MDCT & MRI PICTORIAL REVIEW
OF BLUNT TRAUMATIC AORTIC
INJURY
David Tso, Ferco Berger, Anja Reimann, Chris Davison, Joao Inacio,
Ahmed Albuali, Savvas Nicolaou
Objectives
 Review the pathophysiology of blunt traumatic
aortic injury (BTAI)
 Describe the Presley Trauma Center CT grading
system for aortic injury
 Present current MDCT protocols for the
assessment of blunt traumatic aortic injury
 Describe typical primary and secondary findings
on MDCT in blunt traumatic aortic injury
 Introduce a low dose ultra high pitch MDCT
protocol
Introduction
 Blunt traumatic aortic injury (BTAI) has a high
mortality rate, immediately lethal in 80-90% of
cases
 50% of patients that survive the immediate
injury die within 24 hours if not promptly treated
 Majority of BTAI occur following motor vehicle
collisions secondary to high-speed deceleration
 Prompt recognition and treatment of BTAI is
crucial for long-term survival
 Clinical signs absent in up to 1/3 of patients
  suspect BTAI in any severe deceleration or high-speed
impact
Steenburg SD, et al. Radiology. 2008 Sep;248(3):748-62.
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub 2009 Aug 8.
Mechanisms of Injury
 75%–80% of thoracic aortic injuries result from
high-speed motor vehicle collisions (MVC)
involving rapid deceleration due to head-on or
side-impact collisions > 50 km/h
 Descending aorta is fixed to chest wall, while
heart and great vessels are relatively mobile
 Sudden deceleration causes a tear at junction
between fixed and mobile portions of the aorta,
usually near the isthmus
 Injury may also occur to ascending aorta, distal
descending thoracic aorta, or abdominal aorta
Neschis DG, et al. N Engl J Med. 2008 Oct 16;359(16):1708-16.
Steenburg SD, et al. Radiology. 2008 Sep;248(3):748-62.
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub 2009 Aug 8.
Mechanisms of Injury
 Shearing forces may cause tears
at the aortic isthmus (site of
attachment for ligamentum
arteriosum) due to inflexibility of
the aorta at this site
 Direct compression of sternum
(osseous pinch) can compress
aortic root and cause retrograde
high pressure on the aortic valve
 Water-hammer effect

Simultaneous occlusion of aorta
and sudden elevation of blood
pressure
Legome, E. Uptodate, 2010.
Neschis DG, et al. N Engl J Med. 2008 Oct 16;359(16):1708-16.
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub 2009 Aug 8.
Imaging Options
Imaging Modality
Comments
Plain radiograph
•Upright preferable; sensitivity of supine unclear
•Normal PA radiograph has high negative predictive value; good test for low to
moderate suspicion
•If high clinical suspicion, or abnormal radiograph, further testing required
Chest CT Scan
•Test of choice
•Highly sensitive and specific
•Requires IV contrast
•Can usually proceed directly to OR with positive CT
•Equivocal study necessitates angiography
Angiography
•Highly sensitive and specific
•No longer plays a role, not even when CT results are equivocal
•Rarely adds values in setting of diagnostic CT and delays intervention
Transesophageal
echocardiography
(TEE)
•Highly accurate
•Can be performed at beside or OR, or those who cannot tolerate contrast
•Limited to proximal ruptures, operator dependent
•Largely replaced by MDCT
Magnetic
Resonance (MR)
•Limited by accessibility, scan time
•Potential role in follow-up after post-op aortic repair or equivocal findings
•Strategy for radiation dose reduction in young trauma victims
Adapted from Legome, E. Uptodate, 2010
Imaging findings on CXR
 Mediastinal widening > 8
cm


High Sensitivity (> 80%)
Low specificity (< 50%)
 Obscured aortic knob
 Abnormal paraspinous




stripes
Blood in apex of lung
(apical cap sign)
NG tube, trachea, or
endotracheal tube
deviation to right
CXR usually first imaging
done in trauma setting
CXR can be normal or
only minimally abnormal
•Widening of mediastinum with deviation of trachea (T) to the right
•Depression of left main-stem bronchus (LM)
•Convexity of aortopulmonary window (arrow)
•Left apical cap (*) due to mediastinal hematoma
J.E. Fishman, J Thorac Imaging. 2000 Apr;2:97-103.
