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Biomedical subjects

B L Diffey

Publications and source records attributed to B L Diffey.

At least 73 records · Page 4Linked to original sources
PubMed1987

The onset of ultraviolet erythema.

The onset of erythema induced by UVB and by UVC radiation was monitored in two subjects using a reflectance instrument. It was shown that vasodilation occurred some time before erythema became visible, even with small exposure doses of UVB or UVC, after which visible erythema was not apparent for several hours. In one subject, vasodilation was detected very shortly after irradiation and may have even begun during irradiation. In the other subject vasodilation was detected later at most exposure doses, but still some time before erythema became visible. We conclude that the so-called 'latent period' between irradiation and appearance of erythema is an artificial concept arising from the insensitivity of the eye.

Dose-Response Relationship, Radiation↗
PubMed1987

A comparison of dosimeters used for solar ultraviolet radiometry.

Radiometric measurements of terrestrial sunlight using three different types of broad-band dosimeters were compared with equivalent integrated quantities obtained from simultaneous spectroradiometric measurements. Measurements were made at Durham, UK (55 degrees N) during one day in mid-summer and one day in the autumn. By this means it was possible to encompass a wide range of ultraviolet irradiances. There was close agreement between UV-A irradiance measured using a broad-band radiometer and determined spectroradiometrically over the whole range of irradiances when allowance was made for the spectral sensitivity of the UV-A radiometer. The agreement between erythemally-effective irradiance determined spectroradiometrically and the response of a Robertson-Berger meter showed some non-linearity due to the mismatch between the erythema action spectrum and spectral response of the sensor. There was a similar disparity in agreement between erythemally-effective dose determined spectroradiometrically and the response of polysulphone film for similar reasons. Nevertheless it is concluded that if these latter two dosimeters are calibrated using sunlight, or a solar simulator, as the source, they can yield data which are sufficiently reliable for many applications.

Radiation Dosage↗
PubMed1987

Evaluation of subjective assessment of liver function from radionuclide images.

The appearance of non-hepatic uptake in 99Tcm-colloid images is an important indicator of poor liver function. We undertook this study to evaluate the ability of experienced observers to assess liver function from radionuclide images. A simple model was used to simulate the changing distribution of 99Tcm-colloid in the liver, spleen and bone marrow as the liver function and mass were varied. Suitable images of these three organs were isolated from real studies and used as "templates" to create realistic simulated 99Tcm-colloid images, with the count densities of liver, spleen and bone marrow determined by the model. These images were presented in random order to several observers, who were asked to assess liver function. Comparison of the estimated with the true function shows that visual assessment is systematically inaccurate, with underestimation of poor function and overestimation of good function. It is also imprecise, especially for livers with only midly impaired function. Observers were also affected by changing liver mass and were more likely to judge small livers to be abnormal. We suggest that objective assessment using a quantitative technique should be used as an adjunct to visual inspection for the evaluation of liver function.

Humans↗
PubMed1987

PUVA-induced blisters, complement deposition, and damage to the dermoepidermal junction.

We followed the course of 56 patients receiving psoralen plus long-wave ultraviolet light (PUVA) therapy. Nonhemorrhagic blisters developed on clinically normal skin on the limbs of seven patients. Seeming to be related to friction and trauma, the blisters form as a result of damage to the basal and suprabasal layers. Perilesional skin specimens from all blistered patients contained granular deposits of C3 at the dermoepidermal junction, around the upper dermal blood vessels, or at both sites. The average time for initiation and complete formation of suction blisters was measured in 51 patients at different stages during the course of PUVA treatment. Blister separation was in the lamina lucida, with the pemphigoid antigen in the roof while the blister floor contained the lamina densa, laminin, and type IV collagen. This impaired dermoepidermal adhesion was a general phenomenon that occurred in all PUVA-treated patients. The mechanism remains to be determined.

Adult↗
PubMed1987

A new type of erythemal radiometer for use in phototherapy.

A new type of radiometer is described which, when exposed to ultraviolet radiation lamps, displays the time required to achieve a minimal erythema. The radiometer incorporates a switch on the front panel to allow for the erythemal sensitivity of different sun-reactive skin types. The instrument was exposed to a number of different lamp/filter combinations commonly used for phototherapy, and in each case indicated an exposure time to within +/- 10% of that determined by combining the spectral irradiance with the erythema action spectrum. Good agreement was also obtained between the exposure times necessary to achieve 24 h minimal erythema in Caucasian subjects of different sun-reactive skin types, and those exposure times predicted by the erythemal radiometer.

Erythema↗
PubMed1987

PUVA lentigines.

Explore the source record for details and available documents.

Dose-Response Relationship, Radiation↗
PubMed1987

Analysis of the risk of skin cancer from sunlight and solaria in subjects living in northern Europe.

