Renal Artery Embolization Combined With Radiofrequency Ablation in a Porcine Kidney Model: Effect of Small and Narrowly Calibrated Microparticles as Embolization Material on Coagulation Diameter, Volume, and Shape

Creation of an ex-vivo bovine kidney flow model for testing embolic agents: work in progress

Objectives

To develop an ex- vivo perfusion flow model using a bovine kidney for future testing of embolic agents in an inexpensive and easy way.

Methods

Six bovine adult kidneys were used for this study. Kidneys were cannulated and perfused via a roller pump. Three embolic agents, coils, Gelfoam, and a glue mixture of Histoacryl + Lipiodol, were deployed by targeting three secondary segmental arteries per kidney via a 5Fr catheter under fluoroscopic guidance. Cannulation time, success rate of segmental artery selection and embolic agent deployment, total operational time, and fluoroscopy dose were recorded.

Results

Average kidney weight was 0.752 +/− 0.094 kg. All six bovine kidneys were successfully cannulated in 21.6 min +/− 3.0 min. Deployment of coils and glue was achieved in every case (12/12); however, Gelfoam injection was not successful in one instance (5/6, 83%). Coil deployment demonstrated no embolic effect while Gelfoam and glue injections demonstrated decreased distal contrast filling post-embolization. Mean dose area product was 12.9 ± 1.8 Gy·cm2, fluoroscopy time was 10 ± 4 min and operational time was 27 ± 8 min.

Conclusions

We describe the creation of an ex vivo bovine kidney flow model for the preclinical evaluation of different embolic materials. The flow model can be modified to provide extensive bench testing and it is a promising tool for hands -on training in basic and advanced embolization techniques .

Electrochemical Effects after Transarterial Chemoembolization in Combination with Percutaneous Irreversible Electroporation: Observations in an Acute Porcine Liver Model

PURPOSE

To evaluate the effects of combined use of transarterial chemoembolization and irreversible electroporation (IRE) for focal tissue ablation in an acute porcine liver model.

MATERIALS AND METHODS

Two established interventional techniques were combined: IRE with zones of irreversible and reversible electroporation and chemoembolization with microspheres, iodized oil, and doxorubicin. IRE was performed before chemoembolization in two pigs (pigs 1 and 2; IRE/chemoembolization group), chemoembolization was performed before IRE in two pigs (pigs 3 and 4; chemoembolization/IRE group), and only IRE was performed in two pigs (pigs 5 and 6). Five study groups were defined: IRE/chemoembolization (pigs 1 and 2), chemoembolization/IRE (pigs 3 and 4), IRE only (pigs 5 and 6), chemoembolization only (tissue outside the IRE zones in pigs 1-4), and control (untreated liver tissue outside the IRE zones in pigs 5 and 6). Animals were euthanized 2 hours after intervention. Size and shape of IRE zones on contrast-enhanced computed tomography, cell death on light microscopy, and doxorubicin tissue concentrations on chromatography and fluorescence microscopy were analyzed.

RESULTS

Size and shape of IRE zones were not significantly different (eg, P = .067 for volume). A histologic marker for irreversible cell death was positive in IRE/chemoembolization, chemoembolization/IRE, and IRE groups only in the macroscopically visible IRE zones. Doxorubicin tissue concentrations were not significantly different (P = .873). However, in the reversible electroporation (RE) zones, broad areas with intense intranuclear doxorubicin accumulation were observed in IRE/chemoembolization but not in chemoembolization/IRE and chemoembolization groups.

CONCLUSIONS

IRE before chemoembolization enhances the intranuclear accumulation of doxorubicin in the RE zone.

Sphere-enhanced microwave ablation (sMWA) versus bland microwave ablation (bMWA): technical parameters, specific CT 3D rendering and histopathology

PURPOSE

This study was designed to compare technical parameters during ablation as well as CT 3D rendering and histopathology of the ablation zone between sphere-enhanced microwave ablation (sMWA) and bland microwave ablation (bMWA).

METHODS

In six sheep-livers, 18 microwave ablations were performed with identical system presets (power output: 80 W, ablation time: 120 s). In three sheep, transarterial embolisation (TAE) was performed immediately before microwave ablation using spheres (diameter: 40 ± 10 μm) (sMWA). In the other three sheep, microwave ablation was performed without spheres embolisation (bMWA). Contrast-enhanced CT, sacrifice, and liver harvest followed immediately after microwave ablation. Study goals included technical parameters during ablation (resulting power output, ablation time), geometry of the ablation zone applying specific CT 3D rendering with a software prototype (short axis of the ablation zone, volume of the largest aligned ablation sphere within the ablation zone), and histopathology (hematoxylin-eosin, Masson Goldner and TUNEL).