Steenburg SD, et al. Radiology. 2008 Sep;248(3):748-62.
Advances in Imaging
 Multi-detector CT (MDCT) has become the
imaging modality of choice due to its speed,
sensitivity and availability
 Improved spatial resolution, better overall image
quality, and supplemental post-processing
techniques have contributed to success of CT
 Sensitivity of MDCT for BTAI > 98%
 MDCT has almost completely eliminated the use
of aortography and transesophageal
echocardiography
Demetriades D, et al. J Trauma. 2008 Jun;64(6):1415-8.
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
VGH MDCT Protocol
Protocol
Aortic
Dissection
(scan time
7 sec)
mAs(Tube
A) kV 120
240
Kernel B
Kernel B
Kernel B
Kernel B
B43
B43
B43
B60(Lung) (Mediastinum)
(Mediastinum)
(Mediastinum)
Axial
Oblique Arch
Axial
Coronal
5mmx2.5mm
3mmx1mm
1mmx0.9mm
3mmx1.5mm
MIP
Collimation
Pitch
Rot Time
CTDI vol
128 mmx
0.6mm
0.6
0.33sec
16.22mGy
 Scan is triggered at aortic arch followed by an 8 sec delay
after a trigger HU of 100 is reached
 Saline chaser to tighten bolus and eliminate streak
artefacts
 Single contrast-enhanced phase sufficient for aortic trauma
cases
 ECG-gating may reduce pulsation artefacts
 Additional radiation exposure
 Used for equivocal cases
 Breath-hold technique to minimize breathing artefacts
 Scanner with improved temporal resolution may reduce this
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub 2009 Aug 8.
Presley Classification
 Proposed CT grading system used to
estimate the severity of aortic injuries
 Severity based on findings of




Mediastinal hematoma
Pseudoaneurysm
Intimal flaps or thrombus
Peri-aortic hematoma
 Can be used as an early guide for
management and may help predict clinical
outcomes
Gavant ML. Radiol Clin North Am. 1999 May;37(3):553-74, vi.
Presley Classification: Grade 1
Grade 1a:
- Normal aorta
- NO mediastinal hematoma
Grade 1b:
- Normal aorta
- mediastinal hematoma, aorta
surrounded by fatplane
Gavant ML. Radiol Clin North Am. 1999 May;37(3):553-74, vi.
Presley Classification: Grade 2
Grade 2a:
- Psuedoaneurysm, intimal flap or
thrombus < 1cm
- NO mediastinal hematoma
Grade 2b:
- Psuedoaneurysm, intimal flap or
thrombus < 1cm
- Peri-aortic hematoma
Gavant ML. Radiol Clin North Am. 1999 May;37(3):553-74, vi.
Presley Classification: Grade 3
Grade 3a:
- regular pseudoaneurysm > 1 cm with
intimal flap or thrombus
- peri-aortic hematoma
- NO involvement ascending aorta, arch
or branching vessels
Grade 3b:
- regular pseudoaneurysm > 1 cm with
intimal flap or thrombus
- peri-aortic hematoma
- involvement of ascending aorta, arch or
branching vessels
Gavant ML. Radiol Clin North Am. 1999 May;37(3):553-74, vi.
Presley Classification: Grade 4
Grade 4:
- Irregular, poorly defined
Pseudoaneurysm with intimal flap or thrombus
- large peri-aortic hematoma
Gavant ML. Radiol Clin North Am. 1999 May;37(3):553-74, vi.
