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Abstract Background Chondroblastomas are rare, benign, locally aggressive lesions that appear in the epiphysis. Surgery for femoral head chondroblastoma (FHCB) is difficult. Conventional treatment with curettage via a drilled tunnel along the femoral neck can damage the growth plate and is associated with high local recurrence rates. The trapdoor procedure, which directly facilitates lesion access from the femoral head articular surface, can reduce local recurrence and avoid growth plate damage, although it requires surgical dislocation. Little is known about the long-term results of this direct articular surface approach, and there are no case reports on trapdoor procedures without dislocation. Case presentation We report two cases (patients aged 12 and 15 years) of FHCB presented with coxalgia treated using the trapdoor procedure without surgical dislocation. Both surgeries were performed with patients in the semi-lateral position. The hip joint was exposed via an anterior approach, and a capsulotomy was performed at the superior rim of the acetabulum, followed by the external rotation of the hip joint. With a fine osteotome, a rectangular flap (trapdoor) was opened on the cartilage surface in the lateral non-weight-bearing area, and curettage of the lesion followed by bone and/or bone substitute grafting was performed. Subsequently, the trapdoor was replaced in its original position. There has been no local recurrence or femoral head aseptic necrosis after more than 6 and 12 years for patients 1 and 2, respectively. Both patients had musculoskeletal tumor society scores of 100% at follow-up and are enjoying a normal active life. Conclusions This direct femoral head approach without dislocation may be a simple treatment alternative for FHCB.

The compact energy recovery linac (cERL) has been developed for industrial applications since 2017. Applications such as free electron laser require a compressed beam with a small energy spread and transverse emittance. The typical operation energy of cERL is an intermediate energy region close to 17.5 MeV; therefore, the electron bunch is easily affected by the longitudinal space-charge effects and the coherent synchrotron radiation wakefield effects. Bunch compression is demonstrated by optimizing a combination of a longitudinally chirped electron bunch and the arcs with nonzero R_{56} parameters. When the bunch compression procedure is applied for a bunch charge of 60 pC, an increase in energy spread is observed at the short bunch length. We systematically explored the chirp phase to determine the best condition. The measurement results of the energy spread, bunch length, and transverse emittance were compared with the tracking simulation results to understand the compressed beam dynamics.

Introduction: Radial artery occlusion after puncture is a serious complication of radial artery access for endovascular therapy (EVT). Herein, we show the feasibility of ultrasound-guided trans-occluded radial access (TORA) for EVT after radial artery occlusion. Case: We describe the technique performed under ultrasound guidance for EVT for right external iliac artery stenosis in a 73-year-old man with intermittent claudication. Conclusion: TORA provides a safe and feasible alternative access after radial artery occlusion.

BackgroundThe influence of polyvascular disease (PVD) on the short- and long-term clinical outcomes of patients undergoing transcatheter aortic valve implantation via trans-femoral access (TF-TAVI) has not been fully elucidated.MethodsA total of 2167 patients from the Optimized CathEter vAlvular iNtervention-TAVI (OCEAN-TAVI) registry who underwent TF-TAVI was studied. PVD was defined as the presence of at least two of the following vascular bed (VB) diseases: concomitant coronary artery disease (CAD), cerebrovascular disease (CVD), and peripheral artery disease (PAD).ResultsPatients with PVD (288 patients, 13.3%) had a higher incidence of in-hospital complications, such as AKI (16.3% vs. 7.0%, pConclusionsThe increased prevalence of concomitant atherosclerotic VB diseases before TF-TAVI may increase the rates of in-hospital complications and 2-year cardiovascular death. Given the higher rate of mortality in patients with PVD undergoing TF-TAVI, future studies focusing on medical therapy are needed to reduce long-term cardiovascular events in this high-risk subset.

A disturbance observer (DOB)-based control approach was verified using the low-level radio-frequency systems of superconducting (SC) cavities operated in a continuous wave (CW) mode in a compact energy recovery linac (cERL) at KEK. This approach compensates for both predictable and unpredictable disturbances in a radio frequency (rf) system such as beam loading, Lorentz force detuning, and microphonics. This paper generalizes the DOB method in pulsed SC rf systems in the cERL at KEK. The results show that the pulse-to-pulse stabilities of the rf system are improved as expected by using this control approach. Furthermore, this method is validated by successfully compensating long pulse beam-loading effects in cERL.

