Quantitative measurement of myocardial blood flow with oxygen-15 water and positron computed tomography: An assessment of potential and problems

An in vivo measurement technique using ¹⁵O water and positron CT for quantitation of myocardial blood flow (MBF) was investigated. A closed-chest dog model and NeuroECAT scanner were used in the study. The in vivo technique involves i.v. infusion of ¹⁵O water for a duration of 2-3 min. Oxygen-15 water radioactivity in myocardium was imaged with a NeuroECAT scanner for 10 min, starting at the time of tracer infusion. A separate scan following inhalation of ¹⁵O CO was obtained to label the blood pool and to help remove the contribution of radioactivity in the blood pool during the ¹⁵O water scans. The integrated projection technique was used for calculating MBF. The quantitative microsphere technique for measurement of MBF was performed along with the ¹⁵O water study to provide reference values, with which the MBF values by the in vivo technique were compared. Results of 12 experimental runs (in seven animals) show the in vivo technique with ¹⁵O water and positron CT can give quantitative flow images of myocardium. The in vivo positron CT measurement was found to correlates well (r = 0.93) with the in vitro values (by microspheres) over the flow range of 40 to 150 ml/min/100 g.