An optical system injecting light directly to skin and collecting spectrally modified within skin backscattered portion of light has been designed and fabricated. This method reduces the noise generated by specular component nearly to zero. Seven clinical tests performed on patients with suspect skin lesions have been tested with our device and later biopsy was taken as a “gold standard” procedure. Three cases proved to be melanoma and our spectra indicated differences from those collected from non-melanoma lesions. The process of collecting spectral data was too time consuming.
To accelerate the process of data collection from the skin, using the same principle of diffuse spectroscopy, an imaging device was conceived which is able to collect skin spectral response at once from a relatively sizeable skin area. The requirement of a negligible specular component was considered of paramount importance. Two approaches can satisfy this requirement:
1. Collection of backscattered light directly from the skin
2. Injection of illuminating light directly to the skin without creating reflections directly from the skin.
We decided to use the second approach and construct a circular, circumferential illuminator with angled light injection. Before fabricating this illuminator, a thorough analysis was performed to optimize its radius and angle of injection in order to receive the highest uniformity of diffuse light in the skin. Monte-Carlo simulation was applied to a three layer skin approximation.The results of the simulation will be presented.
Exact color matching of dental restorative materials to vital teeth is a difficult task. There are several reasons for this difficulty and they will be elaborated upon in the presentation. One of the most important reasons is the fact that teeth, as well as dental restorative materials are translucent, and thus the color impression is a product of light scattering, back scattering, transmission, and spectral modifications inside of these objects. Classic colorimetry is insufficient to provide an exact color match. Additional information about the translucency factor of the considered object (material and geometry) is necessary to provide full reproducibility. Translucency has a direct effect on perceived brightness.
In this article we describe the TransluDent, a complementary product to ColorDent, which measures translucency of teeth and dental materials. TransluDent determines translucency by measuring light transmitted through an object and light scattered inside of the object.
The translucency measurements were performed on two groups of subjects. One group consisted of people in their twenties and the second group of subjects was in fifties. For comparison several sets of dental shade-guides were also tested. The great discrepancy in translucency factor between human teeth and popular on the market shades may explain difficulty in color matching of dental restorative materials to teeth.
A novel hypericin-based drug HyperflavTM has been evaluated for light-induced fluorescence detection of oral cancer. Squamous cell carcinoma was induced with carcinogenic agent in right pouches of forty hamsters (20/20 males/females). Solution of HyperflavTM was sprinkled into stomach with a single dose 0.2 - 4 mg of pure hypericin per kg b.w. and 4 - 8 hours before fluorescence analysis. In two animal groups with cancer symptoms the autofluorescence and hypericin-induced fluorescence were taken under 442 nm excitation. The buccal mucosa and adjacent areas were measured fiberoptically in-vivo and in-vitro using orange/green ratio (610/540). The in-vivo fluorescence imaging of malignant areas was conducted to assist the biopsy guidance and to compare with white-light images. Histological and morphological analyses were performed from biopsies. Oral squamous cell carcinoma in its early stage demonstrated specific higher 610/540 ratio for 37 tested hamsters. Advanced state involved another higher fluorescence maximum around 640 nm that in our opinion caused by strong porphyrin-induced native fluorescence. Such deformation of fluorescence spectra may lead to inadequate perception of diseased tissue area. To avoid this problem the autofluorescence spectra & images were added. HyperflavTM application is promising for demarcation of early oral cancer when combined with autofluorescence measurements.
Topinambour belongs to medicinal pants with unique useful chemical composition which is characterized by a wide range of biological-active substances. This composition stipulates high nutrient value of topinambour. On this basis the researchers of the Ukrainian Sate University of Food Technologies elaborated some technologies of prophylactic- curative food-stuffs. These products promote the strengthening of immune system, therefore they are very useful for all people, particularly for those who live on the region contaminated by radionuclides. The results of medical-biological and clinical investigations have been discussed in this paper.
Assessment of tooth color by visual evaluation is a complex task. A number of attempts to build a reliable instrument that can measure the color of teeth have been undertaken in the last 15 years. These attempts were aimed at using conventional colorimeters designed for color measurement of oblique objects. However, the translucency of teeth strongly affected the colorimeters' readout because of the size of the measuring aperture and the geometry of the spectroscope. Here we present the results of our spectroscopic study of dental materials and human teeth that show a characteristic behavior of optical spectra collected with a fiberoptic probe. The probe consisted of 300 micrometer irradiating and 1 mm detecting fibers that were coupled to a white light source (color temperature 6500 K) and to a spectroscope. The conventional shades from Vita and Chromascop shade guides were measured with different location of the fibers. The color of the dental shades was measured by a standard spectrophotometer with two different apertures. We found that registered spectra depended on fiber position and color coordinates changed with aperture size. The influence of the fiber positioning was approved with color measurement of vital teeth. A simplified colorimetric system based on two color coordinates, lightness L*, and the difference, (a* - b*), has been proposed. Finally, we describe a novel dental color matching device based on a fiberoptic probe. The device is able to classify all dental shades from Vita, Chromascop, and Bioform shade guides and is aimed at better color matching of restorative materials to native teeth.
