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Everything you need to know about Computed Tomography (CT) & CT Scanning

Chest: Acute Aortic Syndrome Imaging Pearls - Learning Modules | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ Chest ❯ Acute Aortic Syndrome

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  • “ Coronary artery calcification (CAC) is often not reported in pulmonary CT angiography studies. CAC is a significant predictor of acute coronary syndrome particularly in younger patients, patients without pulmonary thromboembolism, and those without cardiometabolic risk factors. Especially in these subgroups, radiologists should assess CAC findings.”
    Coronary Artery Calcification Is Often Not Reported in Pulmonary CT Angiography in Patients with Suspected Pulmonary Embolism: An Opportunity to Improve Diagnosis of Acute Coronary Syndrome
    Johnson C et al.
    AJR 2014; 202:725-729
  • “ Coronary artery calcification (CAC) was not reported in 45% of patients with positive CAC findings on imaging. Acute coronary syndrome was the final diagnosis in 31.6% of patients with unreported CAC.”
    Coronary Artery Calcification Is Often Not Reported in Pulmonary CT Angiography in Patients with Suspected Pulmonary Embolism: An Opportunity to Improve Diagnosis of Acute Coronary Syndrome
    Johnson C et al.
    AJR 2014; 202:725-729
  • “ Awareness of various nonvascular, nontraumatic mediastinal emergencies and their clinical manifestations and imaging findings is crucial for making an accurate and timely diagnosis to facilitate appropriate patient management.”
    Nonvascular, Nontraumatic Mediastinal Emergencies in Adults: A Comprehensive Review of Imaging Findings
    Katabathina VS et al
    RadioGraphics 2011; 31:1141-1160
  • Nonvascular, Nontraumatic Mediastinal Emergencies in Adults
    - Acute mediastinitis
    - Esophageal emergencies
    - Spontaneous mediastinal hematoma
    - Tension pneumomediastinum
    - Tension pneumopericardium
    - Cardiac tamponade
  • “ CT is a powerful diagnostic tool for evaluating the pericardium and its abnormalities. Knowledge of the normal recesses and sinuses is essential to avoid misdiagnosis. Functional imaging is useful in the evaluation of pricardial constriction and tamponade.”
    Computed Tomography of the Pericardium and Pericardial Disease
    Rajiah P et al.
    J Cardiovasc Comput Tomogr (2010) 4,3-18
  • Normal Pericardium: Facts
    - < 2 mm thick
    - Contains 15-50 ml of fluid
    - Pericardial recesses can be confused with adenopathy or other masses
  • Cardiac Tamponade: CT Findings
    - Large pericardial effusion
    - Enlargement of either the SVC (diameter similar or greater than adjacent aorta) or IVC  (diameter twice adjacent aorta)
    - Periportal edema
    - Reflux of contrast into IVC and  azygous vein or enlargement of hepatic and renal veins
  • “ Unenhanced CT performed well in detection of acute aortic syndrome treated surgically, although its performance does not support its use in place of contrast enhanced CTA. Unenhanced CT may be a reasonable first examination for rapid triage when IV contrast is contraindicated.”
    Acute Aortic Syndromes: A Second Look at Dual-Phase CT
    Lovy AJ et al.
    AJR 2013; 200:805-811
  • “ Contrast-enhanced CTA was highly sensitive for intramural hematoma, suggesting that unenhanced imaging may not always be needed. Acute aortic syndrome imaging protocols should be optimized to reduce radiation dose.”
    Acute Aortic Syndromes: A Second Look at Dual-Phase CT
    Lovy AJ et al.
    AJR 2013; 200:805-811
  • Acute Aortic Syndrome
    - Aortic dissection
    - Intramural hematoma
    - Penetrating atherosclerotic ulcer
    - Ruptured aortic aneurysm
  • “ Intramural blood pools (IBP) are frequently observed at multidetector CT in patients with intramural hematoma (IMH). They may resolve over time or appear during follow-up.These findings are not associated with a poor prognosis, and IBPs should be distinguished from ulcer like projections.”
    Intramural Blood Pools Accompanying Aortic Intramural Hematoma: CT Appearance and Natural Course
    Wu MT et al.
    Radiology 2011;258:705-713
