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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3752_Библиотеки_им_академика_М_И_Перельмана
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Fig. 4.152 2-D double oblique views of the left atrium. Panel ( a ):
Relationship of the esophagus, left lower pulmonary vein and aorta.
Panel ( b ): Relationship between the left atrial appendage, left upper
pulmonary vein, and the ridge between these structures. In contradistinction to the right atrial appendage, the left atrial appendage is verin-
form or “wormlike” with a narrow ostium. The ridge between the left
atrial appendage and left upper pulmonary vein can be prominent and
misdiagnosed as an atrial mass. Ao aorta, LAA left atrial appendage,
LLPV left lower pulmonary vein, LUPV left upper pulmonary vein
abc
Fig. 4.151 Multimodal views of the left atrium. Panel ( a ): 3-D poste-
rior view of the left atrium. Panel ( b ): Endovascular view of the left
upper and lower pulmonary veins and the left atrial appendage. Panel
( c ): Endovascular view of the right upper and lower pulmonary veins.
LAA left atrial appendage, LLPV left lower pulmonary vein, LUPV left
upper pulmonary vein, RLPV right lower pulmonary vein, RUPV right
upper pulmonary vein
such as accessory atrial appendages and diverticulae. The
ridge between the left atrial appendage and left atrium,
sometimes referred to as the “Coumadin ridge” can be
prominent and misdiagnosed as an atrial mass.
The pulmonary veins can be assessed as they course to the
left atrium on the coronal and axial views, with subsequent
measurement of the pulmonary vein orifi ces made coaxially at
the interface of the left atrium and pulmonary vein using a double oblique approach. Multiple variations in pulmonary venous
anatomy occur, commonly with three right and two left pulmonary veins. Pulmonary veins can coalesce into a single trunk at
the atrial interface. Each vein should be followed from its origin in the lungs and assessment should be made for any evidence of anomalous pulmonary venous return.
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Right Ventricle
Similar to the right atrium, heterogeneous opacifi cation of
the contrast can occur in the right ventricle. Morphologic
features of the right ventricle include trabeculation of the
septum, moderator band, and non-adjacent location of the
tricuspid valve and pulmonary valve annuli as they are separated by the conus arteriosus, therefore creating right ventricular divisions into an infl ow, body, and outfl ow
(Fig. 4.153 ). When retrospectively-gated images are acquired
on an adequately opacifi ed right ventricle, volumetric assessment of size and function can be measured. The right ventricle though is ovoid in shape and therefore can be more
challenging to quantitate than the left ventricle.
Left Ventricle
Morphologic features of the left ventricle include a smoothwalled septum, adjacent location of the mitral valve and aortic valve annuli, and prominent papillary muscles (Fig. 4.154 ).
Assessment can be made for wall thinning as well as lipomatous metaplasia associated with myocardial infarction. The
ventricular septum can be assessed for continuity versus
presence of a ventricular septal defect with characterization
of location, shape, and size. The ventricle can be assessed for
thrombi and masses. For retrospectively gated studies, functional views can be reformatted for assessment of left ventricular volumes, wall thicknesses and thickening, myocardial
mass, regional wall motion and global ventricular function
(Fig. 4.155 , Video 4).
Valvular Structure and Function
On retrospectively-gated studies, aortic and mitral valve anatomy and motion including annular dimensions, valve leafl et
number, morphology, degree of calcifi cation, valve excursion, apposition, prolapse, valve area, and regurgitant orifi ce
can be assessed (Figs. 4.156 and 4.157 ). Additionally, large
vegetations or other masses, can be visualized. Functional
image sets can be formatted following the traditional echocardiographic views, with the ability to view motion
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Fig. 4.153 2-D double oblique views of the right ventricle. Panel ( a ):
Trabeculation of the septum and a moderator band ( black arrow ). Panel
( b ): Non-adjacent location of the tricuspid annulus ( single black arrow )
and pulmonic valve annulus ( double black arrows ), separated by the
conus, creating divisions into an infl ow, body, and outfl o w
Fig. 4.154 2-D double oblique view of the left ventricle with the
anatomic features of a smooth-walled septum ( black arrow ) and
continuity between the aortic and mitral valve annuli ( white arrows )
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Fig. 4.155 2-D retrospectively-gated end-diastolic and end-systolic short axis ventricular views used for assessment of wall thickness, volumes,
and ejection fraction
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Fig. 4.156 2-D contrast-enhanced double oblique aortic valve images. Panel ( a ): Trileafl et calcifi c aortic stenosis. Panel ( b ): Planimetry of aortic
valve area demonstrating severe aortic stenosis
through the entire cardiac volume in these views. Functional
views can also be viewed in oblique planes for dynamic
analysis of specifi c structures. Tricuspid and pulmonic
valve assessment requires adequate contrast opacifi cation
of the right heart for analysis. With prospectively gated
images more limited data related to valve morphology can
be obtained (Fig. 4.158 ).
