title: Validation of cardiac single photon emission tomography of labeled intracoronary microspheres as a method to measure changes in distribution of coronary blood flow.
abstract: Single photon emission tomography (SPECT) combined with intracoronary dual-labelled microspheres (Tc-99m and In-111) is a technique that can potentially measure changes in regional coronary blood distribution. To validate the ability of microspheres to measure regional coronary flow distribution, we studied this method in 5 pigs to evaluate 3 specific questions: Does the lack of attenuation correction affect the calculation of relative concentrations of microspheres? Do Tc and In microspheres have similar imaging characteristics? Is there correlation between tomographic concentrations of tracer activity and tissue concentration of microspheres? Tc and In albumin microspheres were injected selectively down the left anterior descending coronary artery, and dual-isotope SPECT imaging of the whole heart was carried out. The heart was then sliced and the slices imaged directly on the collimator. Finally the slice was sectioned and well counted. The correlation coefficient (R) between SPECT profiles and direct camera profiles was 0.91. The R between In and Tc counts was also excellent at 0.93. Comparing SPECT profiles and well counting, the R was 0.79 for Tc and 0.72 for In microspheres, with the standard error of estimate less than 8.7% and 14.5% respectively about the mean value. Therefore; SPECT of intracoronary microspheres does correspond to tissue concentrations of microspheres, lack of attenuation correction does affect the correlation but not to a significant extent, In and Tc microspheres have very similar imaging characteristics. SPECT of dual intracoronary microspheres may provide a potentially useful tool to assess distribution of regional coronary blood flow.
mesh_terms: D000818:Animals; D003326:Coronary Circulation; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D007204:Indium; D008863:Microspheres; D011868:Radioisotopes; D013552:Swine; D013668:Technetium Tc 99m Aggregated Albumin; D014055:Tomography, Emission-Computed
chemical_list: D011868:Radioisotopes; D013668:Technetium Tc 99m Aggregated Albumin; D007204:Indium