Laser interstitial thermal therapy (LITT) has received increased interest in recent years, especially for treating neurological disorders such as gliomas and epilepsy. In LITT, monitoring tissue temperature is critical. For hyperthermia treatment of tumors, temperature must be controlled between 43 – 45°C to kill cancer cells through apoptosis. Heating tissue to higher temperatures between 50 – 80°C will quickly coagulate the tissue through necrosis. The success of LITT depends on accurate real-time temperature feedback. The advance of magnetic resonance imaging (MRI) thermometry has greatly enabled LITT for neurosurgery. However, the FDA has recently warned that MRI thermometry has a slow response time, which may lead to overtreatment. Here, we report our progress in developing a thermal sensing system based on blackbody radiation in the short-wave infrared range (SWIR, 1 μm – 2.5 μm) through a 2 m silica fiber to monitor temperatures as low as 40°C. In the SWIR range, water absorption and silica fiber attenuation are relatively low, making tissue temperature measurement feasible during LITT. We demonstrate the feasibility of using SWIR blackbody radiation for real-time temperature monitoring through bench-top studies and ex vivo tissue studies. This new thermal sensing technology could be seamlessly integrated with current MRI thermometry to improve response time. It could also be used standalone during LITT for applications when use of MRI thermometry is not feasible.
Laser vaporization is a surgical procedure which utilizes a high power laser to quickly heat and vaporize tissue. Laser vaporization can be conducted on internal organs, such as breast or prostate, through a fiber catheter. Compared with other surgical technologies, it has excellent hemostasis capability with minimal collateral tissue damage, which may reduce hospitalization time and postoperative complications. Accurately monitoring tissue temperature during laser vaporization procedures provides important feedback to surgeons to improve surgical outcomes. Tissue cannot be vaporized if the temperature is lower than the boiling point, while high temperatures may lead to carbonization over the tissue surface, which not only reduces vaporization efficiency but also leads to postsurgical complications. However, until now, no sensing technologies have been developed to monitor tissue temperature during routine laser vaporization in clinics. Here, we report the use of blackbody radiation in the short-wave infrared range (SWIR) for tissue temperature monitoring during laser vaporization. Although blackbody radiation in SWIR is very weak for temperatures less than 100°C, the relatively low water absorption and silica fiber attenuation may allow temperature sensing in vivo. We successfully detected blackbody radiation in SWIR down to 80°C through a 2 m silica fiber. We then proved the feasibility of using blackbody radiation in SWIR to monitor tissue temperature during laser vaporization through an ex vivo tissue study. The developed technology is low-cost and can be seamlessly integrated with the fiber catheter used in laser vaporization.