The objective of the study was to design, to investigate and to optimize non-contact fiber delivery system for different clinical applications. This system eliminate the main disadvantages both applied contact and non-contact probes, namely surface contamination with further probes thermal deterioration and large beam divergence, respectively. The main part of the proposed non-contact fiber delivery system is probe made in fused silica or synthetic sapphire which produces quasi-collimated beam with specific outside diameter and power distribution along this beam. These probes were designed for different laser clinical applications, especially for interstitial thermotherapy and photodynamic therapy. Five different types of them were manufactured by InnovaQuartz, Inc. (Phoenix, AZ, USA) and Tochpribor (Kharkiv, Ukraine). To provide comparative analysis and optimization of the optical properties of the novel fiber delivery systems with commercially available ones "steady beam distance"; "steady beam ratio" and "power density efficiency" coefficients are proposed. The improved versions of the commercial urologic devices "transurethral optical laser knife" (Mayo Clinic), TULIP (Intrasonics), UroLase (Bard), SideFire (Myriadlase), ADD (Laserscope), UltraLine (Heraeus Lasersonics), ProLase II (Cytocare) are examined. The received results could provide a tool useful to designers of noncontact fiber delivery systems intended for different clinical applications with cw and pulse lasers.
Several fiber optic probes attached single- or multi-fiber light delivery systems have been competitively examined for purposes of in vivo tissue fluorescence spectroscopy with endoscopic technique use. The effects of the probes' designs and excitation/receiving fiber geometry on fluorescence spectra are analyzed with the sensor optical efficiency (SOE) coefficient and the tip coupling efficiency (TCE) one calculated by means of ray tracing. The profiles of the excitation beam as well as fluorescence profiles were simulated with uniform and Gaussian cross power distributions, whereas the diameter of the tissue surface area from which fluorescence light was collected was taken as five diameter of the tissue surface area directly illuminated by the excitation beam. The plots of the SOE-coefficients versus changeable probe-tissue gap simulated possible peristaltic tissue movement during clinical in situ spectroscopic optical biopsy would be a helpful tool for specialists to design novel endoscopic fiber optic catheters to differentiate normal and pathologic tissues.
We considered the limited number of light-induced fluorescence applications for marketed ultra-bright blue LEDs where they can compete with versatile laser sources. Satisfactory optical output and miniature size as well as low power consumption of blue LEDs emitting at 470 nm allow to consider them as a promising alternatives to metal vapor or gas lasers used in many expires LIF applications. Available to authors LEDs form Hewlett-Packard, Micro Electronics Corp., Nichia Chemical Industries Ltd. and Toyoda Gosei Co. were tested to comply with demands to a tissue excitation source for portable spectroscopes. The optical performance of LEDs has shown that selected group of InGaN LEDs could be successfully used for that. The miniature illuminator that includes LED, focusing condenser, filter set and distal fiberoptic light concentrator was designed and tested in conjunction with portable CCD- equipped spectroscope. Operating in dark condition the proposed LED illuminator provides the level of fluorescence signal sufficient to detect spectral abnormalities in human Caucasian skin and excised gastrointestinal samples. All tissue autofluorescence data taken under LED illumination were compared with readings under He-Cd laser excitation and showed a good match. A new diagnostic designs based on LEDs were considered for clinical use.
Optical biopsy of stomach mucosa was performed afterwards oral administration of encapsulated hyperflav (single dose was chosen to provide 0.1 - 0.15 mg/kg b.w.) A sufficient fluorescence contrast of suspicions versus normal tissue was obtained after incubation time from 4 to 10 hours. Fluorescence was induced by He - Cd laser coupled to fiber optic probe inserted into a biopsy channel of the endoscope. Fluorescent spectra were recorded in the range from 500 nm up to 700 nm with 2 nm resolution. We took two groups of patients with benign and malignant ulcer of the stomach and erosive gastritis. The first group consisted of 59 patients (male/female 36/23) was carried out with optical biopsy of stomach mucosa. The second group consisted of 60 patients (male/female 39/21) was carried out by routine method: gastroscopy and biopsy from 5 - 7 places of macroscopically changed mucosa.
