Communication Dans Un Congrès Année : 2022

Uncertainties of a 177Lu-DOTATATE dosimetric workflow based on a reduced number of SPECT/CT acquisitions​

Résumé

Purpose: Absorbed dose estimation in internal radiation therapy usually requires several SPECT/CT images after each injection that are not always possible to acquire in clinical practice. The goal of this work is to estimate, on real patient data, the uncertainties associated with three simplified dosimetric methods that use only one acquisition instead of several ones. Material and methods: Uncertainties were computed on two patient cohorts: one of thirteen patients (Lyon, France) and one of seven patients (Strasbourg, France). For the first cohort, three SPECT/CT were acquired at cycle 1 (1H, 24H and 96H/144H) and one after the other cycles at 24H. For the second cohort, three SPECT/CT were available at 6H, 24H and 7D after cycles 1 and 4. Three simplified dosimetric methods were proposed. If the organ dose-rate (ODR) is missing at 24H, it is replaced by the ODR at 24H of the next first cycle scaled to injected activities (M1). When there is only one acquisition, dose estimates were made from the patient's pharmacokinetic parameters at cycle 1 (M2) or from a population average pharmacokinetic parameters (M3). Doses obtained from these three methods were compared to the reference method based on three SPECT/CT. Doses were computed with Monte Carlo simulations and a tri-exponential fit. Percentages of dose difference (PDD) between the simplified and the reference methods were computed for kidneys, liver including tumors, spleen and three surrogates of bone marrow. Cross validation was used for M3. Results: The median of PDD of M1 was inferior to 3.3 % at 24H whatever the volume of interest (VOI) (< 1.0 % at 1H/6H and < 2.5 % at 96H/7D). For M2, medians of PDD at 24H were -3.7 % and 13.6 % for left and right kidneys, 1.6 % for liver and tumors, 1.9 % for spleen and 10.0 %, 18.6 % and 6.3 % for respectively L2 to L4, L1 to L5 and T9 to L5. Medians were lowest for delayed acquisitions as at 96H/7D. All medians PDD were inferior to 7.7% for M3 but these results are conditioned by the homogeneity of population pharmacokinetic parameters. Conclusion: Uncertainties were estimated for three simplified dosimetric workflows.Those information can allow us to choose the most adapted method according to the number of available acquisitions and patient-specific information such as pharmacokinetic parameters.

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Dates et versions

hal-04882140 , version 1 (13-01-2025)

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  • HAL Id : hal-04882140 , version 1

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Laure Vergnaud, Anne-Laure Giraudet, Aurélie Moreau, Julien Salvadori, Alessio Imperiale, et al.. Uncertainties of a 177Lu-DOTATATE dosimetric workflow based on a reduced number of SPECT/CT acquisitions​. European Congress of Medical Physics (ECMP), European Federation of organisations for medical physics, Aug 2022, Dublin, Ireland. ⟨hal-04882140⟩
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