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Abdominal Aortic Aneurysms
Jeffrey S Legg, PhD, R.T.(R)(CT)(QM), FASRT
Lynn M Legg, MBA, R.T.(R)(M)
Abdominal aortic aneurysm
(AAA) is a significant disease
affecting the circulatory
system. Risk factors include
smoking, hypertension, sex,
and a possible hereditary
predisposition. AAAs remain
asymptomatic for years, and
various imaging methods
are used in their detection,
diagnosis, and treatment. This
article reviews the anatomy
and physiology of the aorta
as well as the signs and
symptoms, pathophysiology,
epidemiology, and risk factors
for the development of AAA.
The use of ultrasonography
and other imaging modalities
for pre- and post-treatment is
discussed, as is endovascular
aortic repair.
This article is a Directed
Reading. Your access to
Directed Reading quizzes
for continuing education
credit is determined by
your membership status
and CE preference.
After completing this article, the reader should be able to:
 Describe aortic anatomy.
 State the preventive screening recommendations for abdominal aortic aneurysm (AAA).
 Identify the most common locations of AAA occurrence.
 Recall the preferred imaging modalities for AAA and their specific applications.
 Discuss treatments for AAA.
T
he aorta is the largest artery in
the human body. Originating
from the left ventricle, it
extends into the chest and
down into the abdomen. The vessel is
the main conduit for distributing oxygenated blood from the heart to the
body. Abdominal aortic aneurysm
(AAA) is a localized enlargement within the abdominal cavity.
Anatomy and Physiology
The aorta is the major artery of
the body carrying oxygenated blood
from the heart through the thoracic
and abdominal cavities of the body
(see Figure 1). The aorta attaches
superiorly to the left ventricle. Blood is
pumped through the aorta with every
left ventricular contraction. A 3-leaflet
valve at the junction of the left ventricle
and aorta (aortic valve) prevents retrograde flow of blood into the ventricle.1
The aorta is divided into 4 sections: ascending aorta, aortic arch,
thoracic aorta, and abdominal aorta.
The ascending aorta, which rises
superiorly from the left ventricle, is
RADIOLOGIC TECHNOLOGY, November/December 2016, Volume 88, Number 2
Brachiocephalic
Left carotid
Subclavian
Aorta
Celiac
Superior
mesenteric
Adrenal
Renal
Inferior
mesenteric
Iliac
Figure 1. Pathway of the aorta from the heart to
the iliac artery bifurcation. © ASRT 2010.
approximately 3 cm in diameter but can
vary depending on patient sex, age, and
size. At the root of the ascending aorta
are 3 anatomical dilatations called the
aortic sinuses. From the left and right
aortic sinuses arise the left and right
coronary arteries, respectively. The
coronary arteries vascularize the heart
(see Figure 2). The posterior sinus has
no coronary artery.2
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Abdominal Aortic Aneurysms
The aorta enters the abdominal cavity
through the diaphragm and then divides into
2 major vessels: common iliac arteries and
the median sacral artery. Important branches
of the abdominal aorta are the lumbar and
Brachiocephalic
artery
musculophrenic arteries, renal and suprareAortic arch
nal arteries, and arteries that vascularize the
abdominal viscera, such as the celiac trunk and
the superior and inferior mesenteric arteries.2
Ascending aortaa
Generally, all arteries have 3 layers. The
layers of the aorta are composed of smooth
muscle, nerves, intimal cells, and extracellular
Decending aorta matrix. The aortic wall is divided into 3 layers
(thoracic)
Left coronary artery
rteryy
(from external to lumen): tunica externa (or
tunica adventitia), tunica media, and tunica
intima (see Figure 3). The vascular supply to
Right coronary artery
the tunica externa and tunica media is proAortic sinuses
vided by an extensive network of small blood
vessels known as the vasa vasora.2
Blood flows through the aorta in pulses
due to contraction of the left ventricle. The
Figure 2. Aortic arch and its associated arteries. © ASRT 2016.
elasticity of the aorta allows it to expand and
contract as the heart pumps blood through
it. The tunica media contains collagen and
As the aorta rises superiorly from the heart, it makes
elastin filaments that allow it to stretch and contract in
a downward curve, which is known as the aortic arch.
response to the pulsatile flow of blood, assisting in the
The aortic arch often is visible on chest radiographs;
propulsion of blood through the circulatory system. For
from it arises arteries supplying blood to the head,
neck, and upper limbs—the brachiocephalic artery
(which bifurcates to form the right subclavian artery
and right common carotid artery), left common carotid
artery, and left subclavian artery. The aortic arch also
Endothelium
has function in homeostasis, containing barorecepTunica intima
Basement
tors and chemoreceptors that send information about
membrane
carbon dioxide levels and blood pH to the medulla
Tunica media
2,3
oblongata.
Beyond the aortic arch, the aorta descends caudally,
which is called the descending aorta. The descending
Tunica externa
aorta is divided into 2 parts based on location. The
initial section of the aorta that passes through the mediastinum and chest is called the thoracic aorta. Many
branches originate from the thoracic descending aorta,
including intercostal and subcostal arteries, bronchial
arteries, and branches that supply blood to the esophaFigure 3. Layers of the aortic wall. © ASRT 2016.
gus, mediastinum, pericardium, and diaphragm.2
Left common
carotid artery
146
Left subclavian
artery
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example, as the left ventricle contracts
(systole), blood is forced into the aorta,
which expands. This distention provides
the potential energy that helps to maintain blood pressure during diastole.2,3 The
aorta’s elastic recoil also helps the heart
conserve energy. The pressure of the
blood through the aorta, termed the pulse
pressure, equals systolic pressure minus
diastolic pressure.
The measure of the pressure of blood
flow through the aorta is called mean
arterial pressure (MAP), often abbreviated
as Pmean. MAP is a measure of the cardiac
output, systemic vascular resistance, and
central venous pressure. MAP is highest
Normal aorta
Abdominal aortic
at the aorta and decreases across the ciraneurysm
(infrarenal)
culatory system as the aorta branches into
arteries and then into arterioles, capillarFigure 4. Diagram of an abdominal aortic aneurysm (AAA) as compared to a normal
ies, and veins.3
aorta. © ASRT 2016.
