Rationale and objectives: Laser irradiation therapy in deep tissues requires a monitoring method other than visual guidance. Magnetic resonance imaging (MRI) can be used for this purpose because it visualizes soft tissue structures and heat distribution.
Methods: The authors performed interstitial laser irradiations in rat livers with various laser outputs and measured the sizes of laser-induced lesions. MRI of these lesions was done ex vivo and compared with the histologic findings. Laser-induced lesions also were studied in rabbit brain, liver, and skeletal muscle to show the influences of tissue optical and thermal properties. Imaging of interstitial laser irradiation also was performed in vivo in rabbit brains.
Results: MRI depicted the laser-induced lesions produced with different laser outputs and tissue types. MRIs of rabbit brain in vivo effectively demonstrated the signal decrease during heating and acute tissue changes.
Conclusion: MRI has potential for monitoring interstitial laser surgery or hyperthermia.