Relationship between myocardial tissue density measured by microgravimetry and sound speed measured by acoustic microscopy

If myocardial tissue can be assumed to be fluid-like, myocardial tissue elasticity can be estimated by the sound speed of tissue based on the equation K=ρc², where K is the elastic bulk modulus, ρ is density, and c is the sound speed of tissue. However, little data exist regarding the relationship between the sound speed of tissue and tissue density. The purpose of the present study was to evaluate the relationship between the sound speed of tissue and tissue density of various diseased myocardia. Myocardial tissue specimens at autopsy were obtained from 10 control patients without cardiovascular disease, 8 patients with pressure overload left ventricular hypertrophy (POLVH), and 8 patients with cardiac amyloidosis (AMD). Myocardial tissue sound speed was measured using a scanning acoustic microscope operating in the frequency of 450 MHz, and tissue density was measured by microgravimetry. The sound speed in POLVH (1639 ± 17 m/s) was higher and that in AMD (1565 ± 11 m/s) was lower than that in control patients (1615 ± 15 m/s) (p < 0.001) at the temperature of 20–22°C. The density in POLVH (1.087 ± 0.004 g/cm³) was higher and that in AMD (1.072 ± 0.003 g/cm³) was lower than that in control patients (1.082 ± 0.003 g/cm³) (p < 0.001). Tissue density correlated with sound speed in all three groups (r = 0.96, p < 0.001). Therefore, myocardial tissue sound speed data obtained by acoustic microscopy enabled us to evaluate tissue elasticity without measuring tissue density directly.     

Variance of speed of sound and correlation with acoustic impedance in canine corneas

The clinical standard for measuring corneal thickness is ultrasound pachymetry that assumes a constant speed of sound. The purpose of this study was to examine the variance of speed of sound and its relationship with acoustic impedance in healthy eyes of canines with a large age span. Corneal speed of sound and acoustic impedance were measured in 34 canine eyes at room temperature (21 ± 1°C). The mean speed of sound was 1577 ± 10 m/s ranging from 1553 to 1594 m/s. There was a strong correlation between speed of sound and acoustic impedance (R = 0.84, p < 0.001). Corneal speed of sound had a small variance in healthy canines over 1-year-old, but was significantly lower in younger canines suggesting an age effect. The strong correlation between corneal speed of sound and acoustic impedance may offer a potential means to noninvasively detect abnormal speed of sound for more accurate corneal thickness estimation.     

Influence of tissue preparation on the high-frequency acoustic properties of normal kidney tissue

The influence of various tissue preparations on the acoustic properties of normal kidney tissue at high frequencies was investigated. Eight surgically excised normal kidney tissue specimens were classified into three groups: (i) fresh, frozen section, (ii) formalin-fixed, frozen section and (iii) formalin-fixed, paraffin section. Scanning acoustic microscopy operating in the frequency range of 100–200 MHz was used to display the two-dimensional distribution of attenuation constant and sound speed. Our results indicate that (i) there is no significant variation in both acoustic parameters between the three tissue groups, (ii) fixation by 10% formalin produces no significant change in the acoustic parameters, (iii) in fat-free tissue regions, the acoustic parameters are independent of preparation method and (iv) frozen sections must be used to assess the acoustic parameters in fat-rich tissues.     

Evaluation of a novel solid-state method for determining the acoustic power generated by physiotherapy ultrasound transducers

A new secondary method of determining ultrasound power is presented based on the pyroelectricity of a thin membrane of the piezoelectric polymer, polyvinylidene fluoride (PVDF). In operation, the membrane is backed by a polyurethane-based rubber material that is extremely attenuating to ultrasound, resulting in the majority of the acoustic power applied to the PVDF being absorbed within a short distance of the membrane-backing interface. The resulting rapid heating leads to a pyroelectric voltage being generated across the electrodes of the sensor that, under appropriate conditions, is related to the rate of change of temperature with respect to time. For times immediately after changes in transducer excitation (switching either ON or OFF), the change in the pyroelectric voltage is proportional to the delivered ultrasound power level. This paper describes a systematic evaluation of the measurement concept applied at physiotherapy frequencies and power levels, investigating key aspects such as repeatability, linearity and sensitivity. The research demonstrates the way that heating of the backing material affects the sensor performance, but outlines the potential of the method as a reproducible, rapid, solid-state method of determining power, requiring calibration using a known ultrasound power source. (E-mail: bajram.zeqiri@npl.co.uk).     

