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Biomedical subjects

J W Pickering

Publications and source records attributed to J W Pickering.

At least 19 recordsLinked to original sources
PubMed1998

Comparative evaluation of three recombinant antigen-based enzyme immunoassays for detection of IgM and IgG antibodies to human parvovirus B19.

BACKGROUND: Diagnosis of acute and past infection with parvovirus B19 is based on detection of IgM and IgG antibodies. OBJECTIVES: To evaluate two commercial recombinant antigen-based enzyme immunoassay (EIA) test kits for detection of IgM and IgG antibodies to parvovirus B19 and to compare the commercial EIAs to in-house EIA test procedures. STUDY DESIGN: A panel of 121 sera was used to compare the three IgM EIAs. The panel included 84 sera submitted for parvovirus B19 testing and 37 sera that were IgM positive for other viral pathogens. The same serum panel plus an additional 14 sera submitted for B19 testing was used to compare the three IgG EIAs. The commercial EIAs were performed according to manufacturers' instructions. Using the in-house EIA test procedures as the reference, sensitivity and specificity for each of the commercial EIAs was determined. RESULTS: The commercial B19 IgM EIAs showed agreements of 95.0 and 93.4% to the in-house IgM EIA. Compared to the in-house B19 IgM EIA, the commercial B19 IgM EIAs were 97.4 and 97.5% sensitive, respectively. Specificities were 93.5 and 91.4%, respectively. Sensitivities for the commercial IgG EIAs, compared to in-house IgG EIA, were 88.0 and 85.2%, respectively, and specificities were 94.1 and 98.0%. CONCLUSION: We found that the commercial parvovirus B19 IgM and IgG EIAs are comparable to standard in-house EIAs and are suitable for testing for B19 antibodies in human sera.

Antibodies, Viral↗
PubMed1998

Premarket evaluation of a commercial glycoprotein G-based enzyme immunoassay for herpes simplex virus type-specific antibodies.

A new commercial glycoprotein G-based enzyme immunoassay (gG-EIA) was compared with Western blotting (WB) for detection of herpes simplex virus type 1 (HSV-1) or HSV-2 type-specific antibodies in 193 serum samples. Sensitivity for HSV-1 was 95%; specificity was 96%. Sensitivity for HSV-2 was 98%; specificity was 97%. Twelve of 13 serum samples with equivocal gG-EIA results were serotyped by WB.

Antibodies, Viral↗
PubMed1997

In vitro double-integrating-sphere optical properties of tissues between 630 and 1064 nm.

The optical properties (absorption and scattering coefficients and the scattering anisotropy factor) were measured in vitro for cartilage, liver, lung, muscle, myocardium, skin, and tumour (colon adenocarcinoma CC 531) at 630, 632.8, 790, 850 and 1064 nm. Rabbits, rats, piglets, goats, and dogs were used to obtain the tissues. A double-integrating-sphere setup with an intervening sample was used to determine the reflectance, and the diffuse and collimated transmittances of the sample. The inverse adding-doubling algorithm was used to determine the optical properties from the measurements. The overall results were comparable to those available in the literature, although only limited data are available at 790-850 nm. The results were reproducible for a specific sample at a specific wavelength. However, when comparing the results of different samples of the same tissue or different lasers with approximately the same wavelength (e.g. argon dye laser at 630 nm and HeNe laser at 632.8 nm) variations are large. We believe these variations in optical properties should be explained by biological variations of the tissues. In conclusion, we report on an extensive set of in vitro absorption and scattering properties of tissues measured with the same equipment and software, and by the same group. Although the accuracy of the method requires further improvement, it is highly likely that the other existing data in the literature have a similar level of accuracy.

Absorption↗
PubMed1995

Wavelengths for laser treatment of port wine stains and telangiectasia.

BACKGROUND AND OBJECTIVE: This report presents analytical modelling of the influence of wavelength on the amount of volumetric rate of heat produced in dermal blood vessels by millisecond laser radiation. STUDY DESIGN/MATERIALS AND METHODS: A new anatomical model is proposed that represents port wine stains as well as telangiectatic lesions. It consists of a target blood vessel, representing the deepest dermal blood vessel that requires irreversible injury, and a layer of whole blood, representing all other dermal blood vessels above the target vessel. The laser light that interacts with the blood vessels is assumed to be diffuse. Selective photothermolysis is the basis for the analysis. We consider wavelengths between 577 nm and 600 nm, the argon laser wavelengths at 488/515 nm, and the frequency doubled Nd:YAG laser wavelength at 532 nm. RESULTS: The rate of volumetric heat production of absorbed laser light in the target blood vessel is expressed analytically as a function of blood absorption, the concentration of additional dermal blood, and the depth of the target vessel. CONCLUSION: The model explains why 585 nm is a good compromise for treating port wine stains that vary widely in number of dermal blood vessels. It predicts that wavelengths between 577 nm and 582 nm are excellent for the treatment of port wine stains in young children, and it suggests a possible explanation as to why the argon laser is sometimes said to be capable of treating dark mature port wine stains. The copper vapour laser wavelength at 578 nm, and the frequency doubled Nd:YAG laser wavelength at 532 nm, are predicted to be suitable for the treatment of port wine stains that contain, respectively, a small to moderate and a moderate number of dermal blood vessels. When laser beam spotsize becomes smaller, the best wavelength for producing maximal rate of heat in the target vessel is predicted to shift to 577 nm.

