A practical background correction method for an immediately repeated first-pass radionuclide angiography

Background: A satisfactory bolus injection is essential for a successful first-pass radionuclide angiography (FPRNA). Rescheduling the FPRNA study is usually needed due to high background interference caused by an unsatisfactory bolus injection. We developed a protocol to correct the pre-existing background activity subsequent to immediately repeating the study. Methods: Seventy-four consecutive patients who had their bone scan and FPRNA scheduled on the same day were included for analysis. The initial 51 cases constituted the “validation-only” group. In the other 23 cases, the “validation plus clearance constants” group, a 5-min dynamic acquisition was performed during the 5-min equilibrium to obtain the background clearance curve and the clearance constants. For all included 74 cases ejection fraction (EF) analysis was proceeded using the images from the first injection, second injection, and second injection with the corrected background to yield EF1, EF2, and EF2′, respectively. EF2 and EF2′ were then compared to the ejection fraction without background interference, the EF1. Results: For the LV, the mean difference between the EF1 and the uncorrected EF2 (|LVEF1-LVEF2| in mean ± SD) was 3.1 ± 2.0% and the difference between the EF1 and the corrected EF2′ (|LVEF1-LVEF2′|) was 1.6 ± 2.1%, while the mean differences for RV are 2.2 ± 1.9% and 1.8 ± 1.8%, respectively. A significant difference (p < 0.05) was observed between the uncorrected and the corrected data for both the LV and RV. Conclusion: In FPRNA, when a bolus injection is immediately readministered, both LVEF and RVEF can be underestimated. With our correction method, the results are superior to those without correction.