Thin-film luminescent concentrators were studied as novel position sensitive optoelectronic devices. The concentrators were designed as a 16 X 16 lines grid or as a planar structure of 16 X 16 channels along two coordinates. Minimal distance between two lines in grid concentrators was 5 mm. Each line or channel was coupled to silicone photodiode which was connected via analog board and C/D converter to computer. 100-W halogen lamp was projected into concentrators via optical system. Software was developed to determine the center of the light spot and to show its border. Position of the center of the light source was determined with accuracy 0.5 mm. Processing time for this operation was less than 1 ms. The concentrators were able to detect the position of the light source under conditions which were similar to peripheral human vision. Such position sensitive optoelectronics device are promising to build smaller scale integrated device which could be perform of full detection and preprocessing operation in artificial human retina.
We have studied a prototype of human retina which is based on a round thin-film photoluminescent concentrator coupled at its edge to the circular Si-photodiodes. This passive integrated optoelectronic device can perform most important function of peripheral human vision: determination of position of the light source and motion detection. For 12-mm radius film we have got a spatial resolution 13 micrometers in the linear range +/- 5 mm. By stacking several films each with a different absorption characteristic it is possible to realize color sensitive element and, therefore, to perform full functions of human retina.
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.
One of the most important problems in modern laser medicine is the determination of system response on laser treatment. Reaction of living system is significant during many kinds of laser procedures like surgery, therapy and biostimulation. Our study was aimed to optimize laser exposure using feed-back fiber system for intravenous laser irradiation of blood (ILIB). This system consisted of helium-neon laser (633 nm, 5 mW) with coupled fiber unit, photodetector and PC interface. Photodetector signals produced due to light backscattering were storaged and processed during all blood irradiation procedure. Significant time-dependent variations were observed within 9-15 min after beginning of treatment procedure and were correlated with number of trials, stage and character of disease. The designed feed-back system allows us to register a human blood response on laser irradiation to achieve better cure effect.
Natural photodynamic pigment hypericin having intrinsic antitumor properties was applied for fluorescence detection of cancer. Clinical investigation of hypericin was performed to ensure high tumor/normal fluorescence contrast in digestion organs. Laser-induced autofluorescence and exogenous fluorescence analysis of normal tissue and stomach adenocarcinoma was performed using helium-cadmium laser (8 mW, 442 nm). Twenty-one patients have undergone procedure of fluorescence detection of tumors before and after photosensitization. For sensitization of patients we used five or seven capsules containing hypericin in amount of 1 mg which have been administered orally. Strong yellow-red fluorescence of hypericin in tissue with maximum at 603 nm and autofluorescence peak at 535 nm gives an intensity ratio I(603 nm)/I(535 nm) of 2 - 2.5 from cancerous tissue and provides 85% specificity. Preliminary in vivo results of auto- and fluorescence analysis using hypericin photosensitization from one patient with esophageal cancer and eleven patients with stomach cancer proven histologically are encouraging and indicate the high reliability of laser-induced fluorescence technique with hypericin in detection of early stage malignant lesions.
Intravenous laser blood irradiation as an effective method of biostimulation and physiotherapy becomes a more popular procedure. Optimal irradiation conditions for each patient are needed to be established individually. A fiber optics feedback system combined with conventional intravenous laser irradiation system was developed to control of irradiation process. The system consists of He-Ne laser, fiber optics probe and signal analyzer. Intravenous blood irradiation was performed in 7 healthy volunteers and 19 patients with different diseases. Measurements in vivo were related to in vitro blood irradiation which was performed in the same conditions with force-circulated venous blood. Comparison of temporal variations of backscattered light during all irradiation procedures has shown a strong discrepancy on optical properties of blood in patients with various health disorders since second procedure. The best cure effect was achieved when intensity of backscattered light was constant during at least five minutes. As a result, the optical irradiation does was considered to be equal 20 minutes' exposure of 3 mW He-Ne laser light at the end of fourth procedure.
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.
Laser beam propagation inside tissues with different lateral dimensions has been considered. Scattering and anisotropic properties of tissue critically determine spatial fluence distribution and predict sizes of tissue specimens when deviations of this distribution can be neglected. Along the axis of incident beam the fluence rate weakly depends on sample size whereas its relative increase (more than 20%) towards the lateral boundaries. The finite sizes were considered to be substantial only for samples with sizes comparable with the diameter of the laser beam. Interstitial irradiance patterns simulated by Monte Carlo method were compared with direct measurements in human brain specimens.
