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[[File:Contrast CT.jpg|thumb|A woman undergoing CT with IV contrast.]]
'''Contrast CT''' is '''[[CT scan]]''' using [[radiocontrast]], and in Radlines it refers to a CT scan using IV contrast except otherwise noted.
'''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.<ref name="ChoiLee2014">{{cite journal|last1=Choi|first1=Jin-Young|last2=Lee|first2=Jeong-Min|last3=Sirlin|first3=Claude B.|title=CT and MR Imaging Diagnosis and Staging of Hepatocellular Carcinoma: Part II. Extracellular Agents, Hepatobiliary Agents, and Ancillary Imaging Features|journal=Radiology|volume=273|issue=1|year=2014|pages=30–50|issn=0033-8419|doi=10.1148/radiol.14132362|pmc=4263770|pmid=25247563}}</ref>
==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.<ref name="Bae2010">{{cite journal|last1=Bae|first1=Kyongtae T.|title=Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches|journal=Radiology|volume=256|issue=1|year=2010|pages=32–61|issn=0033-8419|doi=10.1148/radiol.10090908}}</ref> The main phases thereof are as follows:<ref name=radiologyassistant>{{cite web|url=http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct-contrast-injection-and-protocols.html|title=CT contrast injection and protocols|author=Robin Smithuis|website=Radiology Assistant|accessdate=2017-12-13}}</ref>
{|class="wikitable"
! Phase !! Time from injection<ref name=radiologyassistant/> !! Time from bolus tracking in proximal aorta<ref name=radiologyassistant/> !! Targeted structures and findings<ref name=radiologyassistant/>
|-
! Non-enhanced CT (NECT)
| - || -
|
*Calfications
*Fat in tumors such as in [[adrenocortical adenoma]]s
*Fat-stranding as seen in inflammation such as [[appendicitis]], [[diverticulitis]] and omental infarction
|-
! [[Pulmonary artery|Pulmonary arterial]] phase
| 6-13 sec<ref name=IFMBE>[https://books.google.se/books?id=oVGjnOLXUgkC&pg=PA584 Page 584] in: {{cite book|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=9783642235085}}</ref> || -
|
*[[Pulmonary embolism]]
|-
! [[Pulmonary vein|Pulmonary venous]] phase
| 17-24 sec<ref name=IFMBE/> || - ||
|-
! Early systemic arterial phase
| 15-20 sec || immediately
|
*Arteries, without enhancement of organs and other soft tissues.
|-
! Late systemicarterial phase<br>''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
|-
! [[Pancreas|Pancreatic]] phase
| 30<ref name="pmid22876336">{{cite journal| author=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 | doi= | pmc=3413036 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22876336 }} </ref> or 40<ref name=pancreatic>{{cite web|url=http://www.radiologyassistant.nl/en/p43848b63def9d/pancreas-carcinoma.html|title=Pancreas - Carcinoma|author=Otto van Delden and Robin Smithuis|website=Radiology Assistant|accessdate=2017-12-15}}</ref> - 50<ref name=pancreatic/> sec || 20-30 sec
|
*[[Pancreatic cancer]]s become hypodense compared to the parenchyma.<ref name=pancreatic/>
|-
! 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<ref name=Guite2013>{{cite book|title=Selected Topics on Computed Tomography|author=Dongqing Wang|isbn=9789535111023|year=2013}} License: [https://creativecommons.org/licenses/by/3.0/ CC-BY-3.0]. Chapter 1: "[https://www.intechopen.com/books/selected-topics-on-computed-tomography/computed-tomography-in-abdominal-imaging-how-to-gain-maximum-diagnostic-information-at-the-lowest-ra 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</ref> || 160 sec
|
*Detect [[venous thrombosis]]<ref name=Guite2013/>
|-
! Delayed phase<br>''Sometimes called "wash out phase" or "equilibrium phase"''
| 6<ref name=radiologyassistant/>-15<ref name=Guite2013/> minutes || 6<ref name=radiologyassistant/>-15<ref name=Guite2013/> minutes
|
*Disappearance of contrast in all abdominal structures except for tissue with [[fibrosis]], which appears more radiodense.
|}
==Gastrointestinal contrast==
'''Rectally administered contrast''' is indicated in cases where a suspicion remains of penetrating trauma to the colon where an initial CT shows no reason for immediate surgery.<ref>{{cite web|url=http://www.radiologyassistant.nl/en/p466181ff61073/acute-abdomen-role-of-ct-in-trauma.html#i466184acd2fdb|title=Acute Abdomen - Role of CT in Trauma|author=Stephen Ledbetter and Robin Smithuis|website=Radiopaedia|date=2007-08-02}}</ref>
==References==
{{reflist}}
[[Category:X-ray computed tomography]]
'''Contrast CT''' is '''[[CT scan]]''' using [[radiocontrast]], and in Radlines it refers to a CT scan using IV contrast except otherwise noted.
