CT Scan Technology

CT Scan Generations

• 3rd generation CT scanners have a rotate/rotate mechanism and a wide fan beam.

Radiographic Properties

• Radiolucent: allows radiation to pass through.
• Radiopaque: blocks radiation.
• Radiodense: absorbs radiation.
• Radioparent: transparent to radiation.

CT Image Resolution

• Contrast Resolution: the ability to distinguish one soft tissue from another without regard to size and shape.
• Spatial Resolution: the ability to distinguish between two points in an image.

Hounsfield Unit

• Water has a Hounsfield unit of 0.

CT Scan History

• Godfrey Hounsfield developed a mathematical equation for reconstructing CT images.
• Johann Radon introduced tomography in 1970.
• The term "tomo" means "section" or "slice".

CT Scan Principles

• CT scan is a series of x-ray images taken from different angles and uses computer processing to create images of soft tissue in the body.
• Tomography: the process of imaging a slice of the body.

CT Scan Equipment

• Gantry Assembly: also known as a "doughnut shape equipment".
• Collimator: limits the area of the patient that intercepts the useful beam.

Old Term for CT Scan

• The old term for CT scan is Computed Axial Tomography.

CT Scan Movement

• Synchronous movement of the detector and the tube is known as rotating.
• Pitch: the relationship between the patient couch movement and x-ray beam width.

CT Scan Generators

• 3 Phase 6 pulse and 3 Phase 12 pulse generators are used in CT scan machines.

CT Scan Computer

• Microprocessors: determines the time between the end of imaging and the reconstruction time.

CT Scan Technical Factors

• Contrast: a technical factor that can be manipulated by the radiographer.
• Opening the collimation in a single detector CT increases slice thickness, dose to the patient, and scattered radiation.

Spatial Resolution

• Factors affecting spatial resolution: pixel size, slice thickness, voxel size, and detector size.

CT Scan Image Acquisition

• The slice thickness of multiple detector array CT scanners is determined by the width of the detectors in the slice thickness dimension.
• Filtered Back Projection: the process of acquiring an image during CT and storing it in computer memory, then reconstructing it.