The objective of the study was to design and to investigate laser fiber delivery system for treatment of obstructed human internal tubular organs using endoscopic techniques. This system eliminates the main disadvantages of both applied contact and non-contact probes, namely surface contamination with concomitant hydrothermal probe deterioration and large beam divergence with poor energy density, respectively. Proposed silica or sapphire probes produce quasi-collimated beam with specific outside diameter and power distribution. To provide comparative analysis of laser delivery systems' optical properties with non-contact endoscopic probes 'steady beam distance' (SBD) and 'steady beam ratio' (SBR) coefficients are proposed. The calculation results are presented in the form of the plots of the SBR - coefficients and SBDs for a 2.0 mm specific outside beam diameter versus laser wavelength, delivery fiber core diameter and its numerical aperture for both probe material. Additionally, the cross power distributions along the SBD were studied. Results obtained could provide a useful tool to designers of non-contact fiber delivery systems intended for a variety of medical applications, including endoscopic surgery with cw or pulse laser tissue irradiation, skin de-epithelialization, laser-induced fluorescence and photodynamic therapy.
In recent years, in-vivo optical spectroscopy has become widely used during many routine endoscopic procedures for purposes of biomedical science and practical medicine by virtue of its non-invasive effect and real time remote detection convenience. Fiber optic probes are an important unit of spectroscopic equipment for providing effective excitation and light gathering on site. Probes should be small enough to be easy introduced into the instrumentation channel of standard flexible or rigid endoscopes. Several commercial and custom types of fiber tips for applications in diagnostics have been examined. Single- and multifiber delivery schemes are also discussed. To provide comparative analyses of probes' optical properties, sensor optical efficiency and tip coupling efficiency coefficients have been proposed. These coefficients are a quantitative measure of probe optical efficiency and have been calculated by means of ray tracing for both fiber-tissue and tissue-fiber traces. These results could be a helpful tool for designers of fiber probes for Raman, laser-induced fluorescence and elastic-scattered spectroscopy of internal human organs.
The fluorescence spectra from stomach mucosa have been measured for cancer diagnostics using hypericin as a photosensitizer. Hypericin was administered orally in amount of 0.1 mg/kg b.w. four hours before conventional endoscopic procedure. Fluorescence was induced by He-Cd laser coupled to optical fiber probe which was inserted into a biopsy channel of the endoscope; the output power at the distal fiber end was 6 mW. Fluorescent light was collected fiber optically and registered by a spectroanalyzer in the range up to 700 nm. Detection algorithm included a comparison of characteristic orange fluorescence of hypericin at 600 nm with fluorescence at 530 nm in conjunction with results of white-light endoscopy. Fluorescence procedure was performed in thirty-seven patients with various oncological and other stomach disorders. It has shown an average 90 percent specificity in detection of small size lesions. Developed technique is promising to detect early stomach cancers and indicate an advantage of laser induced fluorescence with photosensitizer hypericin in differential cancer diagnostics.
During the clinical endoscopic LIF-diagnostics of human digestion organs is needed to register fluorescence spectra in situ. Taking into account intensive bloodstream and therefore strong hemoglobin absorption of laser light the registered fluorescence signal is strongly dependent on distal probe geometry. The contact optics sensor is specially designed to enhance acquisition of auto- and exogenous fluorescence spectra from tissues. The fiber optics sensor consists of cylindrical sapphire or silica body with flat proximal and spherical distal end and tapered tip. The latter one has been made of optical material. This tip has been arranged abutting against the proximal end of the cylindrical body. Such sensor design offers to collect autofluorescent light in wide angle region effectively. Moreover that offers to use sensor simultaneously as an efficient both laser radiation collector and fiber coupler to transport exciting light at the testing site and backward. The produced distal probe has been used through the biopsy channel to endoscope. Original beam splitter throws 80% of fluorescent signal toward detector and simultaneously transmits up to 85% of He-Cd laser radiation to the tissue.
Original design of the multichannel two-reflector optical systems for astronomical and atmospheric devices have been considered. Their feature is the presence of odd or even number of holes in the secondary mirror corresponding to the number of the isolated channels. Formulas for determining diameter and arrangement of these holes are adduced. Proposed optical systems ensure considerably higher light transmittance (in 1.3 - 5.2 times according to isolated channels' number and screening coefficient value) than conventional two-mirror objectives. Technical realization of proposed three-channel objective was successfully produced.
