Influence of Intrahepatic Vessels on Volume and Shape of Percutaneous Thermal Ablation Zones

Frericks, Bernd; Ritz, JP; Albrecht, Thomas; Valdeig, S.; Schenk, Andrea; Wolf, Karl‐Jürgen; Lehmann, Kai S.

doi:10.1097/rli.0b013e31815daf36

Cited by 58 publications

(43 citation statements)

References 26 publications

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“…As has been published earlier [32,33], the cooling effect of different hepatic vascular systems (that is in particular, the portal venous (PV) versus the hepatic venous (HV) tree) result in considerably different necrosis shapes, see Fig. (13).…”

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confidence: 74%

Fast Estimation of the Vascular Cooling in RFA Based on Numerical Simulation

Kröger¹,

Pätz²,

Altrogge³

et al. 2010

TOBEJ

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Abstract:We present a novel technique to predict the outcome of an RF ablation, including the vascular cooling effect. The main idea is to separate the problem into a patient independent part, which has to be performed only once for every applicator model and generator setting, and a patient dependent part, which can be performed very fast. The patient independent part fills a look-up table of the cooling effects of blood vessels, depending on the vessel radius and the distance of the RF applicator from the vessel, using a numerical simulation of the ablation process. The patient dependent part, on the other hand, only consists of a number of table look-up processes. The paper presents this main idea, along with the required steps for its implementation. First results of the computation and the related ex-vivo evaluation are presented and discussed. The paper concludes with future extensions and improvements of the approach.

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mentioning

confidence: 74%

Fast Estimation of the Vascular Cooling in RFA Based on Numerical Simulation

Kröger¹,

Pätz²,

Altrogge³

et al. 2010

TOBEJ

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“…Measured tissue temperatures above 90°C within the heated zone are in favor of this hypothesis. However, the situation may be different for target tissue directly adjacent to vessels, where cooling mechanisms proceed faster (27,28).…”

Section: Discussionmentioning

confidence: 99%

Prediction of cell necrosis with sequential temperature mapping after radiofrequency ablation

Rempp

Clasen

Boss

et al. 2009

Magnetic Resonance Imaging

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Purpose:To assess the feasibility of magnetic resonance (MR) thermometry after thermoablative therapy and to quantitatively evaluate the ability of two sequence types to predict cell necrosis. Methods:Twenty patients with hepatic tumors were treated by MR-guided radiofrequency ablation. For each 10 patients, postinterventionally performed gradient echo and segmented echo planar imaging sequences were used to calculate temperature maps based on the proton resonance frequency shift method. Contrast-enhanced images acquired 1 month after therapy were registered on the temperature maps and the necrotic, nonenhanced area was segmented and compared to the area with a displayed temperature above 60°C. Sensitivity and positive predictive value of the temperature map was calculated, using the follow-up imaging as the gold standard. Results:Temperature mapping reached acceptable image quality in 45/47 cases. Sensitivity, ie, the rate of correctly detected coagulated tissue was 0.82 Ϯ 0.08 for the gradient echo imaging (GRE) sequence and 0.81 Ϯ 0.14 for the echo planar imaging (EPI) sequence. Positive predictive value, ie, the rate of voxel in the temperature map over 60°C that actually developed necrosis, was 0.90 Ϯ 0.07 for the GRE sequence and 0.84 Ϯ 0.11 for the EPI sequence. Conclusion:Sequential MR temperature mapping allows for the prediction of the coagulation zone with an acceptable sensitivity and positive predictive value using EPI and GRE sequences. REAL-TIME TEMPERATURE MAPPING of magnetic resonance (MR)-guided minimally invasive radiofrequency (RF) ablation has been shown to be feasible both ex vivo (1) and in vivo (2-5), and has the potential of becoming the gold standard for therapy monitoring of thermoablative therapies. Different MR techniques have been proposed for temperature measurement (6 -10); the most frequently used is the proton resonance frequency shift (PRF) method (11-14), which is based on a temperature-dependent phase shift allowing for the measurement of temperature changes relative to a baseline image. With frequent repetitive measurements during thermoablative therapy, this approach allows a precise estimation of the lethal thermal dose (15) based on the Arrhenius model (16,17) and could be used to predict the size and position of the coagulation zone in animal studies (3,5). Furthermore, real-time temperature monitoring could allow for visualizing a vessel-related cooling effect and thus prevent a survival of cancer cells due to an undetected heat-sink effect.Due to technical and medical challenges linked to this approach, the majority of the literature up to now concerns preclinical questions. In case of RF ablation, the simultaneous use of an RF generator with frequencies between 300 and 500 kHz during imaging decreases image quality (6,18). To date, only noncommercial filters were used to overcome this problem (4,18) or generators with an adapted frequency were employed in animal studies (3,19). Therefore, we performed temperature measurement with a sequential approach: The sedated pat...

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“…4. Another source of variability may be the heat sink effect due to blood flow within vessels carrying away the heat energy deposited [35][36]. It was possible to avoid forming ablations near major blood vessels in this study; however, the liver is a vascular structure, and smaller vessels could not be avoided in all cases.…”

Section: Discussionmentioning

confidence: 99%

Quantifying local stiffness variations in radiofrequency ablations with dynamic indentation

DeWall

Varghese

Brace

2011

2011 IEEE International Ultrasonics Symposium

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Elastographic imaging can be used to monitor ablation procedures, however confident and clear determination of the ablation boundary is essential to ensure complete treatment of the pathological target. To investigate the potential for ablation boundary representation on elastographic images, local variations in the viscoelastic properties in radiofrequency ablated regions that were formed in vivo in porcine liver tissue were quantified using dynamic indentation. Spatial stiffness maps were then correlated to stained histology, the gold standard for determination of the ablation periphery or boundary. Regions of interest in eleven radiofrequency ablation samples were indented at 18-24 locations each, including the central zone of complete necrosis and more peripheral transition zones including normal tissue. Storage modulus and rate of stiffening were both greatest in the central ablation zone and decreased with radial distance away from the center. The storage modulus and modulus contrast at the ablation outer transition zone boundary were 3.1 ± 1.0 kPa and 1.6 ± 0.4, respectively, and 36.2 ± 9.1 kPa and 18.3 ± 5.5 at the condensation boundary within the ablation zone. Elastographic imaging modalities were then compared to gross pathology in ex vivo bovine liver tissue. Area estimated from strain, shear wave velocity, and gross pathology images were 470 mm 2 , 560 mm 2 , and 574 mm 2 , respectively, and ablation widths were 19.4 mm, 20.7 mm, and 23.0 mm. This study has provided insights into spatial stiffness distributions within radiofrequency ablations and suggests that low stiffness contrast on the ablation periphery leads to the observed underestimation of ablation extent on elastographic images.

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Influence of Intrahepatic Vessels on Volume and Shape of Percutaneous Thermal Ablation Zones

Cited by 58 publications

References 26 publications

Fast Estimation of the Vascular Cooling in RFA Based on Numerical Simulation

Fast Estimation of the Vascular Cooling in RFA Based on Numerical Simulation

Prediction of cell necrosis with sequential temperature mapping after radiofrequency ablation

Quantifying local stiffness variations in radiofrequency ablations with dynamic indentation

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