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Liver perfusion measurements

I read with interest the article by Murase, Miyazaki, and Yang (An efficient method for calculating kinetic parameters in a dual-input single-compartment model. Brit J Radiol 2007;80:371–5). The authors highlight the importance of separating the two components of the dual blood supply to the liver because "contributions from each are altered in many diseases". It is a pity that they do not cite one of the most elegant and successful approaches to this problem developed for use in functional CT by my late colleague Martin Blomley (Blomley MJ, Coulden R, Dawson P, Kormano M, Donlan P, Bufkin C, et al. Liver perfusion studied with ultrafast CT. J Comput Assist Tomogr 1995;19:424–33).

The approach, in brief, involves the following procedure: time-attenuation curves are plotted for both spleen and liver parenchyma. The peak up-slope gradient of the splenic curve is determined and the time at which peak splenic enhancement is achieved is noted. It is assumed (reasonably) that portal perfusion is negligible prior to this time. The peak up-slope of the liver curve in this pre-portal phase is found and used to calculate the hepatic arterial perfusion. Dividing this early peak liver gradient by the peak splenic gradient gives a measure of the ratio of hepatic to splenic (arterial) perfusion. The arterial component of the liver curve is then removed as follows. The (baseline-subtracted) splenic curve is multiplied by the ratio of hepatic to splenic perfusion already obtained, and the result is subtracted from the liver curve to obtain the portal venous contribution. The approach assumes only that the distribution of transit times through the spleen and liver, and also the arrival times of arterial blood in the spleen and liver, are similar.

Yours etc.,

P Dawson

Departments of Imaging, UCL Hospitals, University College London, Euston Road, London NW1 2BU, UK, E-mail: peter.dawson{at}uclh.nhs.uk

Received for publication September 13, 2007. Revision received September 28, 2007. Accepted for publication October 1, 2007.

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