Computer modeling of the combined effects of perfusion, electrical conductivity, and thermal conductivity on tissue heating patterns in radiofrequency tumor ablation

Ahmed, Muneeb; Liu, Zhengjun; Humphries, S.; Goldberg, S. Nahum

doi:10.1080/02656730802192661

Cited by 86 publications

(63 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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

View full text Add to dashboard Cite

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.

show abstract

Section: Iid Bioacoustic-thermal Modelmentioning

confidence: 99%

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

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Second, conductive heat transfer is relatively slow in most tissues and in the in vivo setting has limited ability to overcome relatively minor competing processes, such as perfusion and ventilation. As a result, RF ablation zones can vary widely according to the local tissue environment (10,11). For example, aerated lung is characterized by high impedance to electric current flow and poor heat transfer compared with most solid organs.…”

Section: Introductionmentioning

confidence: 99%

Percutaneous Tumor Ablation Tools: Microwave, Radiofrequency, or Cryoablation—What Should You Use and Why?

Hinshaw¹,

Lubner²,

Ziemlewicz³

et al. 2014

RadioGraphics

286

213

View full text Add to dashboard Cite

“…In some cases, the model simply reduces the applied voltage to the maximum level at which no tissue is heated beyond 100ºC [4][5][6]. Others do not provide details of the RF power delivery protocol [7], so we cannot be sure whether an impedance-controlled pulsing protocol was really modeled.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous modeling studies have been published on RFA with needle-like cooled electrodes [4][5][6][7][8][9][10][11] although they rarely provide sufficient details of the pulsing protocol used.…”

Section: Introductionmentioning

confidence: 99%

Computer modelling of an impedance-controlled pulsing protocol for RF tumour ablation with a cooled electrode

Trujillo

Bon

Rivera

et al. 2016

International Journal of Hyperthermia

View full text Add to dashboard Cite

Purpose: To develop computer models to mimic the impedance-controlled pulsing protocol implemented in RF generators used for clinical practice of radiofrequency ablation (RFA), and to assess the appropriateness of the models by comparing the computer results with those obtained in previous experimental studies.Methods: A 12-minute RFA was modeled using a cooled electrode (17G, 3 cm tip) inserted in hepatic tissue. The short (transverse) diameter of the coagulation zone was assessed under in vivo (with blood perfusion and considering clamping) and ex vivo (at 21ºC) conditions.The computer results obtained by programming voltage pulses were compared with current pulses.Results: The differences between voltage and current pulses protocol were noticeable: using current instead of voltage allows larger coagulation zones to be created, due to the higher energy applied by current pulses. If voltage pulses are employed, the model can accurately predict number of roll-offs, although the waveform of the applied power is clearly not realistic. If current voltages are employed, the applied power waveform matches well with those reported experimentally, but there are significantly fewer roll-offs. Our computer results were overall into the ranges of experimental ones. Conclusions:The proposed models reproduce reasonably well the electrical-thermal performance and coagulation zone size obtained during an impedance-controlled pulsing protocol.

show abstract

Computer modeling of the combined effects of perfusion, electrical conductivity, and thermal conductivity on tissue heating patterns in radiofrequency tumor ablation

Abstract: Optimal combinations of thermal and electrical conductivity can partially negate the effect of perfusion. For clinically relevant tumor sizes, thermal and electrical conductivity impact which tumors can be successfully ablated even in the setting of almost non-existent perfusion.

Cited by 86 publications

References 39 publications

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

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

Percutaneous Tumor Ablation Tools: Microwave, Radiofrequency, or Cryoablation—What Should You Use and Why?

Computer modelling of an impedance-controlled pulsing protocol for RF tumour ablation with a cooled electrode

Contact Info

Product

Resources

About