A novel automated method to measure total antioxidant response against potent free radical reactions

OBJECTIVES: Oxidative damage of biomolecules occurs as a result of potent free radical reactions. In this study, a novel, colorimetric and fully automated method for measuring total antioxidant response (TAR) against potent free radical reactions is described. DESIGN AND METHODS: Potent free radical reactions were initiated with the production of hydroxyl radical (OH(*)) via Fenton reaction, and the rate of the reactions was monitored by following the absorbance of colored dianisidyl radicals. Ortho-dianisidine (10 mM) and ferrous ammonium sulfate (45 microM) were dissolved in KCl/HCl solution (75 mM, pH 1.8). This mixture was named as Reagent 1 and hydrogen peroxide solution (7.5 mM) as Reagent 2. The OH(*), produced by mixing of R1 and R2, oxidized o-dianisidine molecules into dianisidyl radicals, leading to a bright yellow-brown color development within seconds. Antioxidants, present in the sample, suppressed the color formation to a degree that is proportional to their concentrations. The method was applied to an automated analyzer and analytical performance characteristics of the assay were determined. RESULTS: Vitamin C and Trolox, reduced glutathione, bilirubin, uric acid and (+/-)-catechin solutions suppressed the color formation depending on their concentrations. Serum TAR against potent free radical reactions was lower in patients with chronic renal failure (1.13 +/- 0.21 mmol Trolox equiv./l) and was higher in the individuals with neonatal icterus (2.82 +/- 1.18 mmol Trolox equiv./l) than in healthy subjects (1.54 +/- 0.15 mmol Trolox equiv./l). CONCLUSIONS: The easy, inexpensive and fully automated method described can be used to measure TAR of samples against potent free radical reactions.     

A new method of obtaining an acoustic impedance profile for characterization of tissue structures

A special method of processing an echographic signal is described. This method is used to estimate the reflected impulse response of the media examined, without employing conventional deconvolution techniques. Under certain conditions, this impulse response can be used to obtain quantitative results concerning the acoustic impedance of different structures.

Measurements have been made, leading to definition of the possibilities of the method: dynamic impedance range is now only limited by the technology of the equipment used, and the influence of noise on impedance profile quality is very low. Nevertheless, depth definition appears insufficient. The initial application of the method related to an excised canine aorta.     

Short-term results in canines of novel stent-graft design for chimney technique in TEVAR

IntroductionParallel stent-stent grafting is a major endovascular technique used to preserve the supra-aortic branches during thoracic endovascular aortic repair (TEVAR) of aortic pathologies involving the aortic arch. The short- and mid-term results of this technique are satisfactory; however, endoleak remains a major concern. Thus, here we designed a new chimney stent-graft to decrease the endoleak rate.AimTo testify the feasibility and safety of the new chimney stent-graft system in a canine model.Material and methodsSix Labrador retrievers were used. Pre-operative data were collected and all operations were performed under general anesthesia. The main and chimney stent-grafts were implanted through the abdominal aorta and left subclavian artery approaches, respectively. Completion digital subtraction angiography (DSA) was performed to confirm the immediate outcomes. All dogs were fed separately for 6 months and sacrificed after aortic angiography. The thoracic aorta and the main and chimney stent-grafts were harvested for histopathologic examination.ResultsNo complications were found in follow-up DSA. All branch arteries were patent. Inflammatory responses were observed around the stent-grafts in 3 experimental animals, and slight hyperplasia was observed in the surrounding tissues compared with the normal vessels. There was no mural thrombus in the stent, endothelial cells were noted on the inner surface of the stent, and thrombus was formed in the outer skirt and gutter area. The histopathologic examinations revealed similar results to those of gross necropsy observations.ConclusionsThis study demonstrated the feasibility and safety of the Longuette stent-graft and the first to report a revised stent-graft specific for chimney technique.     

