Ultrasound Evaluation of Soft-Tissue Foreign Bodies by US Army Medics

Accuracy of Emergency Medicine Residents Using Point-of-Care Ultrasound (POCUS) to Detect Retained Stingray Barbs

BACKGROUND

Stingray envenomation is a common presenting complaint for coastal emergency departments in the United States. Currently, radiograph is the gold standard to evaluate for a retained stingray barb, but ultrasound may be a useful tool to detect retained barbs.

OBJECTIVE

To determine if emergency medicine residents could use ultrasound to identify stingray barbs embedded in animal tissue models. A secondary objective was to determine if resident experience affected their ability to detect stingray barbs.

METHODS

Thirty-two emergency medicine residents participated in the study. After a short didactic session on foreign body identification with ultrasound, they rotated through six simulation stations and were asked to identify whether a stingray barb was present in pig and chicken tissue models. They were given 2 min per model to identify the presence, size, and depth of a stingray barb. Pre- and postexperiment surveys were collected to assess the residents' level of experience and confidence regarding foreign body identification using ultrasound.

RESULTS

Residents accurately identified barbs in chicken drumsticks with a sensitivity of 72.92% (95% confidence interval [CI] 63.89-81.48) and a specificity of 64.58% (95% CI 54.16-74.08), and in pig's feet with a sensitivity of 50.00% (95% CI 39.62-60.38) and specificity of 68.75% (95% CI 58.48-77.82). There was no statistically significant difference regarding accuracy for any outcome measured based on experience or level of training.

CONCLUSIONS

The use of point-of-care ultrasound by novice sonographers lacks sensitivity to identify retained stingray barbs in animal models and is not significantly impacted by resident experience with point-of-care ultrasound.

Characterisation of multi-layered structures using a vector-based gradient descent algorithm at terahertz frequencies

Material characterisation and imaging applications using terahertz radiation have gained interest in the past few years due to their enormous potential for industrial applications. The availability of fast terahertz spectrometers or multi-pixel terahertz cameras has accelerated research in this domain. In this work, we present a novel vector-based implementation of the gradient descent algorithm to fit the measured transmission and reflection coefficients of multilayered objects to a scattering parameter-based model, without requiring any analytical formulation of the error function. We thereby extract thicknesses and refractive indices of the layers within a maximum 2% error margin. Using the precise thickness estimates, we further image a 50 nm-thick Siemens star deposited on a silicon substrate using wavelengths larger than 300 µm. The vector-based algorithm heuristically finds the error minimum where the optimisation problem cannot be analytically formulated, which can be utilised also for applications outside the terahertz domain.

Subcutaneous Low-Density Foreign Bodies Detection via Grating-Based Multimodal X-ray Imaging

Detecting low-density foreign bodies within soft tissues still stands for a serious challenge. Grating-based multimodal X-ray imaging typically has low hardware requirements while simultaneously providing three kinds of imaging information, i.e., absorption, phase-contrast, and dark-field. We aimed to explore the capacity of grating-based multimodal X-ray imaging technology for detecting common foreign bodies within subcutaneous tissues, and to assess the advantages as well as disadvantages of the three kinds of images obtained via grating-based X-ray multimodal technology in relation to diverse kinds of foreign bodies within different tissues. In this study, metal, glass, wood, plastic, graphite, and ceramic foreign bodies were injected into chunks of the pig adipose tissue and chicken thigh muscles. Next, a grating-based multimodal X-ray imaging device developed in our laboratory was used to detect the above foreign bodies within the adipose and muscle tissues. Our results show that grating-based multimodal X-ray imaging clearly revealed the subcutaneous foreign bodies within the adipose and muscle tissues by acquiring complementary absorption, phase-contrast, and dark-field imaging data in a single shot. Grating-based multimodal X-ray imaging has an exciting potential to detect foreign bodies underneath the epidermis.

Ultrasonography in soft-tissue foreign-body detection: a phantom study

Purpose

Foreign body implantation into the soft tissues, either in the early period or late period, is a common cause of emergency department admissions. Direct X-rays are preferred in the diagnosis of soft-tissue foreign-bodies. Herein, we aimed to analyse the detection rates of foreign bodies of various sizes placed in phantoms implanted into soft tissue by ultrasonography.

Material and methods

A total of 740 pieces of chicken fillet were prepared as phantoms. No objects were implanted into 100 phantoms. We inserted glass, porcelain, plastic, wood, pencil tip, chicken bone, iron, walnut shell, and fishbone with a length of < 1 cm, 1-3 cm, and 3-5 cm into 20 pieces of chicken phantom in each size of foreign body (FB). In addition, 1-3 cm long peanut shell, < 1 cm rose spikes, < 1 cm cactus thorns, < 1 cm pellets, and < 1 cm staples were inserted into 20 pieces of chicken for each object. Each of the chicken pieces was placed inside a latex glove and examined by ultrasonography.

Results

The sensitivity of ultrasonography in the detection of the cactus thorn was 5%, whereas it ranged between 82.5 and 100% for other objects. For glass, plastic, wood, iron, and fishbone, we found that when the size exceeded 1 cm, the sensitivity increased.

Conclusions

In the evaluation of soft tissue FBs, as the size of the FBs increases, the diagnostic value of ultrasonography increases.

U.S. Army Combat Medic eFAST Performance with a Novel Versus Conventional Transducers: A Randomized, Crossover Trial

BACKGROUND

Point-of-injury extended focused assessment with sonography in trauma (eFAST) may identify life-threatening torso hemorrhage and expedite casualty evacuation. The purpose of this study was to compare combat medic eFAST performance between the novel and conventional ultrasound (US) transducers.

METHODS

We conducted a randomized crossover trial. Medic participants, previously naïve to US, were randomized to the type of transducer first utilized. The primary outcome was eFAST completion time in seconds. Secondary outcomes included diagnostic accuracy, technical adequacy, and transducer ease-of-use rating.

RESULTS

Forty medics performed 160 eFASTs. We found a statistically significant difference in eFAST completion times in favor of conventional transducers (304 vs. 358 s; P = 0.03). There was no statistically significant difference between the conventional and novel transducers in terms of diagnostic accuracy (97.7% vs. 96.0%; P = 0.25) and technical adequacy (65% vs. 72.5%; P = 0.11). Median transducer ease-of-use rating (Likert 1-5 scale) was statistically significant in favor of the conventional transducers (5 vs. 4; P = < 0.001).

CONCLUSIONS

Extended focused assessment with sonography in trauma exam times was faster with the conventional transducers. Combat medics performed diagnostically accurate eFASTs with both transducer types in a simulated aid station setting after a brief training intervention. Conventional transducers were rated higher for ease-of-use.