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This article presents a demonstration of the improved performance of an X-ray free-electron laser (FEL) using the optical klystron mechanism and helical undulator configuration, in comparison with the common planar undulator configuration without optical klystron. The demonstration was carried out at Athos, the soft X-ray beamline of SwissFEL. Athos has variable-polarization undulators, and small magnetic chicanes placed between every two undulators to fully exploit the optical klystron. It was found that, for wavelengths of 1.24â nm and 3.10â nm, the required length to achieve FEL saturation is reduced by about 35% when using both the optical klystron and helical undulators, with each effect accounting for about half of the improvement. Moreover, it is shown that a helical undulator configuration provides a 20% to 50% higher pulse energy than planar undulators. This work represents an important step towards more compact and high-power FELs, rendering this key technology more efficient, affordable and accessible to the scientific community.
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The ability to freely control the polarization of X-rays enables measurement techniques relying on circular or linear dichroism, which have become indispensable tools for characterizing the properties of chiral molecules or magnetic structures. Therefore, the demand for polarization control in X-ray free-electron lasers is increasing to enable polarization-sensitive dynamical studies on ultrafast time scales. The soft X-ray branch Athos of SwissFEL was designed with the aim of providing freely adjustable and arbitrary polarization by building its undulator solely from modules of the novel Apple X type. In this paper, the magnetic model of the linear inclined and circular Apple X polarization schemes are studied. The polarization is characterized by measuring the angular electron emission distributions of helium for various polarizations using cold target recoil ion momentum spectroscopy. The generation of fully linear polarized light of arbitrary angle, as well as elliptical polarizations of varying degree, are demonstrated.
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The isolated III grade lateral collateral ligament injuries are rare, and there is limited literature available on their management. We report 3 cases of professional soccer players with isolated distal lateral collateral ligament III grade injury, confirmed by MRI studies. After undergoing MRI examinations, all three players resumed competitive activity without resting and experienced no consequences regarding joint stability. We assessed the significance of the lateral collateral ligament in providing lateral stabilization to the knee joint in professional footballers with clinical tears of the lateral collateral ligament. The other structures of posterolateral area that remain intact contribute to joint stability, and the lateral collateral ligament's extra-articular position appears to expedite the ligament's healing process. Therefore, we propose a possible conservative treatment approach, mostly for professional athletes and adolescent patients, involving a rehabilitation plan without the need for surgery.
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Traumatismos do Joelho , Ligamentos Laterais do Tornozelo , Futebol , Adolescente , Humanos , Traumatismos do Joelho/cirurgia , Atletas , Imageamento por Ressonância MagnéticaRESUMO
PURPOSE: To assess whether a correlation between the calcaneal pronation angle and the presence of internal plantar arch overload signs (such as upper-medial spring ligament lesion, posterior tibial tendon tenosynovitis, etc.) could lead to a better understanding of coxa pedis pathology. MATERIAL AND METHODS: One hundred ankle MRIs of consecutive patients were retrospectively reviewed measuring the calcaneal pronation angle and either the presence or absence of internal plantar arch overload signs. Next, the association of overload signs with increasing pronation angle was evaluated to establish a cut-off point beyond which coxa pedis pathology could be defined. RESULTS: The tibial-calcaneal angle values in patients with and without effusion proved to be significantly different (p < 0.0001). The tibial-calcaneal angle values in patients with and without oedema also demonstrated a significant difference (p < 0.0056). Regarding posterior tibial tendon, a significant difference was found between the two groups (p < 0.0001). For plantar fascia enthesopathy, the result was borderline significant (p < 0.054). A linear correlation was found between the value of pronation angle and the extent of spring ligament injury (p < 0.0001). In contrast, no correlation with age was found. CONCLUSION: In conclusion, the literature associates medial longitudinal plantar arch overload with posterior tibial tendinopathy and spring ligament complex injuries. Our data show that both injuries are highly correlated with increased calcaneal pronation angle, which could be considered a predictive sign of internal plantar arch overload, prior to the development of the associated signs.
