A more accurate tuning‐matching technique for NMR probes using wobulation and variable phase shifter

For optimizing sensitivity and RF excitation, high resolution NMR probes have to be tuned at the Larmor frequency and matched to 50 Ω‐transmission lines to which they are connected. For achieving this setting, one usually resorts to the wobulation function which consists in sweeping the frequency of the power source while monitoring and minimizing the reflected power taken from a directional coupler through adjusting the tuning and matching capacitors. However, the presence of a transmission‐reception switch between the directional coupler and the probe leads to the appearance of extra loss and reactance, and affects the determined values of the previous mentioned capacitors. Even if this situation is usually satisfactory, the true tuning‐matching condition is required for optimal NMR sensitivity and for reliable spectra analyses when nonlinear effects are present (radiation damping, spin‐noise experiments, etc.). To circumvent the need of network analyzer directly attached to the probe for finding this optimal tuning‐matching condition, in the current work, we report a procedure which combines wobulation and choice of a transmission‐line phase shift obtained by a variable phase shifter inserted between the probe and the switch. The technique was successfully validated with help of a network analyzer. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 59–68, 2015     

Prospects for radiofrequency hyperthermia applicator research. I – Pre-optimised prototypes of endocavitary applicators with matching interfaces for prostate hyperplasia and cancer treatments

Inconsistency is observed in comparing assessment data of applicators for endocavitary hyperthermia (EHT) with microwaves (MW) and radiofrequency (RF) obtained using the standard method of inserting bare applicators in phantom tissues. MW antennae exhibit overall average penetration depths of approximately 6?mm, excluding hot spots. RF radiators exhibit penetration depths of not more than approximately 3?mm, a value too low considering the superior penetration of the RF plane wave radiation. Assuming that a mismatch at the RF radiator–tissue interface is causing the poor energy transfer of RF energy, we developed new RF radiators with controlled dielectric matching interfaces for evaluating the potential of RF radiation in EHT and in interstitial hyperthermia (IHT) treatments. We designed, developed and assessed 27.12?MHz, 8?mm OD inductive and capacitive devices of novel and existing designs, each provided an optimised bi-layer matching interface. The assessment results reveal features such as customisable length and shape, independence of insertion depth, uncritical air gap, longitudinal heating uniformity, outstanding penetration depths (19–20?mm) and high SAR gradients at both radiator ends – i.e. prostatic urethra ends – for added safety. These data clear the way for the development of pre-optimised EHT inductive and capacitive RF applicators. Evidence of positive effects of high near-fields density in cavity microenvironments is given. Such devices show potential for more effective prostatic hyperplasia treatments and for improving the feasibility of more adequate treatment planning and thermal dosimetry of interstitial and transurethral hyperthermia treatments of prostate carcinoma.     

An embedded four‐channel receive‐only RF coil array for fMRI experiments of the somatosensory pathway in conscious awake marmosets

fMRI has established itself as the main research tool in neuroscience and brain cognitive research. The common marmoset (Callithrix jacchus) is a non‐human primate model of increasing interest in biomedical research. However, commercial MRI coils for marmosets are not generally available. The present work describes the design and construction of a four‐channel receive‐only surface RF coil array with excellent signal‐to‐noise ratio (SNR) specifically optimized for fMRI experiments in awake marmosets in response to somatosensory stimulation. The array was designed as part of a helmet‐based head restraint system used to prevent motion during the scans. High SNR was obtained by building the coil array using a thin and flexible substrate glued to the inner surface of the restraint helmet, so as to minimize the distance between the array elements and the somatosensory cortex. Decoupling between coil elements was achieved by partial geometrical overlapping and by connecting them to home‐built low‐input‐impedance preamplifiers. In vivo images show excellent coverage of the brain cortical surface with high sensitivity near the somatosensory cortex. Embedding the coil elements within the restraint helmet allowed fMRI data in response to somatosensory stimulation to be collected with high sensitivity and reproducibility in conscious, awake marmosets. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

