| 1. |
- Sandgren, T., et al.
(författare)
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Arterial dimensions in the lower extremities of patients with abdominal aortic aneurysms - No indications of a generalized dilating diathesis
- 2001
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Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 34:6, s. 1079-1084
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study assessed whether there is a dilating diathesis in peripheral arteries of patients with abdominal aortic aneurysms (AAAs). Methods: The anteroposterior diameters of the common femoral artery (CFA) and popliteal artery (PA) were measured in 183 consecutive patients with an AAA (158 men, 25 women, age range, 57-78 years) before elective surgery on the AAA and compared with that of healthy age-matched control subjects. The diameter registrations were performed on the right leg by using a noninvasive echo-tracking ultrasound scanning technique. Results: Eight CFA aneurysms and four PA aneurysms were found in the male patients with AAAs. Of the patients with AAAs in the CFA and in the PA who were investigated, 46% and 49%, respectively, were affected by peripheral vascular occlusive disease (PVOD). The CFA diameters in the patients with AAAs were 97.8% of those in healthy control subjects (P = not significant [NS]). After exclusion of the CFA aneurysms, the diameters were 92.7% of those in healthy control subjects (P = .0003). If patients with PVOD were also excluded, the CFA diameters were 95.2% of those in healthy control subjects (P = .022). The PA diameters in the patients with AAAs were 97.8% of those in healthy control subjects (P = NS). If PA aneurysms were excluded, the diameters were 94.4% of those in healthy control subjects (P = .0003). If patients with PVOD were also excluded, the PA diameters were 96.1% of those in healthy control subjects (P = NS). Conclusion: After excluding the few patients with AAAs who had peripheral aneurysmal disease and the patients with PVOD, no dilating diathesis in CFAs and PAs was found. This supports the hypothesis that specific genetic, or other factors, not present in most AAAs are responsible for the occurrence of concomitant peripheral aneurysms. Furthermore, the generalized vascular dilating diathesis seen in some patients seems to be a specific entity that was not necessarily affiliated with AAA disease.
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| 2. |
- Bjarnegård, Niclas, et al.
(författare)
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The effect of sympathetic stimulation on proximal brachial artery mechanics in humans : differential behaviour within the length of the brachial artery
- 2004
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 182:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Aims: The mechanical properties of arteries play a major role in the regulation of blood pressure and cardiac performance. The effect of sympathetic stimulation on the mechanical properties of the proximal brachial artery was analysed in 18 healthy volunteers, nine young (25 ± 2 years) and nine elderly (69 ± 2 years).Methods: A non-invasive ultrasonic echo-tracking system for measurement of systolic/diastolic variation of the proximal brachial artery diameter in combination with intra-arterial pressure measurements was used to determine wall mechanics. The pressure–diameter (P–D) relationship, distensibility coefficient (DC), compliance coefficient (CC) and stiffness(β) were obtained at rest and during sympathetic stimulation induced by lower body negative pressure (LBNP).Results: The peripheral vascular resistance increased by 100 and 72%, respectively in the young and elderly during LBNP (P < 0.001). Simultaneously, the mechanical properties of the proximal brachial artery remained unaltered, as estimated from both P–D relationship and stiffness in young (β-index rest: 5.2 ± 0.9, LBNP: 5.5 ± 1.3, NS) as well as elderly (β-index rest: 13.6 ± 4.6, LBNP: 16.1 ± 4.7, NS).Conclusions: LBNP-induced sympathetic activation does not change proximal brachial artery mechanics, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behaviour is within the length of the brachial artery, where the site of transition from elastic to muscular wall structure needs to be specified in future studies.
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| 3. |
- Debasso, Rachel, 1978-, et al.
(författare)
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The popliteal artery, an unusual muscular artery with wall properties similar to the aorta : Implications for susceptibility to aneurysm formation?
