دانلود کتاب توموگرافی ترموآکوستیک

Microwave-induced thermoacoustic tomography (TAT) is an emerging biomedical imaging modality that combines the high contrast and dielectric-based specificity of microwave imaging with the high spatial resolution of ultrasound imaging in a single modality. By listening to microwave, TAT detects tissue-absorbed microwave ultrasonically through the photo- or thermoacoustic effect. Since ultrasonic scattering is several orders of magnitude weaker than microwave scattering in tissue, TAT breaks the millimeters-scale spatial resolution limit associated with pure microwave imaging approaches for deep tissue imaging. In TAT, tissue is excited with a short (typically micro- or nanosecond levels) microwave pulse and the subsequent microwave- induced transient thermoacoustic waves in the range of kHz to MHz, due to the transient thermoelastic expansion of microwave-absorbing components in tissue, are detected by wideband unfocused or focused ultrasound transducer(s). Unique advantages of TAT are that functional parameters such as water content and ion concentration, and mechanical properties such as elasticity along with vasculature and blood volume can be imaged in high resolution. In addition, highly specific molecular TAT can be realized through the use of molecular contrast agents. Finally, TAT can be made portable for bedside applications, is economical, and uses non-ionization radiation. TAT has found its potential clinical applications in several areas. In breast imaging, TAT offers submillimeter-resolution ability to quantitatively image the high microwave contrast generated through the presence of blood, water and lipid, which are the predominate transformations associated with malignancy. Application of TAT to joint imaging has been recently explored, offering an opportunity for early detection and monitoring of progressive diseases including osteoarthritis and rheumatoid arthritis. In this case, the microwave contrast is produced through the degraded articular cartilage, and the increased water content in the synovial cavity. Other clinical applications of TAT also start to appear, including vascular, liver and thyroid imaging.