White Paper: Interventional MRI: Current Status and Potential for Development Considering Economic Perspectives, Part 1: General Application

Abstract

ABSTR AC TBackground MRI is attractive for the guiding and monitoring of interventional procedures due to its high intrinsic soft tissue contrast and the possibility to measure physiologic parameters like flow and cardiac function.Method The current status of interventional MRI for the clinical routine was analyzed.Results The effort needed for the development of MR-safe monitoring systems and instruments initially resulted in the application of interventional MRI only for procedures that could not be performed by other means. Accordingly, biopsy of lesions in the breast, which are not detectable by other modalities, has been performed under MRI guidance for decades. Currently, biopsies of the prostate under MRI guidance are established in a similar fashion. At many sites blind biopsy has already been replaced by MR-guided biopsy or at least by the fusion of MR images with ultrasound. Cardiovascular This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.interventions are performed at several centers for ablation as a treatment for atrial fibrillation. Conclusion IntroductionMRI has an intrinsically high soft-tissue contrast and can be used to measure physiological parameters, such as blood flow (flow rate and flow volume), diffusion, temperature, and movement. Since its introduction into the clinical routine in the 1980 s, it has also been used for guiding and monitoring interventions. However, in contrast to CT and ultrasound, the use of MRI for guiding interventions requires significant technical effort. Due to the disruptive effect of the strong main magnetic field and the alternating electromagnetic fields, the monitoring of patients during an intervention by measuring ECG signals, oxygen saturation, or blood pressure requires special equipment. These monitoring systems must not interfere with the MRI scan and must be MR-safe (according to DIN EN 62 570:2010 -05). The list of requirements regarding monitoring equipment provides an indication of the development effort, with suitable monitoring equipment representing only one of the components necessary for MR-guided interventions.In addition to MRI safety, all catheters and instruments must be adapted to this modality. To ensure MRI safety, metal must be largely avoided since, depending on the length and orientation to the main magnetic field, it can heat up and consequently even result in burns. Achieving rigidity and torsion stability of catheters or guide wires without the use of metal for reinforcement represents a technical challenge. In the case of needles, breaking resistance is one of the more difficult properties to achieve for MR-safe designs. Moreover, instruments must be able to be effectively visualized without adjacent structures being superimposed by artifacts. The tip must be able to be identified and definitively differentiated from the shaft since MRI as a cross-sectional imaging method typically uses individual slices even for guiding interventions and does not use projections as in fluoroscopy...

White Paper: Interventional MRI: Current Status and Potential for Development Considering Economic Perspectives, Part 2: Liver and Other Applications in Oncology

“…The first part of this overview discussed the freehand technique in open MRI [1]. Unfortunately, these horizontally open scanners are much less available than closed MRI scanners.…”

“…Interventional MRI is already part of the clinical routine for many areas of application such as breast and prostate biopsy as described in detail in the first part of this overview [1]. Because of the ability to clearly visualize tumor borders and to image the effects achieved by tumor ablation, this method is particularly important in the treatment of oncology patients.…”

Percutaneous MR-guided interventions using an optical Moiré Phase tracking system: Initial results

“…Magnetic resonance imaging (MRI) offers unique approaches to not only diagnose but also treat cancer [ 1 – 3 ]. Compared to CT or ultrasound, MRI has superior soft tissue contrast, lacks ionizing radiation and enables complex double-oblique trajectories [ 4 ].…”

Instrument visualization using conventional and compressed sensing SEMAC for interventional MRI at 3T

“…12 Nonetheless, 3T has been explored for interventional MRI in an attempt to exploit the inherent higher MR signal, which may be used to obtain higher contrast, spatial, and temporal resolution. 1,2,13,14 An important challenge to consider, however, is that MR-conditional needles and drills produce more pronounced artifacts at 3T, which may impair the operator's ability to accurately localize the tip of the instrument, visualize nearby abnormal tissue and important surrounding structures, and accurately gauge the distance to targets. 2,15 The artifacts created by MR-conditional devices may be described as 3D signal displacements, geometric distortions, signal pile-ups, and signal voids.…”

“…Interventional magnetic resonance imaging (MRI) can successfully target anatomic structures and lesions that cannot be adequately visualized or accessed with computed tomography, ultrasonography, or fluoroscopy guidance . Differentiating attributes of interventional MRI are a high contrast resolution to visualize osseous and soft tissue abnormalities, spinal nerves, and submillimeter peripheral nerves; prospective nonorthogonal imaging; the absence of ionizing radiation; and the ability of process monitoring of thermal ablations …”