Evidence-based cross validation for acoustic power transmission for a novel treatment system

Introduction: The novel Trans-Fusimo Treatment System (TTS) is designed to control Magnetic Resonance guided Focused Ultrasound (MRgFUS) therapy to ablate liver tumours under respiratory motion. It is crucial to deliver the acoustic power within tolerance limits for effective liver tumour treatment via MRgFUS. Before application in a clinical setting, evidence of reproducibility and reliability is a must for safe practice.

Materials and methods: The TTS software delivers the acoustic power via ExAblate-2100 Conformal Bone System (CBS) transducer. A built-in quality assurance application was developed to measure the force values, using a novel protocol to measure the efficiency for the electrical power values of 100 and 150W for 6s of sonication. This procedure was repeated 30 times by two independent users against the clinically approved ExAblate-2100 CBS for cross-validation.

Results: Both systems proved to deliver the power within the accepted efficiency levels (70–90%). Two sample t-tests were used to assess the differences in force values between the ExAblate-2100 CBS and the TTS (p?>?0.05). Bland-Altman plots were used to demonstrate the limits of agreement between the two systems falling within the 10% limits of agreement. Two sample t-tests indicated that TTS does not have user dependency (p?>?0.05).

Conclusions: The TTS software proved to deliver the acoustic power without exceeding the safety levels. Results provide evidence as a part of ISO13485 regulations for CE marking purposes. The developed methodology could be utilised as a part of quality assurance system in clinical settings; when the TTS is used in clinical practice.     

声学密度定量技术评价轻度心肌缺血的价值探讨

目的探讨声学密度定量技术在评价轻度心肌缺血中的价值。方法经单光子发射型计算机断层扫描检测的32例患者,采集舒张末期左室乳头肌水平短轴切面超声图像。应用超声定量分析仪分别测量各节段心内膜及相邻心肌平均回声强度,并计算其比值。比较缺血区与非缺血区回声强度及其心内膜与心肌回声强度比值。结果缺血节段心内膜较相邻心肌回声强度更高,缺血节段心内膜与心肌回声强度比值较同一患者非缺血节段及无病变患者相应节段更高。结论区域性心内膜与心肌回声强度比值增高可能是心肌轻度缺血的一个重要指标。     

Evaluation of acoustic properties of the live human smooth-muscle cell using scanning acoustic microscopy

This study was performed to measure the acoustic propagation speed in live human aortic smooth-muscle cells (HASMC), using scanning acoustic microscopy (SAM) and a novel measurement theory that permits the measurement of the acoustic propagation speed in biological samples of unknown thickness. C-mode and X–Z-mode images of HASMC under three different conditions: growing (G); differential (D); and on hypotonic loading (H), were acquired using 100-MHz, 450-MHz and 600-MHz ultrasound. The images exhibit features related to the cell surface curvature and intracellular structure. The theory supporting the methodology is derived in this article and makes use of the interference fringes within the focusing lens of the high-frequency transducer. The propagation speed in the cells was calculated from the location of the interference fringe on the C-mode images and the fringe shift on the X–Y-mode images with 450-MHz ultrasound. The propagation speed in D (1624 ± 16 m/s) was significantly higher than those in G (1571 ± 14 m/s, p < 0.05) and H (1585 ± 8 m/s, p < 0.05). Scanning acoustic microscope measurements, along with the described theory, are useful for studying the acoustic properties of live cells ex vivo and have applications in both pathophysiology and biomechanics.     

高血压病左心室构型对左心房功能影响的研究

目的 应用声学定量(AQ)技术评价高血压病不同左心室构型表达对左心房功能的影响。方法 对照组20例，高血压病组68例，根据左心室心肌质量指数(mass index)和相对室壁厚度，将高血压病组分为左心室几何构型正常组、左心室向心性重构组、左心室向心性肥厚组和左心室离心性肥厚组。应用AQ技术，测量左心房存储容积(RV)、射血分数(LVEF)和管道容积(CV)，分别代表左心房存储器功能、助力泵功能和管道功能。结果 与对照组比较，几何构型正常组和左心室向心性重构组RV增大；向心性肥厚组RV、LAEF增大，CV减低；离心性肥厚组RV增大，LAEF和CV减低。结论 左心房通过其存储器功能、助力泵功能和管道功能的重新分配，代偿高血压病不同左心室构型引起的左心室充盈异常；左心室离心性肥厚时，左心房功能失代偿。     

High frequency ultrasound tissue characterization and acoustic microscopy of intracellular changes

The objective of this work is to investigate changes in the acoustic properties of cells when exposed to chemotherapy for monitoring treatment response. High frequency ultrasound spectroscopy (10-60 MHz) and scanning acoustic microscopy (0.9 GHz) were performed on HeLa cells (Ackermann et al. 1954, Masters 2002) that were exposed to the chemotherapeutic agent cisplatin. Ultrasonic radio-frequency data were acquired from pellets containing HeLa cells after exposure to cisplatin to induce apoptosis. Scanning acoustic and laser fluorescence microscopy images were recorded from single HeLa cells exposed to the same drug. Data acquisition in both cases was performed at several time points throughout the chemotherapeutic treatment for up to 27 h. In the high frequency ultrasound investigation, normalized power spectra were calculated within a region-of-interest. A 20 MHz transducer (f-number 2.35) and a 40 MHz transducer (f-number 3) were used for the data collection in the high frequency ultrasound experiments. The backscatter coefficients, integrated backscatter coefficients, mid-band fit and spectral slope were computed as a function of treatment time to monitor acoustical property changes during apoptosis. Acoustic attenuation was measured using the spectral substitution technique at all time points. Spectral parameter changes were detected after 12 h of exposure and coincided with the initiation of cell damage as assessed by optical microscopy. Integrated backscatter coefficients increased by over 100% between 0 h and 24 h of treatment, with small changes in the associated attenuation ( approximately 0.1 dB/[MHz cm]). Acoustic microscopy was performed at 0.9 GHz frequency. The cell structure was imaged using staining in laser fluorescence microscopy. All cells showed excellent correspondence between the locations of apoptotic nuclear condensation observed in optical imaging and changes in attenuation contrast in acoustic microscopy images. The time after drug exposure at which such changes occurred in the optical images were coincident with the time of changes detected in the acoustic microscopy images and the high frequency ultrasound experiments. (E-mail: Sebastian.Brand@gmail.com).     

声辐射力脉冲成像技术在肝纤维化评估中的初步应用

目的探讨声辐射力脉冲(acoustic radiation force impulse,ARFI)成像技术初步应用于肝纤维化评估的价值。方法使用ARFI成像技术检测50例正常受检者、50例非酒精性单纯性脂肪肝患者及18例经病理证实的肝纤维化患者,比较3组的弹性测值。结果 3组受检者弹性测值间差异有统计学意义(P<0.001)。结论 ARFI成像技术对于评估肝纤维化具有临床应用价值。     

A novel method of intra-hepatic bile-duct closure using the LigaSure device

The LigaSure Vessel Sealing System is an energy-based haemostatic tool that produces permanent vessel occlusion. It was developed as an alternative method for ligating vascular bundles quickly and reliably during surgery. This study demonstrates its efficacy on intra-hepatic bile ducts in a porcine in vitro model.     

脑卒中患者功能恢复的测定:自由步行与最大步行速度的比较

目的比较脑卒中患者自由与最大步行速度在评定功能恢复结果中的价值。方法对 3 2例恢复步行能力的脑卒中偏瘫患者 ,测定自然舒适状态下的 10m步行速度和 10m最大步行速度 ,用Fugl Meyer评定法评定下肢运动功能 ,用Berg平衡量表评定平衡功能 ,用功能独立性测量中的移动类项目测量综合移动能力。对自由步行和最大步行速度与临床评定变量间进行Pearson相关分析。结果自由步行和最大步行速度之间呈高度正相关 (r =0 95 3 ,P <0 0 0 1) ;自由步行和最大步行速度与平衡功能、下肢运动功能和综合移动能力之间呈高度正相关 (r =0 742— 0 83 4,P <0 0 0 1) ;但自由步行速度与功能恢复的相关性更高 (r =0 787— 0 83 4,P <0 0 0 1)。结论自由步行和最大步行速度都能够反映功能恢复结果 ,但是自由步行速度测定方法更实用、更安全和更敏感。     

A new method of measuring in vivo sound speed in the reflection mode

This paper describes a new method for in vivo sound measurement in the reflection mode. The mean sound speed between the reflector and linear array transducer is measured using the following three parameters: time of flight, time of flight difference, and distance between two receiver elements. To detect time of flight, the system delay-line time compensator is adjusted to obtain the sharpest reflector image. This method was evaluated in vivo in human livers, specifically 26 normal, 27 cirrhotic, and 15 fatty livers. The mean sound speed between diaphragm and the transducer was obtained. The measured sound speed was significantly higher in cirrhotic livers and lower in fatty livers.     

