DOI:10.2214/AJR.05.0147
AJR 2006; 187:389-397
© American Roentgen Ray Society
Visualization of Normal Pulmonary Fissures on Sagittal Multiplanar Reconstruction MDCT
Koji Takahashi1,2,
Brad Thompson2,
William Stanford2,
Yutaka Sato2,
Kenichi Nagasawa1,
Hiroaki Sato1,
Makoto Kubota1,
Ayako Kashiba1 and
Hiroyuki Sugimori1
1 Department of Radiology, Asahikawa Medical College and Hospital, 2-1-1-1
Midorigaowa-higashi, Asahikawa, 078-8510 Japan.
2 Department of Radiology, University of Iowa College of Medicine, Iowa City, IA
52242.
Received January 28, 2005;
accepted after revision March 23, 2005.
Address correspondence to K. Takahashi
(taka1019{at}asahikawa-med.ac.jp).
Abstract
OBJECTIVE. Delineation of the interlobar fissures on multiplanar
reconstruction (MPR) images is useful to assess masses at the fissures for
invasion into adjacent lobes. We performed this study to determine the
appropriate MDCT protocol to visualize the interlobar fissures on sagittal MPR
images.
MATERIALS AND METHODS. For the phantom studies, radiographic film
was used to replicate the interlobar fissures. For the clinical studies, we
obtained MDCT scans of 130 patients with normal interlobar fissures.
Visualization of the interlobar fissures on sagittal MPR was assessed using
the following scanning parameters: scan collimations of 0.5, 1, 2, and 3 mm
with helical pitches of 1 and 1.5 for the phantom studies; and scan
collimations of 0.5, 1, 2, and 3 mm with a helical pitch of 1.5 and a scan
collimation of 2 mm with a helical pitch of 1 for the clinical studies.
RESULTS. To visualize fissures as a sharp line, a 0.5- or 1-mm
collimation was required for the major fissure and 0.5 mm for the minor
fissure in the phantom studies. In the clinical studies, 0.5-mm-collimation
MPR images depicted interlobar fissures as a sharp line in all cases. Fissures
on MPR images using 1-, 2-, and 3-mm collimations appeared as a sharp line in
77.5-95.0%, 0-43.3%, and 0% of cases, respectively.
CONCLUSION. Volume data obtained using a 1-mm collimation are
required to visualize all the interlobar fissures as a sharp line on sagittal
MPR images except the minor fissure and superior portion of the right major
fissure, for which a 0.5-mm collimation is required.
Keywords: chest lung lung cancer MDCT pleura pulmonary nodules
Introduction
Two-dimensional multiplanar reconstruction (MPR) is the most frequently
used reconstruction technique for helical CT scans. The benefits of using MPR
have been reported in the assessment of thoracic diseases, including central
airway lesions [1,
2], central pulmonary embolism
[3], mediastinal
lymphadenopathy [4], and
diaphragmatic rupture [5,
6]. Reports indicate that
high-resolution MPR images obtained with a 0.5- or 1-mm collimation depict
normal anatomy and lung disease in a manner similar to axial or direct coronal
high-resolution CT images
[7-9].
The interlobar fissure is an important landmark for assessing the location
and distribution of pulmonary disease. In patients with lung tumors,
assessment of tumor extension across the interlobar fissure is critical in
staging the disease, assessing the feasibility of surgical resection, and
deciding whether lobectomy or pneumonectomy will be required
[10]. Quint et al.
[10] reported poor
sensitivities in detecting transfissural tumor extension on contiguous axial
CT images obtained with a 10-mm slice thickness. However, with a collimation
of less than 2 mm, the interlobar fissures appear as a hyperattenuating line
[11,
12], and some investigators
have indicated that the use of thin-section CT scans could improve accuracy in
identifying tumor extension across the major fissure
[10,
11,
13].
For identification of the interlobar fissures, we postulated that using
sagittal images is more accurate than using axial images to assess the major
fissures along their entire craniocaudal length. We believe the same
hypothesis to be true for identification of the minor fissure because it lies
perpendicular to the longitudinal axis of the thorax. However, researchers
have not previously reported, to our knowledge, the appropriate MDCT protocol
with which to visualize the interlobar fissures on sagittal MPR images.