Measuring the velocity of the blood
pulse wave also aids in assessing aortic
Prevalence
function. Pulse wave velocity (PWV) is a measure of
AAAs are the most common arterial aneurysm, with
aortic stiffness and can be measured invasively via flow
approximately 80% occurring below the renal arteries at
meters or catheter-based pressure probes in patients
the area of aortic bifurcation.8 Studies of adults 50 years
undergoing cardiac catheterization, 4,5 or noninvasively
6
and older indicate an AAA prevalence of 3.9% to 7.2%
with ultrasonography. The aorta stiffens with age,
in men and 1.0% to 1.3% in women.9,10 Worldwide, the
which results in increased5:
prevalence is higher in western countries than in Asiatic
¡ Blood pressure.
countries, and higher in Australia than in the United
¡ Risk of developing blood pressure-related diseases
States and Europe.11 If diagnosed before becoming sympand pathologies.
tomatic, an AAA can be treated and cured. However, a
¡ Correlation with cardiovascular events and morruptured AAA is considered a medical emergency, with
tality.
a 59% to 90% mortality rate if it occurs outside a hospital
Pathophysiology
environment.9,12 The operative mortality for AAA, defined
In general, an AAA is a focal, localized enlargeas death regardless of cause occurring within 30 days
ment (dilatation) of a section of the abdominal aorta
after surgery,13 is approximately 40%.9 Mortality rates for
of 3.0 cm or greater, or when the diameter of the
elective (ie, nonemergency) AAA repair are significantly
dilatation is 50% larger than normal (see Figure 4).7
lower, ranging from 0.6% to 5.3%.14-16 Therefore, careful
Dilatation of the aortic wall occurs when the tunica
screening to detect AAAs and followup when diagnosed
media weakens. The pulsating force of the blood
are necessary, specifically with at-risk patients.
through the aorta causes the tunica intima and externa
The diameter of the aneurysm influences the potento stretch and expand. As the vessel wall layers progrestial for rupture. For AAAs 3.0 cm to 3.9 cm in diameter,
sively weaken, the aneurysm continues to enlarge, often
the annual risk for rupture is negligible. The risk is 1%
resulting in a fatal rupture.
for aneurysms that are between 4.0 cm and 4.9 cm, and
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increases to 11% for those that are between 5.0 cm and
5.9 cm.7,15 The majority of deaths from ruptured AAAs
are found among men 65 years or older; for women,
most deaths occur after age 80 years.7,15
Risk Factors
The etiology of AAA is unknown; however, several
risk factors are associated with an increased incidence.
One significant risk factor is smoking.17-20 The risk of
AAA development increases with the number of cigarettes smoked daily and the number of years smoking.17-21
Singh et al posited that an individual’s number of years
smoking is the critical risk factor.21 Occasional, past,
short-term tobacco use also was found to increase the risk
of AAA,22 although this risk decreased over time after
cessation of smoking.23
Many studies include high blood pressure and
chronic hypertension (systolic  160 mm Hg; diastolic
 95 mm Hg) as risk factors.17,24,25 However, conflicting evidence exists over whether the risk of AAA from
hypertension is gender specific. Analysis by Forsdahl
et al, for example, indicated that the risk exists only in
women.26 In addition, the prevalence of AAA among
men older than 50 years of age is 4 to 6 times greater
than that of women of the same age.21,27-31 Interestingly,
AAAs appear to develop 10 to 15 years later in women
than in men. The peak prevalence of AAA in men is
5.9% at ages 80 to 85 years. However, among women
the peak prevalence is 4.5% at 90 years or older.32
A hereditary link for the development of AAAs has
been hypothesized, prompting studies into the effects
of genetics on AAA development among twins and
other close relatives.33,34 Results from the Swedish Twin
Registry, which contains data on twins in Sweden
since 1886, indicated that monozygotic twins (ie, 2
offspring developed from a single fertilized ovum) had
a 24% probability of having an AAA if the other twin
had one. 33 Another study indicated that a positive family history of AAA in a first-degree relative increases
the risk of aortic aneurysm by up to a factor of 10.35
Research continues in an attempt to determine the specific genes associated with AAA development.36
Signs and Symptoms
Because AAAs are asymptomatic until they expand
enough to press on local organs or rupture, they can go
148
undetected for years. Similarly, the rate of AAA expansion
is difficult to predict. The most common presentation of a
nonruptured AAA is vague, yet persistent and deep, back
and abdominal pain that might extend to the flanks and
groin. A pulsatile pain might be felt around the umbilicus;
however, this pain often is noticeable only on examination.
The symptoms of a ruptured AAA are more significant, yet still ambiguous. These include pain in
the abdomen or back and can be confused with renal
calculus, diverticulitis, or herniation. This severe pain
might appear suddenly, be constant, or spread to the
groin, buttocks, legs, or scrotum. Tachycardia and dizziness on standing also is common. Other symptoms
include syncope, loss of consciousness, sweaty/clammy
skin, nausea, and vomiting. Internal bleeding from a
ruptured AAA can result in hypovolemic shock with
symptoms such as hypotension, cyanosis, skin mottling,
and altered mental status. These symptoms are serious
considering that nearly 65% of patients with a ruptured
AAA die of sudden cardiovascular collapse.37
Medical imaging plays an important role in the diagnosis, surveillance, treatment, and follow up for AAA.
Because the majority of AAAs are asymptomatic, their
initial diagnosis might be an incidental finding during
imaging.
Screening and Surveillance
The U.S. Preventive Services Task Force (USPSTF)
is an independent panel of experts in primary care and
prevention that systematically reviews the evidence of
effectiveness and develops recommendations for clinical preventive services. The USPSTF offers separate
AAA screening recommendations for men and women.
For a man aged 65 to 75 years who has smoked 100 or
more cigarettes in his lifetime, the Task Force recommends one-time screening. 38 For this group, it also
recommends clinicians be selective when counseling
those in the same age cohort who have never smoked
because the benefit for screening is small. For male
nonsmokers, the individual and his physician(s) should
base their decision on the individual’s medical and family history, other risk factors, and personal values. The
USPSTF does not recommend routine AAA screening
for female nonsmokers, regardless of age, because the
evidence about its benefit is insufficient.38
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arteries), and distal (above the iliac bifurcation) sections
of the aorta (see Figure 5).39
The Society for Vascular Ultrasound recommends use of duplex instrumentation that displays
2-D structures and motion in real-time and Doppler.
Recommendations for spectral analysis and color
Doppler imaging include42:
 Proper sample volume size and positioning.
 An angle of 60° or less with respect to the vessel
wall and direction of blood flow.
 Measurement of spectral velocities.
 Imaging carrier frequency between 2.25 MHz
and 4.0 MHz as needed for penetration.
