Computed Tomography Course Quiz

Computed Tomography (CT) Equipment Techniques

• CT is an imaging procedure using special X-ray equipment to create detailed pictures (scans) of areas inside the body
• Also known as computerized tomography or computerized axial tomography (CAT)
• Tomography originates from Greek words tomos (a cut, slice, or section) and graphein (to write or record)
• CT is a non-invasive procedure creating cross-sectional images of the body
• Each cross-section is like a slice of bread
• These images are used for a variety of diagnostic and therapeutic applications

Limitations of Film-Based Radiography

• A major challenge of radiography is the overlapping of all structures on the film
• This makes distinguishing small details difficult, sometimes impossible, especially when structures have similar densities
• This is frequently the case with tumors and surrounding tissues

Second Limitation of Radiography

• Radiography is a qualitative process. This makes it hard to tell the difference between a uniform object with an uneven thickness, and a non-uniform object with a uniform thickness.

• It's difficult to differentiate an object with the same thickness but a different composition from an object with different thicknesses, but the same composition

Limitations of Conventional Tomography

• The overlapping issue in radiography can be somewhat improved using conventional tomography, sometimes referred to geometric tomography.
• This method involves moving the X-ray tube and film simultaneously in opposite directions.
• The goal is to blur out structures above and below the intended section.
• The limitations of tomography include persistent image blur that cannot be fully eliminated
• It's hard to completely eliminate unwanted overlapping structures
• Contrast is degraded by scattered radiation from the X-ray beam open geometry
• Problems are caused by different film screen combinations

CT Differences from Conventional Radiography

• CT generates cross-sectional images removing overlapping structures
• CT's sensitivity to subtle differences in X-ray attenuation is at least 10 times greater than traditional screen-film systems
• This is primarily due to virtual elimination of scatter

Purpose of CT Scans

• CT scans provide detailed cross-sectional images of internal structures (organs, blood vessels, bones, soft tissue etc.)
• Used for diagnostic purposes
• Used to guide treatment, further tests, surgeries (biopsies, radiation therapy)
• Used for detecting and monitoring conditions (such as cancer, heart disease, lung nodules, liver masses)

CT Scan Technique

• Uses digital geometry processing to generate 3D images from a large series of 2D X-ray images taken around a single axis of rotation.

• A flat patient couch is positioned in a circular opening

• The patient is positioned and the table in the gantry can be moved up, down, backwards, or forwards

• The X-ray tube rotates around the patient

• As the X-rays pass through the patient to the detectors, a computer system performs calculations

• This results in a viewable image

• One cross-sectional slice of the body is obtained for each complete rotation

• Multiple shots (profiles), around 1,000, are acquired during each rotation

• A two-dimensional image is compiled from the profiles