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Calcâneo , Imageamento por Ressonância Magnética , Pronação , Humanos , Masculino , Feminino , Imageamento por Ressonância Magnética/métodos , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto , Calcâneo/diagnóstico por imagem , Idoso , Pronação/fisiologia , Valor Preditivo dos Testes , Adolescente , Idoso de 80 Anos ou maisRESUMO
The Paul Scherrer Institute is implementing laser-based seeding in the soft X-ray beamline (Athos) of its free-electron laser, SwissFEL, to enhance the temporal and spectral properties of the delivered photon pulses. This technique requires, among other components, two identical modulators for coupling the electron beam with an external laser with a wavelength range between 260 and 1600â nm. The design, magnetic measurements results, alignment, operation and also details of the novel and exotic magnetic configuration of the prototype are described.
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OBJECTIVES: To provide quantitative anatomical parameters in patients with and without non-traumatic multidirectional instability using MR arthrography (MR-a). MATERIALS AND METHODS: One hundred and seventy-six MR-a performed from January 2020 to March 2021 were retrospectively evaluated. Patients were divided according to the presence of clinically diagnosed multidirectional shoulder instability (MDI). Each MR-a was performed immediately after intra-articular injection of 20 ml of gadolinium using the anterior approach. The width of the axillary recess, the width of the rotator interval, and the circumference of the glenoid were measured by three independent radiologists, choosing the average value of the measurements. The difference between the mean values of each of the three parameters between the two study groups was then assessed. RESULTS: Thirty-seven patients were included in the study (20 in the MDI group, 17 in the control group). The mean axillary recess width in the MDI group was significantly greater than in the control group (t(33) = 3.15, p = .003); rotator interval width and glenoid circumference measurements were not significantly different (t(35) = 1.75, p = .08 and t(30) = 0,51, p = .6, respectively). CONCLUSIONS: Inferior capsular redundancy may be an important predisposing factor in MDI, while glenoid circumference is not related to MDI. The relationship between the width of the rotator interval and shoulder instability remains debated.
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Instabilidade Articular , Articulação do Ombro , Artrografia , Gadolínio , Humanos , Instabilidade Articular/diagnóstico por imagem , Instabilidade Articular/patologia , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Estudos Retrospectivos , Ombro/diagnóstico por imagem , Articulação do Ombro/diagnóstico por imagem , Articulação do Ombro/patologiaRESUMO
PURPOSE: The aim is to investigate whether contrast medium can improve accuracy in the assessment of healing muscle injury in high-level professional athletes. MATERIALS AND METHODS: Our series is a retrospective study including the records of 22 players (mean age 28 ± 5 SD) with lower limbs muscle injuries type 3a (Mueller-Wohlfarth). All athletes received two MRIs: the day after the injury and before resuming heavy effort activities. Contrast medium uptake was measured in the second MRI by comparing the mean enhancement at the lesion site (ME) with that of the healthy contralateral muscle (HM). The result is a percentage referred to as muscular contrast index (MC index). The difference between the mean MC index value between athletes with and without re-injury was assessed with both the Mann-Whitney and the Kruskal-Wallis test. RESULTS: Twenty-nine muscle injuries matched the inclusion criteria. The mean MC index values, adjusted for the variable of time elapsed between the last contrast examination and return to the field, were significantly different in the two study groups (p < .001). CONCLUSION: The contrast medium in the follow-up of muscle injuries may be useful in determining the degree of scar stability in a healing injury. Injuries with a high MC index were found to be 'unstable', with a higher rate of recurrence than those with a low MC index. Resumption of competitive activity after achieving not only clinical resolution but also a satisfactory MC index value may increase the safety of return to the field and reduce the recurrence rate.
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Traumatismos em Atletas , Volta ao Esporte , Adulto , Atletas , Traumatismos em Atletas/diagnóstico por imagem , Traumatismos em Atletas/prevenção & controle , Humanos , Extremidade Inferior/diagnóstico por imagem , Imageamento por Ressonância Magnética , Músculos/lesões , Recidiva , Estudos Retrospectivos , Adulto JovemRESUMO
PURPOSE: The aim of the study is to evaluate which MRI parameters achieve the best degree of inter-individual concordance in the description of meniscal fibrocartilage, regarding its morphology, signal and position. MATERIALS AND METHODS: Eighty-nine knee MRIs were included in the study, retrospectively re-evaluated by three radiologists who completed a binary report (normal/abnormal) describing the meniscus signal, position relative to the tibial plateau margin and morphology. The inter-individual concordance value was calculated using Cohen's test. RESULTS: We obtained different inter-individual concordance values according to the parameters considered. The concordance was poor in the description of the meniscal position relative to the tibial plateau margin (average k = 0.6); the result was comparable in the description of the meniscal morphology (average k = 0.56). The best results were obtained with the meniscal signal analysis (average k = 0.8). CONCLUSION: To the best of our knowledge, there are no studies in the literature assessing the concordance between multiple readers in the description of the parameters we studied. The results we obtained suggest that the most reliable parameter for describing meniscal fibrocartilage is its signal intensity, whereas morphology and position may lead to different interpretations that are not always unequivocal.
