Thoracoscopy-assisted magnetic resonance guided microwave coagulation therapy for hepatic tumors

Subsequent cooling-circulation after radiofrequency and microwave ablation avoids secondary indirect damage induced by residual thermal energy

PURPOSE

We aimed to investigate the exact role of residual thermal energy following microwave ablation (MWA) and radiofrequency ablation (RFA) at the final ablation and transition zones and determine whether residual thermal energy could be dissipated by subsequent cooling-circulation.

METHODS

In an ex vivo study, MWA and RFA were performed on fresh porcine liver, and central and border temperatures were compared. In an in vivo study, MWA and RFA were performed to the livers of New Zealand white rabbits. Tissue samples were stained with α-NADH-diaphorase. The coagulation zones (NADH-negative) and transition zones (lightly NADH-stained) of different groups were compared at different time points.

RESULTS

In the ex vivo model, the residual thermal energy after MWA and RFA could be dispersed by subsequent cooling-circulation due to the temperature decreasing rapidly. In the in vivo study, the coagulation volume in the ablation group was larger than that in the cooling-circulation group (P < 0.05) 2 days after ablation. In the ablation group, the damaged zone (the transition zone plus the coagulation zone) on α-NADH-diaphorase-stained images increased rapidly within 2 hours after ablation and slowly reached the maximum on day 2. However, the damaged zones did not change significantly at the three time points observed in the cooling-circulation group.

CONCLUSION

The residual thermal energy in MWA and RFA induced secondary damage beyond the direct coagulation zone, and it could be dissipated by subsequent cooling-circulation, contributing to smaller ablation and transition zones.

Magnetic resonance and ultrasound image-guided navigation system using a needle manipulator

PURPOSE

Image guidance is crucial for percutaneous tumor ablations, enabling accurate needle-like applicator placement into target tumors while avoiding tissues that are sensitive to injury and/or correcting needle deflection. Although ultrasound (US) is widely used for image guidance, magnetic resonance (MR) is preferable due to its superior soft tissue contrast. The objective of this study was to develop and evaluate an MR and US multi-modal image-guided navigation system with a needle manipulator to enable US-guided applicator placement during MR imaging (MRI)-guided percutaneous tumor ablation.

METHODS

The MRI-compatible needle manipulator with US probe was installed adjacent to a 3 Tesla MRI scanner patient table. Coordinate systems for the MR image, patient table, manipulator, and US probe were all registered using an optical tracking sensor. The patient was initially scanned in the MRI scanner bore for planning and then moved outside the bore for treatment. Needle insertion was guided by real-time US imaging fused with the reformatted static MR image to enhance soft tissue contrast. Feasibility, targeting accuracy, and MR compatibility of the system were evaluated using a bovine liver and agar phantoms.

RESULTS

Targeting error for 50 needle insertions was 1.6 ± 0.6 mm (mean ± standard deviation). The experiment confirmed that fused MR and US images provided real-time needle localization against static MR images with soft tissue contrast.

CONCLUSIONS

The proposed MR and US multi-modal image-guided navigation system using a needle manipulator enabled accurate needle insertion by taking advantage of static MR and real-time US images simultaneously. Real-time visualization helped determine needle depth, tissue monitoring surrounding the needle path, target organ shifts, and needle deviation from the path.

CT-Guided Percutaneous Microwave Ablation of Tumors in the Hepatic Dome: Assessment of Efficacy and Safety

PURPOSE

To evaluate the technique, efficacy, safety, and clinical outcomes of CT-guided microwave ablation of tumors in the hepatic dome.

MATERIALS AND METHODS

Retrospective review was conducted of 46 consecutive patients (31 men and 15 women; mean age, 64 y) treated with CT-guided microwave ablation for hepatic-dome tumors between June 2011 and December 2014. Baseline demographics of sex, tumor diagnosis, tumor location, tumor size, and technical details were recorded. Technical success was evaluated. Treatment response was assessed per European Association for the Study of the Liver criteria. Overall success and overall survival were calculated, and complications were recorded.

RESULTS

Forty-eight tumors were treated. Tumor locations included segments VIII (n = 32), VII (n = 10), and VIa (n = 6). Mean tumor size was 2.4 cm (range, 0.9-5.2 cm). Thirty-four tumors (70%) were treated following creation of artificial ascites with 0.9% normal saline solution (mean volume, 1,237 mL; range, 300-3,000 mL). The technical success rate was 100%, and the complete response rate was 94%. Overall survival rate was 73.9% over 24.7 months of follow-up. There were no major complications. Two patients experienced small, asymptomatic pneumothoraces that were aspirated at the time of the procedure and required no further treatment.

CONCLUSIONS

CT-guided microwave ablation of tumors in the hepatic dome is associated with a high technical success rate, high complete response rate, and low complication rate.

