Non-linear Wave Propagation and Safety Standards for Diagnostic Ultrasound Devices

Safety standards for clinical diagnostic ultrasonic devices were developed for use in relatively low-frequency systems (1–10 MHz), under the assumption that non-linear effects would be negligible. This article reviews ways in which neglecting non-linear wave propagation affects the measurements and calculations required to comply with safety standards and U.S. Food and Drug Administration guidance that recognizes these standards. An attempt is made to evaluate whether ignoring non-linear effects could result in significant error in the exposure quantities defined in these standards at either low or high frequencies, based on published literature. This article maintains that although non-linear effects have been considered in some parts of safety standards related to hydrophone requirements, the coverage is inadequate, especially for modern equipment with high working frequencies. A new approach is required to assess the magnitude of thermal heating for recently developed high-frequency systems to incorporate non-linear effects. In contrast, the current approach for evaluating the risk of cavitation can be used after appropriate modifications.     

超声弹性成像及硬环征、直方图分析鉴别乳腺肿块良恶性的诊断价值

目的：本研究旨在比较弹性成像、弹性成像联合“硬环征”、弹性成像直方图分析的诊断价值。方法：选取2017年1月至2019年1月间于陆军军医大学第二附属医院普通外科就诊的共59个乳房肿块构成本研究组。启动弹性成像功能采集数据,然后在弹性成像图上调节阈值显示硬环征,之后勾选直方图分析。结果：直方图分析的诊断性能(AUC=0.93)优于弹性成像联合“硬环征”(AUC= 0.87)和弹性成像(AUC=0.81)。结论：超声弹性成像直方图分析方法有助于乳腺良、恶性病变的分类,“硬环征”也可提高弹性成像的准确性,有助于提高医师鉴别乳腺肿块良恶性的能力。     

超声定位下放射状冲击波与聚焦式冲击波治疗肱二头肌长头腱炎疗效研究

目的 通过超声定位比较放射状冲击波(radial shock wave therapy,RSWT)与聚焦式冲击波(focus shock wave therapy,FSWT)治疗肱二头肌长头腱炎的疗效.方法 分别采用Dolorclast放射状冲击波治疗机或国产慧康ESWO冲击波治疗机治疗,通过超声定位的43例肱二头肌长头腱炎患者.在治疗前、治疗后即刻、治疗后1个月和3个月利用ASES肩关节评分系统评价,和治疗后6个月远期疗效评价.结果 RSWT组与FSWT组的ASES肩关节评分在治疗前差异无统计学意义(P＞0.05),而治疗后即时、1个月和3个月两组ASES肩关节评分同治疗前评分均有统计学意义(P＜0.05).治疗后6个月RSWT组与FSWT组的有效率分别为90.9％(20/22)和85.7％ (18/21),两组比较无统计学差异P＞0.05.结论 在超声定位下放射状冲击波与聚焦式冲击波治疗肱二头肌长头腱炎均具有良好疗效,其中放射状冲击波疗法更为安全、无创和无明显并发症等特点.     

超声波治疗脑梗死的疗效预后和对血浆D-二聚体含量的影响

目的：探讨联用超声波治疗对脑梗死患者急性期血浆D二聚体（D-dimer）含量的影响。方法：发病24h内人院的急性脑梗死患者120例，随机分为超声波组及常规组各60例，均接受神经内科常规药物治疗，超声波组同时联用超声波治疗。2组患者在入院时及治疗3周后进行血浆D-dimer的检测及神经功能缺损评分评定临床疗效；同时选取88例正常健康体检者（健康组）作为阴性对照。随访1年，将死亡及再发卒中记录为终点事件对患者生存曲线进行分析。结果：治疗4周后，超声波组与常规组D-dimer含量与治疗前比较均明显下降（P〈0．05），与常规组比较，超声波组下降速度更明显；但仍高于健康组（P〈0．05）。临床疗效评定，超声波组总有效率明显高于常规组（91．7％与73．3％，P〈0．05）；比较2组生存曲线发现，超声波组终点事件发生率明显低于常规组（11．7％与31．7％，P〈0．05）。结论：急性脑梗死辅以超声波治疗可明显降低血浆D-dimer含量和神经功能缺损程度。     