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Menisco , Lesões do Menisco Tibial , Humanos , Imageamento por Ressonância Magnética/métodos , Meniscos Tibiais/diagnóstico por imagem , Menisco/diagnóstico por imagem , Estudos Retrospectivos , Lesões do Menisco Tibial/diagnóstico por imagemRESUMO
BACKGROUND: The purpose of this work is to characterize the anatomy of the intraarticular portion of the long head of the biceps tendon (long head biceps tendon) using magnetic resonance (MR) arthrography by investigating whether anatomical variants may facilitate the onset of a supraequatorial lesion (superior labral anterior to posterior, SLAP). MATERIALS AND METHODS: In 482 shoulder MR arthrographies, we considered the anatomical variants of the intraarticular portion of the long head of the biceps tendon classified according to Dierickx's arthroscopic classification; lesions of supraequatorial structures were considered in the data analysis. For each anatomical variant, correlation with SLAP and the odd ratio were statistically evaluated, using Fisher's exact (or chi-squared) test and logistic regression analysis, respectively. RESULTS: In the mesotenon-type variant, the SLAP frequency was higher than expected [χ2 (df = 4) = 14.9, p = 0.005] with a higher risk of developing a type I SLAP (p = 0.0003). In the adherent-type variant, the type II SLAP frequency was higher than expected [χ2 (df = 3) = 18.1, p = 0.0004] with a higher risk of developing type II SLAP (p = 0.0001). Two cases of "split" (SPL) long head biceps tendon had III and type IV SLAP, respectively. These patients have a higher risk for type IV SLAP [odds ratio (OR) 19.562, 95% confidence interval (CI) 1.604-238.541, p = 0.001]. An increased risk of developing SLAP type II was calculated for male subjects (OR 3.479, 95% CI 1.013-11.951, p = 0.019). CONCLUSIONS: It is possible that adherence of the long head biceps tendon to the supraspinatus more often predisposes to a lesion of the superior glenoid labrum (SLAP), in view of the close relationships between the fibrocartilage and the bicipital anchor, probably related to the limited excursion of the intraarticular long head biceps tendon.
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Lesões do Ombro , Articulação do Ombro , Artrografia , Artroscopia , Humanos , Espectroscopia de Ressonância Magnética , Masculino , Lesões do Ombro/patologia , Articulação do Ombro/diagnóstico por imagem , Articulação do Ombro/cirurgia , Tendões/diagnóstico por imagemRESUMO
OBJECTIVE: To evaluate the long-term evolution of matrix-induced autologous chondrocyte implantation (MACI) with magnetic resonance (MR) arthrography and verify the correlation between radiological and clinical findings. MATERIALS AND METHODS: Twenty-six patients (20 m/6f) were diagnosed with knee chondral injuries and treated with MACI implantation. Each patient received MR arthrography and clinical examination at mid-term (range 22-36 months) and long term (range 96-194 months) after surgery. MR arthrography was performed with dedicated coil and a 1.5-Tesla MR unit. The modified MOCART scale was used to evaluate the status of chondral implants. Implant coating, integration to the border zone, and the surface and structure of the repaired tissue were evaluated. Presence of bone marrow oedema was evaluated. The Cincinnati Knee Rating System (CKRS) was used for clinical assessment. RESULTS: At long term, 4/26 patients had complete alignment; 5/26 had a complete integration of the margins; in 4/26 cases, the implant surface was undamaged; in 14/26 cases, the reparative tissue was homogeneous. In 9/26 cases, the implant showed isointense signal compared to articular cartilage, while the presence of subchondral bone oedema was documented in 19/26 cases. The average radiological score decreased from 59.2 (mid-term) to 38.6 (long term). The average clinical score decreased from 8.9 to 8.3. CONCLUSIONS: Decrease in clinical results was not significant (0.6 points p = .06), but mMOCART scores decreased significantly (p = .00003). Although imaging studies showed deterioration of the grafts, the patients did not have significant clinical deterioration (231/250).
