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Two-dimensional frequency-swept pulse with resilience to both B1 and B0 inhomogeneity
摘要： Applications of multidimensional spatially-selective pulses are sometimes limited by their long pulse durations resulting from the need to execute a modulated gradient waveform in concert with RF transmission. Here, we introduce a method to design two-dimensional selective adiabatic pulses using a Cartesian k-space trajectory. The full pulse can be sampled using various undersampled segments to create a multidimensional pulse resilient to large off-resonances. Moreover, the pulse can be designed to be resilient to B1 inhomogeneity. Experimental demonstrations of fully segmented and single-shot k-space sampling patterns are presented.
关键词： MRI,B1 inhomogeneity,B0 inhomogeneity,Adiabatic pulse,Frequency-modulated,Radiofrequency pulse,2D pulse
更新于2025-09-23 15:23:52
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Reducing radiation exposure in an electrophysiology lab with introduction of newer fluoroscopic technology
摘要： The use of fluoroscopic devices exposes patients and operators to harmful effects of ionizing radiation in an electrophysiology (EP) lab. We sought to know if the newer fluoroscopic technology (Allura Clarity) installed in a hybrid EP helps to reduce prescribed radiation dose. We performed radiation dose analysis of 90 patients who underwent various procedures in the EP lab at a community teaching hospital after the introduction of newer fluoroscopic technology in June of 2016. Watchman device insertion, radiofrequency ablation procedures, pacemaker permanent (PPM)/implantable cardioverter defibrillator (ICD) placement and battery changes were included in the study to compare radiation exposure during different procedures performed commonly in an EP lab. In all cases of watchman device placement, radiofrequency ablation procedures, PPM/ICD placement and battery changes, there was a statistically significant difference (<0.05) in radiation dose exposure. Significant reduction in radiation exposure during various procedures performed in an EP lab was achieved with aid of newer fluoroscopic technology and better image detection technology.
关键词： watchman device,permanent pacemaker,Radiation exposure,insertable cardioverter defibrillator,electrophysiology lab,newer fluoroscopic system,radiofrequency ablation
更新于2025-09-23 15:22:29
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First demonstration of a cryocooler conduction cooled superconducting radiofrequency cavity operating at practical cw accelerating gradients
摘要： We demonstrate practical accelerating gradients on a superconducting radiofrequency (SRF) accelerator cavity with cryocooler conduction cooling, a cooling technique that does not involve the complexities of the conventional liquid helium bath. A design is first presented that enables conduction cooling an elliptical-cell SRF cavity. Implementing this design, a single cell 650 MHz Nb3Sn cavity coupled using high purity aluminum thermal links to a 4 K pulse tube cryocooler generated accelerating gradients up to 6.6 MV/m at 100% duty cycle. The experiments were carried out with the cavity-cryocooler assembly in a simple vacuum vessel, completely free of circulating liquid cryogens. We anticipate that this cryocooling technique will make the SRF technology accessible to interested accelerator researchers who lack access to full-stack helium cryogenic systems. Furthermore, the technique can lead to SRF based compact sources of high average power electron beams for environmental protection and industrial applications. A concept of such an SRF compact accelerator is presented.
关键词： superconducting radiofrequency (SRF) cavity,cryocooler conduction cooling,electron beams,accelerating gradients,Nb3Sn
更新于2025-09-23 15:21:01
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Storage of RF photons in minimal conditions
摘要： We investigate the minimal conditions to store coherently a RF pulse in a material medium. We choose a commercial quartz as a memory support because it is a widely available component with a high Q-factor. Pulse storage is obtained by varying dynamically the light–matter coupling with an analog switch. This parametric driving of the quartz dynamics can be alternatively interpreted as a stopped-light experiment. We obtain an ef?ciency of 26%, a storage time of 209 μs and a time-to-bandwidth product of 98 by optimizing the pulse temporal shape. The coherent character of the storage is demonstrated. Our goal is to connect different types of memories in the RF and optical domain for quantum information processing. Our motivation is essentially fundamental.
