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词条 Contrast CT
释义

  1. Bolus tracking

  2. Washout

  3. Phases

  4. Angiography

  5. Amount

     Adults  Children 

  6. Adverse effects

  7. See also

  8. Notes

  9. References

  10. External links

Contrast CT is X-ray computed tomography (CT) using radiocontrast. Radiocontrasts for X-ray CT are, in general, iodine-based types.[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 administrated, and postcontrast after radiocontrast administration.[2]

Bolus tracking

Bolus tracking is a technique used in computed tomography imaging 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.[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) - -
  • Calfications
  • 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
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[7] or 40[8] - 50[8] sec 20-30 sec
  • Pancreatic cancers become hypodense compared to the parenchyma.[8]
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[9] 160 sec
  • Detect venous thrombosis[9]
Delayed phase
Sometimes called "wash out phase" or "equilibrium phase"		 6[5]-15[9] minutes 6[5]-15[9] minutes
  • Disappearance of contrast in all abdominal structures except for tissue with fibrosis, which appears more radiodense.

Angiography

{{main|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.[10]

Amount

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.

Sufficient volume for normal weight adults
ExamIodine concentrationComments
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[12] 60 - 80 ml[12] 55 - 75 ml[12] Parenchymal changes of the lung can often be evaluated adequately without the use of intravenous contrast.
CT pulmonary angiogram 20 ml[13] 17 ml[13] 15 ml[13] Minimal amount when using specific low-contrast protocol.[13]
CT of abdomen Overall 70 ml[11] 60 ml[11] 55 ml[11]
Liver 55 ml[14] 45 ml[14] 40-45 ml[14] Minimal required amount.[14]
CT angiography 25 ml[15] 20 ml[15] When using specific low-contrast protocol.[15]

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):[16]

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:[17]

ExamConcentration 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|Iodinated contrast#Adverse effects|CT scan#Cancer}}

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.[18]

As with CT scans in general, the radiation dose can potentially increase the risk of radiation-induced cancer.

See also

  • Computed tomography of the abdomen and pelvis#Contrast administration

Notes

1. ^{{cite book|last1=Webb|first1=W. Richard|last2=Brant|first2=Wiliam E.|last3=Major|first3=Nancy M.|title=Fundamentals of Body CT|date=2014|publisher=Elsevier Health Sciences|isbn=9780323263580|page=152|url=https://books.google.com/books?id=lcjsAwAAQBAJ&pg=PA152|language=en}}
2. ^{{cite journal |vauthors=Dahlman P, Semenas E, Brekkan E, Bergman A, Magnusson A | title = Detection and Characterisation of Renal Lesions by Multiphasic Helical Ct | journal = Acta Radiologica | volume = 41 | issue = 4 | pages = 361–366 | year = 2000 | pmid = 10937759 | pmc = | doi = 10.1080/028418500127345479 }}
3. ^{{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}}
4. ^{{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}}
5. ^1 2 3 4 5 {{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}}
6. ^1 [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}}
7. ^{{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 }}
8. ^1 2 {{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}}
9. ^1 2 3 {{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
10. ^[https://books.google.com/books?id=E3tYBAAAQBAJ&pg=PA424 Page 424] in: {{cite book|title=Problem Solving in Emergency Radiology E-Book|author=Stuart E. Mirvis, Jorge A Soto, Kathirkamanathan Shanmuganathan, Joseph Yu, Wayne S Kubal|publisher=Elsevier Health Sciences|year=2014|isbn=9781455758395}}
11. ^1 2 3 4 5 {{cite web|url=http://www.medsafe.govt.nz/profs/Datasheet/o/Omnipaqueinj.pdf|title=New Zealand Datasheet|website=New Zealand Medicines and Medical Devices Safety Authority|accessdate=2018-10-16}}
12. ^1 2 0.3–0.4 gI/kg in a 70kg individual, according to*{{cite journal|last1=Iezzi|first1=Roberto|last2=Larici|first2=Anna Rita|last3=Franchi|first3=Paola|last4=Marano|first4=Riccardo|last5=Magarelli|first5=Nicola|last6=Posa|first6=Alessandro|last7=Merlino|first7=Biagio|last8=Manfredi|first8=Riccardo|last9=Colosimo|first9=Cesare|title=Tailoring protocols for chest CT applications: when and how?|journal=Diagnostic and Interventional Radiology|volume=23|issue=6|year=2017|pages=420–427|issn=13053825|doi=10.5152/dir.2017.16615}}
13. ^1 2 3 Using dual energy CTA (such as 90/150SnkVp), according to*{{cite journal|last1=Leroyer|first1=Christophe|last2=Meier|first2=Andreas|last3=Higashigaito|first3=Kai|last4=Martini|first4=Katharina|last5=Wurnig|first5=Moritz|last6=Seifert|first6=Burkhardt|last7=Keller|first7=Dagmar|last8=Frauenfelder|first8=Thomas|last9=Alkadhi|first9=Hatem|title=Dual Energy CT Pulmonary Angiography with 6g Iodine—A Propensity Score-Matched Study|journal=PLOS ONE|volume=11|issue=12|year=2016|pages=e0167214|issn=1932-6203|doi=10.1371/journal.pone.0167214}}
14. ^1 2 3 The liver generally needs an enhancement of at least 30 HU for proper evaluation according to*{{cite book|title=Multislice CT|edition=3|year=2010|publisher=Springer-Verlag Berlin and Heidelberg GmbH & Co. KG|isbn=9783642069680}}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*{{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}}This example takes the example of a man with a typical weight of 70 kg.
15. ^1 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*{{cite journal|last1=Nyman|first1=Ulf|title=Contrast Medium-Induced Nephropathy (CIN) Gram-Iodine/GFR Ratio to Predict CIN and Strategies to Reduce Contrast Medium Doses|year=2012|doi=10.5772/29992}}
16. ^{{cite journal|last1=Caruso|first1=Damiano|last2=De Santis|first2=Domenico|last3=Rivosecchi|first3=Flaminia|last4=Zerunian|first4=Marta|last5=Panvini|first5=Nicola|last6=Montesano|first6=Marta|last7=Biondi|first7=Tommaso|last8=Bellini|first8=Davide|last9=Rengo|first9=Marco|last10=Laghi|first10=Andrea|title=Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula|journal=BioMed Research International|volume=2018|year=2018|pages=1–6|issn=2314-6133|doi=10.1155/2018/8521893}}
17. ^{{cite journal|last1=Nievelstein|first1=Rutger A. J.|last2=van Dam|first2=Ingrid M.|last3=van der Molen|first3=Aart J.|title=Multidetector CT in children: current concepts and dose reduction strategies|journal=Pediatric Radiology|volume=40|issue=8|year=2010|pages=1324–1344|issn=0301-0449|doi=10.1007/s00247-010-1714-7}}
18. ^{{cite web|title=Iodine-containing contrast medium|author=Stacy Goergen|website=InsideRadiology - The Royal Australian and New Zealand College of Radiologists|url=https://www.insideradiology.com.au/iodine-containing-contrast-medium-hp/|accessdate=2019-02-22}} Page last modified on 26/7/2017

References

{{reflist}}

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}}

1 : X-ray computed tomography
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