 Doppler carrier frequency of 2.5 MHz to
4.0 MHz as needed for penetration.
AAAs should be measured in the anteroposterior
dimension, and the greatest dimension should be
reported. 39
Aortic diameters smaller than 3.0 cm are considered normal, and they require no further screening
or surveillance. According to Lederle et al, small to
medium-sized AAAs (3.0-5.4 cm) should undergo
surveillance and follow up.20 Aneurysms in the 3.0-cm
to 3.9-cm range require a conservative management
approach that seeks to slow the growth of the AAA.
Aneurysms in this range are at risk for enlarging and
should be monitored every
2 to 3 years. Medium-sized
A
B
aneurysms (4.0-5.4 cm)
should be monitored every
6 months. AAAs 5.5 cm or
larger require treatment.20
Regardless of surveillance frequency, life-long
control of risk factors,
such as smoking, hypertension, hyperlipidemia,
and diabetes, is necessary.
Pharmacotherapy might be
required. The role of beta
blockers, used to control
Figure 5. Ultrasound images of AAA in transverse (A) and longitudinal (B) views. Calipers size the
hypertension, in reducing
AAA at 60.3 mm and 51.9 mm in the transverse and longitudinal views, respectively. Reprinted with
AAA growth and improvpermission from Brekken R, Dahl T, Hernes TA. Ultrasound in abdominal aortic aneurysm. In:
ing health outcomes is
Grundmann R, ed. Diagnosis, Screening and Treatment of Abdominal, Thoracoabdominal and
questionable.9
Thoracic Aortic Aneurysms. Rijeka, Croatia: InTech; 2011:103-124.
However, recommendations differ. The American
College of Cardiology and the American Heart
Association, for example, suggest screening for men
60 years and older who have a first-degree relative with
AAA.50 The American Society for Vascular Surgery and
the European Society for Vascular Surgery advocate for
screening for all men 65 years and older, regardless of
smoking history. Both vascular surgery societies also
recommend screening for women who are considered
high risk based on smoking or family history.10,38,39
Color duplex ultrasonography is the recommended
tool for AAA screening.38 Advantages include high sensitivity and specificity for AAA, low cost, availability, short
examination time, patient acceptance, and no radiation
exposure.40,41 Recommendations for screening ultrasonography for the abdominal aorta are promoted in a joint
resolution by the American College of Radiology (ACR),
the American Institute of Ultrasound in Medicine, and
the Society of Radiologists in Ultrasound.39 These organizations formed a consensus group that advocates use of
real-time scanners using transducers that allow for appropriate penetration and resolution.39 Suggested parameters
include longitudinal (along the long axis of the aorta) and
transverse images (perpendicular to the long axis of the
aorta) that include the proximal (inferior to diaphragm,
near the celiac artery), mid (near the level of the renal
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Pretreatment Planning
Computed tomography angiography (CTA) is considered the preferred imaging surveillance method for
pre- and post-endovascular aneurysm repair (EVAR)as
well as for postopen surgical repair.43-45 Figure 6 depicts a
Figure 6. Sagittal maximum intensity projection computed
tomography (CT) demonstrating infrarenal AAA. Reprinted with
permission from Higashigaito K, Schmid T, Puippe G, et al. CT
angiography of the aorta: prospective evaluation of individualized
low-volume contrast media protocols. Radiology. 2016:151982.
150
sagittal CT scan demonstrating a sizeable infrarenal AAA.
Chaer recommends obtaining 2.5 mm or smaller slices of
the abdomen and pelvis using 3-D reconstruction.46 This
method allows for accurate measurements perpendicular
to the true axis of the aorta. Three-dimensional aortic
measurements are more accurate than 2-D measurements
and aid sizing of the graft (see Figure 7).46,47
Anatomic considerations from preoperative imaging include aneurysm morphology and measurements.
Examples of important aortic measurements for sizing
an endograft include aortic neck 46,48:
 Diameter at the most caudal renal artery branch.
 Length, or distance from most caudal renal artery
to the origin of the aneurysms.
 Angulation, or angle formed between points connecting the lowest renal artery, the origin of the
aneurysm, and the aortic bifurcation.
Figure 8 illustrates several AAA measurements as
described by Goshima et al.49 The various measurements allow for accurate sizing of the stent-graft and
aids in placement.
Figure 7. CT reconstruction of an AAA (arrows). Reprinted with per-
mission from Bakerstmd under a Creative Commons license. https://
commons.wikimedia.org/wiki/File:AneurysmAortaWithArrows.jpg.
Accessed October 4, 2016.
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Aortic neck diameter
Aortic neck diameter 15 mm
distal to the lowest renal artery
Aortic neck length
Lowest renal artery to
aortic bifurcation length
Lower renal to right
internal iliac artery length
Aneurysm diameter
Aortic bifurcation
diameter
Lower renal to left internal iliac artery length
Left common iliac
artery diameter
Right iliac artery sealing
lengths
Left iliac artery sealing
lengths
Right common
iliac artery
diameter
Right external
iliac artery
diameter
Left external
iliac artery
diameter
Figure 8. Schematic of various measurements of aorta and aneurysm for proper stent siz-
ing and placement. Reprinted with permission from Goshima S, Kanematsu M, Kondo H,
et al. Preoperative planning for endovascular aortic repair of abdominal aortic aneurysms:
feasibility of nonenhanced MR angiography versus contrast-enhanced CT angiography.
Radiology. 2013;267(3):948-955. doi:10.1148/radiol.13121557.
CTA imaging parameters vary by institution; however,
many acquire both contrast enhanced and noncontrast
enhanced images of the abdomen. Figure 9 demonstrates
a transverse CTA with the AAA sized at 5.43 cm  3.6
cm.50 Nonenhanced images are obtained to evaluate the
degree of calcification in the aortoiliac wall and are important for planning access.44 This calcification increases the
stress on the aortic wall and decreases the stability of the
AAA.51 Picel and Kansal offer an example of contrastenhanced CT imaging parameters.44 Their institution