A novel radiofrequency ablative system (40 msec-train pulses with twenty 200 msec pulses at the carrier frequency of 750 KHz and 1 Hz repetition rate) aimed at recanalizing totally occluded peripheral arteries was investigated by means of in vitro tissue ablation from human postmortem arterial wall samples. The samples were submitted to irradiation with a guidewire 150 cm long, maximum diameter of ceramic tip 0.033 inch positioned perpendicular to the tissue surface in saline, contrast medium or blood using varying generator power. Ablation efficacy was determined as the depth of vaporization per pulse delivered. Electrical current for the train duration was measured as voltage at the 1 ohm-resistor. In saline, the ablation efficacy increased from 8 to 65 mm/pulse with generator power increasing from 11 W to 27.5 W. There was no significant difference in the ablation efficacy between saline and blood. In contrast medium, the ablation efficacy was significantly lower. For the same generator power, the electrical current varied during the ablation procedure from 1.3 +/- 0.2 A at the beginning of the procedure to 1.1 +/- 0.2 A after the first pulses and to 2.0 A before artery wall perforation occurred. Neither tissue ablation nor current variations were observed when radiofrequency energy was emitted on calcified tissue. The diameter of craters was 0.89 +/- 0.1 mm (range: 0.85 - 0.96 mm). No major thermal injury such as carbonization or charring was observed. Thus, (1) radiofrequency energy emitted through a guidewire is reliable and effective for the ablation of arterial tissue; (2) the depth of penetration is related to the generator power; (3) the ablation efficacy is greater in saline and blood than in contrast medium; (4) the system is not effective in highly calcified tissue; (5) the procedure may be monitored by electrical current measurements.
A pulsatile blood flow model was used to estimate the influence of position of Doppler guide wires with 12 MHz forward looking ultrasound transducers on the average spectral peak velocity. Three 0.014-inch and three 0.018-inch Doppler guide wires were positioned in plastic tubes ranging from 1.7 mm to 8.0 mm internal diameter. Blood flow of 50, 100 and 200 ml/min was adjusted using a roller-pump. The flow velocity was lower by 54% near the wall than in the center of large tubes (diameter 8.0 mm). In tubes of 2.9 mm and 4.2 mm in diameter the maximum variations were 11% and 22.5% for the 0.014-inch guide wire and 7.5% and 20% for the 0.018-inch guide wire, respectively. No variance in velocity related to wire position was observed in small (1.7 mm) tubes. The system was not sensitive to angular displacement of the guide wire in the range of +/- 30 degree(s). These results demonstrate that intravascular Doppler ultrasound flowmeter may be accurately utilized for measurements of blood flow velocity in small coronary arteries without any need to reposition the guidewire.
The possibility of improving the focusing effect in laser scalpels employing tapered probes with a novel parabolic form has been studied. The irradiance distribution in conventional conical and parabolic tapered probes has been calculated by 3-D ray tracing in the tangent plane with taper angles 9 and 17 deg and their parabolic modifications. The results are compared with measurements of the light distribution in saline using a CCD camera. The irradiance increase in parabolic probes was four times that observed in conical probes. Laser scalpels with novel parabolic rods will be better for precise treatment of tissue than conventional laser scalpels with conical rods.
Optical fiber probes with isotropic response for direct measurement of fluence rate in tissue were studied. Two methods of probe fabrication were considered: in the first one, the isotropic spheres were fabricated by melting the fiber tips and then coated there with a layer of scattering material, in the second one, the spheres were fabricated from solid scattering material (milk glass). The core diameter of the quartz fiber was 120 micrometers ; maximum diameter of the probes was 420 micrometers . Anisotropy was determined as a standard deviation of light distribution at the isotropic fiber end. The second fiber end was coupled with different light sources: He-Ne, Ga-As lasers, or 200-W lamp. Melted probes had high anisotropy; it was necessary to cover the sphere by 4 or 5 layers to reduce the anisotropy less than 10%. Increase of isotropic response using a multi-layer covering was achieved at the expense of total transmission decrease (less than 1%). Melting technology deals with low reproduction and repetition of isotropic response. Anisotropy of glued probes was from 4.5% to 7.5% and total transmission ranged from 20% to 30%. Glued probes had sufficient mechanical strength to use their in vivo measurements of fluence rate. Because of influence of light coherency significant anisotropy increase was registered if the lamp was replaced by lasers.
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.
Light attenuation in a sample of human brain has been measured using a small (0.5 mm in diameter) fiber isotropic detector and similar to that an isotropic irradiator. Two lasers, He-Ne (633 nm) and GaAs (890 nm), were used. In vivo measurements were performed with rabbit brain. Penetration depth of 633 nm light was 1.3 mm and 2.4 mm respectively for human and rabbit brain. Propagation of 890 nm light was significantly higher, penetration depth was 2.8 mm for human tissue and 5.3 for rabbit.
