26 Questions
What is the equivalent number of chest x-rays with a CT Abdomen or Pelvis scan?
500
Which organ receives the highest radiation dose during a Pelvis CT scan?
Uterus
What is the induction of erythema typically caused by in terms of Gy?
2 Gy
How does modern CT scanners modulate the mA during the scan?
Increasing mA for thicker tissue penetration
What is the typical range of patient skin doses in CT scans?
20 to 40 mGy
If the mAs is reduced to half with no other changes, what effect does this have?
Allows for longer helical scans
What aspect of tissue influences Compton scatter and plays a dominant role in forming contrast in medical CT?
Linear attenuation coefficient
How many shades are utilized in the gray-scale of CT image voxels?
4096
What technological advancement led to helical (spiral) acquisition in CT imaging?
Slip-ring technology
In helical CT scanning, what does the pitch parameter indicate?
Table increment per rotation and beam collimation
Which detector is commonly used in modern CT systems?
Solid-state scintillator detectors
How does a narrower window width affect the contrast of a CT image?
Increases contrast
What does the slice sensitivity profile describe in single slice CT?
Extent of details contributing to the signal
How does helical data set interpolation compensate for differences in CT reconstruction algorithms?
Interpolates into planar images
What does the choice of CT reconstruction kernel or algorithm chosen by the operator affect?
Spatial resolution and image quality
What is the role of CT numbers in determining the amount of calcification in pulmonary nodules?
Determining the mean CT number of the nodule
Which aspect of radiation dose in CT is unique compared to chest radiography?
High SNR required for high contrast resolution
What is the principal interaction mechanism in CT that contributes to a considerable radiation dose from scattered radiation?
Compton scattering
What does the Multiple Scan Average Dose (MSAD) in CT measure?
Average dose resulting from a large series of CT slices
How is the Computed Tomography Dose Index (CTDI) measured?
Using a pencil-type ionization chamber in phantoms simulating heads and bodies
Which factor influences the Collimator Pitch CTDIvol in CT imaging?
Collimation mm
What is the impact of increasing pitch while holding other factors constant in CT scanning?
Decreases patient dose
In which body scans are CTDI values typically lower and why?
Body scans, due to greater x-ray attenuation
What parameter increases with tube voltage in CT imaging?
Image contrast
What does decreasing kVp do to dose in CT imaging with other factors constant?
Reduces dose
What is an effective way to reduce patient radiation dose in pediatric patients during CT scans?
Develop mA settings based on patient weight or diameter
This quiz explores the unique aspects of radiation dose in CT imaging compared to x-ray projection imaging. Topics include the highly collimated manner of obtaining single CT images, even distribution of dose due to rotational acquisition, and the higher dose to slice volume for achieving high contrast resolution.
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