Discrimination between urinary tract tissue and urinary stones by fiber optic pulsed photo-thermal radiometry method in vivo

To minimize urotherial tissue injuries by false laser irradiation during the laser stones fragmentation, we developed a novel fiber-optic analytical system which was able to distinguish urotherial tissues from urinary stones in vivo. This system was composed of the fiber-optic pulsed photo-thermal radiometry (PPTR) system together with a thin-fiber endoscope. The ultraviolet Ar laser was employed as the excitation light source. The catheter of this system was 6F in diameter and consisted of SiO₂ glass fiber (400μmφ) as an excitation line, an As-S glass fiber (400μmφ) as a detection line, and a thin-fiber endoscope (610μmφ). A urinary stone was introduced into the canine ureter under general anesthesia. The catheter system was inserted through an opening of the ureter distal to the stone. The e-folding decay time of the PPTR waveform of which optical and/or thermal properties of the tissues and stones were characterized was measured in vivo. The e-folding decay times were significantly different between urinary stones and the canine ureter. These results suggest that the fiber-optic PPTR analysis might be significantly useful procedure to prevent urotherial tissue from false irradiation injuries in clinical laser stone fragmentation.