Unfolding displacement measurement method for the aliasing interferometer signal of a wavelength-comb-swept laser.

We demonstrate an unfolding displacement measurement method to overcome the aliasing problem of wavelength-comb-swept laser (WCSL). Compared to the conventional wavelength-swept laser (WSL), the WCSL exhibits an extended coherence length, owing to the narrowing spectral linewidth of the etalon filter. However, the aliasing interference signal induces an unexpected back-bounced phenomenon during displacement measurement because of the discretely distributed comb-like periodic spectra of the etalon filter. By using the dual-reference interferometry method, the back-bounced displacement measurement can be successfully unfolded to extend the measurement range by two times. In addition, we demonstrate a longer-range surface profiling image over 18 mm within the 200 mm of measurement range using a line-field beam of a parallel-swept source-optical coherence tomography system.

Acousto-Optic-Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements.

We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic-based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R² = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain.

Determination of injection site in flexor digitorum longus for effective and safe botulinum toxin injection.

OBJECTIVE: To determine the optimal injection site in the flexor digitorum longus (FDL) muscle for effective botulinum toxin injection. METHODS: Fourteen specimens from eight adult Korean cadavers were used in this study. The most proximal medial point of the tibia plateau was defined as the proximal reference point; the most distal tip of the medial malleolus was defined as the distal reference point. The distance of a line connecting the proximal and distal reference points was defined as the reference length. The X-coordinate was the distance from the proximal reference point to the intramuscular motor endpoint (IME), or motor entry point (MEP) on the reference line, and the Y-coordinate was the distance from the nearest point from MEP on the medial border of the tibia to the MEP. IME and MEP distances from the proximal reference point were evaluated using the raw value and the X-coordinate to reference length ratio was determined as a percentage. RESULTS: The majority of IMEs were located within 30%-60% of the reference length from the proximal reference point. The majority of the MEPs were located within 40%-60% of the reference length from the proximal reference point. CONCLUSION: We recommend the anatomical site for a botulinum toxin injection in the FDL to be within a region 30%-60% of the reference length from the proximal reference point.

Determination of an ideal stimulation site of the medial antebrachial cutaneous nerve using ultrasound and investigation of the efficiency.

OBJECTIVE: To determine an ideal stimulation site of the medial antebrachial cutaneous nerve (MACN) using ultrasound measurement and to compare the efficiency of the new stimulation site with the conventional stimulation site on the nerve conduction study. METHODS: Both arms of 15 healthy participants were measured using ultrasound. The MACN was identified in the transverse view at each 0, 2, 4, 6, and 8 cm proximal sites from the medial epicondyle, and the distances to the median nerve and to the skin from the MACN were measured. The ideal stimulation site should be located at the level which can give the shortest distance from the skin and the longest distance from the median nerve in terms of volume conduction. To confirm the efficiency of the ideal site, we measured the amplitude of the MACN conduction study at the ideal site against one at the 4 cm proximal to the medial epicondyle (conventional site). RESULTS: The ultrasound showed the ideal stimulation site for the MACN could be the elbow crease line. However, the nerve conduction study revealed that the amplitudes of the MACN were significantly larger at the 4 cm proximal to the medial epicondyle compared with ones at the ideal site. CONCLUSION: The ideal stimulation site based on the ultrasound did not permit better stimulation site for the nerve conduction study of the MACN compared with the conventional site. Careful adjustment of the stimulation site on the basis of this study would contribute to an accurate conduction study of the MACN.