PARAMETRIC IMAGING OF PATIENT PHARMACOKINETICS

This paper presents an approach to extracting patient pharmacokinetic information from a set of longitudinal scintigraphic images and repres enting the kinetic information in parametric image form. In this appro ach, three or foul-pairs of simultaneously acquired anterior and poste rior images, for internal dosimetry with iodine-131, are obtained at 2 4-h intervals. Each pair of anterior and posterior images is converted to a ''conjugate-view'' image. The sequential conjugate-view images a re then spatially registered to each other using a symmetric phase-onl y matched filter technique. With the registered images, the value at e ach pixel location, over time, is fitted to a monoexponential function . The resulting decay constant and intercept parameters are then repre sented as ''decay-constant'' and ''intercept'' images. Further analyti cal integration of the exponential function results in a ''cumulated-a ctivity'' image. Phantom studies demonstrated that the proposed method is accurate and reliable in the registration and kinetic data extract ion of the longitudinal images. Clinical application of the approach t o patients with thyroid carcinoma showed that regions of rapid uptake or clearance that would not otherwise be highlighted were easily ident ified and some regions with unexpected kinetics were observed. It is c oncluded that decay-constant, intercept, and cumulated-activity images provide a rapid and comprehensive visual assessment of patient pharma cokinetics. The technique may have a greater impact on the care of pat ients with extensive and distributed disease.