1,176 research outputs found
Radiation Safety during Interventional Procedures:
__Abstract__
In interventional cardiology revascularization procedures are on the increase and as such
the x-ray radiation dose, used per procedure.
The recent introduction of new technologies, e.g. the drug eluting stent, has led to a
treatment shift. An increasing number of patients with multi-vessel disease, smaller
coronary arteries and diabetes, who previously underwent surgery, now undergo a
percutaneous coronary intervention.
The worldwide increase in percutaneous coronary interventions is described in Chapter 1.
While a coronary intervention can be lifesaving, there is no limit to either the investigation
or the radiation time. Therefore this result in an increase in the x-ray radiation dose to the
patient, and a higher scattered radiation dose to the operator.
Thus increasing both the possibility of skin damage to the patient and consequences to the
operator
Real-time quantification and display of skin radiation during coronary angiography and intervention
BACKGROUND: Radiographically guided investigations may be associated with excessive radiation exposure, which may cause skin injuries. The purpose of this study was to develop and test a system that measures in real time the dose applied to each 1-cm(2) area of skin, taking into account the movement of the x-ray source and changes in the beam characteristics. The goal of such a system is to help prevent high doses that might cause skin injury. METHODS AND RESULTS: The entrance point, beam size, and dose at the skin of the patient were calculated by use of the geometrical settings of gantry, investigation table, and x-ray beam and an ionization chamber. The data are displayed graphically. Three hundred twenty-two sequential cardiac investigations in adult patients were analyzed. The mean peak entrance dose per investigation was 0.475 Gy to a mean skin area of 8.2 cm(2). The cumulative KERMA-area product per investigation was 52.2 Gy/cm(2) (25.4 to 99.2 Gy/cm(2)), and the mean entrance beam size at the skin was 49.2 cm(2). Twenty-eight percent of the patients (90/322) received a maximum dose of 2 Gy. CONCLUSIONS: Monitoring of the dose distribution at the skin will alert the operator to the development of high-dose areas; by use of other gantry settings with nonoverlapping entrance fields, different generator settings, and extra collimation, skin lesion can be avoided
Edge detection versus densitometry in the quantitative assessment of stenosis phantoms: an in vivo comparison in procine coronary arteries
The aim of this study was the in vivo validation and comparison of the geometric and densitometric technique of a computer-assisted automatic quantitative angiographic system (CAAS system). In six Landrace Yorkshire pigs (45 to 55 kg), precision-drilled phantoms with a circular lumen of 0.5, 0.7, 1.0, 1.4, and 1.9 mm were percutaneously introduced into the left anterior descending or left circumflex coronary artery. Twenty-eight coronary angiograms obtained with the phantom in a wedged intracoronary position could be quantitatively analyzed. Minimal lumen diameter, minimal cross-sectional area, percent diameter stenosis, and cross-sectional area stenosis were automatically measured with both the geometric and densitometric technique and were compared with the known phantom dimensions. When minimal lumen diameter was measured using the geometric approach, a nonsignificant underestimation of the phantom size was observed, with a mean difference of -0.06 +/- 0.14 mm. The larger mean difference observed with videodensitometry (-0.11 +/- 0.20 mm) was the result of the failure of the technique to differentiate the low lumen videodensities of two phantoms of smaller size (0.5 and 0.7 mm) from a dense background. Percent cross-sectional area stenosis measured with the two techniques showed a good correlation with the corresponding phantom measurements (mean difference between percent cross-sectional area stenosis calculated from the quantitative angiographic measurements and the corresponding phantom dimensions was equal to 2 +/- 6% for both techniques, correlation coefficient = 0.93 with both techniques, SEE = 5% with the geometric technique and 6% with the densitometric approach).(ABSTRACT TRUNCATED AT 250 WORDS
Experimental observation of second-harmonic generation and diffusion inside random media
We have experimentally measured the distribution of the second-harmonic
intensity that is generated inside a highly-scattering slab of porous gallium
phosphide. Two complementary techniques for determining the distribution are
used. First, the spatial distribution of second-harmonic light intensity at the
side of a cleaved slab has been recorded. Second, the total second-harmonic
radiation at each side of the slab has been measured for several samples at
various wavelengths. By combining these measurements with a diffusion model for
second-harmonic generation that incorporates extrapolated boundary conditions,
we present a consistent picture of the distribution of the second-harmonic
intensity inside the slab. We find that the ratio of the
mean free path at the second-harmonic frequency to the coherence length, which
was suggested by some earlier calculations, cannot describe the second-harmonic
yield in our samples. For describing the total second-harmonic yield, our
experiments show that the scattering parameter at the fundamental frequency
\k_{1\omega}\ell_{1\omega} is the most relevant parameter in our type of
samples.Comment: 10 pages, 7 figure
AdS vacua and RG flows in three dimensional gauged supergravities
We study supersymmetric vacua in N=4 and N=8, three dimensional
gauged supergravities, with scalar manifolds and , non-semisimple Chern-Simons
gaugings and ,
respectively. These are in turn equivalent to SO(4) and
Yang-Mills theories coupled to supergravity. For the N=4 case, we study
renormalization group flows between UV and IR vacua with the same
amount of supersymmetry: in one case, with (3,1) supersymmetry, we can find an
analytic solution whereas in another, with (2,0) supersymmetry, we give a
numerical solution. In both cases, the flows turn out to be v.e.v. flows, i.e.
