4.1 Instruments, Safety 20

How does water appear on T2 images?

Bright

Pathology is often associated with a large number of water molecules. Which weighting is best for pathology? T1? T2?

T2

How do T1 contrast agents (gadolinium) affect T1 relaxation time of what tissues? How does it appear?

shorten T1 relaxation times of enhancing tissues, appears hyperintense in T1W images

How does T2 contrast agents (superparamagnetic iron) affect relaxation times?

shorten T2 decay times of enhancing tissues, appears hypointense on T2W images

What are some reasons to use Gadolinium Based Contrast Agents (GBCA)?

evaluate primary tumors and mets, infections and inflammatory processes, vascular anatomy and pathology

What are some off label uses for GBCA?

brain perfusion, myocardial viability, MRA

GBCA are ______ in nature

paramagnetic

GBCAs are ___-________ ________ ______… they equilibrate between extracellular and intravascular spaces after IV injection

non-specific extracellular agents

TRUE OR FALSE: Diseased cells prohibit entry of GBCAs, while normal cells allow entry of GBCA

FALSE

Once GBCA enters a cell, the paramagnetic contrast agent increases the local magnetic field. Approaching protons interact with the paramagnetic agent… What happens now?

causes rapid T1 relaxation ultimately shortening the T1 relaxation times

TRUE OR FALSE: Approved GBCA does NOT cross the blood brain barrier

TRUE

Why do GBCAs cause cells to appear bright on T1W images?

GBCAs are paramagnetic

Are GBCAs considered to be positive enhancement agents or negative enhancement agents

positive enhancement agents

T1 shortening effects dominate at a standard dose. What is the standard dose of gadolinium chelate?

0.1mmol/kg

T2* shortening effects increase as gadolinium concentration rises. Why does this happen?

Accounts for the signal void that is often seen in the renal collecting systems several minutes following an injection of gadolinium contrast

What are the 8 GBCAs that are for sale in Canada? (NAME THE 5 LINEAR ONES)

Magnevist, multihance, omniscan, optimark, primovist

What are the 8 GBCAs that are for sale in Canada? Name the 3 Macrocyclic Aggents

Dotarem, prohance, gadovist

Extracellular agents are eliminated from the body via ________, with 50% of the dose eliminated within 1-2 hours (assuming normal function)

kidneys

Multihance behaves differently in that 3-5% of the injection dose is taken up by ___ ______ and eliminated by ____ _______

liver cells, biliary excretion

TRUE OR FALSE: a reaction to iodinated contrast does not imply that a person will be allergic to gadolinium contrast or vice versa

TRUE

Name some common adverse reactions to contrast agents used in MRI

coldness, warmth, pain at injection site, nausea with or without vomiting, headache, paresthesia, dizziness

A patient is scheduled for an enhanced MRI. They previously had a severe contrast reaction. The requested examination uses the same class of contrast as the one they had a reaction to. Should contrast be given?

No

What is the biggest risk factor involved for having a reaction to GBCA?

a previous allergic-like reaction to Gadolinium is the greatest risk factor for a future adverse event

What is Nephrogenic Systemic Fibrosis (NSF)?

a rare systemic disease that causes fibrosis (scarring) of the skin and other tissues

What is involved with NSF?

skin, lungs, heart, skeletal muscle

Should GBCA be warmed up prior to administration?

No, kept at room temperature (15 to 30 degrees celcius)

TRUE OR FALSE: It is okay to combine Heparin and contrast in MRI?

TRUE

TRUE OR FALSE: Extravasation and embolism are risks associated with power injection contrast

TRUE

Who has the greatest risk of being affected by extravasation?

children, elderly, hand, wrist, ankle, foot, peripheral IV left in place for hours, veins with multiple punctures, extremities that have received radiation

A patient went for an MRI and experienced extravasation. What can help relieve their pain?

cold compress

TRUE OR FALSE: Most cases of extravasation are able to resolve on their own

TRUE

What are the different methods to deliver contrast for the GI system in MRI?

oral, rectal, and IV contrast

Which type of contrast agents are used in MRI to improve visibility of the pancreatic and biliary ducts/tree during MRCP?

neutral and negative oral contrast agents

What are some neutral oral contrast agents that are considered to be Paramagnetic (contain manganese)?

pineapple juice, blueberry juice

What are some neutral oral contrast agents that are considered to be Diamagnetic?

