Overview of NanoKnife Technology

Irreversible Electroporation (IRE), also known as NanoKnife, is an emerging ablation therapy. It uses steep pulsed direct currents between electrodes to create irreversible "nanoscale" pores in the cell membrane. This disrupts cellular homeostasis and induces apoptosis in targeted cells.

Advantages of NanoKnife Technology

Compared to traditional thermal ablation, IRE has the following advantages:

1. Selective Action: IRE selectively targets the lipid bilayer of cell membranes, sparing fibrous structures such as blood vessels, bile ducts, and nerves that lack lipid bilayers.
2. Temperature Independence: IRE destroys tumor cells without relying on temperature, avoiding the "heat sink effect" and improving the complete ablation rate around vascular tumors.
3. Minimized Damage: IRE electrodes are thin, causing minimal puncture trauma with a lower complication rate than thermal ablation.
4. Immune Activation: IRE induces apoptosis rather than necrosis, preserving tumor antigens and activating host anti-tumor immunity. Combined with immunotherapy, it has potential for long-term efficacy improvements.

Indications and Contraindications

Indications

1. Clinically or pathologically confirmed malignant liver tumors:
   • Single tumor ≤5 cm in diameter.
   • Multiple tumors (up to 3 lesions), each ≤3 cm in diameter.
2. Tumors adjacent to critical structures such as the hepatic hilum, blood vessels, bile ducts, diaphragm, or gastrointestinal tract.
3. Liver function classified as Child-Pugh A/B.
4. Unresectable tumors >5 cm (single) or >3 cm (multiple) suitable for palliative ablation or combination therapies.
5. Expected survival >3 months and Karnofsky Performance Status (KPS) >50.

Contraindications

1. Poor general condition (ECOG >2) or severe dysfunction of vital organs (heart, lung, brain, liver, kidneys).
2. Child-Pugh class C liver function that cannot be improved with supportive care.
3. Tumors with main portal vein or hepatic vein thrombosis.
4. Tumors located on the liver's external surface, with >1/3 exposed.
5. Active infections, particularly biliary system infections.
6. Uncorrectable coagulopathy.
7. History of pacemaker implantation.
8. History of epilepsy or severe arrhythmias, or recent (within 6 months) major myocardial infarction.

Preoperative Evaluation

1. Conduct a detailed medical history review and comprehensive physical examination to assess the patient's overall condition and tolerance for surgery and anesthesia.
2. Complete imaging studies, including contrast-enhanced CT or MRI of the abdomen, and ultrasound with contrast to determine the lesion’s relationship with nearby structures such as blood vessels and bile ducts.
3. Perform routine preoperative tests: ECG, chest CT, pulmonary function tests, echocardiography, complete blood count, biochemical tests, coagulation profile, tumor markers, and myocardial enzymes.

IRE Ablation for Liver Cancer: Procedure Overview

Anesthesia Management

IRE ablation requires endotracheal general anesthesia with deep muscle relaxation. Continuous invasive blood pressure and ECG monitoring are recommended to ensure precise hemodynamic control.

Guidance Methods

IRE is commonly performed via percutaneous, laparoscopic, or open surgery. Among these, percutaneous IRE with imaging guidance is preferred for its simplicity, minimal invasiveness, and precision. Common imaging methods include CT, ultrasound, and MRI. However, due to the time-consuming nature of MRI, CT and ultrasound are predominantly used.

Procedure Workflow

1. Puncture Positioning and Needle Selection

   • Determine the target lesion’s number, size, shape, margins, blood supply, and proximity to critical structures using preoperative CT/MRI and ultrasound.
   • Choose the optimal puncture position and patient posture to facilitate anesthesia and ensure clear ultrasound-guided access.

2. Designing the Needle Placement Plan

   • Develop a plan for the number, direction, and depth of electrode needle placements.
   • Ensure parallel alignment and consistent depth of electrodes. The ablation area lies between two parallel electrodes and should fully cover the tumor and a 0.5 cm margin for curative treatment.

3. Auxiliary Techniques

   • For lesions obscured by air in the lungs, artificial ascites or thoracic fluid can enhance visibility.
   • Fusion imaging technology can improve needle placement accuracy and reduce complications for lesions poorly visualized with conventional ultrasound.

4. Anesthesia, Sterilization, and Draping

   • After successful anesthesia, position the patient and sterilize the puncture area using iodine. Drape the area with sterile sheets, exposing the operative site.

5. IRE Ablation

   • Under ultrasound guidance, place electrodes accurately according to the plan. Set ablation parameters based on the device instructions.

Postoperative Management

1. Closely monitor the patient's vital signs, including blood pressure, oxygen saturation, and heart rate.
2. Maintain bed rest and fasting for 6 hours. For tumors near the intestine, extend fasting duration as needed.
3. Perform follow-up tests on liver and kidney function, complete blood count, and imaging (ultrasound with contrast, CT, or MRI) within 3–7 days.
4. Provide appropriate fluid replacement, symptomatic treatment, and antibiotics or anticoagulants as necessary.