The feasibility of monitoring exogenous dye uptake in tissue in vivo using pulsed photothermal radiometry.
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Animals↗
Biomedical subjects
R R Anderson
Publications and source records attributed to R R Anderson.
Dye-enhanced laser welding for skin closure.
The use of a laser to weld tissue in combination with a topical photosensitizing dye permits selective delivery of energy to the target tissue. A combination of indocyanine green (IG), absorption peak 780 nm, and the near-infrared (IR) alexandrite laser was studied with albino guinea pig skin. IG was shown to bind to the outer 25 microns of guinea pig dermis and appeared to be bound to collagen. The optical transmittance of full-thickness guinea pig skin in the near IR was 40% indicating that the alexandrite laser should provide adequate tissue penetration. Laser "welding" of skin in vivo was achieved at various concentrations of IG from 0.03 to 3 mg/cc using the alexandrite at 780 nm, 250-microseconds pulse duration, 8 Hz, and a 4-mm spot size. A spectrum of welds was obtained from 1- to 20-W/cm2 average irradiance. Weak welds occurred with no thermal damage obtained at lower irradiances: stronger welds with thermal damage confined to the weld site occurred at higher irradiances. At still higher irradiances, local vaporization occurred with failure to "weld." Thus, there was an optimal range of irradiances for "welding," which varied inversely with dye concentration. Histology confirmed the thermal damage results that were evident clinically. IG dye-enhanced laser welding is possible in skin and with further optimization may have practical application.
Animals↗
Endometrial ablation by means of photodynamic therapy with photofrin II.
OBJECTIVE: Photodynamic therapy is a technique in which tissue is irradiated with light after the use of a photosensitizing drug that produces singlet oxygen, which has a cytotoxic effect. The feasibility of using photodynamic therapy with photofrin II for endometrial ablation was studied. STUDY DESIGN: Fifty-eight rabbits were studied. Preferential uptake of photofrin II by endometrial tissue, compared with the myometrium, was established by drug extraction and fluorescence microscopy after administration of photofrin II intravenously. Dosimetry for endometrial ablation was established by administering photofrin II in 1, 2, 5, and 10 mg/kg doses and laser light (630 nm) at radiant exposures of 100 and 200 J/cm2. Histologic examination was performed at 24 hours, 5 days, and 10 days after treatment. There were two control groups. One group received laser light but no photofrin II, and the other received photofrin II without laser light. RESULTS: The concentration of photofrin II was three times higher in the endometrium than in the myometrium at doses of 1 and 2 mg/kg. Fluorescence microscopy of frozen sections of endometrium and myometrium showed a predominantly perivascular fluorescence from photofrin II. A dose of 1 and 2 mg/kg and a flow of 100 J/cm2 was adequate for endometrial ablation in rabbits. At 24 hours after treatment there was extensive hemorrhage and evidence of cell death in the entire endometrium and mild hemorrhage in 10% to 50% of the inner circular layer of the myometrium. At 5 days after treatment necrosis of the entire endometrium and the inner half of the myometrium was seen, but the outer half of the myometrium and the serosa were normal. There were no cases of uterine perforation. Similar results were seen at 10 days after treatment, except for the additional presence of inflammatory cells. Neither control group (drug without light, light without drug) showed any injury to the endometrium at 24 hours. CONCLUSION: We conclude that endometrial ablation can be effectively achieved in rabbits by means of photodynamic therapy with photofrin II without significant complications.
Animals↗
Determination of optical properties of turbid media using pulsed photothermal radiometry.
Pulsed photothermal radiometry (PPTR) measures blackbody radiation emitted by a sample after absorption of an optical pulse. Three techniques for obtaining the absorption coefficient of absorbing-only, semi-infinite samples are examined and shown to give comparable results. An analytic theory for the time dependence of the PPTR signal in semi-infinite scattering and absorbing media has been derived and tested in a series of controlled gel phantoms. This theory, based on the diffusion approximation of the radiative transport equation, is shown to model the time course of the detected signal accurately. Furthermore, when the incident fluence is known, the theory can be used in a non-linear, two-parameter fitting algorithm to determine the absorption and reduced scattering coefficients of a turbid sample with an accuracy of 10-15% for transport albedos ranging from 0.42-0.88.
Algorithms↗
Changes in milk pH and bicarbonate during 20 days of lactation in the guinea pig.
