Computer modeling of the effect of perfusion on heating patterns in radiofrequency tumor ablation

Liu, Z; Ahmed, Muneeb; Sabir, Adeel; Humphries, S.; Goldberg, S. Nahum

doi:10.1080/02656730601094415

Cited by 52 publications

(37 citation statements)

References 40 publications

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“…For the bipolar RF electrode configuration, the current circulated between the anode and the cathode of the active zone (3 cm long) of the electrode, generating a symmetrical ellipsoidal heating pattern, with its long axis coinciding with the axis of the electrode. Thus, in the transverse plane containing the temperature probes, circles concentric with the RF electrode corresponded to pixels with the same temperature evolution, as the current density profile, as well as the heat conduction pattern, were circularly symmetrical in this plane (20).…”

Section: Experimental Phantom Validationmentioning

confidence: 99%

Validation of fast MR thermometry at 1.5 T with gradient‐echo echo planar imaging sequences: phantom and clinical feasibility studies

et al. 2008

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The purpose of this work was to validate in phantom studies and demonstrate the clinical feasibility of MR proton resonance frequency thermometry at 1.5 T with segmented gradient-echo echo planar imaging (GRE-EPI) sequences during liver tumour radiofrequency (RF) ablation. Classical GRE acquisitions and segmented GRE-EPI acquisitions were performed at 1.5 T during simultaneous RF heating with an MR-compatible RF electrode placed in an agar gel phantom. Temperature increments were calculated and compared with four optical temperature probe measurements using Bland- Altman analysis. In a preliminary clinical feasibility study, the rapid GRE-EPI sequence (echo train length = 13) was used for MR temperature monitoring of RF ablation of liver tumours in three patient procedures. For phantom experiments, the Bland-Altman mean of differences between MR and optical probe temperature measurements was <0.4 degrees C, and the 95% limits of agreement value was <1.4 degrees C. For the in vivo studies, respiratory-triggered GRE-EPI acquisitions yielded a temperature accuracy of 1.3 +/- 0.4 degrees C (acquisition time = 0.6 s/image, spatial coverage of three slices/respiratory cycle). MR proton resonance frequency thermometry at 1.5 T yields precise and accurate measurements of temperature increment with both classical GRE and rapid GRE-EPI sequences. Rapid GRE-EPI sequences minimize intra-scan motion effects and can be used for MR thermometry during RF ablation in moving organs.

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Section: Experimental Phantom Validationmentioning

confidence: 99%

Validation of fast MR thermometry at 1.5 T with gradient‐echo echo planar imaging sequences: phantom and clinical feasibility studies

et al. 2008

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“…Simulation data correspond to the t 43 ≥ 600 min isodose boundary calculated by the bioacoustics-thermal model, which did not include the effects of perfusion. 60,61 In the in vivo setting, where there is a substantial heat sink associated with blood flow, larger applied power levels were specified for heating durations of 10-15 min. The selected power levels were chosen to be the highest power levels which yielded a maximal tissue temperature below 100…”

