A revised compartmental model for biokinetics and dosimetry of 2-[18F]FDG

Abstract

Background The aim was to review available biokinetic data, collect own experimental data, and propose an updated compartmental model for 2-[18F]FDG in the frame of the revision of the ICRP report on dose coefficients for radiopharmaceuticals used in diagnostic nuclear medicine. Methods The compartmental model was developed based on published biokinetic data for 2-[18F]FDG. Additional data on urinary excretion in 23 patients (11 males, 12 females) undergoing whole-body PET/CT examinations were obtained within this study. The unknown biokinetic model parameters were derived using the software SAAM II and verified with a modified version of IDAC-Iodide. Dose coefficients for reference adults were calculated with the programme IDAC-Dose 2.1. A dynamic bladder model was employed for urinary bladder dosimetry. Results The proposed model consists of following compartments: blood, heart wall, brain, liver, lungs, pancreas, spleen, kidneys, urinary bladder content and a generic pool compartment “Other”. The latter was introduced to account for 2-[18F]FDG in body organ and tissues besides the explicitly modelled ones. The model predictions showed a good agreement with experimental data. Urinary bladder wall received the highest absorbed dose coefficient of 7.5E−02 mGy/MBq under the assumption of initial urine volume of 100 ml, first voiding at 45 min p.i. and 3.75 h voiding intervals thereafter. The effective dose coefficient calculated according to the current dosimetry framework of ICRP amounted to 1.7E−02 mSv/MBq, compared to 1.9E−02 mSv/MBq in ICRP Publication 128. Conclusion A compartmental model for 2-[18F]FDG was proposed and will be used to replace the descriptive biokinetic model of ICRP Publication 128. The revised model and the provided dose coefficients are expected to improve reference dosimetry for patients administered with 2-[18F]FDG.

Joint EURADOS-EANM initiative for an advanced computational framework for the assessment of external dose rates from nuclear medicine patients

“…Also for Na 131 I, the current ICRP biokinetic model in Publication 128 [ 10 ] was used in the present work for the source regions presented in Table 1 . The compartmental model for 18 FDG which was recently developed by an ICRP task group [ 15 ] was applied. The time activity curves in the source regions indicated in Table 1 were calculated using the software SAAM II (Nanomath (LLC), Spokane, WA, USA).…”

Mathematical complexities in radionuclide metabolic modelling: a review of ordinary differential equation kinetics solvers in biokinetic modelling

“…The numerical methods of SAAM II are based on three computational integration techniques, each with its specific strengths and weaknesses, such as the Rosenbrock integrator, which makes use of the semi-implicit method, the standard forward-integration RK method mostly for non-stiff problems, and the Padé integrator based on the Padé approximation of the matrix exponential—only applicable in SAAM II when the model has constant rates, bolus or constant-infusion inputs. SAAM II also implements other statistical methods, including the objective function (Kamp et al 2023 ). This is an extended least-squares maximum likelihood function that optimizes the parameters and variance of the data with respect to the available information (Sanchez 2005 , Kamp et al 2023 ).…”

“…SAAM II also implements other statistical methods, including the objective function (Kamp et al 2023 ). This is an extended least-squares maximum likelihood function that optimizes the parameters and variance of the data with respect to the available information (Sanchez 2005 , Kamp et al 2023 ).…”

Patient-specific radiation dose for Chinese pediatric patients undergoing whole-body PET/CT examinations

“…However, reference phantoms may cause considerable uncertainty in dose estimation due to the variation in whole-body properties among individuals (Neira et al 2020). For biodistribution, the most common model is the descriptive model presented by The International Commission on Radiological Protection (ICRP, Mattsson et al 2015), which identifies specific organs where the radiopharmaceutical accumulates and decays with characteristic halftimes (Kamp et al 2023). Hay and Segall (1999) proposed a compartment model (CM) for 18 F-FDG, which considers the exchange of 18 F-FDG between compartments.…”