CT Basics Quiz

CT Basics

• CT eliminates superimposed structures.
• Differentiates small density differences in anatomy.
• Provides high-quality images.
• CT images are cross-sectional.
• Z-axis represents thickness, X-axis (width) is right/left, and Y-axis (height) is anterior/posterior.
• A pixel is a picture element, and a voxel is a 3D data volume element.
• Positioning for a scout involves setting the couch zero point and start location.
• Scout production sets up tubes and detectors for the desired projection.
• ODM setup (Z-axis) uses a maximum of one per group, indicated on kV/mA.
• Scan Field of View (SFOV) determines the amount of scanned anatomy, typically exceeding anatomy dimensions (50cm).
• Display Field of View (DFOV) determines image size and can be equal to or less than SFOV.
• Adjusting DFOV affects resolution.
• Noise Index (NI) represents a tradeoff between image quality and patient dose, NI=(Noise/mA)×Dose.
• Corresponds to noise level in reconstructed images.

Image Reconstruction Key Terms

• Fourier transform helps study waves and solve linear differential equations for image analysis, and to compile image construction.
• Filtered back projection is method for image construction that compiles attenuation profiles.
• Interpolation estimates missing data values in raw data scans using surrounding data measurements.
• Raw data represents scan measurements from the detector; it's not useful until processed.
• Image data, generated from processing raw data, uses assigned Hounsfield unit (HU) values based on average tissue density to represent different gray shades based on CT numbers.

CT Numbers

• Bone has a CT number of 1000 (white).
• Muscles (50), White matter (45), Gray matter (40) and Blood (20) have lower CT numbers.
• Cerebrospinal fluid (CSF) is 15.
• Water is 0.
• Fat is -100.
• Lungs are -200.
• Air is -1000 (black).
• Window level determines the central CT number and Window width determines the range of CT numbers displayed.

CT Scanner Generations

• First generation CT scanners used pencil beam and single/two detectors, taking 5 minutes to image the head (only).
• Second generation employed fan-shaped beams and a linear array of detectors for faster imaging compared to the first design, still using translation-rotation motion.
• Third generation used a continuous rotating fan beam and a curvilinear array of detectors for even faster imaging.
• Fourth generation used a stationary ring of detectors that surround the patient; and rotate, decreasing imaging time while maintaining a fan beam.
• Fifth generation (Electron beam CT) involves an electron gun that produces a beam of electrons interacting with a massive anode target which scans the patient in a semicircle. This is faster but less resolution.
• Sixth generation is Dual source CT which has improved volume coverage and resolution
• Seventh generation is Flat-panel CT which uses digital detectors and has great spatial resolution but lacks contrast resolution

Test your knowledge on the fundamentals of CT imaging. This quiz covers topics such as image quality, positioning for a scout, and understanding the key components and terminology related to computed tomography. Perfect for students and professionals looking to refresh their knowledge in radiology.