SELECT count(*) FROM participants AS T1 JOIN Participants_in_Events AS T2 ON T1.Participant_ID  =  T2.Participant_ID WHERE T1.participant_details LIKE '%Dr.%'
How many events had participants whose details had the substring 'Dr.'
[Schema (values) (types)]: | local_govt_in_alabama |  Services : service_id (text) , service_type_code (number) | Participants : participant_id (text) , participant_type_code (number) , participant_details (text) | Events : event_id (text) , service_id (number) , event_details (text) | Participants_in_Events : event_id (text) , participant_id (number);