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Purpose <p>To evaluate simplified dosimetry methods for <sup>131</sup>I-mIBG therapy that maintain agreement with reference method while reducing clinical workflow burdens, particularly beneficial for pediatric applications.</p> Methods <p>In 24 patients, we implemented a hybrid protocol combining planar whole-body scans (1, 24, 48&#xa0;h p.i.) with 24&#xa0;h SPECT/CT for whole-body and liver dosimetry. Three liver segmentation methods were compared on SPECT/CT: whole-organ manual delineation (reference), 4 mL homogeneous sphere, and 4 mL peak sphere. To estimate time-integrated activity coefficients (TIACs) we modeled biokinetics with monoexponential using: full three-time-point data (reference), reduced combinations (1–2, 1–3, 2–3), Hänscheid single-time-point method, and population-based half-lives. Statistical analysis included linear mixed-effects modeling for segmentation comparisons and Bland-Altman analysis for TIAC method validation.</p> Results <p>The median absorbed dose was 0.36 mGy/MBq for liver and 0.09 mGy/MBq for whole-body. Among simplified protocols, dual-time-point 24–48&#xa0;h imaging demonstrated the least bias, with liver absorbed doses showing − 0.02 mGy/MBq (limits of agreement: -0.08 to 0.04 mGy/MBq) and whole-body absorbed doses 0.001 mGy/MBq (limits of agreement: -0.004 to 0.005 mGy/MBq) compared to the full three-time-point reference results. Among single-time-point methods, for both liver and whole-body, the Hänscheid approach applied at 48&#xa0;h demonstrated superior performance. The 4 mL peak sphere overestimated absorbed doses by 69% versus whole-organ delineation (0.61 vs. 0.36 mGy/MBq, <i>p</i> &lt; 0.001), and homogeneous spheres underestimated by 8% (0.33 vs. 0.36 mGy/MBq, <i>p</i> = 0.046).</p> Conclusions <p>Clinically feasible <sup>131</sup>I-mIBG dosimetry can be achieved through: (1) dual 24&#xa0;h/48&#xa0;h imaging (&lt; 6% mean bias), (2) single 48&#xa0;h Hänscheid method (&lt; 6% mean bias), and (3) homogeneous sphere liver segmentation <b>(</b>&lt; 8% mean difference from reference).</p>

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Optimizing 131I-mIBG Dosimetry: Validation of Simplified Time-Point and Segmentation Approaches

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月25日

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  • Sara Kurkowska,
  • Małgorzata Poniatowska,
  • Carlos Uribe,
  • Bożena Birkenfeld,
  • Hanna Piwowarska-Bilska

摘要

Purpose

To evaluate simplified dosimetry methods for 131I-mIBG therapy that maintain agreement with reference method while reducing clinical workflow burdens, particularly beneficial for pediatric applications.

Methods

In 24 patients, we implemented a hybrid protocol combining planar whole-body scans (1, 24, 48 h p.i.) with 24 h SPECT/CT for whole-body and liver dosimetry. Three liver segmentation methods were compared on SPECT/CT: whole-organ manual delineation (reference), 4 mL homogeneous sphere, and 4 mL peak sphere. To estimate time-integrated activity coefficients (TIACs) we modeled biokinetics with monoexponential using: full three-time-point data (reference), reduced combinations (1–2, 1–3, 2–3), Hänscheid single-time-point method, and population-based half-lives. Statistical analysis included linear mixed-effects modeling for segmentation comparisons and Bland-Altman analysis for TIAC method validation.

Results

The median absorbed dose was 0.36 mGy/MBq for liver and 0.09 mGy/MBq for whole-body. Among simplified protocols, dual-time-point 24–48 h imaging demonstrated the least bias, with liver absorbed doses showing − 0.02 mGy/MBq (limits of agreement: -0.08 to 0.04 mGy/MBq) and whole-body absorbed doses 0.001 mGy/MBq (limits of agreement: -0.004 to 0.005 mGy/MBq) compared to the full three-time-point reference results. Among single-time-point methods, for both liver and whole-body, the Hänscheid approach applied at 48 h demonstrated superior performance. The 4 mL peak sphere overestimated absorbed doses by 69% versus whole-organ delineation (0.61 vs. 0.36 mGy/MBq, p < 0.001), and homogeneous spheres underestimated by 8% (0.33 vs. 0.36 mGy/MBq, p = 0.046).

Conclusions

Clinically feasible 131I-mIBG dosimetry can be achieved through: (1) dual 24 h/48 h imaging (< 6% mean bias), (2) single 48 h Hänscheid method (< 6% mean bias), and (3) homogeneous sphere liver segmentation (< 8% mean difference from reference).