Analysis of Apparent Integrated Backscatter Coefficient and Backscattered Spectral Centroid Shift in Calcaneus in vivo for the Ultrasonic Evaluation of Osteoporosis

The purposes of our study were to evaluate the correlation among apparent integrated backscatter coefficient (AIB), spectral centroid shift (SCS) of ultrasonic backscatter signals and bone mineral density (BMD) and to examine the effectiveness of ultrasound variables as predictors of osteoporosis. A total of 1011 persons aged 21–80 y old were included. All study participants underwent BMD measurements of the lumbar spine (LSBMD) and the femoral neck (FNBMD). The participants also underwent calcaneal measurements to determine AIB and SCS with central frequencies of 3.5 (one transducer) and 5.0 MHz (the other transducer). AIB decreased with age and was positively correlated with BMD, while SCS increased with age and was negatively correlated with BMD. The correlation coefficient of SCS with LSBMD and FNBMD at 3.5 MHz was −0.72 and −0.70, respectively. The correlation coefficient at 5.0 MHz was −0.75 and −0.74, respectively. The correlation coefficient of AIB with LSBMD and FNBMD at 3.5 MHz was 0.65 and 0.63. The correlation coefficient at 5.0 MHz was 0.59 and 0.55, respectively. The correlation between SCS and BMD was significantly better than the correlation between AIB and BMD. Using receiver operating characteristic analysis, a significant difference was found between the areas under the curve for SCS and AIB at 3.5 MHz (0.781 vs. 0.715, respectively, p < 0.05), as well as at 5.0 MHz (0.782 vs. 0.709, respectively, p < 0.05). The optimum T-score threshold for SCS was -1.3 for both transducers. The sensitivity and specificity of SCS at 3.5 MHz and 5.0 MHz for the optimum threshold were 64%, 85%, 63% and 86%, respectively. In conclusion, the correlations among the ultrasound parameters and BMDs are strong. SCS performs better than AIB in differentiating patients with osteoporosis. Ultrasound variables may be taken into consideration as predictors of osteoporosis in the future considering its portability.     

In Vivo Comparison of Pulse Wave Velocity Estimation Based on Ultrafast Plane Wave Imaging and High-Frame-Rate Focused Transmissions

Ultrasound-based local pulse wave velocity (PWV) estimation, as a measure of arterial stiffness, can be based on fast focused imaging (FFI) or plane wave imaging (PWI). This study was aimed at comparing the accuracy of in vivo PWV estimation using FFI and PWI. Ultrasound radiofrequency data of carotid arteries were acquired in 14 healthy volunteers (25–57 y) by executing the FFI (12 lines, 7200 Hz) and PWI (128 lines, 2000 Hz) methods consecutively. PWV was derived at two time-reference points, dicrotic notch (DN) and systolic foot (SF), for multiple pressure cycles by fitting a linear function through the positions of the peaks of low-pass filtered wall acceleration curves as a function of time. The accuracy of PWV estimation was determined for various cutoff frequencies (10–200 Hz). No statistically significant difference was observed between PWVs estimated by both approaches. The PWV and R² at DN were higher, on average, than those at SF (PWV/R²: FFI SF 5.5/0.92, FFI DN 6.1/0.92; PWI SF 5.4/0.89, PWI DN 6.3/0.95). The use of cutoff frequencies between 40 and 80 Hz provided the most accurate PWVs. Both methods seemed equally suitable for use in clinical practice, although we have a preference for the PWV at DN given the higher R² values.     

