MRI measurement of change in vascular parameters in the 9L rat cerebral tumor after dexamethasone administration.
OBJECTIVE
To demonstrate in the rat 9L cerebral tumor model that repeated MRI measurements can quantitate acute changes in the blood-brain distribution of Gadomer after dexamethasone administration.


METHODS
A total of 16 Fischer 344 rats were studied at 7T, 15 days after cerebral implantation of a 9L tumor. MRI procedures employed a T-One by Multiple Read Out Pulses (TOMROP) sequence to estimate R(1) (R(1) = 1/T(1)) at 145-second intervals before and after administration of Gadomer (Bayer), a macromolecular contrast agent (CA). Two baseline studies preceded Gadomer administration and 10 subsequent R(1) maps tracked CA concentration in blood and brain for 25 minutes. Thereafter, either dexamethasone (N = 10) or normal saline (N = 6) was administered intravenously. A total of 90 minutes later a second series of 12 TOMROP measurements of Gadomer distribution was performed. The influx constant, K(1), plasma distribution volume, v(D), backflux constant, k(b), and interstitial space, v(e), were determined, and the test-retest differences of each of four vascular parameters were calculated.


RESULTS
Dexamethasone decreased K(1) approximately 60% (P = 0.02), lowered k(b) and v(D) (P = 0.03 and P < 0.01, respectively), and marginally but insignificantly decreased v(e).


CONCLUSIONS
This noninvasive MRI technique can detect drug effects on blood-brain transfer constants of CAs within two hours of administration.
Ewing
James R
JR
Department of Neurology, Henry Ford Hospital, Detroit, Michigan 48202, USA. jre@neurnis.neuro.hfh.edu
Brown
Stephen L
SL
Nagaraja
Tavarekere N
TN
Bagher-Ebadian
Hassan
H
Paudyal
Ramesh
R
Panda
Swayamprava
S
Knight
Robert A
RA
Ding
Guangliang
G
Jiang
Quan
Q
Lu
Mei
M
Fenstermacher
Joseph D
JD
D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage* / Q000378:metabolism; D001812:Blood-Brain Barrier / Q000187:drug effects; D001932:Brain Neoplasms / Q000098:blood supply* / Q000188:drug therapy / Q000473:pathology*; D002199:Capillary Permeability / Q000187:drug effects*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D003287:Contrast Media / Q000008:administration & dosage; D003907:Dexamethasone / Q000008:administration & dosage* / Q000378:metabolism; D005682:Gadolinium / Q000008:administration & dosage; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D012680:Sensitivity and Specificity; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
D018931:Antineoplastic Agents, Hormonal; D003287:Contrast Media; C402765:gadomer 17; D012965:Sodium Chloride; D003907:Dexamethasone; D005682:Gadolinium