Animals↗
PubMed1995

Ultrastructural alterations in heated canine myocardium.

BACKGROUND AND OBJECTIVE: The anisotropy factor of light scattering (g) (wavelength 632.8 nm) in heated myocardium decreases as a function of temperature, suggesting, on the basis of Mie theory of light scattering, formation of an increasing number of particles with diameters smaller than the incident wavelength. STUDY DESIGN/MATERIALS AND METHODS: To test this hypothesis, fresh myocardium was heated at constant temperatures between 37 degrees C and 75 degrees C for 1,000 s. Changes in size and number of granules generated by disintegrating organelles and sarcomeres were studied as a function of temperature by transmission electron microscopy, planimetry and particle counting. RESULTS: The mitochondria started to disintegrate at 45 degrees C and myofibrils between 45 degrees C and 50 degrees C into increasing numbers of small electron dense granules (diameter 50-200 nm), which correlated with the observed decrease of g from 0.93 +/- 0.02 (at room temperature to 45 degrees C) to 0.77 +/- 0.05 at 75 degrees C. CONCLUSION: The scattering coefficient microseconds of 161 +/- 33 cm-1 did not change significantly.

Actin Cytoskeleton↗
PubMed1994

Continuous measurement of the heat-induced changes in the optical properties (at 1,064 nm) of rat liver.

The radiative transfer optical properties (absorption coefficient, scattering coefficient, and anisotropy of scattering) of slowly heated rat liver have been measured at 1,064 nm. Continuous measurements were made using double-integrating spheres and collimated illumination of the sample for up to 5,000 seconds heating with equilibrium temperatures of 48 degrees, 52 degrees, and 58 degrees C. Generally, the scattering increased, and the absorption and anistropy decreased at rates dependent on the heating temperatures. However, there was a large variability between samples.

Absorption↗
PubMed1993

Optical properties of rat liver and tumor at 633 nm and 1064 nm: photofrin enhances scattering.

Predicting the effects of photodynamic therapy (PDT) and Nd: YAG laser coagulation requires knowledge of the light distribution in tumor and surrounding tissue. Therefore, absorption and scattering coefficients and the average cosine of the scattering angle (the anisotropy factor) were measured in rat liver and tumor at 632.8 and 1064 nm. A syngenic colon adenocarcinoma CC531 was implanted subcutaneously in two groups of 7 Wag/Rij rats. In one group Photofrin was administered 5 mg/kg intravenously 48 h before determination of optical properties. Two months after inoculation, samples were taken from tumor and liver and optical properties determined using indirect methods with two integrating spheres. The absorption coefficient was larger in liver than in tumor at 632.8 nm (P < 0.0005), whereas the scattering coefficient was larger in tumor than in liver at 1,064 nm (P < 0.05). Addition of Photofrin increased the scattering coefficient in liver and in tumor at both wavelengths (P < 0.025) and decreased the anisotropy in tumor (P < 0.025), suggesting that for modelling the dosimetry of PDT the optical properties of photosensitized tissue should be used.

Absorption↗
PubMed1993

Modeling the color perception of port wine stains and its relation to the depth of laser coagulated blood vessels.

To find the maximal depth of an ecstatic vessel in the dermis that contributes to the abnormal color of a port wine stain (PWS), "normal" and "laser treated PWS skin" are modeled, respectively, as a two-layer plane parallel geometry consisting of an epidermis and a dermis, and as a three-layer geometry consisting of an epidermis, a dermis without additional blood (the "treated" part of the stain, assumed identical to the "normal" dermis), and a layer of dermis containing 5% or 10% of blood per volume (the untreated part of the PWS). Spectral remittances were calculated for various wavelengths using the diffusion approximation to the transport equation for light propagation. These remittances were transformed into the CIE 1976 (L*a*b*)-color system. Color differences between "normal" and PWS skin as a function of the dermal depth of "injured" ecstatic blood vessels were calculated. The maximal depth where ecstatic blood vessels just contribute to the abnormal PWS color is predicted as 0.9 mm for a "normally" pigmented epidermis (60 microns thick) and a 5% or 10% blood per volume content. For a darker pigmented epidermis (60 microns thickness) and again at both 5% and 10% blood per volume content, this depth was found to be 0.8 mm.

Blood↗
PubMed1993

Defining purpura.

Explore the source record for details and available documents.

Hemangioma↗
PubMed1992

Optical property changes as a result of protein denature in albumen and yolk.