'''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.<ref name="ChoiLee2014">{{cite journal|last1=Choi|first1=Jin-Young|last2=Lee|first2=Jeong-Min|last3=Sirlin|first3=Claude B.|title=CT and MR Imaging Diagnosis and Staging of Hepatocellular Carcinoma: Part II. Extracellular Agents, Hepatobiliary Agents, and Ancillary Imaging Features|journal=Radiology|volume=273|issue=1|year=2014|pages=30–50|issn=0033-8419|doi=10.1148/radiol.14132362|pmc=4263770|pmid=25247563}}</ref>
==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.<ref name="Bae2010">{{cite journal|last1=Bae|first1=Kyongtae T.|title=Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches|journal=Radiology|volume=256|issue=1|year=2010|pages=32–61|issn=0033-8419|doi=10.1148/radiol.10090908}}</ref> The main phases thereof are as follows:<ref name=radiologyassistant>{{cite web|url=http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct-contrast-injection-and-protocols.html|title=CT contrast injection and protocols|author=Robin Smithuis|website=Radiology Assistant|accessdate=2017-12-13}}</ref>
{|class="wikitable"
! Phase !! Time from injection<ref name=radiologyassistant/> !! Time from bolus tracking in proximal aorta<ref name=radiologyassistant/> !! Targeted structures and findings<ref name=radiologyassistant/>
|-
! Non-enhanced CT (NECT)
| - || -
|
*Calfications
*Fat in tumors such as in [[adrenocortical adenoma]]s
*Fat-stranding as seen in inflammation such as [[appendicitis]], [[diverticulitis]] and omental infarction
|-
! [[Pulmonary artery|Pulmonary arterial]] phase
| 6-13 sec<ref name=IFMBE>[https://books.google.se/books?id=oVGjnOLXUgkC&pg=PA584 Page 584] in: {{cite book|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=9783642235085}}</ref> || -
|
*[[Pulmonary embolism]]
|-
! [[Pulmonary vein|Pulmonary venous]] phase
| 17-24 sec<ref name=IFMBE/> || - ||
|-
! Early systemic arterial phase
| 15-20 sec || immediately
|
*Arteries, without enhancement of organs and other soft tissues.
|-
! Late systemicarterial phase<br>''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
|-
! [[Pancreas|Pancreatic]] phase
| 30<ref name="pmid22876336">{{cite journal| author=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 | doi= | pmc=3413036 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22876336 }} </ref> or 40<ref name=pancreatic>{{cite web|url=http://www.radiologyassistant.nl/en/p43848b63def9d/pancreas-carcinoma.html|title=Pancreas - Carcinoma|author=Otto van Delden and Robin Smithuis|website=Radiology Assistant|accessdate=2017-12-15}}</ref> - 50<ref name=pancreatic/> sec || 20-30 sec
|
*[[Pancreatic cancer]]s become hypodense compared to the parenchyma.<ref name=pancreatic/>
|-
! 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<ref name=Guite2013>{{cite book|title=Selected Topics on Computed Tomography|author=Dongqing Wang|isbn=9789535111023|year=2013}} License: [https://creativecommons.org/licenses/by/3.0/ CC-BY-3.0]. Chapter 1: "[https://www.intechopen.com/books/selected-topics-on-computed-tomography/computed-tomography-in-abdominal-imaging-how-to-gain-maximum-diagnostic-information-at-the-lowest-ra 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</ref> || 160 sec
|
*Detect [[venous thrombosis]]<ref name=Guite2013/>
|-
! Delayed phase<br>''Sometimes called "wash out phase" or "equilibrium phase"''
| 6<ref name=radiologyassistant/>-15<ref name=Guite2013/> minutes || 6<ref name=radiologyassistant/>-15<ref name=Guite2013/> minutes
|
*Disappearance of contrast in all abdominal structures except for tissue with [[fibrosis]], which appears more radiodense.
|}
==Gastrointestinal contrast==
'''Rectally administered contrast''' is indicated in cases where a suspicion remains of penetrating trauma to the colon where an initial CT shows no reason for immediate surgery.<ref>{{cite web|url=http://www.radiologyassistant.nl/en/p466181ff61073/acute-abdomen-role-of-ct-in-trauma.html#i466184acd2fdb|title=Acute Abdomen - Role of CT in Trauma|author=Stephen Ledbetter and Robin Smithuis|website=Radiopaedia|date=2007-08-02}}</ref>
==References==
{{reflist}}
[[Category:X-ray computed tomography]]
