Please take a look at this study it is somewhat involved but if I am reading correctly it recognizes a tool called microdialysis (ie.Glucometer) similar to that which diabetics use to measure the level of levodopa present. You establish a clinical level for the patient at which they respond-the dopamine level for them and there ya have it. What the hell is going on here, am I wrong or would this be a godsend? PLEASE TELL ME IF I"M WRONG!!
http://www.clinchem.org/cgi/content/full/43/5/740