Intimal luminal flap & thrombus
 Flaps of torn intima often project into the
aortic lumen
 Thrombus may form in association with
intimal flaps along aorta walls where intima
has been torn
 Important to recognize thombi as potential
source of emboli
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Presley 2A
•Minimal aortic injury, intimal flap / thrombus < 1 cm (blue arrow)
•No signs of peri-aortic hematoma
•Collapsed lung on this window and level setting mimics hematoma (yellow arrow)
Presley 2B
A
B
•Minimal aortic injury, intimal flap / thrombus < 1 cm (A, blue arrow)
•Peri-aortic hematoma (B, blue arrow)
Aortic pseudoaneurysm
 Most aortic injuries demonstrate clearly defined
aortic pseudoaneurysm on CT
 Appears as a rounded bulge from the lumen with
irregular margins
 Arise from anterior aspect of the proximal
descending aorta at the level of the left
mainstem bronchus and proximal left pulmonary
artery
 Injury may include entire circumference of the
aorta and may involve the aortic wall several
centimetres proximal and distal to the
pseudoaneurysm
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Presley 3A
*
A
B
C
•Regular pseudoaneurysm> 1 cm (A, blue arrows, Aorta lumen asterisk)
•Peri-aortic hematoma (B, blue arrows) seen in a sagittal reformat in C
•(blue arrow = pseudoaneurysm)
Periaortic mediastinal hemorrhage
 Mediastinal hemorrhage does not arise directly
from an aorta tear
 Usually stable as long as there is not a complete
breach of the wall of a major artery
 Majority of aorta injuries are associated with
mediastinal hemorrhage
 BTAI can occur in absence of periaortic
hematoma
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Presley 3B
*
*
•Pseudoaneurysm of the distal aortic arch (yellow arrow)
•Peri-aortic extensive mediastinal hematoma (blue arrows)
•Asterisks indicate aortic lumen of the arch
Contrast extravasation
 Findings on CT
 Extensive mediastinal hematoma
 Bulging of the mediastinal pleura
 Marked displacement of esophagus and trachea
 Patients with finding of contrast
extravasation are in imminent danger of
exsanguination
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Presley 4
•Irregular pseudoaneurysm (asterisks)
•Active extravasation (blue arrows)
•Native aortic lumen is narrowed (yellow arrows)
*
*
A
*
B
*
C
D
Secondary findings
 Pseudoaneurysm, intimal dissection, or
intraluminal clot can diminish blood flow into
the descending aorta  can mimic a
coarctation
 Aortic lumen below injury site is atypically
smaller in caliber
 May observe displacement of NG tube,
trachea, or esophagus due to mass effects
caused by periaortic mediastinal hematoma
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Atypical 1
*
•Pseudoaneurysm (blue arrows) with pseudo coarctation of the aorta
•Narrowed lumen (asterisk)
•Tracheal bifurcation and NG tube displaced to the right (yellow arrow)
Atypical 2
• Frank transection of the
aortic arch in an elderly
lady with extensive
atherosclerotic plaques
• Extravasation without
pseudoaneurysm
formation (blue arrow)
• Extensive peri-aortic and
mediastinal hematoma
(yellow arrows)
• Left hemothorax (red
arrow)
Atypical 3
 2 levels of aortic injury:
 Distal descending aorta
(blue arrow)
 Proximal abdominal aorta
(red arrow)
 Vertebral body fracture
at level of abdominal
aorta injury (yellow
arrow)
Anatomic variants mimicking BTAI
 Aortic spindle
 Fusiform dilation of aorta immediately beyond isthmus
 Change in aortic caliber and slight indentation at transition can
be mistaken for injury
 Ductus diverticulum
 Developmental outpouching of aorta usually seen at the
anteromedial aorta at site of aortic isthmus
 Usually appears as a smooth focal bulge with gentle obtuse
angles with the aortic wall
 Ductus remnant
 Fibrous remnant of ductus arteriosus
 Often displays linear calcification
 Branch vessel infundibula
 May simulate traumatic injuries or pseudoaneurysms
 Recognized by anatomic configuration and smooth conical
margins and presence of a vessel emanating from apex of the
infundibulum
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub 2009 Aug 8.
