# Contrast CT

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Medical imaging technique

A woman undergoing [CT pulmonary angiogram](/source/CT_pulmonary_angiogram), a contrast CT scan of the [pulmonary arteries](/source/Pulmonary_artery), because of suspected [pulmonary embolism](/source/Pulmonary_embolism). A contrast delivery system is connected to a [peripheral venous catheter](/source/Peripheral_venous_catheter) in her left arm.

A [CT pulmonary angiogram](/source/CT_pulmonary_angiogram), in this case showing [pulmonary embolism](/source/Pulmonary_embolism) of saddle-type, which becomes more [radiolucent](/source/Radiodensity) than the [radiocontrast](/source/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](/source/CT_scan) (CT) using [radiocontrast](/source/Radiocontrast). Radiocontrasts for X-ray CT are generally [iodine-based types](/source/Iodinated_contrast).[1] 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.[2]

## Bolus tracking

Volume Rendered Carotid Angiogram

**Bolus tracking** is a technique to optimize timing of the imaging. A small [bolus](/source/Bolus_(medicine)) of radio-opaque contrast media is [injected](/source/Injection_(medicine)) into a patient via a peripheral intravenous [cannula](/source/Cannula). Depending on the vessel being imaged, the volume of contrast is tracked using a [region of interest](/source/Region_of_interest) (abbreviated "R.O.I.") at a certain level and then followed by the [CT scanner](/source/Computed_tomography) once it reaches this level. Images are acquired at a rate as fast as the contrast moving through the blood vessels.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

This method of imaging is used primarily to produce images of arteries, such as the [aorta](/source/Aorta), [pulmonary](/source/Pulmonary_artery) artery, [cerebral](/source/Cerebral_artery), [carotid](/source/Carotid_artery) and hepatic arteries.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

## 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](/source/Hepatocellular_carcinoma) as compared to the rest of the liver parenchyma.[3]

## 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.[4] The main phases thereof are as follows:[5]

Phase Time from injection[5] Time from bolus tracking[5] Targeted structures and findings[5] Non-enhanced CT (NECT) - - Calcifications Fat in tumors such as in adrenocortical adenomas Fat-stranding as seen in inflammation such as appendicitis, diverticulitis and omental infarction Pulmonary arterial phase 6–13 sec[6] - Pulmonary embolism (can use bolus tracking in pulmonary trunk + 6 seconds)[7] Pulmonary venous phase 17–24 sec[6] - 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[8] or 40[9] – 50[9] sec 20–30 sec Pancreatic cancers become hypodense compared to the parenchyma.[9] 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[citation needed] 160 sec Detect venous thrombosis[citation needed] Delayed phase Sometimes called "wash out phase" or "equilibrium phase" 6[5]–15[citation needed] minutes 6[5]–15[citation needed] minutes Disappearance of contrast in all abdominal structures except for tissue with fibrosis, which appears more radiodense.

## Angiography

Main article: [CT angiography](/source/CT_angiography)

[CT angiography](/source/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](/source/Vascular_disease). 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](/source/Aortic_dissection).[10]

## Amount

[Hepatocellular carcinoma](/source/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](/source/Iodinated_contrast#Adverse_effects), such as hypersensitivity reactions, [contrast-induced nephropathy](/source/Contrast-induced_nephropathy), effects on thyroid function or adverse [drug interactions](/source/Drug_interaction).[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

Sufficient volume for normal weight adults Exam Iodine concentration Comments 300 mg/ml 350 mg/ml 370 mg/ml CT of brain 95ml[11] 80 ml[11] 75 ml[11] CT of thorax Overall 70–95 ml[notes 1] 60–80 ml[notes 1] 55–75 ml[notes 1] Parenchymal changes of the lung can often be evaluated adequately without the use of intravenous contrast. CT pulmonary angiogram 20 ml[notes 2] 17 ml[notes 2] 15 ml[notes 2] Minimal amount when using specific low-contrast protocol.[notes 2] CT of abdomen Overall 70 ml[11] 60 ml[11] 55 ml[11] Liver 55 ml[notes 3] 45 ml[notes 3] 40–45 ml[notes 3] Minimal required amount.[notes 3] CT angiography 25 ml[notes 4] 20 ml[notes 4] When using specific low-contrast protocol.[notes 4]

