The pharmacokinetics behind patient-specific dosing.
How we model radiopharmaceutical behaviour at the individual level, from first principles to clinical dose report.
Targeted uptake. Measured clearance. Absorbed dose.
Targeted radiopharmaceuticals bind to receptors overexpressed on tumour cells, concentrating the radioactive payload at the lesion site while healthy tissue clears the tracer relatively quickly. The therapeutic window depends on that differential: how much dose reaches the tumour before healthy organ exposure becomes the limiting constraint.
The pharmacokinetics that govern uptake and clearance are not population averages. Receptor density, renal function, and body composition vary enough between patients that a single activity prescription will overdose some and underdose others. Absorbed dose estimation requires a model fitted to the individual.
YSOTOPE quantifies tracer uptake and clearance from each patient's imaging data, fits a two-compartment PK model, and converts the fitted parameters into absorbed dose using Monte Carlo-validated voxel dose kernels.
One model per patient. Not one model for all patients.
The two-compartment model describes how a radiopharmaceutical distributes between blood plasma (central compartment) and tumour tissue (peripheral compartment). Three rate constants govern the dynamic: k12 for transfer from blood to tissue, k21 for washout from tissue back to blood, and ke for irreversible elimination (renal clearance).
YSOTOPE fits these constants by non-linear least squares regression against the patient's serial scan time points. With three or more acquisitions over 24 to 72 hours post-injection, the model converges to clinically meaningful parameter estimates for that individual.
The fitted model then integrates the area under the time-activity curve for each organ, feeding the absorbed dose calculation in gray. Uncertainty in the parameter estimates propagates through to confidence intervals on the final dose report.
Three tumour types. One dosimetry framework.
YSOTOPE's PK modelling approach is validated across the three indication areas where targeted radionuclide therapy is most active.
PSMA-targeted Lu-177
PSMA PET quantification as the upstream input for personalised lutetium-PSMA dosing. High receptor heterogeneity between patients makes individual modelling essential.
Radioiodine dosimetry
I-124 PET-guided dosimetry for differentiated thyroid cancer radioiodine ablation. Scan-guided activity selection replaces empiric fixed-dose protocols.
Lu-177 DOTATATE
Cycle-by-cycle dosimetry from quantitative SPECT for somatostatin receptor-targeted therapy. Inter-lesion heterogeneity tracked across treatment cycles.
Collaborate on a clinical study.
Talk to our dosimetry scientists about applying the YSOTOPE PK framework to your tracer programme or clinical research question. We work with nuclear medicine departments on both prospective studies and retrospective data analysis.