Technical characterization of a new bipolar and multipolar radiofrequency device for minimally invasive treatment of renal tumours

A History of the Development of Radiofrequency Neurotomy

The technique of lumbar medial branch radiofrequency neurotomy for facet joint pain has an intriguing history involving a diverse timeline of medical specialists. This paper aims to chart the pathway that led to its invention and the series of modifications and refinements that have led to modern practice. The story begins with the treatment of World War I soldiers by Nesfield, who used scalpels to cut “trapped” nerves. Inspired by Nesfield’s treatment, Rees developed the “percutaneous rhizolysis” technique in 1960. Shealy was the first to use radiofrequency electrodes for denervation of the facet joints, introducing his technique in 1971. Several radiofrequency electrode developments came about from collaborations with Cosman medical device entrepreneurs during the 1970s, including the Shealy Rhizolysis Kit, the Ray Rhizotomy Electrode, and the Sluijter-Mehta Kit. Subsequent dissections of Rees’ technique and modification of Shealy’s procedure by Bogduk saw the development of “percutaneous lumbar medial branch neurotomy” in 1980 by Bogduk and Long. Bogduk continued to contribute significantly to validation, refinement and acceptance of the technique. In 1998, the technique of pulsed radiofrequency was invented by Sluijter, Cosman, Rittman and van Kleef. Subsequent innovations have consisted of cooled radiofrequency neurotomy, multi-tined cannulae, endoscopic systems, and alternative denervation targets, such as the facet joint capsule. As we pass the first 100 years of the story, we believe there are more chapters to be written on this fascinating subject.

One-year results of the use of endovenous radiofrequency ablation utilising an optimised radiofrequency-induced thermotherapy protocol for the treatment of truncal superficial venous reflux

Background

In previous in vitro and ex vivo studies, we have shown increased thermal spread can be achieved with radiofrequency-induced thermotherapy when using a low power and slower, discontinuous pullback. We aimed to determine the clinical success rate of radiofrequency-induced thermotherapy using this optimised protocol for the treatment of superficial venous reflux in truncal veins.

Methods

Sixty-three patients were treated with radiofrequency-induced thermotherapy using the optimised protocol and were followed up after one year (mean 16.3 months). Thirty-five patients returned for audit, giving a response rate of 56%. Duplex ultrasonography was employed to check for truncal reflux and compared to initial scans.

Results

In the 35 patients studied, there were 48 legs, with 64 truncal veins treated by radiofrequency-induced thermotherapy (34 great saphenous, 15 small saphenous and 15 anterior accessory saphenous veins). One year post-treatment, complete closure of all previously refluxing truncal veins was demonstrated on ultrasound, giving a success rate of 100%.

Conclusions

Using a previously reported optimised, low power/slow pullback radiofrequency-induced thermotherapy protocol, we have shown it is possible to achieve a 100% ablation at one year. This compares favourably with results reported at one year post-procedure using the high power/fast pullback protocols that are currently recommended for this device.

A Prospective, Randomized, Multicenter, Open-label Clinical Trial Comparing Intradiscal Biacuplasty to Conventional Medical Management for Discogenic Lumbar Back Pain

STUDY DESIGN

This study was a prospective, randomized, crossover, multicenter trial for the evaluation of comparative effectiveness of intradiscal biacuplasty (IDB) versus conventional medical management (CMM) in the treatment of lumbar discogenic pain.

OBJECTIVE

The objective was to demonstrate the superiority of IDB over CMM in the treatment of discogenic pain with respect to the primary outcome measure.

SUMMARY OF BACKGROUND DATA

Current therapeutic options for the treatment of chronic low back pain of discogenic origin are limited. CMM is often unsatisfactory with regard to the treatment of discogenic pain. IDB offers a minimally invasive treatment that has been demonstrated to be superior to placebo in the past.

METHODS

A total of 63 subjects with lumbar discogenic pain diagnosed via provocation discography were randomized to IDB + CMM (n = 29) or CMM-alone (n = 34). At 6 months, patients in the CMM-alone group were eligible for crossover if desired. The primary outcome measure was the change in visual analog scale (VAS) from baseline to 6 months. Secondary outcome measures included treatment "responders," defined as the proportion of subjects with a 2-point or 30% decrease in VAS scores. Other secondary measures included changes from baseline to 6 months in (1) short form (SF) 36-physical functioning, (2) Oswestry Disability Index, (3) Beck Depression Inventory, (4) Patient Global Impression of Change, (5) EQ-5D VAS, and (6) back pain-related medication usage.

RESULTS

In the IDB cohort, the mean VAS score reduction exceeded that in the CMM cohort (-2.4 vs. -0.56; P = 0.02), and the proportion of treatment responders was substantially greater (50% vs. 18%). Differences in secondary measures favored IDB. No differences in opioid utilization were noted between groups.

