This report presents a method to embed and extract digital data in an audio file using LSB embedding technique. The intended use of this system regards for reducing noise level that is added during audio steganography process. The aim was to study the effects of sampling rate on audio cover during the process of digitization.The motivation came from our human auditory system (HAS) which is sensitive towards distortions added during steganography process and making the process suspicious. We first show how to embed the text data into audio file by LSB embedding techniques by applying cipher key. Basic audio sampling is discussed. We further segment audio by using Nyquist Shannon sampling theorem. The report concludes that our system successfully preforms audio steganography with decreased noise level in terms of Signal to Noise Ratio (SNR) when sampled at the rate proposed in Nyquist Shannon techniques.
Stereotactic radiosurgery (SRS) is a special radiotherapy technique used to irradiate intracranial lesions by 3-D arrangements of narrow photon beams eliminating the needs of invasive surgery. Three different tertiary collimators, namely BrainLab and Radionics circular cones and BrainLab micro multileaf collimator (mMLC), are used for linear accelerator-based SRS systems (X-Knife). Output factor (St), tissue maximum ratio (TMR) and off axis ratio (OAR) of these three SRS systems were measured using CC01 (Scanditronix/ Welhofer) and Pinpoint (PTW) cylindrical and Markus plane parallel ionization chambers as well as TLD and radiochromic film. Measurement results of CC01 and Pinpoint chambers were very close to each other which indicate that further reduction in volume and physical dimensions of cylindrical ionization chamber is not necessary for SRS/SRT dosimetry. Output factors of BrainLab and Radionics SRS cones were very close to each other while output factors of equivalent diameter mMLC field were different from SRS circular cones. TMR of the three SRS systems compared were very close to one another. OAR of Radionics cone and BrainLab mMLC were very close to each other, within 2%. However, OARs of BrainLab cone were found comparable to OARs of Radionics cone and BrainLab mMLC within maximum variation of 4%. In addition, user-measured similar data of other three mMLC X-Knives were compared with the mMLC X-Knife data measured in this work and found comparable. The concept of switching over to mMLC-based SRS/SRT is thus validated from dosimetric characteristics as well.
Breast cancer is the leading deadly cancer and most commonly diagnosed in women. New technologies in supplement to existing imaging modalities improve breast cancer screening. This article contributes to identify the high potential device that suggested high accuracy and reliable tool for breast screening and also to examine new screening modalities. An improved imaging system which ensures early detection, non-invasive and radiation free is expected in diagnosis. Numerous imaging modalities like positron emission tomography/computed tomography (PET/CT) imaging, ultrasound, magnetic resonance imaging (MRI), thermography, electrical impedance tomography and few others with recent developments show great potential for diagnosis. Some of the techniques aim for lesion detection and characterization with increased specificity and accuracy. In this paper, the capabilities of traditional and emerging breast imaging modalities used in breast cancer screening are summarized and their advantages and disadvantages are discussed.
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