The Prony method and a modified Prony method (MPM), developed to improve the performance of this technique at low signal‐to‐noise ratio, are described and applied to analysis of magnetic resonance spectroscopy (MRS) signals. Furthermore, the way in which results from MPM can be used as prior information in a Bayesian model is also described. First, analysis on simulated data is used to establish the methods' limits of reliability. Their performance with respect to peak identification and quantification of nuclear magnetic resonance parameters are then assayed on real data. Results of application of the methods to 1H‐MRS signals from cultured cells are discussed and compared with those deriving from application of fast Fourier transform. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 565–571, 1997
This paper attempts to systematise all published experimental results for the dose reduction factor (DRF) offered by leaded eyewear on clinicians performing interventional procedures. We aim to present a comprehensive analysis of the issue and a comparison of the various equipment models at different exposure geometries. The main purpose of the paper is, however, to clarify the best choice for the DRF within the possible diverse contexts and approaches to eye lens dose assessment. Evidence has been obtained that the lowest estimates of DRF are associated with larger scatter incidence angles and that, except for the slightly better performance exhibited by wraparound eyeglasses, there is no real distinction between the DRFs for the different equipment categories. The dataset as a whole confirms that, when measurements for the concerned eyewear model and irradiation conditions are unattainable, assuming DRF = 2 represents an adequately conservative choice. Nonetheless, this value includes only 17% of all results from the literature, whereas their histogram follows a distribution skewed towards higher values, represented by a median equal to 5. Therefore, if more realistic dose reconstructions are necessary, such as for purposes of epidemiological investigations or compensation decisions, the adoption of this central tendency index appears to be more reasonable. The complexity of characterising the DRF behaviour as a function of the various exposure factors reinforces the consideration of a statistical approach to eye lens dose assessment as a viable alternative. In this perspective, assuming for DRF a lognormal distribution with parameters and which has been verified to satisfactorily approximate the literature data distribution, should be deemed to be an appropriate option.
The individual monitoring of the occupational exposure in interventional radiologyis problematic, owing primarily to the fact that the personnel has to wear a lead rubber protective apron. Indeed the dosimeter readings are not, in principle, accurately representative for the effective dose in all working conditions, irrespective of the over or under-apron dosimeter location. Therefore different simulations for this kind of exposure have been performed, which assess the effective dose from the doses to tissues and derive its relationship with the monitor readings. After briefly enquiring into the general approach to the effective dose estimate in the actual practice, the present paper firstly describes in this connection the characteristics of the radiation striking the staff in interventional radiology. Then it provides, within a unified framework and through a uniform notation, a review of the literature on the effective dose assessment from the doses to tissues relatively to this type of exposure. Specific results of a certain operative relevance are examined in some detail and particular attention is devoted to identify the most appropriate method for the effective dose estimate from the dosimeter readings. Which method is finally properly modified to conform it to the forthcoming update of the effective dose definition. Article published by EDP Sciences and available at RÉSUMÉ
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