Magnetic Particle Imaging for Real-Time Perfusion Imaging in Acute Stroke

Abstract

The fast and accurate assessment of cerebral perfusion is fundamental for the diagnosis and successful treatment of stroke patients. Magnetic particle imaging (MPI) is a new radiation-free tomographic imaging method with a superior temporal resolution, compared to other conventional imaging methods. In addition, MPI scanners can be built as prehospital mobile devices, which require less complex infrastructure than computed tomography (CT) and magnetic resonance imaging (MRI). With these advantages, MPI could accelerate the stroke diagnosis and treatment, thereby improving outcomes. Our objective was to investigate the capabilities of MPI to detect perfusion deficits in a murine model of ischemic stroke. Cerebral ischemia was induced by inserting of a microfilament in the internal carotid artery in C57BL/6 mice, thereby blocking the blood flow into the medial cerebral artery. After the injection of a contrast agent (superparamagnetic iron oxide nanoparticles) specifically tailored for MPI, cerebral perfusion and vascular anatomy were assessed by the MPI scanner within seconds. To validate and compare our MPI data, we performed perfusion imaging with a small animal MRI scanner. MPI detected the perfusion deficits in the ischemic brain, which were comparable to those with MRI but in real-time. For the first time, we showed that MPI could be used as a diagnostic tool for relevant diseases in vivo, such as an ischemic stroke. Due to its shorter image acquisition times and increased temporal resolution compared to that of MRI or CT, we expect that MPI offers the potential to improve stroke imaging and treatment.

Towards accurate modeling of the multidimensional magnetic particle imaging physics

“…In contrast to magnetic resonance imaging, the contrast in MPI is positive and the reconstructed images are quantitative. With these properties MPI is an interesting candidate for various medical applications ranging from vascular imaging [2][3][4][5] to targeted imaging [6].…”

Superparamagnetic iron oxides as MPI tracers: A primer and review of early applications

“…MPI cerebral perfusion scans have been performed in stroke [38] and traumatic brain injury [39], and has shown its utility for unambiguous detection of neuropathological changes (Figure 5). With the high temporal resolution of 40 frames per second for the FFP method, flowing blood can be observed in real-time in the heart [40] and the brain [38], and it is possible to obtain blood flow velocity measurements [41]. Notably, MPI was able to differentiate the anterior and posterior cerebral circulation via the basil artery, which was not occluded in the MCAO model where it showed an unimpaired perfusion (Figure 5A).…”

Magnetic particle imaging for radiation-free, sensitive and high-contrast vascular imaging and cell tracking

“…Alternative approaches to increasing MPI tracer circulation time include loading SPIOs into red blood cells 7,19,20 . These long-circulating tracers are crucial for applications like cancer imaging via the enhanced permeability and retention (EPR) effect 21•• , brain imaging for traumatic brain injury (TBI) and stroke via visualizing cerebral blood volume and cerebral blood flow 22••,23 , and gastrointestinal (GI) bleed imaging 24 . Each of these applications shown in Fig.…”

“…The concentration–time curves of the MPI and MRI showed similar progression and reduced wash-out of the contrast agents into the ischemic hemisphere. Reprinted with permission from 22•• . Copyright 2017 American Chemical Society.…”