TEST OBJECTS FOR MRI QUALITY ASSURANCE BASED ON POLYMER GELS

Radiation-sensitive polymer gels have been adapted for making test obj ects that can be used to assess the imaging characteristics of magneti c resonance imaging (MRI) systems. The polymer gels contain acrylic mo nomers within a gel matrix, and when irradiated with x rays the consti tuents polymerize to produce highly cross-linked microparticles that d ramatically affect water NMR relaxation rates where they form. The siz e of these effects depends on the radiation dose and composition of th e mixture irradiated, while the spatial pattern of relaxation time cha nges can be precisely controlled by spatial modulation of the x-ray ex posure. This permits the manufacture of complex test patterns free of susceptibility or edge effects, and overall image performance can be a ssessed by constructing contrast-detail diagrams using a singly irradi ated gel containing areas of different sizes and contrasts. Polymer ge ls are stable and a variety of different tests objects can be construc ted inexpensively. Such materials and test phantoms may find widesprea d application in diagnostic MRI quality assurance and testing programs . (C) 1997 American Association of Physicists in Medicine.