Set parameters of BRISK detector with common interface

I would like to use the BRISK detector with the [common interface](http://docs.opencv.org/2.4/modules/features2d/doc/common_interfaces_of_feature_detectors.html#featuredetector-create). Hence I create a detector with cv::Ptr detector = cv::FeatureDetector::create("BRISK"); But how can I now set the parameters such as number of octaves, FAST threshold and patternScale? I'm using OpenCV 2.4.