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Similar to the hydrocephalus application, knowledge of a mass effect (compression or displacement of the brain by a pathological source) is critical in acute care because it alerts the care team to the development of significant ICP (which is life-threatening). Mass effects can arise in a wide spectrum of conditions associated with hemorrhage (e.g. traumatic brain injury, rupture of an aneurysm or vascular malformation, hemorrhagic conversion of acute stroke, and hemorrhage resulting from a postsurgical event). Other sources include alterations of CSF dynamics (e.g. obstructive and nonobstructive hydrocephalus, intracranial hypertension, CSF leaks, and other disorders of CSF flow), and cerebral edema (e.g. from demyelinating disease, cerebral infections, or cytotoxic edema due to acute stroke). Finally ICP can be induced by tumors (primary brain tumors, metastases, and extra-axial masses). The presence of ICP is frequently detected by looking for a shift in mid-line structures of the brain, ventricular effacement (one ventricle bigger than the other), or sulcal effacement (CSF spaces in sulci smaller in one hemisphere).

While CT (including portable CT) is effective at identifying a mass effect, it is less useful for answering the second most important clinical question: “Is it getting worse?” Because the mass effect and thus increasing pressure could be developing for hours post injury (e.g. in the case of a hemorrhage after trauma), a single imaging time point is insufficient. Multiple time points are desirable and would ideally be acquired with a wearable monitor. CT is still relatively cumbersome to use repeatedly in a POC setting and the ionizing radiation makes it ill-suited for anything resembling continuous monitoring. Instead, compact, single-sided “MR monitors” could fill this gap. This is a potential new role for MR technology in medicine: a real-time monitor of ventricular/CSF asymmetry to provide an early warning sign of impending herniation, particularly in patients where clinical exam is difficult (e.g. sedated patients).

In a true monitoring scenario, the patient will have the MR monitor on for hours, perhaps days, likely precluding traditional architectures where the patient goes “inside” the bore (of even a small magnet). Instead, the magnet is “worn” or simply adjacent to the head. Such a device will not provide a homogeneous field, or even allow imaging over the whole head. Instead, the clinical information must be extracted from a 3D image of only a region of brain, or perhaps a 2D or 1D image. Nonetheless, this line of instrumentation can follow the extensive development effort previously applied to single-sided MR devices for spectroscopy and materials evaluation [49,71,72], and relaxometry and diffusion measurements in oil well logging [73].