Aortic spindle with ductus remnant
Contrast-enhanced chest CT
•Mild contour irregularity in medial aspect
of proximal descending thoracic aorta
•Ductus remnant arising anteriorly
•No mediastinal hemorrhage
Volume-rendered image of thoracic aorta
Mild narrowing of the isthmic portion of the
aorta with slight post-isthmic dilatation just
distal to site of ductus remnant
Mirvis SE, et al. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Ductus diverticulum
Contrast-enhanced chest CT
•Smoothly contoured “bump” arising
from anterior proximal descending aorta
at level of the carina
•Consistent with a ductus bump
•No mediastinal hemorrhage.
Volume-rendered view
Outer contour of the ductus and its
close proximity to the left
pulmonary artery
Mirvis SE, et al. Eur J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
50 yo male MVC, unbelted driver
Out pouching from inferior margin of aortic arch concavity posteriorly 1 cm in length
Significant mediastinal hematoma within anterior superior mediastinum
Forbes J, et al. Eur J Radiol. 2010 In Press
Ductus diverticulum of aorta
•No significant change in appearance of aorta or small out pouching
•No progression of mediastinal hematoma seen
•Stable nature of this lesion consistent with a ductus diverticulum of the aorta
Forbes J, et al. Eur J Radiol. 2010 In Press
BTAI: Role of MRI
 Magnetic resonance (MR) angiography has
excellent characteristics for detecting BTAI
 May be a strategy for radiation dose reduction in
young trauma victims
 MR in trauma patient limited due to logistical
issues
 Although not optimal in acute settings, MRI can
be a useful in complex cases
 Can demonstrate subintimal hemorrhage that can be
a clue to traumatic thoracic aortic dissection
 Flash thoracic CT – Low dose
 Follow up for post stent
Forbes J, et al. Eur J Radiol. 2010 In Press
Steenburg SD, et al. Radiology. 2008 Sep;248(3):748-62.
MRI follow-up of Stent graft
repair
CT follow-up after stent graft repair
MRI follow-up 1 year after stent graft repair
Imaging follow-up post-repair
Focal aneurysm seen is a focal expansion of the stent
High pitch MDCT protocol
 Motion artefacts may be misinterpreted as BTAI
 Using dual source CT  can achieve high temporal




Protocol
FLASH Aortic
Dissection
(scan time
0.6 sec)
resolution
Maximum pitch = 3.2
Advantage = ability to capture images of the aorta and
other vascular structures with little motion artefact
Can be non-ECG-triggered for ultrafast spiral scanning
Faster post-processing reconstruction times
mAs(Tube A)
kV 120
Kernel B
Kernel B
210
B36
(Mediastinum)
Axial 2mmx1mm
B70(Lung)
Axial
1mmx1mm
Kernel B
Collimation
B36
(Mediastinum)
128 mmx 0.6mm
Coronal
3mmx1mm
•Bolus injection of 5 cc/sec of optiray 320 for 80cc, followed by 40 cc of saline
•Premonitoring is at the Pulmonary artery.
•Scan is triggered at 100 HU. FLASH protocol uses 10 sec delay after HU threshold is reached
Pitch
Rot Time
CTDI vol
3.2
0.28s
9.08mGy
Screening for BTAI
CXR
Abnormal
mediastinum
Normal
mediastinum
CT with
contrast
Normal CT
No further
action
BTAI
Treatment
Suspicious
Hx
No further
action
Equivocal
finding
Gated Study
or MRI
Nzewi O, et al. Eur J Vasc Endovasc Surg. 2006 Jan;31(1):18-27. Epub 2005 Oct 14.
