A system adapted to record and process data from an image-guided interventional procedure in which a interventional instrument is guided by an operator by reference to an image obtained by an imaging system (1, 9a) and in which the position of the interventional instrument is tracked by a position tracking system (1, 5, 9b), comprising: an input configured to receive position data representing the track of the interventional instrument during the image-guided interventional procedure from the position tracking system (1, 5, 9b); a data store configured to record the position data; a data processor configured to process the position data to derive one or more quantitative measures of the quality of the image-guided interventional procedure; a display configured to display the one or more quantitative measures; characterised in that: the data processor is configured to derive spatial or temporal measurements of the trajectory of the interventional instrument as said one or more quantitative measures, and wherein the quantitative measures are at least one of: number of significant trajectory readjustments, number of excursions of a tip of the interventional instrument from an imaging plane of the imaging system (1, 9a), distance advanced by a tip of the interventional instrument during excursions from an imaging plane of the imaging system (1, 9a), number of incursions of a tip of the interventional instrument into an imaging plane of the imaging system (1, 9a), distance advanced through an imaging plane of the imaging system (1, 9a), number of times an imaging probe of the imaging system (1, 9a) moved, puncture time, number of punctures. an input configured to receive position data representing the track of the interventional instrument during the image-guided interventional procedure from the position tracking system (1, 5, 9b); a data store configured to record the position data; a data processor configured to process the position data to derive one or more quantitative measures of the quality of the image-guided interventional procedure; a display configured to display the one or more quantitative measures; characterised in that: the data processor is configured to derive spatial or temporal measurements of the trajectory of the interventional instrument as said one or more quantitative measures, and wherein the quantitative measures are at least one of: number of significant trajectory readjustments, number of excursions of a tip of the interventional instrument from an imaging plane of the imaging system (1, 9a), distance advanced by a tip of the interventional instrument during excursions from an imaging plane of the imaging system (1, 9a), number of incursions of a tip of the interventional instrument into an imaging plane of the imaging system (1, 9a), distance advanced through an imaging plane of the imaging system (1, 9a), number of times an imaging probe of the imaging system (1, 9a) moved, puncture time, number of punctures. number of significant trajectory readjustments, number of excursions of a tip of the interventional instrument from an imaging plane of the imaging system (1, 9a), distance advanced by a tip of the interventional instrument during excursions from an imaging plane of the imaging system (1, 9a), number of incursions of a tip of the interventional instrument into an imaging plane of the imaging system (1, 9a), distance advanced through an imaging plane of the imaging system (1, 9a), number of times an imaging probe of the imaging system (1, 9a) moved, puncture time, number of punctures.