Randomized trial of Internet-based relapse prevention for partially remitted depression.

OBJECTIVE: To investigate whether Internet-based cognitive behaviour therapy (CBT) can prevent relapse in persons with partially remitted major depression after previous treatment. METHOD: Seventy-one women and 13 men (N = 84) with partially remitted major depression after treatment were randomly assigned to either 10 weeks of Internet-based CBT or to a control group. Self-help material was used in combination with e-mail contact with a personal therapist. Monthly self-ratings of depressive symptoms were made, and diagnostic interviews were conducted before and after the treatment period, as well as 6 months later. RESULTS: Significantly fewer participants in the CBT group experienced relapse (4/38 or 10.5%) compared with those in the control group (14/37 or 37.8%). The difference in relapse rates between groups occurred early in the study period and was still apparent after 6 months. A trend towards a larger reduction in depressive symptoms was observed at post-treatment in the participants who received CBT compared with controls. Reduction in depressive symptoms reduced the risk of relapse. A trend towards a higher remission rate was found in the CBT group at the 6 month follow-up. CONCLUSION: Internet-based CBT seems promising in preventing relapse in persons with partially remitted major depression after previous treatment.

AUTOMATIC GENERATION OF FFT FOR TRANSLATIONS OF MULTIPOLE EXPANSIONS IN SPHERICAL HARMONICS.

The fast multipole method (FMM) is an efficient algorithm for calculating electrostatic interactions in molecular simulations and a promising alternative to Ewald summation methods. Translation of multipole expansion in spherical harmonics is the most important operation of the fast multipole method and the fast Fourier transform (FFT) acceleration of this operation is among the fastest methods of improving its performance. The technique relies on highly optimized implementation of fast Fourier transform routines for the desired expansion sizes, which need to incorporate the knowledge of symmetries and zero elements in the input arrays. Here a method is presented for automatic generation of such, highly optimized, routines.

Increased airway responsiveness of a common fragrance component, 3-carene, after skin sensitisation--a study in isolated guinea pig lungs.

Lungs from skin-sensitised and non-sensitised guinea pigs were exposed via the airways to 3-carene (1900 mg/m3) and perfused with buffer containing either autologous plasma or lymphocytes. The experiments were performed in order to investigate the importance of blood components for the increased lung responsiveness seen in skin-sensitised animals. A reduction in lung function was noted in all lungs during 3-carene exposure. There was no difference in the 3-carene response between lungs from skin-sensitised animals versus lungs from non-sensitised animals when the perfusion buffer contained lymphocytes. However, when plasma diluted with buffer was used as perfusion medium, there was a significant enhancement in the response in lungs from sensitised versus lungs from non-sensitised animals. This implies that skin sensitisation increases lung responses to inhaled 3-carene and those components in plasma, and not the lymphocyte fraction, contributes to the observed increased lung responsiveness.

Independent checking of the delivered dose for high-energy X-rays using a hand-held PC.

BACKGROUND AND PURPOSE: The requirements on the delivered dose in radical radiation therapy are extremely high. The dose should be within a few percent and also delivered with high accuracy in space. Vendors and users have successfully managed to implement radiation therapy systems, which are able to achieve these demands with high accuracy and reproducibility. These systems include computerized tomography scanners, treatment planning systems, simulators, treatment machines, and record and verify systems. More and more common are also computer networks to assure data integrity when transferring information between the systems. Even if these systems are commissioned and kept under quality assurance programs to maintain their accuracy, errors may be introduced. Especially, the human factor is an uncontrolled parameter that may introduce errors. Thus, unintentional changes or incorrect handling of data may occur during clinical use of the equipment. Having an independent dose calculation system implemented in the daily quality assurance process may assure a high quality of treatments and avoidance of severe errors. MATERIALS AND METHODS: To accomplish this, a system of equations for calculating the absorbed dose to the prescription point from the set-up information, has been compiled into a dose-calculation engine. The model is based on data completely independent of the treatment planning system (TPS). The fundamental parameter in the dose engine is the linear attenuation coefficient for the primary photons. This parameter can readily be determined experimentally. The dose calculation engine has been programmed into a hand-held PC allowing direct calculation of the dose to the prescription point when the first treatment is delivered to the patient. RESULTS AND CONCLUSION: The model is validated with measurements and is shown to be within +/-1.0% (1 SD). Comparison against a state-of-the-art TPS shows an average difference of 0.3% with a standard deviation of +/-2.1%. An action level covering 95% of the cases has been chosen, i.e. +/-4.0%. Deviations larger than this are with a high probability due to erroneous handling of the patient set-up data. This system has been implemented into the daily clinical quality control program.

Nickel on the Swedish market before the Nickel Directive.

Nickel allergy is by far the most frequent contact allergy, affecting 10-15% of women in the general population, and causing dermatitis and hand eczema. The EU Nickel Directive, aimed at the prevention of nickel allergy, comes fully into force by July 2001. The Directive covers piercing materials, items in contact with the skin, and requirements on resistance to wear. We carried out a study of the prevalence on the market, before the Nickel Directive, of items that release nickel and of nickel in piercing posts. Nickel release, as shown by a positive dimethylglyoxime (DMG) test, was detected in 25% of 725 items intended for direct and prolonged contact with the skin. Of 15 posts intended for use during epithelialization after piercing, 60% contained more than 0.05% nickel. These products do not comply with the requirements of the EU Nickel Directive. It is suggested that experts in contact dermatitis participate in the prevention of nickel allergy by explaining its effects: the r le of skin exposure and which parts of an item are in contact with the skin, and the crucial question of nickel release versus nickel content.

On beam quality and stopping power ratios for high-energy x-rays.

