Miniaturised ultrasound evaluation at the bedside.

PURPOSE: "Point-of-Care Ultrasound" (POCUS) is now a familiar term. Although the European Federation of Societies for Ultrasound in Medicine and Biology (ESFUMB) published a position paper about its usage (Nielsen et al. in Ultraschall Med 40(1):30-39. https://doi.org/10.1055/a-0783-2303 , 2019), there has not been much scientific focus on its utility in uro-nephrological clinical practice thus far. The aim of this study was to evaluate the present usage of pocket ultrasound devices at the bedside. METHODS: 27 investigators (all medical doctors with at least 6 months of experience in sonography) performed 280 bedside examinations using a pocket ultrasound device for common clinical issues. RESULTS: The most frequent indications included evaluation of hydronephrosis (147), volume management including assessment of dimension of the vena cava inferior (IVC) (195), detection of pleural, pericardial and abdominal effusions (113) as well as residual urine (52). In 90%, specific clinical questions were effectively answered by the pocket ultrasound device alone. CONCLUSIONS: POCUS can be useful in the uro-nephrological field. In the hands of an experienced investigator, it saves time and, when it is realised that departmental ultrasound is not cheap, there is also an economic benefit with applicability within both inpatient and outpatient clinic settings. While acknowledging its technical limits, pocket ultrasound devices may nevertheless be helpful in targeted situations for triage or for bedside follow-up exams after earlier high-end ultrasound-based diagnosis.

Does standoff material affect acoustic radiation force impulse elastography? A preclinical study of a modified elastography phantom.

PURPOSE: This study was conducted to determine the influence of standoff material on acoustic radiation force impulse (ARFI) measurements in an elasticity phantom by using two different probes. METHODS: Using ARFI elastography, 10 observers measured the shear wave velocity (SWV, m/sec) in different lesions of an elasticity phantom with a convex 4C1 probe and a linear 9L4 probe. The experimental setup was expanded by the use of an interposed piece of porcine muscle as standoff material. The probe pressure on the phantom was registered. RESULTS: Faulty ARFI measurements occurred more often when quantifying the hardest lesion (74.0 kPa 4.97 m/sec) by the 9L4 probe with the porcine muscle as a standoff material interposed between the probe and the phantom. The success rate for ARFI measurements in these series was 52.4%, compared with 99.5% in the other series. The SWV values measured with the 9L4 probe were significantly higher (3.33±1.39 m/sec vs. 2.60±0.74 m/sec, P<0.001 in the group without muscle) and were closer to the reference value than those measured with the 4C1 probe (0.25±0.23 m/sec vs. 0.85±1.21 m/sec, P<0.001 in the same group). The SWV values measured when using the muscle as a standoff material were lower than those without the muscle (significant for 9L4, P=0.040). The deviation from the reference value and the variance increased significantly with the 9L4 probe if the muscle was in situ (B=0.27, P=0.004 and B=0.32, P<0.001). In our study, the pressure exerted by the operator had no effect on the SWV values. CONCLUSION: The presence of porcine muscle acting as a standoff material influenced the occurrence of failed measurements as well as the variance and the accuracy of the measured values. The linear high-frequency probe was particularly affected.

Preclinical evaluation of acoustic radiation force impulse measurements in regions of heterogeneous elasticity.

PURPOSE: The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes. METHODS: Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex 4C1 probe and the linear 9L4 probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively). RESULTS: The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the 9L4 probe than in the case of the 4C1 probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050). CONCLUSION: Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures.