A PITFALL ASSOCIATED WITH DETERMINATION OF TRANSVERSE RELAXATION-TIMES OF THE P-31 NMR SIGNALS OF ATP USING THE HAHN SPIN-ECHO

T2 measurements of P-31 NMR signals of ATP using the Hahn 90-degrees-1 80-degrees spin-echo sequence imply difficulties whenever the 180-degr ees pulse angle is not completely perfect. The reason for this finding is the crucial influence of the J-couplings of the ATP signals which result in intensity modulations and consequently in false T2 values ev en when the echo times are chosen to TE = n/J. Examinations on the cal f muscles of healthy volunteers were performed to demonstrate this eff ect and its influence on in vivo T2 determinations. The T2 relaxation times evaluated with the Hahn spin-echo in combination with a Helmholt z coil are far shorter than the true T2 values.