CT with IV contrast

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A woman undergoing CT with IV contrast.

Author: Mikael Häggström [notes 1]
Computed tomography (CT) with intravenous (IV) contrast medium:

Related terms

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.[1]

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.[2]

When it matters

According to European guidelines, the main risk factors of contrast-induced nephropathy:[3]

  • 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
In case of low GFR, other risk factors need to be checked. Subsequently, the procedure depends on whether the dose that can be given is larger or less than the needed dose.

Further reading: CT with IV contrast in low renal function

Allergy

Intramuscular site of adrenaline.jpg
Main article: Contrast medium reaction

In a more severe reaction:[4]

  • Adrenaline shot, 0.3-0.5mg in adults, given intramuscularly.
  • Summon an anesthesiologist

Prevention

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.[5]

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.[6] The main phases thereof are as follows in table below.[7]

CT angiography is a CT scan corresponding with contrast filling one or more blood vessels of interest.

Phase Time from injection[7] Time from bolus tracking in proximal aorta[7] Targeted structures and findings[7]
Non-enhanced CT (NECT) - -
Pulmonary arterial phase 6-13 sec[8] -
Pulmonary venous phase 17-24 sec[8] -
Early systemic arterial phase 15-20 sec immediately
  • Arteries, without enhancement of organs and other soft tissues.
Late systemicarterial phase
Sometimes also called "arterial phase" or "early venous portal phase"
35-40 sec 15-20 sec
  • All structures that get their blood supply from the arteries have optimal enhancement.
  • Some enhancement of the portal vein
Pancreatic phase 30[9] or 40[10] - 50[10] sec 20-30 sec
Hepatic (most accurate) or late portal phase 70-80 sec 50-60 sec
  • Liver parenchyma enhances through portal vein supply, normally with some enhancement of the hepatic veins.
Nephrogenic phase 100 sec 80 sec
  • All of the renal parenchyma enhances, including the medulla, allowing detection of small renal cell carcinomas
Systemic venous phase 180 sec[11] 160 sec
Delayed phase
Sometimes called "wash out phase" or "equilibrium phase"
6[7]-15[11] minutes 6[7]-15[11] minutes
  • Disappearance of contrast in all abdominal structures except for tissue with fibrosis, which appears more radiodense.

Locations

See CT#By location (CT with IV contrast, including CT angiography, is organized as other CT examinations).

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.

References

  1. Choi, Jin-Young; Lee, Jeong-Min; Sirlin, Claude B. (2014). "CT and MR Imaging Diagnosis and Staging of Hepatocellular Carcinoma: Part II. Extracellular Agents, Hepatobiliary Agents, and Ancillary Imaging Features ". Radiology 273 (1): 30–50. doi:10.1148/radiol.14132362. ISSN 0033-8419. PMID 25247563. 
  2. Rudnick, M.; Feldman, H. (2008). "Contrast-Induced Nephropathy: What Are the True Clinical Consequences? ". Clinical Journal of the American Society of Nephrology 3 (1): 263–272. doi:10.2215/CJN.03690907. ISSN 1555-9041. 
  3. Nyman, Ulf; Ahlkvist, Joanna; Aspelin, Peter; Brismar, Torkel; Frid, Anders; Hellström, Mikael; Liss, Per; Sterner, Gunnar; et al. (2018). "Preventing contrast medium-induced acute kidney injury ". European Radiology. doi:10.1007/s00330-018-5678-6. ISSN 0938-7994. 
  4. Unless otherwise specified in lists and table: . Hypersensitivity reactions against contrast media - Swedish Society of Uroradiology [Swedish: Överkänslighetsreaktioner mot kontrastmedel – SURFs kontrastmedelsgrupp ], 2014-10-17].
  5. Error on call to Template:cite web: Parameters url and title must be specified. . American College of Radiology, Committee on Drugs and Contrast Media. Retrieved on 2018-08-25. Version 10.3. 2018. ACR
  6. Bae, Kyongtae T. (2010). "Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches ". Radiology 256 (1): 32–61. doi:10.1148/radiol.10090908. ISSN 0033-8419. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Robin Smithuis. CT contrast injection and protocols. Radiology Assistant. Retrieved on 2017-12-13.
  8. 8.0 8.1 Page 584 in: 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. ISBN 9783642235085. 
  9. Raman SP, Fishman EK (2012). "Advances in CT Imaging of GI Malignancies. ". Gastrointest Cancer Res 5 (3 Suppl 1): S4-9. PMID 22876336. PMC: 3413036. Archived from the original. . 
  10. 10.0 10.1 10.2 Otto van Delden and Robin Smithuis. Pancreas - Carcinoma. Radiology Assistant. Retrieved on 2017-12-15.
  11. 11.0 11.1 11.2 11.3 Dongqing Wang (2013). Selected Topics on Computed Tomography . ISBN 9789535111023.  License: CC-BY-3.0. Chapter 1: "Computed Tomography in Abdominal Imaging: How to Gain Maximum Diagnostic Information at the Lowest Radiation Dose" by Kristie Guite, Louis Hinshaw and Fred Lee. DOI: 10.5772/55903