Chronic venous insufficiency (CVI) as an advanced stage of chronic venous disease is a common problem that occurs in approximately 1–5 % of the adult population. CVI has either a nonthrombotic ...(primary) or postthrombotic (secondary) cause involving reflux, obstruction, or a combination of both. The role of venous obstruction is increasingly recognized as a major cause of CVI, with obstructive lesions in the iliocaval segment being markedly more relevant than lesions at the levels of the crural and femoral veins. Approximately 70–80 % of iliac veins develop a variable degree of obstruction following an episode of acute deep venous thrombosis. Nonthrombotic iliac vein obstruction also known as May-Thurner or Cockett’s syndrome is the most common cause of nonthrombotic iliac vein occlusion. While compression therapy is the basis of therapy in CVI, in many cases, venous recanalization or correction of obstructive iliac vein lesions may result in resolution of symptoms. This document reviews the current evidence on iliocaval vein recanalization and provides standards of practice for iliocaval stenting in primary and secondary causes of chronic venous disease.
Metastatic liver disease is the most common cause of death in cancer patients. Complete surgical resection is currently considered the only curative treatment, with only about 25% of patients being ...amenable to surgery. Therefore, a variety of interventional oncologic techniques have been developed for treating secondary liver malignancies. The aim of these therapies is either to allow patients with unresectable tumors to become surgical candidates, provide curative treatment options in nonsurgical candidates, or improve survival in a palliative or even curative approach. Among these interventional therapies are transcatheter therapies such as portal vein embolization, hepatic artery infusion chemotherapy, transarterial chemoembolization, and radioembolization, as well as interstitial techniques, particularly radiofrequency ablation as the most commonly applied technique. The rationale, application and clinical results of each of these techniques are reviewed on the basis of the current literature. Future prospects such as gene therapy and immunotherapy are introduced.
Objectives Multiple studies show orthopedic health problems for medical staff due to wearing radiation protection aprons. The aim of this study was to evaluate the weight pressure on the shoulder as ...a marker of physical strain caused by different radiation-protection devices. Methods For the weight pressure measurement, a pressure sensor (OMD-30-SE-100N, OptoForce, Budapest, Hungary) placed on the left and right shoulder was used. Wearing different radiation protection systems the force measurement system was used to quantify the weight pressure. Measurements were acquired in still standing position and during various movements. Results A mean significant decreasing weight pressure on the shoulder between 74% and 84% (p<0.001) was measured, when the free-hanging radiation protection system was used in comparison to one-piece and two-piece radiation protection aprons and coats. Using two-piece radiation protection aprons, the weight pressure was significantly lower than that of one-piece radiation protection coats. If a belt was used for the one-piece radiation protection coat, the weight pressure on the shoulder was reduced by 32.5% (p = 0.003). For a two-piece radiation protection apron and a one-piece radiation protection coat (with and without belt) a significant different weight pressure distribution between the right and left shoulder could be measured. Conclusions The free-hanging radiation protection system showed a significant lower weight pressure in comparison to the other radiation protection devices. Apart from this, use of a two-piece radiation protection apron or addition of a belt to a radiation protection coat proved to be further effective options to reduce weight pressure.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background
Metal within the scan plane can cause severe artifacts when reconstructing X‐ray computed tomography (CT) scans. Both in clinical use and recent research, normalized metal artifact ...reduction (NMAR) has established as the reference method for correcting metal artifacts, but NMAR introduces inconsistencies within the sinogram, which can cause additional low‐frequency artifacts after image reconstruction.
Purpose
This paper introduces an extension to NMAR by applying a nonlinear scaling function (NLS‐NMAR) to reduce low‐frequency artifacts, which get introduced by the reconstruction of interpolation‐edge‐related sinogram inconsistencies in the normalized sinogram domain.
Methods
After linear interpolation of the metal trace, an NLS function is applied in the prior‐normalized sinogram domain to reduce the impact of the interpolation edges during filtered backprojection. After sinogram denormalization and image reconstruction, the low frequencies of the NLS image are combined with different high frequencies to restore anatomic details. An anthropomorphic dental phantom with removable metal inserts was utilized on two different CT systems to quantitatively assess the artifact reduction performance in terms of HU deviations and the root‐mean‐square‐error within relevant regions of interest. Clinical dental examples were assessed to qualitatively demonstrate the problem of the interpolation‐related blooming as well as to demonstrate the performance of the NLS function to reduce respective artifacts. To quantitatively prove HU consistency, HU values were assessed in central ROIs in the clinical cases. In addition, single clinical cases of a hip replacement and pedicle screws in the spine are shown to demonstrate the method's results in other body regions.
