Attenuation compensation in cerebral 3D PET: effect of the attenuation map on absolute and relative quantitation

It is generally well accepted that transmission (TX)-based non-uniform attenuation correction can supply more accurate absolute quantification; however, whether it provides additional benefits in routine clinical diagnosis based on qualitative interpretation of 3D brain positron emission tomography (PET) images is still the subject of debate. The aim of this study was to compare the effect of the two major classes of method for determining the attenuation map, i.e. uniform versus non-uniform, using clinical studies based on qualitative assessment as well as absolute and relative quantitative volume of interest-based analysis. We investigated the effect of six different methods for determining the patient-specific attenuation map. The first method, referred to as the uniform fit-ellipse method (UFEM), approximates the outline of the head by an ellipse assuming a constant linear attenuation factor (=0.096 cm^–1) for soft tissue. The second, referred to as the automated contour detection method (ACDM), estimates the outline of the head from the emission sinogram. Attenuation of the skull is accounted for by assuming a constant uniform skull thickness (0.45 cm) within the estimated shape and the correct value (0.151 cm^–1) is used. The usual measured transmission method using caesium-137 single-photon sources was used without (MTM) and with segmentation of the TX data (STM). These techniques were finally compared with the segmented magnetic resonance imaging method (SMM) and an implementation of the inferring attenuation distributions method (IADM) based on the digital Zubal head atlas. Several image quality parameters were compared, including absolute and relative quantification indexes, and the correlation between them was checked. The qualitative evaluation showed no significant differences between the different attenuation correction techniques as assessed by expert physicians, with the exception of ACDM, which generated artefacts in the upper edges of the head. The mean squared error between the different attenuation maps was also larger when using this latter method owing to the fact that the current implementation of the method significantly overestimated the head contours on the external slices. Correlation between the mean regional cerebral glucose metabolism (rCGM) values obtained with the various attenuation correction methods and those obtained with the gold standard (MTM) was good, except in the case of ACDM (R ²=0.54). The STM and SMM methods showed the best correlation (R ²=0.90) and the regression lines agreed well with the line of identity. Relative differences in mean rCGM values were in general less than 8%. Nevertheless, ANOVA results showed statistically significant differences between the different methods for some regions of the brain. It is concluded that the attenuation map influences both absolute and relative quantitation in cerebral 3D PET. Transmission-less attenuation correction results in a reduced radiation dose and makes a dramatic difference in acquisition time, allowing increased patient throughput.     

Zur operativen Indikation beim intraossären Kalkaneuslipom

Intraosseous lipomas represent a small number of benign bone tumors with incidence rates of approximately 0.1%. In about 15% these neoplasias are localized within the calcaneus, mostly at Ward's triangle. The tumors usually remain clinically inapparent and diagnosis is often obtained incidentally. Although CT scan and MRI provide specific and sensitive diagnostic tools that can distinguish morphology and dignity, surgical treatment is not standardized yet. In conjunction with a case report, we summarize and critically compare current treatment strategies.     

The expected number of hospitalisations and beds needed due to pandemic influenza on a regional level in the Netherlands

In order to minimise the effects of a potential influenza pandemic on the population, regional authorities in the Netherlands are in the process of development of a plan to be prepared to cope with mass illness and to ensure health care services. The objective of this study is to calculate the expected numbers of hospitalisations and the maximum number of beds needed per day on a regional level. As many uncertainties are involved in this type of studies, we have performed a scenario analysis of the expected number of hospitalisations and beds needed during an influenza pandemic. The analysis gives insight into the impact of the pandemic in terms of how many will be hospitalised, how many beds are needed during the pandemic and in the effect of a possible intervention by therapeutic use of antivirals in terms of hospitalisations and beds needed. It can be concluded that our scenario analysis will be helpful in designing and planning on a regional level.     

The interrelationship of psychosocial risk factors for coronary artery disease in a working population: do we measure distinct or overlapping psychological concepts?

