COMPARISON OF THE UPTAKE OF RADIOLABELED FATTY-ACID (I-123-PARAPHENYL-PENTADECANOIC ACID) WITH TC-99M-MIBI IN PATIENTS WITH ESTABLISHED TRANSMURAL INFARCTION

Single photon emission computed tomography (SPECT) metabolic imaging o f the heart can be undertaken with I-122-labelled fatty acids, Among t hese, I-123-paraiodophenyl pentadecanoic acid (pIPPA) was used to dete ct myocardial ischaemia and to study viability, The purpose of this st udy was to compare the distribution of locally produced I-123-pIPPA (N ational Accelerator Centre, Faure) with the perfusion tracer Tc-99m-he xakis-2-methoxyisobutyl isonitrile (MIBI) in patients with established transmural infarction. Nine male patients scheduled for resting myoca rdial perfusion imaging with Tc-99m-MIBI were also studied with I-123- pIPPA, Tomographic short-axis slices of the left ventricle Fr ere used to obtain circumferential profiles for comparison. The percentage upt ake index for I-123-pIPPA was higher than that of Tc-99m-MIBI in 5 pat ients, while the opposite pattern was observed in 4 patients, The mean uptake of I-123-pIPPA (60.2% +/- 9.7%) did not differ from the 59.6% +/- 9.4% obtained for Tc-99m-MIBI. The individual variations in distri bution of the tracers are consistent with previous reports, Reduced I- 123-pIPPA uptake (less than Tc-99m-MIBI uptake) may suggest greater se nsitivity to detect residual grey zone ischaemia, Better uptake in sca r tissue implies maintained cytosolic uptake, i.e. viability. Differen t locally produced I-123-labelled fatty acids are now available to stu dy cardiac fatty acid metabolism with SPECT.