Fast multiresolution data acquisition for magnetic particle imaging using adaptive feature detection

Purpose: Magnetic particle imaging is a tomographic imaging modality capable of determining the distribution of magnetic nanoparticles with high temporal resolution. The spatial resolution of magnetic particle imaging is influenced by the gradient strength of the selection field used for spatial encoding. By increasing the gradient strength, the spatial resolution is improved, but at the same time the imaging volume decreases. For a high‐resolution image of an extended field‐of‐view, a multipatch approach can be used by shifting the sampling trajectory in space. As the total imaging timescales with the number of patches, the downside of the multipatch method is the degradation of the temporal resolution. Methods: The purpose of this work was to develop a scanning procedure incorporating the advantages of imaging at multiple gradient strengths. A low‐resolution overview scan is performed at the beginning followed by a small number of high‐resolution scans at adaptively detected locations extracted from the low‐resolution scan. Results: By combining all data during image reconstruction, it is possible to obtain a large field‐of‐view image of anisotropic spatial resolution. It is measured in a fraction of time compared to a fully sampled high‐resolution field of view image. Conclusions: Magnetic particle imaging is a flexible imaging method allowing to rapidly scan small volumes. When scaling magnetic particle imaging from small animal to human applications, it will be essential to keep the acquisition time low while still capturing larger volumes at high resolution. With our proposed adaptive multigradient imaging sequence, it is possible to capture a large field of view while keeping both the temporal and the spatial resolution high.