076 BTAI

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 8090% 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
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub


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
Steenburg SD, et al. Radiology. 2008 Sep;248(3
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub


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, 20
Neschis DG, et al. N Engl J Med. 2008 Oct 16;359(16
Berger FH, et al. Eur J Radiol. 2010 Apr;74(1):24-39. Epub


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
echocardiograph

y (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

•Limited by accessibility, scan time

Adapted from Legome, E. Uptodate,


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)
J.E. to
Fishman,
J Thorachematoma
Imaging. 2000 Apr;2:
•Left apical cap (*) due
mediastinal

Steenburg SD, et al. Radiology. 2008 Sep;248(3


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)
Mirvis SE, Shanmuganathan K. Eur J Radiol. 2007 Oct;64(1):27-40. Epub


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


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):5


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):5


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):5


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):5


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):5


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


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


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


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


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

•Irregular pseudoaneurysm (asterisks)
•Active extravasation (blue arrows)
•Native aortic lumen is narrowed (yellow
arrows)

Presley 4

*

*

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


Atypical 1

*

•Pseudoaneurysm (blue arrows) with pseudo coarctation of the aort
•Narrowed lumen (asterisk)
•Tracheal bifurcation and NG tube displaced to the right (yellow arro