抗环瓜氨酸肽抗体与类风湿因子诊断类风湿性关节炎Meta分析

目的 采用诊断试验Meta分析方法综合评价抗环瓜氨酸肽抗体（抗CCP）和类风湿因子（RF）筛查类风湿性关节炎（RA）的效果,得到各种筛查方法的综合灵敏度.方法 通过检索万方、维普、CNKI等数据库,获得同时有抗CCP和RA诊断筛查RA的文献23篇,直接或间接提取真阳性数（TP）、假阳性数（NP）、假阴性数（FN）、真阴性数数据（TN）;采用DPS 6.5进行诊断试验Meta分析,采用加权法、非加权法以及稳健法三种方法分别拟合两种筛查方法的受试者工作特征曲线（SROC曲线）,比较两种筛查方法诊断RA效果的差别.结果 稳健法结果较为稳定,其结果显示抗CCP筛查RA的综合准确度为0.831,诊断优势比为24.154;RF的综合准确度为0.765,诊断优势比为10.540;抗CCP筛查RA的诊断准确度明显高于RF（P〈0.01）.结论 抗CCP筛查诊断RA能获得较好的准确度,明显高于RF筛查诊断RA所获得的准确度;文献结果显示抗CCP能获得较好的特异度,而RF能获得较好的灵敏度,若能联合抗CCP和RF筛查结果,对RA具有较高的诊断价值.     

血清RF、抗CCP抗体和AFA抗体联合检测在早期诊断类风湿关节炎中的价值

目的探讨血清类风湿因子(rheumatoid factor,RF)、抗环瓜氨酸肽(cyclic citrullinated peptide,CCP)抗体和抗聚角蛋白微丝蛋白抗体(antifilaggrin antibody,AFA)联合检测对早期诊断类风湿关节炎(rheumatoid arthritis,RA)的临床价值。方法选取2016年1月～2018年1月我院风湿免疫科收治的75例RA患者设为研究组,另选取非RA患者105例设为对照组。以免疫散射比浊法测定血清RF水平,ELISA法检测抗CCP抗体和间接免疫荧光法测AFA抗体水平,回顾性统计分析三项指标与RA发病的相关性,血清RF、抗CCP抗体、AFA抗体单独检测与不同组合下联合检测诊断RA的价值。结果研究组三种指标联合检测检出率最高,为81.33%;单独检测AFA抗体检出率最低,为46.67%;研究组和对照组各项指标检出率比较,差异有统计学意义(P0.05);回归分析各指标系数均为正值,OR值均大于1(P0.05);单独检测中,灵敏度以RF最高(73.33%),特异性最高的是AFA抗体(98.10%),阳性预测值、阳性似然比以AFA抗体最高(94.59%,24.50),阴性预测值以RF、抗CCP最高(二者相近,分别为79.80%、79.03%),阴性似然比以RF最低(0.35);联合检测中,灵敏度、特异度、阳性预测值、阴性预测值以RF+抗CCP+AFA最高,阴性似然比以RF+抗CCP+AFA最低(0.19)。结论血清RF、抗CCP抗体、AFA抗体均是RA的正相关危险因素,血清RF+抗CCP+AFA抗体联合检测能显著提高单独指标阳性者RA诊断率,更好的估计RA患病率。     

3D打印技术制作车载式磁共振接收线圈的应用研究

目的:制作车载式核磁共振接收线圈,应用于突发灾害现场伤情相对复杂的人体部位外伤检诊,提供有效、简易线圈设备,快速定位诊断,正确判断伤情,满足车载式磁共振系统设备机动性强的基本要求。方法:应用3D打印技术中熔融沉积制造(fused deposition modeling,FDM)技术将聚乳酸(polylactic acid,PLA)加热熔化到半流体态,在计算机的控制下,根据所要轮廓信息,喷头将半流态材料挤压,凝固后形成轮廓状的薄层,最后进行固化,形成接收线圈。结果:利用3D打印技术制作完成符合人体主要部位需要的适合野外救援车载化条件(如头颈、肩、腰椎、膝关节等关键部位)的磁共振射频接收线圈,满足核磁医疗诊断需求。结论:3D打印技术可以满足车载式磁共振接收线圈的先期研发需求。     

Yttrium-90 Radioembolization Stops Progression of Targeted Breast Cancer Liver Metastases after Failed Chemotherapy