Barium, Kaopectate

What are some neutral oral contrast agents that are considered to be superparamagnetic?

oral iron

What is the purpose of an MRCP?

used to evaluate the gallbladder, ducts of the hepatobiliary system for strictures, stones, tumors, preop and postop assessment of liver transplant

What does MRCP exploit?

the high signal intensity of static fluids in the biliary tract and pancreatic ducts

What type of contrast agents are recommended to improve the visualization of the pancreatic ducts during 2D MRCP and how do they work?

pineapple juice, prevents high signal in fluid filled bowel from overlapping/being superimposed over the high signal in the ducts

Which contrast agents have some hepatocyte excretion and end up in the biliary tree?

Multihance and Eovist

Symptoms of NSF can occur within ______ ___ _______

days to months

TRUE OR FALSE: It is possible to see NSF symptoms after years of exposure to GBCA

TRUE

Which MRI GBCAs are commonly associated with NSF?

Omniscan, Magnevist, Optimark

NSF most commonly occurs in patients:

who have received high doses of GBCA, either as a single administration or cumulatively, in multiple administrations over an extended period of time

What are the risk factors of NSF?

acute kidney injury, severe chronic kidney disease (CKD), end stage chronic kidney disease (stage 5), high doses and multiple exposures

The risk of NSF among patients exposed to standard or lower than standard doses of ______ __ GBCAs is low

group II

Group II GBCAs should only be administered if _____

they are deemed necessary by the supervising radiologist, and the lowest dose needed for diagnosis should be used as deemed necessary by the supervising radiologist

Patients receiving group I GBCAs should be considered at risk of developing NSF if any of the following conditions apply to the patient:

on dialysis (any form), severe or end stage CKD, AKI

Which contrast agent group is strongly preferred in patients that are at risk for NSF?

GBCA group II

A group I or group III agent is being considered for a patient at risk of NSF. What happens now?

the potential benefit of a GBCA enhanced MRI exam are felt to outweigh the risk of NSF with no suitable alternative

Which GBCA group (I/II/III) has been the most often associated with NSF?

group I

Patietns with acute kidney injury who have been exposed to GBCA are at risk of developing what?

NSF

Which GBCA should be avoided with a patient that has a suspected or known AKI?

group I

Name the “low risk” group II contrast agents

Prohance, multihance, dotarem, gadovist

name the “low risk” group III contrast agents

primovist

Which group I agents are absolutely contraindicated for at risk patients?

Omniscan, Optimark, Magnevist

In patients with Nephrogenic Systemic Fibrosis, does it become apparent right after an injection of GBCA, or later?

later

What is the standard dose range for GBCAs? Hint: Straight from ACR contrast media manual

0.2ml/kg

Which contrast agents have a standard dose of 0.1ml/kg?

Gadovist and Primovist

Which GBCA group is the best for patients with a compromised kidney function?

group II

ASK JENNIFER ABOUT CALCULATIONS

CANNNOT VIEW THEM ON BRIGHTSPACE OR PWOERPOINTS

KNOW WHICH CONTRAST AGENTS ARE GROUP I II III *MAY NEED TO LIST FROM A LIST

OH BOY DO THIS ONE EVENTUALLY #62

What are the ACR recommendations for patients with poor kidney function?

ADD HERE Q63 ASK JENNIFER

Know the CAR guideliens for contrast in patients with kidney disease

Q64

Macrocyclic contrast agents (Prohance, Gadovist, Dotarem) / Newer Linear Agents (Multihance, Primovist) may be administered when necessary to “at risk” patients such as:

AKI, stage 4 or 5 CKD (eGRF less than 30), dialysis, informed consent not recommended

What CAR guidelines identify contrast agents as “low risk” in group II

Prohance, multihance, Dotarem, Gadovist

Is outpatient screening for renal disease for group II and III agents recommended?

No: risk of NSF is low

What makes a patient “at risk” when receiving MRI contrast according to CAR guidelines?

patients with impaired renal function have a higher risk for gadolinium retention in the brain, gad retention has no known adverse effects, patients on dialysis should continue on dialysis. Hemodialysis should be scheduled 2-3 hours after GBCA injection

According to CAR guidelines, which GBCA should be absolutely contraindicated for group I?

Omniscan, Optimark, Magnevist

According to the CAR guidelines, should double or triple dosing GBCA be performed?

