Therapy Monitoring of Magnetic Resonance–Guided Radiofrequency Ablation Using T1- and T2-Weighted Sequences at 1.5 T

Abstract

In examinations performed directly after the intervention, the T2-weighted images tend to underestimate the ablation zone, whereas T1-weighted images clearly better reflect the ablation zone. T1-weighted images therefore seem more adequate for repetitive monitoring of MR-guided RFA at 1.5 T.

Preclinical evaluation of an MR-compatible microwave ablation system and comparison with a standard microwave ablation system in an ex vivo bovine liver model

“…However, the latest generation of microwave ablation systems is capable of producing larger and more spherical ablation zones and microwave ablation has found its way into clinical routine [18,19]. Using MRI as a guidance modality in percutaneous ablation procedures is currently limited to a few centres specialised in MR-guided interventions, even though MR-guidance offers several advantages such as near real-time fluoroscopic sequences [11], free selection of imaging planes [12], higher sensitivity in depicting small parenchymal lesions [13], assessment of the ablation zone without application of contrast agent and absence of ionising radiation [14]. The high operating costs of dedicated MRI-scanners combined with longer durations of MR-guided interventions prevent the increased use of MRguidance in interventional oncology [20].…”

“…However, the latest generation of microwave ablation systems has overcome these problems and produces sufficiently large, spherical ablation zones without risk of accidental tissue heating [10]. Most common guidance modalities for thermo-applicator placement are computed tomography (CT) and ultrasound; however, magnetic resonance imaging (MRI) offers several advantages such as near real-time fluoroscopic sequences [11], free selection of imaging planes [12], higher sensitivity in depicting small parenchymal lesions [13], assessment of the ablation zone without application of contrast agent and absence of ionising radiation [14]. A recent pre-clinical study has addressed the MR artefact configuration of a MRcompatible prototype microwave applicator [15].…”

MRI-guided percutaneous thermoablation in combination with hepatic resection as parenchyma-sparing approach in patients with primary and secondary hepatic malignancies: single center long-term experience

“…Nevertheless, the motivation for this approach which has been conducted at our institution for over 10 years is based on the potential advantages of MRguided thermoablation. MRI-guided procedures offer high soft tissue contrast and enables an immediate assessment of the ablation process without the administration of contrast medium, as the ablation zone can be seen as a T1 hyperintense area, whereas the target tumor is typically hypointense on T1 weighted imaging [21]. In contrast, with CT as a guidance modality, both the ablation zone and the target tumor appear hypodense in unenhanced imaging making a reliable differentiation between tumor and the ablation zone difficult [25].…”

“…During thermoablation, the applicator was connected with an extended cable to the generator positioned outside the scanner room. T1-or T2-weighted sequences were used to assess the ablation result as reported in prior work [21]. In the event of an inadequate ablation zone or residual tumor tissue, additional ablation was conducted after repositioning the applicator under MR-fluoroscopy.…”

MRI-guided percutaneous thermoablation as first-line treatment of recurrent hepatic malignancies following hepatic resection: single center long-term experience

“…For thermoablation, the applicator was connected to the generator positioned outside the scanner room using an extension cable. T1-weighted sequences were used to monitor the ablation result [18]. Additional ablation with or without repositioning the applicator under MR-fluoroscopy was performed in 48 cases of inadequate ablation zone with suspicious residual tumor tissue.…”