- 2004
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Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 39:4, s. 836-842
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The popliteal artery is, after the aorta, the most common site for aneurysm formation. Why the popliteal artery is more susceptible than other peripheral muscular arteries is unknown. An important factor may be differences in arterial wall composition as compared with other peripheral muscular arteries, which in turn affect wall properties. These are however unknown. We studied the mechanical wall properties of the popliteal artery in healthy subjects. Material and Methods: An ultrasound echo-tracking system was used to measure pulsatile changes in popliteal diameter in 108 healthy subjects (56 female, 52 male, age range, 9-82 years). In combination with blood pressure, stiffness (β), strain, cross-sectional artery wall compliance coefficient (CC), and distensibility coefficient (DC) were calculated. Intima-media thickness (IMT) was registered with a Philips P700 ultrasound scanner. Results: The popliteal diameter increased with age, and was larger in male subjects than in female subjects (P < .001). Fractional diameter change (strain) decreased with age (P < .001), and strain values were lower in male subjects than in female subjects (P < .01). Accordingly, stiffness increased with age (P < .001), with higher stiffness values in male subjects (P < .01). DC decreased with age (P < .001), with lower DC values in male subjects (P < .01). CC decreased with age, with no difference between genders (P < .001). IMT increased with age (P < .001), with higher IMT values in male subjects (P < .001). The increase in IMT did not affect distensibility. Conclusion: The wall properties of the popliteal artery are affected by age and gender, not only with an increase in diameter, but also with an age-related decrease in distensibility, with male subjects having lower distensibility than in female subjects. This seems not to be the behavior of a true muscular artery, but of a central elastic artery, such as the aorta, and might have implications for susceptibility to arterial dilatation, as well as the association of aneurysm formation between the aorta and the popliteal artery.
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| 4. |
- Kopylov, Philippe, et al.
(författare)
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Norian SRS versus functional treatment in redisplaced distal radial fractures : A randomized study in 20 patients
- 2002
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Ingår i: Journal of Hand Surgery - British and European Volume. - : SAGE Publications. - 0266-7681 .- 1532-2211. ; 27 B:6, s. 538-541
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Tidskriftsartikel (refereegranskat)abstract
- We compared the use of Norian SRS, an injectable calcium phosphate bone cement, with functional treatment of redisplaced distal radial fractures in a prospective randomized study of 20 patients. The redisplaced fractures were either rereduced and stabilized by Norian SRS, or the displaced position was accepted and was not rereduced. All wrists were immobilized in a short-arm dorsal splint for 1 week, followed by a removable splint for another 3 weeks. The chosen primary effect variable was grip strength at 7 weeks, and this did not differ between the two treatment groups. The clinical results at 6 months in both groups were similar. We conclude that aggressive treatment of redisplaced fractures of the distal radius may be unnecessary in most women aged 50 years or more.
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| 5. |
- Alm Carlsson, Gudrun
(författare)
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Bragg-Gray Dosimetry : Theory of Burch
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The theoretical approach to Bragg-Gray dosimetry is: a Bragg-Gray cavity is a cavity (detector) so small that, when inserted into a medium, it does not disturb the fluence of charged particles existing in the medium. This means that the ideal Bragg-Gray cavity (detector) is one of infinitesimal dimensions, a "point" detector. In practice, such detectors do not exist but many real detectors may, in a first approximation, be treated as Bragg-Gray detectors to a high degree of accuracy. Corrections needed (so called perturbation corrections) to account for the deviation of the signal from a practical detector from that of an ideal one has been treated by, e.g., ICRU 1984, Alm Carlsson, 1985, Svensson and Brahme 1986, Alm Carlsson 1987. Derivation of "perturbation corrections" needs careful consideration and under-standing of the ideal case, i.e., that from which deviations are to be corrected for. The ideal case of a Bragg-Gray detector has been treated by Bragg 1912, Gray 1936, Laurence 1937, Spencer and Attix 1955 and Burch 1955. The formulation of Bragg-Gray theory by Spencer and Attix has found wide practical application and has been treated in detail elsewhere. The theory of Burch treats the same problem as did Spencer and Attix, viz., the significance of generation and slowing down of delta-particles in both medium and detector. Burch treated the problem in considerable detail but didn't find a solution for practical calculations. From a physical point of view, however, there is much to learn from Burch's approach. Also, his treatment of so called track ends, evaluated in some detail by Burch 1957, has been adapted in later versions of the Spencer-Attix formulation of Bragg-Gray theory.
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| 6. |
- Alm Carlsson, Gudrun
(författare)
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Fanos Teorem
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I ett oändligt medium erhålles en fullt uppbyggd fluens i alla punkter av mediet. I ett ändligt medium erhålles inte full uppbyggnad av fluensen på avstånd mindre än en maximal "partikelräckvidd" från begränsningsytorna. Fanos teorem har visats gälla för alla punkter i ett oändligt medium men kan endast gälla i det inre av ett ändligt medium där förhållandena är ekvivalenta med dem i det oändliga mediet.