RESULTS

Resulting power output/ablation times were 78.7 ± 1.0 W/120 ± 0.0 s for bMWA and 78.4 ± 1.0 W/120 ± 0.0 s for sMWA (n.s., respectively). Short axis/volume were 23.7 ± 3.7 mm/7.0 ± 2.4 cm(3) for bMWA and 29.1 ± 3.4 mm/11.5 ± 3.9 cm(3) for sMWA (P < 0.01, respectively). Histopathology confirmed the signs of coagulation necrosis as well as early and irreversible cell death for bMWA and sMWA. For sMWA, spheres were detected within, at the rim, and outside of the ablation zone without conspicuous features.

CONCLUSIONS

Specific CT 3D rendering identifies a larger ablation zone for sMWA compared with bMWA. The histopathological signs and the detectable amount of cell death are comparable for both groups. When comparing sMWA with bMWA, TAE has no effect on the technical parameters during ablation.

Irreversible electroporation of the pig kidney with involvement of the renal pelvis: technical aspects, clinical outcome, and three-dimensional CT rendering for assessment of the treatment zone

PURPOSE

To analyze irreversible electroporation (IRE) of the pig kidney with involvement of the renal pelvis.

MATERIALS AND METHODS

IRE of renal tissue including the pelvis was performed in 10 kidneys in five pigs. Three study groups were defined: group I (two applicators with parallel configuration; n = 11), group II (three applicators with triangular configuration; n = 2), and group III (six applicators with complex configuration; n = 3). After IRE and before euthanasia, pigs underwent contrast-enhanced computed tomography (CT). Technical aspects (radial distance of applicators, resulting mean current), clinical outcome (complications, blood samples), and three-dimensional CT rendering for assessment of the treatment zone (short axis, circularity) were assessed.

RESULTS

Radial distances of applicators were 14.3 mm ± 2.8 in group I, 12.3 mm ± 1.9 in group II, and 16.4 mm ± 3.5 in group III. Resulting mean currents were 25.7 A ± 6.5 in group I, 27.0 A ± 7.1 in group II, and 39.4 A ± 8.9 in group III. In group III, two perirenal hematomas were identified. There was no damage to the renal pelvis. During IRE, clinical blood parameters and cardiovascular markers did not change significantly. Short axis measurements were 20.6 mm ± 3.6 in group I, 31.9 mm ± 8.2 in group II, and 39.3 mm ± 2.4 in group III (P < .01 between groups). Circularity scores were 0.8 ± 0.2 in group I, 0.7 ± 0.1 in group II, and 0.7 ± 0.1 in group III, with a score of 1 indicating perfect roundness (P value not significant).

CONCLUSIONS

IRE of the pig kidney with involvement of the renal pelvis is feasible and safe. Size but not shape of the treatment zone is significantly affected by applicator configuration.

CT-guided irreversible electroporation in an acute porcine liver model: effect of previous transarterial iodized oil tissue marking on technical parameters, 3D computed tomographic rendering of the electroporation zone, and histopathology

PURPOSE

To evaluate the effect of previous transarterial iodized oil tissue marking (ITM) on technical parameters, three-dimensional (3D) computed tomographic (CT) rendering of the electroporation zone, and histopathology after CT-guided irreversible electroporation (IRE) in an acute porcine liver model as a potential strategy to improve IRE performance.

METHODS

After Ethics Committee approval was obtained, in five landrace pigs, two IREs of the right and left liver (RL and LL) were performed under CT guidance with identical electroporation parameters. Before IRE, transarterial marking of the LL was performed with iodized oil. Nonenhanced and contrast-enhanced CT examinations followed. One hour after IRE, animals were killed and livers collected. Mean resulting voltage and amperage during IRE were assessed. For 3D CT rendering of the electroporation zone, parameters for size and shape were analyzed. Quantitative data were compared by the Mann-Whitney test. Histopathological differences were assessed.

RESULTS

Mean resulting voltage and amperage were 2,545.3 ± 66.0 V and 26.1 ± 1.8 A for RL, and 2,537.3 ± 69.0 V and 27.7 ± 1.8 A for LL without significant differences. Short axis, volume, and sphericity index were 16.5 ± 4.4 mm, 8.6 ± 3.2 cm(3), and 1.7 ± 0.3 for RL, and 18.2 ± 3.4 mm, 9.8 ± 3.8 cm(3), and 1.7 ± 0.3 for LL without significant differences. For RL and LL, the electroporation zone consisted of severely widened hepatic sinusoids containing erythrocytes and showed homogeneous apoptosis. For LL, iodized oil could be detected in the center and at the rim of the electroporation zone.