Pericardium
The pericardium should be assessed for evidence of
regional or global thickening, calcifi cation, pericardial
effusion, and pericardial masses. This may be particularly
helpful in scenarios of posterior pericardial effusions,
where echocardiographic imaging may be more challeng-
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Fig. 4.157 2-D double oblique mitral valve images. Panel ( a ): Short axis view. Panel ( b ): 4 chamber view
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Fig. 4.158 2-D double oblique pulmonary valve images. Panel ( a ): Long axis view of right ventricular outfl ow tract. Panel ( b ): Coaxial view
showing the pulmonary valve regurgitant orifi ce. LV left ventricle, PA pulmonary artery, RA right atrium
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ing. Small pericardial effusion can be appreciated on coronal images with the fl uid layering in the pericardial space
just above the diaphragm. The HU cursor, if placed on the
effusion, can confi rm that the attenuation of the fl uid is
near water attenuation (0 HU).
Coronary Artery Assessment
Assessment of the coronary arteries requires a multimodal
approach to reconstruction and analysis. Prior to assessment
for coronary arterial atherosclerotic disease, the origin,
course and termination of each coronary artery should be
analyzed for coronary artery dominance and for anomalies.
Viewing the aortic root in the axial plane as a clock face, the
right coronary artery arises from the right sinus of Valsalva
at approximately 11:30 on the clock face and the left main
coronary artery arises off of the left sinus of Valsalva at
approximately 3:30 on the clock face (Fig. 4.159 ).” The right
coronary artery should be followed in the right AV groove,
the left anterior descending coronary artery in the anterior
interventricular groove and the left circumfl ex coronary
artery in the left AV groove with branches of each artery
coursing out of their respective grooves. The posterior
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Fig. 4.159 Axial Images demonstrating the normal location of the origins of the coronary arteries. Viewing the aortic root in the axial plane as
a “clock face,” the right coronary artery arises from the right coronary
sinus at approximately 11:30 on the “clock face” and the left main coronary artery arises off of the left coronary sinus at approximately 3:30 on
the “clock face.” Panel ( a ): 2-D axial view showing the origin of the left
main coronary artery ( arrow ). Panel ( b ): 2-D axial view showing the
origin of the right coronary artery ( arrow ). Panel ( c ): Thick maximal
intensity projection showing the origin of the left main and right coronary arteries ( arrows ). Panel ( d ): Thick maximal intensity projection
showing the origin of the left main and right coronary arteries ( arrows )
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descending artery can be visualized either from the right
coronary artery or circumfl ex in the posterior interventricular
groove, defi ning vessel dominance.
Anomalous coronary arteries can be characterized by
ostial location and morphology, course and termination. An
anomalous coronary artery can arise off of a shared ostium
with another coronary artery, as its own separate ostium, off
of another coronary artery, or off of another vascular structure such as the pulmonary artery. For a coronary artery off
of the contralateral aortic sinus, the course can be pre-pulmonic, inter-arterial, intra-septal, or retro-aortic. Termination
can occur in an anomalous myocardial vascular distribution
or into another arterial or venous vascular structure.
Beginning at the most cranial slices, maximum intensity
projections can be viewed at 5 mm slice thickness. These
thicker slices facilitate visualization of the longitudinal course
of the vessels, with one limitation being that the brightest
pixel dominates the image. Therefore, in the presence of
heavily calcifi ed segments, one might miss a non-calcifi ed
plaque causing a signifi cant narrowing of the coronary vessel.
Adjusting the slice thickness back to 0.5 mm, each coronary
artery segment can subsequently be followed, assessing for
the presence of calcifi ed, mixed, and non-calcifi ed plaque in
the vessels of mild, moderate, or severe grades. The coronary
artery calcium images should also be referenced, as they
demonstrate the presence and location of calcium without
contrast in the coronary arteries.
