Computed tomography diagnostic reference levels for adult brain, chest and abdominal examinations: A systematic review.

OBJECTIVES: Radiation dose variation within and among Computed Tomography (CT) centres is commonly reported. This work systematically reviewed published articles on adult Diagnostic Reference Levels (DRLs) for the brain, chest and abdomen to determine the causes and extent of variation. A systematic literature search and review was performed in selected databases containing leading journals in radiography, radiology and medical physics using carefully defined search terms related to CT and DRLs. The quality of the included articles was determined using the Effective Public Health Practise Project tool for quantitative studies. KEY FINDINGS: The 54 articles reviewed include: 45 studies using human data, 8 studies using phantom data, and one study with both human and phantom data. The main comparator in between studies was the dose indices used in reporting DRLs. DRL variations of up to a factor of 2 for the same procedure were noted in phantom studies, and up to a factor of 3 in human studies. Sources of variation include the type of scanner, the age of the scanner, differences in protocols, variations in patients, as well as variations in study design. Different combinations of dose indices were reported: volume computed tomography dose index (CTDIvol) and dose length product (DLP) (59%); DLP only (11%); weighted computed tomography dose index (CTDIw) and DLP (9%); CTDIvol only (7%); CTDIvol, DLP and effective dose (ED) (6%); CTDIw only (4%); CTDIvol, DLP and size specific dose estimate (SSDE) (1%) and CTDIw, CTDIvol and DLP (1%). The use of different dose indices limited dose comparison between studies. CONCLUSION: The study noted a 2-3 fold variation in DRLs between studies for the same procedure. The causes of variation are reported and include study design, scanner technology and the use of different dose indices. IMPLICATIONS FOR PRACTICE: There is a need for standardisation of CT DRLs in line with the International Commission on Radiological Protection recommendations to reduce dose variation and facilitate dose comparison.

Waveform analysis of non-oscillatory independent components in single-trial auditory event-related activity in healthy subjects and Alzheimer's disease patients.

The objective was to characterize the non-oscillatory independent components (ICs) of the auditory event-related potential (ERP) waveform of an oddball task for normal and newly diagnosed Alzheimer's disease (AD) subjects, and to seek biomarkers for AD. Single trial ERP waveforms were analysed using independent components analysis (ICA) and k-means clustering. Two stages of clustering depended upon the magnitudes and latencies, and the scalp topographies of the non-oscillatory back-projected ICs (BICs) at electrode Cz. The electrical current dipole sources of the BICs were located using Low Resolution Electromagnetic Tomography (LORETA). Generally 3-10 BICs, of different latencies and polarities, occurred in each trial. Each peak was associated with positive and negative BICs. The trial-to-trial variations in their relative numbers and magnitudes may explain the variations in the averaged ERP reported, and the delay in the averaged P300 for AD patients. The BIC latencies, topographies and electrical current density maximum locations varied from trial-to-trial. Voltage foci in the BIC topographies identify the BIC source locations. Since statistical differences were found between the BICs in healthy and AD subjects, the method might provide reliable biomarkers for AD, if these findings are reproduced in a larger study, independently of other factors influencing the comparison of the two populations. The method can extract artefact- and EEG-free single trial ERP waveforms, offers improved ERP averages by selecting the trials on the basis of their BICs, and is applicable to other evoked potentials, conditions and diseases.

Botulism: a case associated with pyramidal signs.

Botulism is a widespread neuroparalytic disease that may be confused with other neurological disorders. As it is potentially lethal, clinicians are required to be aware of its diagnosis and management. We report a case of botulism complicated by pyramidal signs in a 35-year-old woman. Clinical aspects, differential diagnoses and therapeutic problems are discussed.

[Infectivity and effectiveness of different strains of Frankia spp. on Atriplex cordobensis plants]. / Infectividad y efectividad de distintas cepas de Frankia spp sobre plantas de Atriplex cordobensis.

Frankia is an actinomycete that fixes atmospheric nitrogen in actinorhizal symbiosis (in non-legume plants). Atriplex cordobensis is an important Chaco Arido forage species due to the high nitrogen content. The aim of this paper was to isolate plant endophytes to be utilized as an inoculum in adapted species. A. cordobensis seedlings of 30 days were inoculated with isolated strains of Atriplex cordobensis, Colletia hystrix, Trevoa trinervis, Talguenea quinquenervia and 4-6 strains of Retanilla ephedra, courtesy of the University of Chile. A complete randomized design with 9 replications was performed. The infective ability of the strains was established through the re-isolation of the endophytes in QMOD artificial medium. The infectivity was evaluated by means of: plant aerial part length, leaf number, number and length of internodes, dry weight and total nitrogen content. The symbiotic effectivity, inoculation response and fixed nitrogen quantity were calculated. All strains treated on A. cordobensis presented Frankia typical morphological characteristics. A. cordobensis and C. hystrix showed the best nitrogen fixing effectivity, T. quinquenervia had a good aerial development but its fixing nitrogen ability was low, as a plant growth promoting rhizobacteria (PGPR). All strains were infective and A. cordobensis and C. hystrix apported the highest nitrogen amount to the plants.

Dynamic structure neural networks for stable adaptive control of nonlinear systems.

An adaptive control technique, using dynamic structure Gaussian radial basis function neural networks, that grow in time according to the location of the system's state in space is presented for the affine class of nonlinear systems having unknown or partially known dynamics. The method results in a network that is "economic" in terms of network size, for cases where the state spans only a small subset of state space, by utilizing less basis functions than would have been the case if basis functions were centered on discrete locations covering the whole, relevant region of state space. Additionally, the system is augmented with sliding control so as to ensure global stability if and when the state moves outside the region of state space spanned by the basis functions, and to ensure robustness to disturbances that arise due to the network inherent approximation errors and to the fact that for limiting the network size, a minimal number of basis functions are actually being used. Adaptation laws and sliding control gains that ensure system stability in a Lyapunov sense are presented, together with techniques for determining which basis functions are to form part of the network structure. The effectiveness of the method is demonstrated by experiment simulations.

Involvement of corticospinal tract in Wilson's disease. A study of three cases with transcranial stimulation.

Muscle responses evoked by transcranial stimulation were studied in three patients with Wilson's disease. Abnormalities indicating involvement of corticospinal tract were demonstrated in one patient. In keeping with recent evoked potential studies, this finding suggests that lesions in Wilson's disease may affect structures other than the extrapyramidal system.