Designing passive MRI‐safe implantable conducting leads with electrodes

Abstract

Lead insulation and length strongly affect implanted lead safety to RF exposure during MRI. Lead designs employing impedance and reversed winding sections offer hope for the development of passive, MRI-safe, implantable conducting leads for future human use.

Role of the lead structure in MRI‐induced heating: In vitro measurements on 30 commercial pacemaker/defibrillator leads

“…The data show that each lead has its own attitude to RFinduced heating and that the information that are available in the accompanying documents of the PM is not sufficient to explain such attitude. Recent findings (21) indicate that other factors, not currently reported in the accompanying documentation (e.g., insulation thickness/ lead-to-tissue capacitance, wire wounding), affect the amount of heating. Beside the attitude of each lead to heating, it must be kept in mind that a crucial role is played by the implant positioning and the lead path (18).…”

“…Experimental in vitro measurements of the temperature increase at the lead tip of PMs/ICDs during RF exposure show widely varying results, with values ranging from negligible degrees up to more than 60 C (11,17,18,21,30,31). Most of these studies focused only on the induced heating at the lead tip, whereas the temperature increase at the ring of bipolar leads is either considered negligible or even not mentioned.…”

“…Most of the data reported in literature on the heating of implanted leads during MRI only focus on the temperature increase induced at the lead tip (11,17,18,21,32), as it has been assumed that the larger surface of the ring compared to one of the tip implies a lower density for the deposited power at the ring and a consequent lower heating. Our data on bipolar leads show that temperature increases at the ring can be comparable with or even higher than at the tip.…”

“…The structure of the leads is one of these elements. Many efforts have been made by the scientific community to understand the lead structural properties which affect the heating and to develop lead designs or strategies that could eliminate or ameliorate the hazards of MRI (19)(20)(21). However, most of these solutions are still at research level and cannot be immediately applied to commercial leads, as an accurate evaluation of their performances-besides the MRI-conditional use-is needed before they can enter the market.…”

Tracking the Position and Rotational Orientation of a Catheter Using a Transmit Array System

“…Passive techniques use contrast materials or metallic susceptibility for visualization, so there is no connection to the MR scanner [3]- [5]. A third method can be defined as wireless active visualization [6], [7], using inductively coupled radio-frequency (ICRF) coils. In this blended method, the tracking ICRF coil is coupled to a surface receive coil inductively but there is no wired connection to the MR scanner.…”