th  - 1987 - 51st ENC Conference

MF63
NON-INVASIVE SPIN LABELING OF BLOOD BY ADIABATIC FAST PASSAGE
Thomas Dixon ~, Leila N. Du ~, and Mokhtar Gado ~
~Emory University, Department of Radiology, Atlanta,
Georgia
~Washington University, Department of Physics, St.
Louis, Missouri
~Mallinkrodt Institute of Radiology, Washington
University, St. Louis, Missouri
Excellent images of arteries can be made usinm X-rays, if
contrast is provided by injecting iodine compounds through
catheters into the arteries. Unfortunately, these injections
make the procedure more time consuming, expensive, painful and
dangerous than an NMR exam.
While NMR has long produced excellent images of brains and
even beating heartS, its use on rapidly flowing blood is in its
infancy. Our approach has been to modify the pulse sequence to
resist the problems of motion and to trigger our pulses during a
phase of the heartbeat when the blood is still.
Stationary blood can be distinguished from other stationary
tissues if it has been labeled by spin inversion before the image
is produced. Our approach is to use an adiabatic fast passage in
which neither the frequency nor the magnetic field are swept.
Instead, natural motion of arterial blood in an applied field
gradient causes the Larmor frequency of the blood to sweep past
the transmitter frequency. Stationary tissue is thus not
affected. Images of blood only are produced by subtracting an
image with fast passage from one without, just as subtraction is
used in the conventional X-ray images to eliminate interfering
bone shadows.
Images of the neck will be presented and
other problems will be discussed.
dynamic range and