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](/source/Lean_body_mass) of the person. In [obese](/source/Obesity) patients, the Boer formula is the method of choice (at least in those with [body mass index](/source/Body_mass_index) (BMI) between 35 and 40):[12]

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:[13]

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

Further information: [Iodinated contrast § Adverse effects](/source/Iodinated_contrast#Adverse_effects), and [CT scan § Cancer](/source/CT_scan#Cancer)

Iodinated [contrast agents](/source/Contrast_agent) may cause allergic reactions, [contrast-induced nephropathy](/source/Contrast-induced_nephropathy), [hyperthyroidism](/source/Hyperthyroidism) and possibly [metformin](/source/Metformin) accumulation. However, there are no absolute contraindications to iodinated contrast, so the benefits needs to be weighted against the risks.[14]

As with CT scans in general, the radiation dose can potentially increase the risk of [radiation-induced cancer](/source/Radiation-induced_cancer).

The injection of iodinated contrast agents may sometimes lead to its extravasation.[15]

## See also

- [Computed tomography of the abdomen and pelvis#Contrast administration](/source/Computed_tomography_of_the_abdomen_and_pelvis#Contrast_administration)

## Notes

1. ^ [***a***](#cite_ref-IezziLarici2017_12-0) [***b***](#cite_ref-IezziLarici2017_12-1) [***c***](#cite_ref-IezziLarici2017_12-2) 0.3–0.4 gI/kg in a 70kg individual, according to: - Iezzi, Roberto; Larici, Anna Rita; Franchi, Paola; Marano, Riccardo; Magarelli, Nicola; Posa, Alessandro; Merlino, Biagio; Manfredi, Riccardo; Colosimo, Cesare (2017). ["Tailoring protocols for chest CT applications: when and how?"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5669541). *Diagnostic and Interventional Radiology*. **23** (6): 420–427. [doi](/source/Doi_(identifier)):[10.5152/dir.2017.16615](https://doi.org/10.5152%2Fdir.2017.16615). [ISSN](/source/ISSN_(identifier)) [1305-3825](https://search.worldcat.org/issn/1305-3825). [PMC](/source/PMC_(identifier)) [5669541](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5669541). [PMID](/source/PMID_(identifier)) [29097345](https://pubmed.ncbi.nlm.nih.gov/29097345).

1. ^ [***a***](#cite_ref-LeroyerMeier2016_13-0) [***b***](#cite_ref-LeroyerMeier2016_13-1) [***c***](#cite_ref-LeroyerMeier2016_13-2) [***d***](#cite_ref-LeroyerMeier2016_13-3) Using dual energy CTA (such as 90/150SnkVp), according to: - Leroyer, Christophe; Meier, Andreas; Higashigaito, Kai; Martini, Katharina; Wurnig, Moritz; Seifert, Burkhardt; Keller, Dagmar; Frauenfelder, Thomas; Alkadhi, Hatem (2016). ["Dual Energy CT Pulmonary Angiography with 6g Iodine—A Propensity Score-Matched Study"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132396). *PLOS ONE*. **11** (12) e0167214. [Bibcode](/source/Bibcode_(identifier)):[2016PLoSO..1167214M](https://ui.adsabs.harvard.edu/abs/2016PLoSO..1167214M). [doi](/source/Doi_(identifier)):[10.1371/journal.pone.0167214](https://doi.org/10.1371%2Fjournal.pone.0167214). [ISSN](/source/ISSN_(identifier)) [1932-6203](https://search.worldcat.org/issn/1932-6203). [PMC](/source/PMC_(identifier)) [5132396](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132396). [PMID](/source/PMID_(identifier)) [27907049](https://pubmed.ncbi.nlm.nih.gov/27907049).

1. ^ [***a***](#cite_ref-Liver_14-0) [***b***](#cite_ref-Liver_14-1) [***c***](#cite_ref-Liver_14-2) [***d***](#cite_ref-Liver_14-3) The liver generally needs an enhancement of at least 30 HU for proper evaluation according to: - *Multislice CT* (3 ed.). Springer-Verlag Berlin and Heidelberg GmbH & Co. KG. 2010. [ISBN](/source/ISBN_(identifier)) [978-3-642-06968-0](https://en.wikipedia.org/wiki/Special:BookSources/978-3-642-06968-0). In males at 30 years of age, there is an estimated 0.027 HU of liver parenchymal enhancement per kilogram of body weight and per gram of iodine, when injected at 4 ml per second, according to: - Bae, Kyongtae T. (2010). ["Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches"](https://doi.org/10.1148%2Fradiol.10090908). *Radiology*. **256** (1): 32–61. [doi](/source/Doi_(identifier)):[10.1148/radiol.10090908](https://doi.org/10.1148%2Fradiol.10090908). [ISSN](/source/ISSN_(identifier)) [0033-8419](https://search.worldcat.org/issn/0033-8419). [PMID](/source/PMID_(identifier)) [20574084](https://pubmed.ncbi.nlm.nih.gov/20574084). This example takes the example of a man with a typical weight of 70 kg.

