Distributed three-dimensional simulation of B-mode ultrasound imaging using a first-order k-space method

Effect of ultrasound angle for radial artery cannulation in adults: a randomized controlled trial

BACKGROUND

Although the first attempt success rate of radial artery cannulation has been significantly improved by using dynamic needle tip positioning (DNTP) method, there are still problems with long cannulation time. We hereby observe the effect of ultrasound angle for radial artery cannulation in adult patients.

METHODS

Adult patients scheduled to undergo elective surgeries with continuous invasive blood pressure monitoring were included and randomly allocated into either a U-P-artery (ultrasound probe perpendicular to the artery) or U-P-needle (ultrasound probe perpendicular to the needle) group. The primary outcome measure was cannulation time at the first attempt, the secondary outcome measures included the first attempt success rate, number of attempts and the total puncture procedure duration. In addition, the incidence of complications was included as secondary outcomes.

RESULTS

Fifty-nine patients were evaluated finally. The cannulation time at the first attempt in U-P-needle group (N.=28) was significantly lower than that in U-P-artery group (N.=31; median [IQR]: 16 [13.5-20] seconds vs. 41 [25.5-54.5] seconds, P<0.001). The total puncture procedure duration in group U-P-needle was also shorter than that in the group U-P-artery (median [IQR]: 17.4 [13.5-20] seconds vs. 52.2 [25.5-54.5] seconds, P<0.001). No significant difference was observed with respect to first-attempt success rate (96.4% vs. 93.5%, relative risk: 0.97, 95% CI: 0.863-1.0907, P=0.615). The number of attempts showed no statistical difference as well.

CONCLUSIONS

The usage of the U-P-needle approach could remarkably reduce radial arterial cannulation time at the first attempt as well as total puncture procedure duration, comparing with the U-P-artery approach.

Tissue classification using ultrasound-induced variations in acoustic backscattering features

Ultrasound (US) radio-frequency (RF) time series is an effective tissue classification method that enables accurate cancer diagnosis, but the mechanisms underlying this method are not completely understood. This paper presents a model to describe the variations in tissue temperature and sound speed that take place during the RF time series scanning procedures and relate these variations to US backscattering. The model was used to derive four novel characterization features. These features were used to classify three animal tissues, and they obtained accuracies as high as 88.01%. The performance of the proposed features was compared with RF time series features proposed in a previous study. The results indicated that the US-induced variations in tissue temperature and sound speed, which were used to derive the proposed features, were important contributors to the tissue typing capabilities of the RF time series. Simulations carried out to estimate the heating induced during the scanning procedure employed in this study showed temperature rises lower than 2 °C. The model and results presented in this paper can be used to improve the RF time series.

Shadow effects in simulated ultrasound images derived from computed tomography images using a focused beam tracing model

Simulation of ultrasound images based on computed tomography (CT) data has previously been performed with different approaches. Shadow effects are normally pronounced in ultrasound images, so they should be included in the simulation. In this study, a method to capture the shadow effects has been developed, which makes the simulated ultrasound images appear more realistic. The method using a focused beam tracing model gives diffuse shadows that are similar to the ones observed in measurements on real objects. Ultrasound images of a cod (Gadus morhua) were obtained with a BK Medical 2202 ProFocus ultrasound scanner (BK Medical, Herlev, Denmark) equipped with a dedicated research interface giving access to beamformed radio frequency data. CT images were obtained with an Aquilion ONE Toshiba CT scanner (Toshiba Medical Systems Corp., Tochigi, Japan). CT data were mapped from Hounsfield units to backscatter strength, attenuation coefficients, and characteristic acoustic impedance. The focused beam tracing model was used to create maps of the transmission coefficient and scattering strength maps. Field II was then used to simulate an ultrasound image of 38.9 × 55.3 × 4.5 mm, using 10(6) point scatterers. As there is no quantitative method to assess quality of a simulated ultrasound image compared to a measured one, visual inspection was used for evaluation.

Time domain simulation of harmonic ultrasound images and beam patterns in 3D using the k-space pseudospectral method

A k-space pseudospectral model is developed for the fast full-wave simulation of nonlinear ultrasound propagation through heterogeneous media. The model uses a novel equation of state to account for nonlinearity in addition to power law absorption. The spectral calculation of the spatial gradients enables a significant reduction in the number of required grid nodes compared to finite difference methods. The model is parallelized using a graphical processing unit (GPU) which allows the simulation of individual ultrasound scan lines using a 256 x 256 x 128 voxel grid in less than five minutes. Several numerical examples are given, including the simulation of harmonic ultrasound images and beam patterns using a linear phased array transducer.

Modeling power law absorption and dispersion for acoustic propagation using the fractional Laplacian

The efficient simulation of wave propagation through lossy media in which the absorption follows a frequency power law has many important applications in biomedical ultrasonics. Previous wave equations which use time-domain fractional operators require the storage of the complete pressure field at previous time steps (such operators are convolution based). This makes them unsuitable for many three-dimensional problems of interest. Here, a wave equation that utilizes two lossy derivative operators based on the fractional Laplacian is derived. These operators account separately for the required power law absorption and dispersion and can be efficiently incorporated into Fourier based pseudospectral and k-space methods without the increase in memory required by their time-domain fractional counterparts. A framework for encoding the developed wave equation using three coupled first-order constitutive equations is discussed, and the model is demonstrated through several one-, two-, and three-dimensional simulations.