uses 100 mL of nonionic contrast agent injected at a rate
of 4 mL/s to 5 mL/s. Thin sectional images are obtained
RADIOLOGIC TECHNOLOGY, November/December 2016, Volume 88, Number 2
from the base of the lungs to the
symphysis pubis, timed to a bolus
tracking at the celiac trunk of
150 HU over the baseline.
Magnetic Resonance
Angiography
Magnetic resonance angiography (MRA) with gadolinium is an
alternative for pre-EVAR planning
in patients for whom iodinated
contrast is contraindicated.43,44
However, because nephrogenic
systemic fibrosis (a rare syndrome
involving fibrosis to internal organs,
skin, and joints) is linked to gadolinium-based contrast agents and
anaphylactic reactions, evaluation
of renal function prior to MRA contrast is recommended.44 MRA has a
lower sensitivity (ie, ability to identify true positive cases) than does
CTA to detect small blood vessels
and renal arteries with diameters
smaller than 2 mm. For pre-EVAR
planning, the ACR recommends
T1- and T2-weighted spin-echo
image sequences for assessing
aneurysm morphology and relevant vascular anatomy.43 The use
of noncontrast MRA sequences
are gaining acceptance but should
be performed only in centers with
expertise in the technique.43
Other Modalities
Unlike CTA and MRA, neither digital subtraction
angiography nor ultrasonography are recommended
for pre-EVAR measurements. Specifically, digital subtraction angiography is limited by measurement errors
arising from parallax and magnification, and it cannot
evaluate the true aortic lumen diameter. 46
Treatment
Various options are available for treating AAAs,
including endovascular and open surgery, and
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Table 1
AAA Size and Rupture Risk38
Diameter (cm)
Rupture Risk (%/year)
4
0
4-4.9
1
5-5.9
5-10
6-6.9
10-20
7-7.9
20-40
8
30-50
a
a
Figure 9. CT angiogram of abdomen and pelvis with the trans-
verse section demonstrating a 54.3 mm  36.0 mm (5.43 cm
3 3.6 cm) aneurysm. Reprinted with permission from Moole H,
Emani VK, Ramashai S. Mycotic aneurysm in a turtle hunter:
brief review and a case report. J Community Hosp Intern Med
Perspect. 2015;5(3);27229. doi:10.3402/jchimp.v5.27229.
important factors for any treatment are aneurysm size
and risk of rupture (see Table 1). The enlargement rate
of AAAs varies; some increase steadily, others increase
rapidly, and about 20% remain the same size indefinitely. 52 The typical expansion rate is 0.3 cm to 0.4 cm
per year.
Elective Treatment
Two types of treatment for AAAs are available:
open surgical repair and endovascular aneurysm repair
(EVAR). Although physician clinical decision-making
is outside the scope of this article, factors typically
considered include mortality rates, complications, and
balance of short- vs long-term benefits (eg, risk of reintervention with EVAR vs open repair).
Surgical repair of AAAs in the 4.0-cm to 5.4-cm
range has not reduced mortality rates compared to
periodic surveillance.20 However, for aneurysms
larger than 5.5 cm, open surgical intervention is recommended if the perioperative and postoperative
complications are lower than the estimated risk of
rupture. 52 Additional indications for elective surgery
include increase in size by more than 0.5 cm within 6
months, regardless of size.
152
Elective surgical repair should be considered for aneurysms  5 cm.
Open Repair
Open repair is the traditional approach for treating
AAAs. Once open repair is decided upon, imaging is
used to identify anatomical variants to guide treatment
and prevent unexpected complications. 53 Open repair is
conducted under general anesthesia, and a large incision
is made either transperitoneally or retroperitoneally
to access the abdominal aorta. Research indicates
no significant differences in outcome between the 2
approaches54-56; thus, the choice of approach might be
based on patient body habitus, patient preference, the
surgeon’s experience and preference, or a combination
of these factors.53
The affected portion of the aorta is resected and
replaced with a synthetic graft (see Figure 10). If the
AAA involves the iliac arteries, the synthetic graft is
extended to include those vessels. An aneurysm proximal to the renal arteries results in the arteries being
reimplanted into the graft, or the creation of a bypass
graft.53 Aortic replacement graft materials include
polyester (eg, Dacron), polytetrafluoroethylene, and
autogenous vein; woven polyester most commonly is
used. Important qualities in graft material include ease
in handling, durability, and appropriate porosity. 53 The
diameter of the selected graft should match the aortic
diameter; the diameter of a graft usually is smaller than
the diameter of an endograft used in the same location,
if endovascular management is elected.53
Endovascular Aneurysm Repair
EVAR is less invasive than open repair and consists
of interventional radiology or surgical placement via the
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A
Open Repair
Abdominal
aorta
Blood flows
through graft
Aneurysm
Graft sewn
in place
B
Endovascular Stent Graft Repair
Blood flows
through graft
Abdominal
aorta
No flow in
aneursym sac
Endovascular
stent graft in
place
Figure 10. Open (A) and endovascular stent-graft (B) repairs of
aortic aneurysm. Reprinted with permission from Eidt JF. Open
surgical repair of abdominal aortic aneurysm. UpToDate Web
site. http://www.uptodate.com/contents/open-surgical-repair
-of-abdominal-aortic-aneurysm. Revised July 11, 2016. Accessed
March 9, 2016.
common femoral artery of an endovascular stent-graft
or endograft. The endograft is delivered via a catheter
in a folded and compressed manner. The external
iliac artery should be 7 mm at minimum to accept the
delivery sheath.46 Upon deployment, the endograft
expands to exclude the aneurysm sac from aortic blood
flow and blood pressure and protects against further
AAA expansion.46 Preoperative imaging and planning
is crucial to determine patient eligibility and endograft
selection. A variety of endograft types are available
RADIOLOGIC TECHNOLOGY, November/December 2016, Volume 88, Number 2
from various manufacturers. Stents typically are made
of nitinol, Elgiloy, or stainless steel (see Figure 11).43
Complications of EVAR include infection, thrombosis, incorrect placement of the graft (ie, kinking,
angulation), graft migration, and endoleaks (ie, the flow
of blood into the aneurysm sac after graft placement).57
EVAR requires more frequent imaging followup than
does open repair.
Ruptured AAA Repair
A ruptured AAA is defined as a bleeding outside
of the wall of the aneurysm that requires immediate
treatment, as the condition nearly always is fatal 52;
death usually occurs within hours. 58,59 The mortality rate from ruptured AAAs during open repair is
approximately 50%; EVAR has a lower mortality
rate—between 20% and 30%. 52 Although outcomes
can improve with EVAR over open repair, the
emergent nature of a ruptured AAA creates major challenges. For example, most medical institutions are not
equipped to treat ruptured AAAs with EVAR. In addition, patients experience better outcomes undergoing
a procedure at the institution to which they are first
admitted; a 17% to 19% increase in mortality has been
reported when patients are transferred to another facility for open repair. 60,61
Specific to AAA, additional imaging reconstruction
techniques are used to obtain accurate measurements. Multiple vendors supply software that allow for
semiautomated measurements of vessel diameter and
length in relation to the proximal and distal margins
of the aneurysm. Three-dimensional analysis includes
volume rendering, maximum-intensity projection, and
curved planar reformations. 43,44 Benefits of reformatted and reconstructed images include more accurate
pretreatment measurements. 63 Three-dimensional
volume rendering provides excellent depiction and
precise measurement of any angulation in tortuous
AAAs. 44
Post-treatment Imaging
Imaging after AAA treatment is routine to detect issues
or complications with the graft, which can include endoleak and fistula formation, as well as to monitor aneurysm
size.44,64-66 The timing of follow-up imaging varies with
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Aptus, Inc.
