Proton relaxation times T1 and T2 of macromolecular solutions, bovine brain tissues, and experimental cat brain edema tissues were studied as a function of water concentration, protein concentration, and temperature. A linear relation was found between the inverse of the weight fraction of tissue water and the spin-lattice relaxation rate, R1, based on a fast proton exchange model for relaxation. This correlation was also found for the spin-spin relaxation rate, R2, of gray matter samples and macromolecular solutions at low concentrations. Concentrated solutions of protein-water samples showed an enhanced relaxation due to viscosity effects. The T2 of white matter was considerably lengthened with elevated water concentration, but showed no straightforward relation with the total tissue water content. The relaxation times of all samples increased with temperature, supporting the assumption of fast proton exchange in the model for relaxation. This was not found for white matter, in which T2 decreased with increasing temperature, which indicated that intermediate or even slow exchange was present. The relation found between relaxation times and tissue water content can be used to predict the amount of and/or increase in tissue water due to water-elevating processes such as edema.
In a general sense Traffic Medicine in the Netherlands concerns multidisciplinary research about how to reduce traffic crashes and injuries following a “systems approach”. Several universities and research institutes are involved, including the SWOV research institute of traffic safety( 1). In a specific sense Traffic Medicine in the Netherlands concerns researching and applying regulations and methods for assessing and improving fitness to drive in persons with impairments in physical and mental functions which are relevant for driving. Important recent developments in the general and specific field are discussed. Because the Netherlands is a flat country with a moderate climate and generally small distances between destinations, bicycling is a very important mode of transport also for older persons. In general traffic safety has improved tremendously over the last years but much less so for older (65+) cyclists. This is particularly problematic because the older population is increasing and with the arrival of the e-bike, cycling is increasingly popular. Several approaches to improve bicycle safety have been proposed. The Netherlands is part of the European Union (EU) and medical aspects of driver licensing are based on Directives (2) of the European Parliament and Council. The European directive is not very detailed with regard to medical fitness to drive and individual countries can have more specific regulations. For example with regard to neurological disorders and dementia the EU directive states that: “driving licenses shall not be issued to, or renewed for, applicants or drivers suffering from a serious neurological disease or severe behavioural problems due to ageing, unless the application is supported by authorized medical opinion, and if necessary, subject to regular medical check-ups”. It will be discussed how, based on medical consensus and multidisciplinary research, this requirement has been implemented in the Netherlands. In empirical research persons with moderately severe visual (visual acuity < 0.5; homonymous hemianopia) and cognitive impairments (traumatic brain injury; stroke) have been systematically observed when actually driving. On average, driving was poorer in patients than in healthy subjects but many subjects in the patient groups drove safely and fluently and performance was not predicted sufficiently from medical and psychological characteristics (3,4). They appeared to compensate effectively, sometimes also helped by technology, for example the bi-optic telescope, and by visual training and special driving lessons. This has led to changes in regulations such that in the case of moderately severe visual and cognitive impairments on-road tests of “practical fitness to drive” have become important additions to the conventional medical and psychological assessments. Developments in intelligent driver support and autonomous vehicles promise further opportunities for compensating driver impairment but unwanted behavioural changes (adaptation) must be avoided (5). References: 1.SWOV publishes great overviews of recent developments in traffic safety research in its factsheets: http://www.swov.nl/uk/Research/factsheets.htm 2.Directive 2006/126/EC of the European Parliament and of the Council of 20 December 2006 on driving licenses including more recent amendments: http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=URISERV:l24141 3.Coeckelbergh T.R.M, Brouwer W.H., Cornelissen F.W., Kooijman A.C. 2004).Predicting practical fitness to drive in drivers with visual field defects caused by ocular pathology. Human Factors,46, p.748-760. 4.Brouwer, W.H., & Withaar, F.K. (1997). Fitness to drive after traumatic brain injury. Neuropsychological Rehabilitation, 7, p.177-193. 5.Dotzauer, M., Caljouw, S. R., De Waard, D., & Brouwer, W. H. (2015). Longer-term effects of ADAS use on speed and headway control
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