MAGNETIZATION-TRANSFER AND HIGH-DOSE CONTRAST IN EARLY BRAIN INFECTION ON MAGNETIC-RESONANCE

RATIONALE AND OBJECTIVES. The authors studied the effect of contrast d ose, use of magnetization transfer (MT), and temporal delay on the,vis ualization of contrast enhancement with gadoteridol (Gd HP-DO3A) in a canine brain abscess model. METHODS. Alpha streptococcus brain abscess es were studied in five dogs at 1.5 tesla (T) 1 and 5 days after impla ntation. Scans were performed 1, 11, and 21 minutes after contrast was administered, using an initial dose of 0.1 mmol/kg. A supplemental co ntrast injection of 0.2 mmol/kg was given (for a cumulative dose of 0. 3 mmol/kg), with scans repeated at 31, 41, and 51 minutes. RESULTS. Le sion conspicuity on day 1 was greater at high-contrast doses (0.3 mmol /kg) compared with standard doses (0.1 mmol/kg), regardless of whether imaging was performed without (0.89 +/- 0.02 compared with 0.26 +/- 0 .08) or with (0.97 +/- 0.04 compared with 0.28 +/- 0.06) MT. High-dose , MT, and a delay after contrast was injected all produced a statistic ally significant improvement. On blinded review of films obtained 11 a nd 14 minutes after injection, enhancement of the lesion could not be identified with certainty in two of five dogs at a dose of 0.1 mmol/kg , regardless of whether MT was used. Enhancement was seen consistently in all lesions at 0.3 mmol/kg. On day 5, results were comparable, wit h greater absolute enhancement. CONCLUSIONS. In early brain infection, high-contrast doses (0.3 mmol/kg), MT, and a moderate delay after inj ection all improve visualization of lesion enhancement.