¡Aptus
Gore & Associates
¡Excluder
Cook Medical
¡Zenith
¡ Xenith Flex
¡ Zenith LP
Lombard
¡Aorfix
Cordis Corporation
¡Incraft
Medtronic, Inc.
¡AneuRx
¡Talent
¡Endurant
Trivascular
¡Ovation
Endologix
¡Powerlink
¡Nellix
Vascutek
¡Anaconda
Figure 11. AAA stent-graft families. Reprinted with permission from HMP Communications. Criado FJ. EVAR 2012: indications, devices,
and techniques. http://www.vasculardiseasemanagement.com/content/evar-2012-indications-devices-and-techniques. Published May 29,
2012. Accessed March 9, 2016.
the type of treatment employed. For example, in patients
who underwent open repair, a CT scan is recommended
within 5 years to detect aneurysm degeneration involving
the pararenal aorta, iliac arteries, endograft, or anastomotic
sites.43 However, compared to open repair, EVAR requires
more frequent imaging follow up. Post-EVAR contrastenhanced CT is recommended at the 1-, 6-, and 12-month
marks—as well as for lifelong annual surveillance44,46—
and is the ACR’s suggested imaging modality of choice.43
The primary goal of post-EVAR is to evaluate the integrity
of the stent-graft, including evaluation for migration, kinking, structural failure, and endoleak (see Figure 12).44
Decreasing aneurysm sac size is evidence of a well-functioning stent-graft. Volume analysis of the aneurysm sac
is recommended by the ACR because it entails all dimensions of the AAA.43,68-69
Abdominal CTA techniques for post-EVAR patients
vary between institutions, but imaging parameters can
include43:
154
 Single arterial phase.
 Biphasic (ie, noncontrast CT and either the arterial phase, or arterial and delayed phases).
 Triphasic (noncontrast CT, arterial phase, and
delayed phases).
Iezzi et al recommend that a 90-ml to 130-ml bolus of
contrast be administered at a rate of 3 ml/s to 4 ml/s
during the arterial phase. 66 Bolus-tracking software is
used to delay the scan until a 100-HU change develops
in the opacification of the aorta. Delayed phase images
are acquired after the arterial phase, typically 60 to
120 seconds after the initial contrast material injection.
Postprocessing includes maximum-intensity project
and volume rendering. 44 Because of the frequency of CT
scans for post-EVAR follow-up, radiation dose reduction methods should be employed.
Although MRA is an appropriate alternate to CTA,
it is less accurate for assessing the metallic components of the endograft, which might induce artifacts.43
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invasiveness and use of contrast. 43 Digital subtraction
angiography is less sensitive than CTA in detecting
endoleaks, but its ability to assess the direction of blood
flow makes it more accurate in classifying endoleaks.43
Figure 12. Transverse CT angiogram of abdomen and pelvis
post-EVAR treatment. Note the metallic stent surrounding the
aorta (arrow). Note: this is the same patient from Figure 9.
The stent-graft is in the correct location and shows no sign of
endoleaks. Reprinted with permission from Moole H, Emani VK,
Ramashai S. Mycotic aneurysm in a turtle hunter: brief review
and a case report. J Community Hosp Intern Med Perspect.
2015;5(3);27229. doi:10.3402/jchimp.v5.27229.
According to the ACR, the following imaging results
have been found for the various endograft elements43:
 Nitinol (nickel and titanium alloy) – causes
relatively few MR artifacts and allows for visualization of the stent lumen and adjacent structures;
considered the best candidates for MRA.
 Elgiloy (alloy of cobalt, chromium, and nickel) –
might cause significant artifacts and compromise
visualization of the stent-graft lumen while allowing visualization of the adjacent structures.
 Stainless steel – might cause significant artifacts
similar to Elgiloy.
Despite potential artifact issues, MRA has been found
highly sensitive to endoleaks. In addition, MR images can
be reformatted for volume and diameter measurements.43
Duplex ultrasonography also is used in post-EVAR
follow up and is recommended as an adjunct to noncontrast CT. 43 Sandford et al recommend the use of
contrast enhancement to improve post-EVAR scanning.35 Angiography is, at best, “a second-line imaging
modality in post-EVAR patients” because of its
RADIOLOGIC TECHNOLOGY, November/December 2016, Volume 88, Number 2
Dose Reduction
Dose reduction during CT and CTA is important
considering patients will undergo a lifetime of surveillance following EVAR. A variety of techniques
and methods has been employed to reduce radiation
dose, including automatic exposure control, change in
technical parameters, iterative reconstruction, and dualenergy CT. Use of automatic tube current modulation
(or automatic exposure control) can reduce radiation dose by up to 50%.70 Automatic exposure control
systems available for some of the major CT scanner
manufacturers are listed in Table 2.70 Similarly, decreasing tube voltage also reduces dose.71 A dose reduction of
approximately 33% results from a decrease from 120 kV
to 100 kV.72 However, Raman states that changing the
kV is a rarely used option because of a potential increase
in image noise and that technologists and radiologists
must appraise a variety of factors individually to determine whether a lower kV is appropriate.70
Increasing the pitch has been demonstrated to reduce
radiation dose in a retrospective study of thoracolumbar
Table 2
Automatic Exposure Control Systems Available
From Major Manufacturers61
Vendor
System Name(s)
Parameter Explanation
GE
AutomA; SmartmA
Measure of image quality/
noise level defined related
to uniform water phantom
Philips
Dose Right
Image quality expressed
in terms of noise level of
an existing optimal clinical
image
Siemens
CARE Dose 4D
mAs that would be used for
an average-sized patient
Toshiba
SUREExposure 3D
Standard deviation of pixel
values in an image (higher
standard deviation 
higher noise)
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CTAs.73 In comparing high-pitch (3.4) to standardpitch (0.8) CTA examinations with all other imaging
parameters identical, very little difference in arterial
attenuation, signal-to-noise ratio, or contrast-to-noise
ratio was found. Although noise consistently was higher
in high-pitch scans, radiation dose reductions between
45% and 50% were achieved with similar diagnostic
quality. In addition, considerably less contrast media was
required to obtain the same arterial attenuation.73
Relatedly, a radiation dose reduction is possible in
CTA using a lower iodine concentration contrast media
with a resultant kV decrease. The benefit of reduced
iodine concentration is avoidance of contrast-induced
acute kidney injury, an abrupt deterioration in renal
function associated with iodinated contrast use also
known as contrast-induced nephropathy.74 However,
low-iodine contrast media resulted in poor vascular
attenuation, image quality, and diagnostic accuracy.75,76
Although not a direct evaluation of AAA imaging, a
2015 study by Shen et al assessed the image quality
of the aorta using dual-source CT with a lower-thantypical concentration of iodinated contrast (270 mg I/
mL vs 370 mg I/mL).77
Patient's scans using a pitch of 3.2, and a tube voltage of 100 kV and 20 mA were acquired as compared to
the typical 120 kV scans. Objective image quality was
evaluated by comparing mean aortic, signal-to-noise,
and contrast-to-noise ratios. Results indicated no significant differences in these quality parameters except for
more image noise among low-iodine scans. A subjective
image evaluation by 2 radiologists also found no significant differences in the scanning techniques. However,
radiation exposure—as measured by CT dose index
volume and dose length product—was 34.3% less when
using low-iodinated contrast and lower tube voltage.77
Thus, reduced tube voltage should be considered a feasible dose-reduction strategy.
