Interaction of Photons with Matter

Compton Scattering Angular Distribution

High-energy photons interact with matter by three main mechanisms, depending on the energy of the electromagnetic radiation. These are (i) the photoelectric effect, (ii) the Compton effect, and (iii) pair production. In addition, there are other mechanisms such as coherent (Rayleigh) scattering, an interaction between a photon and a whole atom which predominates at energies less than 50 keV triplet production and photonuclear reactions, where high energy gamma rays induce decay in the nucleus,...

Scintillation Detectors in PET

Siemens Pet Block Detector Bgo Crystal

As mentioned above, scintillation detectors are the most common and successful mode for detection of 511 keV photons in PET imaging due to their good stopping efficiency and energy resolution. These detectors consist of an appropriate choice of crystal scintil-lator coupled to a photo-detector for detection of the visible light. This process is outlined in further detail in the next two sections. Scintillation Process and Crystals Used in PET The electronic energy states of an isolated atom...

Gene Delivery Approaches Viral Methods

Gene Delivery Viral Method

Viruses are a natural delivery system for delivering their deoxyribonucleic acid DNA or ribonucleic acid RNA to the host cell. For their own survival they must deliver their DNA or RNA materials, which must be copied successfully within the host cell. Using this delivery system, vector virology has been used to construct several efficient vectors for gene therapy trials. Detailed studies of the viral genome have helped scientists to eliminate disease-causing viral genes before using their...