Michail M. Pankratov

Autofluorescence characteristics of oral mucosa

The fluorescence characteristics of tissues depend upon their biochemical composition and histomorphological architecture, both of which undergo a change during malignant transformation. These changes are detectable as an alteration in the fluorescence spectral profile of the tissues.

Sinus Surgery: Does Mitomycin C Reduce Stenosis?

This experimental study investigates the effect of mitomycin C (MMC) on sinus mucosal healing. MMC has an antiproliferative action on fibroblasts. It is used in glaucoma surgery to prevent restenosis of fistulas. Antrostomies were drilled in rabbit maxillary sinuses. One side was used as a control and the other treated with MMC at a concentration of 0.04, 0.4, or 1 mg/mL. Two animals from each group were sacrificed at 1, 2, 4, and 12 weeks. The antrostomies in the control and 0.04‐mg/mL groups had closed by 1 week; in the 0.4‐mg/mL group by 4 weeks, and in the 1.0‐mg/mL group by 12 weeks. Ciliary function was initially impaired but normalized within 1 week. Both light and scanning electron microscopy showed no permanent damage to the cilia. These results suggest that MMC can be used to delay closure of antrostomies in sinus surgery.

Holmium: Yttrium aluminum garnet laser‐assisted endoscopic sinus surgery: Laboratory experience

Endoscopic sinus surgery using a holmium: yttrium aluminum garnet pulsed solid-state laser oscillating at 2.1 μm with fiberoptic delivery was performed in the laboratory, and the results were compared with those of conventional endoscopic sinus surgery. Three beagle dogs, six human cadaver heads, and one calf head were used in the in vivo and in vitro studies to evaluate the bone ablation, tissue coagulation, and hemostatic properties of the holmium: yttrium aluminum garnet laser. Modified endoscopic telescopes for sinus surgery, a newly developed handpiece for fiberoptic delivery, and other surgical instruments were used

Transtympanic endoscopy of the middle ear

Modern optical technology has made available fiberoptic and rigid endoscopes with diameters of 2 mm and less with acceptable resolution. Endoscopes of small caliber were introduced through a strategically placed myringotomy or an existing perforation to perform exploration of the middle ear as an in‐the‐office procedure. This technique is now routinely used as an adjunct in the diagnostic evaluation of patients with suspected middle ear conditions. Exploratory surgery of the middle ear may be avoided or definitive procedures may be planned better based on endoscopic findings.

Endoscopic Laser-Assisted Reshaping of Collapsed Tracheal Cartilage a Laboratory Study

Repair of anterior tracheal wall collapse is a common and troublesome problem encountered by the head and neck surgeon. The standard treatment calls for an open procedure with or without stenting, depending on the extent of the damage. To avoid the morbidity of the open procedure, a new concept of endoscopic cartilage reshaping was investigated in a laboratory animal study. It involved the application of a 1.44-μm pulsed neodymium:yttrium-aluminum-garnet (Nd: YAG) laser at relatively low power to restructure without devitalizing cartilage. An in vivo study was done in six dogs to determine appropriate laser dosimetry in a model of tracheal wall collapse created by a tracheotomy. The deformed cartilage was treated endoscopically with a noncontact 1.44-μm Nd: YAG laser, at 2 to 4 W of power with a repetition rate of 20 Hz, in three animals. As a control, three animals had endoscopic cartilage incisions followed by stent placement. Six weeks postoperatively, both groups had an adequate airway lined by healthy mucosa. In the animals with stenting, however, there was stenosis formation due to scarring at both ends of the stent, with significant inflammatory response in the local area. This study shows that it is possible to use low-power laser energy to reshape cartilage without destroying its viability, and to restore the tracheal wall to a normal contour without ablation or vaporization. The reshaped cartilage will tend to retain its shape with functional elastic force, as seen in in vitro studies. These preliminary results are encouraging, and it seems reasonable to consider using the technique in selected clinical cases as an alternative to conventional open surgery.

Erbium laser in middle ear surgery : in vitro and in vivo animal study

Cadaveric human temporal bones, cadaveric rabbits, and live rats were used to demonstrate the utility and safety of the erbium:yttrium‐scandium‐gallium‐garnet (Er:YSGG) laser for otologic applications. The shallow penetration in water of this wavelength and its ability to ablate bony tissue with minimal collateral thermal effects spare underlying and adjacent structures and make it appealing for stapedotomy. The authors were able to satisfactorily perform small fenestra stapedotomy, atticotomy, facial nerve decompression, and mastoidectomy. Temperature measurements from the round window area during Er:YSGG stapedotomy recorded an elevation of less than 2°C, which is well within acceptable limits. An acoustic shock produced at the impact site is the major disadvantage and requires further in vivo investigation of the transient and sustained deleterious effects away from the application site. This work supports further investigation into potential applications of the Er:YSGG laser in otology.

