Visualizing electromagnetic vacuum by MRI

TL;DR

This paper demonstrates the first MRI visualization of an electromagnetic vacuum inside a bulk metal, revealing unexpected intensity patterns and surface-specific chemical shifts, which could advance noninvasive surface analysis.

Contribution

It presents the first visualization of EM vacuum inside bulk metal using MRI and introduces novel intensity pattern analysis and chemical shift imaging for metal surfaces.

Findings

Uncovered unexpected MRI intensity patterns on metal faces.

Derived formulas for intensity ratios revealing different effective voxel volumes.

Discriminated metal surface faces via chemical shift imaging.

Abstract

Based upon Maxwell's equations, it has long been established that oscillating electromagnetic (EM) fields incident upon a metal surface decay exponentially inside the conductor, leading to a virtual EM vacuum at sufficient depths. Magnetic resonance imaging (MRI) utilizes radiofrequency (r.f.) EM fields to produce images. Here we present the first visualization of an EM vacuum inside a bulk metal strip by MRI, amongst several novel findings. We uncover unexpected MRI intensity patterns arising from two orthogonal pairs of faces of a metal strip, and derive formulae for their intensity ratios, revealing differing effective elemental volumes (voxels) underneath these faces. Further, we furnish chemical shift imaging (CSI) results that discriminate different faces (surfaces) of a metal block according to their distinct nuclear magnetic resonance (NMR) chemical shifts, which holds much promise for monitoring surface chemical reactions noninvasively. Bulk metals are ubiquitous, and MRI is a premier noninvasive diagnostic tool. Combining the two, the emerging field of bulk metal MRI can be expected to grow in importance. The fundamental nature of results presented here may impactbulk metal MRI and CSI across many fields.