Materials and Methods
Phantom Studies
Initially, a phantom study was performed to assess the visibility of
interlobar fissures on sagittal MPR images. To replicate the interlobar
fissures, we used radiographic film (200 µm in thickness) tilted 30° to
the z-axis to represent the major fissure and placed another film
nearly perpendicular to the scanning z-axis to represent the minor
fissure. The phantom images were obtained on a 4-MDCT scanner (Aquilion,
Toshiba) using the following protocol: 0.5-mm collimation with a 0.5-mm
reconstruction interval; 1-mm collimation with a 0.5-mm reconstruction
interval; 2-mm collimation with a 1-mm reconstruction interval; and 3-mm
collimation with a 1.5-mm reconstruction interval.
To evaluate the visibility of the major fissure, scans were obtained at
pitches of 1 and 1.5, a 0.5-second gantry rotation, 120 kV and 50 mA, a
high-frequency algorithm, a 30-cm field of view, and a 512 x 512 matrix.
For assessment of the minor fissure, the same parameters were used except a
15-cm field of view and 256 x 256 matrix. Once scanning had been
performed, sagittal MPR images with a 1.0-mm slice thickness were generated
from the scan data. The MPR images were photographed separately on hard copies
with a window width of 1,600 H and a window level of -600 H.

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Fig. 1A Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as sharp line with no stairstep
artifact on images obtained using 0.5-mm collimation (A and B)
and 1-mm collimation (C and D) and pitch of 1 or 1.5.
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Fig. 1B Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as sharp line with no stairstep
artifact on images obtained using 0.5-mm collimation (A and B)
and 1-mm collimation (C and D) and pitch of 1 or 1.5.
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Fig. 1C Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as sharp line with no stairstep
artifact on images obtained using 0.5-mm collimation (A and B)
and 1-mm collimation (C and D) and pitch of 1 or 1.5.
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Fig. 1D Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as sharp line with no stairstep
artifact on images obtained using 0.5-mm collimation (A and B)
and 1-mm collimation (C and D) and pitch of 1 or 1.5.
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Fig. 1E Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as slightly thick line with no
and mild stairstep artifact on images obtained using 2-mm collimation at pitch
of 1 (E) and 1.5 (F).
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Fig. 1F Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as slightly thick line with no
and mild stairstep artifact on images obtained using 2-mm collimation at pitch
of 1 (E) and 1.5 (F).
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Fig. 1G Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as significantly thick line with
mild and severe stairstep artifact on images obtained using 3-mm collimation
at pitch of 1 (G) and 1.5 (H).
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Fig. 1H Sagittal multiplanar reconstruction images of phantom major
fissure. Phantom major fissure is visualized as significantly thick line with
mild and severe stairstep artifact on images obtained using 3-mm collimation
at pitch of 1 (G) and 1.5 (H).
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Fig. 2A Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as thin line with no and mild stairstep artifact on
sagittal images using 0.5-mm collimation at pitch of 1 (A) and 1.5
(B).
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Fig. 2B Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as thin line with no and mild stairstep artifact on
sagittal images using 0.5-mm collimation at pitch of 1 (A) and 1.5
(B).
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Fig. 2C Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as slightly thick line on images obtained using 1-mm
collimation at pitch of 1 (C) and 1.5 (D).
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Fig. 2D Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as slightly thick line on images obtained using 1-mm
collimation at pitch of 1 (C) and 1.5 (D).
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Fig. 2E Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as significantly thick line on images obtained with 2-mm
collimation at ptich of 1 (E) and 1.5 (F) and 3-mm collimation
at pitch of 1 (G) and 1.5 (H).
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Fig. 2F Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as significantly thick line on images obtained with 2-mm
collimation at ptich of 1 (E) and 1.5 (F) and 3-mm collimation
at pitch of 1 (G) and 1.5 (H).
