You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Synthesis and biological evaluation of (68)Ga labeled bis-DOTA-3,3'-(benzylidene)-bis-(1H-indole-2-carbohydrazide) as a PET tracer for in vivo visualization of necrosis. The aim of the present study was to develop a (68)Ga labeled bis-DOTA derivative of benzylidene-bis-indole and compare the in vivo stability and biodistribution with that of the previously reported bis-DTPA derivate for in vivo imaging of necrosis using PET. Uptake of the tracer was evaluated in a mouse model of Fas-mediated hepatic apoptosis in correlation with histochemical stainings. The novel (68)Ga labeled tracer showed an improved in vivo stability and could therefore be used for selective non-invasive imaging of necrotic cell death using PET.
{"Chemical": ["(68)Ga labeled bis-DOTA", "bis-DTPA", "(68)Ga", "3,3\u0027-(benzylidene)-bis-(1H-indole-2-carbohydrazide)", "benzylidene-bis-indole"]}