Section: Iid Bioacoustic-thermal Modelmentioning

confidence: 99%

Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

et al. 2012

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Purpose: To evaluate multiple applicator implant configurations of interstitial ultrasound devices for large volume ablation of liver tumors. Methods: A 3D bioacoustic-thermal model using the finite element method was implemented to assess multiple applicator implant configurations for thermal ablation with interstitial ultrasound energy. Interstitial applicators consist of linear arrays of up to four 10 mm-long tubular ultrasound transducers, each under separate and dynamic power control, enclosed within a water-cooled delivery catheter (2.4 mm OD). The authors considered parallel implants with two and three applicators (clustered configuration), spaced 2-3 cm apart, to simulate open surgical placement. In addition, the authors considered two applicator implants with applicators converging and diverging at angles of ∼20• , 30• , and 45• to simulate percutaneous placement. Heating experiments (10-15 min) were performed and compared against simulations employing the same experimental parameters. To estimate the performance of parallel, multiple applicator configurations in an in vivo setting, simulations were performed taking into account a range of blood perfusion levels (0, 5, 12, and 15 kg m −3 s −1 ) that may occur in tumors of varying vascularity. The impact of tailoring the power supplied to individual transducer elements along the length of applicators is explored for applicators inserted in non-parallel (converging and diverging) configurations. Thermal dose (t 43 > 240 min) and temperature thresholds (T > 52• C) were used to define the ablation zones, with dynamic changes to tissue acoustic and thermal properties incorporated within the model. Results: Experiments in ex vivo bovine liver yielded ablation zones ranging between 4.0-5.6 cm × 3.2-4.9 cm, in cross section. Ablation zone dimensions predicted by simulations with similar parameters to the experiments were in close agreement (within 5 mm). Simulations of in vivo heating showed that 15 min heating and interapplicator spacing less than 3 cm are required to obtain contiguous, complete ablation zones. The ability to create complete ablation zone profiles for nonparallel implants was illustrated by tailoring applied power levels along the length of applicators. Conclusions: Parallel implants consisting of three interstitial ultrasound applicators in a triangular configuration yield complete ablation zones measuring up to 6.2 cm × 5.7 cm after 15 min heating. At larger interapplicator spacing, the level of blood perfusion in the tumor may yield indentations along the periphery of the ablation zone. Tailoring applied power along the length of the applicator can accommodate for nonparallel implants, without compromising safety.

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“…a. Obtaining adequate ablative margins is essential (strong consensus) Colorectal liver metastases are less well perfused than the surrounding liver so it is easier to ablate to the tumour edge than to ablate the normally perfused liver around the metastasis which is required in order to achieve an ablative margin [62]. Applicators need to be positioned specifically to achieve a margin.…”

Section: Maximising Local Tumour Controlmentioning

confidence: 99%

Thermal ablation of colorectal liver metastases: a position paper by an international panel of ablation experts, the interventional oncology sans frontières meeting 2013

et al. 2015

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Objectives Previous attempts at meta-analysis and systematic review have not provided clear recommendations for the clinical application of thermal ablation in metastatic colorectal cancer. Many authors believe that the probability of gathering randomised controlled trial (RCT) data is low. Our aim is to provide a consensus document making recommendations on the appropriate application of thermal ablation in patients with colorectal liver metastases. Methods This consensus paper was discussed by an expert panel at The Interventional Oncology Sans Frontières 2013. A literature review was presented. Tumour characteristics, ablation technique and different clinical applications were considered and the level of consensus was documented.Eur Radiol (2015) Results Specific recommendations are made with regard to metastasis size, number, and location and ablation technique. Mean 31 % 5-year survival post-ablation in selected patients has resulted in acceptance of this therapy for those with technically inoperable but limited liver disease and those with limited liver reserve or co-morbidities that render them inoperable.Conclusions In the absence of RCT data, it is our aim that this consensus document will facilitate judicious selection of the patients most likely to benefit from thermal ablation and provide a unified interventional oncological perspective for the use of this technology. Key Points• Best results require due consideration of tumour size, number, volume and location.• Ablation technology, imaging guidance and intraprocedural imaging assessment must be optimised.• Accepted applications include inoperable disease due to tumour distribution or inadequate liver reserve.• Other current indications include concurrent co-morbidity, patient choice and the test-of-time approach.• Future applications may include resectable disease, e.g. for small solitary tumours.

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Computer modeling of the effect of perfusion on heating patterns in radiofrequency tumor ablation

Cited by 52 publications

References 40 publications

Validation of fast MR thermometry at 1.5 T with gradient‐echo echo planar imaging sequences: phantom and clinical feasibility studies

Validation of fast MR thermometry at 1.5 T with gradient‐echo echo planar imaging sequences: phantom and clinical feasibility studies

Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

Thermal ablation of colorectal liver metastases: a position paper by an international panel of ablation experts, the interventional oncology sans frontières meeting 2013

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