PurposeTo determine, in an open-label, retrospective report, the safety and effectiveness of locoregional therapy with yttrium-90 (⁹⁰Y) radioembolization for patients with progressing breast cancer liver metastases (BCLMs) despite multi-agent chemotherapy.Materials and MethodsSeventy-five patients with progressing BCLMs and stable extrahepatic disease were treated with radioembolization at a single institution. Retrospective review of a prospectively collected database was performed to evaluate clinical and biochemical toxicities, tumor response, overall survival (OS), and time to progression. Radiologic response assessments included Response Evaluation Criteria In Solid Tumors in primary index lesions and metabolic activity on positron emission tomography (PET). Univariate and multivariate analyses were performed.ResultsThe mortality rate at 30 days was 4% (n = 3). Clinical toxicity and hyperbilirubinemia of grade 3 or worse occurred in 7.6% (n = 5) and 5.9% of patients (n = 4), respectively. Partial response (PR) was seen in 35.3% of patients (n = 24), stable disease (SD) in 63.2% (n = 43), and progressive disease in 1.5% (n = 1). PET imaging was available in 25 patients, and 21 (84%) had a complete response, PR, or SD. The median OS was 6.6 months (95% confidence interval [CI], 5.0–9.2 mo). The hazard ratio (HR) for OS on multivariate analysis was 0.39 (95% CI, 0.23–0.66) for tumor burden less than 25% compared with greater burden. Elevated bilirubin levels were shown to reduce OS. The HR for hepatic progression was 0.22 (95% CI, 0.05–0.98) for solitary versus multifocal disease.ConclusionsLocoregional therapy with ⁹⁰Y radioembolization is safe and stops or delays the progression of targeted chemorefractory BCLMs. Adverse prognosticators were identified.     

Percutaneous Cryoablation of Hepatic Tumors Adjacent to the Gallbladder: Assessment of Safety and Effectiveness

PurposeTo assess safety and effectiveness of percutaneous image-guided cryoablation of hepatic tumors adjacent to the gallbladder.Materials and MethodsTwenty-one cryoablation procedures were performed to treat 19 hepatic tumors (mean size, 2.7 cm; range, 1.0–5.0 cm) adjacent to the gallbladder in 17 patients (11 male; mean age, 59.2 y; range, 40–82 y) under computed tomography (n = 15) or magnetic resonance imaging (n = 6) guidance in a retrospective study. All tumors (mean size, 2.67 cm; range, 1.0–5.0 cm) were within 1 cm (mean, 0.4 cm) of the gallbladder; seven (33%) were contiguous with the gallbladder. Primary outcomes included complication rate and severity and postprocedure gallbladder imaging findings. Secondary outcomes included technical success and technique effectiveness at 6 months.ResultsComplications occurred in six of 21 procedures (29%); one (5%) was severe. Ice balls extended into the gallbladder lumen in 20 of 21 procedures (95%); no gallbladder-related complications occurred. The most common gallbladder imaging finding was mild, asymptomatic focal wall thickening after nine of 21 procedures (42%), which resolved on follow-up. Technical success was achieved in 19 of 21 sessions (90%). Six-month follow-up was available for 16 tumors; of these, all but two (87%) had no imaging evidence of local tumor progression.ConclusionsPercutaneous cryoablation of hepatic tumors adjacent to the gallbladder can be performed safely and successfully. Although postprocedural gallbladder changes are common, they are self-limited and clinically inconsequential, even when the ice ball extends into the gallbladder lumen.     

Hip Chondrolysis and Femoral Head Osteonecrosis: A Complication of Periacetabular Cryoablation

PurposeTo describe a new complication and retrospectively identify the incidence and risk factors for hip chondrolysis and femoral head osteonecrosis associated with percutaneous cryoablation of periacetabular malignancies.Materials and MethodsIn this retrospective study, 45 patients with a total of 113 musculoskeletal lesions were treated by percutaneous image-guided cryoablation between May 2008 and June 2013. Included in the treated population were 10 patients with a total of 12 periacetabular lesions. Clinical and imaging follow-up of at least 2 months was reviewed for evidence of femoral head osteonecrosis or hip chondrolysis. Parametric and nonparametric statistical methods were used to assess patient demographics and treatment technique and parameters on the development of hip chondrolysis/femoral head osteonecrosis.ResultsHip chondrolysis/femoral head osteonecrosis developed in 40% of patients (four of 10) and in 33% of treated periacetabular lesions (four of 12). All patients in whom chondrolysis/osteonecrosis developed were women. Needle proximity to the acetabulum (< 5 mm) was a significant predictor of chondrolysis/osteonecrosis development (P = .01). Three of the four patients in whom chondrolysis/osteonecrosis developed have undergone total joint replacement.ConclusionsPeriacetabular cryoablation can result in transarticular extension of the ablation zone, which may result in the development of hip chondrolysis and femoral head osteonecrosis. The proximity of the cryoablation probe to the acetabulum is a significant risk factor in the development of this complication.