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Background <p>Myocardial metabolism and perfusion in patients with ischemic heart disease or cardiomyopathy can be simultaneously assessed using <sup>123</sup>I-β-methyl-iodophenyl-pentadecanoic acid (BMIPP) and <sup>201</sup>Thallium (Tl) dual-isotope images. However, cross-contaminated counts between these tracers complicate quantitative analyses, particularly of <sup>123</sup>I-BMIPP washout rates (WRs). We developed a simplified method to determine WRs corrected for energy spectral crosstalk from dual-isotope images.</p> Methods <p>Our correction method was based on fixed energy-spectrum spill-in ratios (iRatio for <sup>123</sup>I and tRatio for <sup>201</sup>Tl) that were empirically determined from phantom and patient datasets. These ratios were applied to separate <sup>123</sup>I and <sup>201</sup>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.</p> Results <p>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 <sup>123</sup>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, <i>p</i> &lt; 0.0001) and SPECT (R² = 0.964, <i>p</i> &lt; 0.0001). Corrected <sup>123</sup>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.</p> Conclusion <p>Our simplified energy spectrum–based method demonstrated that correction of <sup>123</sup>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.</p>

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Energy spectrum-based correction of washout rates in dual-isotope 123I-BMIPP/201Tl imaging

  • 期刊论文

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  • 发表日期：

    2026年5月30日

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  • Kenichi Nakajima,
  • Shotoku Makida,
  • Masato Okamura,
  • Masa-aki Kawashiri,
  • Takayuki Shibutani

摘要

Background

Myocardial metabolism and perfusion in patients with ischemic heart disease or cardiomyopathy can be simultaneously assessed using 123I-β-methyl-iodophenyl-pentadecanoic acid (BMIPP) and 201Thallium (Tl) dual-isotope images. However, cross-contaminated counts between these tracers complicate quantitative analyses, particularly of 123I-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 123I and tRatio for 201Tl) that were empirically determined from phantom and patient datasets. These ratios were applied to separate 123I and 201Tl 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 123I-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 123I-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 123I-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.