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| 7. |
- Alm Carlsson, Gudrun
(författare)
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Spencer-Attix Cavity Theory
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The cavity theory by Spencer and Attix treats the energy deposition in a Bragg-Gray (B-G) cavity (detector). Originally the theory was developed for the case of a B-G detector inside a medium irradiated with photons and assuming electronic equilibrium in the medium at the position of the cavity. The theory is also applicable in media irradiated with other types of uncharged ionizing particles (e.g., neutrons) and charged particles such as electrons and protons. The special case of photon irradiation under CPE (charged particle equilibrium) conditions was coupled to a model for calculating the energy spectrum of the equilibrium fluence of electrons in the undisturbed medium. For other situations, e.g., in a medium externally irradiated with electrons, the problem is to evaluate the energy spectrum of the electron fluence at the point considered in the medium. Today, this is mostly accomplished using Monte Carlo simulations. A Bragg-Gray cavity is regarded to be so small that: the energy imparted to the cavity from electrons released by photons in the cavity is negligible compared to the energy imparted from electrons released by photons in the surrounding medium and passing through the cavity the cavity should not disturb the fluence of electrons in the medium, i. e., the fluence of electrons traversing the cavity is assumed to be identical to that existing at the point of interest in the medium in the absence of the cavity.
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| 8. |
- Alm Carlsson, Gudrun
(författare)
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Spencer-Attix kavitetsteori
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Spencer-Attix kavitetsteori behandlar energideponeringen i en Bragg-Gray kavitet (detektor) inuti ett medium bestrålat med fotoner och med elektronjämvikt i mediet på kavitetens plats. Med en Bragg-Gray kavitet menas en kavitet så liten att energideponeringen i kaviteten från elektroner frigjorda av fotoner i kaviteten är försumbar jämfört med energideponeringen från elektroner frigjorda av fotoner i omgivande mediet och som passerar in kaviteten kaviteten skall inte nämnvärt störa fluensen av elektronerna i mediet, dvs kaviteten antas i varje punkt genomkorsad av samma fluens av elektroner, som finns i mediet i frånvaro av kaviteten
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| 9. |
- Arlig, A, et al.
(författare)
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Attenuation correction in quantitative SPECT of cerebral blood flow: a Monte Carlo study
- 2000
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 45:12, s. 3847-3859
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Tidskriftsartikel (refereegranskat)abstract
- Monte Carlo simulation has been used to produce projections from a voxel-based brain phantom, simulating a 99mTc-HMPAO single photon emission computed tomography (SPECT) brain investigation. For comparison, projections free from the effects of attenuation and scattering were also simulated, giving ideal transaxial images after reconstruction. Three methods of attenuation correction were studied: (a) a pre-processing method, (b) a post-processing uniform method and (c) a post-processing non-uniform method using a density map. The accuracy of these methods was estimated by comparison of the reconstructed images with the ideal images using the normalized mean square error, NMSE, and quantitative values of the regional cerebral blood flow, rCBF. A minimum NMSE was achieved for the effective linear attenuation coefficient mu(eff) = 0.07 (0.09) cm(-1) for the uniform(pre) method, the effective mass attenuation coefficient mu(eff)/rho = 0.08 (0.10) cm2 g(-1) for the uniform(post) method and mu(eff)/rho = 0.12 (0.13) cm2 g(-1) for the non-uniform(post) method. Values in parentheses represent the case of dual-window scatter correction. The non-uniform(post) method performed better, as measured by the NMSE, both with and without scatter correction. Furthermore, the non-uniform(post) method gave, on average, more accurate rCBF values. Although the difference in rCBF accuracy was small between the various methods, the same method should be used for patient studies as for the reference material.
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| 10. |
- Bjarnegård, Niclas, et al.
(författare)
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Age affects proximal brachial artery stiffness : differential behaviour within the length of the brachial artery?
- 2003
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 29:8, s. 1115-1121
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Tidskriftsartikel (refereegranskat)abstract
- With increasing age, the diameter of central elastic arteries increases, whereas their distensibility decreases. The purpose of this study was to investigate the mechanical properties of the proximal brachial artery in relation to age and gender. Distensibility coefficient (DC), stiffness and compliance coefficient (CC) were calculated in 136 healthy males and females (range 9-82 y) using echo-tracking sonography. CC decreased with age in both genders, but CC was higher in males. Stiffness increased and DC decreased with age in an exponential manner, without any differences between genders. In conclusion, as in central elastic arteries, the distensibility of the proximal brachial artery decreases with age, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behavior is within the length of the brachial artery. In future studies using the brachial artery, the examination site needs to be defined.
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