Yuichiro Daidoh

Fiber Optic Pulsed Photothermal Radiometry For Urinary Stone Diagnosis

We investigated a fiber-optic infrared radiation diagnosis for in vivo urinary tract tissue discrimination during laser urinary stone fragmentation. Such in vivo analysis may be useful for preventing mis-irradiation to surrounding tissue. Since we plan to use infrared lasers and infrared fibers to the urinary stones photofragmentation, the pulsed photothermal radiometry(PPTR) was employed in this study due to its simplicity and benefit of common use of the infrared laser and fiber to therapy and diagnosis. We successfully demonstrated a discrimination between urinary stones and urinary tract tissue, by a chalcogenide glass fiber-optic CO laser induced PPTR analysis.

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

To minimize urotherial tissue injuries by false laser irradiation during the laser stones fragmentation, a novel fiber-optic analytical system was developed 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 (400 micrometers (phi) ) as an excitation line, an As-S glass fiber (400 micrometers (phi) ) as a detection line, and a thin-fiber endoscope (610 micrometers (phi) ). A urinary stone was introduced into the canine ureter uneter 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.

New technique for prostatectomy using Ho:YAG laser

To develop a new transperineal laser prostatectomy through a biopsy needle, we determined the efficiency of a pulsed Nd:YAG laser irradiation for canine prostate. The Ho:YAG laser ((lambda) equals 2.1 micrometers ) may induced stress-wave to destroy the small vessels in prostate. After the exposure of the canine prostate, it was punctured by the needle. A quartz fiber of which core-diameter was 200 or 400 micrometers was inserted into the 18 G needle. The irradiation fluence was set to 150 - 600 J/cm2 and repetition rate was kept at 2 Hz. The cross-section of the irradiated portion of the prostate extracted immediately after the irradiation showed dark-colored hemorrhage layer around the ablation tract with 1 - 2 mm thickness. Some hemorrhage was histologically seen in stoma and gland in the irradiated prostate. In the case of 150 - 175 J/cm2 in the irradiation fluence, the irradiated portion of the prostate was found in the wedge-shaped area with brown color at one week after the irradiation. The lymphocytes infiltrating into the wedge-shaped zone were found. The wedge- shaped zone spread over the prostate and the change of urethral mucosa was minimum at one month after the irradiation. In the case of 500 - 600 J/cm2 irradiation, the paraurethral cavity was made at one month after the irradiation. The histological examination showed that the hemorrhage and subsequent histological changes may be caused by the laser induced stress-wave rather than thermal effect. Our results suggest that transperineal irradiation of pulsed Ho:YAG might offer an effective treatment for benign prostatic hyperplasia with the minimal damage to the urethral mucosa.

The basic study of ureteral stricture treatment using Ho:YAG laser:

We experimentally evaluated an adaptability of a pulsed Ho:YAG laser for the treatment of urinary tract strictures. The pulsed Ho:YAG laser (fluence:160J/cm2) was used to ablate canine ureter, comparing to a continuous ultraviolet argon (UV Ar) laser(intensity:from 400W/cm2 to 1600W/cm2). The individual laser beams were delivered through a silica glass fiber (0.4mm in core diameter) and vertically irradiated to the canine ureter at the various durations. The ablated ureters were histologically examined and the ablation depths were measured. The ureter wall was sharply ablated by both Ho:YAG laser and UV Ar laser. The thickness of thermally damaged layer by Ho:YAG laser ablation was slightly thinner than by UV Ar laser ablation. However, the Ho:YAG laser ablation efficiency (3.7X10+0.6-5g/J) was smaller than the UV AR laser ablation efficiency (16.7X10+9.5-5g/J). We demonstrated that the both laser ablation was useful for the laser treatment of the urinary tract stricture.

Basic investigation of laser therapy for the ureteral stricture using ultraviolet argon laser and multifiber catheter

In order to develop new, easy, and safe treatment for urinary tract stricture, we investigated the laser plasty using a combination of an uv Ar laser for ablation and a novel multi-fiber catheter for laser delivery. To investigate the characteristics of the uv Ar laser ablation to ureteral tissue, the experiment in vitro was performed. The ureter was clearly ablated with sufficient thin coagulation layer. The proper laser power for the tissue ablation was about 0.5 W for 0.4 mm core-diameter fiber. The multi-fiber catheter (1.6 mm in outer diameter) consisted of 13 pixels of silica glass fibers (0.2 mm in core diameter) for laser delivery and a through lumen (0.9 mm in inner diameter) for guidewire. The catheter was inserted into a canine ureter under the general anesthesia. The ureter and urinary tract were irradiated using about 0.6 W of laser power at the catheter tip with 40s duration. The irradiated urinary tract tissues were histologically investigated. The ureter was ablated up to the submucosa layer. The urinary tract endotherium was eliminated by the laser ablation without the carbonization. No perforation was found at various irradiation conditions. To investigate the ureteral tissue damage of the uv Ar laser irradiation, the serosa temperature was measured by a thermocouple. The temperature elevation of the serosa could be restricted up to 60 degree(s)C, at which the protein was not coagulated. We concluded that the combination of uv Ra laser and multi-fiber catheter offered easy, reliable therapy for coronary structure.

Novel fiber optic pulsed photo-thermal radiometry for transluminal tissue characterization

The use of fiber-optic pulsed photo-thermal radiometry for noncontact diagnostic tissue characterization under transluminal catheterization is described. The method uses a simple time-dependent radiation waveform measurement and shape analysis. It has been applied to urinary tissue characterization and artery disease diagnosis.<<ETX>>