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Everything you need to know about Computed Tomography (CT) & CT Scanning


IV Contrast

question1. Why do we use IV contrast material?
question2. Do you use serum creatinine levels or GFR in your practice for establishing risk prior to CT scanning?
question3. What is GFR and why is it a more accurate measure than simply getting a creatinine level?
question4. Why are GFR numbers different for Caucasians and African Americans?
question5. Are all CT scans with IV contrast done the same way?
question6. What type of IV contrast material do we use and why?
question7. At what temperature do we store IV contrast material?
question8. Why do you warm IV contrast?
question9. What is the advantage of Visipaque as written in the literature?
question10. When do you use Visipaque-320 and when Omnipaque-350?
question11. Does the concentration of contrast mean that higher concentrations are better (AKA-isn’t a higher number better)?
questionThe simple answer is no. Although the answer may not seem intuitive at first glance the literature is very clear. Some of these results are included:
"Given equivalent iodine load and delivery rate the use of 300 mg I/mL contrast medium results in better contrast enhancement than the use of 370 mg I/mL contrast medium in CT of the chest. For the portal venous phase of CT of the abdomen, there was no significant difference in contrast enhancement for the two concentrations of iodine."

Intraindividual Comparison of Contrast Media Concentrations for Combined Abdominal and Thoracic MDCT
Behrendt FF et al.
AJR 2008; 191:145-150

"For the portal venous phase of CT of the abdomen, there was no significant difference in contrast enhancement for the two concentrations of iodine."

Intraindividual Comparison of Contrast Media Concentrations for Combined Abdominal and Thoracic MDCT
Behrendt FF et al.
AJR 2008; 191:145-150

Study Protocol

  • Total iodine dose (37 g) and iodine delivery rate (1.29 g/s) were identical
  • 370 mg I/ml protocol was 100 ml at 3.5 mL/sec
  • 300 mg I/ml protocol was 123 ml at 4.3 mL/sec
  • Both had saline chasers (50 ml)

"The mean contrast enhancement in the vessels and the cardiac chambers was significantly higher for the 300 mg I/mL protocol than for the 370 mg I/mL protocol at all anatomic sites in the chest except for the left ventricle."

Intraindividual Comparison of Contrast Media Concentrations for Combined Abdominal and Thoracic MDCT
Behrendt FF et al.
AJR 2008; 191:145-150

IV Contrast


 

"With respect to contrast enhancement in the abdomen, there was no statistically significant difference in mean attenuation between the 370 and 300 mg I/ml protocols."

Intraindividual Comparison of Contrast Media Concentrations for Combined Abdominal and Thoracic MDCT
Behrendt FF et al.
AJR 2008; 191:145-150

"The advantage of use of contrast media with a lower iodine concentration is the lower osmolarity and viscosity than those of higher iodine concentration contrast media. Both chemical properties, especially viscosity, of contrast media have been associated with toxic side effects, such as nephrotoxicity."

Intraindividual Comparison of Contrast Media Concentrations for Combined Abdominal and Thoracic MDCT Behrendt FF et al. AJR 2008; 191:145-150

question12. What is the volume of IV contrast material we use?
question13. What patients are considered high risk patients for IV contrast for CIN?
question14. Do we have set cutoffs for creatinine levels and if so what are they?
question15. Can we pretreat patients who have borderline renal function? If yes then how?
question16. Should patients be NPO for CT scanning? If yes for how long?
question17. What are the common volumes of contrast used for IV injection?
question18. What kind of IV access is ideal for use for IV contrast injection?
question19. Has there been any new developments in technology that may help us high injection rates in patients who can not tolerate an 18g needle (or at times even a 20g)?
question20. Can any IV the patient has in place be used to inject the contrast material?
question21. Can we use a central line or a PICC line for injection?
question22. What about the new “purple PICC/central lines” I hear about?
question23. What are some of the common normal “side effects” of IV contrast agents?
question24. Is there a relationship between patients receiving chemotherapy and CIN?
question25. Is it ok for patients to have both an MR and a CT with contrast on the same day?
question26. Have you ever seen a patient develop diffuse erythema distal to the IV injection site in the absence of extravasation?
question27. Patients often report a metallic taste in their mouth following use of IV iodinated contrast. Is there an explanation?
question28. Are there any contrast volume limitations for the use of IV contrast?
question29. Can you tell me a bit more about GFR and what it really means?

 

 

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