Blood-brain barrier permeability in rats is altered by exposure to magnetic fields associated with magnetic resonance imaging at 1.5 T.
We have previously reported that exposure of rats to low-field (0.15 T) magnetic resonance imaging (MRI) increases blood-brain barrier (BBB) permeability. However, a number of investigators have failed to observe this effect when high-field MRI (1.5 T or higher) is used. Therefore, we investigated whether or not we would observe changes using our technique at these higher fields. Adult male Sprague-Dawley rats were anaesthetised and then exposed to a 22.5 min imaging or sham procedure. Immediately following exposure, rats were injected with 1 MBq of 153Gd-DTPA intracardially and then immediately re-exposed for an additional 22.5 min. The rats were killed 1h following the second MRI exposure, at which time the brain was resected and 3 ml of venous blood collected. The ratio of radioactivity per gram of brain to radioactivity per milliliter of blood, known as the brain-blood partition coefficient, was determined and used as a measure of BBB permeability. Groups of animals had different exposures. Group 1 (n = 9) was exposed to a clinically relevant MRI procedure. Group 2 (n = 20) was exposed to the same procedure except the rf specific absorption rate (SAR) was reduced to 25% and the animals were positioned 15 cm from imager centre to increase the time-varying magnetic field from 0.4 to 2.8 T/s. For the sham exposures (n = 21), the animals were placed in the imager with the static field ramped down to zero and exposed to a sound recording simulating a MRI examination.(ABSTRACT TRUNCATED AT 250 WORDS)
Prato
F S
FS
Department of Nuclear Medicine and Magnetic Resonance, St. Joseph's Health Centre, London, Ontario, Canada.
Wills
J M
JM
Roger
J
J
Frappier
H
H
Drost
D J
DJ
Lee
T Y
TY
Shivers
R R
RR
Zabel
P
P
D000818:Animals; D001812:Blood-Brain Barrier / Q000528:radiation effects*; D002199:Capillary Permeability / Q000528:radiation effects*; D003287:Contrast Media; D004574:Electromagnetic Fields; D005682:Gadolinium; D019786:Gadolinium DTPA; D008279:Magnetic Resonance Imaging / Q000009:adverse effects; D008297:Male; D009942:Organometallic Compounds; D004369:Pentetic Acid / Q000031:analogs & derivatives; D051381:Rats; D017207:Rats, Sprague-Dawley
D003287:Contrast Media; D009942:Organometallic Compounds; D004369:Pentetic Acid; D005682:Gadolinium; D019786:Gadolinium DTPA