Two original designs of mirror image rotator systems (IRS) on base of five plane mirrors with planar perpendiculars for panoramic plane pivots of the infrared solar spectrographs and circular review systems are considered. Comparison of conventional three-mirror IRS with proposed ones showed advantages of the latter, such as: mirror sizes' decreasings (in 1.8 - 2 times), decrease of the longitudinal and radial dimensions of the system (in 1.3 - 3 times) and optical pathlength for axis beam (in 1.25 - 3 times).
Biomedical science and practical medicine need special techniques for reliable real-time remote detection and determination information from human tissue. Most applications of these techniques in interior organs are based on optical fibers which should not only be able to deliver excitation light with minimal loss but provide effective light gathering from tissue being under the test. As emitted from tissue optical signal is often weak especially if autofluorescence spectroscopy is chosen for diagnostics, an efficient collection by fiber optics probe became essential. The main part of the proposed fiber optics probes is a specially designed tapered tip with one flat surface and another spherical one. This tip operates as a collector, transmitter and coupler to deliver light to the tissue and backward to the detector simultaneously. To find geometrical dimensions of tips optimized for these purposes calculating formulas have been adduced. These optimized tips could collect fluorescence signal from biological sites in wide angular aperture region and could transport light without leakage on tapered surface. When delivery fibers are placed at the focal plane of tip spherical surface an efficient optical coupling with them is achieved. Ray tracing of the tapered tips has been performed on sapphire and quartz tip materials in air and in saline to determine the best sensor design.
The paper deals with a problem of light focusing on the tissue for laser surgery, diagnostic and therapeutics with assistance by tapered tips. Optimization of the shape and geometrical dimensions of laser scalpels sought to minimize tissue damage by means of exception of light leaking through the tapered surface and decrease of distal end inner reflection. These results can be achieved by simultaneous attaching,spherical shape to the front surface of tapered tip also optimization of fiber-tip distance and tip dimensions. Analytical and ray-tracing calculations have been performed for sapphire (n equals 1.75) and silica (n equals 1.45) tip materials and air or saline (n equals 1.33) mediums. The diameter of aperture diaphragm and reflection number of incident beam in the tip have been varied from 1 to 5 fiber core diameter and from 1 to 10, respectively. Several numerical methods for evaluation of tip efficiency for optimized and conventional tips were discussed. Some versions of commercially available tip modernization have been presented. Modification of front surface of the tapered tip increased the angular aperture from 4 degrees to 12 degrees (in air) and from 8 degrees to 15 degrees (in saline) with obviating light leaking in commercial tip by Hans Sttetler SA, Switzerland. Replacement of the contact flat laser scalpel (surgical laser technologies, Malvern, PA) to an optimized one allowed us to increase the taper angle from 1.9 degrees to 10 degrees and produced, therefore, shorter and stronger tip without reducing its optical properties.
System for transformation of radiant flux as a delivery system with modification of the flux diameter was considered. That can be used with most efficiency in modelling radiators and simulators for electro-optical test facility where there is necessity of modulation of collimated radiant flux with considerable diameter D1 and little angular convergence or divergence 2(alpha) . This system consists of consecutively installed coaxes reflecting concentrator with tapered angle 2(beta) and cylindrical hollow fiber of diameter D2, at first; two mirror truncated cones formed in meridian section angular mirror with angular basis (beta) , at second. These two mirror cones carried out the recollimation of radiant flux for obtaining the starting angular convergence (divergence) 2(alpha) . Formulas for determining geometrical dimensions of this delivery system depending on concentration rate C both angles (alpha) and (beta) are adduced. One attends those energy losses for this transformation of radiant flux were not more than 2 - 3%. Focon-fiber configuration of proposed delivery system has been presented.
