A theoretical model evaluating the angular distribution of luminescence emission in X-ray scintillating screens.

The aim of this study was to examine the angular distribution of the light emitted from radiation-excited scintillators in medical imaging detectors. This distribution diverges from Lambert's cosine law and affects the light emission efficiency of scintillators, hence it also affects the dose burden to the patient. In the present study, the angular distribution was theoretically modeled and was used to fit experimental data on various scintillator materials. Results of calculations revealed that the angular distribution is more directional than that predicted by Lambert's law. Divergence from this law is more pronounced for high values of light attenuation coefficient and thick scintillator layers (screens). This type of divergence reduces light emission efficiency and hence it increases the incident X-ray flux required for a given level of image brightness.     

Gluten neuropathy: electrophysiological progression and HLA associations

Journal of Neurology - Gluten neuropathy (GN) is the term used to describe peripheral neuropathy that occurs in patients with gluten sensitivity (GS) or coeliac disease (CD) in the absence of other...     

Brain volume dynamics in multiple sclerosis. A case-control study

ABSTRACT

Objectives: In this study, we aimed to explore the extent and clinical relevance of brain volume dynamics in relapsing remitting multiple sclerosis (RRMS).

Methods: Sixty-three patients with RRMS with a disease duration of about 5 years (36 women, mean age 39.9 ± 9.4 years; mean EDSS1.4 ± 1.2, mean relapse rate 0.98 ± 1.17) and 50 healthy control individuals (24 women, mean age 39.1 ± 10.2 years) were recruited and imaged on a MRI scanner by using post-gadolinium high-resolution3D T1W sequences. Cross-sectional and longitudinal volumetric data were obtained by using SIENA(X) and FIRST software.

Results: Patients showed significantly lower subcortical volumes compared to healthy controls. Interestingly, the educational level predicted the rate of right thalamus atrophy. The mean annualized percentage of brain volume change (aPBVC) was ?0.92% (±1.64%) and was presented in higher rates during the first five years after MS diagnosis.

Conclusion: Brain atrophy mainly involved subcortical grey matter structures and was more conspicuous during the first years of MS diagnosis. The buffering role of education in atrophy was also corroborated by this study.     

Three pyrone glucosidic derivatives from Conyza albida

Three new pyrone glucosidic derivatives, together with the known pyromeconic acid glucoside, three acytelenes and two eudesmanes, were obtained from the aerial parts of Conyza albida. The structures were elucidated by high field NMR spectroscopy.     

Evaluating phosphors for use in X-ray image detectors by the effective performance index (EPI) method: application to Eu3+ activated yttrium based materials.

Phosphor materials used in X-ray image receptors were evaluated by the effective performance index (EPI). EPI describes the dependence of image quality on X-ray to light energy conversion and light diffusion processes. EPI was experimentally determined by means of X-ray luminescence (XLE) and MTF measurements performed on Y2O2S:Eu, Y2O3:Eu, and YVO4:Eu phosphors. The spectral compatibility of these materials with optical detectors (films, photocathodes, photodiodes) was also determined. Highest EPI values were obtained for Y2O2S:Eu-GaAs combination at mammographic energies. All phosphors could be of use in digital X-ray imaging being adequately compatible to silicon photodiodes employed in digital detectors.     

Polycystic ovarian syndrome: the commonest cause of hyperandrogenemia in women as a risk factor for metabolic syndrome

Polycystic ovarian syndrome (PCOS), the commonest endocrine disorder of women, is currently emerging as a potential facet of the metabolic syndrome (MBS) in women. Available data suggest that the MBS or, alternatively, individual metabolic risk factors may be overly present and most importantly that MBS may arise at a significantly younger age among PCOS women. The concept that a conventionally considered reproductive disorder may entail a significant metabolic impact on affected women has warranted medical interest on the mechanisms underlying the multiplicative sequelae of PCOS. Although obesity indisputably compounds the clinical course of women with PCOS, this appears to be just the tip of the iceberg. Insulin resistance and hyperinsulinemia have been intuitively involved as a critical link due to their contribution to the pathophysiology and clinical presentation of both PCOS and MBS. Hyperandrogenemia, the predominant endocrine hallmark of PCOS, has also been implicated as a contributing factor to the suggested interrelationship.     