There is growing evidence that psychosocial factors contribute to the risk of coronary artery disease. Commonly used psychometric scales share several features leading to questions about whether they reflect distinguishable concepts. Study participants were 822 employees of the Augsburg Cohort Study (mean age 40 years, 89% men). The authors analyzed the interrelationship between the following psychosocial measures by applying Pearson correlations and factor analysis to the Hospital Anxiety and Depression Scale (HADS), Type D Personality (DS14), the Maastricht Vital Exhaustion Questionnaire (VE), Social Support (F-SozU), the SF12 Health Survey, and Effort-Reward Imbalance. Although the full correlation matrix revealed low to medium associations supporting the notion that the applied psychometric scales show some conceptual overlap, factor analyses resulted in 13 distinguishable and interpretable factors, considerably reflecting the original psychometric scales. This strengthens the assumption that the psychometric scales used constitute distinct psychological concepts, in particular, depressive symptomatology and negative affectivity versus vital exhaustion.     

Epidemiology of eye injuries in Abidjanian children

Eye injuries, most of them preventable, are particularly severe in Africa, because of the risks of infection and delay in treatment. We report a 16-month (March 1997-June 1998) prospective observational survey of eye injuries in children up to the age of 15 years at Treichville-Abidjan University Hospital. During this period, 62 children were treated for these injuries. Ocular traumas represented 4% (n = 245) of new admissions in ophthalmology, and 29% of these injuries occurred in children. The sex ratio was 5:2 boys to girls, and their mean age was 8.66 +/- 3.56 years. Eye injuries occurred most often during play (84%, n = 52). More than 85% (n = 53) of children were alone or without adult supervision at the time of the injury. The causal agent was most often wood (35%) followed by metal (29%). The mean time from injury to hospital admission was 1.8 +/- 0.77 day. Only 19% of patients were admitted the day of injury. Most patients (66%) first sought treatment in a primary care centre. More than 70% (n = 44) of injuries necessitated hospitalisation. Open eyeball wounds were the most common injury (53%) and were associated with endophthalmitis in 16%. The mean recovery of visual acuity was 0.1. At admission, 40 of the injured eyes (64.5%) had monocular blindness; six recovered, for a final blindness rate of 55%. Injuries associated with wooden objects had a final blindness rate of 77% and play-related injuries 63%. The primary posttraumatic sequelae were corneal scars. Eyeball phthysis (14.5%) was secondary to 8 open wounds of the eyeball and one postcontusion retinal detachment. Eye injuries remain a major cause of monocular blindness in children in Cote d'Ivoire. Most of them can be prevented by relatively simple measures including supervision of children and rapid hospitalisation when injury occurs.     

A method for assessing occupational dermal exposure to permanent hair dyes

Hairdressers have an increased risk of developing occupational skin diseases due to exposure to skin irritants and sensitizers. In the present work a method of assessing dermal exposure to permanent hair dyes was developed. The sampling performance characteristics of hand wash sampling with bag rinsing were studied for five hair dye compounds. The effect of residence time, sample load and different matrices were studied. Thirty volunteers were exposed to a reference solution of these compounds and to commercial hair dye products. The sampling efficiency after 5 min residence time was between 70 and 90% for the dye components in the hair dye products. Sampling efficiency decreases with increasing residence time, making the time of sampling an important factor. Hand wash sampling should be performed as soon as possible after the work task of interest. We conclude that the sampling efficiency is adequate for measurements of dermal exposure to permanent hair dyes. Hand wash sampling with bag rinsing is a useful tool for field studies of dermal exposure assessment in hairdressers.     