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Fig. 2G Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as significantly thick line on images obtained with 2-mm
collimation at ptich of 1 (E) and 1.5 (F) and 3-mm collimation
at pitch of 1 (G) and 1.5 (H).
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Fig. 2H Sagittal multiplanar reconstruction (MPR) images of phantom
minor fissure. On MPR images with 1-, 2-, and 3-mm collimation, stairstep
artifact was mild at pitch of 1 and severe at pitch of 1.5. Phantom minor
fissure is visualized as significantly thick line on images obtained with 2-mm
collimation at ptich of 1 (E) and 1.5 (F) and 3-mm collimation
at pitch of 1 (G) and 1.5 (H).
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We assessed the thickness of the visualized phantom fissures and the
presence and degree of stairstep artifact on these images using the following
criteria: thickness was graded as a thin line, a slightly thick line, or a
significantly thick line; and stairstep artifact was graded as none, mild, or
severe. The thickness of the fissures was graded in comparison with the
phantom fissure on conventional axial images obtained using a 0.5-mm
collimation; the grades were defined as follows: thin when the thickness of
the fissures was equal to that on the axial phantom images, slightly thick
when it was slightly thicker than on the axial phantom images, and
significantly thick when it was considerably thicker than on the axial phantom
images. The images were initially assessed independently by two pulmonary
radiologists, and the final decision was made by consensus in cases for which
there was interobserver disagreement.
Clinical Studies
The study was approved by the institutional review board, and informed
consent was not required or obtained to review the CT studies.
To determine the appropriate MDCT scanning parameters with which to
visualize normal interlobar fissures on sagittal MPR images, we performed a
retrospective review of CT studies of 130 patients obtained for clinical
reasons during the period from January 2003 to June 2004. We used a 4-MDCT
scanner (Aquilion, Toshiba) and obtained sagittal MPR images of the interlobar
fissures in five groups of subjects using different scan collimations and
helical pitches: 0.5-mm collimation with a 0.5-mm reconstruction interval at a
pitch of 1.5 in 20 patients, 1-mm collimation with a 0.5-mm reconstruction
interval at a pitch of 1.5 in 20 patients, 2-mm collimation with a 1-mm
reconstruction interval at a pitch of 1 in 30 patients, 2-mm collimation with
a 1-mm reconstruction interval at a pitch of 1.5 in 30 patients, and 3-mm
collimation with a 1.5-mm reconstruction interval at a pitch of 1.5 in 30
patients.
Images were obtained using 120 kV and 150 mAs, 0.5-second gantry rotation,
30-cm field of view, 512 x 512 matrix, and a high-frequency
reconstruction algorithm. Sagittal MPR images with a 3-, 2-, and 1-mm
collimation were obtained from clinically indicated standard chest CT studies
and those with a 0.5-mm collimation, from patients in whom high-resolution CT
was clinically indicated. We excluded patients with incomplete fissures;
diffuse lung disease; focal lesions adjacent to the interlobar fissures;
pleural effusions; pleural abnormalities; cardiomegaly; and thoracic
deformity, including scoliosis and pectus excavatum. The patient population
included 74 men and 56 women who ranged in age from 34 to 71 years (mean, 48
years). There was no significant difference in sex and age among the five
groups with different scan collimations and helical pitches. We obtained
bilateral sagittal MPR images of the interlobar fissures of 1-mm thickness
with 10-mm intervals and photographed both on hard copies with a window width
of 1,600 H and a window level of -600 H.
We assessed the visibility of the interlobar fissures on sagittal MPR
images using the following criteria: sharp line, blurred line, and inadequate
visualization. We judged the fissure to be a sharp line when it appeared
similar to that on conventional axial images with a 1-mm collimation in 10
healthy subjects as a control group. We judged the fissure to be blurred when
it appeared as a thick line with marginal blurring or when there was a
stairstep artifact, and we judged the fissure to be inadequately visualized
when it appeared as a hypo- or hyperattenuating band devoit of
vascularity.
