihara1,
Mitsuhiro Koyama1,
Seiki Hamada1,
Hiroaki Naito1,
Hironobu Nakamura1 and
Masayuki Kudo2
1
Department of Radiology, Osaka University Medical School, 2-2 Yamadaoka,
Suita, Osaka, 565-0871, Japan.
2
General Electric Yokogawa Medical Systems, 4-7-127 Asahigaoka, Hino, Tokyo,
191-0065, Japan.
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Fig. 1. —Bar graph shows image quality of multidetector
high-resolution CT (HRCT). Image quality of axial 1.25 mm x 4i (four
images per gantry rotation) mode on multidetector HRCT was equal to that of
single-detector HRCT in all cases (100%), although image quality of other
modes on multidetector HRCT was worse than that on singledetector HRCT. Total
number of readings was 22. Area with striped lines, level 1= single-detector
HRCT; gray area, level 2 = inferior to single-detector HRCT.
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Fig. 2. —Bar graph shows diagnostic efficacy of multidetector
high-resolution CT (HRCT). In one case (5%) with helical 1.25-mm high-speed
mode and four cases (18%) with helical 2.5-mm high-speed mode, diagnostic
efficacy of multidetector HRCT was slightly worse than that on single-detector
HRCT. Total number of readings was 22. Area of striped lines, level 1 =
sufficient for diagnosis; gray area, level 2 = insufficient for diagnosis.
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Fig. 3A. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Single-detector high-resolution CT scan with 1-mm
collimation reveals faint centrilobular nodule (arrow).
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Fig. 3B. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Multidetector CT scan with axial 1.25 mm x 4i (four
images per gantry rotation) mode reveals faint centrilobular nodule
(arrow). Compared with A, image quality is not degraded.
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Fig. 3C. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Multidetector CT scan with helical 1.25-mm high-quality
mode (pitch, 3:1) reveals faint centrilobular nodule (arrow).
Compared with A, image quality is not degraded.
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Fig. 3D. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Multidetector CT scan with helical 1.25-mm high-speed mode
(pitch, 6:1) shows faint nodule (arrow). Nodule is more indistinct
than nodule on axial 1.25 mm x 4i mode (B) and helical 1.25-mm
high-quality mode (C).
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Fig. 3E. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Multidetector CT scan with axial 2.5 mm x 2i (two
images per gantry rotation) mode shows faint nodule (arrow). Nodule
is more indistinct than nodule on multidetector CT with axial 1.25 mm x
4i mode (B).
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Fig. 3F. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Multidetector CT scan with helical 2.5-mm high-quality
mode shows faint nodule (arrow). Image quality of multidetector CT is
more indistinct than that of axial 2.5 mm x 2i mode (E), but is
still worthwhile.
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Fig. 3G. —Cadaver of 67-year-old man with tuberculosis. Lung was
inflated and fixed. Multidetector CT scan with helical 2.5-mm high-speed mode
shows faint centrilobular nodules (arrowhead). One of two observers
determined this case as insufficient for diagnosis.
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Fig. 4. —Graph shows standard deviation (SD) values of eight regions
of interest on multidetector high-resolution CT of phantom. Highest SD values
and lowest SD values are indicated with lines, and mean SD values are
indicated with points. There is no significant difference between SD values of
axial 1.25 mm x 4i (four images per gantry rotation) mode and those of
helical 1.25-mm high-quality mode on multidetector CT. However, there were
significant differences between SD values of axial mode and those of helical
high-quality mode (p<0.01), between those of axial mode and
helical high-speed mode (p<0.05), and between those of helical
high-quality mode and helical high-speed mode (p<0.01) of same
slice collimation. Noise of axial mode was larger than that of helical
high-quality mode, but smaller than that of helical high-speed mode on same
slice thickness.  = mean value.
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Fig. 5A. —Multidetector high-resolution CT images of phantom, including
acrylic spheres. Three numbered circles are regions of interest. Scan with
axial 1.25 mm x 4i (four images per gantry rotation) mode shows no
streak artifact.
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Fig. 5B. —Multidetector high-resolution CT images of phantom, including
acrylic spheres. Three numbered circles are regions of interest. Scan with
helical 1.25-mm high-quality mode (pitch, 3:1) shows no streak artifact.
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Fig. 5C. —Multidetector high-resolution CT images of phantom, including
acrylic spheres. Three numbered circles are regions of interest. Scan with
helical 1.25-mm high-speed mode (pitch, 6:1) shows streak artifacts that are
radiated from spheres (arrows).
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Fig. 5D. —Multidetector high-resolution CT images of phantom, including
acrylic spheres. Three numbered circles are regions of interest. Scan with
helical 2.5-mm high-speed mode shows prominent streak artifacts that are
radiated from spheres (arrows).
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Copyright © 2001 by the American Roentgen Ray Society.