Milk samples were obtained from lactating albino guinea pigs after 4 to 6 h of separation from their offspring. The samples were collected in 5-ml glass vials and capped immediately. They were transported rapidly to a pH-gas analyzer for measurements of pH, bicarbonate, base excess, and partial pressure of CO2. Eight guinea pigs were sampled daily for 20 d for a total of 160 observations. Analysis of variance indicated animal and day differences. Regression analyses over days revealed equations of best fit to be quadratic, although stepwise trends were observed in the data as well. The quadratic model for pH was Y(pH) = 6.996 - .057X + .002X2, where X was day of lactation (R2 = .54). The model for bicarbonate was Y (-HCO3 in milliequivalents per liter) = 8.896 - .659X + .0202X2 (R2 = .60). For base excess, the model was Y (in milliequivalents per liter) = -22.65 - 1.99X + .069X2 (R2 = .58). The model for partial pressure of CO2 was Y (millimeters of Hg) = 38.63 + 1.06X - .080X2 (R2 = .33). Decreases in pH and bicarbonate were parallel to changes in mammary epithelial cells of guinea pigs in which degeneration of mechanisms responsible for two important ingredients relating to milk volume occur. These have been identified previously as reductions in lactose and potassium. Synthesis of the enzyme carbonic anhydrase with its resultant bicarbonate production may be related in some way to these components of milk secretion.
Acid-Base Equilibrium↗
Comparison of trace elements in milk of four species.
The objective of this study was to compare trace elements in milks of four species. Milk samples of 4 ml or more were obtained from guinea pigs, dairy cattle, horses, and humans. The milks were analyzed for the trace elements Al, B, Ba, Cu, Fe, Li, Mn, Mo, Si, Sr, Ti, and Zn by inductively coupled argon plasma spectroscopy. Zinc ranged from more than 4 ppm in guinea pig milk to less than 2 ppm in mare milk. Strontium was over 1 ppm in the milk of guinea pigs and less than .1 ppm for the human. Iron ranged from over .7 ppm for the guinea pig to less than .2 ppm for the cow. Copper was over .5 ppm in guinea pig milk and only .05 ppm for cow milk. Boron ranged from .59 to .10 ppm, Si from .58 to .16 ppm, Al from .45 to .10 ppm; and Ba from .22 to .08 ppm in milks of the four species studied. Titanium ranged from a trace to .11 ppm. Lithium, Mn, and Mo all were less than .04 ppm. Milk Mn was surprisingly low relative to bodily needs.
Animals↗
Photodynamic therapy in dermatology. Shedding a different light on skin disease.
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Dermatology↗
Postsclerotherapy hyperpigmentation.
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Female↗
Burn depth estimation using indocyanine green fluorescence.
Expedient primary excision of deep dermal and full-thickness burn wounds with subsequent skin grafting is the standard of care in most burn institutions, but differentiating full-thickness from partial-thickness burns is often difficult. Because accurate early assessment of burn depth may improve care, a variety of technical methods have attempted to measure burn depth but these methods have had limited success. We describe a new technique to determine burn depth that uses infrared (840- to 850-nm) fluorescence emission from intravenously administered indocyanine green following excitation with infrared (780 nm) and UV light (369 nm). Full-thickness and partial-thickness burns in hairless rat skin were distinguished based on the infrared-induced and UV-induced fluorescence intensity ratios relative to normal, unburned skin immediately after the burn and on post-burn days 1 through 3 and 7. Dual-wavelength excitation of indocyanine green infrared fluorescence can delineate full-thickness from partial-thickness burns at an early date, allowing prognosis, surgical planning, and early primary excision and grafting.
Animals↗
A laser densitometer for selective spot analysis on dot blots and two-dimensional gel autoradiograms.
We describe an inexpensive densitometer, employing a small HeNe laser and an IBM-compatible personal computer that performs accurate measurements of selected spots on two-dimensional gel autoradiograms or chromatograms with an accuracy and a sensitivity equal or superior to those of many commercial instruments. Our open-table design allows the operator to visually monitor the scanning process in room lighting, and provides great flexibility in both the size and the nature of items to be scanned. The instrument has two moving parts (a prism and a small motor). A commercially available software package (ASYST) acquires digital data, graphs the data on the TV monitor, converts the data to optical density or to radioactive incorporation (cpm), subtracts background, integrates peak areas, and stores data on disk. The total time for these operations is 20-30 s per spot. The instrument has a dynamic range of 0.25 to 3.0 OD units and can measure a 10,000-fold range of 14C or 35S isotope concentrations on autoradiograms. The complete device can be assembled with a hobbyist's knowledge of electronics, moderate programming abilities (no machine language required), and a cost of less than $3000, not including the IBM PC.
