Use of a radiolabelled form of 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide as a biomarker for the detection, in an individual, of PBR levels associated with normal and pathological conditions. Method for the detection of PBR levels associated with normal and pathological conditions.Diagnostic kit.本發明係關於一種以放射性標記型7-氯-N,N,5-三甲基-4-側氧基-3-苯基-3,5-二氫-4H-嗒并[4,5-b]吲哚-1-乙醯胺作為檢測個體中與正常狀態及病理狀態相關之PBR量之生物標記上之用途。本發明亦關於一種檢測與正常狀態及病理狀態相關之PBR量之方法。本發明亦關於一種診斷試劑套組。