Assessment of the scatter fraction evaluation methodology using Monte Carlo simulation techniques

To evaluate scatter fraction and scatter pair spatial distribution, experimental methods are generally used. These methods make use of a line source, placed along the FOV axis, inserted in a cylindrical phantom filled with air or water. The accuracy of these experimental methodologies can be tested by the use of a Monte Carlo method. In fact, the simulation allows the shape of the scatter event projection and the scatter fraction to be defined. An example of this application is the simulation package PETSI (PET SImulation). In this paper the comparison between the predicted scatter fraction and the experimentally evaluated one, obtained using an ECAT III PT 911/02 double ring whole body scanner are presented. PETSI permits additional data to be obtained: a) the true and scatter component of the energy spectrum; b) the spatial distribution, in the FOV plane, of the detected scatter events at different energy thresholds; c) the scatter to total detected events ratio; d) the predicted scatter fraction at both energy thresholds and FOV diameters. This information is very useful for optimizing both energy threshold and FOV size and to improve the accuracy of the currently used methods for the scatter fraction evaluation. Preliminary results of the predicted scatter fraction in a uniform phantom are presented.This article was presented at the 1st EEC workshop on accuracy determination in PET, January 19–20th. 1989 Pisa, Italy (COMAC-BME Concerted Project Characterization and Standardization of PET Instrumentation)     

Profile of in Vitro Binding Affinities of Neuroleptics at Different Rat Brain Receptors: Cluster Analysis Comparison with Pharmacological and Clinical Profiles

A series of 21 neuroleptics with different chemical structures (phenothiazines, thioxanthenes, dibenzodiazepines, butyrophenones, benzamides, etc.) was examined for their in vitro interactions with 12 neurotransmitter binding sites in the rat brain (alpha- and beta-noradrenergic, dopaminergic, muscarinic, serotoninergic, histaminic, and opioid receptors, calcium channels, and serotonin uptake binding sites). The biochemical profile obtained from the binding data was compared with reported pharmacological and clinical profiles for this class of compounds by cluster analysis. Cluster analysis on binding data classified the compounds in three main subgroups: benzamides, compounds with an affinity mainly for DA2 and 5-HT2 receptors and inactive at muscarinic receptors, and compounds with a high affinity for alpha 1-adrenergic receptors and muscarinic receptors. The main subgroups resulting from cluster analysis of previously published pharmacological and clinical data for neuroleptics contain compounds common to the present study, with some correlations. The results extend previous observations that a complete binding profile corresponds to the pharmacological and clinical profile of this class of compounds.     

Echocardiography and Doppler sonography in the evaluation of cardiac structure and function

Physical activity increases the work load of the heart. The adjustments of the heart depend on the quality and quantity of the work performed. These adjustments concern the function and the morphology of the cardiovascular system. It is important to underline that these adjustments are not permanent and can disappear when physical activity is stopped. In young subjects the risks are very few while the benefits may be shown on a better and more armonic body structure. In the elderly the benefits can be achieved with a lesser cost for submaximal activities, but the risks are of course more frequent due the possible onset of cardiovascular disease. It is important to correctly recognize the limits whitin which the physical activity can be allowed because beneficial. Echocardiography has given an important contribution to evaluate the morpho-functional adaptions of the athlete's heart. Similarly, it has proven useful in the detection of pathological cardiovascular modifications, asymptomatic or pausymptomatic, that do not allow certification to practise sport at agonistic levels.     

Bleeding patterns in recent postmenopausal outpatients with uterine myomas: comparison between two regimens of HRT

Objectives: To evaluate and to compare the bleeding patterns obtained with two regimens of hormone replacement therapy given to early postmenopausal women with asymptomatic uterine leiomyomas. Methods: In this randomised prospective 1-year study 50 early postmenopausal women with one to four asymptomatic uterine leiomyomas were enrolled into two study-groups to take two regimens of hormone replacement therapy for 12 28-day cycles: (A) Tibolone, 2.5 mg/day; (B) conjugated equine estrogens (CEE), 0.625 mg/day plus medroxyprogesterone acetate (MPA), 5 mg/day. The bleeding patterns and the changes in uterine volume of the 47 outpatients who completed the study were evaluated and compared. Results: Amenorrhea incidence was higher in group A (75.0% of the cycles) than in group B (65.6% of the cycles), while irregular bleeding and irregular spotting incidences were higher in group B (29.7 and 4.7% of the cycles, respectively) compared to group A (22.6 and 2.4% of the cycles, respectively). The mean bleeding and spotting lengths were not statistically different between patients in group A and those in group B. Finally, at the end of the study period transvaginal ultrasonography showed no significant change in leiomyoma size. Conclusions: The results demonstrate that, in early postmenopausal patients with asymptomatic uterine leiomyomas, Tibolone treatment seems to be preferable compared to CEE–MPA continuous combined treatment in relation to the lesser occurrence of irregular bleeding. Furthermore, neither Tibolone nor CEE–MPA therapy, at the doses used here, promote fibroid growth.     

Reduction of capsular polysaccharide production in Klebsiella pneumoniae by sodium salicylate.