Costs and Cost Analysis↗
Light and electron microscopic analysis of tattoos treated by Q-switched ruby laser.
Short-pulse laser exposures can be used to alter pigmented structures in tissue by selective photothermolysis. Potential mechanisms of human tattoo pigment lightening with Q-switched ruby laser were explored by light and electron microscopy. Significant variation existed between and within tattoos. Electron microscopy of untreated tattoos revealed membrane-bound pigment granules, predominantly within fibroblasts and macrophages, and occasionally in mast cells. These granules contained pigment particles ranging from 2-in diameter. Immediately after exposure, dose-related injury was observed in cells containing pigment. Some pigment particles were smaller and lamellated. At fluences greater than or equal to 3 J/cm2, dermal vacuoles and homogenization of collagen bundles immediately adjacent to extracellular pigment were occasionally observed. A brisk neutrophilic infiltrate was apparent by 24 h. Eleven days later, the pigment was again intracellular. Half of the biopsies at 150 d revealed a mild persistent lymphocytic infiltrate. There was no fibrosis except for one case of clinical scarring. These findings confirm that short-pulse radiation can be used to selectively disrupt cells containing tattoo pigments. The physial alteration of pigment granules, redistribution, and elimination appear to account for clinical lightening of the tattoos.
Biopsy↗
Comparative studies of femtosecond to microsecond laser pulses on selective pigmented cell injury in skin.
Threshold radiant exposures for grossly apparent immediate whitening and ultrastructural alterations of melanosomes in black guinea pig skin were determined for a series of red visible laser pulses ranging from 4 x 10(-4) to 6.5 x 10(-14) s. Threshold exposures for melanosomal injury were found to be independent of pulsewidth when the pulsewidths were below the estimated thermal relaxation time of melanosomes. Threshold radiant exposures for melanosomal injury were found to increase when the pulsewidths were approximately equal to or above the thermal relaxation time of melanosomes. At longer pulse durations, fracturing of melanosomes was not observed despite the longer exposures necessary for injury. Instead, perimelanosomal vacuoles were noted. These findings are consistent with the theory of selective photothermolysis and provide evidence for the thermal initiation of melanosomal disruption.
Animals↗
Q-switched ruby laser irradiation of normal human skin. Histologic and ultrastructural findings.
The Q-switched ruby laser is used for treatment of tatoos. The effects of Q-switched ruby laser pulses on sun-exposed and sun-protected human skin, as well as senile lentigines, were investigated with clinical observation, light microscopy, and transmission electron microscopy. A pinpricklike sensation occurred at radiant exposures as low as 0.2 J/cm2. Immediate erythema, delayed edema, and immediate whitening occurred with increasing radiant exposure. The threshold for immediate whitening varied inversely with skin pigmentation, ranging from a mean of 1.4 J/cm2 in lentigines to 3.1 J/cm2 in sun-protected skin. Transmission electron microscopy showed immediate alteration of mature melanosomes and nuclei within keratinocytes and melanocytes, but stage I and II melanosomes were unaffected. Histologically, immediate injury was confined to the epidermis. There was minimal inflammatory response 1 day after exposure. After 1 week, subthreshold exposures induced hyperpigmentation, with epidermal hyperplasia and increased melanin staining noted histologically. At higher radiant exposures, hypopigmentation occurred with desquamation of a pigmented scale/crust. All sites returned to normal skin color and texture without scarring within 3 to 6 months. These observations suggest that the human skin response to selective photothermolysis of pigmented cells is similar to that reported in animal models, including low radiant exposure stimulation of melanogenesis and high radiant exposure lethal injury to pigmented epidermal cells.
Adult↗
Efficiency of opaque photoprotective agents in the visible light range.