Treatment for BTAI
 Open surgical repair previously the mainstay of therapy
 Endovascular stenting becoming more common since it is
less invasive and has less complications
 Aggressive blood pressure control necessary if any delay in
surgical treatment
 HR < 100 bpm
 SBP < 100 mmHg
 Do not delay surgery if imaging or clinical findings reveal
evidence of active or impending rupture




Contrast extravasation
Pseudocoarctation
Rapid enlargement of a pseudoaneurysm
Large, reaccumulating hemothorax
Demetriades D, et al. J Trauma. 2008 Jun;64(6):1415-8.
Fabian TC, et al. Ann Surg. 1998 May;227(5):666-76.
Steenburg SD, et al. Radiology. 2008 Sep;248(3):748-62.
Future Directions
 Need for a more appropriate classification system taking into
account a wider spectrum of aortic injuries
 Use of ECG-gated MDCT vs. high pitch vs. volume imaging
 ECG-gating may reduce pulsation artefacts, but at the cost of
additional radiation exposure
 High pitch allow faster scanning times, reducing motion artefacts
 Increase in number of detectors enabling greater coverage with a
single rotation
 Dual energy imaging
 Utility of virtual non-contrast and bone subtraction in visualizing
aorta and related vascular structures
 Ability to visualize intramural hematoma
Conclusion
 Traumatic aortic injury is time-sensitive injury
requiring rapid and accurate diagnosis
 Contrast enhanced MDCT is imaging
modality of choice when investigating aortic
injuries with sensitivity similar to angiography
 Normal variations in aortic anatomy may
mimic aortic injury and must be assessed in
context of the clinical picture
 MRI is less established in the emergency
setting, but may have a role in distinguishing
overlapping aortic pathologies
References
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Berger FH, van Lienden KP, Smithuis R, Nicolaou S, van Delden OM. Acute aortic syndrome and
blunt traumatic aortic injury: pictorial review of MDCT imaging. Eur J Radiol. 2010 Apr;74(1):24-39.
Epub 2009 Aug 8.
Steenburg SD, Ravenel JG, Ikonomidis JS, Schönholz C, Reeves S. Acute traumatic aortic injury:
imaging evaluation and management. Radiology. 2008 Sep;248(3):748-62.
Gavant ML. Helical CT grading of traumatic aortic injuries. Impact on clinical guidelines for
medical and surgical management. Radiol Clin North Am. 1999 May;37(3):553-74, vi.
Mirvis SE, Shanmuganathan K. Diagnosis of blunt traumatic aortic injury 2007: still a nemesis. Eur
J Radiol. 2007 Oct;64(1):27-40. Epub 2007 Mar 21.
Neschis DG, Scalea TM, Flinn WR, Griffith BP. Blunt aortic injury. N Engl J Med. 2008 Oct
16;359(16):1708-16.
Nzewi O, Slight RD, Zamvar V. Management of blunt thoracic aortic injury. Eur J Vasc Endovasc
Surg. 2006 Jan;31(1):18-27. Epub 2005 Oct 14.
Fishman JE. Imaging of blunt aortic and great vessel trauma. J Thorac Imaging. 2000 Apr;15(2):97103.
Forbes J, Yong-Hing CJ, Galea-Soler S, Nicolaou S. Ductus diverticulum: A confusing normal
variant in the setting of trauma. Eur J Radiol. 2010 In Press
Fabian TC, Davis KA, Gavant ML, Croce MA, Melton SM, Patton JH Jr, Haan CK, Weiman DS, Pate
JW. Prospective study of blunt aortic injury: helical CT is diagnostic and antihypertensive therapy
reduces rupture. Ann Surg. 1998 May;227(5):666-76.
Demetriades D, Velmahos GC, Scalea TM, Jurkovich GJ, Karmy-Jones R, Teixeira PG, Hemmila MR,
O'Connor JV, McKenney MO, Moore FO, London J, Singh MJ, Spaniolas K, Keel M, Sugrue M, Wahl
WL, Hill J, Wall MJ, Moore EE, Lineen E, Margulies D, Malka V, Chan LS. Diagnosis and treatment
of blunt thoracic aortic injuries: changing perspectives. J Trauma. 2008 Jun;64(6):1415-8.