Diagnostic fluorescence spectroscopy of oral mucosa

Autofluorescence characteristics of normal, dysplastic, and malignant squamous tissues from the oral cavity were measured with a spectrofluorometer in the excitation range of 250 - 500 nm and emission range of 350 - 750 nm. Fluorescence excitation-emission matrices (EEM) were obtained from samples collected from patients in the clinic and in the operating room. The same samples were submitted for histopathological examination following spectroscopic measurements. The contour plots obtained from the EEMs of the samples showed consistent differences between normal and abnormal tissues. All the abnormal samples showed enhanced red region (> 600 nm) fluorescence with a prominent peak at 635 nm, when excited by 410 nm light. A ratio contour plot (abnormal/normal) enhanced spectral differences in the red region. A fiber-optic based spectrofluorometer for EEM measurements is being developed for further investigations.

Pulsed delivery of laser energy in experimental thermal retinal photocoagulation

Retinal lesions produced with a pulsed laser beam of 1-20 kHz frequency and 10-100% duty cycle were compared with lesions produced with a continuous wave (cw) laser of the same peak power and total energy. Photocoagulation was applied to the retina of three black pigmented rabbits using krypton red laser (647.1 nm) equipped with an acousto-optical modulator to convert cw laser emission to a pulsating beam. An optical fiber fed the laser beam into an optical system delivering a collimated beam of predetermined divergence; the animals eye focused this beam to a 50-pm spot on the retina. Peak power was kept constant at 0.2 W, and energy was kept constant at 20 mJ. After 7 months the animals were sacrificed and retinal tissue examined by light microscopy. The central section of each lesion was identified and photographed. For lesions with the same energy per pulse and the same pulse duration, the most influential factor, in the frequency range of 1-20 kHz, appeared to be the duty cycle: the smaller the duty cycle, the smaller the lesion, and vice versa. In other words, the shorter the time interval between consecutive pulses, the larger were the pulsed laser lesions.

Laser-assisted cartilage reshaping: in vitro and in vivo animal studies

Correction of cartilaginous defects in the head and neck area remains a challenge for the surgeon. This study investigated a new technique for laser-assisted cartilage reshaping. The pulsed 1.44 micrometers Nd:YAG laser was used in vitro and in vivo experiments to irradiate cartilage to change its shape without carbonization or vaporization of tissue. Two watts of average power in non contact manner was used to irradiate and reshape the cartilage. The extracted reshaped cartilage specimens underwent testing of elastic force with a computer assisted measurement system that recorded the changes in elastic force in the specimens from 1 hr to 11 days post-irradiation. An animal model of defective tracheal cartilage (collapsed tracheal wall) was created, allowed to heal for 6 weeks and then corrected endoscopically with the laser-assisted technique. The results of the in vitro and in vivo investigations demonstrated that it was possible to alter the cartilage and that cartilage would retain its new shape. The clinical significance of the technique is evident and warrants further animal studies and clinical trials.

Autologous fibrin tissue adhesive in endoscopic sinus surgery

Endoscopic sinus surgery may be complicated by bleeding, formation of synechia, and infection. This study investigated the application of autologous fibrin tissue adhesive during endoscopic sinus surgery in an attempt to avoid packing, to decrease complications, and to improve healing. Fibrin tissue adhesive from pooled human blood is a hemostatic and bacteriostatic agent. Autologous fibrin tissue adhesive avoids the potential infectious and immunologic risks of the pooled blood product. Twelve patients undergoing bilateral endoscopic sinus surgery participated in the study. Phlebotomy and preparation of the adhesive were performed during the procedure. Fibrin tissue adhesive was applied to only one side, with the contralateral side used as a control. Bacitracin ointment was applied to the adhesive-treated side, and packing coated with bacitracin was placed on the contralateral side. Patients were observed for a minimum of 3 months, and results were documented with photographic and video recordings. A uniformly high degree of patient satisfaction was achieved because of the elimination of packing and a sensation of increased nasal airway patency on the fibrin-treated side. Fibrin tissue adhesive provided hemostasis, decreased crusting, accelerated mucosal healing, and diminished synechia. Autologous fibrin tissue adhesive is beneficial in endoscopic sinus surgery, and its application should be considered, especially when the risk of hemorrhage or synechia is increased.