Operational experience of a 500 kV photoemission gun at the compact energy recovery linac (cERL) of the High Energy Accelerator Research Organization is presented. The gun, developed at the Japan Atomic Energy Agency, was found to have failures in two out of the ten-segment ceramic insulator just after installation at cERL. The gun had been operated at 390 kV with eight segments until April 2015 and provided a 0.9 mA beam. An additional two-segment insulator was installed on the top of the existing insulators to recover the high-voltage performance. The gun was then conditioned up to 539 kV and has been operated stably at 500 kV. No discharge caused by the gun itself was observed at 500 kV once the high threshold voltage for stable operation exceeded 500 kV. A dark current of a few picoamperes was generated at 500 kV from a photocathode puck with a semiconducting wafer, while no dark current was observed without a semiconducting wafer. Stable generation of a 500 keV beam with current greater than 0.8 mA was demonstrated for more than two hours.

BackgroundPeri‐stent contrast staining (PSS) after metallic drug‐eluting stent deployment is associated with target lesion revascularization and very late stent thrombosis. However, the type of PSS that influences the clinical outcomes is unknown. Therefore, we aimed to reveal which PSS type was influencing clinical outcomes. Methods and ResultsThis study included 5580 de novo lesions of 4405 patients who were implanted with a first‐ or second‐generation drug‐eluting stent and who were evaluated using follow‐up angiography within 12 months after stent implantation. We compared the clinical outcomes of patients divided into focal PSS and segmental PSS groups for 6 years after stent implantation. Total PSS was observed in 97 lesions (2.2%), of which 42 and 55 lesions were focal and segmental PSS, respectively. Baseline characteristics were similar between groups, except for intraoperative chronic total occlusion (segmental PSS=47.3% versus focal PSS=11.9%, P=0.0001). The incidence of segmental PSS tended to be higher in patients with a first‐generation drug‐eluting stent (83.6% versus 16.4%, P=0.05). The cumulative incidence of stent thrombosis in the 6 years of segmental PSS group was significantly higher than that of the focal PSS group (13.9% versus 0%, P=0.04). The cumulative incidence of overall target lesion revascularization for restenosis, excluding target lesion revascularization procedures for stent thrombosis, was significantly higher in the segmental PSS group (38.0% versus 0%, P=0.01). ConclusionsThe incidence of segmental PSS tended to be higher in patients with a first‐generation drug‐eluting stent and appeared to be significantly associated with target lesion revascularization and stent thrombosis.

We demonstrated the generation of a 500-keV electron beam from a high dc voltage photoemission gun for an energy recovery linac light source [N. Nishimori et al., Appl. Phys. Lett. 102, 234103 (2013)]. This demonstration was achieved by addressing two discharge problems that lead to vacuum breakdown in the dc gun. One is field emission generated from a central stem electrode. We employed a segmented insulator to protect the ceramic insulator surface from the field emission. The other is microdischarge at an anode electrode or a vacuum chamber, which is triggered by microparticle transfer or field emission from a cathode electrode. An experimental investigation revealed that a larger acceleration gap, optimized mainly to reduce the surface electric field of the anode electrode, suppresses the microdischarge events that accompany gas desorption. It was also found that nonevaporable getter pumps placed around the acceleration gap greatly help to suppress those microdischarge events. The applied voltage as a function of the total gas desorption is shown to be a good measure for finding the optimum dc gun configuration.

We have developed a high-resolution cavity-beam position monitor (BPM) to be used at the focal point of the ATF2, which is a test beam line that is now being built to demonstrate stable orbit control at ∼nanometer resolution. The design of the cavity structure was optimized for the Accelerator Test Facility (ATF) beam in various ways. For example, the cavity has a rectangular shape in order to isolate two dipole modes in orthogonal directions, and a relatively thin gap that is less sensitive to trajectory inclination. A two stage homodyne mixer with highly sensitive electronics and phase-sensitive detection was also developed. Two BPM blocks, each containing two cavity BPMs, were installed in the existing ATF beam line using a rigid support frame. After testing the basic characteristics, we measured the resolution using three BPMs. The system demonstrated 8.7 nm position resolution over a dynamic range of 5 μm.