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Cartilagem Articular , Artrografia , Cartilagem Articular/diagnóstico por imagem , Cartilagem Articular/cirurgia , Condrócitos , Seguimentos , Humanos , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/cirurgia , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Transplante Autólogo , Resultado do TratamentoRESUMO
PURPOSE: To study distractive muscle injuries applying US and MRI specific classifications and to find if any correlation exists between the results and the return to sport (RTS) time. The second purpose is to evaluate which classification has the best prognostic value and if the lesions extension correlates with the RTS time. METHODS: A total of 26 male, professional soccer players (age 21.3 ± 5.6), diagnosed with traumatic muscle injury of the lower limbs, received ultrasound and MRI evaluation within 2 days from the trauma. Concordance between US and MRI findings was investigated. The relationships between MRI and US based injury grading scales and RTS time were evaluated. Correlation between injuries' longitudinal extension and RTS time was also investigated. RESULTS: The correlation between US and MRI measurements returned a Spearman value of rs = 0.61 (p = .001). Peetrons and Mueller-Wohlfahrt grading scales correlations with RTS time were r = 0.43 (p = .02) and r = 0.83 (p = < .001). The lesion's extension correlation with RTS time was r = 0.63 (p < .001). The correlation between the site of the lesion and its location with the RTS time were rs = 0.2 and rs = 0.25. CONCLUSIONS: Both US and MRI can be used as prognostic indicators along with the Peetrons (US) and the Mueller-Wohlfahrt (MRI) classifications. MRI is more precise and generates more reproducible results. The lesion craniocaudal extension must be considered as a prognostic indicator, while the injury location inside the muscle or along its major axis has doubtful significance.
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Imageamento por Ressonância Magnética , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/lesões , Volta ao Esporte/estatística & dados numéricos , Futebol/lesões , Adolescente , Adulto , Traumatismos em Atletas/classificação , Traumatismos em Atletas/diagnóstico por imagem , Correlação de Dados , Humanos , Masculino , Prognóstico , Fatores de Tempo , Ultrassonografia , Adulto JovemRESUMO
The list of authors in the paper by Juranic et al. (2018) [J. Synchrotron Rad. 25, 1238-1248] is corrected.
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The SwissFEL soft X-ray free-electron laser (FEL) beamline Athos will be ready for user operation in 2021. Its design includes a novel layout of alternating magnetic chicanes and short undulator segments. Together with the APPLE X architecture of undulators, the Athos branch can be operated in different modes producing FEL beams with unique characteristics ranging from attosecond pulse length to high-power modes. Further space has been reserved for upgrades including modulators and an external seeding laser for better timing control. All of these schemes rely on state-of-the-art technologies described in this overview. The optical transport line distributing the FEL beam to the experimental stations was designed with the whole range of beam parameters in mind. Currently two experimental stations, one for condensed matter and quantum materials research and a second one for atomic, molecular and optical physics, chemical sciences and ultrafast single-particle imaging, are being laid out such that they can profit from the unique soft X-ray pulses produced in the Athos branch in an optimal way.
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A new and simple method to generate X-ray free-electron-laser radiation with unprecedented spectral bandwidth above the 10% level is presented. The broad bandwidth is achieved by sending a transversely tilted beam through a transverse-gradient undulator. The extent of the bandwidth can easily be controlled by variation of the beam tilt or the undulator gradient. Numerical simulations confirm the validity and feasibility of this method.
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An optimization of the undulator layout of X-ray free-electron-laser (FEL) facilities based on placing small chicanes between the undulator modules is presented. The installation of magnetic chicanes offers the following benefits with respect to state-of-the-art FEL facilities: reduction of the required undulator length to achieve FEL saturation, improvement of the longitudinal coherence of the FEL pulses, and the ability to produce shorter FEL pulses with higher power levels. Numerical simulations performed for the soft X-ray beamline of the SwissFEL facility show that optimizing the advantages of the layout requires shorter undulator modules than the standard ones. This proposal allows a very compact undulator beamline that produces fully coherent FEL pulses and it makes possible new kinds of experiments that require very short and high-power FEL pulses.
