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:

Stepwise assessment tool of operative skills ( SATOS ) : validity testing on a porcine training model of open gastrectomy . BACKGROUND The aim of this prospective study was to evaluate and compare operative performance and technical improvement of surgical trainees learning open gastrectomy using an objective structured stepwise assessment tool of operative skills ( SATOS ) previously validated for open surgery . STUDY DESIGN Thirty residents in general surgery performed 2 open partial gastrectomy training events on a porcine model . Earlier instruction was provided for the critical operative steps , with additional intraoperative instruction when required . Performance was assessed by postgraduate year ( PGY ) according to operative time , technical skills using a 23-step objective structured tool , and error rate . RESULTS There were 11 PGY-3 , 11 PGY-4 , and 8 PGY-5 residents . At the initial assessment , performance significantly differentiated the 3 PGY grades according to technical skills and error rate . At the second assessment , all 3 PGY classes were still significantly differentiable by technical skills , with no difference in error rate . Comparing performances , residents improved operative time ( p < 0.001 ) , technical skills ( p < 0.001 ) , and error rate ( p = 0.019 ) over the 2 training events . CONCLUSIONS SATOS demonstrated relevant and accurate objective assessment of trainees ' operative skills and improvement for open gastrectomy in a porcine model . This tool may be useful to standardize instruction , to expose weaknesses of trainees , and to determine minimal technical standards in residency programs .
{"Intervention": ["operative skills ( SATOS )", "porcine training model", "open partial gastrectomy training events", ".", "porcine model", "stepwise assessment tool of operative skills ( SATOS )"], "Outcome": ["relevant and accurate objective assessment", "technical skills", "operative time", "operative skills and improvement", "technical skills and error rate .", "error rate", "technical skills , with no difference in error rate .", "23-step objective structured tool , and error rate .", "postgraduate year ( PGY )"], "Participant": []}