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:

• Model for [¹⁵O]H₂O
• Blood flow
• [¹¹C]CO₂

Literature

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.

Tags: Carbon dioxide, Perfusion, Radiowater

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