The risk of non-melanoma skin cancer in northern Europeans who indulge in sunbathing or use a UVA solarium was estimated using a mathematical model of skin cancer incidence that makes allowance for childhood, occupational and recreational sun exposure. This model demonstrates that the cumulative incidence of skin cancer in indoor workers is about 2-3% by the age of 70, yet this risk can increase 5-fold if they indulge in a two-week sunbathing vacation each summer. The use of a UVA solarium is also shown to increase the risk of skin cancer. Because risk increases with the approximate square of annual solarium exposure, it is not possible to define a 'safe' level of exposure. Instead, it is shown that weekly use of a UVA solarium from age 20 until middle age (40-50) gives a relative cumulative incidence of 1.3 compared with non-users of sun beds and sun canopies. The risk begins to increase rapidly for more frequent use, particularly when solaria are used in combination with sunbathing.

Adolescent↗
PubMed1986

Status of ultraviolet A dosimetry in methoxsalen plus ultraviolet A therapy.

The carcinogenic risk of methoxsalen plus ultraviolet A treatment (PUVA) is almost certainly related to the cumulative UVA exposure dose. A reliable estimate of UVA dose is a major component, therefore, in determining the long-term safety of this treatment modality. Thirty-one UVA meters from twenty-nine different PUVA treatment centers were compared with a calibrated UVA meter. The results inferred that 95% of UVA meters used in PUVA centers are reading between 57% and 159% of the true UVA irradiance, a factor of 2.8 in relative sensitivity. This wide variation in accuracy between the UVA meters gives cause for concern. These variations were attributed to differences in calibration procedure, optical properties of the sensors, and, most importantly, poor quality control by the manufacturers. The situation that appears to have existed since the introduction of PUVA therapy can be improved only if dermatologists agree that the present inaccurate and uncertain approach to UVA measurements is unsatisfactory. Manufacturers of UVA meters should be encouraged to provide instruments as reliable as the dosimeters used in radiotherapy, in which the prescribed dose is probably within 5% of the true value. Ideally, a standard type of UVA meter with appropriate physical properties and an agreed calibration procedure should be used by all centers engaged in PUVA treatment.

Humans↗
PubMed1986

The erythemal response to ultraviolet radiation in subjects with polymorphic light eruption.

A reflectance instrument was used to measure objectively the erythemal response to UV-B and UV-C radiation in subjects with polymorphic light eruption. The characteristics of the dose-response curves obtained for each quality of ultraviolet radiation were significantly different, but were essentially indistinguishable from the comparable dose-response curves measured previously in normal subjects. It is concluded that in this photodermatosis the chromophore(s) and mediator(s) of delayed (24 h) ultraviolet-induced erythema are identical to those in normal skin.

Adult↗
PubMed1986

Occupational exposure to ultraviolet radiation in dermatology departments.

The ultraviolet radiation (UVR) doses received by staff who are occupationally exposed to artificial sources of UVR found in dermatology departments have been measured using personal UV monitors. The results show that staff may receive actinic (UVB and UVC) doses which are in excess of recommended maximum permissible limits for occupational exposure, but that the UVA doses are well within these limits.

Dermatology↗
PubMed1986

Use of UV-A sunbeds for cosmetic tanning.

A survey has been carried out of people using UV-A sunbeds at commercial premises in the U.K. The degree of tan achieved was found to be closely related to the subject's ability to tan in sunlight, and subjects who burnt easily in sunlight were most at risk of developing erythema after using a sunbed. Side-effects, particularly itching, were common. The prevalence of itching, nausea and skin rashes were higher in women taking oral contraceptives than in women on no medication. Although long-term quantitative estimates of the risks of UV-A sunbed use (such as skin ageing and skin cancer) are unknown, it is recommended that individuals who do not tan or tan poorly should be discouraged from using sunbeds.

Adolescent↗
PubMed1986

A quantitative study of the effect of topical indomethacin on cutaneous erythema induced by UVB and UVC radiation.

The effect of indomethacin gel on UVB and UVC erythema was assessed objectively using a reflectance instrument. When indomethacin was applied immediately after irradiation, UVR (ultraviolet radiation) dose-dependent suppression of erythema was demonstrated for both wavelengths until 36 h after irradiation when both indomethacin and control gel base-treated sites were equally erythematous. Suppression of erythema also occurred when application of indomethacin was delayed until 24 h after irradiation, showing that for both wavelengths prostaglandin synthesis remains increased throughout this period. The degree of suppression at any time, however, was no greater than that achieved by a single application immediately after irradiation, indicating that the eventual equal erythema of indomethacin and gel base-treated sites was not due to tachyphylaxis or inadequate dosage. Construction of dose-response curves for the indomethacin-responsive and indomethacin-unresponsive components of erythema shows that in human skin the difference in erythemal response to UVB and UVC radiation is not due to the formation of different mediators at these wavelengths.

Administration, Topical↗