Phantoms
By definition, an imaging phantom is a specially designed object that is scanned or imaged in the field of medical imaging to measure, evaluate, analyze, or optimize the performance of various imaging modalities. However, according to this common definition, simple test plates like those used in regular quality control, could also be regarded as phantoms.
However, the actual use of phantoms in medical imaging goes far beyond simple image quality test objects. In dosimetry, mathematical phantoms provide a computational model of the human body including all relevant tissues and organs to allow Monte Carlo calculations of organ and tissue doses in a vast range of radiation qualities and geometries.
In imaging, phantoms are used and developed at different levels of sophistication. 4D anthropomorphic phantoms include also moving parts or structures simulating organ or tissue movements, like breathing. Anthropomorphic phantoms are usually custom tailored to mimic a defined class of patients, with or without defined pathologies. When imaged with the modality they are designed for, their image mimics either the image of an actual patient, or important features of a patient image. These images then can be used to test and optimize imaging parameters and procedures, compare different systems, or optimize image processing for well defined and usually challenging clinical applications.
Radiographic phantoms consist of materials that need to be well classified with regard to their interaction with the radiation used in imaging. Ideally, they exhibit similar attenuation, similar scatter properties, and ideally identical (effective) atomic number as the tissue or organ they mimic. In 3D (or even 4D) phantoms, also mass density needs to be accounted for. Our department and this group have a long history of phantom and phantom material development. Currently, 3D printing and additive manufacturing is becoming more and more important for the design and production of advanced phantoms. Therefore, we cooperate very closely with our additive manufacturing group.
Picture: Imaging phantom mimicking a prematurely born neonate for optimization of imaging parameters and comparison of different systems in pediatric radiography. Phantom printed by two different technologies (a), and x-ray images of the phantoms (b and c). From this publication