Results
The NLS‐NMAR can minimize the effect of interpolation‐related sinogram inconsistencies and thus reduce resulting hyperdense blooming artifacts. In the phantom results, the reconstructions with the NLS‐NMAR‐corrected low frequencies demonstrate the lowest error. In the qualitative assessment of the clinical data, the NLS‐NMAR shows a tremendous enhancement in image quality, also performing best within all assessed images series.
Conclusion
The NLS‐NMAR provides a small yet effective extension to conventional NMAR by reducing low‐frequency hyperdense metal trace‐interpolation‐related artifacts in computed tomography.
Very short acquisition times and the use of low-kV protocols in CTA demand modifications in the contrast media (CM) injection regimen. The aim of this study was to optimize the use of CM delivery ...parameters in thoraco-abdominal CTA in a porcine model.
Six pigs (55-68 kg) were examined with a dynamic CTA protocol (454 mm scan length, 2.5 s temporal resolution, 70 s total acquisition time). Four CM injection protocols were applied in a randomized order. 120 kV CTA protocol: (A) 300 mg iodine/kg bodyweight (bw), IDR = 1.5 g/s (flow = 5 mL/s), injection time (ti) 12 s (60 kg bw). 70 kV CTA protocols: 150 mg iodine/kg bw: (B) IDR = 0.75 g/s (flow = 2.5 mL/s), ti = 12 s (60 kg bw); (C) IDR = 1.5 g/s (flow = 5 mL/s), ti = 12 s (60 kg bw); (D) IDR = 3.0 g/s (flow = 10 mL/s), ti = 3 s (60 kg bw). The complete CM bolus shape was monitored by creating time attenuation curves (TAC) in different vascular territories. Based on the TAC, the time to peak (TTP) and the peak enhancement were determined. The diagnostic window (relative enhancement > 300 HU), was calculated and compared to visual inspection of the corresponding CTA data sets.
The average relative arterial peak enhancements after baseline correction were 358.6 HU (A), 356.6 HU (B), 464.0 HU (C), and 477.6 HU (D). The TTP decreased with increasing IDR and decreasing ti, protocols A and B did not differ significantly (systemic arteries, p = 0.843; pulmonary arteries, p = 0.183). The delay time for bolus tracking (trigger level 100 HU; target enhancement 300 HU) for single-phase CTA was comparable for protocol A and B (3.9, 4.3 s) and C and D (2.4, 2.0 s). The scan window time frame was comparable for the different protocols by visual inspection of the different CTA data sets and by analyzing the TAC.
All protocols provided sufficient arterial enhancement. The use of a 70 kV CTA protocol is recommended because of a 50% reduction of total CM volume and a 50% reduced flow rate while maintaining the bolus profile. In contrast to pulmonary arterial enhancement, the systemic arterial enhancement improved only slightly increasing the IDR from 1.5 g/s to 3 g/s because of bolus dispersion of the very short bolus (3s) in the lungs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Different two-dimensional (2D) and three-dimensional (3D) imaging techniques are used for procedure planning and selection of prosthesis size before transcatheter aortic valve implantation. This ...study sought to compare different 2D and 3D imaging techniques and determine the accuracy of 3D transoesophageal echocardiography (TEE) for accurate analysis of aortic annulus dimensions.
In 49 consecutive patients with severe aortic stenosis undergoing transcatheter aortic valve implantation angiography, 2D transthoracic echocardiography (TTE), 2D and 3D TEE, and dual-source CT (DSCT) were performed to determine aortic annulus diameters. TTE and 2D TEE provided only one diameter of the aortic annulus. Angiography, DSCT and 3D TEE allowed measurement of diameters in sagittal and coronal views. The distance between aortic annulus and left main coronary artery ostium was measured by angiography, DSCT and 3D TEE.
Sagittal diameters determined by angiography, TTE, 2D TEE, 3D TEE and DSCT were smaller than coronal diameters determined by angiography, 3D TEE and DSCT. Coronal and sagittal diameters determined by 3D TEE were in high agreement with corresponding measurements by DSCT (23.60±1.89 vs 23.46±2.07 mm and 22.19±1.96 vs 22.27±2.01 mm, respectively; mean±SD). There was a high correlation between DSCT and 3D TEE for the definition of coronal and sagittal aortic annulus diameters (r=0.88, SEE=0.89 mm and r=0.77, SEE=1.26 mm, respectively). Correlation of 3D TEE (13.47±1.67 mm) and DSCT (13.64±1.82 mm) in the analysis of the distance between aortic annulus and left main coronary artery ostium was better (r=0.54, SEE=1.55 mm) than between angiography (14.85±3.84 mm) and DSCT (r=0.35, SEE=1.77 mm).