1. ^ [***a***](#cite_ref-Angiography_15-0) [***b***](#cite_ref-Angiography_15-1) [***c***](#cite_ref-Angiography_15-2) CT-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: - Nyman, Ulf (2012). "Contrast Medium-Induced Nephropathy (CIN) Gram-Iodine/GFR Ratio to Predict CIN and Strategies to Reduce Contrast Medium Doses". *Coronary Interventions*. [doi](/source/Doi_(identifier)):[10.5772/29992](https://doi.org/10.5772%2F29992). [ISBN](/source/ISBN_(identifier)) [978-953-51-0498-8](https://en.wikipedia.org/wiki/Special:BookSources/978-953-51-0498-8).

## References

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1. **[^](#cite_ref-2)** Dahlman P, Semenas E, Brekkan E, Bergman A, Magnusson A (2000). "Detection and Characterisation of Renal Lesions by Multiphasic Helical Ct". *Acta Radiologica*. **41** (4): 361–366. [doi](/source/Doi_(identifier)):[10.1080/028418500127345479](https://doi.org/10.1080%2F028418500127345479). [PMID](/source/PMID_(identifier)) [10937759](https://pubmed.ncbi.nlm.nih.gov/10937759). [S2CID](/source/S2CID_(identifier)) [27758886](https://api.semanticscholar.org/CorpusID:27758886).

1. **[^](#cite_ref-ChoiLee2014_3-0)** 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"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4263770). *Radiology*. **273** (1): 30–50. [doi](/source/Doi_(identifier)):[10.1148/radiol.14132362](https://doi.org/10.1148%2Fradiol.14132362). [ISSN](/source/ISSN_(identifier)) [0033-8419](https://search.worldcat.org/issn/0033-8419). [PMC](/source/PMC_(identifier)) [4263770](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4263770). [PMID](/source/PMID_(identifier)) [25247563](https://pubmed.ncbi.nlm.nih.gov/25247563).

1. **[^](#cite_ref-Bae2010_4-0)** Bae, Kyongtae T. (2010). ["Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches"](https://doi.org/10.1148%2Fradiol.10090908). *Radiology*. **256** (1): 32–61. [doi](/source/Doi_(identifier)):[10.1148/radiol.10090908](https://doi.org/10.1148%2Fradiol.10090908). [ISSN](/source/ISSN_(identifier)) [0033-8419](https://search.worldcat.org/issn/0033-8419). [PMID](/source/PMID_(identifier)) [20574084](https://pubmed.ncbi.nlm.nih.gov/20574084).

1. ^ [***a***](#cite_ref-radiologyassistant_5-0) [***b***](#cite_ref-radiologyassistant_5-1) [***c***](#cite_ref-radiologyassistant_5-2) [***d***](#cite_ref-radiologyassistant_5-3) [***e***](#cite_ref-radiologyassistant_5-4) [***f***](#cite_ref-radiologyassistant_5-5) Robin Smithuis. ["CT contrast injection and protocols"](http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct-contrast-injection-and-protocols.html). *Radiology Assistant*. Retrieved 2017-12-13.

1. ^ [***a***](#cite_ref-IFMBE_6-0) [***b***](#cite_ref-IFMBE_6-1) [Page 584](https://books.google.com/books?id=oVGjnOLXUgkC&pg=PA584) 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](/source/ISBN_(identifier)) [978-3-642-23508-5](https://en.wikipedia.org/wiki/Special:BookSources/978-3-642-23508-5).