Prevalence of distress and symptom severity from the lower urinary tract in men: a population-based study with the DAN-PSS questionnaire

Background. Lower urinary tract symptoms (LUTS) are a commonand costly public health issue. The prevalence varies greatlyin published reports. The distress caused by each symptom isimportant to assess the primary care required before therapeuticdecisions or a referral to an urologist are made. Objectives. LUTS are highly prevalent in men, but less is knownregarding the distress caused by each symptom. The aim of thisstudy was to examine symptom severity and different levels ofdistress using the Danish Prostatic Symptom Score (DAN-PSS)questionnaire in men affected by symptoms from the lower urinarytract. Methods. The study included all men aged 41–81 years (n= 504) that, 12 months earlier in a population-based survey,had reported stress incontinence, urgency or post-micturitiondribbling in a postal questionnaire. The DAN-PSS questionnairewas used to measure severity and distress from LUTS. Results. In total, 311 (80%) of the 387 responders who reportedat least one symptom experienced some level of distress. Themost distressing symptom overall was urinary incontinence. Nineof 10 men with storage symptoms (stress, urge and ‘other’urinary incontinence) reported distress even if the symptomoccurred only seldom. Moreover, two-thirds of the men with themost frequent symptom, post-micturition dribbling, characterizedtheir symptom as moderate or severe; the most distressing voidingsymptom was weak stream. In general, LUTS were well tolerated. Conclusion. Urge incontinence was the most distressing LUTSeven when occurring only seldom. The DAN-PSS questionnaire maybe a potentially useful tool for health professionals to identifypatients with pronounced distress from LUTS to offer therapeuticand nursing care on the relevant level. Keywords. DAN-PSS, distress, LUTS, population-based, postal questionnaire.     

Efficient priming of simian/human immunodeficiency virus (SHIV)-specific T-cell responses with DNA encoding hybrid SHIV/hepatitis B surface antigen particles

Recent efforts to design an human immunodeficiency virus type 1 (HIV-1) vaccine candidate have focused on means of eliciting anti-viral T-cell responses. We tried to improve the immunogenicity of DNA vaccines by designing hybrid DNA constructs encoding hepatitis B surface antigen (HBsAg) fused to antigenic domains of simian/human immunodeficiency virus (SHIV 89.6P). Immunisation with hybrid DNA induced both effector and long-lasting precursor T-cells. Following boosting with a recombinant modified vaccinia Ankara (rMVA) producing full-length SIV and HIV antigens, it appeared that priming with hybrid DNA had increased virus-specific T-cell responses in terms of both the number of virus-specific IFN-gamma-secreting T-cells and virus-specific lymphoproliferation. After intrarectal challenge with SHIV 89.6P, immunised animals demonstrated early control of SHIV 89.6P replication and stable CD4+ T-cell counts.     

Modelling HIV-RNA viral load in vertically infected children

Human immunodeficiency virus (HIV) ribo-nucleic acid (RNA) viral load is a measure of actively replicating virus and is used as a marker of disease progression. For a thorough understanding of the dynamics of the evolution of the virus in the early life of HIV-1 vertically infected children, it is important to elucidate the pattern of HIV-RNA viral load over age. An aspect of assay systems used in the quantification of RNA viral load is that they measure values above particular cut-off values for detection, below which the assays used are not sufficiently sensitive. In this way, measurements are potentially left-censored. Recent adult studies suggest that to adequately model RNA pattern over age, it is necessary to account for within-subject correlation, due to repeated measures, and censoring. The aim of this study, therefore, was to establish whether it is necessary to use complex methods to allow for repeated measures within individuals and censoring of the HIV-RNA viral load in children enrolled in a cohort study. The approach involved the identification of an appropriate model for the basic pattern of RNA viral load by age and subsequent assessment of various estimation procedures accounting for repeated measures and censoring in different ways. Methods developed by Hughes involving the expectation-maximization (EM) algorithm and the Gibbs sampler were taken as the benchmark for comparison of simpler alternatives. Other approaches considered involve linear mixed-effects and ordinary least squares in which censoring is dealt with informally by taking the cut-off value as absolute or taking the mid-point between cut-off and zero. Fractional polynomials provided a substantially superior approach for modelling the dynamics of viral load over age compared to conventional polynomials or change-point models. Allowing for repeated measures was necessary to improve the power of the likelihood ratio tests required to establish the final model, but methods beyond taking the mid-point for censored values did not further improve the fit. Although Hughes' methodology is the best approach, its implementation is not necessary for the identification of the optimal model.