3D imaging techniques should be used to evaluate aortic annulus diameters, as 2D imaging techniques, providing only a sagittal view, underestimate them. 3D TEE provides measurements of aortic annulus diameters similar to those obtained by DSCT.
This study investigated general and subject-specific motivational beliefs from the perspectives of self-determination theory (i.e. intrinsic, identified, introjected, and extrinsic motivation) and ...achievement goal theory (i.e. mastery, performance-approach, and -avoidance goal orientation including the respective classroom goal structures), their interrelations, their stability over time, and their associations with desirable outcomes (i.e. deep-level learning strategies, self-concept of ability). It was hypothesized that motivational beliefs are interrelated but demonstrate a distinct correlational pattern depending on whether they were assessed as general or subject-specific motivation. In addition, motivational beliefs were hypothesized to relate to learning strategies and ability beliefs.
Medical students (
= 146) participated in this longitudinal study with measurement points at the beginning and end of a semester. The questionnaire included established motivational scales to assess motivational beliefs and desirable outcomes. Measurement models were tested using confirmatory factor analyses; correlations of scale means were investigated to assess the nomological network of motivational beliefs.
As expected, intrinsic and identified motivation were associated with mastery goal orientation and with desirable outcome variables, such as the use of deep-level learning strategies. General and subject-specific motivation exhibited distinct correlational patterns. Motivation was relatively stable over time. Results did not confirm the factor structure of classroom goal structure.
The study emphasizes the benefit of a subject-specific conceptualization of motivation and the need for a careful adaptation of theoretical constructs from the secondary school context to make them fruitful for the promotion of medical students' motivation. Medical teachers can use established motivational interventions (e.g. using an individual frame of reference for feedback) to support students' adaptive motivational beliefs (e.g. self-determined motivation, mastery goals). Given the subject specificity of motivation, it seems beneficial to promote adaptive motivation in the respective medical specialty regardless of students' general motivational characteristics.
Abstract
Background
The increasing number of minimally invasive fluoroscopy-guided interventions is likely to result in higher radiation exposure for interventional radiologists and medical staff. ...Not only the number of procedures but also the complexity of these procedures and therefore the exposure time as well are growing. There are various radiation protection means for protecting medical staff against scatter radiation. This article will provide an overview of the different protection devices, their efficacy in terms of radiation protection and the corresponding dosimetry.
Method
The following key words were used to search the literature: radiation protection, eye lens dose, radiation exposure in interventional radiology, cataract, cancer risk, dosimetry in interventional radiology, radiation dosimetry.
Results and Conclusion
Optimal radiation protection always requires a combination of different radiation protection devices. Radiation protection and monitoring of the head and neck, especially of the eye lenses, is not yet sufficiently accepted and further development is needed in this field. To reduce the risk of cataract, new protection glasses with an integrated dosimeter are to be introduced in clinical routine practice.
Key Points:
A combination of personal radiation protection devices and optimized dosimetry improves the safety of medical staff.
Citation Format
König AM, Etzel R, Thomas RP et al. Personal Radiation Protection and Corresponding Dosimetry in Interventional Radiology: An Overview and Future Developments. Fortschr Röntgenstr 2019; 191: 512 – 521
Zusammenfassung
Hintergrund
Röntgenstrahlen haben ein sehr breites Anwendungsspektrum in der Medizin. Mit dem Trend zu minimalinvasiven Eingriffen steigen besonders die Zahlen Computertomografie- (CT) und durchleuchtungsgesteuerter Interventionen. Mit der zunehmenden Komplexität der Eingriffe steigt außerdem die Untersuchungsdauer und damit häufig auch die Expositionsdauer. Um das medizinische Personal vor allem vor der Streustrahlung zu schützen, gibt es eine Vielzahl von persönlichen Strahlenschutzmitteln. Diese Übersichtsarbeit soll einen Überblick über die verfügbaren Systeme, ihre Effektivität bezüglich des persönlichen Strahlenschutzes und der entsprechenden Dosimetrie geben.
Methode
Literaturrecherche, vor allem in pubmed mit den Schlüsselwörtern: Strahlenschutz, Augenlinsendosis, Strahlenexposition in der interventionellen Radiologie, Katarakt, Tumorrisiko, Dosimetrie in der interventionellen Radiologie und Strahlendosimetrie.
