Perspectives on imaging modalities

Abstract

In the comparison of various techniques it is important to analyze what is known about the physical possibilities of a particular technique for making a specific measurement. X-ray CT, ultrasound, and emission methods with radionuclides do not measure chemical composition. NMR can uniquely measure chemical composition. Unfortunately in the measurement of chemical composition, NMR is insensitive, thus large volumes of tissue must be selected by the NMR spectroscopic experiment for a reliable measurement. Measurements that rely on tissue physical differences to detect surfaces and motion include rapid x-ray imaging and ultrasound. For these reasons they have some attributes for particular types of studies that are superior to emission tomography and NMR. However, in the past few years, improvements in the NMR technology have led to the ability to acquire images representing only 30 sec of time in 3-dimensional studies of the beating human heart. It was believed until recently that anatomical resolution of PET was so poor that other imaging modalities would have to be used to delineate the specific region from which the PET information was coming, particularly in studies of the brain. However, in the past year it has been demonstrated that PET can acquire high resolution images of the CNS cortical ribbon at 2.5 mm or better.(ABSTRACT TRUNCATED AT 250 WORDS)