High-frequency ultrasound imaging of the skin during normal and hypertensive pregnancies

Linear sound attenuation model for assessing external stimuli in prenatal period

The popularization of acoustic stimulation during the prenatal period encourages the analysis of sounds reaching the inside of the uterus. To assess the distortion of any sound stimuli, a mathematical model of attenuation has to be used. In this paper a mathematical model is proposed on the basis of data from a physical model. The physical model consisted of muscle slices of two different thicknesses placed in a tank filled with water. The amplitudes of sinusoidal waves between 160 and 2000 Hz were measured under the water surface. Using the collected data, a linear mathematical model of sound attenuation on the way to the fetal ear was created. The results indicated a rise in the amount of sound attenuation for increasing frequencies. Analysis of slope coefficients for two muscle thicknesses revealed that there is no significant difference between attenuation by the thinner and the thicker tissue. Finally, the model was verified with data obtained during experiments on animals. The proposed model of the sound transmission allowed assessment of the attenuation by a soft tissue. It reveals changes in the sound reaching fetal ears, which can make acoustic stimulation different than what is heard in postnatal life. The model can be used to simulate the distortion of any sound which is proposed to prenatal stimulation and to assess its quality.

Non-invasive assessment of negative pressure wound therapy using high frequency diagnostic ultrasound: oedema reduction and new tissue accumulation

Tissue oedema plays an important role in the pathology of chronic and traumatic wounds. Negative pressure wound therapy (NPWT) is thought to contribute to active oedema reduction, yet few studies have showed this effect. In this study, high frequency diagnostic ultrasound at 20 MHz with an axial resolution of 60 µm was used to assess the effect of NPWT at - 80 mmHg on pressure ulcers and the surrounding tissue. Wounds were monitored in four patients over a 3-month period during which changes in oedema and wound bed thickness (granulation tissue) were measured non-invasively. The results showed a rapid reduction of periwound tissue oedema in all patients with levels falling by a mean of 43% after 4 days of therapy. A 20% increase in the thickness of the wound bed was observed after 7 days due to new granulation tissue formation. Ultrasound scans through the in situ gauze NPWT filler also revealed the existence of macrodeformation in the tissue produced by the negative pressure. These preliminary studies suggest that non-invasive assessment using high frequency diagnostic ultrasound could be a valuable tool in clinical studies of NPWT.

Quantitative assessments of burn degree by high-frequency ultrasonic backscattering and statistical model

An accurate and quantitative modality to assess the burn degree is crucial for determining further treatments to be properly applied to burn injury patients. Ultrasounds with frequencies higher than 20 MHz have been applied to dermatological diagnosis due to its high resolution and noninvasive capability. Yet, it is still lacking a substantial means to sensitively correlate the burn degree and ultrasonic measurements quantitatively. Thus, a 50 MHz ultrasound system was developed and implemented to measure ultrasonic signals backscattered from the burned skin tissues. Various burn degrees were achieved by placing a 100 °C brass plate onto the dorsal skins of anesthetized rats for various durations ranged from 5 to 20 s. The burn degrees were correlated with ultrasonic parameters, including integrated backscatter (IB) and Nakagami parameter (m) calculated from ultrasonic signals acquired from the burned tissues of a 5 × 1.4 mm (width × depth) area. Results demonstrated that both IB and m decreased exponentially with the increase of burn degree. Specifically, an IB of -79.0 ± 2.4 (mean ± standard deviation) dB for normal skin tissues tended to decrease to -94.0 ± 1.3 dB for those burned for 20 s, while the corresponding Nakagami parameters tended to decrease from 0.76 ± 0.08 to 0.45 ± 0.04. The variation of both IB and m was partially associated with the change of properties of collagen fibers from the burned tissues verified by samples of tissue histological sections. Particularly, the m parameter may be more sensitive to differentiate burned skin due to the fact that it has a greater rate of change with respect to different burn durations. These ultrasonic parameters in conjunction with high-frequency B-mode and Nakagami images could have the potential to assess the burn degree quantitatively.

Studying plasticity of sensory function: insight from pregnancy

Plasticity of sensory function has become an object of study because of its proposed role in the recovery of function after central nervous system damage. Normal pregnancy may provide a useful in vivo model to study the effects of progressive reduction in the abdominal skin receptor density. As such changes are confined to abdominal skin, other parts of the body are only moderately affected by pregnancy and therefore can provide a control for other changes during pregnancy. The two-point discrimination test (TPDT) of the skin is a simple test of the sensory function. We conducted the TPDT in a pregnant population longitudinally studied at different pregnancy stages and in different skin regions. In this pregnant population, we found a reduction in sensory sensibility that was not skin region specific. In particular, the increase in abdominal circumference did not produce different effects of TPDT on the belly compared to the dorsum or the hand. This suggests that the sensory system is able to compensate for the reduction in peripheral information flow through central nervous system plasticity.

Has packing sinus wounds become a ritualistic practice?

Wound healing is both a science and an art, and modern advances in wound management are ensuring that advanced clinicians use both clinical knowledge and experience when deciding on wound dressings and therapies. When there is a lack of evidence, then selection of dressings or therapies becomes extremely difficult and inappropriate treatment can occur. This is generally the situation with sinus wounds. There is very little evidence available to help decide on suitable dressings for these intractable wounds. The use of high frequency ultrasound (HFU) can help to guide practice on whether or not to pack sinus wounds. This article will explore the potential of ultrasound use by describing a case study of a patient with a sinus wound where HFU was used to examine the sinus and inform the practitioners on the appropriate choice of wound dressing.

Wound healing assessment using 20 MHz ultrasound and photography

BACKGROUND/AIMS

To compare two non-invasive techniques of assessing wound healing, photography and high resolution ultrasound (HRUS) scanning, in experimentally induced full-thickness human skin wounds.

METHODS

Punch biopsy wounds, 4 mm in diameter, were made aseptically through locally anaesthetised skin on the anterior (volar) surface of the non-dominant forearm, 3 cm below the base of the cubital fossa, of 20 human participants. The wounds were treated with a topical antibiotic and covered for 3 days with Mepore sterile dressings. Wound healing was assessed on post-operative days 3, 7, 14 and 21 from photographs and HRUS B-scans. All photographs were taken of the wound site and adjacent intact skin under standardised conditions. The prints obtained were examined visually and digitised. Digital HRUS B-scans were taken through the centre of the wound bed and the adjacent intact skin parallel to the epidermis. Using the scanner's calibrated linear measurement capability, the wound width was measured adjacent to the deep surface of the scab, at the base of the wound, and midway between these two levels.

RESULTS

The wound margins were more clearly defined in the HRUS scans than in the photographs of the wounds; in some of the latter the scab masked the wound margins. Changes in the surface width of the wound were affected by the time of scab dehiscence, which varied between volunteers. There was less individual variation in the width of the base of the wound, as measured from the HRUS scans.

CONCLUSIONS

In contrast to photography, which allows recording of changes in the superficial aspect of the wound only, HRUS scanning permits the quantitative assessment of structural changes deep within the wound. Temporal changes in the width of the base of the wound can be used as an indication of the progress of repair.