Contrast CT, or contrast-enhanced computed tomography (CECT), is

X-ray computed tomography An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

(CT) using

radiocontrast Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography (contrast CT), projectional radiography, and fluoroscopy. Radiocontrast agents are typically iod ...

. 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 administered, and ''postcontrast'' after radiocontrast administration.

Bolus tracking

Bolus tracking is a technique to optimize timing of the imaging. A small bolus of radio-opaque contrast media is injected into a patient via a peripheral intravenous

cannula A cannula (; Latin meaning 'little reed'; : cannulae or cannulas) is a tube that can be inserted into the body, often for the delivery or removal of fluid or for the gathering of samples. In simple terms, a cannula can surround the inner or out ...

. 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 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 The aorta ( ; : aortas or aortae) is the main and largest artery in the human body, originating from the Ventricle (heart), left ventricle of the heart, branching upwards immediately after, and extending down to the abdomen, where it splits at ...

pulmonary The lungs are the primary organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the backbone on either side of the heart. Their function in the respiratory syste ...

artery, cerebral,

carotid In anatomy, the left and right common carotid arteries (carotids) () are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries. Structure The common carotid a ...

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 Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide. HCC most common ...

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 disease Vascular disease is a class of diseases of the vessels of the circulatory system in the human body, body, including blood vessels – the arteries and veins, and the lymphatic vessels. Vascular disease is a subgroup of cardiovascular disease. Diso ...

s. 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

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 water-soluble, intravenous radiocontrast agent containing iodine, which enhances the visibility of vascular structures and organs during radiography, radiographic procedures. Some pathologies, such as cancer, have p ...

, such as hypersensitivity reactions, contrast-induced nephropathy, effects on thyroid function or adverse

drug interaction In pharmaceutical sciences, drug interactions occur when a drug's mechanism of action is affected by the concomitant administration of substances such as foods, beverages, or other drugs. A popular example of drug–food interaction is the effect ...

s. 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 Lean body mass (LBM), sometimes conflated with , is a component of body composition. Fat-free mass (FFM) is calculated by subtracting body fat weight from total body weight: total body weight is lean plus fat. In equations: :LBM = BW ...

of the person. In

obese Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classified as obese when ...

patients, the Boer formula is the method of choice (at least in those with

body mass index Body mass index (BMI) is a value derived from the mass (Mass versus weight, weight) and height of a person. The BMI is defined as the human body weight, body mass divided by the square (algebra), square of the human height, body height, and is ...

(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 agent A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiop ...

s may cause allergic reactions, contrast-induced nephropathy,

hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

and possibly

metformin Metformin, sold under the brand name Glucophage, among others, is the main first-line medication for the treatment of type2 diabetes, particularly in people who are overweight. It is also used in the treatment of polycystic ovary syndrome, ...

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 Exposure to ionizing radiation is known to increase the future incidence of cancer, particularly leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most wi ...

. 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