Improving the Concentration of MR Contrast in the Arteries

This project will build and validate a tool designed to optimize the use of magnetic
resonance (MR) contrast agents for contrast-enhanced magnetic resonance angiography (CE-MRA).
As with most angiography methods, contrast agents selectively highlight a patient's arteries
as compared to surrounding tissue. In CE-MRA the contrast agent is injected into an arm vein
using a programmable injector and transported by the body's circulation to the arteries of
interest, at which point a MR acquisition depicts the arteries distinctly from surrounding
soft tissue.

At present, the clinically accepted method of injecting the contrast agent is essentially the
same for every patient, and has not been systematically evaluated or optimized. For most
chest and abdominal CE-MRA studies contrast is injected over 5-15 seconds, and the resultant
concentration of contrast agent in the arteries over the duration of the MR acquisition is
not well known. What this concentration is and how it varies over time, however, has a large
impact on the quality and clarity of the resulting images. This project is designed to
optimize the concentration of contrast agent in the arteries during the MR scan by using the
predictive results of a small "test bolus" injection to tailor the actual contrast injection
for each individual patient such that concentration remains as high and as constant as
possible during the time of MR acquisition. This will be accomplished by developing
algorithms and software tools to tailor the optimal, patient-specific injection parameters.
The method will be validated in a preliminary clinical study.

We propose that we can predict what the contrast bolus will look like (i.e., its
"concentration vs. time") by first administering a small (1cc) test bolus, taking pictures as
the contrast passes through the blood vessels, and analyzing the results. Using this
information, we believe that an individually patient-tailored injection given in multiple
phases (i.e., a "multi-phasic" injection) can create constant contrast concentration (and
therefore constant signal intensity) throughout the scan, eliminating this source of image
blurring, and improving the sharpness and likely the diagnostic quality of first-pass CE-MRA.
Moreover, by tailoring the contrast to the duration of the scan, the contrast agent is used
most efficiently and not wasted outside the acquisition duration, potentially recouping any
contrast-to-noise ratio (CNR) loss. It is important to note the results of this study are
generalizable to CT Angiography (CTA) as well, where similar efficient use of the contrast
will reduce cost and excessive patient exposure to iodinated contrast. We plan to compare an
"optimized" multiphasic contrast administration to a standard single phase contrast
administration.

Inclusion Criteria:

- 18 years of age or older;

- Scheduled at University of Washington Radiology to undergo contrast-enhanced cardiac
MR.

Exclusion Criteria:

- Unable to understand the nature of the study or to consent;

- Unwilling to participate;

- Prisoner;

- Pregnant;

- Contraindications for MRI:

- Metallic or other surgical implants

- History of metal work; metal pieces in your eyes or other body parts

- pacemaker

- defibrillator

- some aneurysm clips

- some artificial heart valves

- some implanted venous access device

- some cochlear/inner ear implants

- spinal stimulator

- some intrauterine devices (IUD)

- some tattoos or permanent make-up

- transdermal patch

- severe anxiety in confined spaces (claustrophobia)

- Contraindications for contrast:

- an allergic reaction to gadolinium contrast in the past that required treatment

- severe kidney or liver disease