Automated tilt compensation in acoustic microscopy.

Scanning acoustic microscopy (SAM) is a potent and nondestructive technique capable of producing three-dimensional topographic and tomographic images of specimens. This is achieved by measuring the differences in time of flight (ToF) of acoustic signals emitted from various regions of the sample. The measurement accuracy of SAM strongly depends on the ToF measurement, which is affected by tilt in either the scanning stage or the sample stage. Hence, compensating for the ToF shift resulting from sample tilt is imperative for obtaining precise topographic and tomographic profiles of the samples in a SAM. In the present work, we propose an automated tilt compensation in ToF of acoustic signal based on proposed curve fitting method. Unlike the conventional method, the proposed approach does not demand manually choosing three separate coordinate points from SAM's time domain data. The effectiveness of the proposed curve fitting method is demonstrated by compensating time shifts in ToF data of a coin due to the presence of tilt. The method is implemented for the correction of different amounts of tilt in the coin corresponding to angles 6.67°, 12.65° and 15.95°. It is observed that the present method can perform time offset correction in the time domain data of SAM with an accuracy of 45 arcsec. The experimental results confirm the effectiveness of the suggested tilt compensation technique in SAM, indicating its potential for future applications.

Minimally invasive techniques as adjuncts in low- versus high-lying retained rectal foreign bodies of autoerotic nature in young men: a tailored management algorithm with two contrasting case reports from India.

Retained rectal foreign bodies (RFBs) of an autoerotic nature represent an emerging and rare surgical emergency, posing a sensitive challenge for surgeons. RFBs exhibit a wide range of presentations and require varied management approaches, with the choice of treatment modality differing from case to case. Recently, minimally invasive techniques have been employed for the retrieval of RFBs. In 2021, the World Society of Emergency Surgery and the American Association for the Surgery of Trauma released guidelines on anorectal emergencies, highlighting the usefulness of these techniques as adjunctive tools for both diagnosis and ruling out associated complications. In this report, we describe two noteworthy cases of men who presented to the trauma emergency department with foreign bodies lodged in their rectums. We also highlight the potential role of minimally invasive techniques within a "step-up" approach for the management of retained RFBs.

Image denoising in acoustic microscopy using block-matching and 4D filter.

Scanning acoustic microscopy (SAM) is a label-free imaging technique used in biomedical imaging, non-destructive testing, and material research to visualize surface and sub-surface structures. In ultrasonic imaging, noises in images can reduce contrast, edge and texture details, and resolution, negatively impacting post-processing algorithms. To reduce the noises in the scanned image, we have employed a 4D block-matching (BM4D) filter that can be used to denoise acoustic volumetric signals. BM4D filter utilizes the transform domain filtering technique with hard thresholding and Wiener filtering stages. The proposed algorithm produces the most suitable denoised output compared to other conventional filtering methods (Gaussian filter, median filter, and Wiener filter) when applied to noisy images. The output from the BM4D-filtered images was compared to the noise level with different conventional filters. Filtered images were qualitatively analyzed using metrics such as structural similarity index matrix (SSIM) and peak signal-to-noise ratio (PSNR). The combined qualitative and quantitative analysis demonstrates that the BM4D technique is the most suitable method for denoising acoustic imaging from the SAM. The proposed block matching filter opens a new avenue in the field of acoustic or photoacoustic image denoising, particularly in scenarios with poor signal-to-noise ratios.