Dose reduction also arises from using dual-energy
CT. This technique entails the simultaneous acquisition
of CT data using 2 different energy levels that result in
different degrees of photon attenuation. As a result, contrast can be subtracted from CTA to create nonenhanced
images, thus negating the nonenhanced CT scan mentioned previously. This technique reportedly decreased
dose by nearly 20%.78
156
Larger dose reductions were reported by Buffa et al in
their comparison of single-phase dual-energy CT to conventional CTA.79 Each patient underwent a single-energy
nonenhanced scan, an arterial phase, and a delayed
phase. The delayed phase began 30 seconds after the
arterial phase using the dual-source mode. The researchers found that the effective dose from the dual-energy
mode acquisition (delayed phase) was 40.3% less than
the 2 scans in the single-energy mode (ie, nonenhanced
and arterial phases). An estimated dose reduction of
61.7% was achieved when the dual-energy acquisition
was compared to a single-source, triple-phase CTA (ie,
noncontrast and 2 arterial phase scans).79
Iterative reconstruction—or more accurately, statistical iterative reconstruction—is a data reconstruction
method that improves on the commonly used filtered
back-projection in CT. Iterative reconstruction allows
for lower radiation dose via lower tube potentials and
current levels without the increase in image noise
common in filtered back-projection. In iterative reconstruction algorithms:
[P]rojection data are predicted based on an
assumption about the initial attenuation coefficients
of all voxels. These predicted data are compared to
measured projection data, and the voxel attenuation
values are modified until an acceptable level of error
between the predicted and measured data is achieved.62
Prognosis
The data are mixed regarding mortality differences
in open repair compared to EVAR. Improved outcomes have been reported for EVAR over open repair,
including decreased length of hospitalization and lower
perioperative morbidity.80-84 However, the benefits of
EVAR are accompanied by lifelong radiologic surveillance and possible radiation exposure because of the
higher rate of complications compared to open repair.
Complications include endoleak, stent-graft migration,
kinking, and thrombosis. 43,44,46 Nonetheless, EVAR is
recommended for patients with multiple risk factors for
a poor prognosis following open repair and who have
anatomy suitable for stent-graft placement.85
The incidence rate for endograft complications ranges from 11% to 30%.86 The most common complication
of EVAR is endoleaks, which places the post-EVAR
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A Type I
B Type II
C Type III
patient at continued risk for aneurysm sac
enlargement or rupture. 43 This persistent
flow of blood into the sac post-EVAR represents a failure to exclude the aneurysm
completely.87 Estimates for the prevalence
of endoleaks ranges from 4% to 23%.88-90
Endoleaks are classified into 5 types, with
each varying in severity, prevalence, reason
for leakage, and risk of secondary rupture
(see Figure 13).91,92
Type I endoleaks result from an
incompetent seal at the proximal or distal stent-graft attachment sites. These
leaks consist of the flow of blood into the
aneurysm sac proximal or distal to the
D Type IV
E Type V
stent graft. Type I endoleaks typically
occur either immediately after insertion
or soon thereafter.91,93 Treatment of type I
endoleaks is recommended at the time of
diagnosis because the aneurysm sac can
grow and rupture from systemic pressure.
Follow-up imaging, usually CT, demonstrates blood outside the stent-graft.94
This type of endoleak can be repaired
through endovascular means; open surgical repair is a viable but secondary option
for repair.91-93 Up to 10% of endoleaks are
type I.
A type II endoleaks comprise between
10% and 45% of all endoleaks. 46,95 These
Figure 13. Illustration of endoleak classification. Reasons for aneurysm sac fillendoleaks entail retrograde blood flow
ing, expansion, or both include: A. Type I, incomplete or ineffective seal. B. Type
from aortic branch vessels (eg, lumbar,
II, retrograde branch flow of blood. C. Type III, tear in graft fabric. D. Type IV,
internal iliac, accessory renal, middle
porous graft fabric. E. Type V, no clear evidence for filling. © ASRT 2015.
sacral, and inferior mesenteric arteries).
Risk factors for type II endoleak development include the number of patent lumbar
arteries and the diameter of lumbar arteries, as larger
regarding the significance and management of type II
arteries tend to be associated with persistent endoleendoleaks. 46 The majority of researchers believe that
88,96-98
ak.