Europium-activated phosphors for use in X-ray detectors of medical imaging systems

Three europium-activated phosphors Y₂O₂S:Eu, Y₂O₃:Eu, and YVO₄:Eu emitting red light were studied to investigate their suitability for radiographic cassettes or digital imaging systems. Screens were prepared from phosphor powders with various coating thicknesses by sedimentation. To assess phosphor light producing efficiency in relation to patient dose, each screen was X-rayed using 40–120 kVp and the number of light photons emitted per X-ray incident was experimentally and theoretically evaluated. Additionally, the capability of the emitted light to sensitize films or to generate electrons in silicon photodiodes used in digital imaging systems was examined. Y₂O₂S:Eu screens were most efficient in light emission, and when combined with either red sensitive films or Si photodiodes, they were found superior to Y₂O₃:Eu or YVO₄:Eu screens in film grain or electron signal generation. In many cases they were also found superior to terbium-activated phosphors. Provided that several problems related to industrial production (special dyes, reflective backing, crossover effects) are dealt with, those europium-activated screens could be employed in low-tube-voltage radiographic applications. Received 17 March 1997; Revision received 25 July 1997; Accepted 21 August 1997     

Epikeratophakia for Myopia Correction

Epikeratophakia is based on the principles of the Barraquer refractive procedures, with modifications that simplify the surgical technique and eliminate the use of the microkeratome by placing the donor corneal tissue lens on the anterior surface of the cornea. Procedures developed to permit freeze-drying the preshaped lens for storage enable these lenses to be obtained from a central source, freeing the surgeon from the complexities of the computer and the cryolathe. The correction of theoretically unlimited amounts of myopia is possible with these lenses. In 12 eyes that underwent the final epikeratophakia procedure, the average desired correction achieved was 98%.     

Distribution and characterization of cyclo (His-Pro)-like immunoreactivity in the human gastrointestinal tract

Cyclo (His-Pro) [C(HP)] has been measured by radioimmunoassay in perchloric acid extracts of human gastrointestinal (GI) tract structures derived from autopsy sources and fresh colonic biopsies. C(HP) was identified in all regions of the human GI tract, ranging in concentrations from 599 +/- 102 pg/mg protein in stomach, to 127 +/- 26 pg/mg protein in esophagus. The mean concentration of C(HP) from colonic biopsies was 335 +/- 30 pg/mg protein, statistically similar to values derived from postmortem sources. Since C(HP) concentrations are within the range of other gut peptide modulators, cyclo (His-Pro) is speculated to play a role as a new paracrine modulator of human GI tract function(s).     

Short-term effect of orlistat on dietary glycotoxins in healthy women and women with polycystic ovary syndrome

Exogenous advanced glycation endproducts (AGEs, known atherogenic molecules) abundant in everyday precooked, rich in fat, overheated meals can possibly contribute to the increased risk for diabetes and cardiovascular disease in women with polycystic ovary syndrome (PCOS). The aim of the present study was to investigate the effect of a lipase inhibitor on absorbed food glycotoxins in healthy women and those with PCOS. A 2-day protocol was followed. In the first day, a meal rich in AGE was provided, which on the second day was followed by two 120-mg capsules of lipase inhibitor, orlistat. Serum AGE levels were evaluated at baseline (0 hours), and at 3 and 5 hours postmeal during the study. Thirty-six women were studied, 15 controls (mean age, 28.80 +/- 5.47 years; body mass index, 25.85 +/- 6.73 kg/m(2)) and 21 with PCOS (mean age, 25.29 +/- 5.06 years; body mass index, 30.40 +/- 7.51 kg/m(2)) (University Hospital, Athens, Greece, institutional practice). Serum AGE levels, on day 1, were significantly increased both in the control group and in the PCOS group as compared with basal values (control group, 14.1%; PCOS group, 6.0%; P < .001). The corresponding rise was significantly lower on day 2 when the same meal was combined with orlistat (control group, 4.1%; PCOS group, 2.0%; P < .01). A limitation of the study is that it is a nonplacebo, nonrandomized therapeutic trial where each subject is considered as its own control. In conclusion, this study demonstrated the beneficial effect of orlistat on the absorption of food glycotoxins.