A reflection technique for measurement of high acoustic intensities

A number of commercially available hydrophones having a uniform frequency response suitable for measurement of pulse echo waveforms overload at high acoustic intensities. A reflection technique which reduces the magnitude of this incident energy is described and permits these hydrophones to measure high intensities without distortion.     

Influence of histochemical preparation on acoustic parameters of liver tissue: A 5-MHz study

In this study the influence of various histological techniques on the acoustic parameters of liver tissue was investigated. Radiofrequency (RF) echographic data were obtained in vitro from 21 liver samples taken from 8 white New Zealander rabbits. The samples were measured in four different subsequent histological tissue processing conditions (freshly excised, 4% buffered formalin fixed, after it went through a paraffin cycle and after staining with hematoxylin and eosin). The acoustic parameters that were obtained from the rf data were velocity of sound, slope of the attenuation coefficient versus frequency between 1.9 and 6.9 MHz, attenuation coefficient at 4.4 MHz, slope of the backscattering spectrum between 1.9 and 6.9 MHz, and intercept of the backscattering spectrum. It was found that fixation by formalin preserves the acoustic properties of the tissue to a reasonable extent. Embedding in paraffin and deparaffinizing induces large changes in the acoustic properties of the tissue. As an alternative, freezing prior to cutting, rather than the paraffin cycle, was investigated also in 10 liver samples obtained from 4 New Zealander rabbits. This method produced no significant changes of the acoustic parameters and should therefore be preferred in acoustic microscopy.     

Anti-hyperalgesic effects of a novel TRPM8 agonist in neuropathic rats: A comparison with topical menthol

Menthol has historically been used topically to alleviate various pain conditions. At low concentrations, this non-selective TRPM8 agonist elicits a cooling sensation, however higher concentrations result in cold hyperalgesia in normal subjects and paradoxically analgesia in neuropathic patients. Through behavioural and electrophysiological means, we examined whether this back-translated into a pre-clinical rodent model. Menthol was applied topically to the hind paws of naive and spinal nerve-ligated (SNL) rats. In behavioural assays, menthol did not affect withdrawal thresholds to mechanical stimulation and 10% and 40% menthol rarely sensitised withdrawals to innocuous cooling in naïve rats. However, in SNL rats, 10% and 40% menthol alleviated cold hypersensitivity. This was partly corroborated by in vivo electrophysiological recordings of dorsal horn lamina V/VI neurones. As several studies have implicated TRPM8 in analgesia, we examined whether a novel systemically available TRPM8 agonist, M8-Ag, had more potent anti-hyperalgesic effects than menthol in neuropathic rats. In vitro, M8-Ag activates TRPM8, expressed in HEK293 cells, with an EC50 of 44.97 nM. In vivo, M8-Ag inhibited neuronal responses to innocuous and noxious cooling in SNL rats with no effect in sham-operated rats. This effect was modality selective; M8-Ag did not alter neuronal responses to mechanical, heat or brush stimulation. In addition, M8-Ag attenuated behavioural hypersensitivity to innocuous cooling but not mechanical stimulation. These data suggest that menthol induced hyperalgesia is not consistently replicable in the rat and that the analgesic properties are revealed by injury. Systemic TRPM8 agonists might be beneficial in neuropathy without affecting normal cold sensitivity.     

Measurement of the ultrasonic energy radiated by transducers used in echography.

A method based on the response of a thick piezoelectric disc to an ultrasonic plane wave and enabling the measurement of the energy in short pulses is described. The energy characteristics of three transducers, differing in frequency and diameter, are given. Their mean acoustic intensities are respectively 0.08, 0.26 and 14mW/cm² for repetition rates of 1 kHz, 1 kHz and 2.4 kHz