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

Hoffmann, Rüdiger; Keßler, David-Emanuel; Weiß, Jakob; Clasen, Stephan; Pereira, Philippe L.; Nikolaou, Konstantin; Rempp, Hansjörg

doi:10.1080/02656736.2017.1284349

Cited by 5 publications

(4 citation statements)

References 34 publications

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“…In our study, the SI ranged from 0.68 to 0.75. This value is similar to those reported for high-power MWA systems for conventional guidance techniques and higher than the SI value for a non-perfusion cooled MR-conditional system which has been reported to range from 0.36 to 0.59 [31].…”

Section: Discussionsupporting

confidence: 86%

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

Grimm¹,

Winkelmann²,

Weiß³

et al. 2019

Eur Radiol Exp

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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.

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Section: Discussionsupporting

confidence: 86%

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

Grimm¹,

Winkelmann²,

Weiß³

et al. 2019

Eur Radiol Exp

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“…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 specific locations 26 , 27 . It has been reported that poor display of the microwave applicator tip (length, 1.6 cm) on T1WI may be related to the ceramic structure of the tip, especially for oblique noncoplanar puncture, but the depth and shape of the applicator tip can be observed better after scanning along the long axis of the microwave applicator 28 .…”

Section: Discussionmentioning

confidence: 99%

2450-MHz microwave ablation of liver metastases under 3.0 T wide-bore magnetic resonance guidance: a pilot study

Liu

et al. 2022

Sci Rep

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To investigate the feasibility and effectiveness of 3.0 T wide-bore magnetic resonance (MR)-guided microwave ablation (MA) of liver metastases (LM). From October 2018 to May 2020, 39 patients with 63 LM were treated with 3.0 T wide-bore MR-guided 2450-MHz MA therapy. The procedure parameters, technical success, complications, biochemical index changes, local tumor response, local tumor progression (LTP), 12-month disease-free survival (DFS) and 12-month overall survival (OS) were recorded and analyzed. The mean tumor maximum diameter and total procedure time were 3.0 cm and 55.2 min, respectively. Technical success was 100%, but 5 cases (12.8%) had grade-1 complications. Alanine transaminase, aspartate transaminase and total bilirubin showed a slight transient increase on day 3 (P < 0.05) and returned to normal by day 30 (P > 0.05). The complete ablation rates for ≤ 2.5 and > 2.5 cm lesions were 100% and 92.5%, respectively. During the median follow-up of 12.0 months, the LTP rate was 4.8% (3/63), and the 12-month DFS and OS rates were 61.3% and 92.2%, respectively. 3.0 T wide-bore MR-guided MA for LM is a safe and effective approach, especially for small LM.

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“…Integrating microwave ablation systems with MRI may be challenging due to the need to design the ablation applicators and feeding cables from MRI-conditional materials, as well as considerable attenuation in long feeding cables due to the requirement that the microwave power source is placed outside the scanner room. 31 Some prior studies have investigated the use of 1.5 T MRI thermometry for monitoring microwave heating of ex vivo tissues such as brain, muscle, liver, kidney, in vivo rabbit brain, as well as ablation of prostate cancer in humans. [32][33][34] In these studies, MR thermometry images were acquired with different imaging sequences such as spoiled gradient-recalled echo (SPGR) and fast-SPGR in a single plane with an update time of~13-26 s. Prior studies have also employed gradient eco sequences (GRE) with Z-shimming for minimizing artifacts in the proximity of metallic microwave ablation applicator.…”

Section: Introductionmentioning

confidence: 99%

“…While MR thermometry has been widely applied for monitoring and guiding delivery of ultrasound and laser ablation, 26–30 it has not been widely used with microwave ablation systems. Integrating microwave ablation systems with MRI may be challenging due to the need to design the ablation applicators and feeding cables from MRI‐conditional materials, as well as considerable attenuation in long feeding cables due to the requirement that the microwave power source is placed outside the scanner room 31 . Some prior studies have investigated the use of 1.5 T MRI thermometry for monitoring microwave heating of ex vivo tissues such as brain, muscle, liver, kidney, in vivo rabbit brain, as well as ablation of prostate cancer in humans 32–34 .…”

Section: Introductionmentioning

confidence: 99%

Experimental assessment of microwave ablation computational modeling with MR thermometry

et al. 2020

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Computational models are widely used during the design and characterization of microwave ablation (MWA) devices, and have been proposed for pretreatment planning. Our objective was to assess three-dimensional (3D) transient temperature and ablation profiles predicted by MWA computational models with temperature profiles measured experimentally using magnetic resonance (MR) thermometry in ex vivo bovine liver. Materials and methods: We performed MWA in ex vivo tissue under MR guidance using a custom, 2.45 GHz water-cooled applicator. MR thermometry data were acquired for 2 min prior to heating, during 5-10 min microwave exposures, and for 3 min following heating. Fiber-optic temperature sensors were used to validate the accuracy of MR temperature measurements. A total of 13 ablation experiments were conducted using 30-50 W applied power at the applicator input. MWA computational models were implemented using the finite element method, and incorporated temperature-dependent changes in tissue physical properties. Model-predicted ablation zone extents were compared against MRI-derived Arrhenius thermal damage maps using the Dice similarity coefficient (DSC). Results: Prior to heating, the observed standard deviation of MR temperature data was in the range of 0.3-0.7°C. Mean absolute error between MR temperature measurements and fiber-optic temperature probes during heating was in the range of 0.5-2.8°C. The mean DSC between model-predicted ablation zones and MRI-derived Arrhenius thermal damage maps for 13 experimental setups was 0.95. When comparing simulated and experimentally (i.e. using MRI) measured temperatures, the mean absolute error (MAE %) relative to maximum temperature change was in the range 5%-8.5%. Conclusion: We developed a system for characterizing 3D transient temperature and ablation profiles with MR thermometry during MWA in ex vivo liver tissue, and applied the system for experimental validation of MWA computational models.

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

Abstract: The tested MR-compatible system can be used without loss of ablation performance compared to the standard system.

Cited by 5 publications

References 34 publications

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

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

2450-MHz microwave ablation of liver metastases under 3.0 T wide-bore magnetic resonance guidance: a pilot study

Experimental assessment of microwave ablation computational modeling with MR thermometry

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