This study aims to make the implementation of the attenuation and backscattering study to be apply for skin tissue. Attenuation and backscatter coefficients were defined in the range 22 to 48 MHz based on the L38 transducer which has a central frequency of 30 MHz and a 60% bandwidth. The attenuation coefficient was computed using local attenuation estimation algorithms (i.e., spectral difference and spectral log difference methods). Using a reference phantom technique, we compensated the recorded backscatter spectra for system-independent measurements. This study shows the experimental and theoretical steps needed to implement a quantitative study of ultrasounds images in the skin.
Radiogenic dental damage is a common and crucial problem in patients receiving radiotherapy for malignancies in the head and neck region. Unfortunately, little is known about the development of complications after radiation therapy on the microstructure profiles of the human tooth. Therefore, we propose a novel method in which the primary focus is to investigate, in vitro, the direct influences of di↵erent radiation doses on elastic properties of enamel and dentin of human tooth by Scanning Acoustic Microscopy (SAM) at the microscale. We obtain two-dimensional (2D) acoustic impedance images from twenty-five sound human third molars each of which is cut into a 1 mm thick cross-sectional slices. Acoustic impedance by SAM operating at 320 MHz are recorded from the sections comprising enamel and dentin before and after every irradiation dose to a cumulative dose of 60 Gy. The findings of our study reveal that radiation therapy changes the micro-elastic features of enamel and dentin accompanied by the decreased acoustic impedance. We establish a relationship between cumulative irradiation doses and the measured acoustic impedance. The quantified acoustic impedance values for the different irradiation doses might be helpful in in vitro assays for the determination of the safe dose limits to prevent severe tooth damage in the treatment plan of the individuals having head and neck cancer.
Lasers have the potential for reducing the required debonding force and can prevent the mechanical damage given to the enamel surface as a result of conventional debonding procedure. However, excessive thermal effects limit the use of lasers for debonding purposes. The aim of this study was to investigate the optimal parameters of 1940-nm Tm:fiber laser for debonding ceramic brackets. Pulling force and intrapulpal temperature measurements were done during laser irradiation simultaneously. A laser beam was delivered in two different modes: scanning the fiber tip on the bracket surface with a Z shape movement or direct application of the fiber tip at one point in the center of the bracket. Results showed that debonding force could be decreased significantly compared to the control samples, in which brackets were debonded by only mechanical force. Intrapulpal temperature was kept equal or under the 5.5°C threshold value of probable thermal damage to pulp. Scanning was found to have no extra contribution to the process. It was concluded that using 1940-nm Tm:fiber laser would facilitate the debonding of ceramic brackets and can be proposed as a promising debonding tool with all the advantageous aspects of fiber lasers.
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