Ergebnisse und Schlussfolgerung
Ein optimaler Strahlschutz sieht immer eine Kombination aus unterschiedlichen Strahlenschutzmitteln bzw. Methoden vor. Der Strahlenschutz und das Monitoring des Kopf-Hals-Bereichs, vor allem der Augenlinse, hat weiterhin Entwicklungs- und Akzeptanzbedarf. Hier werden neue Bleiglas-Brillen mit integrierten Dosimetern erwartet, damit zukünftig die genaue Dosis bestimmt und somit das Kataraktrisiko reduziert werden kann.
Kernaussagen:
Die richtige Kombination aus Strahlenschutzmittel und entsprechender Dosimetrie erhöht die Sicherheit beim Umgang mit Röntgenstrahlen.
Zitierweise
König AM, Etzel R, Thomas RP et al. Personal Radiation Protection and Corresponding Dosimetry in Interventional Radiology: An Overview and Future Developments. Fortschr Röntgenstr 2019; 191: 512 – 521
The aim of this study was to introduce and evaluate a new metal artifact reduction framework (iMARv2) that addresses the drawbacks (residual artifacts after correction and user preferences for image ...quality) associated with the current clinically applied iMAR.
A new iMARv2 has been introduced, combining the current iMAR with new modular components to remove residual metal artifacts after image correction. The postcorrection image impression is adjustable with user-selectable strength settings. Phantom scans from an energy-integrating and a photon-counting detector CT were used to assess image quality, including a Gammex phantom and anthropomorphic phantoms. In addition, 36 clinical cases (with metallic implants such as dental fillings, hip replacements, and spinal screws) were reconstructed and evaluated in a blinded and randomized reader study.
The Gammex phantom showed lower HU errors compared with the uncorrected image at almost all iMAR and iMARv2 settings evaluated, with only minor differences between iMAR and the different iMARv2 settings. In addition, the anthropomorphic phantoms showed a trend toward lower errors with higher iMARv2 strength settings. On average, the iMARv2 strength 3 performed best of all the clinical reconstructions evaluated, with a significant increase in diagnostic confidence and decrease in artifacts. All hip and dental cases showed a significant increase in diagnostic confidence and decrease in artifact strength, and the improvements from iMARv2 in the dental cases were significant compared with iMAR. There were no significant improvements in the spine.
This work has introduced and evaluated a new method for metal artifact reduction and demonstrated its utility in routine clinical datasets. The greatest improvements were seen in dental fillings, where iMARv2 significantly improved image quality compared with conventional iMAR.
Aging involves reductions in exercise total limb blood flow and exercise capacity. We hypothesized that this may involve early age-related impairments of skeletal muscle microvascular responsiveness ...as previously reported for insulin but not for exercise stimuli in humans.
Using an isometric exercise model, we studied the effect of age on contrast-enhanced ultrasound (CEUS) parameters, i.e. microvascular blood volume (MBV), flow velocity (MFV) and blood flow (MBF) calculated from replenishment of Sonovue contrast-agent microbubbles after their destruction. CEUS was applied to the vastus lateralis (VLat) and intermedius (VInt) muscle in 15 middle-aged (MA, 43.6±1.5 years) and 11 young (YG, 24.1±0.6 years) healthy males before, during, and after 2 min of isometric knee extension at 15% of peak torque (PT). In addition, total leg blood flow as recorded by femoral artery Doppler-flow. Moreover, fiber-type-specific and overall capillarisation as well as fiber composition were additionally assessed in Vlat biopsies obtained from CEUS site. MA and YG had similar quadriceps muscle MRT-volume or PT and maximal oxygen uptake as well as a normal cardiovascular risk factors and intima-media-thickness.
During isometric exercise MA compared to YG reached significantly lower levels in MFV (0.123±0.016 vs. 0.208±0.036 a.u.) and MBF (0.007±0.001 vs. 0.012±0.002 a.u.). In the VInt the (post-occlusive hyperemia) post-exercise peaks in MBV and MBF were significantly lower in MA vs. YG. Capillary density, capillary fiber contacts and femoral artery Doppler were similar between MA and YG.
In the absence of significant age-related reductions in capillarisation, total leg blood flow or muscle mass, healthy middle-aged males reveal impaired skeletal muscle microcirculatory responses to isometric exercise. Whether this limits isometric muscle performance remains to be assessed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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