FLUID-ATTENUATED INVERSION-RECOVERY MR-IMAGING - IDENTIFICATION OF PROTEIN-CONCENTRATION THRESHOLDS FOR CSF HYPERINTENSITY

OBJECTIVE. Using human volunteers and phantoms emulating CSF, we analy zed the effects of varying protein concentration on the signal intensi ty of saline solution. Also, for different fluid-attenuated inversion recovery (FLAIR) sequences, we compared protein concentration threshol ds above which the signal from these solutions becomes hyperintense to that from brain parenchyma. SUBJECTS AND METHODS. Nine albumin soluti ons of varying concentrations (3.9 mg/dl to 2500 mg/dl) were imaged us ing fast FLAIR MR sequences (TR, 6000 msec; inversion time, 1730 msec; echo train length, 20) at different effective TEs (110, 150, 200, and 250 msec). The brains of five healthy volunteers were imaged using th e same sequences. Plots of signal-to-noise ratios from the different a lbumin solutions versus albumin concentration were generated and corre lated with average signal-to-noise ratios from brain parenchyma and CS F. RESULTS. We saw a gradual increase in signal-to-noise ratios from t he albumin solutions as a function of albumin concentration, As the ef fective TE increased, the point of intersection between the plots and the average signal-to-noise ratio from brain parenchyma occurred at lo wer albumin concentrations. CONCLUSION. FLAIR MR imaging is potentiall y useful to evaluate pathologic conditions that increase CSF protein c oncentration, Using phantoms and healthy volunteers, we defined a prot ein concentration threshold above which the signal from saline solutio ns becomes hyperintense to that from brain parenchyma. This threshold depends on the effective TE used in the FLAIR sequence and is 250 mg/d l for an effective TE of 110 msec, 125 mg/dl for 150 msec, 110 mg/dl f or 200 msec, and 95 mg/dl for 250 msec.