Minimally invasive surgery using the open magnetic resonance imaging system combined with video-assisted thoracoscopic surgery for synchronous hepatic and pulmonary metastases from colorectal cancer: report of four cases

Simultaneous resection of hepatic and pulmonary metastases (HPM) from colorectal cancer (CRC) has been reported to be effective, but it is also considered invasive. We report the preliminary results of performing minimally invasive surgery using the open magnetic resonance (MR) imaging system to resect synchronous HPM from CRC in four patients. All four patients were referred for thoracoscopy-assisted interventional MR-guided microwave coagulation therapy (T-IVMR-MCT) combined with video-assisted thoracoscopic surgery (VATS). The median diameters of the HPM were 18.2 and 23.2 mm, respectively. The median duration of VATS and T-IVMR-MCT was 82.5 and 139 min, respectively. All patients were discharged without any major postoperative complications. One patient was still free of disease at 24 months and the others died of disease progression 13, 36, and 47 months without evidence of recurrence in the treated area. Thus, simultaneous VATS + T-IVMR-MCT appears to be an effective option as a minimally invasive treatment for synchronous HPM from CRC.

Microwave ablation of giant hepatic cavernous hemangiomas

PURPOSE

This study was designed to explore the safety and efficacy of percutaneous microwave (MW) ablation as an alternative treatment for symptomatic giant hepatic hemangiomas.

METHODS

Patients (n = 7; 6 females, 1 male; mean age = 44 years) with symptomatic, giant hemangiomas (n = 8) were treated with ultrasound-guided percutaneous MW ablation and followed for a mean of 18 months. Patient pain was recorded both before and after the procedure according to the 10-point visual analog scale. All patients were treated using one or three gas-cooled 17-gauge antennas powered by a 2.4-GHz generator (Neuwave Medical, Madison, WI). Mean ablation time was 11.6 min. Four patients received hydrodissection to protect the abdominal wall, colon, or gallbladder (5 % dextrose in water, mean volume 900 mL). Immediate postablation biphasic CT of the abdomen was performed, and four of seven patients have undergone delayed follow-up imaging.

RESULTS

All ablations were technically successful with no major or minor complications. Average pain score decreased from 4.6 to 0.9 (p < 0.05), and six of seven patients report resolution or improvement of symptoms at 18-month average follow-up (range 1-33 months). Immediately postablation, mean tumor diameter decreased 25 % (from 7.3 to 5.5 cm, p < 0.05) and volume decreased 62 % (from 301 to 113 cm(3), p < 0.05).

DISCUSSION

In this series, percutaneous MW ablation was safe, well-tolerated, and effective in markedly shrinking large hepatic hemangiomas and improving symptoms in most patients.

Microwave ablation of hepatic malignancy

Microwave ablation is an extremely promising heat-based thermal ablation modality that has particular applicability in treating hepatic malignancies. Microwaves can generate very high temperatures in very short time periods, potentially leading to improved treatment efficiency and larger ablation zones. As the available technology continues to improve, microwave ablation is emerging as a valuable alternative to radiofrequency ablation in the treatment of hepatic malignancies. This article reviews the current state of microwave ablation including technical and clinical considerations.

Evolving ablative therapies for hepatic malignancy

The liver is a common site for both primary and secondary malignancy. Hepatic resection and transplantation are the two treatment modalities that have been shown to achieve complete cure, but only 10 to 20% of patients are candidates for these treatments. For the remaining patients, tumor ablation has emerged as the most promising alternative modality. In addition to providing local control and improving survival outcomes, tumor ablation also helps to down stage patients for potential curative treatments, both alone as well as in combination with other treatments. While tumor ablation can be achieved in multiple ways, the introduction of newer ablative techniques has shifted the focus from palliation to potentially curative treatment. Because the long-term safety and survival benefits are not substantive at present, it is important that we strive to evaluate the results from these studies using appropriate comparative outcome methodologies.

Percutaneous microwave coagulation for eradication of VX2 tumors subcutaneously in rabbits

BACKGROUND

Percutaneous microwave coagulation (PMC) has been accepted as a promising modality in the treatment of tumors in well-vascularized tissues such as liver tumors and hysteromyoma. However, PMC for treatment of tumors in low blood-flow tissues has been seldom reported. The aim of this study was to determine the feasibility and safety of PMC for the treatment of tumors in low blood-flow tissues in a rabbit model.

METHODS

Fifteen rabbits with VX2 tumors implanted subcutaneously underneath the right second nipple were divided into a PMC group (n = 9) and a control group (n = 6). PMC was performed with output power of 40 W for one to two minutes. The therapeutic efficacy was evaluated by magnetic resonance imaging (MRI), physical examinations, survival rate, and histology. The cosmetic outcome after PMC was also assessed.

