1,855 research outputs found
Assessment of poststress left ventricular ejection fraction by gated SPECT: comparison with equilibrium radionuclide angiocardiography
PURPOSE: We compared left ventricular (LV) ejection fraction obtained by gated SPECT with that obtained by equilibrium radionuclide angiocardiography in a large cohort of patients.
METHODS: Within 1 week, 514 subjects with suspected or known coronary artery disease underwent same-day stress-rest (99m)Tc-sestamibi gated SPECT and radionuclide angiocardiography. For both studies, data were acquired 30 min after completion of exercise and after 3 h rest.
RESULTS: In the overall study population, a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.82, p<0.0001) and after stress (r=0.83, p<0.0001). In Bland-Altman analysis, the mean differences in ejection fraction (radionuclide angiocardiography minus gated SPECT) were -0.6% at rest and 1.7% after stress. In subjects with normal perfusion (n=362), a good correlation between ejection fraction measured by gated SPECT and by radionuclide angiocardiography was observed at rest (r=0.72, p<0.0001) and after stress (r=0.70, p<0.0001) and the mean differences in ejection fraction were -0.9% at rest and 1.4% after stress. Also in patients with abnormal perfusion (n=152), a good correlation between the two techniques was observed both at rest (r=0.89, p<0.0001) and after stress (r=0.90, p<0.0001) and the mean differences in ejection fraction were 0.1% at rest and 2.5% after stress.
CONCLUSION: In a large study population, a good agreement was observed in the evaluation of LV ejection fraction between gated SPECT and radionuclide angiocardiography. However, in patients with perfusion abnormalities, a slight underestimation in poststress LV ejection fraction was observed using gated SPECT as compared to equilibrium radionuclide angiocardiography
Supersymmetry of a Nonstationary Pauli Equation
The supersymmetry of the electron in both the nonstationary magnetic and
electric fields in a two-dimensional case is studied. The supercharges which
are the integrals of motion and their algebra are established. Using the
obtained algebra the solutions of nonstationary Pauli equation are generated.Comment: 12 pages, Late
Motion of a spin 1/2 particle in shape invariant scalar and magnetic fields
We study the motion of a spin 1/2 particle in a scalar as well as a magnetic
field within the framework of supersymmetric quantum mechanics(SUSYQM). We also
introduce the concept of shape invariant scalar and magnetic fields and it is
shown that the problem admits exact analytical solutions when such fields are
considered.Comment: 14 page
Photon creation in a spherical oscillating cavity
We study the photon creation inside a perfectly conducting, spherical
oscillating cavity. The electromagnetic field inside the cavity is described by
means of two scalar fields which satisfy Dirichlet and (generalized) Neumann
boundary conditions. As a preliminary step, we analyze the dynamical Casimir
effect for both scalar fields. We then consider the full electromagnetic case.
The conservation of angular momentum of the electromagnetic field is also
discussed, showing that photons inside the cavity are created in singlet
states.Comment: 14 pages, no figure
Comparison of bioelectrical impedance analysis and dual-energy X-ray absorptiometry for the assessment of appendicular body composition in anorexic women
Objective: To establish the accuracy of bioelectrical impedance analysis (BIA) for the assessment of appendicular body
composition in anorexic women.
Design: Cross-sectional study.
Setting: Outpatient University Clinic.
Subjects: A total of 39 anorexic and 25 control women with a mean (s.d.) age of 21 (3) y.
Methods: Total, arm and leg fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry and predicted from total
and segmental BIA at 50 kHz. The predictor variable was the resistance index (Rl), that is, the ratio of height 2 to body resistance
for the whole body and the ratio of length2/limb resistance for the arm and leg.
Results: Predictive equations developed on controls overestimated total, arm and leg FFM in anorexics (Po0.0001). Populationspecific
equations gave a satisfactory estimate of total and appendicular FFM in anorexics (P\ubcNS) but had higher percent root
mean square errors (RMSEs%) as compared to those developed on controls (8% vs 5% for whole body, 12% vs 10% for arm and
10% vs 8% for leg). The accuracy of the estimate of total and leg FFM in anorexics was improved by adding body weight (Wt) as
a predictor with Rl (RMSE%\ubc5% vs 8% and 7% vs 10%, respectively). However, the same accuracy was obtained using Wt
alone, suggesting that in anorexics, BIA at 50 kHz is not superior to Wt for assessing total and leg FFM.
Conclusion: BIA shows some potential for the assessment of appendicular body composition in anorexic women. However, Wt
is preferable to BIA at 50 kHz on practical grounds. Further studies should consider whether frequencies 450 kHz give better
estimates of appendicular composition in anorexics as compared to Wt
Superevolution
Usually, in supersymmetric theories, it is assumed that the time-evolution of
states is determined by the Hamiltonian, through the Schr\"odinger equation.