No, increase in NSF

According to the CAR guidelines, should the GBCA dose be decreased beyond the standard dosing?

No, there is insufficient evidence to suggest that this would lower the risk of NSF

A patient needs their contrast enhanced MRI repeated. When should this be performed?

Once the GBCA had sufficient time to clear from the patient’s renal system

Describe the hypothesis on why NSF can occur in patients with reduced renal function?

gadolinium ions dissociate from the chelates in GBCAs in patients with significantly reduced renal function due to the prolonged clearance times. Free gadolinium then binds with an anion such as a phosphate. A precipitate forms that gets deposited in tissues. Next there is a fibrotic reaction.

A patient that is pregnant is required to have an enhanced MRI. Should GBCAs be used?

Only when the clinical benefit outweights the unknown risk of fetal exposure

TRUE OR FALSE: Currently, no evidence exists to support adverse effects on the fetus when GBCA is used for an MRI

TRUE

A child is required for an MRI. What type of contrast group should be used?

group II

A patient is required to have an MRCP. Which two contrast agents have some hepatocyte excretion and end up in the biliary tree?

Multihance and Eovist

What sort of contrast is recommended for an MRCP?

Negative contrast agents (like pineapple juice)

A patient goes for an enhanced MRI that required GBCAs. The patient is breast feeding. Should the patient stop feeding for 24 hours after their injection or exposure to GBCA?

No, it is not required as a very small percentage of gadolinium based contrast medium is excreted into the breastmilk

You are preparing a drug that appears to be cloudy or has some sort of sediment. Should you use this drug?

No

A syringe is not labeled but is filled with a substance and is close to where the rest of the medications are normally kept. A patient requires a certain type of drug from a syringe. Should this unlabeled syringe be used?

No

What are the names of 3 Liver Specific Contrast Agents?

Multihance, Primovist, Superparamagnetic iron oxide

Name the two Hepatocyte specific liver specific contrast agents

Multihance, primovist

Name the one Kupffer Specific Contrast agent

Superparamagnetic Iron Oxide

What makes Multihance and Primovist so special as Hepatocyte specific agents?

they are gadolinium chelates that are free to distribute in vascular and extravascular spaces but also undergo (varying amounts of) hepatocellular excretion. They are “bi-phasic” or “combination” contrast media.

Hepatocellular excretion varies greatly between two hepatocyte specific agents. Provide names and a % of their excretion

Multihance 3-5%, Primovist 50%

Which provides better enhancement of a normal liver, Multihance or Primovist?

Primovist

What is the indication of Primovist (Gadoexetate disodium according co ACR contrast media slide)

intravenous use in T1 weighted MRI of the liver to detect and characterize lesions in adults with known or suspected focal liver disease

What is the recommended dose for Primovist (Gadoxetate Disodium)?

0.1ml/kg

Lesion Characterization of the liver is possible with Dynamic imaging (25, 60, 120 seconds). Hepatocyte phase 20-120 minutes post injection. Using Primovist, how are liver lesions detected and characterized?

pre contrast MR images and using images obtained during dynamic and hepatocyte phases

Using Primovist for a liver MRI, how do things appear during the dynamic imaging phases?

temporal enhancement and washout pattern of intravascular contrast is used to assess lesions

Primovist is selectively taken up by ___________ (finish the sentence)

hepatocytes, resulting in increased signal intensity in the liver

Primovist is used during a liver MRI. Lesions that have no or minimal hepatocyte function (hemangiomas, cysts, metatases, majority of hepatocellular carcinomas) appear:

darker than surrounding, functioning liver tissue

Primovist is eliminated:

50% renal and 50% hepatobilary

When are oral MR contrast agents used?

visualize and evaluate the stomach and the bowel. Sometimes used to opacify the biliary tree

Biphasic Oral Contrast Agents in MRI have low signal on T1 images and high signal on T2 images:

Water, dilute barium, methylcellulose, polyethylene glycol

What are Biphasic Oral Contrast MRI agents used to demonstrate?

inflammatory bowel disease, disease complications (fistulae), therapeutic response to treatment when used for MR enterography

What is a example of a Negative Oral Contrast agent (superparamagnetic):

pineapple juice

How does a negative oral contrast agent (superparamagnetic), example: pineapple juice, appear on T1 and T2 images?

hypointense

When should oral MR contrast agents be avoided?

immediately before bowel surgery and in cases of perforated bowel