RESULTS

In the PMC group, tumor eradication was achieved in six rabbits (66.7%) without any evidence of tumor recurrence and metastasis as proven by MRI and histological examinations. The mean greatest and shortest tumor diameters of these six rabbits were 1.83 and 1.33 cm, respectively. Slight epidermal burns, which proved reversible, were found in seven rabbits (77.8%). The PMC group had a significantly longer survival than those in the control group (P = 0.0097). The four rabbits with coagulated tumors survived more than three months with their tumors becoming nonpalpable and undetectable by MRI and histological examinations.

CONCLUSIONS

PMC is feasible and safe in the treatment of tumors in low blood-flow tissues in a rabbit model. Attention should be paid to avoid skin burns with PMC.

US-guided percutaneous microwave coagulation of small breast cancers: a clinical study

PURPOSE

To determine the feasibility of percutaneous microwave coagulation (PMC) for the treatment of small solitary breast cancers.

MATERIALS AND METHODS

With approval of the institutional ethics committee and written informed consent, 41 patients with core-needle-biopsy-proved breast cancers 3.0 cm or less in diameter accessed by using ultrasonography (US) were recruited. US-guided PMC was performed with general anesthesia, followed immediately by mastectomy. Histochemical staining with α-nicotinamide adenine dinucleotide, reduced (NADH)-diaphorase was used to determine cell viability and the extent of PMC lesions.

RESULTS

The mean tumor volume was 5.26 cm(3) ± 3.80 (standard deviation), with a range from 0.09 to 14.14 cm(3). PMC was successfully performed in all cases, with complete tumor ablation as assessed by using US. The mean time to reach complete ablation was 4.48 minutes, ranging from 3 to 10 minutes. With microscopic examination, 37 of 41 cases (90%; 95% confidence interval [CI]: 76.9%, 97.3%) showed complete tumor coagulation, as observed by using α-NADH-diaphorase staining. Of 38 cases diagnosed with invasive ductal carcinoma, 36 cases (95%; 95% CI: 82.3%, 99.4%) showed complete tumor coagulation. Slight thermal injuries to the skin and pectoralis major muscle, which proved reversible, were found in three cases.

CONCLUSION

US-guided PMC of small solitary breast cancers is feasible. Nevertheless, larger-scale clinical trials are still needed to validate PMC for adoption into a standard clinical practice.

Sonography-guided percutaneous microwave ablation of intrahepatic primary cholangiocarcinoma

OBJECTIVE

To evaluate the efficacy and safety of sonography-guided percutaneous microwave ablation of intrahepatic primary cholangiocarcinoma.

MATERIALS AND METHODS

From May 2006 to March 2010, 15 patients (11 men, 4 women; mean age, 57.4 years) with 24 histologically proven intrahepatic primary cholangiocarcinoma lesions (mean tumor size, 3.2±1.9 cm; range, 1.3-9.9 cm) were treated with microwave ablation.

RESULTS

Thirty-eight sessions were performed for 24 nodules in 15 patients. The follow-up period was 4-31 months (mean, 12.8±8.0 months). The ablation success rate, the technique effectiveness rate, and the local tumor progression rate were 91.7% (22/24), 87.5% (21/24), and 25% (6/24) respectively according to the results of follow-up. The cumulative overall 6, 12, 24 month survival rates were 78.8%, 60.0%, and 60.0%, respectively. Major complication occurred including liver abscess in two patients (13.3%) and needle seeding in one patient (6.7%). Both complications were cured satisfied with antibiotic treatment combined to catheter drainage for abscess and resection for needle seeding. The minor complications and side effects were experienced by most patients which subsided with supportive treatment.

CONCLUSION

Microwave ablation can be used as a safe and effective technique to treat intrahepatic primary cholangiocarcinoma.

Laparoscopic radiofrequency ablation of liver tumors: comparison of MR guidance versus conventional laparoscopic ultrasound for needle positioning in a phantom model

Laparoscopic radiofrequency ablation (LapRFA) is an established procedure for liver tumors in patients who are unsuitable for resection. A novel technique of magnetic resonance (MR) guided needle positioning during LapRFA was developed and compared to conventional ultrasound (US) guidance in a phantom model. MR-guided procedures were conducted in a 1.0 tesla high field open MR using an MR compatible endoscope and camera. The ultrasound-guided procedure was performed with a clinically established laparoscopy setup and a 2D laparoscopic US probe. During both techniques an identical monopolar non-ferromagnetic RFA needle and a silicon-based phantom model were applied. Finally needle positioning was performed by two surgeons and one interventionalist. Time to needle placement and number of trials were recorded and statistically analyzed. MR-guided needle positioning under laparoscopic control was technically feasible. Average time to correct needle placement was 2' 6″ in the LapUS group and 1' 54″ in the MR group. The number of trials was 3.2 in the LapUS group and 2.6 in the MR group. Image quality was assessed by all participants. MR images showed a better tissue to tumor contrast and allowed an improved orientation due to multiplanar visualization. MR-guided laparoscopic RFA is a promising technique offering multiplanar needle positioning with high soft tissue contrast with immediate therapy control. In a phantom model it showed comparable results regarding needle positioning to the established technique of laparoscopic US guidance.