they are driven by the expectation value of a relevant operator in the dual
. These provide examples of v.e.v. flows between two vacua
within a gauged supergravity framework.Comment: 35 pages in JHEP form, 3 figures, typos corrected, references adde
DICER1 RNase IIIb domain mutations are infrequent in testicular germ cell tumours
Background: Testicular Germ Cell Tumours (TGCT) are the most frequently occurring malignancy in males from 15-45 years of age. They are derived from germ cells unable to undergo physiological maturation, although the genetic basis for this is poorly understood. A recent report showed that mutations in the RNase IIIb domain of DICER1, a micro-RNA (miRNA) processing enzyme, are common in non-epithelial ovarian cancers. DICER1 mutations were found in 60% of Sertoli-Leydig cell tumours, clustering in four codons encoding metal-binding sites. Additional analysis of 14 TGCT DNA samples identified one case that also contained a mutation at one of these sites. Findings. A number of previous studies have shown that DICER1 mutations are found in Q) within the RNase IIIb domain in one TGCT sample, which was predicted to disturb DICER1 function. Conclusion: Overall our findings suggest a mutation frequency in TGCTs of ∼1%. We conclude therefore that hot-spot mutations, frequently seen in Sertoli-Leydig cell tumours, are not common in TGCTs
Coronary arteriography for quantitative analysis: experimental and clinical comparison of cinefilm and video recordings.
Although use of videotape for the recording of coronary angiograms continues to grow, the validity of quantitative coronary angiographic analysis of video images remains unknown. To estimate the realibility of angiographic images recorded on videotapes, experimental and clinical angiograms were recorded simultaneously on both 35 mm cinefilm and super-VHS videotape with normal images and with spatial filtering of the images (edge enhancement) on a digital cardiac imaging system. The experimental angiographic studies were performed with plexi
Limit on the mass of a long-lived or stable gluino
We reinterpret the generic CDF charged massive particle limit to obtain a
limit on the mass of a stable or long-lived gluino. Various sources of
uncertainty are examined. The -hadron spectrum and scattering cross sections
are modeled based on known low-energy hadron physics and the resultant
uncertainties are quantified and found to be small compared to uncertainties
from the scale dependence of the NLO pQCD production cross sections. The
largest uncertainty in the limit comes from the unknown squark mass: when the
squark -- gluino mass splitting is small, we obtain a gluino mass limit of 407
GeV, while in the limit of heavy squarks the gluino mass limit is 397 GeV. For
arbitrary (degenerate) squark masses, we obtain a lower limit of 322 GeV on the
gluino mass. These limits apply for any gluino lifetime longer than
ns, and are the most stringent limits for such a long-lived or stable gluino.Comment: 15 pages, 5 figures, accepted for publication in JHE
Argyres-Douglas theories and S-duality
This article is distributed under the terms of the Creative Commons
Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are creditedM.B. and T.N. are partly supported by the U.S. Department of Energy under grants DOE-SC0010008, DOE-ARRA-SC0003883, and DOE-DE-SC0007897.
This research was supported in part by the National Science Foundation under Grant No.
NSF PHY11-25915. S.G. is partially supported by the ERC Advanced Grant “SyDuGraM”,
by FNRS-Belgium (convention FRFC PDR T.1025.14 and convention IISN 4.4514.08) and by the “Communaut´e Francaise de Belgique” through the ARC progra
AdS_7/CFT_6, Gauss-Bonnet Gravity, and Viscosity Bound
We study the relation between the causality and the positivity of energy
bounds in Gauss-Bonnet gravity in AdS_7 background and find a precise
agreement. Requiring the group velocity of metastable states to be bounded by
the speed of light places a bound on the value of Gauss-Bonnet coupling. To
find the positivity of energy constraints we compute the parameters which
determine the angular distribution of the energy flux in terms of three
independent coefficients specifying the three-point function of the
stress-energy tensor. We then relate the latter to the Weyl anomaly of the
six-dimensional CFT and compute the anomaly holographically. The resulting
upper bound on the Gauss-Bonnet coupling coincides with that from causality and
results in a new bound on viscosity/entropy ratio.Comment: 21 page, harvmac; v2: reference adde
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