"Opaque" physical sunscreens are important for photoprotection of individuals with visible light and UV-A photosensitivity such as those with porphyria, drug photoallergy, and polymorphous light eruption. Diffuse spectral transmittance of various thicknesses of opaque sunscreen formulations were measured from 350- to 800-nm range using a spectrophotometer equipped with an integrating sphere. Transmission through 20% zinc oxide paste was high and decreased minimally despite large increases in the sunscreen layer thickness. Adding a visible light absorber such as iron oxide to scattering sunscreens, however, substantially lowered transmittance below that predicted by the product of the transmittances for each component alone. Opaque sunscreens protected against hematoporphyrin derivative photosensitization of albino guinea pig skin; these results were quantitatively consistent with the in vitro findings. Poor photoprotection against visible light is obtained with white paste sunscreens, even if thick layers are applied. The addition of pigments to such sunscreens, however, greatly enhances photoprotection and cosmetic acceptability.
Animals↗
Polarized light examination and photography of the skin.
Light reflected from skin has two components: regular reflectance, or "glare" arising from the surface, and light backscattered from within the tissue. The regular reflectance contains the visual cues related to surface texture, whereas the backscattered component contains the cues related to pigmentation, erythema, infiltrates, vessels, and other intracutaneous structures. Unlike the backscattered component, regular reflectance preserves the plane of polarization of polarized incident light. Thus, viewing skin through a linear polarizer, under linearly polarized illumination, separates the two components of tissue reflectance. Thirty patients were examined and photographed in this manner. When the planes of polarization are parallel, images with enhanced surface detail are obtained. When the planes are orthogonal, wrinkles and surface detail disappear, and an enhanced view of vasculature and pigmented lesions is obtained. Simple, clinically useful techniques are presented.
Humans↗
Irradiation of pigmented melanoma cells with high intensity pulsed radiation generates acoustic waves and kills cells.
Photokilling of pigmented mouse melanoma cells (B-16) was investigated using pulsed high intensity visible radiation. Melanin acts as an endogenous chromophore, and 694 nm radiation with 40 nsec pulse duration and 0.5-3 X 10(7)w/cm2 intensity causes cell death. Irradiation of non-pigmented human melanoma cells (U1) or human squamous carcinoma cells (FaDu) under similar conditions did not kill the cells. Also, irradiation of B-16 cells with 300 microsec laser pulses (10(3)W/cm2) or with continuous wave (CW) radiation (10(-3)W/cm2) did not kill the cells. These data indicate that pigmented cell killing is due to absorption of radiation by melanin and that the pulsewidth and intensity of radiation play important roles in cell killing. The generation of acoustic waves due to absorption of the pulsed radiation by pigmented cells and by isolated melanosomes was demonstrated at 532 and 625 nm and 8.5 nsec pulse duration (10(7)-10(8) W/cm2); the amplitudes of the acoustic signals were approximately 2.5-3.0-fold higher at 532 nm compared with 625 nm, and they increased with increasing fluence. In contrast, irradiation of U1 or FaDu cells with comparable fluences and intensities did not generate acoustic waves. A possible correlation between the generation of photoacoustic waves and pigment cell death is proposed. Since the thermal relaxation time of melanosomes is 0.5-1.0 microsec, the mechanism proposed is that thermal confinement of high intensity, short-pulse visible radiation generates acoustic waves by thermal expansion, leading to mechanical damage to the cells.
Acoustics↗
Effect of blood upon the selective ablation of atherosclerotic plaque with a pulsed dye laser.
Laser angioplasty systems with laser energy preferentially absorbed by atherosclerotic plaque may offer a safe method of plaque removal. This study evaluated the effect of blood upon selective energy absorption using a pulsed dye laser at 480 nm. Intra-arterial laser irradiation of normal rabbit femoral arteries demonstrated a perforation threshold energy with blood perfusion of 13.1 mJ per pulse compared to 87.9 mJ with saline (P less than .0001), indicating a deleterious effect in the presence of blood. An adverse effect upon arterial healing at 3 days was noted in sheep following intra-arterial irradiation during blood but not saline perfusion. Normal and atherosclerotic human aorta ablation thresholds differed significantly (P less than .0002) under saline (plaque: 20 mJ and normal: 120 mJ) but the difference under blood (plaque: 5 mJ and normal: 20 mJ) was not significant. We conclude that absorption of laser energy by blood can reduce the effect of differential absorption by endogenous chromophores in normal and pathologic vascular tissues and, therefore, removal of blood may be a prerequisite for selective ablation of atherosclerotic plaques.
Animals↗