Teaching Case

The patient, a 45 year old woman, underwent routine bi-annual mammography.

The patient underwent a routine mammographic examination. In the cranio-caudal projection, several ring like structures are seen bilaterally projecting over the breasts, mainly in the outer regions, and they appear in larger number on the left side. No such images were seen on the oblique views, thus posing the suspicion of an artifact. Clinical examination of the patient, and interrogation of the radiographer who perfomed the examination, allowed to find out the cause of this artifact. The patient's curly hair, quite long and somehow difficult to control, had fallen between the x-ray tube and the film holder, thus causing the artifact.

High-quality mammography images enhance a radiologist's ability to interpret mammograms. Artifacts (i.e., variations in mammographic density not caused by true attenuation differences) may create pseudo-lesions or mask abnormalities leading to misinterpretation. Many artifacts are readily identified, whereas others present a true diagnostic challenge. Familiarity with the numerous artifacts encountered will enable radiologists to provide accurate diagnoses. Artifacts in mammography can be classified according to the causes into four categories (references 1,2): A) patient-related (for example motion, superimposed objects or substances [jewelry, body parts, clothing, hair, implanted medical devices, foreign bodies, substances on the skin]), B) technologist-related (for example improper film handling and loading, improper use of the mammography unit and related equipment, positioning and darkroom errors), C) related to the mammographic unit (such as failure of the collimation mirror to rotate, grid inhomogeneity, failure of the reciprocating grid to move, material in the tube housing, compression failure, improper alignment of the compression paddle with the Bucky tray, defective compression paddle) and D) related to processing and the processor(such as the result of static energy, dirt or excessive developer buildup on the rollers, excessive roller pressure, damp film, scrapes and scratches, incomplete fixing, power failure, contaminated developer) . Other authors (reference 3) have arranged artifacts in the following categories: (1) particularly dangerous artifacts (because as often unseen they may affect image quality or patient radiation dose), (2) masses, (3) calcifications, (4) density variations. Evaluation of mammograms for artifacts is essential for mammographic quality assurance. Familiarity with the broad range of artifacts and the measures required to eliminate them is vital. Careful attention to darkroom cleanliness, care in film handling, regularly scheduled processor maintenance and chemical replenishment, daily quality assurance activities, and careful attention to detail during patient positioning and mammography can reduce or eliminate most mammographic artifacts. Implementation of a well-organised quality control programme will reduce the occurrence of artifacts. Recognition of artifacts in mammography is instructive and will help to improve the mammographic diagnostic quality.