Microprocessor-controlled Nd:YAG laser for hyperthermia induction in the RIF-1 tumor

Area of Science:

• Oncology
• Biomedical Engineering
• Laser Medicine

Background:

• Hyperthermia, the therapeutic use of heat, is an established cancer treatment modality.
• Near-infrared laser technology offers precise energy delivery for localized hyperthermia.
• Effective temperature monitoring and control are critical for successful hyperthermia outcomes.

Purpose of the Study:

• To evaluate the efficacy of interstitial versus superficial near-infrared laser-induced hyperthermia in a murine tumor model.
• To assess temperature distribution and control during laser-induced hyperthermia treatments.
• To correlate treatment parameters with tumor response and side effects.

Main Methods:

• RIF-1 tumors in C3H male mice were treated with 1,064 nm Nd:YAG laser radiation.
• Hyperthermia was delivered interstitially or superficially using a quartz fiber with a diffuser or microlens.
• Tumor temperatures were controlled via a feedback thermocouple to maintain 42-45°C for 30 minutes, with a second thermocouple monitoring temperature distribution.

Main Results:

• Excellent temperature control (±0.2°C) was achieved at the feedback thermocouple.
• Significant temperature discrepancies were observed at the second thermocouple (up to -2.3°C or +4.6°C).
• Superficial treatment resulted in statistically significant improvements in tumor growth delay and increased skin necrosis compared to interstitial treatment.

Conclusions:

• Superficial laser-induced hyperthermia demonstrates superior efficacy over interstitial application for RIF-1 tumors in mice.
• Precise temperature monitoring is essential, but spatial temperature variations necessitate careful consideration of delivery methods.
• Laser-based hyperthermia presents a promising approach for localized cancer treatment, warranting further investigation into optimal delivery techniques.