Validation of myocardial blood flow estimation with nitrogen-13 ammonia PET by the argon inert gas technique in humans

We simultaneously determined global myocardial blood flow (MBF) by the argo n inert gas technique and by nitrogen-13 ammonia positron emission tomograp hy (PET) to validate PET-derived MBF values in humans. A total of 19 patien ts were investigated at rest (n=19) and during adenosine-induced hyperaemia (n=16). Regional coronary artery stenoses were ruled out by angiography. T he argon inert gas method uses the difference of arterial and coronary sinu s argon concentrations during inhalation of a mixture of 75% argon and 25% oxygen to estimate global MBE. It can be considered as valid as the microsp heres technique, which, however, cannot be applied in humans. Dynamic PET w as performed after injection of 0.8 +/-0.2 GBq N-13-ammonia and MBF was cal culated applying a two-tissue compartment model. MBF values derived from th e argon method at rest and during the hyperaemic state were 1.03 +/-0.24 ml min(-1) g(-1) and 2.64 +/-1.02 ml min-(1) g-(1), respectively. MBF values derived from ammonia PET at rest and during hyperaemia were 0.95 +/-0.23 ml min(-1) g(-1) and 2.44 +/-0.81 ml min(-1) g(-1), respectively. The correla tion between the two methods was close (y=0.92x+0.14, r=0.96; P<0.0001). No indication was found for limited extraction of ammonia in the myocardium. The high concordance of global MBF values derived with argon and ammonia in dicates that the implicit correction of spillover and recovery effects, inc orporated in the model by including an effective blood volume parameter, wo rks correctly quantitatively. Our data provide the previously missing human validation of MBF measurements from N-13-ammonia PET.