Artefact and ablation performance of an MR-conditional high-power microwave system in bovine livers: an ex vivo study

Abstract

Background We evaluated a magnetic resonance (MR)-conditional high-power microwave ablation system. Methods An exvivo 1.5-T evaluation was conducted by varying the sequence (T1-weighted volume interpolated breath-hold examination, T1w-VIBE; T1-weighted fast low-angle shot, T1w-FLASH; T2-weighted turbo spin-echo, T2w-TSE), applicator angulation to B0 (A-to-B0), slice orientation, and encoding direction. Tip location error (TLE) and artefact diameters were measured, and influence of imaging parameters was assessed with analysis of variance and post hoc testing. Twenty-four exvivo ablations were conducted in three bovine livers at 80 W and 120 W. Ablation durations were 5, 10, and 15 min. Ablation zones were compared for short-axis diameter (SAD), volume, and sphericity index (SI) with unpaired t test. Results The artefact pattern was similar for all sequences. The shaft artefact (4.4 ± 2.9 mm, mean ± standard deviation) was dependent on the sequence (p = 0.012) and the A-to-B0 (p < 0.001); the largest shaft diameter was measured with T1w-FLASH (6.3 ± 3.4 mm) and with perpendicular A-to-B0 (6.7 ± 2.4 mm). The tip artefact (1.6 ± 0.7 mm) was dependent on A-to-B0 (p = 0.001); TLE was -2.6 ± 1.0 mm. Ablation results at the maximum setting (15 min, 120 W) were SAD = 42.0 ± 1.41 mm; volume = 56.78 ± 3.08 cm3, SI = 0.68 ± 0.05. In all ablations, SI ranged 0.68–0.75 with the smallest SI at 15 min and 120 W (p = 0.048). Conclusion The system produced sufficiently large ablation zones and the artefact was appropriate for MR-guided interventions.

2450 MHz Microwave Ablation for Liver Metastases Under 3.0T Wide-bore Magnetic Resonance Guidance: a Pilot Study

“…The formation of air bubbles during ultrasound-guided ablation results in a blurred boundary. Thus, MR-guided ablation plays a very important role in the ablation of very small lesions and lesions at speci c locations 25,26 It has been reported that poor display microwave applicator tip (length, 1.6 cm) on T1WI may be related to the ceramic structure of the tip, especially for oblique non-coplanar puncture, but the depth and shape of the applicator tip can be observed better after scanning along the long axis of the microwave applicator 27 .…”

MR-Guided High-Power Microwave Ablation in Hepatic Malignancies: Initial Results in Clinical Routine

“…Nevertheless, one relevant issue regarding patient safety concerns the visualization of the microwave applicator. In our recently reported ex vivo evaluation of the appearance of the applicator’s MR artefact, the applicator shaft was clearly visible under MR guidance while the tip only showed a small artefact [ 17 ]. This observation was even stronger under clinical, non-optimal conditions, especially with MR-fluoroscopic sequences.…”

“…3D T1-weighted VIBE was repeated to confirm the correct applicator position. The previously reported impaired visibility of the applicator tip had to be considered during applicator placement and position control [ 17 ]. Ablation was conducted after connection of the microwave antenna and the generator via an MR-compatible coaxial cable with the generator placed outside the scanner room.…”

“…Ablation was conducted after connection of the microwave antenna and the generator via an MR-compatible coaxial cable with the generator placed outside the scanner room. Ablation settings were selected according to the results of initial ex vivo experiments in bovine liver with the generator power ranging from 80 to 100 W [ 17 ]. After ablation, unenhanced 3D T1-weighted VIBE was acquired for therapy monitoring without having withdrawn the microwave antenna (Fig.…”

The Role of Human U Three Protein 14a as a Predictor for Hepatocellular Carcinoma Recurrence After Microwave Ablation

“…The antenna was attached to the microwave generator (ECO-100E2, Nanjing ECO Medical Instrument Co, China). 21,22 It generated electromagnetic waves that agitate water molecules in the surrounding tissue, producing friction and heat, thus inducing cellular death by coagulative necrosis. A pre-set mode with output power of 55 to 80 W was used with duration of 5 to 15 minutes for each ablation.…”