Morphological Variation of Nonreentrant Idiopathic Ventricular Tachycardia Originating from the Right Ventricular Outflow Tract and Effect of Radiofrequency Lesion

RF catheter ablation was performed in 16 patients with nonreentrant idiopathic VT originating from the RVOT. All documented VT was monomorphic, but subtle morphological variation in the VT-QRS complex was observed in 10 (63%) of 16 patients. Through endocardial mapping, VT origin was determined within a narrow site (< 0.5 ± 0.5 cm) in 4 of the 10 patients with the morphological variation. In the other 6 of 10 patients, the origin extended to an area of > 0.5 ± 0.5 cm. In VT with morphological variation, the local electrogram at the site of VT origin also showed variation in morphology and activation sequence. For VT of narrow origin, RF application to the site eliminated the VT. However, in VT from a wide arrhythmogenic area, RF current had to be delivered to 3–7 distinct sites to cover the possible origin, and specific QRS configuration of VT and/or PVC was ablated at each of the earliest activation site. All but one VT were successfully ablated by RF current. Subtle morphological variation was frequent in this type of VT, and about half were associated with a wide arrhythmogenic area. Precise mapping and analysis of the efficacy of each BF application might be helpful to better understand the relationship between subtle changes of VT-QRS morphology and their origins.     

射频消融对右室流出道室性早搏的疗效及心肌损伤标记物和自主神经的影响

目的:观察射频消融治疗右室流出道室性早搏的有效性和安全性。方法:对36例症状明显的右室流出道单形性室性早搏患者进行射频消融治疗,观察即刻及术后2月的疗效;测定射频消融术前以及术后检测高敏C反应蛋白(hs-CRP)、血清肌钙蛋白I(cTnI)和磷酸肌酸激酶同工酶(CK-MB)观察心肌损伤。另设健康体检者30例作为正常对照组。结果:射频消融能有效治疗右室流出道室性早搏,消融即刻成功率为100%,远期成功率为94.4%。hs-CRP、CK-MB和cTnI射频消融术后1d较术前明显升高,7d后恢复正常。结论:射频消融术治疗右室流出道室性早搏安全有效。     

Evaluation of Ultrasonic Attenuation in Primary and Secondary Human Liver Tumors and Its Potential Effect on High-Intensity Focused Ultrasound Treatment

Primary and secondary liver tumors are completely different diseases but are usually treated similarly using high-intensity focused ultrasound (HIFU). However, the acoustic parameters of these tissues are not well documented. In this study, attenuation coefficients were evaluated in fresh primary (N = 8) and secondary (N = 13) human liver tumor samples recovered by hepatectomy. The average attenuation coefficients of the primary and secondary liver tumors were 0.10 ± 0.03 and 0.20 ± 0.04 Np/cm/MHz, respectively. The average attenuation coefficients of the liver tissue surrounding the primary and secondary tumors were 0.16 ± 0.07 and 0.07 ± 0.02 Np/cm/MHz, respectively. Numerical simulations performed using these values revealed that completely different HIFU ablation patterns were created in primary and secondary liver tumors using the same exposure parameters. The dimensions of a typical HIFU lesion were two times larger in secondary liver tumors than in primary tumors. HIFU treatment parameters should be set properly according to the acoustic properties of the diseased liver tissue.     

Comparing Myocardial Shear Wave Propagation Velocity Estimation Methods Based on Tissue Displacement,Velocity and Acceleration Data

Shear wave elastography (SWE) is a promising technique used to assess cardiac function through the evaluation of cardiac stiffness non-invasively. However, in the literature, SWE varies in terms of tissue motion data (displacement, velocity or acceleration); method used to characterize mechanical wave propagation (time domain [TD] vs. frequency domain [FD]); and the metric reported (wave speed [WS], shear or Young's modulus). This variety of reported methodologies complicates comparison of reported findings and sheds doubt on which methodology better approximates the true myocardial properties. We therefore conducted a simulation study to investigate the accuracy of various SWE data analysis approaches while varying cardiac geometry and stiffness. Lower WS values were obtained by the TD method compared with the FD method. Acceleration-based WS estimates in the TD were systematically larger than those based on velocity (～10% difference). These observations were confirmed by TD analysis of 32 in vivo SWE mechanical wave measurements. In vivo data quality is typically too low for accurate FD analysis. Therefore, our study suggests using acceleration-based TD analysis for in vivo SWE to minimize underestimation of the true WS and, thus, to maximize the sensitivity of SWE to detect stiffness changes resulting from pathology.     

