Physics in medicine and biology · 2026
Minimally invasive quantification of [18F]MC225 PET using constrained simultaneous estimation of the input function.
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Providência Laura, Somsen Joost F, Van Der Weijden Chris W, Mossel Pascalle, Salvi De Souza Giordana, Dierckx Rudi A, Luurtsema Gert, Lammertsma Adriaan A, Tsoumpas Charalampos
Аннотация
OBJECTIVE: [18F]MC225 is a PET radiotracer used to assess P-glycoprotein function at the bloodbrain barrier. [18F]MC225 PET quantification requires arterial catheterization to obtain the plasma input function, an invasive procedure. The simultaneous estimation of the input function (SIME) has been proposed as a technique for estimating the plasma input function, however, it requires at least one venous/arterial blood sample. Long axial field-of-view (LAFOV) PET scanners enable a variation of the SIME algorithm, the constrained SIME (cSIME), that incorporates information from whole-blood activity, potentially eliminating the need for blood sampling. In this study, we evaluated the feasibility of cSIME for quantifying the [18F]MC225 in the brain using a clinical dataset.
APPROACH: Dynamic data from seven subjects scanned on a LAFOV PET system following injection of [18F]MC225 were included. The constrained SIME method was used to estimate the plasma input function of each subject. A whole-blood input function extracted from the ascending aorta was used as the initial estimate, and multiple brain regions were simultaneously fitted to estimate the parameters required to convert the whole-blood input function into a plasma input function. Volume of distribution (VT) values were calculated using both the ground-truth and cSIME-estimated plasma input functions with a reversible two-tissue compartment model.
MAIN RESULTS: Without a blood sample,VTestimates using the cSIME plasma input function resulted in relative differences ranging between approximately -26% and 11% compared to theVTestimates obtained with the measured plasma input function. Incorporating one blood sample as anchor at 60 minutes decrease these relative differences to 11%.
SIGNIFICANCE: The findings of this study suggest that cSIME may help reduce the invasiveness of quantitative [18F]MC225 PET studies. The clinical relevance of the observed bias will ultimately depend on its magnitude relative to disease-related differences in kinetic parameters expected in patient populations.
APPROACH: Dynamic data from seven subjects scanned on a LAFOV PET system following injection of [18F]MC225 were included. The constrained SIME method was used to estimate the plasma input function of each subject. A whole-blood input function extracted from the ascending aorta was used as the initial estimate, and multiple brain regions were simultaneously fitted to estimate the parameters required to convert the whole-blood input function into a plasma input function. Volume of distribution (VT) values were calculated using both the ground-truth and cSIME-estimated plasma input functions with a reversible two-tissue compartment model.
MAIN RESULTS: Without a blood sample,VTestimates using the cSIME plasma input function resulted in relative differences ranging between approximately -26% and 11% compared to theVTestimates obtained with the measured plasma input function. Incorporating one blood sample as anchor at 60 minutes decrease these relative differences to 11%.
SIGNIFICANCE: The findings of this study suggest that cSIME may help reduce the invasiveness of quantitative [18F]MC225 PET studies. The clinical relevance of the observed bias will ultimately depend on its magnitude relative to disease-related differences in kinetic parameters expected in patient populations.