Spherically shaped laser probes, primarily used in laser angioplasty to unobstruct occluded arteries have weak focusing abilities in physiological media due to index mismatching. Three- D ray tracing was developed to calculate the light distributions of aspherically modified tips (parabolic, hyperbolic, etc.). It was found that the focusing effects of aspherical silica (n equals 1.457) tips are up to 3.0 times better than those of spherical tips. It is possible to increase the irradiance of tissue in water by about 6 to 9 times using normal silica fiber without total internal reflection. Experiments were performed in air and in water using normal silica fiber without total internal reflection. Experiments were performed in air and in water using registration of light distribution with a CCD-camera and confirmed the theoretical predictions. For aspherical sapphire (n equals 1.75) tips increasing of maximum irradiance is more than 16 times than for spherical probes. The spherically modified tips are more atraumatic due to rapid decrease in fluence rate distal from the position of highest irradiance. Three-D ray tracing is useful to optimize the design of different modified tips.
An isotropic probe for direct measurement of fluence rate in tissue was made by melting 110 micrometers -core fiber to less than 0.4 mm sphere and painting by scattering material. Anisotropy response for the best probe of 0.35 mm diameter was +/- 10% in angular range to +/- 150 degree(s). The general position error of the probe in the tissue provided by experimental setup was less than 0.1 mm. The fluence rate was measured in the human leg in vivo at a depth of up to 5 mm for incident irradiance of 100 mW/cm2 and wavelength 625 nm (dye laser) for beam diameters of 1 mm and 5 mm. Effective attenuation coefficients of about 0.6 mm-1 (for depth of up to 1 mm) and 0.7 mm-1 (for muscle layers) were obtained. Differences in light distribution in the skin comparative to the deeper layers were not found.
The spatial irradiance distribution of optical modified fibers with beveled tips which can be used for lateral-aiming delivery systems was calculated using 3-D ray tracing. Light refraction and reflection at the front surface and second refraction at this surface after reflection by cylindrical fiber surface were taken into account. The results were compared to measurements using CCD-camera and goniometric measurements performed for silica (n equals 1.457) 0.6 mm-fibers in air and in water. The slope angle was varied from 18 degree(s) to 60 degree(s). To prevent a forward lighting, gold coating of the front fiber face was considered. Measured damage threshold of this coating yielded 2 W in air and 30 W in water for continuous wave Nd:YAG laser. For the Ho:YAG laser (250 microsecond(s) , 2 Hz) the measured threshold was 60 mJ in water and in air. To increase the focusing effect the front side of the fiber can be modified as a beveled spherical surface.
Modified (sculpted) optical fiber tips for medical delivery systems are described. Tips have aspherical profiles (parabolic, hyperbolic, etc.) Light distributions of modified silica (n = 1.457) tips were calculated using a 3-D ray-tracing program in air and water. It was found that the focusing effects of aspherical tips are from 2.5 to 3.0 times better than those of spherical tips. It is possible to increase the irradiance of tissue in water by about 6 to 9 times using normal silica fiber with high efficiency (without total internal reflection). Experiments were performed in air and water, using registration of light distribution with a CCD-camera, and confirmed the theoretical predictions.
Fiber-optic sensors C FOS) are wi. del y used for rioncontact measurements due to their simplicity, small size, insensitivity to
I nfl uence of el ectromagneti C fiel ds , hi gh metrol ogi cal characteristics, etc. The operation principle of FOS with intensity
modul ati on techni que I s based on the photodetector regi strati on of
1ight , reflected from the control 1 ed surface E I ) . The i ntensi ty of
detected 1 1 ght depends on th FOS' s di stance from the control 1 ed
surface, its form and inclination to sensor's axis, FOS shift speed,
etc. So they can be consider multipurpose.
We are devel opi ng FOS wi th i ntensi ty modul ati on techni que wi th
traight tips as well as with sloped tips. In FOS with sloped tips the
light ring spot is appearing on the controlled surface due to the
effect of symmetry. We use thi s phenomena to empl oy refl ected 1 i ght
more efficiently and to increase the FOS characteristics.
Tak i ng I nto account the fact that pr obl ems of cal cul aWl on of
fibers with sloped tip were not analyzed in details earlier-, in
particular, only the case of light distribution of parallel beams
runni ng was consi dered E 2) we wi I 1 conduct a consi stent cal cul ati on
of bounds of i rradi ance fi ci d , created by a fi ber wi th sl oped tip,
esti mate I i ght di stri buti on I n a 1 1 ght spot , and determi. ne
characteristics of the FOS with sloped tip.