Organ-Dedicated Molecular Imaging Systems

Abstract

In this review, we will cover both clinical and technical aspects of the advantages and disadvantages of organ specific (dedicated) molecular imaging (MI) systems, namely positron emission tomography (PET) and single photon emission computed tomography, including gamma cameras. This review will start with the introduction to the organ-dedicated MI systems. Thereafter, we will describe the differences and their advantages/disadvantages when compared with the standard large size scanners. We will review time evolution of dedicated systems, from first attempts to current scanners, and the ones that ended in clinical use. We will review later the state of the art of these systems for different organs, namely: breast, brain, heart, and prostate. We will also present the advantages offered by these systems as a function of the special application or field, such as in surgery, therapy assistance and assessment, etc. Their technological evolution will be introduced for each organ-based imager. Some of the advantages of dedicated devices are: higher sensitivity by placing the detectors closer to the organ, improved spatial resolution, better image contrast recovery (by reducing the noise from other organs), and also lower cost. Designing a complete ring-shaped dedicated PET scanner is sometimes difficult and limited angle tomography systems are preferable as they have more flexibility in placing the detectors around the body/organ. Examples of these geometries will be presented for breast, prostate and heart imaging. Recently achievable excellent time of flight capabilities below 300-ps full width at half of the maximum reduce significantly the impact of missing angles on the reconstructed images.