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Objective <p>This study explored a hybrid curve-fitting method optimized for radiation dosimetry evaluation in total-body dynamic positron emission tomography/computed tomography (PET/CT) imaging, compared to conventional methods reliant on multi-time-point static acquisition protocols, and evaluated the radiation dosimetry results and organ biodistribution of [<sup>68</sup>Ga]Ga-NOTA-SNA002.</p> Methods <p>A total of 16 patients with solid tumors underwent a 60-min dynamic PET acquisition immediately after administration of [<sup>68</sup>Ga]Ga-NOTA-SNA002, followed by a 20-min static PET scan at about 120&#xa0;min post-injection. Volumes of interest (VOIs) were manually delineated on the CT images for subsequent radiation dosimetry estimation and biodistribution analysis. Two datasets were created to generate organ time-activity curves (TACs): (1) two PET frames reconstructed at 15<b>–</b>35&#xa0;min and 40<b>–</b>60&#xa0;min from the dynamic PET dataset, and one frame from static PET acquisition, thereby simulating a conventional multi-time-point static protocol; (2) 55 frames from the dynamic PET dataset and a frame from static PET. To calculate the time-integrated activity coefficients (TIACs) for the tracer in source organs, two methods were used: a routine method (RM) that fitted Dataset 1 by using a conventional bi-exponential curve fitting approach, and a hybrid method (HM) that fitted Dataset 2 by combining rectangular integration for the early phase of TACs with exponential fitting for the later phase. Absorbed and effective radiation doses were subsequently estimated using OLINDA/EXM version 1.1.</p> Results <p>The [<sup>68</sup>Ga]Ga-NOTA-SNA002 primarily accumulated in the urinary system, with relatively low overall uptake levels in other source organs. Analysis of tumor-to-organ standardized uptake value (SUV) ratios revealed that all ratios reached their highest values at 120&#xa0;min post-injection. The TIACs derived from the HM were consistently higher than those obtained using the RM method, while preserving a similar rank order of distribution across organs. In both methods, the kidneys, liver, and lungs exhibited the largest TIACs. The bladder wall, kidneys, and spleen received the highest absorbed doses. The total effective dosimetry calculated with RM and HM were 20.47 ± 3.08 µSv/MBq and 36.33 ± 6.18 µSv/MBq, respectively.</p> Conclusion <p>The radiation dosimetry results obtained from both the RM and the HM consistently support the safety and feasibility of total-body PET/CT imaging using [<sup>68</sup>Ga]Ga-NOTA-SNA002. Meanwhile, the HM provides theoretically more accurate results compared to the RM, and is therefore recommended for radiation dosimetry evaluation of other novel tracers.</p>

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A hybrid curve-fitting method for radiation dosimetry evaluation and simultaneous multi-organ biodistribution assessment in total-body dynamic PET/CT: application to a novel PD-L1-targeted tracer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月30日

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  • Yunze Xie,
  • Wenxin Tang,
  • Lichao Zhang,
  • Guobing Liu,
  • Hongcheng Shi

摘要

Objective

This study explored a hybrid curve-fitting method optimized for radiation dosimetry evaluation in total-body dynamic positron emission tomography/computed tomography (PET/CT) imaging, compared to conventional methods reliant on multi-time-point static acquisition protocols, and evaluated the radiation dosimetry results and organ biodistribution of [68Ga]Ga-NOTA-SNA002.

Methods

A total of 16 patients with solid tumors underwent a 60-min dynamic PET acquisition immediately after administration of [68Ga]Ga-NOTA-SNA002, followed by a 20-min static PET scan at about 120 min post-injection. Volumes of interest (VOIs) were manually delineated on the CT images for subsequent radiation dosimetry estimation and biodistribution analysis. Two datasets were created to generate organ time-activity curves (TACs): (1) two PET frames reconstructed at 15–35 min and 40–60 min from the dynamic PET dataset, and one frame from static PET acquisition, thereby simulating a conventional multi-time-point static protocol; (2) 55 frames from the dynamic PET dataset and a frame from static PET. To calculate the time-integrated activity coefficients (TIACs) for the tracer in source organs, two methods were used: a routine method (RM) that fitted Dataset 1 by using a conventional bi-exponential curve fitting approach, and a hybrid method (HM) that fitted Dataset 2 by combining rectangular integration for the early phase of TACs with exponential fitting for the later phase. Absorbed and effective radiation doses were subsequently estimated using OLINDA/EXM version 1.1.

Results

The [68Ga]Ga-NOTA-SNA002 primarily accumulated in the urinary system, with relatively low overall uptake levels in other source organs. Analysis of tumor-to-organ standardized uptake value (SUV) ratios revealed that all ratios reached their highest values at 120 min post-injection. The TIACs derived from the HM were consistently higher than those obtained using the RM method, while preserving a similar rank order of distribution across organs. In both methods, the kidneys, liver, and lungs exhibited the largest TIACs. The bladder wall, kidneys, and spleen received the highest absorbed doses. The total effective dosimetry calculated with RM and HM were 20.47 ± 3.08 µSv/MBq and 36.33 ± 6.18 µSv/MBq, respectively.

Conclusion

The radiation dosimetry results obtained from both the RM and the HM consistently support the safety and feasibility of total-body PET/CT imaging using [68Ga]Ga-NOTA-SNA002. Meanwhile, the HM provides theoretically more accurate results compared to the RM, and is therefore recommended for radiation dosimetry evaluation of other novel tracers.