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Biomedical subjects

R R Anderson

Publications and source records attributed to R R Anderson.

At least 109 records · Page 6Linked to original sources
PubMed1993

Treatment of benign pigmented epidermal lesions by Q-switched ruby laser.

BACKGROUND: Disorders of cutaneous pigmentation are a common problem, which can cause substantial cosmetic morbidity. Traditional treatments are often ineffective and sometimes associated with further hyperpigmentation, hypopigmentation, or scarring. Because the Q-switched ruby laser has proven useful for the treatment of tattoos and, in a small number of cases, benign disorders of the epidermal melanin, we decided to apply this modality systematically to additional benign pigmented lesions. METHODS: Thirty-four benign pigmented epidermal lesions including lentigines, café-au-lait macules, and nevi spili in nine white patients were exposed to single pulses of a Q-switched ruby laser (694 nm, 40 ns pulse duration) at 4.5 and/or 7.5 J/cm2. RESULTS: After one treatment, substantial clearing occurred at each fluence in all lentigines and café-au-lait macules. Initial improvement was achieved in a small nevus spilus after two treatments at 4.5 J/cm2 and a larger nevus spilus after one treatment at 7.5 J/cm2 with complete removal of the junctional or compound nevi portion but no improvement in the café-au-lait portion. Complete return of the background pigment was observed by 1 year. There was no scarring. Immediately after treatment, histology revealed vacuolization of keratinocytes and melanocytes, and occasional subepidermal blisters. CONCLUSIONS: These findings show that while the Q-switched ruby laser may not be entirely useful for treating nevi spili, it does provide an effective treatment for lentigines and café-au-lait macules.

Adolescent↗
PubMed1993

Clinical use of the Q-switched ruby and the Q-switched Nd:YAG (1064 nm and 532 nm) lasers for treatment of tattoos.

BACKGROUND: The desire to remove tattoos has probably been around as long as their existence. Recent technological advances in lasers have finally made it possible to remove tattoos without leaving an equally undesirable scar. OBJECTIVE: The purpose of this article is to review the use of the Q-switched ruby (694 nm) and the Q-switched Nd:YAG (532 and 1064 nm) lasers for effective removal of tattoo ink, with cosmetically appealing results. RESULTS: The Q-switched ruby laser (694 nm) effectively removes blue-black and green ink, may treat other colors less efficiently, and is frequently associated with transient pigmentary changes, including rare depigmentation. The Q-switched Nd:YAG laser at 1064 nm quickly removes black ink, as well as other colors less efficiently; pigmentary changes are much less frequent, correlating with its lower absorption by melanin. The 532-nm wavelength treats red ink effectively, but also leads to temporary hypopigmentation. Transient textural changes may be noted at all three wavelengths discussed, but scarring is rare. CONCLUSIONS: Q-switched lasers can remove tattoos without residual scarring. Efficacy of ink removal is dependent on the wavelength used for the targeted pigment.

Adult↗
PubMed1993

The Q-switched Nd:YAG laser effectively treats tattoos. A controlled, dose-response study.

BACKGROUND AND DESIGN: The Q-switched ruby laser was recently shown to remove tattoos without scarring. The Q-switched neodymium: yttrium aluminum garnet (Nd:YAG) laser, which targets black ink with a longer wavelength that has less absorption by melanin, should effectively treat tattoos with fewer pigmentary alterations. A prospective, blinded, controlled study was conducted to assess the ability of the Q-switched Nd:YAG laser (1064 nm, 10 ns, 5 Hz) to remove tattoos. Twenty-five patients with 39 blue-black or multicolored tattoos (14 previously untreated, 25 Q-switched ruby laser-resistant) were exposed in randomly derived quadrants with 6, 8, 10, or 12 J/cm2 at 3 to 4 week intervals for a total of four treatment sessions. RESULTS: An excellent response (> 75% ink removal) was seen in 77% of the black tattoos and more than 95% of the black ink cleared in 11 (28%) of 39 tattoos at 10 to 12 J/cm2 after four treatment sessions. Colored inks were not as effectively removed. Response was related to fluence with greatest improvement noted in the quadrants treated with 10 and 12 J/cm2. No significant side effects, including pigmentary changes or scarring, were noted. Histopathologic examination demonstrated persistence of tattoo ink in clinically clear areas and confirmed the absence of fibrosis and granulomatous changes. CONCLUSION: The Q-switched Nd:YAG laser (1064 nm) effectively treats black tattoos with an excellent cosmetic outcome. Bright colors were minimally responsive to treatment. Higher doses were more effective and equally well tolerated.

Adult↗
PubMed1993

Photodynamic therapy in dermatology: recent developments.

The application of PDT in dermatology has been limited by technical problems, lack of standardized treatment parameters and controlled clinical trials, and cutaneous photosensitivity. PDT requires specially trained personnel and relies on devices that are expensive and difficult to maintain. In North America, PDT is currently performed at only a few centers on an investigational basis. Although a great deal of anecdotal clinical information is available on PDT for treating non-melanoma skin cancer, controlled trials are still needed in order to compare PDT with the highly effective methods already available. PDT may also be useful for a variety of nononcologic dermatoses. New photosensitizers such as BPD-MA, NPe6, and ALA offer the promise of causing significantly less prolonged photosensitivity than the currently available agents; combined with well-designed clinical studies, this will undoubtedly facilitate the acceptance of PDT into standard dermatologic practice.

Dermatology↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1991

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↗