CONCLUSION

There is no adverse effect of previous ITM on technical parameters, 3D CT rendering of the electroporation zone, and histopathology after CT-guided IRE of the liver.

A nanoengineered embolic agent for precise radiofrequency ablation

The purpose of the work is to investigate whether the electromagnetic properties of multi-walled carbon nanotubes (MWCNT) in the presence of radiofrequency (RF) energy is (1) safe, and (2) improves the precision of the therapeutic efficiency of the RF-ablation (RFA) procedure. An in vitro phantom was created for evaluating temperature near RF treated nanotubes. For the in vivo study, three baboons and six pigs were submitted for RFA procedure in superior/inferior kidney poles embolized with a non-adherent, lipophilic embolic agent (marsembol) with or without MWCNT. Tissue damage in the surrounding kill zone was assayed through caspase-3 activation. The in vitro results showed marked heat increase only in the region of the nanotubes. In vivo, necrosis/ischemic damage resulted from RFA therapy alone, RFA plus marsembol only. In marsembol + MWCNT condition, dramatic disruption of cell membranes and sub-cellular organelles was found whereas the nuclear membranes and basal cell membranes remained largely intact. The marsembol vaporized under RFA and tissue fluid filled the space. This caused the MWCNT to cluster within the new aqueous environment. RFA plus marsembol + MWCNT created a well-defined demarcation between healthy and apoptotic cells as evidenced by a marked reduction of caspase-3 expression. By contrast, there was a much less defined ablation zone in the absence of MWCNT. In conclusion, the combination of RFA plus marsembol + MWCNT embolization delineated the kill zone in vitro and in vivo. We demonstrate that MWCNTs remain in the ablation region thus minimizing their migration to the systemic circulation.

Specific CT 3D rendering of the treatment zone after Irreversible Electroporation (IRE) in a pig liver model: the "Chebyshev Center Concept" to define the maximum treatable tumor size

Background

Size and shape of the treatment zone after Irreversible electroporation (IRE) can be difficult to depict due to the use of multiple applicators with complex spatial configuration. Exact geometrical definition of the treatment zone, however, is mandatory for acute treatment control since incomplete tumor coverage results in limited oncological outcome. In this study, the “Chebyshev Center Concept” was introduced for CT 3d rendering to assess size and position of the maximum treatable tumor at a specific safety margin.

Methods

In seven pig livers, three different IRE protocols were applied to create treatment zones of different size and shape: Protocol 1 (n = 5 IREs), Protocol 2 (n = 5 IREs), and Protocol 3 (n = 5 IREs). Contrast-enhanced CT was used to assess the treatment zones. Technique A consisted of a semi-automated software prototype for CT 3d rendering with the “Chebyshev Center Concept” implemented (the “Chebyshev Center” is the center of the largest inscribed sphere within the treatment zone) with automated definition of parameters for size, shape and position. Technique B consisted of standard CT 3d analysis with manual definition of the same parameters but position.

Results

For Protocol 1 and 2, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were not significantly different between Technique A and B. For Protocol 3, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were significantly smaller for Technique A compared with Technique B (41.1 ± 13.1 mm versus 53.8 ± 1.1 mm and 39.0 ± 8.4 mm versus 53.8 ± 1.1 mm; p < 0.05 and p < 0.01). For Protocol 1, 2 and 3, sphericity of the treatment zone was significantly larger for Technique A compared with B.

Conclusions

Regarding size and shape of the treatment zone after IRE, CT 3d rendering with the “Chebyshev Center Concept” implemented provides significantly different results compared with standard CT 3d analysis. Since the latter overestimates the size of the treatment zone, the “Chebyshev Center Concept” could be used for a more objective acute treatment control.

Solid renal masses: effectiveness and safety of image-guided percutaneous radiofrequency ablation

With increasing emphasis on minimally invasive nephron-sparing techniques for treatment of renal tumors, image-guided percutaneous radiofrequency ablation (RFA) has emerged as a safe and effective method of tumor eradication that may be performed on an outpatient basis, with relatively low morbidity and mortality. This review addresses the clinical and technical considerations, risks, complications, and currently reported efficacy data pertaining to RFA of renal tumors, as well as the standardized approach to treatment and follow-up currently used in our practice.