I have noticed the large amount of detections in the second subject. This is because again likely due to the brightness of your image. It may help to use more bias correction in the preprocessing step or you can just adjust the quantification threshold high enough to ignore those false positives.  It isn't a huge issue. Alternatively you could manually mask out noisy or unwanted detections such as these. We recently created a module for masking out unwanted detections and requantifying. You can create masks for your subjects in something like FreeSurfer. Hopefully this helps.

Chris