Temperature control and light penetration in a feedback interstitial laser thermotherapy system

Area of Science:

• Oncology
• Medical Engineering
• Laser Medicine

Background:

• Interstitial laser thermotherapy (ILT) offers targeted tumor treatment.
• Effective ILT requires precise temperature control and predictable energy delivery.
• Closed-loop systems integrating temperature feedback show promise for ILT.

Purpose of the Study:

• To evaluate a closed-loop interstitial laser thermotherapy system in processed liver tissue.
• To demonstrate the system's efficacy in treating a vascularized liver tumor in vivo.
• To analyze the impact of laser power and carbonization on temperature distribution and system performance.

Main Methods:

• Utilized an Nd:YAG laser with a temperature feedback circuit and thermistor probes.
• Performed experiments in processed liver using a sapphire probe at varying power outputs (1-5 W).
• Treated implanted adenocarcinoma in rat liver at 2 W, with feedback probes placed 3 mm from tumor margin.

Main Results:

• Optimal temperature control and minimal carbonization observed at 1-3 W in vitro.
• Higher power (4-5 W) led to carbonization, impaired light penetration, and temperature control issues.
• Successful in-vivo tumor eradication was achieved at 2 W with preserved temperature control and light penetration.

Conclusions:

• Closed-loop feedback systems enable stable and reproducible local hyperthermia.
• Avoiding carbonization and preserving light penetration enhances ILT system performance.
• This system demonstrates significant potential for interstitial thermotherapy of malignant tumors.