Oxygen-18: positron emission

Hutchinson PJ, Gupta AK, Fryer TF, Al-Rawi PG, Chatfield DA, Coles JP, et al. Correlation between cerebral blood flow, substrate delivery, and metabolism in head injury a combined microdialysis and triple oxygen positron emission tomography study. J Cereb Blood Flow Metab 2002 22 735-45. 

What nuclide is produced when (a) calcium-41 undergoes electron capture (b) oxygen-15 undergoes positron emission ... 

At very high temperatures, above 3 or 4 billion k, silicon is consumed so quickly that positron emission and electron capture reactions which might modify the n/p ratio are largely short-circuited. The weak interaction does not have time to convert any appreciable fraction of protons into neutrons during the brief period of thermonuclear combustion. It follows that, starting with matter that is initially dominated by nuclei containing equal numbers of neutrons and protons, such as oxygen-16 and silicon-28, the final products must conserve Z = N, unless they move away from nuclear stability beyond calcium-40, the last stable a element. 

Buxton DB, Nienaber CA, Luxen A, Ratib O, Hansen H, Phelps ME et al. Noninvasive quantitation of regional myocardial oxygen consumption in vivo with [1-1 ICjacetate and dynamic positron emission tomography. Circulation 1989 79 134-142... 

Fluorine-18 is an artificial radionuclide, discovered in 1937. It decays with a half-life of 109.8 min for 97% by positron emission and for 3% by electron capture to the stable isotope oxygen-18. The maximum jS+-particle energy is 0.635 MeV [4],... 

Rauch, S.L., Jenike, M.A., Alpert, N.M., Baer, L., Breiter, H.C., Savage, C.R., and Fischman, A.J. (1994) Regional cerebral blood flow measured during symptom provocation in obsessive-compulsive disorder using oxygen 15-labeled carbon dioxide and positron emission tomography. Arch Gen Psychiatry 51 62-70. 

Sr was more stable in vivo but Ag was more lipophilic. These results suggest that generator-produced isotopes such as Rb-82 (T% = 75 sec) sequestered inside cryptands may be useful freely diffusible tracers for measuring blood flow by positron emission tomography. It would be more convenient to make this measurement with generator-produced isotopes than with water from cyclotron-produced oxygen-15 (Th = 122 sec). 

A) Stable oxygen has an atomic weight of about 16 amu. Oxygen-14 has too few neutrons and so will need to increase the number of neutrons. This can occur by positron emission or electron capture. Positron emission is much more likely ... 

Positron emission tomographic (PET) studies may reveal a reduced cerebral metabolic rate for oxygen utilization, while single-photon emission computed tomographic (SPECT) studies can ascertain strokes in individuals with MELAS by using a tracer, /V-isopropyl-p- 123-1 -iodoamphetamine. The tracer accumulates in the parietooccipital region, and it can delineate the extent of the lesion. SPECT studies are used to monitor the evolution of the disease. 

Positron emission—A proton turns into a neutron plus a positively charged electron known as a positron or beta-plus particle. As with electron emission there s another particle included this time a neutrino instead of an antineutrino. An isotope of fluorine decays into oxygen as follows ... 

A very good review paper pertaining to tissue imaging was written by Stephen Joffe [171]. He cites 34 published articles on topics such as oxygen measurements, but the strength of the article is in the detailed comparison of NIR with other methods like X-ray, MRI, ultrasound, positron emission, thermal emission, electrical impedance, and more. He discusses the various types of equipment used, detectors, and light sources. He also gives one of the best short descriptions of time-resolved spectroscopy seen in any review article. 

Awasthi V et al (2007) Cerebral oxygen delivery by Hposome-encapsulated hemoglobin A positron-emission tomographic evaluation in a rat model of hemorrhagic shock. J Appl Physiol 103 28-38... 

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