CONCLUSION

Superior performance of IDB with respect to all study outcomes suggests that it is a more effective treatment for discogenic pain than CMM-alone.

LEVEL OF EVIDENCE

2.

An in vitro study to optimise treatment of varicose veins with radiofrequency-induced thermo therapy

Objective

To develop a reproducible method of using radiofrequency-induced thermotherapy with adequate thermal spread to ablate the whole vein wall in a truncal vein but avoiding carbonisation, device sticking and high impedance “cut outs” reducing interruptions during endovenous treatments.

Methods

Porcine liver was treated with radiofrequency-induced thermotherapy under glass to allow measurements, observation and video recording. Powers of 6–20 W were used at varying pullback speeds to achieve linear endovenous energy densities of 18–100 J/cm. Thermal spread, carbonisation of treated tissue and high-impedance cut outs were recorded.

Results

The currently recommended power settings of 18 and 20 W produced sub-optimal results. If pulled back at 3 s/cm to achieve linear endovenous energy densities around 60 J/cm, tissue carbonisation and high impedance cut outs occurred. When high powers and fast pullbacks of 1 s/cm were used, no carbonisation or cut outs occurred but thermal ablation of the liver model was below target due to reduced time for thermal conduction. Low powers (6–12 W) with slow pullbacks (6–12 s/cm) achieved target thermal ablation with minimal carbonisation and high impedance cut outs.

Conclusions

Using low power (6 W) and a slow discontinuous pullback (6 s every 0.5 cm, in steps), we were able to achieve our target thermal ablation in the porcine liver model without carbonisation and high impedance cut outs. This suggests the currently recommended power levels could be reduced, reducing the need to remove the device to clean the electrodes during treatment while achieving target thermoablation of the treated tissue.

Analysis of radiofrequency ablation of small renal tumors in patients at high anesthetic and surgical risk: urologist experience with follow-up results in the initial six months

BACKGROUND

To evaluate the results of various types of radiofrequency ablation (RFA) treatment of renal tumors in patients with excessive anesthetic and surgical risk.

MATERIALS AND METHODS

Data for RFA performed in in high risk patients were retrospectively evaluated. Other RFA applications in patients with no anesthetic and/or surgical risk were excluded. RFA was by ultrasound or CT guided percutaneous (USG/CT-PRFA) and retroperitoneally or transperitoneally laparoscopic (R/T-LRFA) techniques under general or local anethesia. Follow-up data of enhanced CT or MRI after 1, 3 and 6 months were analysed for twelve RFA applications.

RESULTS

The RFA applications included 4 (40%) left-sided, 5 (50%) right-sided and 1 (10%) bilaterally RFA (simultaneously 1 right and 2 left). The localizations of tumors were 2 (16.6%) upper, 5 (41.6%) mid and 5 (41.6%) lower pole. The RFA applications included 9 (75%) USG-PRFA, 1 (8.3%) CT-PRFA, 1 (8.3%) T-LRFA and 1 (8.3%) R-LRFA. The mean age was 65.3 ± 8.5 (52-76) years. The mean tumor size was 29.6 ± 6.08 (15-40) mm. No complications related to the RFA were encountered in any of the cases. Failure (residual tumour) was determined in 8.3% (1/12) of USG-RFA application. The success rate was thus 91.7% (11/12). Other 1st, 3rd and 6th months follow-up data revealed no residua and recurrence.

CONCLUSIONS

RFA application appears to be safe as a less invasive and effective treatment modality in selected cases of small renal tumors in individuals with excessive anesthetic and also surgical risk.

Quantification of tissue shrinkage and dehydration caused by microwave ablation: experimental study in kidneys for the estimation of effective coagulation volume

PURPOSE

To quantify the extent of tissue shrinkage and dehydration caused by microwave (MW) ablation in kidneys for estimation of effective coagulation volume.

MATERIALS AND METHODS

MW ablations were carried out in ex vivo porcine kidneys. Six study groups were defined: groups 1A, 2A, and 3A for MW ablation (90 W for 5 min, 7.5 min, or 10 min), and groups 1B, 2B, and 3B for control (without MW ablation). Pre- and postinterventional volume analyses were performed. Effective coagulation volumes (original tissue included in coagulation) were determined. Postinterventional dehydration analyses were performed with calculation of mean mass fractions of water.

