CT with IV contrast
Bolus tracking is where a specified location within the circulatory system is monitored during IV contrast infusion, and the timing of the main imaging is counted from when the contrast reaches this location (sufficiently to achieve a specified threshold).
Washout is where tissue loads radiocontrast during arterial phase, but then returns to a rather hypodense state in venous or later phases. This is a property of for example hepatocellular carcinoma as compared to the rest of the liver parenchyma.
Low renal function
- Main article: CT with IV contrast in low renal function
Decreased renal function and several other conditions increase the risk of contrast-induced nephropathy, which is a potentially lethal renal injury to the kidney following intravenous radiocontrast.
When it matters
According to European guidelines, the main risk factors of contrast-induced nephropathy:
- Estimated glomerular filtration rate (eGFR) of less than 30 ml/min/1.73 m2 before intra-venous or intra-arterial radiocontrast administration with second-pass renal exposure (passing lungs or other tissues before the kidneys).
- eGFR of less than 45 ml/min/1.73 m2 before intra-arterial administration with first-pass renal exposure or in ICU patients
- Known or suspected acute renal failure
- Large doses of radiocontrast given IA with first-pass renal exposure
- Multiple radiocontrast injections within 48-72 h
Further reading: CT with IV contrast in low renal function
- Main article: Contrast medium reaction
In a more severe reaction:
- Adrenaline shot, 0.3-0.5mg in adults, given intramuscularly.
- Summon an anesthesiologist
- Main article: Prevention of contrast medium reaction
Before a contrast CT of a patient with known allergic-like or unknown-type of contrast reaction to the same class of contrast medium (such as iodinated), the American College of of Radiology recommends premedication with a glucocorticoid, preferably starting 12 or 13 hours before contrast administration.
Depending on the purpose of the investigation, there are standardized protocols for time intervals between intravenous radiocontrast administration and image acquisition, in order to visualize the dynamics of contrast enhancements in different organs and tissues. The main phases thereof are as follows in table below.
CT angiography is a CT scan corresponding with contrast filling one or more blood vessels of interest.
|Phase||Time from injection||Time from bolus tracking in proximal aorta||Targeted structures and findings|
|Non-enhanced CT (NECT)||-||-|
|Pulmonary arterial phase||6-13 sec||-|
|Pulmonary venous phase||17-24 sec||-|
|Early systemic arterial phase||15-20 sec||immediately||
| Late systemicarterial phase
Sometimes also called "arterial phase" or "early venous portal phase"
|35-40 sec||15-20 sec||
|Pancreatic phase||30 or 40 - 50 sec||20-30 sec|
|Hepatic (most accurate) or late portal phase||70-80 sec||50-60 sec||
|Nephrogenic phase||100 sec||80 sec||
|Systemic venous phase||180 sec||160 sec|
| Delayed phase
Sometimes called "wash out phase" or "equilibrium phase"
|6-15 minutes||6-15 minutes||
See CT#By location (CT with IV contrast, including CT angiography, is organized as other CT examinations).
- For a full list of contributors, see article Radlines:Authorship for details. . Creators of images are attributed at the image description pages, seen by clicking on the images. See
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