We reviewed sagittal MPR images at the midportion of the thorax on the
right side and 10-15 mm lateral to the cardiac margin on the left. Because the
angle of the major fissure along its longitudinal axis differs between levels
above and below the hilum, we assessed its conspicuity at regions both
superior and inferior to the hila. We also assessed the visibility of the
right minor fissure. All images were independently reviewed by two pulmonary
radiologists who were blinded to the collimation and pitch of the images.
Interobserver variation of the score between the two reviewers was assessed
using kappa statistics. Kappa values were defined as the following: 0-0.20,
poor; 0.21-0.40, fair; 0.41-0.60, moderate; 0.61-0.80, good; and 0.81-1,
excellent.
Results
Phantom Studies
The Phantom major fissure was visualized as a thin line with no stairstep
artifact on sagittal MPR images obtained using 0.5- and 1-mm collimation at
pitches of 1 and 1.5; as a slightly thick line with no and mild stairstep
artifact on MPR images using a 2-mm collimation at pitches of 1 and 1.5,
respectively; and as a significantly thick line with mild and severe stairstep
artifact on MPR images obtained using a 3-mm collimation at pitches of 1 and
1.5, respectively (Figs. 1A,
1B,
1C,
1D,
1E,
1F,
1G, and
1H).
The phantom minor fissure was visualized as a thin line with no stairstep
artifact on the sagittal MPR images using a 0.5-mm collimation at pitches of 1
and 1.5. It was visualized as a slightly thick line on MPR images obtained
with a 1-mm collimation and as a significantly thick line on images obtained
with 2- and 3-mm collimation. Stairstep artifact on MPR images obtained using
a 1-, 2-, and 3-mm collimation was mild at pitch of 1 and severe at pitch of
1.5 (Figs. 2A,
2B,
2C,
2D,
2E,
2F,
2G, and
2H).
Clinical Studies
Interobserver agreement in the quality criteria of the interlobar fissures
on MPR images was excellent in all portions of the interlobar fissures:
= 0.96 in the right superior major fissure,
= 0.90 in the
right inferior major fissure,
= 0.88 in the left superior major
fissure,
= 0.90 in the left inferior fissure, and
= 0.86 in
the minor fissure.
The mean percentages of the two reviewers for each criterionthat is,
sharp line, blurred line, and inadequate visualizationin the assessment
of the right superior and inferior major fissures, the left superior and
inferior major fissures, and the minor fissure are shown in
Table 1.
Discussion
For visualization of the interlobar fissures on axial CT images, the most
significant factors affecting their appearance and conspicuity are partial
volume averaging from the adjacent lung tissue; the thinness of the fissures;
and their anatomic course, which is oblique to axial scanning planes. To
overcome problems with volume averaging and to visualize the interlobar
fissures as a hyperattenuating line, a thin collimation (generally <2 mm)
is required on conventional axial scanning
[11,
12]. However, to assess the
entire interlobar fissures, the use of thin-collimation scans results in an
excessive number of a axial images. Alternatively, a 25° cranially tilted
axial scan can provide the same benefit in visualization of the major fissure,
which appears as a linear of bandlike density, and can do so even with a 5- to
10-mm collimation [13].
However, this method is generally impractical and undesirable for routine
scanning.

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Fig. 3A Sagittal multiplanar reconstruction images obtained with each
of scanning parameters show typical appearance of interlobar fissures in five
patients. Upper and lower portions of right major fissure and minor fissure
are visualized as sharp line on images obtained using 0.5-mm collimation in
57-year-old woman (A) and 1-mm collimation in 62-year-old man
(B) at pitch of 1.5.
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Fig. 3B Sagittal multiplanar reconstruction images obtained with each
of scanning parameters show typical appearance of interlobar fissures in five
patients. Upper and lower portions of right major fissure and minor fissure
are visualized as sharp line on images obtained using 0.5-mm collimation in
57-year-old woman (A) and 1-mm collimation in 62-year-old man
(B) at pitch of 1.5.
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Fig. 3C Sagittal multiplanar reconstruction images obtained with each
of scanning parameters show typical appearance of interlobar fissures in five
patients. Upper and lower portions of right major fissure and minor fissure
are visualized as blurred line (arrows) on images obtained using 2-mm
collimation at pitch of 1 in 55-year-old man (C) and at pitch of 1.5 in
68-year-old woman (D).
