THE EFFECT OF CONTRAST DOSE, IMAGING TIME, AND LESION SIZE IN THE MR DETECTION OF INTRACEREBRAL METASTASIS

PURPOSE: To evaluate the effect of MR contrast dose versus delayed ima ging time on the detection of metastatic brain lesions based on lesion size. METHODS: Contrast MR examinations with gadoteridol were obtaine d in 45 patients with brain metastases. The patients were divided into two groups: 16 received cumulative standard dose (0.1 mmol/kg) and 29 received cumulative triple dose (0.3 mmol/kg). Both groups were evalu ated at two dose levels (lower dose and higher dose) with two separate injections. Each patient received an initial bolus injection of eithe r 0.05 (cumulative standard dose) or 0.1 (cumulative triple dose) mmol /kg of gadoteridol to reach the lower-dose level and underwent imaging immediately and 10 and 20 minutes later. Thirty minutes after injecti on, an additional bolus injection of 0.05 (cumulative standard dose) o r 0.2 (cumulative triple dose) mmol/kg was administered to reach the c umulative higher-dose level (cumulative standard dose, 0.1 mmol/kg; cu mulative triple dose, 0.3 mmol). Images were acquired immediately. RES ULTS: There was no difference in the detection rate for lesions larger than 10 mm among T2-weighted, lower-dose immediate and delayed, or im mediate higher-dose images in both study groups. Lesions smaller than 10 mm had improved detection with delayed imaging in both study groups ; however, the immediate higher-dose studies still had the highest det ection rate. CONCLUSION: In the evaluation of small central nervous sy stem metastases, either delayed imaging after the injection of standar d contrast dose or higher contrast dose may improve their detection, a nd therefore affect clinical management. Higher contrast dose (cumulat ive triple dose) studies appear to be more effective than delayed imag ing with standard dose.