RESULTS

Mean deployed energies were 21.6 kJ ± 1.1 for group 1A, 29.9 kJ ± 1.0 for group 2A, and 42.1 kJ ± 0.5 kJ for group 3A, and were significantly different (P < .0001). Differences between pre- and postinterventional volumes were -3.8% ± 0.6 for group 1A, -5.6% ± 0.9 for group 2A, and -7.2% ± 0.4 for group 3A, and -1.1% ± 0.3 for group 1B, -1.8% ± 0.4 for group 2B, and -1.1% ± 0.4 for group 3B. Postinterventional volumes were significantly smaller than preinterventional volumes for all groups (P < .01). Underestimations of effective coagulation volume from visualized coagulation volume were 26.1% ± 3.5 for group 1A, 35.2% ± 11.2 for group 2A, and 42.1% ± 4.9 for group 3A, which were significantly different (P < .01). Mean mass fractions of water were 64.2% ± 1.4 for group 1A, 63.2% ± 1.7 for group 2A, and 62.6% ± 1.8% for group 3A, with significant differences versus corresponding control groups (P < .01).

CONCLUSIONS

For MW ablation in kidneys, underestimation of effective coagulation volume based on visualized coagulation volume is significantly greater with greater deployed energy. Therefore, local dehydration with tissue shrinkage is a potential contributor.

Bipolar versus multipolar radiofrequency (RF) ablation for the treatment of renal cell carcinoma: differences in technical and clinical parameters

PURPOSE

This study aimed to compare retrospectively bipolar RF ablation with multipolar RF ablation for the treatment of renal cell carcinoma.

MATERIALS AND METHODS

Between March 2009 and June 2012, 12 tumours (nine patients) treated with bipolar RF ablation (one applicator) and 14 tumours (11 patients) treated with multipolar RF ablation (two applicators) were compared systematically. Selection between bipolar RF ablation and multipolar RF ablation was operator choice considering tumour size. Study goals included differences in tumour and coagulation extent, and technical parameters (total RF energy delivery and RF ablation time per coagulation volume).

RESULTS

Tumour maximum diameter was significantly larger for multipolar RF ablation compared with bipolar RF ablation (27.0 mm versus 19.4 mm; p < 0.01). This difference is partially dependent on operator choice. Coagulation length, width and volume were significantly larger for multipolar RF ablation compared with bipolar RF ablation (35.0 mm versus 26.5 mm, 27.5 mm versus 23.0 mm and 14.3 cm(3) versus 8.1 cm(3); p < 0.01, p < 0.05 and p < 0.05, respectively). Coagulation circularity was not significantly different between both study groups (0.8 versus 0.8; not significant). Total RF energy delivery was significantly higher and RF ablation time per coagulation volume was significantly shorter for multipolar RF ablation compared with bipolar RF ablation (52.0 kJ versus 28.6 kJ and 2.4 min/cm(3) versus 4.1 min/cm(3); p < 0.05 and p < 0.05, respectively).

CONCLUSIONS

Multipolar RF ablation creates a significantly larger coagulation width, but identical coagulation shape, compared with bipolar RF ablation. Additionally, multipolar RF ablation coagulates faster according to the shorter RF ablation time per coagulation volume.

Microwave ablation in porcine livers applying 5-minute protocols: influence of deployed energy on extent and shape of coagulation

PURPOSE

To evaluate the influence of deployed energy on extent and shape of microwave (MW)-induced coagulation in porcine livers applying 5-minute protocols.

MATERIALS AND METHODS

MW ablations (n = 25) were performed in ex vivo porcine livers (n = 8). Ablation time was 5 minutes. Five study groups were defined, each with different power output: I, 20 W (n = 5); II, 40 W (n = 5); III, 60 W (n = 5); IV, 80 W (n = 5); and V, 105 W (n = 5). Extent and shape of white coagulation was evaluated macroscopically, including short diameter, volume, front margin, coagulation center (distance between center of short diameter of coagulation and applicator tip), and ellipticity index (short diameter/long diameter). Deployed energy was also analyzed.

RESULTS

Short diameter and volume were significantly different (P<.001 and P<.001) between the groups: I, 23.0 mm and 11.1 cm(3); II, 12.4 mm and 12.4 cm(3); III, 27.0 mm and 17.6 cm(3); IV, 31.0 mm and 29.2 cm(3); and V, 35.0 mm and 42.3 cm(3). Front margin and coagulation center were also significantly different (P<.05 and P<.001): I, 6.0 mm and 13.0 mm; II, 8.0 mm and 11.0 mm; III, 8.0 mm and 14.0 mm; IV, 8.0 mm and 18.0 mm; and V, 10.0 mm and 19.0 mm. Ellipticity index was not significantly different. Deployed energy was significantly different (P<.001): I, 5.7 kJ; II, 11.0 kJ; III, 15.5 kJ; IV, 21.6 kJ; and V, 26.6 kJ.

CONCLUSIONS

Extent, but not shape, of MW-induced coagulation depends on the deployed energy. Applying the protocols described in this study, significantly different coagulation volumes can be created with an ablation time of 5 minutes but different power output.

Radiofrequency-induced thermal therapy: results of a European multicentre study of resistive ablation of incompetent truncal varicose veins

OBJECTIVES

To investigate the effectiveness of bipolar radiofrequency-induced thermal therapy (RFITT) in a multicentre non-randomized study.

