Physical Principles of Computed Tomography questions 2024

Physical Principles of Computed Tomography questions 2024 Data Acquisition Systematic collection of information from the patient to produce CT image, Slice by slice data acquisition(axial), x-ray tube rotates around the patient, data is collected from the single slice, the tube stops, patient moves to the next location Volume data acquisition Volume or helical scanning, x-ray tube rotates around the patient and traces a spiral path to scan an entire volume of tissue, relative transmission(attenuation measurements) values are sent to the computer and stored as raw data, large number of transmission measurements are needed to reconstruct the CT image Radiation attenuation amount of attenuation in the tissues is used to reconstruct an image, attenuation is the reduction of intensity of a beam of radiation as it passes through an object, either through absorption or scatter, depends on electrons per gram, atomic number, tissue density, and radiation energy used Homogenous beam All photons have same energy, Also called monochromatic or monoenergetic beam, Used in Houndsfield's first ct scanner because of Lambert-Beer law, Each section of absorber attenuates beam by equal amounts, Quality of beam(beam energy) does not change, Start with 80 keV, the transmitted photons all have an energy of 80keV, Takes longer to produce, Attenuation is exponential