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

X-ray computed tomography An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 ...

(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 io ...

. 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 of radio-opaque contrast media is injected into a patient via a peripheral intravenous

cannula A cannula (; Latin meaning 'little reed'; plural or ) 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 outer surfaces ...

. Depending on the vessel being imaged, the volume of contrast is tracked using a

region of interest A region of interest (often abbreviated ROI) is a sample within a data set identified for a particular purpose. The concept of a ROI is commonly used in many application areas. For example, in medical imaging, the boundaries of a tumor may be def ...

(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 ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...

pulmonary The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

artery, cerebral,

carotid In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
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. It occurs in t ...

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 Computed tomography angiography (also called CT angiography or CTA) is a computed tomography technique used for angiography—the visualization of arteries and veins—throughout the human body. Using contrast injected into the blood vessels, i ...

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 blood vessels – the arteries and veins of the circulatory system of the body. Vascular disease is a subgroup of cardiovascular disease. Disorders in this vast network of blood vessels can cause a ra ...

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 Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or ...

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 visibil ...

, such as hypersensitivity reactions,

contrast-induced nephropathy Contrast-induced nephropathy (CIN) is a purported form of kidney damage in which there has been recent exposure to medical imaging contrast material without another clear cause for the acute kidney injury. Despite extensive speculation, the actua ...

, effects on thyroid function or adverse

drug interaction Drug interactions occur when a drug's mechanism of action is disturbed by the concomitant administration of substances such as foods, beverages, or other drugs. The cause is often the inhibition of the specific receptors available to the drug, ...

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 ''fat-free mass'', 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&n ...

of the person. In

obese Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...

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 (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m2, resulting from mass in kilograms and he ...

(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,

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 hyperthyroidism ...

and possibly

metformin Metformin, sold under the brand name Glucophage, among others, is the main first-line medication for the treatment of type 2 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