Quality Control and Patient Dosimetry on line for Computed Tomography

The aim of this work is to present the functionalities and first results of an automatic system on quality control and patient dosimetry for diagnostic radiology, and its application to computed tomography (CT) in a big university hospital. The system is directly connected to the PACS (Picture Archive an Communication System) of the hospital and extracts useful information contained in the DICOM headers and Radiation Dose Structured Reports (RDSRs). The full process is automatic and was tested during the past 6 months for 11,500 procedures in three CT units. The system allows not only to extract, archive and process the parameters contained in the DICOM headers and RDSRs, but also to manage all the additional information contained in such headers for a quality control "on line". With all this information, several trigger conditions can be implemented to generate alarms and to launch corrective actions in cases such as individual dose values per examination higher than 3 times the diagnostic reference level (DRL), median values of the last 30 procedures higher than the DRL, etc. For other modalities, trigger conditions like low compression in mammography or low kV in chest images can also be used. The system allows export of data for statistical process. A personal patient dose record can be built, initially limited to the examinations performed at the hospital, but with the capability of further connection with other hospitals and outpatient centers using the same system. Mean and median Dose Length Product (DLP) values for the most common CT procedures are presented and compared with the existing references available, to decide if optimization actions are required to refine some clinical protocols. Effective doses have also been estimated from the DLP values, using the conversion factors based on the current Dose Datamed European Guidelines.