  • “ Intramural blood pools (IBP) is an intramural contrast medium filled pool with a tiny intimal orifice and/or a connection with an intercostal or lumbar artery in an IMH; IBP is morphologically distinct from an ulcer like projection (ULP) which has a wiser intimal opening to the lumen.”
    Intramural Blood Pools Accompanying Aortic Intramural Hematoma: CT Appearance and Natural Course
    Wu MT et al.
    Radiology 2011;258:705-713
  • “ Most Intramural blood pools (IBP) show complete resorption over time (32 of 56 (57%) or have incomplete resorption (16 of 56 (29%) during a median follow-up of 33.8 months; the presence of IBP was not associated with poor prognosis.”
    Intramural Blood Pools Accompanying Aortic Intramural Hematoma: CT Appearance and Natural Course
    Wu MT et al.
    Radiology 2011;258:705-713
  • Retrograde Type A Dissection:
    Risk Factors
    1. Graft
    - those with proximal bare springs
    2. Aorta
    - steeply angulated aortic arch in the setting of a morphologically normal aorta
    3. Both
    - compliance mismatch between the stent graft and aortic wall
  • Operative Aortic Repair
    - Abdominal aortic graft instability
    - Aortic root repair
    - Extensive aortic pathology and staged repair
  • Post Surgical Repair
    - Comparative series of 1252 patients repaired with endoluminal stents and surgical grafts followed for up to 10 years reported rupture only after endovascular treatment.
    - Following surgical repair, the rate of anastomotic pseudoaneurysm formation (contained rupture) is 0.2-15%
  • Post Surgical Repair
    1. Surgical grafts dilate over time, rates depending on the graft material (ePTFE vs polyester).
    - At 6 years, dilatation ranges between 20-30%
    - ePTFE exhibits lowest degree of dilatation
    - Dilatation does not result in graft failure
    2. Grafts lose strength over time, owing to polyester degradation.
    - 31.4% lost at 10 years
    - 100% lost at 25-39 years
  • Aortic Root Repair
    1. Must know surgical procedure
    - valve may be replaced
    - coronary reimplantation or bypass
    2. Full root interposition
    - Excision and end-to-end anastomoses
    3. Inclusion root technique
    - Native root wrapped around graft
  • Complications
    1. Vascular
    - pseudoaneurysm
    - coronary ostial aneurysm
    - dissection
    - endoleak
    2. Periaortic   
    - mediastinitis
    - sternal dehiscence
  • Extensive Aortic Pathology
    1. Pathology that involves ascending aorta, aortic arch, descending aorta
    - +/- abdominal aorta
    2. Necessitates staged repair
    3. Stage 1:
    - Ascending aortic graft   
    - Elephant trunk prosthesis arch/proximal descending thoracic aorta
    4. Stage 2:
    - Descending aorta +/- abdominal aorta repair
  • Includes:
    • Penetrating atherosclerotic ulcer
    • Acute thoracic aortic injury
    • Intramural hematoma
    • Dissection
    • Aneurysmal leakage
  • "End diastolic diameter 95% confidence levels were 2.5-3.7 cm for the aortic root, 2.1-3.5 cm for the ascending aorta, and 1.7-2.6 cm for the descending thoracic aorta."

    Assessment of the thoracic aorta by multidetector computed tomography: Age and sex specific reference values in adults without evident cardiovascular disease
    Lin FY et al.
    J Cardiovasc Comput Tomogr (2008) 2, 298-308
  • "Aortic diameters were significantly greater at end systole than end diastole (mean difference 1.9 ± 1.2 mmfor ascending aorta and 1.3 ± 1.8 for descending thoracic aorta. P < 0.001)."

    Assessment of the thoracic aorta by multidetector computed tomography: Age and sex specific reference values in adults without evident cardiovascular disease
    Lin FY et al.
    J Cardiovasc Comput Tomogr (2008) 2, 298-308
  • Intramural Hematoma: MDCT Findings

    - High CT attenuation on non contrast CT scans
    - Focal ulcer usually present
    - More common in descending aorta but occurs in ascending aorta as well
  • Congenital Anomalies of the Thoracic Aorta

    - Sequestration
    - Vascular rings
    - Coarctation of the aorta
    - Abberrant vessels
    - Right sided arch and associated anomalies
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