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Fig. 3D Sagittal multiplanar reconstruction images obtained with each
of scanning parameters show typical appearance of interlobar fissures in five
patients. Upper and lower portions of right major fissure and minor fissure
are visualized as blurred line (arrows) on images obtained using 2-mm
collimation at pitch of 1 in 55-year-old man (C) and at pitch of 1.5 in
68-year-old woman (D).
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Fig. 3E Sagittal multiplanar reconstruction images obtained with each
of scanning parameters show typical appearance of interlobar fissures in five
patients. Upper and lower portions of right major fissure and minor fissure in
51-year-old man are visualized as hyperattenuating band (arrows) on
image obtained using 3-mm collimation at pitch of 1.5.
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With the recent advent of MDCT and especially with the increases in the
number of data acquisition channels and with the thinner detector collimation,
MDCT can now readily provide high-resolution MPR images of the lung from
nearly isovoxel volume data. Honda et al.
[7] reported that coronal MPR
images obtained using a 0.5-mm collimation can provide image quality similar
to that of direct coronal thin-section CT scans for the evaluation of normal
pulmonary structures, including the interlobar fissures, on autopsy lung
specimens.
Recently, the authors of two studies reported that coronal MPR images
obtained from helical scan data with a thin collimation (0.5-1 mm) and axial
high-resolution CT images were comparable for the evaluation of lung
parenchymal abnormalities [8,
9]. In both studies, the
authors indicated that MPR images depict the features and distribution of
parenchymal abnormalities as accurately as axial high-resolution CT images.
Arakawa et al. [8] reported
that MPR images provided additional information to that provided by axial
high-resolution images in 22% of cases, especially for the presence and
distribution of ground-glass opacities, intralobular reticular opacities, and
bronchial dilatation. Remy-Jardin et al.
[9] suggested that the
significantly reduced numbers of images provide additional benefit as a
diagnostic algorithm when using MPR. On the basis of these studies, we thought
that sagittal MPR images obtained from thin-collimation volume data would be
suitable for assessment of the interlobar fissures (Figs.
3A,
3B,
3C,
3D,
3E,
4A,
4B, and
4C).

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Fig. 4A Poor visualization of upper major fissure and minor fissure
on sagittal multiplanar reconstruction images in three patients. Image
obtained using 1-mm collimation at pitch of 1.5 shows that lower portion of
right major fissure in 60-year-old man appears as sharp line, whereas its
upper portion and minor fissure appear as blurred line (arrow).
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Fig. 4B Poor visualization of upper major fissure and minor fissure
on sagittal multiplanar reconstruction images in three patients. Image
obtained using 2-mm collimation at pitch of 1 shows that lower portion of
right major fissure in 48-year-old woman appears as sharp line, whereas its
upper portion and minor fissure appear as blurred line (arrows).
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Fig. 4C Poor visualization of upper major fissure and minor fissure
on sagittal multiplanar reconstruction images in three patients. Image
obtained using 2-mm collimation at pitch of 1.5 shows that lower portion of
right major fissure in 66-year-old man appears as blurred line, whereas its
upper portion and minor fissure appear as hypoattenuating band
(arrows).
