Comparing the image quality of myocardial perfusion agents in the clinicallaboratory: small test groups and large reference populations

Myocardial perfusion studies have been performed for 6 years using techneti um-99m (Tc-99(m))-sestamibi (MIBI). in this study we evaluated a newer agen t, Tc-99(m)-tetrofosmin (TF), on a trial basis for 2 weeks, and compared th e results from each week to those in an adjacent week of MIBI use. The rout ine protocol included weight-based dosing, frequent dipyridamole use, and s eparate-day rest and stress wherever possible. During: the first week, TF w as used with 'usual' image timing, i.e. stress tomography performed 30-60 m in after stress, and ancillary immediate images performed 4 min after injec tion. For the second week, 'early' tomography was performed 15-30 min after stress. TF scans (n =53) were compared with MIBI scans for the adjacent we eks (n = 54) and with a historical reference series (n = 1800). Blinded ana lysis was made of tomographic image quality, peak myocardial counts and bac kground activity (lung and abdomen) on immediate and delayed acquisitions a nd on tomographic reconstructions. The TF and MIBI test groups were similar with respect to gender, weight, stress protocol, tracer doses, imaging tim es and scintigraphic findings. Using analysis of variance, the tomographic quality scores were similar for the two observers, with stress > rest (P < 0.0001), 'usual' > 'early' (P < 0.001) and MIBI > TF (P < 0.05). Myocardial counts were approximately 20% higher with the MIBI test group than with TF at all times after stress (P = 0.001), and were similar to the reference p opulation. MIBI with usual timing gave more favourable stress abdominal bac kground ratios than the other three agent/timing combinations. Satisfactory images could be obtained with TF, but no apparent advantage over MIBI coul d be attained with earlier post-stress imaging. Subtle advantages for MIBI over TF were suggested by comparison of the small test groups. in our local imaging context, these conclusions were reinforced by a large control seri es. ((C) 2000 Lippincott Williams & Williams).