Introduction to Quantitative Imaging

The standard paradigm in medical imaging uses sophisticated imaging systems that take advantage of a variety of phenomena that create image contrast, and those images are subjectively interpreted by highly trained clinicians. The trend toward measurement-driven medicine motivates an effort to convert imaging systems into measurement systems which provide quantitative imaging biomarkers. The mission of the Radiological Society of North America’s Quantitative Imaging Biomarker Alliance is to improve the value and practicality of quantitative imaging biomarkers by reducing variability across devices, sites, patients, and time. The core of the effort is the adoption of the principles of metrology into image analysis methods so confidence intervals can be claimed on imaging/measurement performance. Physicists’ contribution to this effort includes developing new imaging biomarkers, creating simulations of the physical interactions of image formation (in silico phantoms), and creating methods for objectively quantifying the technical performance of the system. Examples of objectively assessed parameters that are direct substitutes for subjectively assessed parameters, as well as other parameters that are not readily extracted from standard imaging methods, will be described. Methods for assessing their performance as quantitative imaging biomarkers will be described.