Heat-induced changes in the scattering and absorbing properties of tissue begin with the denaturation of protein. Using egg albumen and egg yolk as tissue phantoms, the changes in absorption and scattering coefficients and the average cosine of the scattering angle have been quantified from 350 to 850 nm for heating corresponding to an empirical damage parameter from 3.7 to 1430 (albumen) and from 0.067 to 28 (yolk). In addition to being useful for modelling the response of tissue to laser light, the changes in optical properties yield information on the particle size distribution in the phantoms. For a low damage parameter the albumen has a large percentage of small, so-called Rayleigh scattering, particles owing to the initial denaturation of the protein. As the damage parameter increases, the percentage of these particles decreases. In the yolk, the effect of denaturation of proteins on the scattering characteristics is still present but less pronounced, because of the initial highly scattering nature of the tissue and perhaps to other rate processes that also occur.

Animals↗
PubMed1992

Monoline argon laser (514 nm) treatment of benign pigmented lesions with long pulse lengths.

A dichroic filter was adjusted in order to make use of the green line of an argon laser for the treatment of pigmented lesions (actinic and senile lentigo, ephelis, café-au-lait marks and spilus nevus). Using a power of 1.5 W, a spot size of 0.5 mm and pulse lengths of 200 or 300 ms, satisfactory elimination of 620 pigmented cutaneous lesions was achieved. Although the pulse lengths used were much longer than the thermal relaxation time of the melanosomes, the histology after treatment showed little damage of adjacent structures. Good restoration of the epidermis and a return of normal pigmentation led to excellent cosmetic results, with few complications.

Cicatrix↗
PubMed1991

Laser beam diameter for port wine stain treatment.

Optimal port wine stain treatment requires the selective absorption of light by the ectatic blood vessels. We investigated whether deeper blood vessels can be coagulated, without damaging other cutaneous structures, by varying the laser beam diameter. The penetration of the light was simulated with a random walk (Monte Carlo) program. Scattering of the light plays a major role: practically all light that is absorbed in a blood vessel in the dermis is scattered light. In the epidermis, where the distribution is more centered, a larger beam diameter does not increase the energy density as much as deeper within the dermis where the blood vessels lie and where the light is totally diffuse. Increasing the laser beam diameter from 200 microns to 1 mm or more, makes a typical blood vessel absorb 2.5 times more energy, while the energy absorbed by the epidermis remains the same. The larger the laser beam diameter the better the treatment.

Absorption↗
PubMed1991

A computer controlled scanner for the laser treatment of vascular lesions and hyperpigmentation.

A computer controlled scanner has been used with a copper vapour laser for the treatment of vascular lesions and hyperpigmented lesions. The computer controls the position and speed of travel of the laser spot during treatment. The illumination time is adjustable with a minimum of 1 ms. The light from the laser is scanned over the lesion so that the lesion is 'painted in' in a raster-like scan of arbitrary shape and produces a series of parallel lines 0.6 mm apart.

Computers↗
PubMed1991

The facial distribution of port wine stains on patients presenting for laser treatment.

During a 2-year period, 232 patients with port wine stains presented for laser treatment. They were analyzed for the position of the port wine stain with respect to the right and left ophthalmic, maxillary, and mandibular divisions of cranial nerve V and the right and left cervical plexus. Fifty-one percent of the facial lesions were confined to either the right or left maxillary division, and 72% of the lesions were confined to just one of the eight nerve regions; 5.9% of the lesions occupied regions on both sides of the face, whereas 49.8% were confined to the right side and 44.3% to the left. In comparison with a group of 103 patients studied by Ohtsuka of Japan, there appeared to be significantly more patients in the maxillary division (p less than 0.0001) and significantly fewer patients in the ophthalmic division and in the combination of ophthalmic and maxillary divisions (p less than 0.00001).

Adolescent↗
PubMed1990

Copper vapour laser treatment of port-wine stains and other vascular malformations.

Over a 2-year period more than 1350 treatment sessions have been conducted with yellow 578 nm light from a copper vapour laser on a variety of vascular malformations. Of these sessions half were of port-wine stains, from 297 patients. The light is applied by scanning a 1 mm optical fibre approximately 2 mm above the lesion along the lines of Langer. We use a maximum scan rate of 3 s/cm2, which is the highest rate at which minimal blanching can be produced. Up to 6.5 watts of light has been used, and a typical energy fluence is 20 to 30 J/cm2. Topical melanin suppressing creams are used before and after treatment, in order to maximise the effectiveness of the treatment. Non-vasoconstricting anaesthetics are always used. Repeat treatments are 3 months apart. The scan rate we used was directly correlated with the light intensity. The degree to which the colour of the port-wine stains lightened after the first treatment was also well correlated with the scan rate (p less than 0.0005). The faster the scan rate, the greater the colour reduction. This provides some supporting evidence for the short illumination time that theoretical models have indicated as "ideal". The lightening was more marked for patients whose lesion colour was initially dark (p less than 0.0005). Those whose skin had a high melanin content (Maori, Polynesian and Asian) responded more slowly than others. Thirty-six patients have had a greater than 70% reduction in the size of their lesions after an average of four treatments. Ten patients have responded poorly after at least four treatments (10% of all those who have had four or more treatments). The occurrence of scarring, hyperpigmentation and hypopigmentation was low in comparison with that reported previously from the green light of argon ion lasers.

Adolescent↗