Contrast CT, or contrast enhanced computed tomography (CECT), is X-ray computed tomography (CT) using radiocontrast. Radiocontrasts for X-ray CT are generally iodine-based types. This is useful to highlight structures such as blood vessels that otherwise would be difficult to delineate from their surroundings. Using contrast material can also help to obtain functional information about tissues. Often, images are taken both with and without radiocontrast. CT images are called ''precontrast'' or ''native-phase'' images before any radiocontrast has been administrated, and ''postcontrast'' after radiocontrast administration.

Bolus tracking

Bolus tracking is a technique to optimize timing of the imaging. A small

bolus Bolus may refer to: Geography * Bolus, Iran, a village in Ardabil Province, Iran * Bolus, or Baulus, an Anatolian village on the site of ancient Berissa Medicine * Bolus (digestion), a ball-shaped mass moving through the digestive tract * Bolus ...

of radio-opaque contrast media is injected into a patient via a peripheral intravenous cannula. Depending on the vessel being imaged, the volume of contrast is tracked using a region of interest (abbreviated "R.O.I.") at a certain level and then followed by the

CT scanner A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...

once it reaches this level. Images are acquired at a rate as fast as the contrast moving through the blood vessels. This method of imaging is used primarily to produce images of arteries, such as the aorta, pulmonary artery,

cerebral Cerebral may refer to: * Of or relating to the brain * Cerebrum, the largest and uppermost part of the brain * Cerebral cortex, the outer layer of the cerebrum * Retroflex consonant, also referred to as a cerebral consonant, a type of consonant so ...

, carotid and hepatic arteries.

Washout

"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.

Phases

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:

Angiography

CT angiography is a contrast CT taken at the location and corresponding phase of the blood vessels of interest, in order to detect vascular diseases. For example, an ''abdominal aortic angiography'' is taken in the arterial phase in the abdominal level, and is useful to detect for example aortic dissection.

Amount

CT scan of hepatocellular carcinoma, without and with IV contrast

Adults

The following table shows the preferable volume in normal weight adults. However, dosages may need to be adjusted or even withheld in patients with risks of

iodinated contrast Iodinated contrast is a form of intravenous radiocontrast agent containing iodine, which enhances the visibility of vascular structures and organs during radiographic procedures. Some pathologies, such as cancer, have particularly improved visib ...

, such as hypersensitivity reactions, contrast-induced nephropathy, effects on thyroid function or adverse drug interactions. The dose should be adjusted in those not having normal body weight, and in such cases the adjustment should be proportional to the lean body mass of the person. In obese patients, the Boer formula is the method of choice (at least in those with body mass index (BMI) between 35 and 40): For men: Lean body mass = (0.407 × W) + (0.267 × H) − 19.2 For women: Lean body mass = (0.252 × W) + (0.473 × H) − 48.3

Children

Standard doses in children:

Adverse effects

Iodinated contrast agents may cause allergic reactions, contrast-induced nephropathy,

hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

and possibly metformin accumulation. However, there are no absolute contraindications to iodinated contrast, so the benefits needs to be weighted against the risks. Page last modified on 26/7/2017 As with CT scans in general, the radiation dose can potentially increase the risk of radiation-induced cancer. The injection of iodinated contrast agents may sometimes lead to its extravasation

Notes

References

External links

*{{cite web, url=https://radlines.org/CT_with_IV_contrast_in_low_renal_function, title=CT with IV contrast in low renal function, website=Radlines.org X-ray computed tomography