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What are we trying to acheive?
What are we trying to acheive?
A scan of the chest timed with peak contrast enhancement of vessels of interest eg aortic arch, pulmonary arteries. We often scan patients with very complicated congenital abnormalities, which means there major chest and heart vessels will not be correctly positioned/absent. Therefore a CTA chest is a very important part of their diagnosis.
On Siemens scanners, we can achieve peak contrast enhancement of vessels through two methods. Bolus tracking or Test Bolus. See video below for a quick explanation of the methods
bolus tracking/
bolus tracking/
monitoring
monitoring
1 contrast injection
Unknown scan delay
Triggers start of scan off ROI placed in vessel. Once the vessel reaches high enhancement the scan is triggered to start.
Advantages:
Does not contaminate ROI with contrast prior to actual scan
Disadvantages:
Makes it more difficult to have breath hold inbuilt to scanner
Unknown scan delay so can potentially trigger prior to contrast finishing. This results in excess contrast given and contrast pooling in the SVC and creating a streaking artefact across the chest.
test bolus
test bolus
2 contrast injections
1 for test bolus
1 for scan
Set delay of scan based of time to peak enhancement given on test bolus images.
Advantages:
Test injection allows us to observe the patient reaction with contrast prior to actual scan
Can add in breath hold on scanner
Potential for reduced contrast due to us knowing the scan delay eg 12s scan delay means we don't need more than 12s of contrast
Disadvantages: Contaminates contrast in vessels/organs prior to actual scan. Therefore may not ideal for brains/carortid/abdomen angiograms
Try observe and scan some angiograms this week using both bolus tracking and test bolus
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