Fast design of local N-gram-specific absorption rate-optimized radiofrequency pulses for parallel transmit systems

Designing multidimensional radiofrequency pulses for clinical application must take into account the local specific absorption rate (SAR) as controlling the global SAR does not guarantee suppression of hot spots. The maximum peak SAR, averaged over an N grams cube (local NgSAR), must be kept under certain safety limits. Computing the SAR over a three-dimensional domain can require several minutes and implementing this computation in a radiofrequency pulse design algorithm could slow down prohibitively the numerical process. In this article, a fast optimization algorithm is designed acting on a limited number of control points, which are strategically selected locations from the entire domain. The selection is performed by comparing the largest eigenvalues and the corresponding eigenvectors of the matrices which locally describe the tissue's amount of heating. The computation complexity is dramatically reduced. An additional critical step to accelerate the computations is to apply a multi shift conjugate gradient algorithm. Two transmit array setups are studied: a two channel 3 T birdcage body coil and a 12-channel 7 T transverse electromagnetic (TEM) head coil. In comparison with minimum power radiofrequency pulses, it is shown that a reduction of 36.5% and 35%, respectively, in the local NgSAR can be achieved within short, clinically feasible, computation times.     

PRACTICAL MANAGEMENT OF PRIMARY VARICOSE VEINS

SUMMARY Varicose veins cause a great deal of morbidity in our population today. Despite the large amount of surgical time spent dealing with the problem, there is still a disappointingly high recurrence rate and many patients are investigated inadequately before surgery. This review considers the assessment of ‘simple’ varicose veins using a combination of tourniquet tests and a hand-held doppler probe. The place of more sophisticated investigative techniques is also discussed, in particular the value of duplex assessment in localising the variably sited sapheno-popliteal junction. Routine stripping of the long saphenous vein to the below-knee level is likely to decrease the recurrence rate of simple, long, saphenous varicose veins.     

异搏停心脏停跳液的延迟复跳现象临床分析与处理

系统观察使用异搏停停跳液的34例体外循环病例,6例(17.6％)在10～38分钟复跳。延迟复跳组和非延迟复跳组间不存在血钙等特异性因素的影响,而受年龄、心脏缺血时间和心脏张力的影响。延迟复跳心脏的功能良好,超微结构保护良好。作者对异搏停液的使用指征和延迟复跳的处理提出了建议。     

Spinal and supraspinal mechanisms affecting torque development at different joint angles

Introduction: We examined the neural mechanisms responsible for plantar flexion torque changes at different joint positions. Methods: Nine subjects performed maximal voluntary contractions (MVC) at 6 ankle–knee angle combinations [3 ankle angles (dorsiflexion, anatomic position, plantar flexion) and 2 knee angles (flexion, full extension)]. Neural mechanisms were determined by V‐wave, H‐reflex (at rest and during MVC), and electromyography during MVC (RMS), normalized to the muscle compound action potential (V/M_sup, H_max/M_max, H_sup/M_sup and RMS/M_sup) and voluntary activation (VA), while muscle function was assessed by doublet amplitude. Results: MVC and doublet amplitude were significantly lower at plantar flexion (P < 0.01), while VA was significantly lower at dorsiflexion and full knee extension (P < 0.05). V/M_sup and RMS/M_sup were significantly lower at knee extension (P < 0.01), while H_sup/M_sup was not affected by joint angle. Conclusions: These results indicate that joint positions leading to muscle lengthening produce reduced neural drive, due mainly to supraspinal mechanisms. Muscle Nerve 53 : 626–632, 2016     

黄嘌呤氧化酶对血管内皮功能障碍的影响

目的考察黄嘌呤氧化酶(xanthine oxidase)在自发性高血压大鼠(SHR)血管舒缩及内皮功能障碍中的作用。方法采用尾套法测定SHR和正常大鼠(WKY)血压;Greiss反应测定血清一氧化氮分泌量;FRAP(ferric reduction abilitypower)法测定主动脉蛋白总抗氧化能力;RT-PCR法考察黄嘌呤氧化酶及内皮型一氧化氮合酶(eNOS)mRNA表达情况;血管环舒缩测定来评价黄嘌呤氧化酶抑制剂别嘌呤醇(oxypurinol,Oxy)对大鼠腹主动脉内皮依赖性舒张反应的影响。结果SHR血压(191.1±5.6)显著高于WKY大鼠(140.4±5.9)mmHg;SHR血清NO分泌量(28.4±5.4)、主动脉蛋白总抗氧化能力(1.02±0.14)U/μg蛋白和腹主动脉内皮依赖性舒张反应(66.2±4.6)%均显著低于WKY[分别为(51.6±5.8),(2.8±0.3)U/μgpro和81.0%±2.7%);而心、肾及主动脉中黄嘌呤氧化酶表达均显著高于WKY大鼠(P<0.05)。黄嘌呤氧化酶抑制剂Oxy能明显降低黄嘌呤氧化酶mRNA表达(降低31.6%),且改善腹主动脉内皮依赖型舒张反应(提高20.2%),但对eNOS表达则无显著影响。结论结果提示SHR中存在内皮功能障碍和氧化应激状态,黄嘌呤氧化酶参与了SHR内皮功能障碍。     

Analysis of hesitancy and motivational factors for COVID-19 vaccination among patients presenting to eye care hospitals – A multicenter questionnaire-based survey

Purpose:To analyze the hesitancy and motivational factors related to coronavirus disease 2019 (COVID-19) vaccination among patients visiting for eye care.Methods:A telephonic survey was conducted using validated questionnaires consisting of 36 questions in five sections from July 1 to July 31, 2021. Patients visiting six tertiary centers and one secondary center of our eye hospitals were interviewed over their phones, and their responses were entered onto the Google forms. The responses were recorded as demographics, health status, awareness about vaccination, factors contributing to hesitancy or acceptance to vaccinate, and general perception about the vaccine.Results:A total of 5033 patients were surveyed. The mean age was 49.0 ± 14.2 years. A total of 563 (11.2%) patients gave a history of symptoms or were tested positive for COVID-19; 2225 (44.2%) patients were already COVID-19 vaccinated. Around 2883 (56%) patients were aware of getting infection despite vaccination, and 4092 (81.3%) perceived vaccination should be compulsory. The main reason for vaccination hesitancy was the fear of side effects (n = 487, 17.3%). The fear of getting infected was the most common reason for vaccination (n = 911, 40.9%). Factors associated with a lower proportion of vaccinated individuals included younger age (P < 0.001), female gender (P < 0.001), lower education (P < 0.001), lower income (P < 0.001), and rural residence (P = 0.33).Conclusion:Creating awareness about the minor side effects and reassurance can allay an individual’s fears. The fear associated with the rapid spread of infection and associated mortality needs to be utilized to increase vaccination acceptance. A targeted approach toward groups with poor uptake of vaccination is necessary.