Artifacts in digital mammography.

In April 2005 screening with digital mammography was allowed in the Flemish part of Belgium. A rigorous physical-technical Quality Control (QC) procedure based on the European guidelines (EUREF) was then implemented. Besides quality control, there is also quality assurance (QA). Detection of artifacts is part of the QA. During the central second reading, a continuous evaluation of the image quality is done. All visible artifacts in the digital images are registered and collected. All systems participate also in a daily quality control, with a daily exposure of a phantom image which is sent to the certified quality control group. The collected artifacts were divided into 5 different categories: patient related artifacts, technologist related artifacts, mammography unit related artifacts, processing related artifacts and viewing conditions related artifacts. Patient related artifacts are comparable with film screen mammography (FSM) and are therefore not discussed. One of the main artifacts in the group of technologist related artifacts is dust in the cassette of computed radiography (CR) systems. In the group of mammography unit related artifacts a distinction is made between the artifacts of CR systems and direct radiography (DR) systems. In the CR group, the artifacts originate in the reader, whereas in the DR group they originate in the detector, which in our study was a Selenium detector. Artifacts due to failure of the Selenium detector are most frequent in this last group. Processing related artifacts are found when the reading of the processing algorithm by the system or by the PACS software made mistakes. Because there is a daily quality control of the monitors of the soft copy work stations, we didn't recognize viewing conditions related artifacts. Some of the artifacts can simulate breast lesions or can disturb the reading of the images. In order to avoid misinterpretation, recognizing artifacts and understanding their physical-technical background are of great importance in digital breast imaging.