Microwave tumor ablation: mechanism of action, clinical results, and devices

Microwave ablation uses dielectric hysteresis to produce direct volume heating of tissue. Microwaves are capable of propagating through many tissue types, even those with high impedance such as lung or bone, with less susceptibility to "heat-sink" effects along vessels. Microwaves are highly conducive to the use of multiple applicators, showing the synergy seen with other energies, but also the potential capability for phasing of the electromagnetic field. As a result, larger, more customizable ablation zones may be created in less time. Although multiple microwave ablation systems are currently available, further study and continued development are needed.

Real-time magnetic resonance-guided microwave coagulation therapy for pelvic recurrence of rectal cancer: initial clinical experience using a 0.5 T open magnetic resonance system

PURPOSE

This study aims to evaluate consecutive cases of recurrent rectal cancer in the pelvic cavity treated with microwave coagulation therapy using real-time navigation by an open magnetic resonance system.

METHODS

Nine recurrent pelvic lesions in 8 patients after curative resection of rectal cancer were treated with real-time magnetic resonance-guided microwave coagulation therapy as a palliative local therapy to reduce tumor volume and/or local pain. Clinical and pathological data were collected retrospectively by reviewing medical records and clinical imaging results.

RESULTS

Seven patients received other treatments before real-time magnetic resonance-guided microwave coagulation. Six patients had distant synchronous metastases. Three patients underwent surgery under lumbar anesthesia. Microwave coagulation was performed percutaneously in 5 lesions and under laparotomy in 4 lesions. Although adverse events related to microwave coagulation (skin necrosis and nerve injury) were observed, no fatal complications occurred. Local re-recurrence was observed in 2 of 9 ablated lesions. Except for 1 patient who died of chronic renal failure, the remaining 7 patients died of cancer. Median overall survival after microwave coagulation for all patients was 10 months (range, 4-37 mo). Median overall survival after discovery of pelvic recurrence in all patients was 22 months (range, 9-42 mo).

CONCLUSIONS

The benefits of using an open magnetic resonance system in the pelvic cavity include the abilities to treat tumors that cannot be visualized by other modalities, to demonstrate internal architectural changes during treatment, to differentiate treated vs untreated areas, and to allow adjustments to the treatment plan during the procedure. Additional studies are required to clarify the efficacy of tumor coagulation for local control.

Microwave tissue ablation: biophysics, technology, and applications

Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias, and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control, and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article reviews the basic biophysics of microwave tissue heating, provides an overview of the design and operation of current equipment, and outlines areas for future research.

Microwave coagulation therapy for hepatic tumors: review of the literature and critical analysis

BACKGROUND

Surgical resection of malignant hepatic tumors has been demonstrated to increase overall survival; however, the majority of patients are not candidates for resection. For patients with unresectable tumors, various chemical and thermal ablation modalities have been developed. microwave coagulation therapy (MCT) is one such thermal ablation modality and the purpose of this review is to evaluate the presently available data for MCT and assess the level of evidence to support its clinical use.

METHODS

This review is limited to published studies in the English literature including at least 30 patients per study with MCT for hepatocellular cancer (HCC) or colorectal hepatic metastasis (CRHM). Patterns of local recurrence, complications and survival outcome of MCT ablation are presented and discussed including assessment of Asian experience using the 2.4GHZ device and American experience using the 914MHZ device.

CONCLUSIONS

Although randomized controlled trials comparing RFA and MCT for hepatic ablation are lacking, our review (based on level 2 data) supports that MCT may be optimal when larger necrosis zones and/or ablation of multiple lesions are the objectives. The data support that the potential procedural advantage(s) noted for ablation of CRHM and HCC >3cm, is not supported for HCC <3cm; moreover MCT shares with all other ablation modalities a high rate of locoregional recurrence in HCC; likely due to the multicentricity of this disease process.

Interventional cardiovascular magnetic resonance: still tantalizing

The often touted advantages of MR guidance remain largely unrealized for cardiovascular interventional procedures in patients. Many procedures have been simulated in animal models. We argue these opportunities for clinical interventional MR will be met in the near future. This paper reviews technical and clinical considerations and offers advice on how to implement a clinical-grade interventional cardiovascular MR (iCMR) laboratory. We caution that this reflects our personal view of the "state of the art."