CT For Technologist Exam Review CH1 Flashcards
Which is NOT a synonym for the preliminary (or localizer) image taken at the start of a CT examination?
A. Topogram.
B. Scout.
C. Scanogram.
D. Spiral.
D - Spiral.
The ability of a system to differentiate, on the image, objects with similar densities is known as:
A. High-contrast resolution.
B. Low-contrast resolution.
C. Spatial resolution.
D. Temporal resolution.
B - Low-contrast resolution.
Each two-dimensional square of data that make up the CT image is called a:
A. Pixel.
B. Voxel.
C. Matrix.
D. Fragment.
A - Pixel.
How many pixels are contained in a 1,024 matrix image?
A. 1,024.
B. 2,048.
C. 262,144.
D. 1,048,576.
D - 1,048,576.
1024x1024 = 1,048,576
Beam attenuation can be defined as:
The phenomenon by which an X-ray beam passing through a structure is decreased in intensity or amount because of absorption and interaction with matter.
Which of the following is a low-attenuation structure?
A. Iodine-filled aorta.
B. Rib.
C. Trachea.
D. Calcified arteries.
C - Trachea
Air-filled trachea (air is low-attenuation)!
An object is slightly less dense than water. What is the expected Hounsfield measurement?
A. -940.
B. -10.
C. 50.
D. 850.
B -10.
Why does the administration of iodinated contrast media result in an enchanced image?
Iodinated contrast material increases the ability of the enhanced structure to attenuate the X-ray beam.
The X-ray beam sources for CT produces X-ray energy that is polychromatic. This means that:
The beam comprises photons with varying energies.
An object that appears on the image but is not present in the object scanned is called a(n):
A. Artifacts.
B. Anomaly.
C. Shadow.
D. Ghost.
A - Artifacts.
Which is an advantage of filtering the X-ray beam?
A. Filtering reduces the anode heat load.
B. A filtered beam produces images with substantially less quantum mottle.
C. Filtering the beam prevents energy from being converted to heat, therefore, 100% of the energy is converted into X-rays.
D. Filtering reduces the radiation dose to the pt.
D - Filtering reduces the radiation dose to the pt.
Scan thickness is PRIMARILY important for the part it plays in:
A. Noise reduction.
B. The contrast scale.
C. Detector aperture opening.
D. Volume averaging.
D - Volume averaging.
Thinner slices = REDUCES volume averaging by decreasing the amount of pt info included in each voxel.
You are working with the radiologists to establish examination protocols for your department. Which of the following is a logical consideration when determining an appropriate slice thickness for studies of the internal auditory canal?
A. Because the auditory ossicles are quite small, a thin slice will be necessary to reduce the chance that volume averaging will obscure their appearance on the image.
B. The appropriate slice thickness will vary considerably from pt to pt. Therefore, each technologist should be free to adjust the slice thickness as he/she deems necessary for the particular pt.
C. A slice thickness of 5 to 7 mm is adequate b/c the structures of interest are not particularly small, and the examination is most often ordered as a screening study for asymptomatic pts.
D. The thickness slice available should be used to reduce the radiation dose to the corneas.
A.
How many CT numbers are assigned to each pixel in the image matrix?
A. One-half the number of all values recorded from the detector array.
B. One.
C. The number of HU per pixel is one-tenth the display field of view.
D. Two values for a 256-matrix; 4 values for a 512-matrix.
B - one.
Which is another name for raw data?
A. Image data.
B. Scan data.
C. Reconstructed data.
D. Displayed data.
B - Scan data.