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Bioplastics possess the potential to foster a sustainable circular plastic economy, but their end-of-life is still challenging. To sustainably overcome this problem, this work proposes the hydrothermal carbonization (HTC) of residual bioplastics as an alternative green path. The focus is on cellulose acetate - a bioplastic used for eyewear, cigarette filters and other applications - showing the proof of concept and the chemistry behind the conversion, including a reaction kinetics model. HTC of pure and commercial cellulose acetates was assessed under various operating conditions (180-250 °C and 0-6 h), with analyses on the solid and liquid products. Results show the peculiar behavior of these substrates under HTC. At 190-210 °C, the materials almost completely dissolve into the liquid phase forming 5hydroxymethylfurfural and organic acids. Above 220 °C, intermediates repolymerize into carbon-rich microspheres (secondary char), achieving solid yields up to 23 %, while itaconic and citric acid form. A comparison with pure substrates and additives demonstrates that the amounts of acetyl groups and derivatives of the plasticizers are crucial in catalyzing HTC reactions, creating a unique environment capable of leading to a total rearrangement of cellulose acetates. HTC can thus represent a cornerstone in establishing a biorefinery for residual cellulose acetate.
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X-ray free-electron lasers (FELs) are state-of-the-art scientific tools capable to study matter on the scale of atomic processes. Since the initial operation of X-ray FELs more than a decade ago, several facilities with upgraded performance have been put in operation. Here we present the first lasing results of Athos, the soft X-ray FEL beamline of SwissFEL at the Paul Scherrer Institute in Switzerland. Athos features an undulator layout based on short APPLE-X modules providing full polarisation control, interleaved with small magnetic chicanes. This versatile configuration allows for many operational modes, giving control over many FEL properties. We show, for example, a 35% reduction of the required undulator length to achieve FEL saturation with respect to standard undulator configurations. We also demonstrate the generation of more powerful pulses than the ones obtained in typical undulators. Athos represents a fundamental step forward in the design of FEL facilities, creating opportunities in FEL-based sciences.
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X-Treme is a soft X-ray beamline recently built in the Swiss Light Source at the Paul Scherrer Institut in collaboration with École Polytechnique Fédérale de Lausanne. The beamline is dedicated to polarization-dependent X-ray absorption spectroscopy at high magnetic fields and low temperature. The source is an elliptically polarizing undulator. The end-station has a superconducting 7â T-2â T vector magnet, with sample temperature down to 2â K and is equipped with an in situ sample preparation system for surface science. The beamline commissioning measurements, which show a resolving power of 8000 and a maximum flux at the sample of 4.7 × 10(12)â photonsâ s(-1), are presented. Scientific examples showing X-ray magnetic circular and X-ray magnetic linear dichroism measurements are also presented.
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We present the case of a 60-year-old man with a history of severe tophaceous gout with polyarticular involvement who came to the emergency room due to direct trauma to the right forearm and knee. The knee X-ray and CT scan showed a lateral tibial plateau fracture characterized by the presence of a lytic bone lesion. The presence of a solid neoplasm was ruled out and a CT-guided biopsy was performed. Histological evaluation revealed findings typical for an advanced intraosseous gout. As there was no significant risk of progression of the lytic lesion, the fracture site was treated conservatively. This case is unique in the literature in terms of location and should be considered as an atypical site of intraosseous gout. Proper differentiation of a pathological fracture on an intraosseous gout location from a neoplastic lesion is essential to choose the correct therapy.
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BACKGROUND AND AIM: The purpose of the study was to compare the data obtained by two independent observers and statistically analyze the results using Cohen's K to highlight the concordance or discordance in the diagnosis of normality, pathology and, in particular, the type of femoro-acetabular impingement (FAI) on plain films. METHODS: the study was conducted retrospectively. The only inclusion criterium was the minimum age of 20 years. All patients underwent a radiographic examination of the pelvis in standard anteroposterior projection in orthostasis. RESULTS: A good concordance between the two operators in the examination of normal hip joint (k= 0.68 right/ 0,74 left) was found; a similar grade of agreement was found for the analysis of "pincer" type FAI (k = 0.73 right, 0,67 left). The best results in concordance were achieved in the examination of "cam" type FAI (k= 0.82 right, 0,88 left), "mixed" type FAI (k = 0.85 right, 0,86 left), and in findings of "coxa profunda" (k = 0.92 right, 0,88 left). CONCLUSION: We found a good concordance between the two readers; a few cases of disagreement were found in the diagnosis of "pincer" type FAI and absence of disease. This discrepancy may be due to the different weight given by the single observer to the clinical indication that leads the patient to examination, but also by the difficulty of a not dedicated radiologist to show some subtle signs indicative of early FAI.