Radiofrequency ablation of small liver malignancies under magnetic resonance guidance: progress in targeting and preliminary observations with temperature monitoring

Abstract

Objectives: To evaluate the feasibility and effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation for small liver tumours with poor conspicuity on both contrast-enhanced ultrasonography (US) and computed tomography (CT), using fast navigation and temperature monitoring. Methods: Sixteen malignant liver nodules (long-axis diameter, 0.6-2.4 cm) were treated with multipolar RF ablation on a 1.5-T wide-bore MR system in ten patients. Targeting was performed interactively, using a fast steady-state free precession sequence. Real-time MR-based temperature mapping was performed, using gradient echo-echo planar imaging (GRE-EPI) and hardware filtering. MR-specific treatment data were recorded. The mean follow-up time was 19±7 months. Results: Correct placement of RF electrodes was obtained in all procedures (image update, <500 ms; mean targeting time, 21±11 min). MR thermometry was available for 14 of 16 nodules (88%) with an accuracy of 1.6°C in a non-heated region. No correlation was found between the size of the lethal thermal dose and the ablation zone at follow-up imaging. The primary and secondary effectiveness rates were 100% and 91%, respectively. Conclusions: RF ablation of small liver tumours can be planned, targeted, monitored and controlled with MR imaging within acceptable procedure times. Temperature mapping is technically feasible, but the clinical benefit remains to be proven.

Fast PRF-based MR thermometry using double-echo EPI: in vivo comparison in a clinical hyperthermia setting

“…Also, this fast sequence can be used for realtime monitoring of fast thermal treatments, for example, high intensity focused ultrasound (HIFU) [37], radiofrequency ablation [38] and laser ablation [39]. These ablation procedures require a temporal resolution of around 1 s and a spatial resolution of around 1 × 1 × 5 mm 3 .…”

Automatic temperature control for MR-guided interstitial ultrasound ablation in liver using a percutaneous applicator: Ex vivo and in vivo initial studies

“…Different modalities of thermal ablation in liver more (LITT) (7) or less (RF) (6,12) easily combined with MR monitoring have been previously reported. In this paper, we report thermal ablation in liver with interstitial, percutaneous, US, applicator-operated, MR temperature active control.…”

“…MR thermometry, which provides near-real-time temperature maps (9)(10)(11) and enables thermal dose calculation (8) in a noninvasive manner, is considered a very promising tool for this purpose. Despite the difficulties of temperature mapping in the liver, mostly due to low T 2 * values and motion-related artifacts, PRFS-based fast temperature mapping has been shown feasible and stable in vivo, in a range of 1.6-3 C temperature uncertainty, with a temporal resolution of a few seconds and a spatial resolution of 2-3 mm (12)(13)(14).…”

In vitro artefact assessment of a new MR-compatible microwave antenna and a standard MR-compatible radiofrequency ablation electrode for tumour ablation

“…Magnetic resonance imaging (MRI) as guidance modality is less commonly used; nevertheless, it offers several advantages such as near real-time fluoroscopic imaging, free selection of imaging planes, monitoring of thermal effects, and absence of ionizing radiation [16,17]. Furthermore, the high soft tissue contrast enables tumour localisation and evaluation of the ablation zone in most cases without additional use of contrast agent [18].…”