METHODS

Some 672 incompetent saphenous veins (85% great saphenous varicose vein, 15% short saphenous vein) in 462 patients (56.5% CEAP [clinical, aetiological, anatomical and pathological elements] class 3 or worse) were treated in eight European centres. Patients were assessed between 180 and 360 days postoperatively. Occlusion rates were determined by duplex ultrasound and compared with the power used for treatment, pull back rate and experience of the operating surgeon.

RESULTS

Complete occlusion rates of 98.4% were achieved when treatments were performed by an experienced operator (more than 20 cases), when the maximum power setting on the RFITT generator was between 18 and 20 W and the applicator was withdrawn at a rate slower than 1.5 second/cm

CONCLUSIONS

RFITT is efficacious, well tolerated by patients and has a low incidence of procedure-related post-operative complications.

Multipolar radiofrequency ablation using 4-6 applicators simultaneously: a study in the ex vivo bovine liver

In this study the volume and shape of coagulation zones after multipolar radiofrequency ablation (RFA) with simultaneous use of 4-6 applicators in the ex vivo bovine liver were investigated. The RF-applicators were positioned in 13 different configurations to simulate ablation of large solitary tumors and simultaneous ablation of multiple lesions with 120 kJ of applied energy/session. In total, 110 coagulation zones were induced. Standardized measurements of the volume and shape of the coagulation zones were carried out on magnetic resonance images and statistically analyzed. The coagulation zones induced with solitary applicators and with 2 applicators were imperceptibly small and incomplete, respectively. At 20mm applicator distance, the total ablated volume was significantly larger if all applicators were arranged in a single group compared to placement in 2 distant applicator groups, each consisting of 3 applicators (p=.001). The mean total coagulated volume ranged from immeasurably small (if 6 solitary applicators were applied simultaneously) to 74.7 cc (if 6 applicators at 30 mm distance between neighboring applicators were combined to a single group). Applicator distance, number and positioning array impacted time and shape. The coagulation zones surrounding groups with 4-6 applicators were regularly shaped, homogeneous and completely fused, and the axial diameters were almost constant. In conclusion, multipolar RFA with 4-6 applicators is feasible. The multipolar simultaneous mode should be applied for large and solitary lesions only, small and multiple tumors should be ablated consecutively in standard multipolar mode with up to 3 applicators.

Water-cooled radiofrequency: a neuroablative or a neuromodulatory modality with broader applications?

We report the successful use of water-cooled radiofrequency where more traditional forms of neuroablation—conventional and pulsed radiofrequency—had failed to achieve adequate pain relief. We also discuss the mechanism of neural damage with water cooled radiofrequency and discuss why this technique may have a broader role in the management of a wide array of pain syndromes.

Kidney cancer: energy ablation

PURPOSE OF REVIEW

Solid renal tumours with a diameter 4 cm or less are frequently found during routine radiologic investigations. Since a significant number of patients are elderly and frail, there is a growing interest in effectively treating these patients by minimally invasive energy-ablative surgery.

RECENT FINDINGS

Such tumours may be treated by either freezing (cryoablation) or by heat (radio-frequency ablation or high-intensity focused ultrasound). In addition, percutaneous methods are available, but percutaneous focused ultrasound is not feasible as yet with the technique available. All percutaneous techniques lack effective monitoring of ablation, however, and oncological follow-up commonly relies on radiologic measurements only. Not surprisingly, the effectiveness of all percutaneous procedures is significantly lower, with a high recurrence and re-treatment rate as compared with open or laparoscopic procedures. Long-term results in larger series are missing, but it seems that laparoscopic cryoablation is most effective in respect to oncological results, but requires more technical efforts and surgical skills as compared with radio-frequency ablation or focused ultrasound.

SUMMARY

There is currently no ideal energy-ablative energy source on the horizon, but cryoablation seems to produce the most durable result. Focused ultrasound, however, may have the greatest potential for further developments.

Novel Intradiscal Biacuplasty (IDB) for the Treatment of Lumbar Discogenic Pain

Reported here is the treatment of severe axial discogenic pain in a young man utilizing the new minimally invasive transdiscal radiofrequency technique called intradiscal biacuplasty (Baylis Medical Inc., Montreal, Canada). The new procedure is detailed and step-by-step fluoroscopic imaging presented. There were no intra- and postoperative complications, and significant improvements in patient functional capacity, and pain scores were noted. Visual analog scale pain score decreased from 5 to 1 cm at 6-month follow-up, Oswestry disability scores improved from 14 (28% or moderate disability) to 6 points (12% or minimal disability) and SF-36-PF (physical function) score changed from 67 to 82. Potential advantages of cooled, bipolar radiofrequency to heat the posterior annulus are discussed.