These endoleaks generally are considered
follow-up imaging for changes in aneurysm sac diamethe most benign because they do not provide arterial
ter and shape are most important because spontaneous
pressure to the aneurysm sac.99 Type II might not be
resolution has occurred in approximately one-third of
visible on the arterial phase of a CT scan, resulting in
cases. 46,95 However, evidence of increased diameter of
the need for delayed imaging. Color duplex ultrasothe aneurysm sac necessitates repair, usually endovasnography or arteriography also might be needed for
cularly. 46,99 Repair consists of the embolization of the
diagnosis. 46,94 According to Chaer, controversy exists
patent arteries involved. 89,100,101
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A type III endoleak is serious because it originates
at the junctions of the endograft components, or from
holes or tears in the endograft fabric. The resulting leak
increases the pressure in the aneurysm sac, leading to
the potential for aneurysm expansion and rupture. 46,99
Typical repair of type III leaks consist of the deployment of additional stent-grafts to seal the hole or tear, or
to bridge the disconnected endograft components. 46
Type IV endoleaks occur when blood is leaking from
either the graft wall fabric or suture holes; however, this
type of endoleak has become less common because of
improvements in graft technology and materials. Type
IV endoleaks have not been associated with long-term
adverse events and typically are self-resolving. 46
With a type V endoleak, also referred to as endotension, the aneurysm sac continues to expand without an
identified or demonstrable source of leakage or flow via
any imaging modality.102 Although poorly understood,
type V endoleaks are believed to have been improved
with a change in graft design.92,94
Migration of a stent-graft entails the movement from
its original location after EVAR, with a migration of
0.5 cm to 1 cm considered significant.44 The use of prior
images is critical for comparing the original location of
the stent-graft with the location from later images to
detect and evaluate migration. The use of consistent
anatomic landmarks from radiologic images, such as the
renal and superior mesenteric arteries, can be used to
detect migration. Factors related to stent-graft migration include device type, landing zone length, and neck
diameter and configuration. Although preoperative
planning is important, morphologic changes in the
aneurysm (eg, neck enlargement) can lead to stent-graft
migration. 44
Endograft kinking or occlusion is a complication
more commonly seen in EVAR patients than those
undergoing open repair (2.3% vs 0.2%, respectively).103
Results from a European study reveal post-EVAR
endograft kinking in 1.7% to 3.7% of cases with a significant association with type I and III endoleaks.104,105
A final complication is arterial thrombosis, estimated
to occur in approximately 3% of EVAR patients. A
key to reducing the risk of thrombosis is identifying
healthy catheter entrance vessels using a thorough
preoperative evaluation. Evaluation of the entry vessels
158
is recommended to include the degree of calcification, artery diameter, and tortuosity.106 Although the
complication rate of AAA treatment is small, the aforementioned complications might require intervention
depending on their severity.
Conclusion
Aortic abdominal aneurysm is a focal, localized
enlargement or dilatation of a section of the abdominal
aorta and is the most common type of arterial aneurysm affecting older adults. Medical imaging, including
CT, MR, ultrasonography, and angiography, plays an
important role in the detection, diagnosis, treatment,
and follow-up of AAAs. Various imaging modalities,
including ultrasonography, are used as a screening tool
to detect AAAs while they are small. Surgical and endovascular treatment options for AAA are available and
improve patients’ survival. Post-treatment, radiologic
imaging plays an important role in assessing the treatment and monitoring the patient.
Jeffrey S Legg, PhD, R.T.(R)(CT)(QM), FASRT, is
associate professor and chair of the Department of Radiation
Sciences for Virginia Commonwealth University (VCU). He
is associate editor-Americas for Radiography and chairman
of the ASRT Foundation Research Grants Advisory Panel.
Lynn M Legg, MBA, R.T.(R)(M), manages the radiology department and teaches radiographic imaging for the
VCU School of Dentistry. She has published on topics such
as mammography and dental radiography.
The authors thank Jaime Tisando, MD, FACR, FACC,
FAHA, FSIR, FSAR, professor emeritus of radiology and
surgery for VCU Medical Center, for his encouragement,
excellent review and suggestions.
Reprint requests may be mailed to the American Society
of Radiologic Technologists, Publications Department, at
15000 Central Ave SE, Albuquerque, NM 87123-3909, or
emailed to [email protected].
© 2016 American Society of Radiologic Technologists
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58. Lesperance K, Andersen C, Singh N, Starnes B, Martin MJ.
Expanding use of emergency endovascular repair for ruptured abdominal aortic aneurysms: disparities in outcomes
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59. Dillavou ED, Muluk SC, Makaroun MS. A decade of change
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have we improved outcomes equally between men and
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60. Brattheim BJ, Eikemo TA, Altreuther M, Landmark AD,
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63. Sprouse LR 2nd, Meier GH 3rd, Parent FN, et al. Is threedimensional computed tomography reconstruction justified
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65. Stavropoulos SW, Charagundla SR. Imaging techniques for
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66. Iezzi R, Santoro M, Dattesi R, et al. Multi-detector CT
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67. Kauffmann C, Tang A, Therasse E, et al. Measurements and
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68. van Prehn J, van der Wal MB, Vincken K, Bartels LW, Moll
FL, van Herwaarden JA. Intra- and interobserver variability
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504-510. doi:10.1583/08-2478.1.
69. Bargellini I, Cioni R, Petruzzi P, et al. Endovascular repair
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70. Raman SP, Johnson PT, Deshmukh S, Mahesh M, Grant
KL, Fishman EK. CT dose reduction applications: available tools on the latest generation of CT scanners. J Am Coll
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71. Gnannt R, Winklehner A, Eberli D, Knuth A, Frauenfelder T,
Alkadhi H. Automated tube potential selection for standard
chest and abdominal CT in follow-up patients with testicular
cancer: comparison with fixed tube potential. Eur Radiol.
2012;22(9):1937-1945. doi:10.1007/s00330-012-2453-y.
72. Paul JF. Individually adapted coronary 64-slice CT angiography based on precontrast attenuation values, using
different kVp and tube current settings: evaluation of image
quality. Int J Cardiovasc Imaging. 2011;27(suppl 1):53-59.
doi:10.1007/s10554-011-9960-9.
73. Apfaltrer P, Hanna EL, Schoepf UJ, et al. Radiation dose
and image quality at high-pitch CT angiography of the
aorta: intraindividual and interindividual comparisons
with conventional CT angiography. AJR Am J Roentgenol.
2012;199(6):1402-1409. doi:10.2214/AJR.12.8652.
74. Goldfarb S, McCullough PA, McDermott J, Gay SB.
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protocols for interventional radiology, diagnostic computed
tomography radiology, and interventional cardiology. Mayo
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75. Cademartiri F, Mollet NR, van der Lugt A, et al. Intravenous
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76. Kim EY, Yeh DW, Choe YH, Lee WJ, Lim HK. Image quality and attenuation values of multidetector CT coronary
angiography using high iodine-concentration contrast material: a comparison of the use of iopromide 370 and iomeprol
400. Acta Radiol. 2010;51(9):982-989. doi:10.3109/0284185
1.2010.509740.
