Abstract Background Myocardial metabolism and perfusion in patients with ischemic heart disease or cardiomyopathy can be simultaneously assessed using 123 I-β-methyl-iodophenyl-pentadecanoic acid (BMIPP) and 201 Thallium (Tl) dual-isotope images. However, cross-contaminated counts between these tracers complicate quantitative analyses, particularly of 123 I-BMIPP washout rates (WRs). We developed a simplified method to determine WRs corrected for energy spectral crosstalk from dual-isotope images. Methods Our correction method was based on fixed energy-spectrum spill-in ratios (iRatio for 123 I and tRatio for 201 Tl) that were empirically determined from phantom and patient datasets. These ratios were applied to separate 123 I and 201 Tl counts in 38 studies of 36 patients with ischemic heart disease using dual-energy planar and single-photon emission computed tomography (SPECT) images. We calculated WRs before and after correction using early and late anterior planar images, as well as mean tomographic counts derived from polar maps. Thresholds of 5% (planar) and 10% (SPECT) were used to assess classification agreement between corrected and uncorrected WRs. Results The range of iRatios was 0.57–0.73 and that of tRatios was 0.10–0.12. Higher iRatio values were associated with greater body-weight patients, whereas tRatios were relatively stable regardless of body weight. The corrected 123 I-BMIPP WR depends primarily on tRatio and, by formulation, is not directly affected by iRatio. Using a fixed tRatio of 0.12, the correction method revealed strong correlations between corrected and uncorrected WRs for planar imaging (R² = 0.969, p < 0.0001) and SPECT (R² = 0.964, p < 0.0001). Corrected 123 I-BMIPP WRs were comparable to uncorrected values for both planar imaging (mean difference, − 1.4%) and SPECT (mean difference, 0.8%). Among the 38 studies, classification of tentative normal versus abnormal WRs remained concordant in 35 (92%) planar studies and 36 (95%) SPECT studies. Conclusion Our simplified energy spectrum–based method demonstrated that correction of 123 I-BMIPP WRs is feasible under dual-isotope conditions. Although uncorrected WRs may provide approximate estimates, correction is important for reliable quantitative use of dual-isotope datasets, where spectral cross-talk limits accuracy. The proposed model-based approach improves the robustness and interpretability of WR assessment and enables practical, standardized quantitation.
Nakajima et al. (Sat,) studied this question.