Heavily encapsulated Klebsiella pneumoniae (serotypes 1 and 2) was cultured in the presence of sodium salicylate. The addition of salicylate (2 to 30 micrograms/ml) progressively decreased the amount of capsular polysaccharide produced by all strains without significantly inhibiting cell growth. Further addition of salicylate (50 to 200 micrograms/ml) was progressively inhibitory to cell growth and decreased the production of polysaccharide only slightly. The optimal concentration of salicylate that could reduce the polysaccharide production of heavily encapsulated, virulent strains by 50% or more was 30 micrograms/ml. Mutants of these bacteria that produced less capsule were affected by salicylate to a lesser degree. All concentrations of salicylate tested were physiologically achievable in humans and within the therapeutic range of aspirin. The addition of calcium and magnesium partially reversed the effects of salicylate on polysaccharide production. Chelating agents, particularly EGTA [ethylene-bis(oxyethylenenitrile)tetraacetic acid], reduce capsule production as salicylate did. Thus, the chelation of calcium and magnesium by salicylate could account, at least in part, for the reduction of capsule. Optical density measurements allowed for rapid monitoring of capsule production in various culture media because a large part of culture turbidity was apparently due to the capsule. Decreased production of the primary K. pneumoniae virulence factor with salicylate may have therapeutic potential.     

Evaluation of a Rapid Immunochromatographic Test for Serodiagnosis of Visceral Leishmaniasis

The purpose of this study was to compare the performance of a rapid immunochromatographic dipstick test for the qualitative detection of circulating antibodies to the leishmanial recombinant antigen K39 with that of a classical immunofluorescent antibody test for serodiagnosis of visceral leishmaniasis. Sera from 143 Italian subjects, including 69 patients with clinically suspected visceral leishmaniasis, 23 patients with hypergammaglobulinemia and 51 healthy controls, were tested. The immunochromatographic test was performed according to the manufacturer's instructions, using antigen-impregnated nitrocellulose paper strips. The immunofluorescent antibody test was performed according to an established method, using promastigotes of Leishmania infantum zymodeme Montpellier 1 as antigen. In 11 patients, diagnosis of active Leishmania infection was established by microscopic examination of biopsy samples and/or clinical response to meglumine antimoniate. Results of the two tests correlated for all but two sera examined. In two patients, one with proven infectious mononucleosis and one with bacterial pneumonia, the immunofluorescent antibody test was positive and the dipstick test was negative. In the restricted sample of patients in whom a definitive diagnosis was established, the immunochromatographic test was positive in 11 of 11 patients with confirmed Leishmania infection and negative in 103 of 103 subjects who either had other documented diseases or were healthy controls, showing 100% sensitivity and 100% specificity. Electronic Publication     

High-sensitivity, high-linearity, low-leak, self-balanced impedance cardiograph

An impedance cardiograph (so-called cardioimpedance meter) with the following characteristics is described: preadjustable current generator range of 0-4 mA rms at 100 kHz, crystal-controlled; sensitivity up to 50 V/omega with a resolution of 2 m omega; maximum nonlinearity of 2%; 0.7 microA arms of maximum leak current at 50 Hz; flat frequency response between 0 and 19 Hz. The instrument is self-balanced, using Arenson's bridge [1] with minor modifications, and is also able to operate as a plethysmograph, respirograph, and as an intracardiac Z-meter. Preliminary test as an impedance cardiograph yielded a correlation coefficient better than 0.8 when the stroke volume was evaluated by Kubicek's method and compared with values obtained using thermodilution.     

Dipolar sources of the early scalp somatosensory evoked potentials to upper limb stimulation Effect of increasing stimulus rates

Brain electrical source analysis (BESA) of the scalp electroencephalographic activity is well adapted to distinguish neighbouring cerebral generators precisely. Therefore, we performed dipolar source modelling in scalp medium nerve somatosensory evoked potentials (SEPs) recorded at 1.5-Hz stimulation rate, where all the early components should be identifiable. We built a four-dipole model, which was issued from the grand average, and applied it also to recordings from single individuals. Our model included a dipole at the base of the skull and three other perirolandic dipoles. The first of the latter dipoles was tangentially oriented and was active at the same latencies as the N20/P20 potential and, with opposite polarity, the P24/N24 response. The second perirolandic dipole showed an initial peak of activity slightly earlier than that of the N20/P20 dipolar source and, later, it was active at the same latency as the central P22 potential. Lastly, the third perirolandic dipole exaplaining the fronto-central N30 potential scalp distribution was constantly more posterior than the first one. In order to evaluate the effect of an increasing repetition frequency on the activity of SEP dipolar sources, we applied the model built from 1.5-Hz SEPs to traces recorded at 3-Hz and 10-Hz repetition rates. We found that the 10-Hz stimulus frequency reduced selectively the later of the two activity phases of the first perirolandic dipole. The decrement in strength of this dipolar source can be explained if we assume that: (a) the later activity of the first perirolandic dipole can represent the inhibitory phase of a “primary response”; (b) two different clusters of cells generate the opposite activities of the tangential perirolandic dipole. An additional finding in our model was that two different perirolandic dipoles contribute to the centro-parietal N20 potential generation. Received: 5 August 1997 / Accepted: 26 November 1997