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 > 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 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 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 Atypical  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  Aortic spindle BTAI  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 Berger FH, et al Eur J Radiol 2010 Apr;74(1):24-39 Epub Aortic spindle with ductus remnant Contrast-enhanced chest CT •Mild contour irregularity in medial aspect of proximal descending thoracic aorta •Ductus remnant arising anteriorly Volume-rendered image of thoracic aorta Mild narrowing of the isthmic portion of the aorta with slight post-isthmic Mirvis SE, et al Eur Jjust Radiol 2007 to Oct;64(1):27-40 Epub dilatation distal site of ductus 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 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 Forbes J, et al Eur J Radiol 2010 In 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 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 Steenburg SD, et al Radiology 2008 Sep;248(3 MRI follow-up of Stent graft repair CT follow-up after stent graft repair MRI follow-up year after stent graft re Imaging follow-up postrepair 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 mAs(Tube A)post-processing reconstruction times kV 120 210 Kernel B Kernel B B36 (Mediastinum) Axial 2mmx1mm B70(Lung) Axial 1mmx1mm Kernel B Collimation B36 (Mediastinum) 128 mmx 0.6mm Coronal 3mmx1mm Pitch Rot Time CTDI vol 3.2 0.28s 9.08mGy   •Bolus injection of 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 Screening for BTAI Nzewi O, et al Eur J Vasc Endovasc Surg 2006 Jan;31(1):18-27 Epu 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) Fabian TC, et al Ann Surg 1998 May;227(5) Steenburg SD, et al Radiology 2008 Sep;248(3 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           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 Steenburg SD, Ravenel JG, Ikonomidis JS, Schönholz C, Reeves S Acute traumatic aortic injury: imaging evaluation and management Radiology 2008 Sep;248(3):74862 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):97-103 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 ... 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... 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... the aorta Forbes J, et al Eur J Radiol 2010 In BTAI: Role of MRI  Magnetic resonance (MR) angiography has excellent characteristics for detecting BTAI  May be a strategy for radiation dose reduction