Detectability of early brain meningitis with magnetic resonance imaging.
OBJECTIVE
The ability of high-field (1.5 T) magnetic resonance imaging (MRI) to detect early brain meningitis was evaluated in a canine model. Contrast dose, timing postinjection, and imaging technique (specifically the use of magnetization transfer) were assessed.


METHODS
Imaging of five canines was performed at 1.5 T 24 hours after injection of Cowans staphylococcus into the cisterna magna. Two control animals also were imaged using the same protocol, with one animal receiving a cisternal injection of nutrient broth only and the other no injection. Contrast doses of 0.1, 0.3, and 0.8 mmol/kg gadoteridol (Gd HP-DO3A or Pro-Hance) were compared. Scans were performed at 2, 12, and 22 minutes after an initial injection of 0.1 mmol/kg. At each time point, paired T1-weighted scans with and without magnetization transfer (MT) were acquired. Thirty minutes after the initial injection of contrast, a supplemental dose of 0.2 mmol/kg was given (for a cumulative dose of 0.3 mmol/kg). Scans were then repeated at 2, 12, and 22 minutes after this dose was administered. A second supplemental contrast injection of 0.5 mmol/kg (for a cumulative dose of 0.8 mmol/kg) was given at 70 minutes, and immediate postinjection scans with and without MT were acquired.


RESULTS
In the animals receiving a cisternal injection of bacteria, the degree of meningeal enhancement was greatest at 0.8 mmol/kg, intermediate at 0.3 mmol/kg, and least at 0.1 mmol/kg. These conclusions were constant whether imaging was performed with or without MT. Scans in control studies did not demonstrate abnormal meningeal enhancement. High-contrast dose, MT, and acquisition of immediate postcontrast scans all resulted in statistically significant improvement. On masked film review, abnormal meningeal enhancement was noted in only 2 of 5 experimental dogs at a dose of 0.1 mmol/kg (regardless of the use of MT) compared with all animals at a dose of 0.3 mmol/kg. In 18 of 37 dogs (paired scans with and without MT), when abnormal enhancement was noted, the use of MT improved the visualization of abnormal meningeal enhancement.


CONCLUSIONS
In early brain meningitis, high-contrast dose (0.3 mmol/kg), MT, and scanning immediately after injection improve detection of abnormal meningeal enhancement, thus facilitating the diagnosis of meningitis. Of these factors, contrast dose is the most important.
Runge
V M
VM
Magnetic Resonance Imaging and Spectroscopy Center, University of Kentucky, Lexington 40536-0098, USA.
Wells
J W
JW
Williams
N M
NM
Lee
C
C
Timoney
J F
JF
Young
A B
AB
D000818:Animals; D003287:Contrast Media; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005682:Gadolinium; D006571:Heterocyclic Compounds; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008578:Meninges / Q000473:pathology; D016920:Meningitis, Bacterial / Q000175:diagnosis*; D009942:Organometallic Compounds; D013203:Staphylococcal Infections / Q000175:diagnosis*; D013205:Staphylococcal Protein A
D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D013205:Staphylococcal Protein A; C062402:gadoteridol; D005682:Gadolinium