Revision Revision

Dr Mohamed El Safwany, MD.Dr Mohamed El Safwany, MD.

Liver CTLiver CT

Blood circulation in the liver comprises two Blood circulation in the liver comprises two major components: the hepatic artery and the major components: the hepatic artery and the portal vein.portal vein.

After intravenous contrast agent injection, rapidAfter intravenous contrast agent injection, rapid

and repeated acquisitions of the hepatic and repeated acquisitions of the hepatic structures allow visualization of the contrast structures allow visualization of the contrast distributiondistribution

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Liver CTLiver CT

parameters:parameters:• • slice thickness 3.2 mmslice thickness 3.2 mm• • reconstruction interval 1.6reconstruction interval 1.6• • pitch 1.2pitch 1.2• • gantry rotation 0.5 sgantry rotation 0.5 s• • field of view 350–450 mmfield of view 350–450 mm• • 150–200 mAs.150–200 mAs.

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Pulmonary angiogramPulmonary angiogram

Gold Standard.Gold Standard. Positive angiogram provides 100% Positive angiogram provides 100%

certainty that an obstruction exists in the certainty that an obstruction exists in the pulmonary artery.pulmonary artery.

Negative angiogram provides > 90% Negative angiogram provides > 90% certainty in the exclusion of PE.certainty in the exclusion of PE.

IncrementIncrement

is the distance between the reconstructed is the distance between the reconstructed images in the Z direction.images in the Z direction.

When the chosen increment is smaller When the chosen increment is smaller than the slice thickness, the images are than the slice thickness, the images are created with an overlap.created with an overlap.

Technical aspect of acute abdomen CT Technical aspect of acute abdomen CT ImagingImaging

IV contrast should be given at 3-5 ml/secIV contrast should be given at 3-5 ml/sec total of 100-120 mL,total of 100-120 mL, followed by salinefollowed by saline Use SMART PREP or threshold techUse SMART PREP or threshold tech

AORTIC ANEURYSMAORTIC ANEURYSM

Study should only be performed in Study should only be performed in hemodynamically stable patients.hemodynamically stable patients.

Hemodynamically unstable patients with Hemodynamically unstable patients with high degree of suspicion of aortic high degree of suspicion of aortic pathology should go directly to OR.pathology should go directly to OR.

If becomes unstable in CT, a quick non If becomes unstable in CT, a quick non conreast scan may be diagnostic.conreast scan may be diagnostic.

Liver Haemangioma CT Liver Haemangioma CT A) Pre-contrastA) Pre-contrast

B) Arterial phaseB) Arterial phase

C) Portal venous phaseC) Portal venous phase

D) Delayed phaseD) Delayed phase

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

UTILIZED

CARE BOLUSCARE BOLUS

                                                                                            

SMART PREPSMART PREP

                                                         

Bolus tracking- PEBolus tracking- PE

PE?PE?

Focal enhancing massesFocal enhancing masses

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Three Slices from a VolumeThree Slices from a Volume

• A single acquisition is somewhat noisyA single acquisition is somewhat noisy• Previous T1-weighted image was actually average of 4 Previous T1-weighted image was actually average of 4

separate acquisitions separate acquisitions (to average out noise)(to average out noise)

• MRI can be a 2D or a 3D acquisition techniqueMRI can be a 2D or a 3D acquisition technique--2323--

DWI in StrokeDWI in Stroke ADC decreases in infarcted brain tissue within ADC decreases in infarcted brain tissue within minutesminutes of the vessel blockage of the vessel blockage

Stroke damage doesn’t show up on T1- or T2-Stroke damage doesn’t show up on T1- or T2-weighted images for 2-3 weighted images for 2-3 daysdays post-blockage post-blockage

DWI is now commonly used to assess region of DWI is now commonly used to assess region of damage in stroke emergenciesdamage in stroke emergencies

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Good LuckGood Luck