Here we explore the superevolution of states in superspace, in which the
supercharges are the principal operators. The superevolution equation is
consistent with the Schr\"odinger equation, but it avoids the usual degeneracy
between bosonic and fermionic states. We discuss superevolution in
supersymmetric quantum mechanics and in a simple supersymmetric field theory.Comment: 23 page
Exercise-rest Tc-99m tetrofosmin SPECT in patients with chronic ischemic left ventricular dysfunction: Direct comparison with Tl-201 reinjection
Background. This study was designed to compare the results of exercise-rest technetium-99m tetrofosmin single photon emission computed tomography (SPECT) with those of thallium-201 reinjection at rest after exercise-redistribution imaging in the same patients with chronic ischemic left ventricular (LV) dysfunction. Methods. Within 1 week, 33 patients with chronic myocardial infarction and LV dysfunction underwent exercise-rest tetrofosmin SPECT and Tl-201 reinjection at rest after exercise-redistribution imaging. In each patient, regional tetrofosmin and Tl-201 activity was quantitatively measured in 22 myocardial segments. Regional LV function was assessed in corresponding segments by echocardiography. Results. Agreement in the evaluation of regional perfusion status between tetrofosmin and Tl-201 imaging was observed in 78% of the 726 total segments, with a Îş value of 0.61. In segments with normal function at echocardiography (n = 436), no difference between Tl-201 and tetrofosmin uptake was observed. In hypokinetic segments (n = 138), exercise tetrofosmin uptake was lower (P < .01) as compared with exercise Tl-201 activity, whereas no difference was observed between tetrofosmin uptake at rest as compared with Tl-201 activity on redistribution and reinjection images. In segments with severe functional impairment (akinetic or dyskinetic, n = 152), tetrofosmin uptake on exercise images was reduced (P < .01) as compared with exercise Tl-201 activity; furthermore, tetrofosmin uptake at rest was lower (P < .01) as compared with Tl-201 activity on both redistribution and reinjection images. In these segments, concordance in the detection of myocardial viability between tetrofosmin and Tl-201 imaging was observed in 138 (91%) of the 152 segments, with a Îş value of 0.77. Conclusions. In patients with chronic coronary artery disease and LV dysfunction quantitative exercise-rest tetrofosmin and Tl-201 reinjection SPECT provide similar information in the assessment of perfusion status and in the detection of myocardial viability
On the construction of variant supergravities in D=11, D=10
We construct with a geometric procedure the supersymmetry transformation laws
and Lagrangian for all the ``variant'' D=11 and D=10 Type IIA supergravities.
We identify into our classification the D=11 and D=10 Type IIA ``variant''
theories first introduced by Hull performing T-duality transformation on both
spacelike and timelike circles. We find in addition a set of D=10 Type IIA
``variant'' supergravities that can not be obtained trivially from eleven
dimensions compactifying on a circle.Comment: 21 pages, Late
Effective Actions for Massive Kaluza-Klein States on AdS_3 x S^3 x S^3
We construct the effective supergravity actions for the lowest massive
Kaluza-Klein states on the supersymmetric background AdS_3 x S^3 x S^3. In
particular, we describe the coupling of the supergravity multiplet to the
lowest massive spin-3/2 multiplet which contains 256 physical degrees of
freedom and includes the moduli of the theory. The effective theory is realized
as the broken phase of a particular gauging of the maximal three-dimensional
supergravity with gauge group SO(4) x SO(4). Its ground state breaks half of
the supersymmetries leading to 8 massive gravitinos acquiring mass in a super
Higgs effect. The holographic boundary theory realizes the large N=(4,4)
superconformal symmetry.Comment: 31 pages, v2: minor change
Kaluza-Klein supergravity on AdS_3 x S^3
We construct a Chern-Simons type gauged N=8 supergravity in three spacetime
dimensions with gauge group SO(4) x T_\infty over the infinite dimensional
coset space SO(8,\infty)/(SO(8) x SO(\infty)), where T_\infty is an infinite
dimensional translation subgroup of SO(8,\infty). This theory describes the
effective interactions of the (infinitely many) supermultiplets contained in
the two spin-1 Kaluza-Klein towers arising in the compactification of N=(2,0)
supergravity in six dimensions on AdS_3 x S^3 with the massless supergravity
multiplet. After the elimination of the gauge fields associated with T_\infty,
one is left with a Yang Mills type gauged supergravity with gauge group SO(4),
and in the vacuum the symmetry is broken to the (super-)isometry group of AdS_3
x S^3, with infinitely many fields acquiring masses by a variant of the
Brout-Englert-Higgs effect.Comment: LaTeX2e, 24 pages; v2: references update
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