We present the measurement results of electron beam emittance in the Accelerator Test Facility damping ring operated in multibunch modes. The measurements were carried out with an upgraded laser wire beam profile monitor. The monitor has now a vertical wire as well as a horizontal one and is able to make much faster measurements thanks to an increased effective laser power inside the cavity. The measured emittance shows no large bunch-to-bunch dependence in either the horizontal or vertical directions. The values of the vertical emittance are similar to those obtained in the single-bunch operation. The present results are an important step toward the realization of a high-energy linear collider.

GaAs/GaAsP strain-compensated superlattices (SLs) were developed for spin-polarized photocathode applications. High crystal quality was maintained with SL thicknesses up to 720 nm (90-pairs); however, the quantum efficiency (QE) did not increase linearly with the SL thickness but became saturated starting from an SL thickness of 192 nm (24-pairs). Time-resolved photoluminescence measurements revealed that the carrier lifetime in the GaAs/GaAsP strain-compensated SL was as short as 20.5 ps at room temperature, which causes the elimination of photoexcited electrons before emission. A simulation based on a diffusion model was implemented to quantitatively evaluate the effect of the carrier lifetime on the QE. The simulation results were in good agreement with the experimental results and demonstrate that a carrier lifetime of over 120 ps is required for a two-fold improvement of the QE. [ABSTRACT FROM AUTHOR]

GaInP, which has a wider band gap than GaAs, is introduced as a photocathode for energy recovery linac (ERL). The wide band gap of material is expected to reduce the heating effect in the thermal relaxation process after high energy excitation. GaInP photocathodes exhibited higher quantum efficiency than GaAs and low thermal emittance as the same as GaAs photocathodes under green laser light irradiation. A short picosecond electron pulse was also achieved with the GaInP photocathode under 532 nm pulse laser irradiation. These experimental results demonstrate that the GaInP photocathode is an important candidate for ERL. [ABSTRACT FROM AUTHOR]

Background: Certain patients with critical limb ischemia (CLI) experience significant decline in activities of daily living (ADL) during hospitalization. The prognosis of decline in ADL during hospitalization remains unknown. Methods: A retrospective analysis was performed on collected data of patients with CLI treated by endovascular treatment between April 2007 and December 2015. We evaluated CLI in patients ADL at the time of hospitalization and after discharge using the Barthel index. We classified all patients into patients with decline in ADL and stable in ADL and compared clinical outcomes (cumulative incidence of wound healing, amputation-free survival at 1 year) between the 2 groups. Results: Two hundred and fifty-five consecutive patients with CLI (221 limbs), who underwent successful endovascular intervention, were enrolled in this study. Of all patients, 22 patients were classified into the decline group. The prevalence of wound, Ischemia, foot infection (WIfI) classification high grade was higher in the decline group (30.7% vs 63.6%; P < .01). The wound healing rates were worse in the decline group than in the stable group (40% vs 78% at 1 year; P < .01). The same trends were observed in the amputation-free survival (37% vs 78%; P < .01). After multivariate analysis, decline in ADL was an independent predictor of wound healing and amputation-free survival (odds ratio [OR]: 2.85, 95% confidence interval [CI]: 1.61-3.35, P < .01; OR: 2.46, 95% CI: 1.26-4.53, P = .01). Conclusions: Patients with CLI with decline in ADL during hospitalization were found to have a poor prognosis suggesting that a decline in ADL may affect the clinical outcomes. [ABSTRACT FROM AUTHOR]

With a low emittance and short-bunch electron beam at a high repetition rate realized by a superconducting linac, stimulated excitation of an optical cavity at the terahertz spectrum range is shown. The electron beam passes through small holes in the cavity mirrors without being destroyed. A sharp resonance structure which indicates wideband stimulated emission via coherent diffraction radiation is observed while scanning the round-trip length of the cavity. [ABSTRACT FROM AUTHOR]