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Diffusion into rat brain of contrast and shift reagents for magnetic resonance imaging and spectroscopy
Author(s) -
Preston Edward,
Foster David O.
Publication year - 1993
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.1940060510
Subject(s) - chemistry , reagent , blood–brain barrier , gadolinium , ischemia , nuclear magnetic resonance , parenchyma , interstitial fluid , medicine , central nervous system , pathology , physics , organic chemistry
A sensitive radiotracer technique was used to measure transfer constants (K i s) for blood to brain diffusion of the MR contrast reagent gadolinium diethylenetriaminepentaacetate (GdDTPA 2− ) and the MR shift reagent dysprosium triethylenetetraminehexaacetate (DyTTHA 3− ) across the normal and the ischemically injured blood‐brain barrier (BBB) of rats. In rats with a normal BBB mean K i s (nL/g/s) for these reagents ranged from 0.3 to 1.4 across eight brain regions and were significantly lower in each region than K i s for sucrose (1.5–3.2), a substance known to be a poor permeant of the intact BBB. K i s measured 6h after a 10min period of normothermic forebrain ischemia were increased to 4.0–6.2 (reagents) and 6.6–7.5 (sucrose) in two brain regions, striatum and hippocampus, known to be especially vulnerable to ischemic injury. Measurements of BBB permeability to DyTTHA 3− after osmotic opening of the barrier with hypertonic arabinose gave K i s of 25–30 in forebrain regions. Estimates of reagent concentrations in brain interstitial fluid 30 min after dosing the animals indicated that both an extremely high dose of DyTTHA 3− and severe disruption of the BBB would be required to shift the resonance frequency of extracellular Na + appreciably. With the moderate degrees of BBB injury produced by short‐term ischemia, a dose of GdDTPA 2− about 25 times the usual clinical dose of 0.1 mmol/kg would be required to quantify the injury by dynamic MRI.