RF‐Shielding of Laser‐Cut Venous Stents: Calculations, Simulations, and Experiments

TL;DR

This paper presents a model to calculate how laser-cut venous stents shield radiofrequency fields, which can help optimize MRI imaging of stent patency.

Contribution

A novel analytical model combining Faraday's and Biot–Savart's laws to predict RF-shielding of laser-cut stents based on geometry and orientation.

Findings

Shielding calculations for circular and rectangular loops showed deviations of less than 10% from simulations and measurements.

Stent orientation significantly affects shielding, with deviations under 14% at 1.5T and 10% at 3T.

The model can guide MRI parameter adjustments to improve stent monitoring.

Abstract

To develop an analytical model of the RF‐shielding of laser‐cut venous stents for different orientations and stent geometries.

Laser‐cut venous stents are modeled as a grid composed of circular and rectangular loops. As these loops are orthogonal they shield different components of the transmit RF field. The shielding is calculated using Faraday's induction law, taking into account the self‐inductance and mutual coupling of circular and rectangular loops, and Biot–Savart's law. The shielding of 95 stent‐mimicking models was calculated, and numerical simulations and measurements were performed at both 1.5 and 3T for validation.

The shielding of circular and rectangular loops differed by less than 3.3% and 10% between calculations, simulations, and measurements. The overall stent length had negligible impact on the shielding (< 8%). The combined shielding of both loop types showed deviations of less than 10% compared to stent models with varying cell sizes. Orienting the stents at an oblique angle other than 0° or 90° to B
0, the model‐predicted shielding values deviated by less than 14%/10% from the measured values at 1.5 T/3 T.

The model allows for the calculation of the B
1 shielding of laser‐cut venous stents depending on their geometry and orientation relative to B
0. Thus, it may help to adapt imaging parameters such as the flip angle to optimize monitoring of stent patency.

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