二维彩色多普勒超声对心脏间隔膨胀瘤的诊断分析

目的：探讨各种原因所致心脏间隔膨胀瘤的超声特征。方法：应用二维彩色多普勒分析45例心脏间隔膨胀瘤形成病因、发生部位、膨胀瘤与心脏血流动力学之间的相互关系。结果：房间隔膨胀瘤及室间隔膜部膨胀瘤多为先天性间隔发育薄弱所致，室间隔肌部膨胀瘤多因心肌梗死导致。结论：膨胀瘤的大小与间隔发育情况、心肌梗死范围有关；膨胀瘤的破裂与瘤壁厚薄及心脏血流动力学有关。     

Effect of Skull Porous Trabecular Structure on Transcranial Ultrasound Imaging in the Presence of Elastic Wave Mode Conversion at Varying Incidence Angle

With the advancement of aberration correction techniques, transcranial ultrasound imaging has exhibited great potential in applications such as imaging neurological function and guiding therapeutic ultrasound. However, the feasibility of transcranial imaging varies among individuals because of the differences in skull acoustic properties. To better understand the fundamental mechanisms underlying the variation in imaging performance, the effect of the structure of the porous trabecular bone on transcranial imaging performance (i.e., target localization errors and resolution) was investigated for the first time through the use of elastic wave simulations and experiments. Simulation studies using high-resolution computed tomography data from ex vivo skull samples revealed that imaging at large incidence angles reduced the target localization error for skulls having low porosity; however, as skull porosity increased, large angles of incidence resulted in degradation of resolution and increased target localization errors. Experimental results indicate that imaging at normal incidence introduced a localization error of 1.85 ± 0.10 mm, while imaging at a large incidence angle (40°) resulted in an increased localization error of 6.54 ± 1.33 mm and caused a single point target to no longer appear as a single, coherent target in the resulting image, which is consistent with simulation results. This first investigation of the effects of skull microstructure on transcranial ultrasound imaging indicates that imaging performance is highly dependent on the porosity of the skull, particularly at non-normal angles of incidence.     

In vivo Ultrafast Quantitative Ultrasound and Shear Wave Elastography Imaging on Farm-Raised Duck Livers during Force Feeding

Shear wave elastography (speed and dispersion), local attenuation coefficient slope and homodyned-K parametric imaging were used for liver steatosis grading. These ultrasound biomarkers rely on physical interactions between shear and compression waves with tissues at both macroscopic and microscopic scales. These techniques were applied in a context not yet studied with ultrasound imaging, that is, monitoring steatosis of force-fed duck livers from pre-force-fed to foie gras stages. Each estimated feature presented a statistically significant trend along the feeding process (p values <10^–3). However, whereas a monotonic increase in the shear wave speed was observed along the process, most quantitative ultrasound features exhibited an absolute maximum value halfway through the process. As the liver fat fraction in foie gras is much higher than that seen clinically, we hypothesized that a change in the ultrasound scattering regime is encountered for high-fat fractions, and consequently, care has to be taken when applying ultrasound biomarkers to grading of severe states of steatosis.     

护理人员睡眠状况调查以及夜班工作对睡眠的影响

目的调查护理人员的睡眠状况,以及夜班工作对睡眠的影响.方法对348名护理人员、50名通讯值班员,100名夜勤人员进行匹兹堡睡眠质量指数测查和睡眠特征分析,采用DSM-Ⅳ标准进行失眠症诊断.结果护理人员中睡眠状况差者占71.86%,符合DSM-Ⅳ中原发性失眠诊断者占38.22%;通讯值班员该两项比例分别为74%和48%;夜勤人员分别为26.76%和7%.护理人员睡眠状况差与年龄、从事夜班年限有关;护理人员与通讯值班员的睡眠状况相似（ P〉0.05）,与夜勤人员的睡眠状况有非常显著性差异（ P＜0.01）.结论轮班工作方式对护理人员的睡眠状况影响较大,使其在入睡时间、睡眠时间、睡眠效率、日间功能等方面普遍存在一定障碍,但对此不倾向于使用药物治疗,可采用非药物疗法如穴位按摩、自我保健等.