OVERALL ACCURACY OF TECHNETIUM-99M-MAG3 CLEARANCE MEASUREMENTS OBTAINED WITH A GAMMA-CAMERA HEART CURVE

The aim of the present study was to evaluate the accuracy of Tc-99m-MA G3 clearance measurements using a precordial gamma camera curve calibr ated by a single plasma sample. Methods: Technetium-99m-MAG3 was admin istered to ten young normal volunteers. A 60-min gamma camera acquisit ion was performed. Five different segments of the gamma camera curve w ere determined: 3 min to 20 min, 3 min to 30 min, 3 min to 40 min, 3 m in to 50 min and 3 min to 60 min. A biexponential function was fitted on each of these five different segments, which were thereafter calibr ated using eight different blood samples. These blood samples were suc cessively used for calibration at 5, 10, 15, 20, 30, 40, 50 and 60 min . The single injection, multiple plasma sample method was used as refe rence. Results: Camera clearances varied markedly based on the length of the precordial curve and on the time of the calibration sample. Dif ferent regression equations were obtained for each duration of the cam era curve, and for each blood sample timing. Correlation coefficients were >0.95 in most cases recording period of at least 50 min, however, was necessary to obtain a s.e.e. better than those obtained using a s ingle blood sample method without gamma camera curve. Conclusion: The Tc-99m-MAG3 clearance determination using a gamma camera heart curve c alibrated with a single blood sample does not necessarily improve the accuracy of the one blood sample method.