关键词： quantum memory,quartz resonator,radiofrequency photons
更新于2025-09-23 15:21:01
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Prediction of Local Tumor Progression after Radiofrequency Ablation (RFA) of Hepatocellular Carcinoma by Assessment of Ablative Margin Using Pre-RFA MRI and Post-RFA CT Registration
摘要： To evaluate the clinical impact of using registration software for ablative margin assessment on pre-radiofrequency ablation (RFA) magnetic resonance imaging (MRI) and post-RFA computed tomography (CT) compared with the conventional side-by-side MR-CT visual comparison. Materials and Methods: In this Institutional Review Board-approved prospective study, 68 patients with 88 hepatocellulcar carcinomas (HCCs) who had undergone pre-RFA MRI were enrolled. Informed consent was obtained from all patients. Pre-RFA MRI and post-RFA CT images were analyzed to evaluate the presence of a sufficient safety margin (≥ 3 mm) in two separate sessions using either side-by-side visual comparison or non-rigid registration software. Patients with an insufficient ablative margin on either one or both methods underwent additional treatment depending on the technical feasibility and patient’s condition. Then, ablative margins were re-assessed using both methods. Local tumor progression (LTP) rates were compared between the sufficient and insufficient margin groups in each method. Results: The two methods showed 14.8% (13/88) discordance in estimating sufficient ablative margins. On registration software-assisted inspection, patients with insufficient ablative margins showed a significantly higher 5-year LTP rate than those with sufficient ablative margins (66.7% vs. 27.0%, p = 0.004). However, classification by visual inspection alone did not reveal a significant difference in 5-year LTP between the two groups (28.6% vs. 30.5%, p = 0.79). Conclusion: Registration software provided better ablative margin assessment than did visual inspection in patients with HCCs who had undergone pre-RFA MRI and post-RFA CT for prediction of LTP after RFA and may provide more precise risk stratification of those who are treated with RFA.
关键词： Fusion,Margin,Magnetic resonance imaging,Local tumor progression,Radiofrequency ablation
更新于2025-09-23 15:21:01
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Polymers and Electromagnetic Radiation || Front Matter
摘要： This book concentrates on the interaction of electromagnetic waves with polymers and deals only exceptionally with particle radiation. Electromagnetic waves comprise a very broad range of frequencies that extends over more than 20 orders of magnitude from the radiofrequency region up to the region of hard c-rays emitted from radionuclides or being part of the cosmic rays.
关键词： microwave,radiofrequency,visible light,infrared radiation,gamma rays,polymers,electromagnetic waves,interaction,X-rays,ultraviolet light
更新于2025-09-23 15:21:01
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Laser Ablation versus Radiofrequency Ablation for benign non-functioning thyroid nodules: Six-month results of a randomised, parallel, open-label, trial (LARA trial)
摘要： Background: No direct prospective studies comparing laser ablation (LA) and radiofrequency ablation (RFA) for debulking benign non‐functioning thyroid nodules (BNTNs) exist. We aimed to compare the efficacy and safety of both techniques in patients with solid or predominantly solid BNTN. Methods. This six‐month, single‐use, randomized open label parallel trial compared the following primary endpoints between the RFA and LA groups six months after treatment: (1) nodule volume reduction expressed as a percentage of nodule volume at baseline; (2) proportion of nodules with more than 50 % reduction (successful rate). We enrolled subjects with a solitary BNTN or dominant nodule characterized by pressure symptoms/cosmetic problems or patients without symptoms who experienced a volume increase >20% in one year. Nodules underwent core needle biopsy (CNB) for diagnosis. Patients were randomly assigned (1:1) to receive LA or RFA. Safety was assessed in all randomly assigned participants. Results: Sixty patients were randomly assigned to receive either RFA or LA (1:1) between January 2016 and November 2018. Both groups were similar in basal nodule volume, thyroid function, histology, symptoms/cosmetic score, and procedure time. At six months, the nodule volume reduction was 64.3% (95% confidence interval 57.5 ‐ 71.2%) in the RFA group and 53.2% (47.2 – 95.2%; p = 0.02) in the LA group. This effect was also confirmed in the linear regression model adjusted for age, baseline volume, and proportion of cellular component (LA vs RFA percent change Delta= ‐12?8, p=0?02). No significant difference was observed in success rate 6‐month after treatment (RFA vs LA: 86?7% vs 66?7%, p=0?13) or in thyrotropin level between the groups. Although improved, no significant difference was observed between RFA and LA for compressive symptoms (RFA: 2.13 vs 3.9, p<0?001; LA: 2.4 vs 3.87, p<0?001) and cosmetic score (RFA: 1?65 vs 2?2, p<0?001; LA: 1?85 vs 2?2, p<0?001). The adverse event rates (local pain, dysphonia, thyrotoxicosis, fever, hematoma) were 37% (n=11) and 43% (n=13) for RFA and LA, respectively, with no requirement for hospitalization. Conclusion: While the success rate was similar in the RFA and LA groups, RFA achieved a significantly larger nodule volume reduction at six months.