77. Shen Y, Sun Z, Xu L, et al. High-pitch, low-voltage and lowiodine-concentration CT angiography of aorta: assessment
of image quality and radiation dose with iterative reconstruction. PLoS ONE. 2015;10(2):e0117469. doi:10.1371
/journal.pone.0117469.
78. Flors L, Leiva-Salinas C, Norton PT, Patrie JT, Hagspiel KD.
Endoleak detection after endovascular repair of thoracic
aortic aneurysm using dual-source dual-energy CT: suitable
scanning protocols and potential radiation dose reduction.
Am J Roentgenol. 2013;200(2):451-460. doi:10.2214/AJR.11
.8033.
79. Buffa V, Solazzo A, D’Auria V, et al. Dual-source dualenergy CT: dose reduction after endovascular abdominal
aortic aneurysm repair. Radiol Med. 2014;119(12):934-941.
doi:10.1007/s11547-014-0420-1.
80. Veith FJ, Lachat M, Mayer D, et al. Collected world and
single center experience with endovascular treatment of ruptured abdominal aortic aneurysms. Ann Surg. 2009;250(5):
818-824. doi:10.1097/SLA.0b013e3181bdd7f5.
81. van Beek SC, Conijn AP, Koelemay MJ, Balm R. Editor’s
choice - endovascular aneurysm repair versus open repair
for patients with a ruptured abdominal aortic aneurysm: a
systematic review and meta-analysis of short-term survival.
Eur J Vasc Endovasc Surg. 2014;47(6):593-602. doi:10.1016
/j.ejvs.2014.03.003.
82. Powell JT, Thompson SG, Thompson MM, et al. The
Immediate Management of the Patient with Rupture: Open
Versus Endovascular repair (IMPROVE) aneurysm trial-ISRCTN 48334791 IMPROVE trialists. Acta Chir Belg.
2009;109(6):678-680.
83. Desgranges P, Kobeiter H, Katsahian S, et al. Editor’s
choice - ECAR (Endovasculaire ou Chirurgie dans les
Anévrysmes aorto-iliaques Rompus): a French randomized
controlled trial of endovascular versus open surgical repair
of ruptured aorto-iliac aneurysms. Eur J Vasc Endovasc Surg.
2015;50(3):303-310. doi:10.1016/j.ejvs.2015.03.028.
84. Powell JT, Sweeting MJ, Thompson MM, et al. Endovascular
or open repair strategy for ruptured abdominal aortic aneurysm: 30 day outcomes from IMPROVE randomised trial.
BMJ. 2014;348:f7661. doi:10.1136/bmj.f7661.
85. Dillavou ED. Surgical and endovascular repair of ruptured
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consequences of persistent type II endoleaks. J Vasc Surg.
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Mehta M, Byrne J, Darling RC 3rd, et al. Endovascular
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Kim SM, Ra HD, Min SI, Jae HJ, Ha J, Min SK. Clinical
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2005;365(9478):2179-2186.
104.Fransen GA, Desgranges P, Laheij RJ, Harris PL, Becquemin
JP. Frequency, predictive factors, and consequences of stentgraft kink following endovascular AAA repair. J Endovasc
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105. Liaw JV, Clark M, Gibbs R, Jenkins M, Cheshire N, Hamady
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106.Maleux G, Koolen M, Heye S. Complications after endovascular aneurysm repair. Semin Intervent Radiol. 2009;26(1):
3-9. doi:10.1055/s-0029-1208377.
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163
Directed Reading Quiz
16806-01
1.25 Category A credits
Expires Dec. 31, 2019*
Abdominal Aortic Aneurysms
To earn continuing education credit:
 Take this Directed Reading quiz online at asrt.org/drquiz.
www.asrt.org/drquiz.
 Or, transfer your responses to the answer sheet on Page 168
410M
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*Your answer sheet for this Directed Reading must be received in the ASRT office on or before this date.
Read the preceding Directed Reading and choose the answer that is most correct based on the article.
1. An abdominal aortic aneurysm (AAA) is a focal,
localized enlargement of a section of the abdominal
aorta at least ______ cm, or when the diameter is
______ % larger than normal.
a. 7; 30
b. 3; 50
c. 4; 75
d. 6; 15
2. For a man aged 65 to 75 years who has smoked
100 or more cigarettes in his lifetime, the U.S.
Preventive Services Task Force recommends
screening:
a.once.
b. every 5 years.
c. every 10 years.
d. at various times based on other risk factors.
3. ______ is the recommended tool for AAA
screening.
a. Color duplex ultrasonography
b. Magnetic resonance angiography (MRA)
c. Computed tomography angiography (CTA)
d. Endovascular aneurysm repair (EVAR)
4. Suggested parameters of ultrasound imaging for
AAA include:
1. coronal (back to front)
2. longitudinal (along the long axis of the
aorta).
3. transverse (perpendicular to the long axis
of the aorta).
a.
b.
c.
d.
1 and 2
1 and 3
2 and 3
1, 2, and 3
continued on next page
164
RADIOLOGIC TECHNOLOGY, November/December 2016, Volume 88, Number 2
Directed Reading Quiz
5. ______ is considered the preferred method for
pre- and post-EVAR as well as postopen surgical
repair imaging surveillance.
a. Color Doppler ultrasonography
b.CTA
c.MRA
d.Radiography
9. The mortality rate from ruptured AAAs during
open repair is approximately ______ %; EVAR has
a mortality rate between 20% and 30%.
a.30
b.50
c.65
d.75
6. Anatomic considerations from preoperative imaging
include aneurysm morphology and measurements.
Examples of important aortic measurements for
sizing an endograft include all of the following
except aortic neck:
a.diameter.
b.length.
c.angulation.
d.density.
10. Dose reduction techniques during CT and CTA,
such as using ______ , are important because
patients will undergo a lifetime of surveillance after
EVAR.
1. automatic exposure control
2. dual-energy CT
3. iterative reconstruction
7. ______ is an alternative for pre-EVAR planning
in patients for whom iodinated contrast is
contraindicated.
a. Color Doppler ultrasonography
b. MRA with gadolinium
c. CT without contrast
d. Plain film radiography
a.
b.
c.
d.
1 and 2
1 and 3
2 and 3
1, 2, and 3
8. MRA has a lower sensitivity than ______ in
detecting blood vessels and renal
arteries with a diameter smaller than 2 mm.
a.CTA
b. digital subtraction angiography
c. color Doppler ultrasonography
d. CT without contrast
RADIOLOGIC TECHNOLOGY, November/December 2016, Volume 88, Number 2
165