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: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. 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:

A prospective comparison of the multiplane probe with the biplane probe in structure visualization and Doppler examination during transesophageal echocardiography . To compare the imaging capability of the multiplane probe with that of the biplane probe , 317 consecutive patients were randomized to undergo transesophageal echocardiography with either probe . Images of 24 cardiac structures and nine Doppler signals were graded prospectively on a three-grade system . Both multiplane and biplane probes provided excellent visualization of cardiac structures and Doppler signals , but the multiplane probe was significantly superior to the biplane probe . There were no differences in the number of attempts at esophageal intubation , the amount of sedation used , and the examination time . The number of complications was similar , although all failed intubations occurred with the multiplane probe .
{"Intervention": ["biplane probe", "multiplane probe", "transesophageal echocardiography", "multiplane and biplane probes"], "Outcome": ["Doppler signals", "number of complications", "the examination time", "number of attempts at esophageal intubation", "the amount of sedation used ,", "structure visualization and Doppler examination", "imaging capability", "nine Doppler signals", "failed intubations", "excellent visualization of cardiac structures"], "Participant": []}