1. **[^](#cite_ref-7)** Pavan Nandra (2018). ["Introducing the use of Flash CTPA; how does it compare to standard CTPA?"](https://posterng.netkey.at/esr/viewing/index.php?module=viewing_poster&doi=10.1594/ecr2018/C-1831). *Postering*. [doi](/source/Doi_(identifier)):[10.1594/ecr2018/C-1831](https://doi.org/10.1594%2Fecr2018%2FC-1831).

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1. ^ [***a***](#cite_ref-pancreatic_9-0) [***b***](#cite_ref-pancreatic_9-1) [***c***](#cite_ref-pancreatic_9-2) Otto van Delden and Robin Smithuis. ["Pancreas - Carcinoma"](https://web.archive.org/web/20190926032743/http://www.radiologyassistant.nl/en/p43848b63def9d/pancreas-carcinoma.html). *Radiology Assistant*. Archived from [the original](http://www.radiologyassistant.nl/en/p43848b63def9d/pancreas-carcinoma.html) on 2019-09-26. Retrieved 2017-12-15.

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1. ^ [***a***](#cite_ref-NZ_11-0) [***b***](#cite_ref-NZ_11-1) [***c***](#cite_ref-NZ_11-2) [***d***](#cite_ref-NZ_11-3) [***e***](#cite_ref-NZ_11-4) [***f***](#cite_ref-NZ_11-5) ["New Zealand Datasheet"](http://www.medsafe.govt.nz/profs/Datasheet/o/Omnipaqueinj.pdf) (PDF). *New Zealand Medicines and Medical Devices Safety Authority*. Retrieved 2018-10-16.

1. **[^](#cite_ref-CarusoDe_Santis2018_16-0)** Caruso, Damiano; De Santis, Domenico; Rivosecchi, Flaminia; Zerunian, Marta; Panvini, Nicola; Montesano, Marta; Biondi, Tommaso; Bellini, Davide; Rengo, Marco; Laghi, Andrea (2018). ["Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110034). *BioMed Research International*. **2018**: 1–6. [doi](/source/Doi_(identifier)):[10.1155/2018/8521893](https://doi.org/10.1155%2F2018%2F8521893). [ISSN](/source/ISSN_(identifier)) [2314-6133](https://search.worldcat.org/issn/2314-6133). [PMC](/source/PMC_(identifier)) [6110034](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110034). [PMID](/source/PMID_(identifier)) [30186869](https://pubmed.ncbi.nlm.nih.gov/30186869).

1. **[^](#cite_ref-Nievelsteinvan_Dam2010_17-0)** Nievelstein, Rutger A. J.; van Dam, Ingrid M.; van der Molen, Aart J. (2010). ["Multidetector CT in children: current concepts and dose reduction strategies"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2895901). *Pediatric Radiology*. **40** (8): 1324–1344. [doi](/source/Doi_(identifier)):[10.1007/s00247-010-1714-7](https://doi.org/10.1007%2Fs00247-010-1714-7). [ISSN](/source/ISSN_(identifier)) [0301-0449](https://search.worldcat.org/issn/0301-0449). [PMC](/source/PMC_(identifier)) [2895901](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2895901). [PMID](/source/PMID_(identifier)) [20535463](https://pubmed.ncbi.nlm.nih.gov/20535463).

1. **[^](#cite_ref-18)** Stacy Goergen. ["Iodine-containing contrast medium"](https://www.insideradiology.com.au/iodine-containing-contrast-medium-hp/). *InsideRadiology - The Royal Australian and New Zealand College of Radiologists*. Retrieved 2019-02-22. Page last modified on 26/7/2017

1. **[^](#cite_ref-pmid29896979_19-0)** Hrycyk J, Heverhagen JT, Böhm I (2019). "What you should know about prophylaxis and treatment of radiographic and magnetic resonance contrast medium extravasation". *Acta Radiol*. **60** (4): 496–500. [doi](/source/Doi_(identifier)):[10.1177/0284185118782000](https://doi.org/10.1177%2F0284185118782000). [PMID](/source/PMID_(identifier)) [29896979](https://pubmed.ncbi.nlm.nih.gov/29896979). [S2CID](/source/S2CID_(identifier)) [48360725](https://api.semanticscholar.org/CorpusID:48360725).

## External links

- ["CT with IV contrast in low renal function"](https://radlines.org/CT_with_IV_contrast_in_low_renal_function). *Radlines.org*.

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Adapted from the Wikipedia article [Contrast CT](https://en.wikipedia.org/wiki/Contrast_CT) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Contrast_CT?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.