From Surf Wiki (app.surf) — the open knowledge base

Contrast CT

Medical imaging technique

Summary

Medical imaging technique

pulmonary arteries]], because of suspected [[pulmonary embolism]]. A contrast delivery system is connected to a [[peripheral venous catheter]] in her left arm.

radiolucent]] than the [[radiocontrast]] filled blood surrounding it (but it may be indistinguishable without radiocontrast)

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 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. 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, pulmonary artery, cerebral, 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:

Phase	Time from injection	Time from bolus tracking	Targeted structures and findings	Non-enhanced CT (NECT)	Pulmonary arterial phase	Pulmonary venous phase	Early systemic arterial phase	Late systemicarterial phase
Sometimes also called "arterial phase" or "early venous portal phase"	Pancreatic phase	Hepatic (most accurate) or late portal phase	Nephrogenic phase	Systemic venous phase	Delayed phase
Sometimes called "wash out phase" or "equilibrium phase"
title=5th European Conference of the International Federation for Medical and Biological Engineering 14 - 18 September 2011, Budapest, Hungary. Volume 37 of IFMBE Proceedings	author=Ákos Jobbágy	publisher=Springer Science & Business Media	year=2012	isbn=978-3-642-23508-5}}	-
17–24 sec	-
15–20 sec	immediately
35–40 sec	15–20 sec
vauthors=Raman SP, Fishman EK	title=Advances in CT Imaging of GI Malignancies.	journal=Gastrointest Cancer Res	year= 2012	volume= 5	issue= 3 Suppl 1	pages= S4-9	pmid=22876336	pmc=3413036 }} or 40 – 50 sec	20–30 sec
70–80 sec	50–60 sec
100 sec	80 sec
180 sec	160 sec
date=December 2019	reason=removed citation to predatory publisher content}} minutes	date=December 2019	reason=removed citation to predatory publisher content}} minutes

Angiography

Main article: CT 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

[[Hepatocellular carcinoma]], without (top) and with (bottom) 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, such as hypersensitivity reactions, contrast-induced nephropathy, effects on thyroid function or adverse drug interactions.

Exam	Iodine concentration	Comments	300 mg/ml	350 mg/ml	370 mg/ml
CT of brain	url=http://www.medsafe.govt.nz/profs/Datasheet/o/Omnipaqueinj.pdf	title=New Zealand Datasheet	website=New Zealand Medicines and Medical Devices Safety Authority	access-date=2018-10-16}}	80 ml	75 ml
CT of thorax	Overall	70–95 ml0.3–0.4 gI/kg in a 70kg individual, according to:
CT pulmonary angiogram	20 mlUsing dual energy CTA (such as 90/150SnkVp), according to:
CT of abdomen	Overall	70 ml	60 ml	55 ml
Liver	55 mlThe liver generally needs an enhancement of at least 30 HU for proper evaluation according to:
CT angiography	25 mlCT-angiography in a 70kg person, with 100-150 mg I/kg by using 80 kVp, mAs-compensation for constant CNR, fixed injection duration adapted to scan time, automatic bolus tracking and a saline chaser, according to:

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:

Exam	Concentration of iodine	300 mg/ml	350 mg/ml
Generally	2.0 ml/kg	1.7 ml/kg
CT of brain, neck or thorax	1.5 ml/kg	1.3 ml/kg

Adverse effects

Iodinated contrast agents may cause allergic reactions, contrast-induced nephropathy, hyperthyroidism and possibly metformin accumulation. However, there are no absolute contraindications to iodinated contrast, so the benefits needs to be weighted against the risks.

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

(2014). "Fundamentals of Body CT". Elsevier Health Sciences.
(2000). "Detection and Characterisation of Renal Lesions by Multiphasic Helical Ct". Acta Radiologica.
(2014). "CT and MR Imaging Diagnosis and Staging of Hepatocellular Carcinoma: Part II. Extracellular Agents, Hepatobiliary Agents, and Ancillary Imaging Features". Radiology.
(2010). "Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches". Radiology.
Robin Smithuis. "CT contrast injection and protocols".
Ákos Jobbágy. (2012). "5th European Conference of the International Federation for Medical and Biological Engineering 14 - 18 September 2011, Budapest, Hungary. Volume 37 of IFMBE Proceedings". Springer Science & Business Media.
Pavan Nandra. (2018). "Introducing the use of Flash CTPA; how does it compare to standard CTPA?".
(2012). "Advances in CT Imaging of GI Malignancies.". Gastrointest Cancer Res.
Otto van Delden and Robin Smithuis. "Pancreas - Carcinoma".
Stuart E. Mirvis, Jorge A. Soto, Kathirkamanathan Shanmuganathan, Joseph Yu, Wayne S. Kubal. (2014). "Problem Solving in Emergency Radiology E-Book". Elsevier Health Sciences.
"New Zealand Datasheet".
(2018). "Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula". BioMed Research International.
(2010). "Multidetector CT in children: current concepts and dose reduction strategies". Pediatric Radiology.
Stacy Goergen. "Iodine-containing contrast medium".
(2019). "What you should know about prophylaxis and treatment of radiographic and magnetic resonance contrast medium extravasation". Acta Radiol.

Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

x-ray-computed-tomography

Want to explore this topic further?

Ask Mako anything about Contrast CT — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report