In the axial view, the vessels are visualized in the plane
of image acquisition. As previously mentioned, if the CT
system used does not provide true isotropic voxels due to
limited Z axis resolution, the axial view provides greater
resolution than other reconstructed planes. Each individual
artery should be followed through the cranial to caudal
axial slices rather than attempting to view multiple arteries
on one axial slice. The left main coronary artery, left anterior descending artery, circumfl ex coronary artery, and
right coronary artery are analyzed individually along with
their branches. A coronary arterial segment coaxial to the
axial plane will appear as a circle, while an artery coursing
perpendicular to the axial plane will appear linear. The limitation is that an arterial segment coursing in any other
direction will be out of plane and therefore challenging to
review. Therefore, other modalities including 2-D double
oblique and curved multiplanar reconstructions are
employed to follow the course of the arterial segment being
analyzed.
Double oblique views allow each coronary artery to be followed in plane coaxially throughout its course (Fig. 4.160 ).
Use of double oblique views allows the reader to follow the
course of each coronary artery, which is especially useful for
tortuous segments. The optimal assessment plane for the most
proximal segment of a coronary artery can be identifi ed in its
long and short axis and then rotated 360 degrees. The oblique
plane is then moved at small increments for serial assessment
of segments and branches from proximal to distal artery.
Curved multiplanar reformatted images are extremely
useful to evaluate an entire coronary artery in one view. The
reader can choose the plane of a specifi c artery which is
displayed as a “curved surface” from within the 3-D volume
(Fig. 4.161 ). With curved multiplanar reformatted views, a
centerline is created and the artery “straightened out” and
viewed as a cylinder. The software also creates cross sectional cuts of each coronary arterial segment of the cylinder,
with the ability to adjust the thickness of the cross sections.
The arterial segment of interest (coronary artery stenosis)
can be compared to the segments above and below it as a
reference. All other structures are automatically eliminated,
including the side branches, and separate reconstructions
can be rendered for every side branch. The long axis luminal
view can be rotated 360° around its central axis in order to
assess eccentric plaques and stenoses. With curved multiplanar reformatted images, the computer software could create
the appearance of a stenosis by following an area of dense
calcium rather than the center of the vessel lumen.
Additionally, the centerline can jump from the coronary
artery to follow an adjacent cardiac vein. The centerline
should therefore be viewed in order to ensure that it remains
within the center of the vessel of analysis.
abc
Fig. 4.160 2-D double oblique identifi cation of a segment of the left anterior descending coronary artery with long ( a , b ) and short axis ( c ) views
of the arterial segment
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The volume rendered technique relies on identifying all
pixels above a certain threshold with various degrees of
attenuation. The results are most similar in orientation to
invasive coronary angiography images (Figs. 4.162 and
4.163 , Videos 5 and 6). The coronary arteries are seen as
relatively smooth structures with other cardiovascular landmarks present. The image can be rotated, allowing the interpreter some fl exibility in visualizing the segment from
multiple angles. A stenotic coronary artery segment will
appear darker as well as narrowed on volume rendered
images. The 3-D volume rendered images in CCTA help in
identifi cation of coronary anomalies as well as to assess the
dominance of the coronary arterial tree. In patients with previous coronary artery bypass graft surgery, the origin of
grafts from the aorta can be counted and the courses followed to the native vessels. Stumps of occluded grafts can
also be easily identifi ed. As there are potential artifacts with
all these additional techniques, the thin axial slices should
always be used to confi rm or exclude any potential lesions
that might be seen with other reconstructions.
a b
Fig. 4.161 Curved multiplanar reformatted view of a left anterior descending coronary artery. ( a ) The left anterior descending coronary artery is viewed
as serial coaxial cross sections. ( b ) The centerline ( yellow line ) is used to determine the center of each arterial segment
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Fig. 4.162 3-D images of the right coronary artery ( arrows ) in the right
anterior oblique 30 degree/ caudal 0 degree view. Panel ( a ): Image with
skeletal structures. Panel ( b ): Image of heart and coronary arteries.
Panels ( c , d ): Images of coronary arteries with varying degree of trans-
parency of the heart. As opposed to invasive angiography, the left coronary artery is also visualized. CAU caudal, RAO right anterior oblique
Artifacts Affecting Assessment
of The Coronary Arteries
A spectrum of artifacts may limit interpretation of the coronary arteries. Recognition of artifacts related to acquisition
and reconstruction is important in order to avoid misinterpretation of coronary artery fi ndings.
