Image acquisition stability of fixated musculoskeletal sonography in an exercise setting: a quantitative analysis and comparison with freehand acquisition.

PURPOSE: In dynamic musculoskeletal sonography, probe fixation can contribute to field of view (FOV) consistency, which is necessary for valid analysis of architectural parameters. In this volunteer study, the achieved FOV consistency in fixated ultrasonography was quantified and compared with freehand acquisition. METHODS: During five resting periods during cycling exercise, longitudinal B-mode images of the vastus lateralis (VL) muscle were acquired on one thigh with a fixated probe, and by two trained observers on the other thigh. In each acquisition, the structural similarity compared to the first resting period was determined using the complex wavelet structural similarity index (CW-SSIM). Also, the pennation angle of the VL was measured. Both CW-SSIM and pennation angle were compared between fixated and freehand acquisition. Furthermore, the compression of tissue by the probe fixation was measured. RESULTS: In fixated acquisition, a significantly higher structural similarity (p < 0.05) and an improved repeatability of pennation angle measurement were obtained compared to freehand acquisition. Probe fixation compressed muscle tissue by 12% on average. CONCLUSIONS: Quantification of the structural similarity showed an increase in FOV consistency with sonography compared to freehand acquisition. The demonstrated feasibility of long-term fixated acquisition might be attractive in many medical fields and sports, and for reduction of work-related ergonomic problems among sonographers.

Investigation on the Effect of Spatial Compounding on Photoacoustic Images of Carotid Plaques in the In Vivo Available Rotational Range.

Photoacoustic imaging (PAI) is a promising imaging modality due to its high optical specificity. However, the low signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of in vivo PA images are major challenges that prevent PAI from finding its place in clinics. This paper investigates the merit of spatial compounding of PA images in arterial phantoms and the achievable improvements of SNR, when in vivo conditions are mimicked. The analysis of the compounding technique was performed on a polyvinyl alcohol vessel phantom with black threads embedded in its wall. The in vivo conditions were mimicked by limiting the rotation range in ±30°, adding turbid surrounding medium, and filling the lumen with porcine blood. Finally, the performance of the technique was evaluated in ex vivo human carotid plaque samples. Results showed that spatial compounding elevates the SNR by 5-10 dB and CNR by 1-5 dB, depending on the location of the absorbers. This paper elucidates prospective in vivo PA characterization of carotid plaques by proposing a method to enhance PA image quality.

Visualization of vasculature using a hand-held photoacoustic probe: phantom and in vivo validation.

Assessment of microvasculature and tissue perfusion can provide diagnostic information on local or systemic diseases. Photoacoustic (PA) imaging has strong clinical potential because of its sensitivity to hemoglobin. We used a hand-held PA probe with integrated diode lasers and examined its feasibility and validity in the detection of increasing blood volume and (sub) dermal vascularization. Blood volume detection was tested in custom-made perfusion phantoms. Results showed that an increase of blood volume in a physiological range of 1.3% to 5.4% could be detected. The results were validated with power Doppler sonography. Using a motorized scanning setup, areas of the skin were imaged at relatively short scanning times ( < 10 ?? s / cm 2 ) with PA. Three-dimensional visualization of these structures was achieved by combining the consecutively acquired cross-sectional images. Images revealed the epidermis and submillimeter vasculature up to depth of 5 mm. The geometries of imaged vasculature were validated with segmentation of the vasculature in high-frequency ultrasound imaging. This study proves the feasibility of PA imaging in its current implementation for the detection of perfusion-related parameters in skin and subdermal tissue and underlines its potential as a diagnostic tool in vascular or dermal pathologies.