Source-to-Target Automatic Rotating Estimation
STARE, Source-to-Target Automatic Rotating Estimation, is a MATLAB package for non-invasive estimation of the net influx rate (Ki) of irreversible Positron Emission Tomography (PET) radiotracers and currently validated for [18F]-FDG data. It adopts a novel data-driven approach that only requires individual-level dynamic PET data as input but not blood data.
STARE builds upon a source-to-target tissue model, where the tracer time activity curves (TACs) in multiple “target” regions are expressed at once as a function of a common “source” region, based on the two-tissue irreversible compartment model. The disentanglement of target regions Ki from the source region Ki is attained by fitting the source-to-target model across all target regions simultaneously assuming a common source region every time [1].
Unlike other PET tracer Ki estimation methods that rely on tracer blood data to anchor their estimates to individual subjects, STARE ensures identifiability by data-driven, subject-specific anchoring in its cost function minimization. This is attained by adding a regularization term in its cost function that penalizes the distance of the Ki estimate from the Ki derived from a bootstrapped set of partial volume-corrected image-derived input function data, as extracted from a vasculature (blood) region in the field of view (FOV) that is automatically segmented with a k-means clustering method. To avoid the need for any a priori determination of the single source region, the above steps are repeated with each of the considered target regions acting in turn as the source region at each iteration. The final Ki is estimated in each target region by averaging the estimates obtained in each source rotation [1].
According to the developers, there are plans to extend STARE to support shortened scan duration, voxel-level quantification, Python-based distributions, and to validate its performance with other radiotracers as well.
STARE has been developed and validated in Matlab R2016b.
References (open-access):
[1] Bartlett, E. A., Ogden, R. T., Mann, J. J., & Zanderigo, F. (2022). Source‐to‐Target Automatic Rotating Estimation (STARE)–A publicly‐available, blood‐free quantification approach for PET tracers with irreversible kinetics: Theoretical framework and validation for [18F] FDG. NeuroImage, 249, 118901. DOI: 10.1016/j.neuroimage.2022.118901
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