Some physical aspects of positron annihilation tomography: A critical review

Nuclear imaging of molecular processes in cancer

“…It is generally accepted that PET in humans offers superior resolution to SPECT, although the resolution of PET is intrinsically limited to the distance traveled by the positron before annihilation (up to several mm, depending on the positron energy) [10] and in principle, improvements in SPECT technology could reverse this superiority [11,12]. Another advantage of PET is that, because of the relatively high energy (511 KeV) and hence lower attenuation of the gamma photons, quantification is superior to that of SPECT.…”

Targeting activated macrophages to identify the vulnerable atherosclerotic plaque

“…While the physics of positron annihilation and design of PET camera favors a higher resolution than SPECT in human subjects, it actually favors a lower resolution in mice. 17 PET radiotracers emit positrons from the nucleus which travel a calculated range from *0.5 to 2 mm in tissue before annihilations (distance depending on the radionuclide). While the ''blurring'' effect of this short passage is not consequential in human imaging, it reduces the spatial resolution of micro-PET making it more difficult to detect very small targets such as atherosclerotic plaque in the aortic wall.…”

Discovered Solar Positronium

“…Radioactive isotope, pair production and fusion reac-tion are the major sources of e + . The huge applications for e + include atomic, nuclear, astrophysics experiments [1]- [5], positron emission tomography (PET) [6] [7], studies of defects, surfaces, electron momentum of materials [8] [9] and material with medicinal values [10]. With the advent of sophisticated technology scientists are capable to produce high intense pulsed positron beam, accumulation of e + and Ps, production of Ps 2 molecule, intensive studies of Ps laser cooling for the achievement of Ps Bose-Einstein Condensation (PsBEC) [11]- [15].…”

“…Short pulses of Ps atoms is suitable for laser spectroscopy of the Lyman-α -like transition in the dipositronium (Ps 2 ) molecule at a UV wavelength of 251 nm [16], as well as Ps formation and dynamics in various target materials and efficient production of Rydberg Ps (binding energy −6.8 eV which is just half of the H due to the reduced mass of Ps) atoms. A. P. Mills and co-workers succeeded to make the e + beam intensity ~10 10 to ~10 11 per cm 2 by adding Ps-forming target and a pulsed magnet and Ps-Lyman-α spectroscopy can be found elsewhere [17]. Dipositronium and Ps can be produced simultaneously on the metal surface by the highest intense slow e + beam bombardment which is significant for studying the Rydberg Ps atoms and observing the PsBEC state.…”