Computed Tomography Final Exam

define computed tomography (CT) -the process of creating a cross-sectional tomographic plane of any part of the body -rotates -detector assembly -algorithm; matrix -liquid crystal display (LCD) or cathode ray tube (CRT) -Basic scanning steps: -The xray tube _______ around the patient or part -A ______ measures the remnant radiation exiting the patient and feeds data to a computer -The computer compiles and calculates the data according to a preselected _______ and assembles it into a ________ -The image is displayed on a _______ or _______ gantry computer and operator console patient table -three major components of a ct scanner detector assembly -electronic component of scanner that measures remnant radiation exiting the patient and converts it to a proportional analog signal matrix -array of numbers arranged in a grid; comprises the digital image hounsfield unit -number used to describe average density of tissue data acquisition system (DAS) -part of detector assembly that converts analog signals to digital signals that can be used by the CT computer Field of View (FOV) -area of anatomy displayed by the monitor voxel -volume element; determined by slice thickness window level -determines the midpoint of the range of gray levels displayed gantry -part of scanner that houses the xray tube, cooling system, detector assembly, and DAS window width -the range of CT numbers used to map signals into shades of gray pixel -one individual cell surface within an image matrix used for CRT image display; picture element multiplanar reconstruction -a digital postprocessing technique that has the ability to reconstruct CT axial images into other planes without additional radiation to the patient head chest abdomen -three most commonly requested CT procedures intravenously orally rectally -three routes used to introduce contrast for CT procedures faster scans require faster contrast delivery -why are power injectors needed for CT contrast procedures? -spatial resolution -contrast resolution -quantum noise -artifacts -four ma image quality spatial resolution -the amount of blurring in a CT image is described as contrast resolution -the ability to differentiate between small differences in density within the image is termed quantum noise -the most common cause of noise in a CT image arises from the random variation in photon detection, or to reduce chance of residual barium in GI tract causing artifact on CT -why would it be best to schedule CT scan of the abdomen on a patient several days after the patient's GI fluoro procedure? slice thickness scan time scan diameter patient instructions -four image quality factors that are under the technologist's control spatial resolution -FOV affects what image quality factor noise spatial resolution -matrix size affects what image quality factor spatial resolution contrast resolution noise -slice thickness affects what image quality factor artifacts -dental filling affect what image quality factor noise contrast resolution -xray beam energy affects what image quality factor spatial resollution -focal spot size affects what image quality factor artifacts -residual barium affects what image quality factor spatial resolution contrast resolution noise -reconstruction algorithm affects what image quality factor