Contrast CT
Contrast CT, or contrast enhanced computed tomography (CECT), is
Bolus tracking
Bolus tracking is a technique to optimize timing of the imaging. A small
This method of imaging is used primarily to produce images of arteries, such as the
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) | - | - |
|
Pulmonary arterial phase | 6-13 sec[6] | - |
|
Pulmonary venous phase | 17-24 sec[6] | - | |
Early systemic arterial phase | 15-20 sec | immediately |
|
Late systemicarterial phase Sometimes also called "arterial phase" or "early venous portal phase" |
35-40 sec | 15-20 sec |
|
Pancreatic phase | 30[8] or 40[9] - 50[9] sec | 20-30 sec |
|
Hepatic (most accurate) or late portal phase | 70-80 sec | 50-60 sec |
|
Nephrogenic phase | 100 sec | 80 sec |
|
Systemic venous phase | 180 sec[citation needed] | 160 sec |
|
Delayed phase Sometimes called "wash out phase" or "equilibrium phase" |
6[5]-15[citation needed] minutes | 6[5]-15[citation needed] minutes |
|
Angiography
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.
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 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):[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
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.[14]
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.[15]
See also
Notes
- ^ a b c 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?". Diagnostic and Interventional Radiology. 23 (6): 420–427. PMID 29097345.
- 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?". Diagnostic and Interventional Radiology. 23 (6): 420–427.
- ^ a b c d 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". PLOS ONE. 11 (12): e0167214. PMID 27907049.
- 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". PLOS ONE. 11 (12): e0167214.
- ^ a b c d 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 9783642069680.
- Bae, Kyongtae T. (2010). "Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches". Radiology. 256 (1): 32–61. PMID 20574084.
- Multislice CT (3 ed.). Springer-Verlag Berlin and Heidelberg GmbH & Co. KG. 2010.
- ^ a b c 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. ISBN 978-953-51-0498-8.
- Nyman, Ulf (2012). "Contrast Medium-Induced Nephropathy (CIN) Gram-Iodine/GFR Ratio to Predict CIN and Strategies to Reduce Contrast Medium Doses". Coronary Interventions.
References
- ISBN 9780323263580.
- S2CID 27758886.
- PMID 25247563.
- PMID 20574084.
- ^ a b c d e f Robin Smithuis. "CT contrast injection and protocols". Radiology Assistant. Retrieved 2017-12-13.
- ^ ISBN 9783642235085.
- .
- PMID 22876336.
- ^ a b c Otto van Delden and Robin Smithuis. "Pancreas - Carcinoma". Radiology Assistant. Archived from the original on 2019-09-26. Retrieved 2017-12-15.
- ISBN 9781455758395.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - ^ a b c d e f "New Zealand Datasheet" (PDF). New Zealand Medicines and Medical Devices Safety Authority. Retrieved 2018-10-16.
- PMID 30186869.
- PMID 20535463.
- ^ Stacy Goergen. "Iodine-containing contrast medium". InsideRadiology - The Royal Australian and New Zealand College of Radiologists. Retrieved 2019-02-22. Page last modified on 26/7/2017
- S2CID 48360725.
External links
- "CT with IV contrast in low renal function". Radlines.org.