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Storto et al. [14] assessed
the value of MPR images for the detection of neoplastic extension across the
major and minor fissures. They obtained MPR images from single-detector
helical scans with a 2-mm collimation and pitches of 1 and 1.5. In their
study, the visibility of the interlobar fissures on MPR images was good,
represented as a sharp hyperattenuating line in 78.4% of patients; acceptable,
as a bandlike opacity with marginal blurring, in 13.7%; and poor, as
insufficient visualization for diagnosis, in 7.8%. They also assessed
transfissural extension of tumors on MPR images using the following two
criteria for potential fissural neoplastic invasion: the presence of a mass on
both sides of the fissure and neoplastic lobulations extending across the
fissural plane. They reported that the two criteria yielded a high diagnostic
accuracy with a sensitivity and specificity of 100% and 92.8%, and 100% and
100% for the major and minor fissures, respectively
[14]. However, the interlobar
fissures on MPR images appeared indistinct with marginal blurring and were
considered similar to the blurred line group from our criteria. Furthermore,
the number of subjects in their analysis was small: seven cases with invasion
and 14 cases without invasion in the assessment of the major fissure and eight
with invasion and four without invasion in that of the minor fissure. We agree
with their statement that sagittal MPR images are useful in evaluating a lung
mass at the fissures for invasion into adjacent lobes. However, we believe
that MPR images obtained using a 2-mm collimation would be suboptimal in
detecting subtle changes reflecting transfissural tumor extension and that the
use of a thinner collimation would provide a better morphologic representation
of the interlobar fissures on MPR images and thereby augment the assessment of
abnormalities of the fissure, adjacent lung, or both.
In clinical studies, a 0.5-mm-collimation scan revealed both the major and
minor fissures as a sharp line in all cases. A 1-mm-collimation scan depicted
fissures as a sharp line in more than 90% of cases except for the superior
portion of the right major fissure and the minor fissure, for which only a
sharp line was seen in 82.5% and 77.5% of the cases, respectively. This
difference is thought to be due to the more horizontal orientation of these
fissures, which results in significant partial volume averaging and stairstep
artifact. MPR images obtained using 2- and 3-mm collimation were considered to
be suboptimal for visualizing the fissures because of marginal blurring and
frequent nonvisualization as a line, respectively.
Limitations in our data are the lack of clinical study of the diagnostic
accuracy of sagittal MPR images for assessing abnormalities of the interlobar
fissures, including transfissural tumor extension. However, we have found that
clear visualization of the interlobar fissures on high-resolution MPR images
is beneficial in the evaluation of adjacent lesions (Figs.
5A,
5B,
6A, and
6B). Another clinical study is
ongoing in an attempt to clarify the benefit of high-resolution MPR
images.

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Fig. 5A 72-year-old man with lung cancer in superior segment of right
lower lobe. Sagittal multiplanar reconstruction (MPR) image obtained using
0.5-mm collimation at pitch of 1.5 shows tumor abutting and retracting major
fissure but not involving minor fissure.
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Fig. 5B 72-year-old man with lung cancer in superior segment of right
lower lobe. MPR image obtained using 2-mm collimation at pitch of 1.5 does not
clearly show anatomic relationship between tumor and interlobar fissures.
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Fig. 6A 69-year-old man with lung cancer in anteromedial basal
segment of left lower lobe. Sagittal multiplanar reconstruction (MPR) image
obtained using 1-mm collimation at pitch of 1.5 shows neoplastic lobulations
extending fissural plane (arrows).
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Fig. 6B 69-year-old man with lung cancer in anteromedial basal
segment of left lower lobe. MPR image obtained using 2-mm collimation at pitch
of 1.5 does not clearly show relationship between tumor margin and fissural
plane.
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An additional limitation is that our data were obtained using a 4-MDCT
scanner. Currently, 64-MDCT scanners are in use commercially. With this
increase in the number of slices, CT images may deteriorate due to "cone
beam" artifact, which is not compensated for by MDCT reconstruction
algorithms in 4-MDCT scanner systems that use relatively narrow cone beam
angles. However, cone beam artifact can be minimized using a modified
volumetric CT reconstruction technique in MDCT scanners with more than 16
tracks [15]. In future
configurations, interpolation algorithms for MDCT will likely use
z-axis deconvolution to further improve longitudinal spatial
resolution [16]. In studies
using MDCT scanners, the detector collimation should be selected on the basis
of the coverage desired and taking into account the thinnest slice thickness
needed for retrospective reconstruction. We think our data are useful in
determining a scanning protocol for visualization of the interlobar fissures
on sagittal MPR images.
In conclusion, 1-mm-collimation volume data are required to visualize all
the interlobar fissures as a sharp line on sagittal MPR images except the
minor fissure and the superior portion of the right major fissure, for which a
0.5-mm collimation is required.
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