Revision Dr Mohamed El Safwany, MD.

Liver CT Blood circulation in the liver comprises two major components: the hepatic artery and the portal vein. After intravenous contrast agent injection, rapid and repeated acquisitions of the hepatic structures allow visualization of the contrast distribution 2

Liver CT parameters:  slice thickness 3.2 mm  reconstruction interval 1.6  pitch 1.2  gantry rotation 0.5 s  field of view 350–450 mm  150–200 mAs. 3

Pulmonary angiogram  Gold Standard.  Positive angiogram provides 100% certainty that an obstruction exists in the pulmonary artery.  Negative angiogram provides > 90% certainty in the exclusion of PE.

Increment  is the distance between the reconstructed images in the Z direction.  When the chosen increment is smaller than the slice thickness, the images are created with an overlap.

Technical aspect of acute abdomen CT Imaging  IV contrast should be given at 3-5 ml/sec  total of mL,  followed by saline  Use SMART PREP or threshold tech

AORTIC ANEURYSM  Study should only be performed in hemodynamically stable patients.  Hemodynamically unstable patients with high degree of suspicion of aortic pathology should go directly to OR.  If becomes unstable in CT, a quick non conreast scan may be diagnostic.

Liver Haemangioma CT A) Pre-contrast

B) Arterial phase

C) Portal venous phase

D) Delayed phase CT – we will not do delayed phase unless haemangioma suspected. Please specify “? haemangioma” on request form.

UTILIZED

CARE BOLUS

SMART PREP

Bolus tracking- PE

PE?

Focal enhancing masses Focal enhancing masses

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Three Slices from a Volume A single acquisition is somewhat noisy A single acquisition is somewhat noisy Previous T1-weighted image was actually average of 4 separate acquisitions (to average out noise) Previous T1-weighted image was actually average of 4 separate acquisitions (to average out noise) MRI can be a 2D or a 3D acquisition technique MRI can be a 2D or a 3D acquisition technique -23-

DWI in Stroke  ADC decreases in infarcted brain tissue within minutes of the vessel blockage  Stroke damage doesn’t show up on T1- or T2- weighted images for 2-3 days post-blockage  DWI is now commonly used to assess region of damage in stroke emergencies -24-

 Good Luck