Koji Sensaki

Investigation of possible mechanism of laser welding between artificial film and bronchial tissue

The mechanism of laser welding between artificial film and airway epithelium was investigated. An expanded-polytetrafluoroethylene (e-PTFE) patch (200 micrometers in thickness) was welded to exised canine trachea using carbon monoxide laser (wavelength 5.4 micrometers ) with contact irradiation method. The power density at the tip of the laser fiber cable was 300 W/cm2 and irradiation time was five seconds. This method was designed for closure of a postoperative bronchopleural fistula via a bronchoscope using laser tissue welding. The welded contact surfaces of the patch and the tissue were examined with scanning electron microscope. The surface of e-PTFE showed porous structure. And welded surface of the tissue revealed multiple process. The porous structure of the e-PTFE patch and process of the tracheal epithelium coincided with size. The evidence of its remodeling as cast of the patch surface proved. Strings of e-PTFE fibrils were also recognized among the process. The mechanical anchoring effect was considered as a possible mechanism of laser patch welding of e-PTFE and bronchial epithelium.

Infrared glass fiber cables for CO laser medical applications

We developed the medical fiber cables which were designed for CO laser therapy, i.e., angioplasty and endoscopic therapy. As-S chalcogenide glass fibers were used for CO laser delivery. A 230 micrometers core-diameter fiber was used for the angioplasty laser cable. The outer diameter of this cable was 600 micrometers . The total length and insertion length of the angioplasty laser cable were 2.5 m and 1.0 m, respectively. Typically, 2.0 W of fiber output was used in the animal experiment in vivo for the ablation of the model plaque which consisted of human atheromatous aorta wall. The transmission of the angioplasty laser cable was approximately 35%, because the reflection loss occurred at both ends of the fiber and window. Meanwhile, the core diameter of the energy delivery fiber for the endoscopic therapy was 450 micrometers . The outer diameter of this cable was 1.7 mm. Approximately 4.5 W of fiber output was used for clinical treatment of pneumothorax through a pneumoscope. Both types of the cables had the ultra-thin thermocouples for temperature monitoring at the tip of the cables. This temperature monitoring was extremely useful to prevent the thermal destruction of the fiber tip. Moreover, the As-S glass fibers were completely sealed by the CaF2 windows and outer tubes. Therefore, these cables were considered to have sufficient safety properties for medical applications. These laser cables were successfully used for the in vivo animal experiments and/or actual clinical therapies.

Thoracoscopic CO laser coagulation shrinkage of blebs in treatment of spontaneous pneumothorax

Spontaneous pneumothorax is a common disease in young people. Operative intervention has been done in most of the recurrent cases. Recently thoracoscopic treatment has been tested as a less invasive treatment modarity. We adopted carbon monoxide (CO) laser for thoracoscopic treatment of recurrent spontaneous pneumothorax. CO laser (wavelength; 5.4 micrometers ) could be delivered by chalcogenide glass (As - S) covered with a teflon sheath and ZnSe fiber tip. The sterilized flexible bronchoscope was inserted through the thoracoscopic outer sheath under local anesthesia. Shrinkage of blebs was obtained by non-contact method of CO laser irradiation. Laser power at the tip was 2.5 - 5 W and irradiation duration was 0.5 s each. Excellent shrinkage of bleb and bulla could be obtained by CO laser without perforation complication. Advantages of CO laser as a thoracoscopic treatment were: (1) capability of fiber delivery (flexible thoracoscopy was easy to operate and clear to visualize the blebs which were frequently found at the apical portion of the lung, and (2) shallow extinction length (good shrinkage of blebs, low risk of perforation, and thin layer of carbonization). In conclusion, our new technique of thoracoscopic CO laser irradiation was found to be a safe and effective treatment of spontaneous pneumothorax.

Focal positivity of immunohistochemical markers for pulmonary squamous cell carcinoma in primary pulmonary choriocarcinoma: A histopathological study

Cytokeratin 5/6 (CK5/6), p63, and p40 are commonly used as immunohistochemical markers for squamous cell carcinoma (SqCC) of the lung. To elucidate their positivity in primary pulmonary choriocarcinoma (PPC), the present study examined 4 PPCs, including 1 surgically removed PPC and 3 postmortem PPCs. All PPCs consisted of nested cytotrophoblastic tumor cells and occasional syncytiotrophoblastic tumor cells although 1 surgically removed PPC was markedly affected by pre-operative therapy-associated necrosis and 3 postmortem PPCs coexisted with adenocarcinoma. In 1 surgical case, a pre-operative biopsy specimen of PPC contained a few polygonal tumor cells, which mimicked SqCC and exhibited focal p40+ features. Nuclear p63+ and p40+ features of cytotrophoblast-like polygonal tumor cells were focally observed in 3 PPCs (75%) and 2 PPCs (50%), respectively. CK5/6+ trophoblastic tumor cells were focally identified in 1 PPC. Additionally, in 2 other PPCs, CK5/6+ tumor cells were scattered in choriocarcinomatous areas, but possible intermingling of CK5/6+ adenocarcinoma cells could not be ruled out. The results emphasized that PPCs could mimic SqCC morphologically and immunohistochemically, although PPC was an extremely rare neoplasm. Surgical pathologists should be aware of this diagnostic pitfall when encountering a few squamous marker-positive polygonal tumor cells within hemorrhagic necrotic biopsy specimens from lung tumors.

Effect of low-power laser on wound healing at the site of tracheal anastomosis in rats

The effect of low power laser on the wound healing process was investigated at the site of anastomosis in rats. Tracheal reconstruction was performed after the tracheal transection and He-Ne laser (NEC,GLG5360, wavelength 632.8 nm)(3.3 X 10-3 W/cm2, 5 min) was irradiated to the site of anastomosis. Structural and functional recoveries were evaluated at 1 and 2 weeks postoperatively. Hydroxyproline content, epithelial condition, cellular infiltration, fiber proliferation, microstructure of cilia, mucociliary function and neovascularization were measured. Hydroxyproline was measured with Amino acid autoanalyzer (Hitachi 835-50). Microstructure of cilia was observed with scanning electron microscope (JSN-840, JEOL). Mucociliary function was evaluated by India ink movement. The hydroxyproline contents per 1 mg dry weight in irradiated group and control group were equivalent (approximately 20 (mu) g). Cellular infiltration of irradiated group was fewer than that of control group. The degree of mucociliary functional recovery in the irradiated group was better than that of control group. Among the cases that showed the structural recovery of cilia, the functional recovery was observed in whole irradiated group, and in 40% of control group. Neovascularization was more pronounced in irradiated group. From this study it is suggested that the laser irradiation may reduce the inflammation and promote the recovery of mucociliary function at the site of anastomosis.