MPI region of interest (ROI) analysis and quantification of iron in different volumes

Abstract

MPI directly detects superparamagnetic iron oxides (SPIOs), which should enable precise, accurate and linear quantification. However, selecting a region of interest (ROI) has strong effects on MPI quantification results. Ideally, ROI selection should be simple, user-independent, and widely applicable. In this work, we describe and compare four MPI ROI selection methods and assesses their performance in vitro and in vivo. To explore the effect of ROI selection, ten ferucarbotran phantoms were imaged, each contained the same amount of iron but varied in volume. Three users tested the accuracy of the ROI methods for quantification of these samples. Lastly, quantification of ferucarbotran-labeled stem cells in vivo was demonstrated with the four ROI methods. We demonstrate that each ROI method has strengths. We conclude there is an important trade-off between ROI size and the accuracy of iron quantification, therefore the choice of ROI selection method for each study must be carefully informed.