Dr O’Hanlon qualified in 1999 from UCD and went on to complete his cardiology and general medical training in Ireland until moving to complete his Fellowship in cardiovascular magnetic resonance and structural cardiomyopathies in the Royal Brompton Hospital between 2006 and 2009. He returned to Ireland in 2009 and set up the first dedicated Cardiac MRI Centre. This service is now expanding to the Beacon Hospital.
Dr O’Hanlon and his colleague Dr Deirdre Waterhouse currently scan over 5,000 patients a year. Dr O’Hanlon has a Level 3 accreditation through the European Society of Cardiovascular imaging in Cardiovascular Magnetic Resonance and through the Society of Cardiovascular Magnetic Resonance in the USA. He continues to publish in peer review medical journals on aspects on the role of cardiovascular magnetic resonance and hypertrophic cardiomyopathy and other structural cardiomyopathies. He lectures internationally. He is also part of the Aspetar cardiovascular magnetic resonance team in Qatar providing Cardiac MRI reporting services for international athletes screened through their sports screening service.