Let’s Talk About Radiation: Safe Imaging at DINW
We know that hearing the word “radiation” can raise a few eyebrows—and sometimes a few…
What You Should Know About Contrast in CT and MRI Scans
At DINW, we perform imaging exams that require contrast, but most commonly CT and MRI scans. If your doctor recommends contrast for your scan, you may have questions about what it is, how it works, and whether it’s safe.
Here’s a quick guide to help you feel informed and confident before your appointment.
What Is Contrast and Why Is It Used?
Contrast agents (also called contrast dye) are substances used to enhance the visibility of specific areas in the body during imaging. They’re not permanent and are naturally eliminated through your urine.
Contrast helps radiologists:
- Detect tumors, infections, or inflammation
- Evaluate blood flow and vessels
- Identify abnormalities in the brain and spine
- Avoid the need for repeat scans
Without contrast, certain areas—like blood vessels—may appear dark or “empty,” making it harder to interpret the images accurately.
Oral vs. IV Contrast: What’s the Difference?
Depending on the type of exam, contrast can be given in two main ways:
Oral Contrast
- Used primarily in CT scans of the abdomen and pelvis
- You drink a liquid contrast agent before the scan
- Helps highlight your gastrointestinal (GI) tract
- May have a chalky or fruity taste, depending on the type
- Barium-based agents may cause temporary white-colored stools
IV (Intravenous) Contrast
- Used in both CT and MRI scans
- Injected into a vein, usually in your arm
- Highlights blood vessels, tissues, and internal organs
- May cause a brief warm sensation or metallic taste
Your care team will let you know which type of contrast you’ll receive based on your specific exam and medical history.
What to Expect With Contrast Use
During the Exam:
- You may briefly feel coolness, warmth, or a metallic taste during the injection.
After the Exam:
- No downtime (unless you received sedation)
- Drink plenty of water to help flush the contrast
- Barium may cause white stools for a day or two
Preparation Tips for Imaging With Contrast
- Follow any prep instructions (like fasting or staying hydrated)
- Arrive 30–60 minutes early, depending on your exam type (our schedulers will let you know)
- Remove all metal items (jewelry, belts, phones, etc.)
- Inform your technologist or scheduler if you:
- Are pregnant or breastfeeding
- Have kidney issues or allergies
- Have had previous reactions to contrast
- Experience claustrophobia or require sedation
Types of Contrast Used in CT and MRI
CT Contrast (Iodine-Based)
- Injected into a vein
- Highlights blood vessels, organs, and soft tissues
- May cause a brief warm sensation or metallic taste
- Occasionally causes mild side effects like nausea or itching
MRI Contrast (Gadolinium-Based)
- Also injected via IV
- Helps visualize the brain, spinal cord, joints, and tumors
- Detects smaller abnormalities than standard MRI
- Reactions are rare and typically mild
Is Contrast Safe?
In most people, contrast agents are very safe. Millions of scans are performed each year with minimal issues. Still, side effects can occasionally occur.
Common Mild Reactions:
- Warmth or flushing
- Headache or nausea
- Mild rash or itching
Rare but Serious Reactions:
- Allergic response (e.g., swelling or difficulty breathing)
- Kidney-related complications in those with severe kidney disease
- A rare condition called Nephrogenic Systemic Fibrosis (NSF) may occur in at-risk MRI patients with kidney problems
Your care team will screen for kidney function, allergies, and past reactions before your scan. If needed, we’ll adjust your exam or avoid contrast altogether.
CT vs. MRI Contrast: Which Has More Allergy Risk?
CT contrast (iodine-based) is more likely to trigger allergic-type reactions—such as hives, itching, or shortness of breath—than MRI contrast (gadolinium-based). Although serious reactions are still rare, they occur slightly more often with CT scans.
By comparison, MRI contrast has a much lower rate of allergic response, and reactions are usually mild. For those with a history of allergies or contrast reactions, your provider may recommend premedication or alternative testing to ensure safety.
Contrast and Kidney Function
Patients with impaired kidney function are evaluated carefully before receiving contrast—especially iodine or gadolinium-based types. Depending on your kidney health:
- Contrast dose may be adjusted or avoided
- A different test may be chosen
- Dialysis may be scheduled soon after the scan (if already on dialysis)
We always check kidney function before contrast exams to reduce any risk.
Who’s at Higher Risk for Reactions?
- History of contrast allergy
- Asthma or other severe allergies
- Dehydration or heart/kidney conditions
- Taking beta-blockers or NSAIDs
Note: A seafood allergy does not increase your risk of contrast reaction.
If you’ve had a previous reaction, your doctor may prescribe antihistamines before the scan.
Pregnancy & Breastfeeding Considerations
Pregnancy
- Most contrast materials are avoided during pregnancy unless absolutely necessary.
- Iodine is considered low-risk.
- Gadolinium is typically avoided due to unknown fetal risks.
Breastfeeding
- It is safe to continue breastfeeding after receiving contrast.
- If you prefer, you can pump and discard for 24 hours—this is optional and for peace of mind only.
What to Expect Before and After Contrast
Before your exam:
- You may need to fast or follow other instructions
- Complete a screening form when you arrive
- Let us know about any medical conditions, allergies, or concerns
After your exam:
- Most people resume normal activity right away
- Drink fluids to help your body flush out the contrast
- Mild discomfort (such as bruising or a metallic taste) is normal and short-lived
Final Thoughts
CT and MRI contrast agents are incredibly valuable tools that help doctors make faster, more accurate diagnoses. Whether you’re being evaluated for a tumor, vascular condition, or another health issue, contrast-enhanced imaging provides clearer answers—and peace of mind.
If you have concerns, don’t hesitate to ask questions. Our imaging team is here to ensure your experience is safe, smooth, and supportive.
📅 Need to schedule your CT or MRI with contrast?
Contact Diagnostic Imaging NW to book your appointment today! https://www.dinw.com/for-patients/scheduling/
Additional Sources:
https://www.ashospital.net/blog/why-do-i-need-contrast-for-my-mri