The aim of this work is to quantitatively compare two commonly used beam quality indices, IPR(20/10) and %dd(10)x, with respect to their ability to predict stopping power ratios (water to air), s(w,air), for high-energy x-rays. In particular, effects due to a varied amount of filtration of the photon beam will be studied. A new method for characterizing beam quality is also presented, where the information we strive to obtain is the moments of the spectral distribution. We will show how the moments enter into a general description of the transmission curve and that it is possible to correlate the moments to s(w,air) with a unique and simple relationship. Comparisons with TPR(20/10) and %dd(10), show that the moments are well suited for beam quality specification in terms of choosing the correct s(w,air).

Transmission measurements in air using the ESTRO mini-phantom.

The aim of this work is to study the possibility of using the ESTRO mini-phantom for transmission measurements of primary kerma in water at a point free in air. We discuss in-air measurements in general, with special attention given to in-air equivalent measurements using a water equivalent mini-phantom. The study includes four different photon energies (4, 6, 10 and 18 MV), where scoring of dose and primary kerma inside a mini-phantom in narrow beam geometry is performed with the Monte Carlo code EGS4. The results reveal that relative measurements (i.e. with and without a water absorber present) at 10 cm depth in a mini-phantom do not represent the variation of primary kerma in water at a point free in air (deviations as large as 7% at 4 MV are observed). Minimum deviations are obtained at depths somewhat larger than the depth of dose maximum. The observed deviations are due to a considerable beam hardening in the water absorber, which changes the amount of attenuation and scatter inside the mini-phantom.

A method for measuring dermal exposure to multifunctional acrylates.

UV-curable acrylates are used increasingly for coating wood surfaces in the furniture industry. One of the active components, tripropylene glycol diacrylate (TPGDA), is known to be both an allergen and irritant to the skin. Methods to measure dermal exposure to skin irritants and allergens, such as acrylates, are insufficient for exposure assessment and there is none for this compound. The aim of this investigation was to develop a skin and surface sampling method, based on tape stripping, and a gas chromatographic method for quantitative analysis for assessing occupational skin exposure to multifunctional acrylates. Twelve adhesives were tested for their efficiency to remove TPGDA and UV-coating from a glass surface, the skin of guinea pigs and human volunteers employing the tape-stripping method in order to find the best performing tape. Variables that affect removal efficiency such as the applied dose and its retention time on the skin, tape adhesion time on the skin, and the number of strippings required to detect the contaminant from the skin were studied. Fixomull tape performed the best during sampling and analysis and had the most consistent removal efficiencies for the studied substances. The average removal efficiency with a single stripping at the 2 microliters TPGDA exposed skin sites was 85% (RSD = 14.1), and for UV-resin exposed sites 63% (RSD = 20.2). The results indicated that this method can be used for measuring dermal exposure to multifunctional acrylates efficiently, accurately, and economically. This method provides a sensitive and powerful tool for the assessment of dermal exposure to multifunctional acrylates both from the skin and from other contaminated surfaces in occupational field settings.

Off-axis primary-dose measurements using a mini-phantom.

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head-scatter factor) and off-axis position (primary off-axis ratio). These parameters are normally measured "in air" with a build-up cap thick enough to generate full dose build-up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it has been recommended that head-scatter measurements are carried out using a mini-phantom rather than a conventional build-up cap. Due to the volume of the mini-phantom, the effects from attenuation and scatter are not negligible. In relative head-scatter measurements these effects cancel and the head scatter is thus a good representation of the variation of the incident photon beam with collimator setting. However, in off-axis measurements, attenuation and scatter conditions vary due to beam softening and do not cancel in the calculation of the primary off-axis ratio. The purpose of the present work was to estimate the effects from attenuation and phantom scatter in order to determine their influence on primary off-axis ratio measurements. We have characterized the off-axis beam-softening effect by means of narrow-beam transmission measurements to obtain the effective attenuation coefficient as a function of off-axis position. We then used a semi-analytical expression for the phantom-scatter calculation that depends solely on this attenuation coefficient. The derived formalism for relative "in air" measurements using a mini-phantom is clear and consistent, which enables the user to separately calculate the effects from scatter and attenuation. For the investigated beam qualities, 6 and 18 MV, our results indicate that the effects from attenuation and scatter in the mini-phantom nearly cancel (the combined effect is less than 1%) within 12.5 cm from the central beam axis. Thus, no correction is needed when the primary off-axis ratio is measured with a mini-phantom.

Gas chromatographic determination of butoxyacetic acid in human blood after exposure to 2-butoxyethanol.

Venous blood samples from five male volunteers exposed to 20 ppm 2-butoxyethanol (BE) for 2 h were collected at 0, 2, 4, and 6 h from the start of exposure and analyzed by gas chromatography after simultaneous ion-pair extraction and derivatization with pentafluorobenzyl bromide. Butoxyacetic acid (BAA), a major metabolite of BE, was found in all samples except those collected prior to exposure. This is the first time to our knowledge that the analysis of BAA in human blood has been reported. Concentrations of BAA in blood ranged from 22 to 60 microM. These concentrations were about two orders of magnitude lower than those causing swelling and hemolysis of human erythrocytes in vitro. The BAA blood level peaked after 2-4 h. The decrease between 4 and 6 h indicates an average half-time of BAA in blood of about 4 h, which is in accordance with previously observed half-times in urine. The low renal clearance of BAA (22-39 ml/min) indicates extensive binding to blood proteins and poor tubular secretion of the substance. Binding of BAA to blood components is also indicated by the low apparent volume of distribution of approximately 15l.

Injection device for pharmaco-angiography.

A device for injections of vasoactive agents at angiography connected with an injector for contrast medium and a film changer is described. It enables the examination to be performed according to predetermined data with a high degree of reproducibility. It lends itself particularly to experimental investigations of pharmacologic effects within various vascular areas.