An Introduction to Molecular Imaging

This chapter introduces the different types of imaging modalities currently at the forefront of imaging and illustrates some basic concepts underlying these techniques. Molecular imaging aims to detect and monitor mechanistic processes in cells, tissues, or living organisms with the use of instruments and contrast mechanisms without perturbing their living system. The chapter discusses the basic principles, advantages and limitations of the imaging techniques such as positron emission tomography (PET), single photon emission computed tomography (SPECT), computed tomography (CT) or computed axial tomography (CAT) and magnetic resonance imaging (MRI). Optical imaging techniques exploit different properties of light, such as absorption, emission, reflectance, scattering, polarisation, coherence, and fluorescence, as a source of contrast. There are numerous types of fluorescence microscope systems available; however, only two of the simplest and most common microscopes, conventional and confocal, are discussed. Ultrasound (US) waves are longitudinal sound waves that oscillate back and forth.