Coronary Artery Artifacts Due to Contrast Dose
and Timing Relative to Image Acquisition
In the setting of right heart greater than left heart enhancement, the images may have been acquired too early after
contrast administration. This early acquisition of images
can also lead to the distal segments of the coronary arteries
not being opacifi ed, which can be misinterpreted as signifi cant stenosis or occlusion. Measurement of contrast density
and homogeneity at serial levels of the descending aorta can
be performed. If the HUs decrease signifi cantly as the aorta
descends, the distal coronary arteries may be poorly opacifi ed and more diffi cult to analyze. Additionally, inadequate
fl ushing of contrast out of the superior vena cava can cause
“streak artifact” potentially obscuring the mid right coronary artery.
Artifacts Due to Overlap of HU Attenuation
Between Coronary Artery Lumen and Other
Structures
Blooming artifacts can occur due to coronary artery or
cardiac calcification, stents, clips, wires, pacemakers,
implantable cardiac defibrillators and other radiopaque
implanted materials. The non- contrast coronary artery
calcium images can be used to assess for coronary artery
segments which may be problematic prior to analysis of
the CCTA images. Changing contrast level can diminish
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these artifacts, and viewing of thin slices can decrease
volume averaging artifact, but some arterial segment
evaluation may be non-diagnostic.
Coronary Artery Artifacts Due to Motion
Artifacts can occur due to patient motion, respiratory motion,
motion due to ectopic atrial and ventricular beats and other
arrhythmias, and cardiac/coronary artery motion (Fig. 4.164 ).
Respiratory and patient motion artifacts are well seen on sagittal views by viewing the sternum and other skeletal structures. In coronal images and sagittal reconstructions, multiple
stacks of images are viewed simultaneously, and therefore
thin collimation lines can be seen. If the data sets are not
aligned properly due to motion, step artifact can occur.
Cardiac motion is complex, with contraction from apex to
base as well as rotational movement of the heart during con-
traction. The motion of the right coronary artery is particularly complex and therefore images may appear blurred,
appear as a “cashew nut” like shape or appear as a complete
double image, depending on the phase of the R-R interval
chosen to view. All available phases of the R-R interval
should be assessed for each coronary artery segment with
motion artifact in order to choose the most optimal images
for analysis.
Coronary Artery Artifacts Due to 3-D
Reconstruction
Although the 3-D images are intuitive regarding the
gross location, orientation and relationships of the coronary arteries to cardiovascular structures, reconstruction can lead to the artifactual appearance of coronary
artery stenosis or obstruction. The automated editing
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Fig. 4.163 3-D images of the right coronary artery ( arrows ) in the left
anterior oblique 30°/ caudal 0° view. Panel ( a ): Image with skeletal
structures. Panel ( b ): Image of heart and coronary arteries. Panels ( c ,
d ): Images of coronary arteries with varying degree of transparency of
the heart. As opposed to invasive angiography, the left coronary artery
is also visualized. CAU caudal, LAO left anterior oblique
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Fig. 4.164 Coronary artery artifacts due to curved multiplanar reformats of a left anterior mammary artery graft to the left anterior descending coronary artery. Panel ( a ): Double image of the LIMA graft due to
motion ( arrow ). Panel ( b ): Areas of coronary artery discontinuity due
to motion ( white arrows ). Additional blooming artifacts due to surgical
clips are present ( black arrow )
software may have edited out too much of the artery or
left in overlying tissue obstructing view of the coronary
artery (Fig. 4.165 ). The variety of motion artifacts men-
tioned above can lead to the discontinuous appearance
of the artery. Intra-myocardial bridging can also appear
as coronary artery occlusion as the artery courses internal to the epicardium. Due to these issues related to 3-D
reconstruction, the volume rendered images are not
used as the primary modality to document the presence
of coronary artery stenoses.
Non-cardiovascular Structure
Additional assessment of appropriately windowed full fi eld
of view images need to be performed to assess: visceral
situs, skeletal structure, lung parenchyma, presence of tho-
racic masses, and assessment of abdominal structures
which may be in the fi eld of view. Assessment of the noncardiovascular structures in the fi eld of view should be performed by physicians with expertise in analysis of these
structures.
Conclusion
CCTA workstations and software provide multiple
modalities to assess cardiovascular structure and function. Although axial images are most commonly relied on
for fi nal interpretation, other planes and reconstruction
modalities, if used with a thorough knowledge of their
strengths and limitations, are important to analysis. The
employment of these modalities in an organized approach
coupled with an understanding of the spatial relationships
between cardiovascular structures allow for comprehensive diagnosis of cardiovascular pathology.
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