Five original designs of iris diaphragms to overlap coaxes round and annular apertures of the multichannel mirror or lens-mirror objectives are considered. Authors have proposed three novel configurations of the iris diaphragm lobes and also several diaphragm designs where referred lobes have been combined with ordinary ones. Horse-shoe shape lobe has been basic for all types of proposed iris diaphragm designs. Firstly this lobe is a main part of fan-diaphragm to intercept mirror objective annular aperture. Secondary that had been a prototype for both moon shape lobe and flat ring shape one. Thirdly usual iris diaphragm should be formed annular zone diaphragm in combination with fan-diaphragm. Proposed iris diaphragms has been designed to intercept both annular and round apertures of mirror and lens-mirror objectives simultaneously as well alternately. Formulas for calculation geometrical parameters of different kinds of the lobes and their disposition on the stationary mountings have been adduced. One attends that total light losses through screening should not be more than 18 - 20%. Technical realization most of proposed iris diaphragm designs have to be of interest for purposes of electro-optical test facility.
Fluorescence signal during tissue LIF-analysis depends on both excitation conditions and tissue optics, registration optics and location of the probe relative to tissue sample as well. To develop reliable fiber optic probes and optimize their position the spatial distribution of tissue fluorescence should be studied. Fluorescence indicatrices of skin of rat were measured in angular range of 80 degrees. Excited light from He-Cd (20 mW, 442 nm) laser was delivered on the cutaneous surface at the angular range from 0 to 60 degrees with the tissue surface. Fluorescence was registered in the spectrum between 530 nm and 700 nm with 1.5 nm resolution. Autofluorescence of the skin of 5 white rats was studied in-vivo. Local application of sensitizer hypericin was used for stimulated fluorescence studies. Fluorescence indicatrices were not corresponded to scattering ones under the same conditions and depended on incident angle of excitative laser beam. No influence of polarization of excitative beam on outside fluorescence distribution was observed. Maximum in-vivo fluorescence yield was registered at the normal incidence. There were observed marked differences between spatial distribution of normal and photosensitized rat skin tissues.
Hypericin has been studied as a novel natural photosensitizer for PDT. It has been extracted from plants (St.-John's-wort). Oral administration (10% alcohol solution in a dose 2 mg/kg b.w.) was applied for 15 patients with gastric cancers 18 - 48 h before surgery. Normal and cancerous tissue samples were resected and underwent fluorescence analysis 1 - 2 h after resection. Tissue fluorescence was excited by He-Cd (20 mW, 442 nm) and Ar laser beams (100 mW, 488 nm) and registered from 510 to 725 nm. In tissue hypericin has maximum fluorescence peak at 603 nm for both excitation wavelengths. Fluorescence intensity ratio I603/I503 chosen as a criterion for tissue classification was varied from 1.6 to 3.2 (mean 2.5) for adenocarcinoma under He-Cd excitation whereas Ar laser excitation gave from 2.5 up to 4.2 (mean 3.5). Normal tissue had this ratio from 0.48 to 0.65 (mean 0.55) and from 0.53 to 0.75 (mean 3.5) for He-Cd and Ar laser excitation, respectively. No side effects were observed in patients during 6 month follow-up.
Fluence rate was measured in normal and cancerous (glioma) human brain samples using a multichannel detector. Detector consisted of 8 isotrope fiber probes positioned around the central irradiating probe. Detecting probes were displaced one from other at a step 0.5 mm along the central irradiating fiber. Bare ends of detecting fibers were coupled with photodiode array. He-Ne (633 nm) or Nd:YAG (1064 nm) lasers were coupled with irradiating probe. Fluence rate was measured in each of 8 points in the depth range 5 mm. Measured mean penetration depths of 633 nm light were 0.70 mm, 0.50 mm and 0.40 mm for white matter, grey matter and glioma, respectively. For Nd:YAG laser, penetration depth was about 2.3 mm for normal tissue and glioma. Multichannel computerized detector allows to provide a small invasive real-time measurements of fluence rate in different tissues.
Bent multimode optical fibers were studied using a 3D ray tracing program. Effect of fiber bending increased with smaller input aperture beams. Transmission of fibers decreased for the longer proximal straight part of the fiber. Significant focusing effect and output light redistribution were detected if a proximal straight part of the fiber was less than 1 fiber diameter. Transmission of hollow waveguides considerably depended on the inner surface quality. Calculated data were in accordance with experimental measurements of fiber transmission and output light distribution. Ray tracing is a useful approach to simulate different delivery systems using optical fibers and hollow waveguides.
The optimization of shape of conical laser probes in respect of minimization of light leaking through the tapered side surface was considered and possibility by improving a focusing effect in laser scalpels employing tapered probes with a novel parabolic form was studied.