Analysis of [15O]CO2

Inhaled [15O]CO2 is converted to [15O]H2O in the lungs (West and Dollery, 1962) by carbonic anhydrase (CA):

This reaction is reversible, but since there is much more water in the body than carbon dioxide, practically all 15O is labelling water. The reaction rate of carbonic anhydrase is only limited by the diffusion rate of the substrates, and equilibrium is thus instant as compared to the time-resolution of PET.

Therefore [15O]CO2 can be used in quantification of blood flow with the same analysis methods that are used with [15O]H2O PET.

Notice that 11C and 15O labelled CO2 are completely different tracers.

See also:


Ackerman RH, Subramanyam R, Correia JA, Aplert NM, Taveras JM. Positron imaging of cerebral blood flow during continuous inhalation of C15O2. Stroke 1980; 11(1): 45-49. doi: 10.1161/01.str.11.1.45.

Bigler RE, Kostick JA, Gillespie JR. Compartmental analysis of the steady-state distribution of 15O2 and H215O in total body. J Nucl Med. 1981; 22: 959-965. PMID: 7299481.

Bigler RE, Sgouros G. Biological analysis and dosimetry for 15O-labeled O2, CO2, and CO gases administered continuously by inhalation. J Nucl Med. 1983; 24: 431-437. PMID: 6405020.

Frackowiak RSJ, Lenzi G-L, Jones T, Heather J-D. Quantitative measurement of regional blood flow and oxygen metabolism in man using 15O and positron emission tomography: theory, procedure, and normal values. J Comput Assist Tomogr. 1980; 4(6): 727-736. doi: 10.1097/00004728-198012000-00001.

Herscovitch P, Raichle ME. Effect of tissue heterogeneity on the measurement of cerebral blood flow with the equilibrium C15O2 inhalation technique. J Cereb Blood Flow Metab. 1983; 3: 407-415. doi: 10.1038/jcbfm.1983.66.

Jones SC, Greenberg JH, Reivich M. Error analysis for the determination of cerebral blood flow with the continuous inhalation of 15O-labeled carbon dioxide and positron tomography. J Comput Assist Tomogr. 1982; 6(1): 116-124. doi: 10.1097/00004728-198202000-00020.

Meyer E, Yamamoto YL. The requirement for constant arterial radioactivity in the C15O2 steady-state blood-flow model. J Nucl Med. 1984; 25: 455-460. PMID: 6443572.

West JB, Dollery CT. Uptake of oxygen-15-labeled CO2 compared with carbon-11-labeled CO2 in lung. J Appl Physiol. 1962; 17(1): 9-13. doi: 10.1152/jappl.1962.17.1.9.

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Updated at: 2017-09-07
Created at: 2009-04-24
Written by: Vesa Oikonen