Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Brain Tumors

Lasers were invented in the middle of the 20th century, from the previous theoretical work of Einstein on the process of amplification of stimulated emission, and quickly became used in various devices for industrial, telecommunication and military applications. In the medical field, neurosurgeons were some of the first researchers to investigate the use of lasers for therapy in the 1960s, but were limited by cumbersome designs and the availability of lasers that could only operate in pulsed modes. As improved laser designs were introduced that allowed for continuous mode operation and other wavelengths, new medical techniques were developed and improved. Subsequently, in the early 1970s, Sutton introduced the concept of interstitial hyperthermia, which led to the development of a new technique called laser interstitial thermotherapy (LITT). LITT treatments consist of heating tumors with prolonged and moderate temperature elevations, inducing alteration of cell membranes and enzyme denaturation, leading to the formation of a selective zone of coagulation necrosis in the heated tissue without vaporization. The Nd-YAG and diode laser are the most frequent lasers used for LITT due to their optimum wavelength for absorption and heating in tissue. With the recent development and widespread availability of magnetic resonance imaging (MRI), laser fibers can be inserted stereotactically within the tumor and the treatment can be controlled in real-time. MR imaging allows for monitoring of the temperature elevation in the treated area and for prediction of the extent of induced necrosis based on the temperature history. Several clinical studies have been performed that show that the technique is now safe and allows for control of brain tumors metastases for which traditional treatments including radiosurgery have failed. Additional technical progress is now being performed on methods to treat tumors with larger diameters and with more complex shapes. Lastly, additional clinical studies are needed in larger patient populations to confirm the findings of the initial clinical trials.