Errors in the spleen-blood partition coefficient for water in C15O2 steady-state PET

The aim of this study was to clarify if the value of 0.93, determined for patients with normal livers, is useful as a pathological spleen-blood partition coefficient for water when the splenic blood flow is quantified by the C15O2 steady-state method. A steady-state PET scan with continuous inhalation of C15O2 and a dynamic PET scan with a H(2)15O bolus injection were performed. From 157 patients, 392 slices were chosen as having planes that encompassed the spleen and provided regions of interest with full signal imaging. A comparison of the results of the steady-state and dynamic methods was performed. When 0.93 was adopted as the spleen-blood partition coefficient for water, an error of about 25% was seen in the splenic blood flow of patients with cirrhosis. When measuring splenic blood flow, the H(2)15O dynamic method is necessary. However, a rough estimate of splenic blood flow is possible by the C15O2 PET steady-state method, if this error is known.