1. Discuss aortic aneurysms ▪ Relevant anatomy, prevalence, location, aetiology and types. 2. Discuss Diagnostic Imaging ▪ Plain radiography, ultrasound and CT ▪ Discuss Ultrasound and CT with regard to imaging aortic aneuryms 3. Discuss CT with respect to aneurysms 4. Discuss patient preparation and contrast media 5. Discuss technical factors including parameters
A permanent dilation of the vessel wall, they may arise in any part of the aorta.
Illustration shows isolated aorta Major branches Not labeled: Coronary arteries Celiac and mesenteric arteries
90% of AAA are infrarenal About 70% rupture into the retroperitoneum 10-30% have free rupture
True aneurysm involves all three layers of vessel wall. Pseudoaneurysm or False aneurysm communicates with the vessel lumen, but is contained only by adventitia, or surrounding tissue Normal True Pseudo- Dissecting Aorta Aneurysm Aneurysm Aneurysm
Family Hx, ?Genetic 1st degree relative 10-20 times the risk More common in men than women Atherosclerotic risk factors ie Diabetes Hypertension High cholesterol Smoking Age >65 Family History Other predisposing factors include Infection, trauma, connective tissue disease and arteritis.
(AAA) is a true aneuryms involve the infrarenal aorta. Diameter >3cm = AAA AAA of any size can rupture, but those >5cm more likely to rupture Size is most important factor in determining rupture risk Rupture is associated with 80-90% overall mortality
Usually not diagnostic Sometimes calcification of wall visible “Eggshell calcification” (Curvilinear calcification in the wall of the Aorta) Rarely seen Even if AAA visualised, you cannot tell Size of aneurysm If it is leaking
Non-ionic contrast-enhanced CT provides information about • Size of the aneurysmal lumen, • Presence of active extravasation, and the relationship of an aneurysm to the abdominal vasculature. 3D multiplanar reformatting - evaluates the relationship of the aneurysm with other structures planning endovascular stent-graft placement
Consent /ID ▪ Explanation of the procedure ensuring informed consent is gained. ▪ Verify pt. details. Bowel preparation ▪ May require bowel prep if time permits. ▪ Follow-up /mapping for stent design, patients may require complete bowel preparation Pt. History Patient history such as pregnancy status checked if applicable, Active kidney disease, kidney failure, dialysis, thyroid cancer, hyperthyroidism, asthma medication and Metformin checked Potential Artefact removal
Scanner calibrations and tube warm-up procedures should be done while the room is free of both patients and CT staff Equipment appropriate equipment ▪ head holder foot extension, thyroid or breast shields
patient supine head first arms place above the head* 60mlTequila administered by Oprah
Contrast media (CM) - Omnipaque-350 or Omnipaque-240 is used depending on hospital protocol Bolus administered beginning of scan. This ensures accurate visualisation of aneurysm. Reactions to CM are classified into three categories: Mild, Moderate, and Severe
Scan Parameters –AAA Scanogram ▪ Top of the kidneys to the aortic bifurcation (level of L5). Chest/abdo ▪ Slice Thickness ▪ Average slice thickness=10mm. ▪ A 5mm scan may be preferred at the level of the renal arteries, to ascertain the relationship to the aortic aneurysm.
aneurysm outlined in blue haematoma outlined in red
Benefits Limitations Non-invasive Ionising radiation Highly predictive of aneurysm size Higher $CT Localises proximal extent of aneurysm Limited info arterial anatomy Gold standard for querying rupture Availability Contrast media enhances structure Contrast reactions Cheaper $ Suboptimal in obese patients Widely available / portable/ Quick Suboptimal with increased bowel gas Non-invasive Subjective interpretationUS No Radiation Cannot determine patency of visceral vessels Can see free fluid if ruptured into peritoneal cavity Cannot identify peri-aortic disease
http://radiopaedia.org/ http://radiographics.rsna.org/ http://ct.com/ http://aorticaneurysm/ucol.ac.nz http://georgebushisawanker.com/ Gedroyc, W., & Rankin, S. (1992). Practical CT techniques. London: Springer-Verlag. Golledge, J., Muller, J., Daugherty, A., & Norman, P. (2006). Abdominal aortic aneurysm pathogenesis and implications for management. Arteriosclerosis, Thrombosis, and Vascular Biology: Journal of the American Heart Association, 26, 2605-2613.