CT with IV contrast
Author:
Mikael Häggström [notes 1]
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.[1]
Contents
Contrast-induced nephropathy
Risk factors
The Roxana Mehran score predictor applies the following ten variables:[2]
- Age (4 points if older than 75 years old)
- Anemia (3 points)
- Use of an intra-aortic balloon pump (5 points)
- eGFR 60 to 40 (2 points)
- eGFR 40 to 20 (4 points)
- eGFR less than 20 (6 points)
- Hypotension (5 points, if systolic BP less than 80 mmHg for at least one hour requiring inotropic support)
- Contrast media volume (1 point per 100 ml)
- Congestive heart failure (5 points)
- Diabetes (3 points).
A risk score of less than 6 carries a risk of 7.5% to score more than 16 carries up to 57% risk.
Alternatives
In people with risk factors, the main alternatives are:
- Adjustment of the contrast dose. Evidence suggests that contrast doses should be limited to a ratio of grams of iodine to glomerular filtration rate (Igram / GFRml/min) of a maximum of 1.[3] The local practice at NU Hospital Group has a Igram/GFR ratio of maximum 0.7 in patients with GFR ≥45 ml/min. It recommends a ratio of maximum 0.5 if GFR is lower, or in the presence of risk factors.
| Iodine concentration |
1 | 0.7 | 0.5 |
|---|---|---|---|
| 240 mg/ml | 4.2 ml *GFRml/min | 2.9 ml *GFRml/min | 2.1 ml *GFRml/min |
| 350 mg/ml | 2.9 ml *GFRml/min | 2 ml *GFRml/min | 1.4 ml *GFRml/min |
- Using no intravenous contrast' for the investigation.
- Switching to another modality such as ultrasonography or MRI
- Treating or mitigating risk factors.
- Hydration by drinking or intravenous volume expander, either before or after contract administration, decreases the risk of contrast-induced nephropathy.[4]
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.[5] The main phases thereof are as follows:[6]
| Phase | Time from injection[6] | Time from bolus tracking in proximal aorta[6] | Targeted structures and findings[6] |
|---|---|---|---|
| Non-enhanced CT (NECT) | - | - |
|
| Pulmonary arterial phase | 6-13 sec[7] | - | |
| Pulmonary venous phase | 17-24 sec[7] | - | |
| 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[10] | 160 sec |
|
| Delayed phase Sometimes called "wash out phase" or "equilibrium phase" |
6[6]-15[10] minutes | 6[6]-15[10] minutes |
|
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.[11]
References
- ↑ 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:. ISSN 0033-8419. PMID 25247563.
- ↑ Kalgi Modi, Scott C. Dulebohn (2017). Contrast-Induced Nephropathy. StatPearls Publishing. CC-BY-4.0
- ↑ Keaney, J. J.; Hannon, C. M.; Murray, P. T. (2013). "Contrast-induced acute kidney injury: how much contrast is safe? ". Nephrology Dialysis Transplantation 28 (6): 1376–1383. doi:. ISSN 0931-0509.
- ↑ Yang, Xiaoming; Hiremath, Swapnil; Akbari, Ayub; Shabana, Wael; Fergusson, Dean A.; Knoll, Greg A. (2013). "Prevention of Contrast-Induced Acute Kidney Injury: Is Simple Oral Hydration Similar To Intravenous? A Systematic Review of the Evidence ". PLoS ONE 8 (3): e60009. doi:. ISSN 1932-6203.
- ↑ Bae, Kyongtae T. (2010). "Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches ". Radiology 256 (1): 32–61. doi:. ISSN 0033-8419.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Robin Smithuis. CT contrast injection and protocols. Radiology Assistant. Retrieved on 2017-12-13.
- ↑ 7.0 7.1 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.
- ↑ 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. .
- ↑ 9.0 9.1 9.2 Otto van Delden and Robin Smithuis. Pancreas - Carcinoma. Radiology Assistant. Retrieved on 2017-12-15.
- ↑ 10.0 10.1 10.2 10.3 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
- ↑ Stephen Ledbetter and Robin Smithuis (2007-08-02). Acute Abdomen - Role of CT in Trauma. Radiopaedia.
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