关键词： Radiofrequency ablation,Laser ablation,Benign non‐functioning thyroid nodules,Thyroid nodules,Volume reduction
更新于2025-09-23 15:19:57
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Bio-Based Polycationic Polyurethane as an Ion-Selective Membrane for Nitrate Tapered Optical Fiber Sensors
摘要： There has been long-standing controversy, both among scientists and in the public, about whether children absorb more radio frequency (RF) energy in their heads than adults when using a mobile telephone. This review summarizes the current understanding of this issue, and some of the complexities in comparing the absorption of RF energy in different individuals from use of mobile phones. The discussion is limited to dosimetric issues, i.e., possible age-related differences in absorption of RF energy in the heads of mobile phone users. For most metrics of exposure, in particular those relevant to assessing the compliance of handsets with regulatory limits, there is no clear evidence for age-related differences in exposure. For two metrics of exposure, there is a clear evidence that age can play a factor: 1) the local specific absorption rate (SAR), in particular anatomically defined locations within the brain, will vary with head size and hence with age and 2) the SAR, in particular tissues, (e.g., bone marrow in the skull) can vary with age due to age-related differences in the dielectric properties of tissue. However, these differences involve SAR levels that are below the 1-g or 10-g peak spatial SAR (psSAR averaged over 1 or 10 g of tissue) and have no significance for compliance assessment. Age-related differences observed in worst case simulations such as presently considered are difficult to generalize to human populations under real-world exposure conditions due to many variables that determine SAR during realistic usages.
关键词： radiofrequency,specific absorption rate,exposure,children,Mobile phone
更新于2025-09-23 15:19:57
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Clinical efficacy comparison of low-temperature plasma radiofrequency ablation and Nd:YAG laser in treating recurrent acquired nasolacrimal duct obstruction
摘要： To evaluate the effectiveness and safety of low-temperature plasma radiofrequency ablation (coblation) and Nd:YAG laser in treating recurrent nasolacrimal duct obstruction. A prospective study was performed on patients who agreed to be treated with coblation or Nd:YAG laser for recurrent nasolacrimal duct obstruction after failed lacrimal Nd:YAG laser combined with silicone intubation. The visual analogue scale (VAS) pain grade was assessed at baseline, immediately, and 3 and 7 days after surgery. The degree of watering, lacrimal passage irrigation, and complications were also evaluated 1 week and 1, 3, and 6 months after surgery. Ninety-five patients who met the criteria for recurrent nasolacrimal duct obstruction from February 2018 to February 2019 were included in this study, with 46 patients receiving coblation and 49 patients Nd:YAG laser. The intraoperative and postoperative (3 days after surgery) VAS pain grades of the patients who received coblation were significantly lower than those who received Nd:YAG laser (P < 0.001). The number of patients in the coblation group who achieved complete clinical relief (no epiphora symptoms with fluent lacrimal passage irrigation) was significantly larger than that in the lacrimal Nd:YAG laser group at 1, 3, and 6 months after surgery (P = 0.033, P = 0.006, P = 0.003, respectively). During the follow-up period, there were no unexpected complications in either group. Compared with Nd:YAG laser, coblation performed well in alleviating pain and maintaining sustained disease relief and may therefore be an alternative to conventional laser or dacryocystorhinostomy surgery in the management of recurrent nasolacrimal duct obstruction.
关键词： Nd:YAG laser,Recurrent acquired nasolacrimal duct obstruction,Low-temperature plasma radiofrequency ablation,VAS pain grade
更新于2025-09-23 15:19:57
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Microneedle fractional radiofrequency-induced micropores evaluated by in vivo reflectance confocal microscopy, optical coherence tomography, and histology
摘要： Background: Microneedle fractional radiofrequency (MNRF) is a minimally invasive technique that delivers radiofrequency (RF) energy into the skin via microneedles. Reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) enable the characterization of device-tissue interactions in in vivo skin. The aim of this study is to describe MNRF-induced micropores using RCM and OCT imaging. Materials and methods: Five healthy participants were treated with a 7 × 7 array of 1500 μm microneedles on two adjacent areas of the right hip. One area received MNRF using high RF energy while the other underwent MNRF at low RF energy. Micropore morphology was evaluated qualitatively and quantitatively with RCM and OCT. To relate imaging with histology, one participant underwent punch biopsy in both areas. Results: Reflectance confocal microscopy visualized shape, content, and thermal-induced coagulation zone (CZ) of MNRF micropores. At high RF energy, micropores showed concentric shape, contained hyperreflective granules, and coagulated tissue from epidermis to dermo-epidermal junction (diameter 63-85 μm). Micropores at low RF energy, presented with a stellate shape, no content and CZs that were visible only in epidermis (CZ thickness 9 μm, IQR 8-21 μm). Evaluating OCT, high RF energy showed deeper (150 μm), more easily identifiable micropores compared to low RF energy micropores (70 μm). Histology showed tissue coagulation to a depth of 1500 μm at high RF energy, while at low RF energy, disruption was only visible in epidermis. Conclusion: Microneedle fractional radiofrequency micropores show distinct characteristics in both RCM and OCT, depending on RF energy. These in vivo imaging modalities are complementary and allow combined, qualitative, and quantitative evaluation.
关键词： microneedle fractional radiofrequency,histology,optical coherence tomography,micropore,reflectance confocal microscopy
更新于2025-09-19 17:15:36